# sudoers - default sudo security policy plugin - man(5) - [phpMan] [_SUDOERS_(5)](https://www.chedong.com/phpMan.php/man/SUDOERS/5/markdown) File Formats Manual [_SUDOERS_(5)](https://www.chedong.com/phpMan.php/man/SUDOERS/5/markdown) ## NAME sudoers — default sudo security policy plugin ## DESCRIPTION The **sudoers **policy plugin determines a user's **sudo **privileges. It is the default **sudo **policy plugin. The policy is driven by the _/etc/sudoers_ file or, optionally, in LDAP. The policy format is described in detail in the “SUDOERS FILE FORMAT” section. For information on stor‐ ing **sudoers **policy information in LDAP, see [_sudoers.ldap_(5)](https://www.chedong.com/phpMan.php/man/sudoers.ldap/5/markdown). ### Configuring sudo.conf for sudoers **sudo **consults the [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) file to determine which plugins to load. If no [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) file is present, or if it contains no _Plugin_ lines, **sudoers **will be used for auditing, policy decisions and I/O logging. To explicitly configure [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) to use the **sudoers **plugin, the following configuration can be used. Plugin sudoers_audit sudoers.so Plugin sudoers_policy sudoers.so Plugin sudoers_io sudoers.so Starting with **sudo **1.8.5, it is possible to specify optional arguments to the **sudoers **plugin in the [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) file. Plugin arguments, if any, should be listed after the path to the plugin (i.e., after _sudoers.so_). The arguments are only effective for the plugin that opens (and parses) the _sudoers_ file. For **sudo **version 1.9.1 and higher, this is the _sudoers_audit_ plugin. For older versions, it is the _sudoers_policy_ plugin. Multiple arguments may be specified, separated by white space. For example: Plugin sudoers_audit sudoers.so sudoers_mode=0400 error_recovery=false The following plugin arguments are supported: error_recovery=bool The _error_recovery_ argument can be used to control whether **sudoers **should attempt to recover from syntax errors in the _sudoers_ file. If set to _true_ (the default), **sudoers** will try to recover from a syntax error by discarding the portion of the line that con‐ tains the error until the end of the line. A value of _false_ will disable error recov‐ ery. Prior to version 1.9.3, no error recovery was performed. ignore_perms=bool The _ignore_perms_ argument can be used to disable security checks when loading the _sudoers_ file. If enabled, the _sudoers_ file will be loaded regardless of the owner or file mode. This argument is intended to be used for testing purposes and should not be enabled on production systems. ldap_conf=pathname The _ldap_conf_ argument can be used to override the default path to the _ldap.conf_ file. ldap_secret=pathname The _ldap_secret_ argument can be used to override the default path to the _ldap.secret_ file. sudoers_file=pathname The _sudoers_file_ argument can be used to override the default path to the _sudoers_ file. sudoers_uid=user-ID The _sudoers_uid_ argument can be used to override the default owner of the sudoers file. It should be specified as a numeric user-ID. sudoers_gid=group-ID The _sudoers_gid_ argument can be used to override the default group of the sudoers file. It must be specified as a numeric group-ID (not a group name). sudoers_mode=mode The _sudoers_mode_ argument can be used to override the default file mode for the sudoers file. It should be specified as an octal value. For more information on configuring [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown), refer to its manual. ### User Authentication The **sudoers **security policy requires that most users authenticate themselves before they can use **sudo**. A password is not required if the invoking user is **root**, if the target user is the same as the invoking user, or if the policy has disabled authentication for the user or com‐ mand. Unlike [_su_(1)](https://www.chedong.com/phpMan.php/man/su/1/markdown), when **sudoers **requires authentication, it validates the invoking user's credentials, not the target user's (or **root**'s) credentials. This can be changed via the _rootpw_, _targetpw_ and _runaspw_ flags, described later. If a user who is not listed in the policy tries to run a command via **sudo**, mail is sent to the proper authorities. The address used for such mail is configurable via the _mailto_ De‐ faults entry (described later) and defaults to _root_. No mail will be sent if an unauthorized user tries to run **sudo **with the **-l **or **-v **option un‐ less there is an authentication error and either the _mail_always_ or _mail_badpass_ flags are enabled. This allows users to determine for themselves whether or not they are allowed to use **sudo**. By default, all attempts to run **sudo **(successful or not) are logged, regardless of whether or not mail is sent. If **sudo **is run by **root **and the SUDO_USER environment variable is set, the **sudoers **policy will use this value to determine who the actual user is. This can be used by a user to log com‐ mands through sudo even when a **root **shell has been invoked. It also allows the **-e **option to remain useful even when invoked via a sudo-run script or program. Note, however, that the _sudoers_ file lookup is still done for **root**, not the user specified by SUDO_USER. **sudoers **uses per-user time stamp files for credential caching. Once a user has been authen‐ ticated, a record is written containing the user-ID that was used to authenticate, the termi‐ nal session ID, the start time of the session leader (or parent process) and a time stamp (using a monotonic clock if one is available). The user may then use **sudo **without a password for a short period of time (15 minutes unless overridden by the _timestamp_timeout_ option). By default, **sudoers **uses a separate record for each terminal, which means that a user's login sessions are authenticated separately. The _timestamp_type_ option can be used to select the type of time stamp record **sudoers **will use. ### Logging By default, **sudoers **logs both successful and unsuccessful attempts (as well as errors). The _log_allowed_ and _log_denied_ flags can be used to control this behavior. Messages can be logged to [_syslog_(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown), a log file, or both. The default is to log to [_syslog_(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown) but this is configurable via the _syslog_ and _logfile_ settings. See “EVENT LOGGING” for a description of the log file format. **sudoers **is also capable of running a command in a pseudo-terminal and logging input and/or output. The standard input, standard output, and standard error can be logged even when not associated with a terminal. For more information about I/O logging, see the “I/O LOGGING” section. Starting with version 1.9, the _log_servers_ setting may be used to send event and I/O log data to a remote server running **sudo_logsrvd **or another service that implements the protocol de‐ scribed by [_sudo_logsrv.proto_(5)](https://www.chedong.com/phpMan.php/man/sudologsrv.proto/5/markdown). ### Command environment Since environment variables can influence program behavior, **sudoers **provides a means to re‐ strict which variables from the user's environment are inherited by the command to be run. There are two distinct ways **sudoers **can deal with environment variables. By default, the _env_reset_ flag is enabled. This causes commands to be executed with a new, minimal environment. On AIX (and Linux systems without PAM), the environment is initialized with the contents of the _/etc/environment_ file. The HOME, MAIL, SHELL, LOGNAME and USER en‐ vironment variables are initialized based on the target user and the SUDO_* variables are set based on the invoking user. Additional variables, such as DISPLAY, PATH and TERM, are pre‐ served from the invoking user's environment if permitted by the _env_check_, or _env_keep_ op‐ tions. A few environment variables are treated specially. If the PATH and TERM variables are not preserved from the user's environment, they will be set to default values. The LOGNAME and USER are handled as a single entity. If one of them is preserved (or removed) from the user's environment, the other will be as well. If LOGNAME and USER are to be pre‐ served but only one of them is present in the user's environment, the other will be set to the same value. This avoids an inconsistent environment where one of the variables describ‐ ing the user name is set to the invoking user and one is set to the target user. Environment variables with a value beginning with ‘()’ are removed unless both the name and value parts are matched by _env_keep_ or _env_check_, as they may be interpreted as functions by the **bash** shell. Prior to version 1.8.11, such variables were always removed. If, however, the _env_reset_ flag is disabled, any variables not explicitly denied by the _env_check_ and _env_delete_ options are allowed and their values are inherited from the invoking process. Prior to version 1.8.21, environment variables with a value beginning with ‘()’ were always removed. Beginning with version 1.8.21, a pattern in _env_delete_ is used to match **bash **shell functions instead. Since it is not possible to block all potentially dangerous environment variables, use of the default _env_reset_ behavior is encouraged. Environment variables specified by _env_check_, _env_delete_, or _env_keep_ may include one or more ‘*’ characters which will match zero or more characters. No other wildcard characters are supported. By default, environment variables are matched by name. However, if the pattern includes an equal sign (‘=’), both the variables name and value must match. For example, a **bash **shell function could be matched as follows: env_keep += "BASH_FUNC_my_func%%=()*" Without the ‘=()*’ suffix, this would not match, as **bash **shell functions are not preserved by default. The complete list of environment variables that are preserved or removed, as modified by global Defaults parameters in _sudoers_, is displayed when **sudo **is run by **root **with the **-V **op‐ tion. The list of environment variables to remove varies based on the operating system **sudo** is running on. Other settings may influence the command environment: **• sudoers **options such as _always_set_home_, _secure_path_, _set_logname_, _set_home_, and _setenv_. **• **Command tags, such as SETENV and NOSETENV. Note that SETENV is implied if the command matched is **ALL**. **• sudo **options, such as **-E **and **-i**. On systems that support PAM where the **pam_env **module is enabled for **sudo**, variables in the PAM environment may be merged in to the environment. If a variable in the PAM environment is already present in the user's environment, the value will only be overridden if the variable was not preserved by **sudoers**. When _env_reset_ is enabled, variables preserved from the invok‐ ing user's environment by the _env_keep_ list take precedence over those in the PAM environ‐ ment. When _env_reset_ is disabled, variables present the invoking user's environment take precedence over those in the PAM environment unless they match a pattern in the _env_delete_ list. The dynamic linker on most operating systems will remove variables that can control dynamic linking from the environment of set-user-ID executables, including **sudo**. Depending on the operating system this may include _RLD*, DYLD_*, LD_*, LDR_*, LIBPATH, SHLIB_PATH, and oth‐ ers. These type of variables are removed from the environment before **sudo **even begins execu‐ tion and, as such, it is not possible for **sudo **to preserve them. As a special case, if the **-i **option (initial login) is specified, **sudoers **will initialize the environment regardless of the value of _env_reset_. The DISPLAY, PATH and TERM variables re‐ main unchanged; HOME, MAIL, SHELL, USER, and LOGNAME are set based on the target user. On AIX (and Linux systems without PAM), the contents of _/etc/environment_ are also included. All other environment variables are removed unless permitted by _env_keep_ or _env_check_, described above. Finally, the _restricted_env_file_ and _env_file_ files are applied, if present. The variables in _restricted_env_file_ are applied first and are subject to the same restrictions as the in‐ voking user's environment, as detailed above. The variables in _env_file_ are applied last and are not subject to these restrictions. In both cases, variables present in the files will only be set to their specified values if they would not conflict with an existing environment variable. ## SUDOERS FILE FORMAT The _sudoers_ file is composed of two types of entries: aliases (basically variables) and user specifications (which specify who may run what). When multiple entries match for a user, they are applied in order. Where there are multiple matches, the last match is used (which is not necessarily the most specific match). The _sudoers_ file grammar will be described below in Extended Backus-Naur Form (EBNF). Don't despair if you are unfamiliar with EBNF; it is fairly simple, and the definitions below are annotated. ### Resource limits By default, **sudoers **uses the operating system's native method of setting resource limits for the target user. On Linux systems, resource limits are usually set by the _pam_limits.so_ PAM module. On some BSD systems, the _/etc/login.conf_ file specifies resource limits for the user. On AIX systems, resource limits are configured in the _/etc/security/limits_ file. If there is no system mechanism to set per-user resource limits, the command will run with the same limits as the invoking user. The one exception to this is the core dump file size, which is set by **sudoers **to 0 by default. Disabling core dumps by default makes it possible to avoid potential security problems where the core file is treated as trusted input. Resource limits may also be set in the _sudoers_ file itself, in which case they override those set by the system. See the _rlimit_as,_ _rlimit_core,_ _rlimit_cpu,_ _rlimit_data,_ _rlimit_fsize,_ _rlimit_locks,_ _rlimit_memlock,_ _rlimit_nofile,_ _rlimit_nproc,_ _rlimit_rss,_ _rlimit_stack_ options described below. Resource limits in **sudoers **may be specified in one of the following for‐ mats: “value” Both the soft and hard resource limits are set to the same value. The special value “infinity” can be used to indicate that the value is unlimited. “soft,hard” Two comma-separated values. The soft limit is set to the first value and the hard limit is set to the second. Both values must either be enclosed in a set of double quotes, or the comma must be escaped with a backslash (‘\’). The special value “infinity” may be used in place of either value. “default” The default resource limit for the user will be used. This may be a user-specific value (see above) or the value of the resource limit when **sudo **was invoked for sys‐ tems that don't support per-user limits. “user” The invoking user's resource limits will be preserved when running the command. For example, to restore the historic core dump file size behavior, a line like the following may be used. **Defaults rlimit_core=default** Resource limits in **sudoers **are only supported by version 1.8.7 or higher. ### Quick guide to EBNF EBNF is a concise and exact way of describing the grammar of a language. Each EBNF defini‐ tion is made up of _production_ _rules_. For example: symbol ::= definition | alternate1 | alternate2 ... Each _production_ _rule_ references others and thus makes up a grammar for the language. EBNF also contains the following operators, which many readers will recognize from regular expres‐ sions. Do not, however, confuse them with “wildcard” characters, which have different mean‐ ings. ? Means that the preceding symbol (or group of symbols) is optional. That is, it may ap‐ pear once or not at all. * Means that the preceding symbol (or group of symbols) may appear zero or more times. + Means that the preceding symbol (or group of symbols) may appear one or more times. Parentheses may be used to group symbols together. For clarity, we will use single quotes ('') to designate what is a verbatim character string (as opposed to a symbol name). ### Aliases There are four kinds of aliases: _User_Alias_, _Runas_Alias_, _Host_Alias_ and _Cmnd_Alias_. Begin‐ ning with **sudo **1.9.0, _Cmd_Alias_ may be used in place of _Cmnd_Alias_ if desired. Alias ::= 'User_Alias' User_Alias_Spec (':' User_Alias_Spec)* | 'Runas_Alias' Runas_Alias_Spec (':' Runas_Alias_Spec)* | 'Host_Alias' Host_Alias_Spec (':' Host_Alias_Spec)* | 'Cmnd_Alias' Cmnd_Alias_Spec (':' Cmnd_Alias_Spec)* | 'Cmd_Alias' Cmnd_Alias_Spec (':' Cmnd_Alias_Spec)* User_Alias ::= NAME User_Alias_Spec ::= User_Alias '=' User_List Runas_Alias ::= NAME Runas_Alias_Spec ::= Runas_Alias '=' Runas_List Host_Alias ::= NAME Host_Alias_Spec ::= Host_Alias '=' Host_List Cmnd_Alias ::= NAME Cmnd_Alias_Spec ::= Cmnd_Alias '=' Cmnd_List NAME ::= [A-Z]([A-Z][0-9]_)* Each _alias_ definition is of the form Alias_Type NAME = item1, item2, ... where _Alias_Type_ is one of _User_Alias_, _Runas_Alias_, _Host_Alias_, or _Cmnd_Alias_. A NAME is a string of uppercase letters, numbers, and underscore characters (‘_’). A NAME **must **start with an uppercase letter. It is possible to put several alias definitions of the same type on a single line, joined by a colon (‘:’). For example: Alias_Type NAME = item1, item2, item3 : NAME = item4, item5 It is a syntax error to redefine an existing _alias_. It is possible to use the same name for _aliases_ of different types, but this is not recommended. The definitions of what constitutes a valid _alias_ member follow. User_List ::= User | User ',' User_List User ::= '!'* user name | '!'* #user-ID | '!'* %group | '!'* %#group-ID | '!'* +netgroup | '!'* %:nonunix_group | '!'* %:#nonunix_gid | '!'* User_Alias A _User_List_ is made up of one or more user names, user-IDs (prefixed with ‘#’), system group names and IDs (prefixed with ‘%’ and ‘%#’ respectively), netgroups (prefixed with ‘+’), non- Unix group names and IDs (prefixed with ‘%:’ and ‘%:#’ respectively), and _User_Alias_es. Each list item may be prefixed with zero or more ‘!’ operators. An odd number of ‘!’ operators negate the value of the item; an even number just cancel each other out. User netgroups are matched using the user and domain members only; the host member is not used when matching. A _user_ _name_, _user-ID_, _group_, _group-ID_, _netgroup_, _nonunix_group_ or _nonunix_gid_ may be enclosed in double quotes to avoid the need for escaping special characters. Alternately, special characters may be specified in escaped hex mode, e.g., \x20 for space. When using double quotes, any prefix characters must be included inside the quotes. The actual _nonunix_group_ and _nonunix_gid_ syntax depends on the underlying group provider plu‐ gin. For instance, the QAS AD plugin supports the following formats: **• **Group in the same domain: "%:Group Name" **• **Group in any domain: "%:Group " **• **Group SID: "%:S-1-2-34-5678901234-5678901234-5678901234-567" See “GROUP PROVIDER PLUGINS” for more information. Quotes around group names are optional. Unquoted strings must use a backslash (‘\’) to es‐ cape spaces and special characters. See “Other special characters and reserved words” for a list of characters that need to be escaped. Runas_List ::= Runas_Member | Runas_Member ',' Runas_List Runas_Member ::= '!'* user name | '!'* #user-ID | '!'* %group | '!'* %#group-ID | '!'* %:nonunix_group | '!'* %:#nonunix_gid | '!'* +netgroup | '!'* Runas_Alias | '!'* ALL A _Runas_List_ is similar to a _User_List_ except that instead of _User_Alias_es it can contain _Runas_Alias_es. User names and groups are matched as strings. In other words, two users (groups) with the same user (group) ID are considered to be distinct. If you wish to match all user names with the same user-ID (e.g., **root **and **toor**), you can use a user-ID instead of a name (#0 in the example given). The user-ID or group-ID specified in a _Runas_Member_ need not be listed in the password or group database. Host_List ::= Host | Host ',' Host_List Host ::= '!'* host name | '!'* ip_addr | '!'* network(/netmask)? | '!'* +netgroup | '!'* Host_Alias | '!'* ALL A _Host_List_ is made up of one or more host names, IP addresses, network numbers, netgroups (prefixed with ‘+’), and other aliases. Again, the value of an item may be negated with the ‘!’ operator. Host netgroups are matched using the host (both qualified and unqualified) and domain members only; the user member is not used when matching. If you specify a network number without a netmask, **sudo **will query each of the local host's network interfaces and, if the network number corresponds to one of the hosts's network interfaces, will use the netmask of that interface. The netmask may be specified either in standard IP address notation (e.g., 255.255.255.0 or ffff:ffff:ffff:ffff::), or CIDR notation (number of bits, e.g., 24 or 64). A host name may include shell-style wildcards (see the “Wildcards” section below), but unless the _hostname_ command on your machine returns the fully qualified host name, you'll need to use the _fqdn_ flag for wildcards to be useful. **sudo **only inspects actual network in‐ terfaces; this means that IP address 127.0.0.1 (localhost) will never match. Also, the host name “localhost” will only match if that is the actual host name, which is usually only the case for non-networked systems. digest ::= [A-Fa-f0-9]+ | [A-Za-z0-9\+/=]+ Digest_Spec ::= "sha224" ':' digest | "sha256" ':' digest | "sha384" ':' digest | "sha512" ':' digest Digest_List ::= Digest_Spec | Digest_Spec ',' Digest_List Cmnd_List ::= Cmnd | Cmnd ',' Cmnd_List command name ::= regex | file name command ::= command name | command name args | command name regex | command name '""' | ALL Edit_Spec ::= "sudoedit" file name+ | "sudoedit" regex | "sudoedit" List_Spec ::= "list" Cmnd ::= Digest_List? '!'* command | '!'* directory | '!'* Edit_Spec | '!'* List_Spec | '!'* Cmnd_Alias A _Cmnd_List_ is a list of one or more commands, directories, or aliases. A command is a fully qualified file name, which may include shell-style wildcards (see the “Wildcards” section be‐ low), or a regular expression that starts with ‘^’ and ends with ‘$’ (see the “Regular expressions” section below). A directory is a fully qualified path name ending in a ‘/’. When you specify a directory in a _Cmnd_List_, the user will be able to run any file within that directory (but not in any sub-directories therein). If no command line arguments are specified, the user may run the command with any arguments they choose. Command line argu‐ ments can include wildcards or be a regular expression that starts with ‘^’ and ends with ‘$’. If the command line arguments consist of ‘""’, the command may only be run with _no_ ar‐ guments. If a _Cmnd_ has associated command line arguments, the arguments in the _Cmnd_ must match those given by the user on the command line. If the arguments in a _Cmnd_ begin with the ‘^’ charac‐ ter, they will be interpreted as a regular expression and matched accordingly. Otherwise, shell-style wildcards are used when matching. Unless a regular expression is specified, the following characters must be escaped with a ‘\’ if they are used in command arguments: ‘,’, ‘:’, ‘=’, ‘\’. To prevent arguments in a _Cmnd_ that begin with a ‘^’ character from being in‐ terpreted as a regular expression, the ‘^’ must be escaped with a ‘\’. There are two commands built into **sudo **itself: “list” and “sudoedit”. Unlike other commands, these two must be specified in the _sudoers_ file _without_ a leading path. The “list” built-in can be used to permit a user to list another user's privileges with **sudo**'s **-U **option. For example, “sudo -l -U otheruser”. A user with the “list” privilege is able to list another user's privileges even if they don't have permission to run commands as that user. By default, only root or a user with the ability to run any command as either root or the specified _user_ on the current host may use the **-U **option. No command line argu‐ ments may be specified with the “list” built-in. The “sudoedit” built-in is used to permit a user to run **sudo **with the **-e **option (or as **sudoedit**). It may take command line arguments just as a normal command does. Unlike other commands, “sudoedit” is built into **sudo **itself and must be specified in the _sudoers_ file _without_ a leading path. If a leading path is present, for example _/usr/bin/sudoedit_, the path name will be silently converted to “sudoedit”. A fully-qualified path for **sudoedit **is treated as an error by **visudo**. A _command_ may be preceded by a _Digest_List_, a comma-separated list of one or more _Digest_Spec_ entries. If a _Digest_List_ is present, the command will only match successfully if it can be verified using one of the SHA-2 digests in the list. Starting with version 1.9.0, the **ALL** reserved word can be used in conjunction with a _Digest_List_. The following digest formats are supported: sha224, sha256, sha384, and sha512. The string may be specified in either hex or base64 format (base64 is more compact). There are several utilities capable of generating SHA-2 digests in hex format such as openssl, shasum, sha224sum, sha256sum, sha384sum, sha512sum. For example, using openssl: $ openssl dgst -sha224 /bin/ls SHA224(/bin/ls)= 118187da8364d490b4a7debbf483004e8f3e053ec954309de2c41a25 It is also possible to use openssl to generate base64 output: $ openssl dgst -binary -sha224 /bin/ls | openssl base64 EYGH2oNk1JC0p9679IMATo8+BT7JVDCd4sQaJQ== Warning, if the user has write access to the command itself (directly or via a **sudo **command), it may be possible for the user to replace the command after the digest check has been per‐ formed but before the command is executed. A similar race condition exists on systems that lack the [_fexecve_(2)](https://www.chedong.com/phpMan.php/man/fexecve/2/markdown) system call when the directory in which the command is located is writable by the user. See the description of the _fdexec_ setting for more information on how **sudo **executes commands that have an associated digest. Command digests are only supported by version 1.8.7 or higher. ### Defaults Certain configuration options may be changed from their default values at run-time via one or more _Default_Entry_ lines. These may affect all users on any host (‘Defaults’), all users on a specific host (‘Defaults@host’), a specific user (‘Defaults:user’), a specific command (‘Defaults!cmnd’), or commands being run as a specific user (‘Defaults>runasuser’). White space is not permitted between ‘Defaults’ and the ‘@’, ‘:’, ‘!’, or ‘>’ characters. While a comma-separated list may be used in place of a single value after the ‘@’, ‘:’, ‘!’, or ‘>’ character, using an alias instead of a list is often improve readability. Per-command entries may not include command line arguments. If you need to specify arguments, define a _Cmnd_Alias_ and reference that instead. Default_Type ::= 'Defaults' | 'Defaults@' Host_List | 'Defaults:' User_List | 'Defaults!' Cmnd_List | 'Defaults>' Runas_List Default_Entry ::= Default_Type Parameter_List Parameter_List ::= Parameter | Parameter ',' Parameter_List Parameter ::= Parameter '=' Value | Parameter '+=' Value | Parameter '-=' Value | '!'* Parameter Parameters may be **flags**, **integer **values, **strings**, or **lists**. Flags are implicitly boolean and can be turned off via the ‘!’ operator. Some integer, string and list parameters may also be used in a boolean context to disable them. Values may be enclosed in double quotes ("") when they contain multiple words. Special characters may be escaped with a backslash (‘\’). To include a literal backslash character in a command line argument you must escape the back‐ slash twice. For example, to match ‘\n’ as part of a command line argument, you must use ‘\\\\n’ in the _sudoers_ file. This is due to there being two levels of escaping, one in the _sudoers_ parser itself and another when command line arguments are matched by the [_fnmatch_(3)](https://www.chedong.com/phpMan.php/man/fnmatch/3/markdown) or [_regexec_(3)](https://www.chedong.com/phpMan.php/man/regexec/3/markdown) function. Lists have two additional assignment operators, ‘+=’ and ‘-=’. These operators are used to add to and delete from a list respectively. It is not an error to use the ‘-=’ operator to remove an element that does not exist in a list. Defaults entries are parsed in the following order: global, host, user, and runas Defaults first, then command defaults. If there are multiple Defaults settings of the same type, the last matching setting is used. The following Defaults settings are parsed before all others since they may affect subsequent entries: _fqdn_, _group_plugin_, _runas_default_, _sudoers_locale_. See “SUDOERS OPTIONS” for a list of supported Defaults parameters. ### User specification User_Spec ::= User_List Host_List '=' Cmnd_Spec_List \ (':' Host_List '=' Cmnd_Spec_List)* Cmnd_Spec_List ::= Cmnd_Spec | Cmnd_Spec ',' Cmnd_Spec_List Cmnd_Spec ::= Runas_Spec? Option_Spec* (Tag_Spec ':')* Cmnd Runas_Spec ::= '(' Runas_List? (':' Runas_List)? ')' Option_Spec ::= (SELinux_Spec | Date_Spec | Timeout_Spec | Chdir_Spec | Chroot_Spec) SELinux_Spec ::= ('ROLE=role' | 'TYPE=type') AppArmor_Spec ::= 'APPARMOR_PROFILE=profile' Date_Spec ::= ('NOTBEFORE=timestamp' | 'NOTAFTER=timestamp') Timeout_Spec ::= 'TIMEOUT=timeout' Chdir_Spec ::= 'CWD=directory' Chroot_Spec ::= 'CHROOT=directory' Tag_Spec ::= ('EXEC' | 'NOEXEC' | 'FOLLOW' | 'NOFOLLOW' | 'LOG_INPUT' | 'NOLOG_INPUT' | 'LOG_OUTPUT' | 'NOLOG_OUTPUT' | 'MAIL' | 'NOMAIL' | 'INTERCEPT' | 'NOINTERCEPT' | 'PASSWD' | 'NOPASSWD' | 'SETENV' | 'NOSETENV') A **user specification **determines which commands a user may run (and as what user) on specified hosts. By default, commands are run as **root **(unless _runas_default_ has been set to a differ‐ ent value) but this can also be changed on a per-command basis. The basic structure of a user specification is “who where = (as_whom) what”. Let's break that down into its constituent parts: ### Runas_Spec A _Runas_Spec_ determines the user and/or the group that a command may be run as. A fully- specified _Runas_Spec_ consists of two _Runas_List_s (as defined above) separated by a colon (‘:’) and enclosed in a set of parentheses. The first _Runas_List_ indicates which users the command may be run as via the **-u **option. The second defines a list of groups that may be specified via the **-g **option (in addition to any of the target user's groups). If both _Runas_List_s are specified, the command may be run with any combination of users and groups listed in their respective _Runas_List_s. If only the first is specified, the command may be run as any user in the list and, optionally, with any group the target user belongs to. If the first _Runas_List_ is empty but the second is specified, the command may be run as the in‐ voking user with the group set to any listed in the _Runas_List_. If both _Runas_List_s are empty, the command may only be run as the invoking user and the group, if specified, must be one that the invoking user is a member of. If no _Runas_Spec_ is specified, the command may only be run as the _runas_default_ user (**root **by default) and the group, if specified, must be one that the _runas_default_ user is a member of. A _Runas_Spec_ sets the default for the commands that follow it. What this means is that for the entry: dgb boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm The user **dgb **may run _/bin/ls_, _/bin/kill_, and _/usr/bin/lprm_ on the host boulder—but only as **operator**. For example: $ sudo -u operator /bin/ls It is also possible to override a _Runas_Spec_ later on in an entry. If we modify the entry like so: dgb boulder = (operator) /bin/ls, (root) /bin/kill, /usr/bin/lprm Then user **dgb **is now allowed to run _/bin/ls_ as **operator**, but _/bin/kill_ and _/usr/bin/lprm_ as **root**. We can extend this to allow **dgb **to run _/bin/ls_ with either the user or group set to **operator**: dgb boulder = (operator : operator) /bin/ls, (root) /bin/kill,\ /usr/bin/lprm While the group portion of the _Runas_Spec_ permits the user to run as command with that group, it does not force the user to do so. If no group is specified on the command line, the com‐ mand will run with the group listed in the target user's password database entry. The fol‐ lowing would all be permitted by the sudoers entry above: $ sudo -u operator /bin/ls $ sudo -u operator -g operator /bin/ls $ sudo -g operator /bin/ls In the following example, user **tcm **may run commands that access a modem device file with the dialer group. tcm boulder = (:dialer) /usr/bin/tip, /usr/bin/cu,\ /usr/local/bin/minicom In this example only the group will be set, the command still runs as user **tcm**. For example: $ sudo -g dialer /usr/bin/cu Multiple users and groups may be present in a _Runas_Spec_, in which case the user may select any combination of users and groups via the **-u **and **-g **options. In this example: alan ALL = (root, bin : operator, system) ALL user **alan **may run any command as either user **root **or **bin**, optionally setting the group to op‐ erator or system. ### Option_Spec A _Cmnd_ may have zero or more options associated with it. Options may consist of SELinux roles and/or types, AppArmor profiles, start and/or end dates and command timeouts. Once an option is set for a _Cmnd_, subsequent _Cmnd_s in the _Cmnd_Spec_List_, inherit that option unless it is overridden by another option. Option names are reserved words in _sudoers_. This means that none of the valid option names (see below) can be used when declaring an alias. ### SELinux_Spec On systems with SELinux support, _sudoers_ file entries may optionally have an SELinux role and/or type associated with a command. This can be used to implement a form of role-based access control (RBAC). If a role or type is specified with the command it will override any default values specified in _sudoers_. A role or type specified on the command line, however, will supersede the values in _sudoers_. ### AppArmor_Spec On systems supporting AppArmor, _sudoers_ file entries may optionally specify an AppArmor pro‐ file that should be used to confine a command. If an AppArmor profile is specified with the command, it will override any default values specified in _sudoers_. Appropriate profile tran‐ sition rules must be defined to support the profile change specified for a user. AppArmor profiles can be specified in any way that complies with the rules of [_aa_change_profile_(2)](https://www.chedong.com/phpMan.php/man/aachangeprofile/2/markdown). For instance, in the following _sudoers_ entry alice ALL = (root) APPARMOR_PROFILE=my-profile ALL the user **alice **may run any command as **root **under confinement by the profile ‘my-profile’. You can also stack profiles, or allow a user to run commands unconfined by any profile. For example: bob ALL = (root) APPARMOR_PROFILE=foo//&bar /usr/bin/vi cathy ALL = (root) APPARMOR_PROFILE=unconfined /bin/ls These _sudoers_ entries allow user **bob **to run _/usr/bin/vi_ as **root **under the stacked profiles ‘foo’ and ‘bar’, and user **cathy **to run _/bin/ls_ without any confinement at all. ### Date_Spec **sudoers **rules can be specified with a start and end date via the NOTBEFORE and NOTAFTER set‐ tings. The time stamp must be specified in “Generalized Time” as defined by RFC 4517. The format is effectively ‘yyyymmddHHMMSSZ’ where the minutes and seconds are optional. The ‘Z’ suffix indicates that the time stamp is in Coordinated Universal Time (UTC). It is also pos‐ sible to specify a timezone offset from UTC in hours and minutes instead of a ‘Z’. For exam‐ ple, ‘-0500’ would correspond to Eastern Standard time in the US. As an extension, if no ‘Z’ or timezone offset is specified, local time will be used. The following are all valid time stamps: 20170214083000Z 2017021408Z 20160315220000-0500 20151201235900 ### Timeout_Spec A command may have a timeout associated with it. If the timeout expires before the command has exited, the command will be terminated. The timeout may be specified in combinations of days, hours, minutes, and seconds with a single-letter case-insensitive suffix that indicates the unit of time. For example, a timeout of 7 days, 8 hours, 30 minutes, and 10 seconds would be written as ‘7d8h30m10s’. If a number is specified without a unit, seconds are as‐ sumed. Any of the days, minutes, hours, or seconds may be omitted. The order must be from largest to smallest unit and a unit may not be specified more than once. The following are all _valid_ timeout values: ‘7d8h30m10s’, ‘14d’, ‘8h30m’, ‘600s’, ‘3600’. The following are _invalid_ timeout values: ‘12m2w1d’, ‘30s10m4h’, ‘1d2d3h’. This setting is only supported by version 1.8.20 or higher. ### Chdir_Spec The working directory that the command will be run in can be specified using the CWD setting. The _directory_ must be a fully-qualified path name beginning with a ‘/’ or ‘~’ character, or the special value “*”. A value of “*” indicates that the user may specify the working direc‐ tory by running **sudo **with the **-D **option. By default, commands are run from the invoking user's current working directory, unless the **-i **option is given. Path names of the form _~user/path/name_ are interpreted as being relative to the named user's home directory. If the user name is omitted, the path will be relative to the runas user's home directory. This setting is only supported by version 1.9.3 or higher. ### Chroot_Spec The root directory that the command will be run in can be specified using the CHROOT setting. The _directory_ must be a fully-qualified path name beginning with a ‘/’ or ‘~’ character, or the special value “*”. A value of “*” indicates that the user may specify the root directory by running **sudo **with the **-R **option. This setting can be used to run the command in a [_chroot_(2)](https://www.chedong.com/phpMan.php/man/chroot/2/markdown) “sandbox” similar to the [_chroot_(8)](https://www.chedong.com/phpMan.php/man/chroot/8/markdown) utility. Path names of the form _~user/path/name_ are interpreted as being relative to the named user's home directory. If the user name is omitted, the path will be relative to the runas user's home directory. This setting is only supported by version 1.9.3 or higher. ### Tag_Spec A command may have zero or more tags associated with it. The following tag values are sup‐ ported: EXEC, NOEXEC, FOLLOW, NOFOLLOW, LOG_INPUT, NOLOG_INPUT, LOG_OUTPUT, NOLOG_OUTPUT, MAIL, NOMAIL, INTERCEPT, NOINTERCEPT, PASSWD, NOPASSWD, SETENV, and NOSETENV. Once a tag is set on a _Cmnd_, subsequent _Cmnd_s in the _Cmnd_Spec_List_, inherit the tag unless it is overrid‐ den by the opposite tag (in other words, PASSWD overrides NOPASSWD and NOEXEC overrides EXEC). EXEC and NOEXEC If **sudo **has been compiled with _noexec_ support and the underlying operating system supports it, the NOEXEC tag can be used to prevent a dynamically-linked executable from running fur‐ ther commands itself. In the following example, user **aaron **may run _/usr/bin/more_ and _/usr/bin/vi_ on the host shanty, but shell escapes will be disabled. aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi See the “Preventing shell escapes” section below for more details on how NOEXEC works and whether or not it will work on your system. FOLLOW and NOFOLLOW Starting with version 1.8.15, **sudoedit **will not open a file that is a symbolic link unless the _sudoedit_follow_ flag is enabled. The FOLLOW and NOFOLLOW tags override the value of _sudoedit_follow_ and can be used to permit (or deny) the editing of symbolic links on a per- command basis. These tags are only effective for the _sudoedit_ command and are ignored for all other commands. LOG_INPUT and NOLOG_INPUT These tags override the value of the _log_input_ flag on a per-command basis. For more in‐ formation, see “I/O LOGGING”. LOG_OUTPUT and NOLOG_OUTPUT These tags override the value of the _log_output_ flag on a per-command basis. For more in‐ formation, see “I/O LOGGING”. MAIL and NOMAIL These tags provide fine-grained control over whether mail will be sent when a user runs a command by overriding the value of the _mail_all_cmnds_ flag on a per-command basis. They have no effect when **sudo **is run with the **-l **or **-v **options. A NOMAIL tag will also override the _mail_always_ and _mail_no_perms_ options. For more information, see the descriptions of _mail_all_cmnds_, _mail_always_, and _mail_no_perms_ in the “SUDOERS OPTIONS” section below. PASSWD and NOPASSWD By default, **sudo **requires that a user authenticate before running a command. This behavior can be modified via the NOPASSWD tag. Like a _Runas_Spec_, the NOPASSWD tag sets a default for the commands that follow it in the _Cmnd_Spec_List_. Conversely, the PASSWD tag can be used to reverse things. For example: ray rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm would allow the user **ray **to run _/bin/kill_, _/bin/ls_, and _/usr/bin/lprm_ as **root **on the ma‐ chine “rushmore” without authenticating himself. If we only want **ray **to be able to run _/bin/kill_ without a password the entry would be: ray rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm Note, however, that the PASSWD tag has no effect on users who are in the group specified by the _exempt_group_ setting. By default, if the NOPASSWD tag is applied to any of a user's entries for the current host, the user will be able to run ‘sudo -l’ without a password. Additionally, a user may only run ‘sudo -v’ without a password if all of the user's entries for the current host have the NOPASSWD tag. This behavior may be overridden via the _verifypw_ and _listpw_ options. SETENV and NOSETENV These tags override the value of the _setenv_ flag on a per-command basis. If SETENV has been set for a command, the user may disable the _env_reset_ flag from the command line via the **-E **option. Additionally, environment variables set on the command line are not subject to the restrictions imposed by _env_check_, _env_delete_, or _env_keep_. As such, only trusted users should be allowed to set variables in this manner. If the command matched is **ALL**, the SETENV tag is implied for that command; this default may be overridden by use of the NOSETENV tag. INTERCEPT and NOINTERCEPT If **sudo **has been compiled with _intercept_ support and the underlying operating system sup‐ ports it, the INTERCEPT tag can be used to cause programs spawned by a command to be vali‐ dated against _sudoers_ and logged just like they would be if run through **sudo **directly. This is useful in conjunction with commands that allow shell escapes such as editors, shells, and paginators. There is additional overhead due to the policy check that may add latency when running commands such as shell scripts that execute a large number of sub-com‐ mands. For interactive commands, such as a shell or editor, the overhead is not usually noticeable. In the following example, user **chuck **may run any command on the machine “research” in in‐ tercept mode. chuck research = INTERCEPT: ALL See the “Preventing shell escapes” section below for more details on how INTERCEPT works and whether or not it will work on your system. ### Wildcards **sudo **allows shell-style _wildcards_ (aka meta or glob characters) to be used in host names, path names, and command line arguments in the _sudoers_ file. Wildcard matching is done via the [_glob_(3)](https://www.chedong.com/phpMan.php/man/glob/3/markdown) and [_fnmatch_(3)](https://www.chedong.com/phpMan.php/man/fnmatch/3/markdown) functions as specified by IEEE Std 1003.1 (“POSIX.1”). * Matches any set of zero or more characters (including white space). ? Matches any single character (including white space). [...] Matches any character in the specified range. [!...] Matches any character _not_ in the specified range. \x For any character ‘x’, evaluates to ‘x’. This is used to escape special characters such as: ‘*’, ‘?’, ‘[’, and ‘]’. **These are not regular expressions. **Unlike a regular expression there is no way to match one or more characters within a range. Character classes may be used if your system's [_glob_(3)](https://www.chedong.com/phpMan.php/man/glob/3/markdown) and [_fnmatch_(3)](https://www.chedong.com/phpMan.php/man/fnmatch/3/markdown) functions support them. However, because the ‘:’ character has special meaning in _sudoers_, it must be escaped. For example: /bin/ls [[\:alpha\:]]* Would match any file name beginning with a letter. A forward slash (‘/’) will _not_ be matched by wildcards used in the file name portion of the command. This is to make a path like: /usr/bin/* match _/usr/bin/who_ but not _/usr/bin/X11/xterm_. When matching the command line arguments, however, a slash _does_ get matched by wildcards since command line arguments may contain arbitrary strings and not just path names. ### Wildcards in command line arguments should be used with care. Wildcards can match any character, including white space. In most cases, it is safer to use a regular expression to match command line arguments. For more information, see “Wildcards in command arguments” below. ### Exceptions to wildcard rules The following exceptions apply to the above rules: "" If the empty string ‘""’ is the only command line argument in the _sudoers_ file en‐ try it means that command is not allowed to be run with _any_ arguments. sudoedit Command line arguments to the _sudoedit_ built-in command should always be path names, so a forward slash (‘/’) will not be matched by a wildcard. ### Regular expressions Starting with version 1.9.10, it is possible to use regular expressions for path names and command line arguments. Regular expressions are more expressive than shell-style _wildcards_ and are usually safer because they provide a greater degree of control when matching. The type of regular expressions supported by **sudoers **are POSIX extended regular expressions, sim‐ ilar to those used by the [_egrep_(1)](https://www.chedong.com/phpMan.php/man/egrep/1/markdown) utility. They are usually documented in the [_regex_(7)](https://www.chedong.com/phpMan.php/man/regex/7/markdown) or [_re_format_(7)](https://www.chedong.com/phpMan.php/man/reformat/7/markdown) manual, depending on the system. As an extension, if the regular expression be‐ gins with “(?i)”, it will be matched in a case-insensitive manner. In _sudoers_, regular expressions must start with a ‘^’ character and end with a ‘$’. This makes it explicit what is, or is not, a regular expression. Either the path name, the com‐ mand line arguments or both may be regular expressions. Because the path name and arguments are matched separately, it is even possible to use wildcards for the path name and regular expressions for the arguments. It is not possible to use a single regular expression to match both the command and its arguments. Regular expressions in _sudoers_ are limited to 1024 characters. There is no need to escape _sudoers_ special characters in a regular expression other than the pound sign (‘#’). In the following example, user **john **can run the [_passwd_(1)](https://www.chedong.com/phpMan.php/man/passwd/1/markdown) command as **root **on any host but is not allowed to change **root**'s password. This kind of rule is impossible to express safely us‐ ing wildcards. john ALL = /usr/bin/passwd ^[a-zA-Z0-9_]+$,\ !/usr/bin/passwd root It is also possible to use a regular expression in conjunction with **sudoedit **rules. The fol‐ lowing rule would give user bob the ability to edit the _/etc/motd_, _/etc/issue_, and _/etc/hosts_ files only. bob ALL = sudoedit ^/etc/(motd|issue|hosts)$ Regular expressions may also be used to match the command itself. In this example, a regular expression is used to allow user **sid **to run the _/usr/sbin/groupadd_, _/usr/sbin/groupmod_, _/usr/sbin/groupdel_, _/usr/sbin/useradd_, _/usr/sbin/usermod_, and _/usr/sbin/userdel_ commands as **root**. sid ALL = ^/usr/sbin/(group|user)(add|mod|del)$ One disadvantage of using a regular expression to match the command name is that it is not possible to match relative paths such as _./useradd_ or _../sbin/useradd_. This has security im‐ plications when a regular expression is used for the command name in conjunction with the negation operator, ‘!’, as such rules can be trivially bypassed. Because of this, using a negated regular expression for the command name is **strongly discouraged**. This does not apply to negated commands that only use a regular expression to match the command arguments. See “Regular expressions in command names” below for more information. ### Including other files from within sudoers It is possible to include other _sudoers_ files from within the _sudoers_ file currently being parsed using the _@include_ and _@includedir_ directives. For compatibility with sudo versions prior to 1.9.1, _#include_ and _#includedir_ are also accepted. An include file can be used, for example, to keep a site-wide _sudoers_ file in addition to a local, per-machine file. For the sake of this example the site-wide _sudoers_ file will be _/etc/sudoers_ and the per-machine one will be _/etc/sudoers.local_. To include _/etc/sudoers.local_ from within _/etc/sudoers_ one would use the following line in _/etc/sudoers_: @include /etc/sudoers.local When **sudo **reaches this line it will suspend processing of the current file (_/etc/sudoers_) and switch to _/etc/sudoers.local_. Upon reaching the end of _/etc/sudoers.local_, the rest of _/etc/sudoers_ will be processed. Files that are included may themselves include other files. A hard limit of 128 nested include files is enforced to prevent include file loops. Starting with version 1.9.1, the path to the include file may contain white space if it is escaped with a backslash (‘\’). Alternately, the entire path may be enclosed in double quotes (""), in which case no escaping is necessary. To include a literal backslash in the path, ‘\\’ should be used. If the path to the include file is not fully-qualified (does not begin with a ‘/’), it must be located in the same directory as the sudoers file it was included from. For example, if _/etc/sudoers_ contains the line: @include sudoers.local the file that will be included is _/etc/sudoers.local_. The file name may also include the ‘%h’ escape, signifying the short form of the host name. In other words, if the machine's host name is “xerxes”, then @include /etc/sudoers.%h will cause **sudo **to include the file _/etc/sudoers.xerxes_. Any path name separator characters (‘/’) present in the host name will be replaced with an underbar (‘_’) during expansion. The _@includedir_ directive can be used to create a _sudoers.d_ directory that the system package manager can drop _sudoers_ file rules into as part of package installation. For example, given: @includedir /etc/sudoers.d **sudo **will suspend processing of the current file and read each file in _/etc/sudoers.d_, skip‐ ping file names that end in ‘~’ or contain a ‘.’ character to avoid causing problems with package manager or editor temporary/backup files. Files are parsed in sorted lexical order. That is, _/etc/sudoers.d/01_first_ will be parsed before _/etc/sudoers.d/10_second_. Be aware that because the sorting is lexical, not numeric, _/etc/sudoers.d/1_whoops_ would be loaded _after_ _/etc/sudoers.d/10_second_. Using a consistent number of leading zeroes in the file names can be used to avoid such problems. After parsing the files in the directory, control returns to the file that contained the _@includedir_ direc‐ tive. Unlike files included via _@include_, **visudo **will not edit the files in a _@includedir_ directory unless one of them contains a syntax error. It is still possible to run **visudo **with the **-f** flag to edit the files directly, but this will not catch the redefinition of an _alias_ that is also present in a different file. ### Other special characters and reserved words The pound sign (‘#’) is used to indicate a comment (unless it is part of a #include directive or unless it occurs in the context of a user name and is followed by one or more digits, in which case it is treated as a user-ID). Both the comment character and any text after it, up to the end of the line, are ignored. The reserved word **ALL **is a built-in _alias_ that always causes a match to succeed. It can be used wherever one might otherwise use a _Cmnd_Alias_, _User_Alias_, _Runas_Alias_, or _Host_Alias_. Attempting to define an _alias_ named **ALL **will result in a syntax error. Using **ALL **can be dan‐ gerous since in a command context, it allows the user to run _any_ command on the system. The following option names permitted in an _Option_Spec_ are also considered reserved words: CHROOT, ROLE, TYPE, TIMEOUT, CWD, NOTBEFORE and NOTAFTER. Attempting to define an _alias_ with the same name as one of the options will result in a syntax error. An exclamation point (‘!’) can be used as a logical _not_ operator in a list or _alias_ as well as in front of a _Cmnd_. This allows one to exclude certain values. For the ‘!’ operator to be effective, there must be something for it to exclude. For example, to match all users ex‐ cept for **root **one would use: ALL, !root If the **ALL**, is omitted, as in: !root it would explicitly deny **root **but not match any other users. This is different from a true “negation” operator. Note, however, that using a ‘!’ in conjunction with the built-in **ALL **alias to allow a user to run “all but a few” commands rarely works as intended (see “SECURITY NOTES” below). Long lines can be continued with a backslash (‘\’) as the last character on the line. White space between elements in a list as well as special syntactic characters in a _User_ _Specification_ (‘=’, ‘:’, ‘(’, ‘)’) is optional. The following characters must be escaped with a backslash (‘\’) when used as part of a word (e.g., a user name or host name): ‘!’, ‘=’, ‘:’, ‘,’, ‘(’, ‘)’, ‘\’. ## SUDOERS OPTIONS **sudo**'s behavior can be modified by _Default_Entry_ lines, as explained earlier. A list of all supported Defaults parameters, grouped by type, are listed below. **Boolean Flags**: always_query_group_plugin If a _group_plugin_ is configured, use it to resolve groups of the form ‘%group’ as long as there is not also a system group of the same name. Normally, only groups of the form ‘%:group’ are passed to the _group_plugin_. This flag is _off_ by default. always_set_home If enabled, **sudo **will set the HOME environment variable to the home direc‐ tory of the target user (which is the _runas_default_ user unless the **-u **op‐ tion is used). This flag is largely obsolete and has no effect unless the _env_reset_ flag has been disabled or HOME is present in the _env_keep_ list, both of which are strongly discouraged. This flag is _off_ by default. authenticate If set, users must authenticate themselves via a password (or other means of authentication) before they may run commands. This default may be over‐ ridden via the PASSWD and NOPASSWD tags. This flag is _on_ by default. case_insensitive_group If enabled, group names in _sudoers_ will be matched in a case insensitive manner. This may be necessary when users are stored in LDAP or AD. This flag is _on_ by default. case_insensitive_user If enabled, user names in _sudoers_ will be matched in a case insensitive manner. This may be necessary when groups are stored in LDAP or AD. This flag is _on_ by default. closefrom_override If set, the user may use the **-C **option which overrides the default starting point at which **sudo **begins closing open file descriptors. This flag is _off_ by default. compress_io If set, and **sudo **is configured to log a command's input or output, the I/O logs will be compressed using **zlib**. This flag is _on_ by default when **sudo** is compiled with **zlib **support. exec_background By default, **sudo **runs a command as the foreground process as long as **sudo** itself is running in the foreground. When the _exec_background_ flag is en‐ abled and the command is being run in a pseudo-terminal (due to I/O logging or the _use_pty_ flag), the command will be run as a background process. At‐ tempts to read from the controlling terminal (or to change terminal set‐ tings) will result in the command being suspended with the SIGTTIN signal (or SIGTTOU in the case of terminal settings). If this happens when **sudo** is a foreground process, the command will be granted the controlling termi‐ nal and resumed in the foreground with no user intervention required. The advantage of initially running the command in the background is that **sudo** need not read from the terminal unless the command explicitly requests it. Otherwise, any terminal input must be passed to the command, whether it has required it or not (the kernel buffers terminals so it is not possible to tell whether the command really wants the input). This is different from historic _sudo_ behavior or when the command is not being run in a pseudo- terminal. For this to work seamlessly, the operating system must support the auto‐ matic restarting of system calls. Unfortunately, not all operating systems do this by default, and even those that do may have bugs. For example, ma‐ cOS fails to restart the [_tcgetattr_(3)](https://www.chedong.com/phpMan.php/man/tcgetattr/3/markdown) and [_tcsetattr_(3)](https://www.chedong.com/phpMan.php/man/tcsetattr/3/markdown) functions (this is a bug in macOS). Furthermore, because this behavior depends on the command stopping with the SIGTTIN or SIGTTOU signals, programs that catch these signals and suspend themselves with a different signal (usually SIGTOP) will not be automatically foregrounded. Some versions of the linux [_su_(1)](https://www.chedong.com/phpMan.php/man/su/1/markdown) command behave this way. This flag is _off_ by default. This setting is only supported by version 1.8.7 or higher. It has no ef‐ fect unless I/O logging is enabled or the _use_pty_ flag is enabled. env_editor If set, **visudo **will use the value of the SUDO_EDITOR, VISUAL or EDITOR en‐ vironment variables before falling back on the default editor list. **visudo** is typically run as **root **so this flag may allow a user with **visudo **privi‐ leges to run arbitrary commands as **root **without logging. An alternative is to place a colon-separated list of “safe” editors int the _editor_ setting. **visudo **will then only use SUDO_EDITOR, VISUAL or EDITOR if they match a value specified in _editor_. If the _env_reset_ flag is enabled, the SUDO_EDITOR, VISUAL and/or EDITOR environment variables must be present in the _env_keep_ list for the _env_editor_ flag to function when **visudo **is in‐ voked via **sudo**. This flag is _on_ by default. env_reset If set, **sudo **will run the command in a minimal environment containing the TERM, PATH, HOME, MAIL, SHELL, LOGNAME, USER and SUDO_* variables. Any variables in the caller's environment or in the file specified by the _restricted_env_file_ setting that match the _env_keep_ and _env_check_ lists are then added, followed by any variables present in the file specified by the _env_file_ setting (if any). The contents of the _env_keep_ and _env_check_ lists, as modified by global Defaults parameters in _sudoers_, are displayed when **sudo **is run by **root **with the **-V **option. If the _secure_path_ setting is enabled, its value will be used for the PATH environment variable. This flag is _on_ by default. fast_glob Normally, **sudo **uses the [_glob_(3)](https://www.chedong.com/phpMan.php/man/glob/3/markdown) function to do shell-style globbing when matching path names. However, since it accesses the file system, [_glob_(3)](https://www.chedong.com/phpMan.php/man/glob/3/markdown) can take a long time to complete for some patterns, especially when the pattern references a network file system that is mounted on demand (auto mounted). The _fast_glob_ flag causes **sudo **to use the [_fnmatch_(3)](https://www.chedong.com/phpMan.php/man/fnmatch/3/markdown) function, which does not access the file system to do its matching. The disadvantage of _fast_glob_ is that it is unable to match relative paths such as _./ls_ or _../bin/ls_. This has security implications when path names that include globbing characters are used with the negation operator, ‘!’, as such rules can be trivially bypassed. As such, this flag should not be used when the _sudoers_ file contains rules that contain negated path names which include globbing characters. This flag is _off_ by default. log_passwords Most programs that require a user's password will disable echo before read‐ ing the password to avoid displaying the plaintext password on the screen. However, if terminal input is being logged (see “I/O LOGGING”), the pass‐ word will still be present in the I/O log. If the _log_passwords_ option is disabled, **sudoers **will attempt to prevent passwords from being logged. It does this by using the regular expressions in _passprompt_regex_ to match a password prompt in the terminal output buffer. When a match is found, in‐ put characters in the I/O log will be replaced with ‘*’ until either a line feed or carriage return is found in the terminal input or a new terminal output buffer is received. If, however, a program displays characters as the user types (such as **sudo **when _pwfeedback_ is set), only the first char‐ acter of the password will be replaced in the I/O log. This option has no effect unless _log_input_ or _log_ttyin_ are also set. This flag is _on_ by de‐ fault. This setting is only supported by version 1.9.10 or higher. fqdn Set this flag if you want to put fully qualified host names in the _sudoers_ file when the local host name (as returned by the ‘hostname’ command) does not contain the domain name. In other words, instead of myhost you would use myhost.mydomain.edu. You may still use the short form if you wish (and even mix the two). This flag is only effective when the “canonical” host name, as returned by the [_getaddrinfo_(3)](https://www.chedong.com/phpMan.php/man/getaddrinfo/3/markdown) or [_gethostbyname_(3)](https://www.chedong.com/phpMan.php/man/gethostbyname/3/markdown) function, is a fully-qualified domain name. This is usually the case when the system is configured to use DNS for host name resolution. If the system is configured to use the _/etc/hosts_ file in preference to DNS, the “canonical” host name may not be fully-qualified. The order that sources are queried for host name resolution is usually specified in the _/etc/nsswitch.conf_, _/etc/netsvc.conf_, _/etc/host.conf_, or, in some cases, _/etc/resolv.conf_ file. In the _/etc/hosts_ file, the first host name of the entry is considered to be the “canonical” name; subsequent names are aliases that are not used by **sudoers**. For example, the following hosts file line for the machine “xyzzy” has the fully-qualified domain name as the “canonical” host name, and the short version as an alias. **192.168.1.1 xyzzy.sudo.ws xyzzy** If the machine's hosts file entry is not formatted properly, the _fqdn_ flag will not be effective if it is queried before DNS. Beware that when using DNS for host name resolution, turning on _fqdn_ re‐ quires **sudoers **to make DNS lookups which renders **sudo **unusable if DNS stops working (for example if the machine is disconnected from the network). Just like with the hosts file, you must use the “canonical” name as DNS knows it. That is, you may not use a host alias (CNAME entry) due to per‐ formance issues and the fact that there is no way to get all aliases from DNS. This flag is _on_ by default. ignore_audit_errors Allow commands to be run even if **sudoers **cannot write to the audit log. If enabled, an audit log write failure is not treated as a fatal error. If disabled, a command may only be run after the audit event is successfully written. This flag is only effective on systems for which **sudoers **supports audit logging, including FreeBSD, Linux, macOS, and Solaris. This flag is _on_ by default. ignore_dot If set, **sudo **will ignore "." or "" (both denoting the current directory) in the PATH environment variable; the PATH itself is not modified. This flag is _off_ by default. ignore_iolog_errors Allow commands to be run even if **sudoers **cannot write to the I/O log (local or remote). If enabled, an I/O log write failure is not treated as a fatal error. If disabled, the command will be terminated if the I/O log cannot be written to. This flag is _off_ by default. ignore_logfile_errors Allow commands to be run even if **sudoers **cannot write to the log file. If enabled, a log file write failure is not treated as a fatal error. If dis‐ abled, a command may only be run after the log file entry is successfully written. This flag only has an effect when **sudoers **is configured to use file-based logging via the _logfile_ setting. This flag is _on_ by default. ignore_local_sudoers If set via LDAP, parsing of _/etc/sudoers_ will be skipped. This is intended for sites that wish to prevent the usage of local sudoers files so that only LDAP is used. This thwarts the efforts of rogue operators who would attempt to add roles to _/etc/sudoers_. When this flag is enabled, _/etc/sudoers_ does not even need to exist. Since this flag tells **sudo **how to behave when no specific LDAP entries have been matched, this sudoOption is only meaningful for the ‘cn=defaults’ section. This flag is _off_ by de‐ fault. ignore_unknown_defaults If set, **sudo **will not produce a warning if it encounters an unknown De‐ faults entry in the _sudoers_ file or an unknown sudoOption in LDAP. This flag is _off_ by default. insults If set, **sudo **will insult users when they enter an incorrect password. This flag is _off_ by default. log_allowed If set, **sudoers **will log commands allowed by the policy to the system audit log (where supported) as well as to syslog and/or a log file. This flag is _on_ by default. This setting is only supported by version 1.8.29 or higher. log_denied If set, **sudoers **will log commands denied by the policy to the system audit log (where supported) as well as to syslog and/or a log file. This flag is _on_ by default. This setting is only supported by version 1.8.29 or higher. log_exit_status If set, **sudoers **will log the exit value of commands that are run to syslog and/or a log file. If a command was terminated by a signal, the signal name is logged as well. This flag is _off_ by default. This setting is only supported by version 1.9.8 or higher. log_host If set, the host name will be included in log entries written to the file configured by the _logfile_ setting. This flag is _off_ by default. log_input If set, **sudo **will run the command in a pseudo-terminal (if **sudo **was run from a terminal) and log all user input. If the standard input is not con‐ nected to the user's terminal, due to I/O redirection or because the com‐ mand is part of a pipeline, that input is also logged. For more informa‐ tion about I/O logging, see the “I/O LOGGING” section. This flag is _off_ by default. log_output If set, **sudo **will run the command in a pseudo-terminal (if **sudo **was run from a terminal) and log all output that is sent to the user's terminal, the standard output or the standard error. If the standard output or stan‐ dard error is not connected to the user's terminal, due to I/O redirection or because the command is part of a pipeline, that output is also logged. For more information about I/O logging, see the “I/O LOGGING” section. This flag is _off_ by default. log_server_keepalive If set, **sudo **will enable the TCP keepalive socket option on the connection to the log server. This enables the periodic transmission of keepalive messages to the server. If the server does not respond to a message, the connection will be closed and the running command will be terminated unless the _ignore_iolog_errors_ flag (I/O logging enabled) or the _ignore_log_errors_ flag (I/O logging disabled) is set. This flag is _on_ by default. This setting is only supported by version 1.9.0 or higher. log_server_verify If set, the server certificate received during the TLS handshake must be valid and it must contain either the server name (from _log_servers_) or its IP address. If either of these conditions is not met, the TLS handshake will fail. This flag is _on_ by default. This setting is only supported by version 1.9.0 or higher. log_stderr If set, **sudo **will log the standard error if it is not connected to the user's terminal. This can be used to log output to a pipe or redirected to a file. This flag is _off_ by default but is enabled when either the _log_output_ flag or the LOG_OUTPUT command tag is set. log_stdin If set, **sudo **will log the standard input if it is not connected to the user's terminal. This can be used to log input from a pipe or redirected from a file. This flag is _off_ by default but is enabled when either the _log_input_ flag or the LOG_INPUT command tag is set. log_stdout If set, **sudo **will log the standard output if it is not connected to the user's terminal. This can be used to log output to a pipe or redirected to a file. This flag is _off_ by default but is enabled when either the _log_output_ flag or the LOG_OUTPUT command tag is set. log_subcmds If set, **sudoers **will log when a command spawns a child process and executes a program using the [_execve_(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown), [_execl_(3)](https://www.chedong.com/phpMan.php/man/execl/3/markdown), [_execle_(3)](https://www.chedong.com/phpMan.php/man/execle/3/markdown), [_execlp_(3)](https://www.chedong.com/phpMan.php/man/execlp/3/markdown), [_execv_(3)](https://www.chedong.com/phpMan.php/man/execv/3/markdown), [_execvp_(3)](https://www.chedong.com/phpMan.php/man/execvp/3/markdown), [_execvpe_(3)](https://www.chedong.com/phpMan.php/man/execvpe/3/markdown), or [_system_(3)](https://www.chedong.com/phpMan.php/man/system/3/markdown) library functions. For example, if a shell is run by **sudo**, the individual commands run via the shell will be logged. This flag is _off_ by default. The _log_subcmds_ flag uses the same underlying mechanism as the _intercept_ setting. Some commands may not work properly when _log_subcmds_ is enabled, due to the way it intercepts sub-commands. See “Preventing shell escapes” for more information on what systems support this option and its limita‐ tions. This setting is only supported by version 1.9.8 or higher and is incompatible with SELinux RBAC support unless the system supports [_seccomp_(2)](https://www.chedong.com/phpMan.php/man/seccomp/2/markdown) filter mode. log_ttyin If set, **sudo **will run the command in a pseudo-terminal and log user key‐ strokes sent to the user's terminal, if one is present. This flag is _off_ by default but is enabled when either the _log_input_ flag or the LOG_INPUT command tag is set. If no terminal is present, for example when running a remote command using [_ssh_(1)](https://www.chedong.com/phpMan.php/man/ssh/1/markdown), this flag will have no effect. log_ttyout If set, **sudo **will run the command in a pseudo-terminal and log all output displayed on the user's terminal, if one is present. This flag is _off_ by default but is enabled when either the _log_output_ flag or the LOG_OUTPUT command tag is set. If no terminal is present, for example when running a remote command using [_ssh_(1)](https://www.chedong.com/phpMan.php/man/ssh/1/markdown), this flag will have no effect. log_year If set, the four-digit year will be logged in the (non-syslog) **sudo **log file. This flag is _off_ by default. long_otp_prompt When validating with a One Time Password (OTP) scheme such as **S/Key **or **OPIE**, a two-line prompt is used to make it easier to cut and paste the challenge to a local window. It's not as pretty as the default but some people find it more convenient. This flag is _off_ by default. mail_all_cmnds Send mail to the _mailto_ user every time a user attempts to run a command via **sudo **(this includes **sudoedit**). No mail will be sent if the user runs **sudo **with the **-l **or **-v **option unless there is an authentication error and the _mail_badpass_ flag is also set. This flag is _off_ by default. mail_always Send mail to the _mailto_ user every time a user runs **sudo**. This flag is _off_ by default. mail_badpass Send mail to the _mailto_ user if the user running **sudo **does not enter the correct password. If the command the user is attempting to run is not per‐ mitted by **sudoers **and one of the _mail_all_cmnds_, _mail_always_, _mail_no_host_, _mail_no_perms_ or _mail_no_user_ flags are set, this flag will have no effect. This flag is _off_ by default. mail_no_host If set, mail will be sent to the _mailto_ user if the invoking user exists in the _sudoers_ file, but is not allowed to run commands on the current host. This flag is _off_ by default. mail_no_perms If set, mail will be sent to the _mailto_ user if the invoking user is al‐ lowed to use **sudo **but the command they are trying is not listed in their _sudoers_ file entry or is explicitly denied. This flag is _off_ by default. mail_no_user If set, mail will be sent to the _mailto_ user if the invoking user is not in the _sudoers_ file. This flag is _on_ by default. match_group_by_gid By default, **sudoers **will look up each group the user is a member of by group-ID to determine the group name (this is only done once). The result‐ ing list of the user's group names is used when matching groups listed in the _sudoers_ file. This works well on systems where the number of groups listed in the _sudoers_ file is larger than the number of groups a typical user belongs to. On systems where group lookups are slow, where users may belong to a large number of groups, or where the number of groups listed in the _sudoers_ file is relatively small, it may be prohibitively expensive and running commands via **sudo **may take longer than normal. On such systems it may be faster to use the _match_group_by_gid_ flag to avoid resolving the user's group-IDs to group names. In this case, **sudoers **must look up any group name listed in the _sudoers_ file and use the group-ID instead of the group name when determining whether the user is a member of the group. If _match_group_by_gid_ is enabled, group database lookups performed by **sudoers **will be keyed by group name as opposed to group-ID. On systems where there are multiple sources for the group database, it is possible to have conflicting group names or group-IDs in the local _/etc/group_ file and the remote group database. On such systems, enabling or disabling _match_group_by_gid_ can be used to choose whether group database queries are performed by name (enabled) or ID (disabled), which may aid in working around group entry conflicts. The _match_group_by_gid_ flag has no effect when _sudoers_ data is stored in LDAP. This flag is _off_ by default. This setting is only supported by version 1.8.18 or higher. intercept If set, all commands run via **sudo **will behave as if the INTERCEPT tag has been set, unless overridden by an NOINTERCEPT tag. Some commands may not work properly when _intercept_ is enabled, due to the way it intercept sub- commands. See the description of INTERCEPT and NOINTERCEPT above as well as the “Preventing shell escapes” section at the end of this manual. This flag is _off_ by default. This setting is only supported by version 1.9.8 or higher and is incompati‐ ble with SELinux RBAC support unless the system supports [_seccomp_(2)](https://www.chedong.com/phpMan.php/man/seccomp/2/markdown) filter mode. intercept_allow_setid On most systems, the dynamic loader will ignore LD_PRELOAD (or the equiva‐ lent) when running set-user-ID and set-group-ID programs, effectively dis‐ abling intercept mode. To prevent this from happening, **sudoers **will not permit a set-user-ID or set-group-ID program to be run in intercept mode unless _intercept_allow_setid_ is enable. This flag has no effect unless the _intercept_ flag is enabled or the INTERCEPT tag has been set for the com‐ mand. This flag is _on_ by default when the _intercept_type_ option is set to _trace_, otherwise it default to _off_. This setting is only supported by version 1.9.8 or higher. intercept_authenticate If set, commands run by an intercepted process must be authenticated when the user's time stamp is not current. For example, if a shell is run with _intercept_ enabled, as soon as the invoking user's time stamp is out of date, subsequent commands will need to be authenticated. This flag has no effect unless the _intercept_ flag is enabled or the INTERCEPT tag has been set for the command. This flag is _off_ by default. This setting is only supported by version 1.9.8 or higher. intercept_verify If set, **sudo **will attempt to verify that a command run in intercept mode has the expected path name, command line arguments and environment. The process will be stopped after [_execve_(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown) has completed but before the new command has had a chance to run. To verify the command, **sudo **will read the command's path from _/proc/PID/exe_, the command line arguments and envi‐ ronment from the process's memory, and compare them against the arguments that were passed to [_execve_(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown). In the event of a mismatch, the command will be sent a SIGKILL signal and terminated. This can help prevent a time of check versus time of use issue with inter‐ cept mode where the [_execve_(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown) arguments could be altered after the **sudoers** policy check. The checks can only be performed if the [_proc_(5)](https://www.chedong.com/phpMan.php/man/proc/5/markdown) file system is available. This flag has no effect unless the _intercept_ flag is enabled or the INTERCEPT tag has been set for the command and the _intercept_type_ option is set to _trace_. This setting is incompatible with programs that change their root directory via [_chroot_(2)](https://www.chedong.com/phpMan.php/man/chroot/2/markdown). If a program changes its root directory, path names will no longer match those seen by the **sudo **parent process and sub-commands will be terminated before they have a chance to run. This flag is _on_ by default. This setting is only supported by version 1.9.12 or higher. netgroup_tuple If set, netgroup lookups will be performed using the full netgroup tuple: host name, user name, and domain (if one is set). Historically, **sudo **only matched the user name and domain for netgroups used in a _User_List_ and only matched the host name and domain for netgroups used in a _Host_List_. This flag is _off_ by default. noexec If set, all commands run via **sudo **will behave as if the NOEXEC tag has been set, unless overridden by an EXEC tag. See the description of EXEC and NOEXEC above as well as the “Preventing shell escapes” section at the end of this manual. This flag is _off_ by default. noninteractive_auth If set, authentication will be attempted even in non-interactive mode (when **sudo**'s **-n **option is specified). This allows authentication methods that don't require user interaction to succeed. Authentication methods that re‐ quire input from the user's terminal will still fail. If disabled, authen‐ tication will not be attempted in non-interactive mode. This flag is _off_ by default. This setting is only supported by version 1.9.10 or higher. pam_acct_mgmt On systems that use PAM for authentication, **sudo **will perform PAM account validation for the invoking user by default. The actual checks performed depend on which PAM modules are configured. If enabled, account validation will be performed regardless of whether or not a password is required. This flag is _on_ by default. This setting is only supported by version 1.8.28 or higher. pam_rhost On systems that use PAM for authentication, **sudo **will set the PAM remote host value to the name of the local host when the _pam_rhost_ flag is en‐ abled. On Linux systems, enabling _pam_rhost_ may result in DNS lookups of the local host name when PAM is initialized. On Solaris versions prior to Solaris 8, _pam_rhost_ must be enabled if _pam_ruser_ is also enabled to avoid a crash in the Solaris PAM implementation. This flag is _off_ by default on systems other than Solaris. This setting is only supported by version 1.9.0 or higher. pam_ruser On systems that use PAM for authentication, **sudo **will set the PAM remote user value to the name of the user that invoked sudo when the _pam_ruser_ flag is enabled. This flag is _on_ by default. This setting is only supported by version 1.9.0 or higher. pam_session On systems that use PAM for authentication, **sudo **will create a new PAM ses‐ sion for the command to be run in. Unless **sudo **is given the **-i **or **-s **op‐ tions, PAM session modules are run with the “silent” flag enabled. This prevents last login information from being displayed for every command on some systems. Disabling _pam_session_ may be needed on older PAM implementa‐ tions or on operating systems where opening a PAM session changes the utmp or wtmp files. If PAM session support is disabled, resource limits may not be updated for the command being run. If _pam_session_, _pam_setcred_, and _use_pty_ are disabled, _log_servers_ has not been set and I/O logging has not been configured, **sudo **will execute the command directly instead of running it as a child process. This flag is _on_ by default. This setting is only supported by version 1.8.7 or higher. pam_setcred On systems that use PAM for authentication, **sudo **will attempt to establish credentials for the target user by default, if supported by the underlying authentication system. One example of a credential is a Kerberos ticket. If _pam_session_, _pam_setcred_, and _use_pty_ are disabled, _log_servers_ has not been set and I/O logging has not been configured, **sudo **will execute the command directly instead of running it as a child process. This flag is _on_ by default. This setting is only supported by version 1.8.8 or higher. passprompt_override If set, the prompt specified by _passprompt_ or the SUDO_PROMPT environment variable will always be used and will replace the prompt provided by a PAM module or other authentication method. This flag is _off_ by default. path_info Normally, **sudo **will tell the user when a command could not be found in their PATH environment variable. Some sites may wish to disable this as it could be used to gather information on the location of executables that the normal user does not have access to. The disadvantage is that if the exe‐ cutable is simply not in the user's PATH, **sudo **will tell the user that they are not allowed to run it, which can be confusing. This flag is _on_ by de‐ fault. preserve_groups By default, **sudo **will initialize the group vector to the list of groups the target user is in. When _preserve_groups_ is set, the user's existing group vector is left unaltered. The real and effective group-IDs, however, are still set to match the target user. This flag is _off_ by default. pwfeedback By default, **sudo **reads the password like most other Unix programs, by turn‐ ing off echo until the user hits the return (or enter) key. Some users be‐ come confused by this as it appears to them that **sudo **has hung at this point. When _pwfeedback_ is set, **sudo **will provide visual feedback when the user presses a key. This does have a security impact as an onlooker may be able to determine the length of the password being entered. This flag is _off_ by default. requiretty If set, **sudo **will only run when the user is logged in to a real tty. When this flag is set, **sudo **can only be run from a login session and not via other means such as [_cron_(8)](https://www.chedong.com/phpMan.php/man/cron/8/markdown) or cgi-bin scripts. This flag is _off_ by de‐ fault. root_sudo If set, **root **is allowed to run **sudo **too. Disabling this prevents users from “chaining” **sudo **commands to get a **root **shell by doing something like ‘sudo sudo /bin/sh’. Note, however, that turning off _root_sudo_ will also prevent **root **from running **sudoedit**. Disabling _root_sudo_ provides no real additional security; it exists purely for historical reasons. This flag is _on_ by default. rootpw If set, **sudo **will prompt for the **root **password instead of the password of the invoking user when running a command or editing a file. This flag is _off_ by default. runas_allow_unknown_id If enabled, allow matching of runas user and group IDs that are not present in the password or group databases. In addition to explicitly matching un‐ known user or group IDs in a _Runas_List_, this option also allows the **ALL** alias to match unknown IDs. This flag is _off_ by default. This setting is only supported by version 1.8.30 or higher. Older versions of **sudo **always allowed matching of unknown user and group IDs. runas_check_shell If enabled, **sudo **will only run commands as a user whose shell appears in the _/etc/shells_ file, even if the invoking user's _Runas_List_ would other‐ wise permit it. If no _/etc/shells_ file is present, a system-dependent list of built-in default shells is used. On many operating systems, system users such as “bin”, do not have a valid shell and this flag can be used to prevent commands from being run as those users. This flag is _off_ by de‐ fault. This setting is only supported by version 1.8.30 or higher. runaspw If set, **sudo **will prompt for the password of the user defined by the _runas_default_ option (defaults to **root**) instead of the password of the in‐ voking user when running a command or editing a file. This flag is _off_ by default. selinux If enabled, the user may specify an SELinux role and/or type to use when running the command, as permitted by the SELinux policy. If SELinux is disabled on the system, this flag has no effect. This flag is _on_ by de‐ fault. set_home If enabled and **sudo **is invoked with the **-s **option, the HOME environment variable will be set to the home directory of the target user (which is the _runas_default_ user unless the **-u **option is used). This flag is largely ob‐ solete and has no effect unless the _env_reset_ flag has been disabled or HOME is present in the _env_keep_ list, both of which are strongly discour‐ aged. This flag is _off_ by default. set_logname Normally, **sudo **will set the LOGNAME and USER environment variables to the name of the target user (the user specified by _runas_default_ unless the **-u** option is given). However, since some programs (including the RCS revision control system) use LOGNAME to determine the real identity of the user, it may be desirable to change this behavior. This can be done by negating the set_logname option. The _set_logname_ option will have no effect if the _env_reset_ option has not been disabled and the _env_keep_ list contains LOGNAME or USER. This flag is _on_ by default. set_utmp When enabled, **sudo **will create an entry in the utmp (or utmpx) file when a pseudo-terminal is allocated. A pseudo-terminal is allocated by **sudo **when it is running in a terminal and one or more of the _log_input_, _log_output_, _log_stdin_, _log_stdout_, _log_stderr_, _log_ttyin_, _log_ttyout_, or _use_pty_ flags is enabled. By default, the new entry will be a copy of the user's exist‐ ing utmp entry (if any), with the tty, time, type, and pid fields updated. This flag is _on_ by default. setenv Allow the user to disable the _env_reset_ option from the command line via the **-E **option. Additionally, environment variables set via the command line are not subject to the restrictions imposed by _env_check_, _env_delete_, or _env_keep_. As such, only trusted users should be allowed to set vari‐ ables in this manner. This flag is _off_ by default. shell_noargs If set and **sudo **is invoked with no arguments it acts as if the **-s **option had been given. That is, it runs a shell as **root **(the shell is determined by the SHELL environment variable if it is set, falling back on the shell listed in the invoking user's /etc/passwd entry if not). This flag is _off_ by default. stay_setuid Normally, when **sudo **executes a command the real and effective user-IDs are set to the target user (**root **by default). This option changes that behav‐ ior such that the real user-ID is left as the invoking user's user-ID. In other words, this makes **sudo **act as a set-user-ID wrapper. This can be useful on systems that disable some potentially dangerous functionality when a program is run set-user-ID. This option is only effective on sys‐ tems that support either the [_setreuid_(2)](https://www.chedong.com/phpMan.php/man/setreuid/2/markdown) or [_setresuid_(2)](https://www.chedong.com/phpMan.php/man/setresuid/2/markdown) system call. This flag is _off_ by default. sudoedit_checkdir If set, **sudoedit **will check all directory components of the path to be edited for writability by the invoking user. Symbolic links will not be followed in writable directories and **sudoedit **will refuse to edit a file located in a writable directory. These restrictions are not enforced when **sudoedit **is run by **root**. On some systems, if all directory components of the path to be edited are not readable by the target user, **sudoedit **will be unable to edit the file. This flag is _on_ by default. This setting was first introduced in version 1.8.15 but initially suffered from a race condition. The check for symbolic links in writable intermedi‐ ate directories was added in version 1.8.16. sudoedit_follow By default, **sudoedit **will not follow symbolic links when opening files. The _sudoedit_follow_ option can be enabled to allow **sudoedit **to open sym‐ bolic links. It may be overridden on a per-command basis by the FOLLOW and NOFOLLOW tags. This flag is _off_ by default. This setting is only supported by version 1.8.15 or higher. syslog_pid When logging via [_syslog_(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown), include the process ID in the log entry. This flag is _off_ by default. This setting is only supported by version 1.8.21 or higher. targetpw If set, **sudo **will prompt for the password of the user specified by the **-u** option (defaults to the value of _runas_default_) instead of the password of the invoking user when running a command or editing a file. This flag pre‐ cludes the use of a user-ID not listed in the passwd database as an argu‐ ment to the **-u **option. This flag is _off_ by default. tty_tickets If set, users must authenticate on a per-tty basis. With this flag en‐ abled, **sudo **will use a separate record in the time stamp file for each ter‐ minal. If disabled, a single record is used for all login sessions. This option has been superseded by the _timestamp_type_ option. umask_override If set, **sudo **will set the umask as specified in the _sudoers_ file without modification. This makes it possible to specify a umask in the _sudoers_ file that is more permissive than the user's own umask and matches histori‐ cal behavior. If _umask_override_ is not set, **sudo **will set the umask to be the union of the user's umask and what is specified in _sudoers_. This flag is _off_ by default. use_netgroups If set, netgroups (prefixed with ‘+’), may be used in place of a user or host. For LDAP-based sudoers, netgroup support requires an expensive sub- string match on the server unless the **NETGROUP_BASE **directive is present in the _/etc/ldap.conf_ file. If netgroups are not needed, this option can be disabled to reduce the load on the LDAP server. This flag is _on_ by de‐ fault. use_pty If set, and **sudo **is running in a terminal, the command will be run in a new pseudo-terminal. If the **sudo **process is not attached to a terminal, _use_pty_ has no effect. A malicious program run under **sudo **may be capable of injecting commands into the user's terminal or running a background process that retains ac‐ cess to the user's terminal device even after the main program has finished executing. By running the command in a separate pseudo-terminal, this at‐ tack is no longer possible. This flag is _on_ by default for **sudo **1.9.14 and above. user_command_timeouts If set, the user may specify a timeout on the command line. If the timeout expires before the command has exited, the command will be terminated. If a timeout is specified both in the _sudoers_ file and on the command line, the smaller of the two timeouts will be used. See the _Timeout_Spec_ section for a description of the timeout syntax. This flag is _off_ by default. This setting is only supported by version 1.8.20 or higher. utmp_runas If set, **sudo **will store the name of the runas user when updating the utmp (or utmpx) file. By default, **sudo **stores the name of the invoking user. This flag is _off_ by default. visiblepw By default, **sudo **will refuse to run if the user must enter a password but it is not possible to disable echo on the terminal. If the _visiblepw_ flag is set, **sudo **will prompt for a password even when it would be visible on the screen. This makes it possible to run things like ‘ssh somehost sudo ls’ since by default, [_ssh_(1)](https://www.chedong.com/phpMan.php/man/ssh/1/markdown) does not allocate a tty when running a com‐ mand. This flag is _off_ by default. **Integers**: closefrom Before it executes a command, **sudo **will close all open file descriptors other than standard input, standard output, and standard error (file de‐ scriptors 0-2). The _closefrom_ option can be used to specify a different file descriptor at which to start closing. The default is 3. command_timeout The maximum amount of time a command is allowed to run before it is termi‐ nated. See the _Timeout_Spec_ section for a description of the timeout syn‐ tax. This setting is only supported by version 1.8.20 or higher. log_server_timeout The maximum amount of time to wait when connecting to a log server or wait‐ ing for a server response. See the _Timeout_Spec_ section for a description of the timeout syntax. The default value is 30 seconds. This setting is only supported by version 1.9.0 or higher. maxseq The maximum sequence number that will be substituted for the ‘%{seq}’ es‐ cape in the I/O log file (see the _iolog_dir_ description below for more in‐ formation). While the value substituted for ‘%{seq}’ is in base 36, _maxseq_ itself should be expressed in decimal. Values larger than 2176782336 (which corresponds to the base 36 sequence number “ZZZZZZ”) will be silently truncated to 2176782336. The default value is 2176782336. Once the local sequence number reaches the value of _maxseq_, it will “roll over” to zero, after which **sudoers **will truncate and re-use any existing I/O log path names. This setting is only supported by version 1.8.7 or higher. passwd_tries The number of tries a user gets to enter his/her password before **sudo **logs the failure and exits. The default is 3. syslog_maxlen On many systems, [_syslog_(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown) has a relatively small log buffer. IETF RFC 5424 states that syslog servers must support messages of at least 480 bytes and should support messages up to 2048 bytes. By default, **sudoers **creates log messages up to 980 bytes which corresponds to the historic BSD syslog implementation which used a 1024 byte buffer to store the message, date, hostname, and program name. To prevent syslog messages from being trun‐ cated, **sudoers **will split up log messages that are larger than _syslog_maxlen_ bytes. When a message is split, additional parts will in‐ clude the string “(command continued)” after the user name and before the continued command line arguments. This setting is only supported by version 1.8.19 or higher. **Integers that can be used in a boolean context**: loglinelen Number of characters per line for the file log. This value is used to de‐ cide when to wrap lines for nicer log files. This has no effect on the syslog log file, only the file log. The default is 80 (use 0 or negate the option to disable word wrap). passwd_timeout Number of minutes before the **sudo **password prompt times out, or 0 for no timeout. The timeout may include a fractional component if minute granu‐ larity is insufficient, for example 2.5. The default is 0. timestamp_timeout Number of minutes that can elapse before **sudo **will ask for a password again. The timeout may include a fractional component if minute granular‐ ity is insufficient, for example 2.5. The default is 15. Set this to 0 to always prompt for a password. If set to a value less than 0 the user's time stamp will not expire until the system is rebooted. This can be used to allow users to create or delete their own time stamps via ‘sudo -v’ and ‘sudo -k’ respectively. umask File mode creation mask to use when running the command. Negate this op‐ tion or set it to 0777 to prevent **sudoers **from changing the umask. Unless the _umask_override_ flag is set, the actual umask will be the union of the user's umask and the value of the _umask_ setting, which defaults to 0022. This guarantees that **sudo **never lowers the umask when running a command. If _umask_ is explicitly set in _sudoers_, it will override any umask setting in PAM or login.conf. If _umask_ is not set in _sudoers_, the umask specified by PAM or login.conf will take precedence. The umask setting in PAM is not used for **sudoedit**, which does not create a new PAM session. **Strings**: apparmor_profile The default AppArmor profile to transition into when executing the command. The default _apparmor_profile_ can be overridden for individual _sudoers_ en‐ tries by specifying the APPARMOR_PROFILE option. This option is only available when sudo is built with AppArmor support. authfail_message Message that is displayed after a user fails to authenticate. The message may include the ‘%d’ escape which will expand to the number of failed pass‐ word attempts. If set, it overrides the default message, “%d incorrect password attempt(s)”. badpass_message Message that is displayed if a user enters an incorrect password. The de‐ fault is “Sorry, try again.” unless insults are enabled. editor A colon (‘:’) separated list of editor path names used by **sudoedit **and **visudo**. For **sudoedit**, this list is used to find an editor when none of the SUDO_EDITOR, VISUAL or EDITOR environment variables are set to an editor that exists and is executable. For **visudo**, it is used as a white list of allowed editors; **visudo **will choose the editor that matches the user's SUDO_EDITOR, VISUAL or EDITOR environment variable if possible, or the first editor in the list that exists and is executable if not. Unless in‐ voked as **sudoedit**, **sudo **does not preserve the SUDO_EDITOR, VISUAL or EDITOR environment variables unless they are present in the _env_keep_ list or the _env_reset_ option is disabled. The default is _/usr/bin/editor_. intercept_type The underlying mechanism used by the _intercept_ and _log_subcmds_ options. It has the following possible values: dso Preload a dynamic shared object (shared library) that intercepts the [_execve_(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown), [_execl_(3)](https://www.chedong.com/phpMan.php/man/execl/3/markdown), [_execle_(3)](https://www.chedong.com/phpMan.php/man/execle/3/markdown), [_execlp_(3)](https://www.chedong.com/phpMan.php/man/execlp/3/markdown), [_execv_(3)](https://www.chedong.com/phpMan.php/man/execv/3/markdown), [_execvp_(3)](https://www.chedong.com/phpMan.php/man/execvp/3/markdown), [_execvpe_(3)](https://www.chedong.com/phpMan.php/man/execvpe/3/markdown), and [_system_(3)](https://www.chedong.com/phpMan.php/man/system/3/markdown) library functions. A value of _dso_ is in‐ compatible with **sudo**'s SELinux RBAC support. trace Use [_ptrace_(2)](https://www.chedong.com/phpMan.php/man/ptrace/2/markdown) to intercept the [_execve_(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown) system call. This is only supported on Linux systems where [_seccomp_(2)](https://www.chedong.com/phpMan.php/man/seccomp/2/markdown) filtering is enabled. If the _/proc/sys/kernel/seccomp/actions_avail_ file is missing or does not contain a “trap” element, setting _intercept_type_ to _trace_ will have no effect and _dso_ will be used instead. The default is to use _trace_ if it is supported by the system and _dso_ if it is not. iolog_dir The top-level directory to use when constructing the path name for the in‐ put/output log directory. Only used if the _log_input_ or _log_output_ options are enabled or when the LOG_INPUT or LOG_OUTPUT tags are present for a com‐ mand. The session sequence number, if any, is stored in the directory. The default is _/var/log/sudo-io_. The following percent (‘%’) escape sequences are supported: %{seq} expanded to a monotonically increasing base-36 sequence number, such as 0100A5, where every two digits are used to form a new directory, e.g., _01/00/A5_ %{user} expanded to the invoking user's login name %{group} expanded to the name of the invoking user's real group-ID %{runas_user} expanded to the login name of the user the command will be run as (e.g., **root**) %{runas_group} expanded to the group name of the user the command will be run as (e.g., **wheel**) %{hostname} expanded to the local host name without the domain name %{command} expanded to the base name of the command being run In addition, any escape sequences supported by the system's [_strftime_(3)](https://www.chedong.com/phpMan.php/man/strftime/3/markdown) function will be expanded. To include a literal ‘%’ character, the string ‘%%’ should be used. Any path name separator characters (‘/’) present in the user, group or host name will be replaced with an underbar (‘_’) during expansion. iolog_file The path name, relative to _iolog_dir_, in which to store input/output logs when the _log_input_ or _log_output_ options are enabled or when the LOG_INPUT or LOG_OUTPUT tags are present for a command. _iolog_file_ may contain di‐ rectory components. The default is ‘%{seq}’. See the _iolog_dir_ option above for a list of supported percent (‘%’) escape sequences. In addition to the escape sequences, path names that end in six or more _X_s will have the _X_s replaced with a unique combination of digits and letters, similar to the [_mktemp_(3)](https://www.chedong.com/phpMan.php/man/mktemp/3/markdown) function. If the path created by concatenating _iolog_dir_ and _iolog_file_ already ex‐ ists, the existing I/O log file will be truncated and overwritten unless _iolog_file_ ends in six or more _X_s. iolog_flush If set, **sudo **will flush I/O log data to disk after each write instead of buffering it. This makes it possible to view the logs in real-time as the program is executing but may significantly reduce the effectiveness of I/O log compression. This flag is _off_ by default. This setting is only supported by version 1.8.20 or higher. iolog_group The group name to look up when setting the group-ID on new I/O log files and directories. If _iolog_group_ is not set, the primary group-ID of the user specified by _iolog_user_ is used. If neither _iolog_group_ nor _iolog_user_ are set, I/O log files and directories are created with group-ID 0. This setting is only supported by version 1.8.19 or higher. iolog_mode The file mode to use when creating I/O log files. Mode bits for read and write permissions for owner, group, or other are honored, everything else is ignored. The file permissions will always include the owner read and write bits, even if they are not present in the specified mode. When cre‐ ating I/O log directories, search (execute) bits are added to match the read and write bits specified by _iolog_mode_. Defaults to 0600 (read and write by user only). This setting is only supported by version 1.8.19 or higher. iolog_user The user name to look up when setting the user and group-IDs on new I/O log files and directories. If _iolog_group_ is set, it will be used instead of the user's primary group-ID. By default, I/O log files and directories are created with user and group-ID 0. This setting can be useful when the I/O logs are stored on a Network File System (NFS) share. Having a dedicated user own the I/O log files means that **sudoers **does not write to the log files as user-ID 0, which is usually not permitted by NFS. This setting is only supported by version 1.8.19 or higher. lecture_status_dir The directory in which **sudo **stores per-user lecture status files. Once a user has received the lecture, a zero-length file is created in this direc‐ tory so that **sudo **will not lecture the user again. This directory should _not_ be cleared when the system reboots. The default is _/var/lib/sudo/lectured_. log_server_cabundle The path to a certificate authority bundle file, in PEM format, to use in‐ stead of the system's default certificate authority database when authenti‐ cating the log server. The default is to use the system's default certifi‐ cate authority database. This setting has no effect unless _log_servers_ is set and the remote log server is secured with TLS. This setting is only supported by version 1.9.0 or higher. log_server_peer_cert The path to the **sudo **client's certificate file, in PEM format. This set‐ ting is required when the remote log server is secured with TLS and client certificate validation is enabled. For **sudo_logsrvd**, client certificate validation is controlled by the _tls_checkpeer_ option, which defaults to _false_. This setting is only supported by version 1.9.0 or higher. log_server_peer_key The path to the **sudo **client's private key file, in PEM format. This set‐ ting is required when the remote log server is secured with TLS and client certificate validation is enabled. For **sudo_logsrvd**, client certificate validation is controlled by the _tls_checkpeer_ flag, which defaults to _false_. This setting is only supported by version 1.9.0 or higher. mailsub Subject of the mail sent to the _mailto_ user. The escape ‘%h’ will expand to the host name of the machine. Default is “*** SECURITY information for %h ***”. noexec_file As of **sudo **version 1.8.1 this option is no longer supported. The path to the noexec file should now be set in the [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) file. pam_askpass_service On systems that use PAM for authentication, this is the service name used when the **-A **option is specified. The default value is either ‘sudo’ or ‘sudo-i’, depending on whether or not the **-i **option is also specified. See the description of _pam_service_ for more information. This setting is only supported by version 1.9.9 or higher. pam_login_service On systems that use PAM for authentication, this is the service name used when the **-i **option is specified. The default value is ‘sudo-i’. See the description of _pam_service_ for more information. This setting is only supported by version 1.8.8 or higher. pam_service On systems that use PAM for authentication, the service name specifies the PAM policy to apply. This usually corresponds to an entry in the _pam.conf_ file or a file in the _/etc/pam.d_ directory. The default value is ‘sudo’. This setting is only supported by version 1.8.8 or higher. passprompt The default prompt to use when asking for a password; can be overridden via the **-p **option or the SUDO_PROMPT environment variable. The following per‐ cent (‘%’) escape sequences are supported: %H expanded to the local host name including the domain name (only if the machine's host name is fully qualified or the _fqdn_ option is set) %h expanded to the local host name without the domain name %p expanded to the user whose password is being asked for (respects the _rootpw_, _targetpw_ and _runaspw_ flags in _sudoers_) %U expanded to the login name of the user the command will be run as (defaults to **root**) %u expanded to the invoking user's login name %% two consecutive ‘%’ characters are collapsed into a single ‘%’ char‐ acter On systems that use PAM for authentication, _passprompt_ will only be used if the prompt provided by the PAM module matches the string “Password: ” or “username's Password: ”. This ensures that the _passprompt_ setting does not interfere with challenge-response style authentication. The _passprompt_override_ flag can be used to change this behavior. The default value is ‘[sudo] password for %p: ’. role The default SELinux role to use when constructing a new security context to run the command. The default role may be overridden on a per-command basis in the _sudoers_ file or via command line options. This option is only available when **sudo **is built with SELinux support. runas_default The default user to run commands as if the **-u **option is not specified on the command line. This defaults to **root**. sudoers_locale Locale to use when parsing the sudoers file, logging commands, and sending email. Changing the locale may affect how sudoers is interpreted. De‐ faults to ‘C’. timestamp_type **sudoers **uses per-user time stamp files for credential caching. The _timestamp_type_ option can be used to specify the type of time stamp record used. It has the following possible values: global A single time stamp record is used for all of a user's login ses‐ sions, regardless of the terminal or parent process ID. An addi‐ tional record is used to serialize password prompts when **sudo **is used multiple times in a pipeline, but this does not affect authen‐ tication. ppid A single time stamp record is used for all processes with the same parent process ID (usually the shell). Commands run from the same shell (or other common parent process) will not require a password for _timestamp_timeout_ minutes (15 by default). Commands run via **sudo **with a different parent process ID, for example from a shell script, will be authenticated separately. tty One time stamp record is used for each terminal, which means that a user's login sessions are authenticated separately. If no terminal is present, the behavior is the same as _ppid_. Commands run from the same terminal will not require a password for _timestamp_timeout_ minutes (15 by default). kernel The time stamp is stored in the kernel as an attribute of the ter‐ minal device. If no terminal is present, the behavior is the same as _ppid_. Negative _timestamp_timeout_ values are not supported and positive values are limited to a maximum of 60 minutes. This is currently only supported on OpenBSD. The default value is _tty_. This setting is only supported by version 1.8.21 or higher. timestampdir The directory in which **sudo **stores its time stamp files. This directory should be cleared when the system reboots. The default is _/run/sudo/ts_. timestampowner The owner of the lecture status directory, time stamp directory and all files stored therein. The default is **root**. type The default SELinux type to use when constructing a new security context to run the command. The default type may be overridden on a per-command basis in the _sudoers_ file or via command line options. This option is only available when **sudo **is built with SELinux support. **Strings that can be used in a boolean context**: admin_flag The _admin_flag_ option specifies the path to a file that is created the first time a user that is a member of the _sudo_ or _admin_ groups runs **sudo**. Only available if **sudo **is configured with the **--enable-admin-flag **option. The de‐ fault value is _~/.sudo_as_admin_successful_. env_file The _env_file_ option specifies the fully qualified path to a file containing variables to be set in the environment of the program being run. Entries in this file should either be of the form ‘VARIABLE=value’ or ‘export VARIABLE=value’. The value may optionally be enclosed in single or double quotes. Variables in this file are only added if the variable does not already exist in the environment. This file is considered to be part of the security policy, its contents are not subject to other **sudo **environment restrictions such as _env_keep_ and _env_check_. exempt_group Users in this group are exempt from password and PATH requirements. The group name specified should not include a ‘%’ prefix. This is not set by default. fdexec Determines whether **sudo **will execute a command by its path or by an open file descriptor. It has the following possible values: always Always execute by file descriptor. never Never execute by file descriptor. digest_only Only execute by file descriptor if the command has an associated digest in the _sudoers_ file. The default value is _digest_only_. This avoids a time of check versus time of use race condition when the command is located in a directory writable by the invoking user. _fdexec_ will change the first element of the argument vector for scripts ($0 in the shell) due to the way the kernel runs script interpreters. Instead of be‐ ing a normal path, it will refer to a file descriptor. For example, _/dev/fd/4_ on Solaris and _/proc/self/fd/4_ on Linux. A workaround is to use the SUDO_COMMAND environment variable instead. The _fdexec_ setting is only used when the command is matched by path name. It has no effect if the command is matched by the built-in **ALL **alias. This setting is only supported by version 1.8.20 or higher. If the operating system does not support the [_fexecve_(2)](https://www.chedong.com/phpMan.php/man/fexecve/2/markdown) system call, this setting has no effect. group_plugin A string containing a **sudoers **group plugin with optional arguments. The string should consist of the plugin path, either fully-qualified or relative to the _/usr/libexec/sudo_ directory, followed by any configuration arguments the plugin requires. These arguments (if any) will be passed to the plugin's initializa‐ tion function. If arguments are present, the string must be enclosed in double quotes (""). On 64-bit systems, if the plugin is present but cannot be loaded, **sudoers **will look for a 64-bit version and, if it exists, load that as a fallback. The ex‐ act rules for this vary by system. On Solaris, if the plugin is stored in a directory ending in “lib”, **sudoers **will create a fallback path by appending “/64” to the directory name; _/usr/lib/group_plugin.so_ becomes _/usr/lib/64/group_plugin.so_. On Linux, a directory ending in “lib” will be transformed to “lib64” as the fallback path; _/usr/lib/group_plugin.so_ becomes _/usr/lib64/group_plugin.so_. On all other systems, the fallback path is gener‐ ated by adding a “64” before the file extension; _group_plugin.so_ becomes _group_plugin64.so_. On AIX systems, the plugin may be either a shared object ending in ‘.so’ or an archive file containing a shared object ending in ‘.a’ with the name of the shared object in parentheses at the end. For more information see “GROUP PROVIDER PLUGINS”. lecture This option controls when a short lecture will be printed along with the pass‐ word prompt. It has the following possible values: always Always lecture the user. never Never lecture the user. once Only lecture the user the first time they run **sudo**. If no value is specified, a value of _once_ is implied. Negating the option re‐ sults in a value of _never_ being used. The default value is _never_. lecture_file Path to a file containing an alternate **sudo **lecture that will be used in place of the standard lecture if the named file exists. By default, **sudo **uses a built-in lecture. listpw This option controls when a password will be required when a user runs **sudo** with the **-l **option. It has the following possible values: all All the user's _sudoers_ file entries for the current host must have the NOPASSWD flag set to avoid entering a password. always The user must always enter a password to use the **-l **option. any At least one of the user's _sudoers_ file entries for the current host must have the NOPASSWD flag set to avoid entering a password. never The user need never enter a password to use the **-l **option. If no value is specified, a value of _any_ is implied. Negating the option re‐ sults in a value of _never_ being used. The default value is _any_. log_format The event log format. Supported log formats are: json Logs in JSON format. JSON log entries contain the full user details as well as the execution environment if the command was allowed. Due to limitations of the protocol, JSON events sent via _syslog_ may be trun‐ cated. sudo Traditional sudo-style logs, see “EVENT LOGGING” for a description of the log file format. This setting affects logs sent via [_syslog_(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown) as well as the file specified by the _logfile_ setting, if any. The default value is _sudo_. logfile Path to the **sudo **log file (not the syslog log file). Setting a path turns on logging to a file; negating this option turns it off. By default, **sudo **logs via syslog. mailerflags Flags to use when invoking mailer. Defaults to **-t**. mailerpath Path to mail program used to send warning mail (negate to prevent **sudo **from sending mail). Defaults to the path to sendmail found at configure time. mailfrom Address to use for the “from” address when sending warning and error mail. The address should be enclosed in double quotes ("") to protect against **sudo **inter‐ preting the ‘@’ sign. Defaults to the name of the user running **sudo**. mailto Address to send warning and error mail to (negate to prevent **sudo **from sending mail). The address should be enclosed in double quotes ("") to protect against **sudo **interpreting the ‘@’ sign. Defaults to root. rlimit_as The maximum size to which the process's address space may grow (in bytes), if supported by the operating system. See “Resource limits” for more information. rlimit_core The largest size core dump file that may be created (in bytes). See “Resource limits” for more information. Defaults to 0 (no core dump created). rlimit_cpu The maximum amount of CPU time that the process may use (in seconds). See “Resource limits” for more information. rlimit_data The maximum size of the data segment for the process (in bytes). See “Resource limits” for more information. rlimit_fsize The largest size file that the process may create (in bytes). See “Resource limits” for more information. rlimit_locks The maximum number of locks that the process may establish, if supported by the operating system. See “Resource limits” for more information. rlimit_memlock The maximum size that the process may lock in memory (in bytes), if supported by the operating system. See “Resource limits” for more information. rlimit_nofile The maximum number of files that the process may have open. See “Resource limits” for more information. rlimit_nproc The maximum number of processes that the user may run simultaneously. See “Resource limits” for more information. rlimit_rss The maximum size to which the process's resident set size may grow (in bytes). See “Resource limits” for more information. rlimit_stack The maximum size to which the process's stack may grow (in bytes). See “Resource limits” for more information. restricted_env_file The _restricted_env_file_ option specifies the fully qualified path to a file containing variables to be set in the environment of the program being run. Entries in this file should either be of the form ‘VARIABLE=value’ or ‘export VARIABLE=value’. The value may optionally be enclosed in single or double quotes. Variables in this file are only added if the variable does not already exist in the environment. Unlike _env_file_, the file's contents are not trusted and are processed in a manner similar to that of the invoking user's environ‐ ment. If _env_reset_ is enabled, variables in the file will only be added if they are matched by either the _env_check_ or _env_keep_ list. If _env_reset_ is disabled, variables in the file are added as long as they are not matched by the _env_delete_ list. In either case, the contents of _restricted_env_file_ are processed before the contents of _env_file_. runchroot If set, **sudo **will use this value for the root directory when running a command. The special value “*” will allow the user to specify the root directory via **sudo**'s **-R **option. See the “Chroot_Spec” section for more details. It is only possible to use _runchroot_ as a command-specific Defaults setting if the command exists with the same path both inside and outside the chroot jail. This restriction does not apply to global, host, or user-based Defaults set‐ tings or to a _Cmnd_Spec_ that includes a _Chroot_Spec_. This setting is only supported by version 1.9.3 or higher. runcwd If set, **sudo **will use this value for the working directory when running a com‐ mand. The special value “*” will allow the user to specify the working direc‐ tory via **sudo**'s **-D **option. See the “Chdir_Spec” section for more details. This setting is only supported by version 1.9.3 or higher. secure_path If set, **sudo **will use this value in place of the user's PATH environment vari‐ able. This option can be used to reset the PATH to a known good value that contains directories for system administrator commands such as _/usr/sbin_. Users in the group specified by the _exempt_group_ option are not affected by _secure_path_. This option is not set by default. syslog Syslog facility if syslog is being used for logging (negate to disable syslog logging). Defaults to authpriv. The following syslog facilities are supported: **authpriv **(if your OS supports it), **auth**, **daemon**, **user**, **local0**, **local1**, **local2**, **local3**, **local4**, **local5**, **local6**, and **local7**. syslog_badpri Syslog priority to use when the user is not allowed to run a command or when authentication is unsuccessful. Defaults to alert. The following syslog priorities are supported: **alert**, **crit**, **debug**, **emerg**, **err**, **info**, **notice**, **warning**, and **none**. Negating the option or setting it to a value of **none **will disable logging of unsuccessful commands. syslog_goodpri Syslog priority to use when the user is allowed to run a command and authenti‐ cation is successful. Defaults to notice. See _syslog_badpri_ for the list of supported syslog priorities. Negating the option or setting it to a value of **none **will disable logging of successful com‐ mands. verifypw This option controls when a password will be required when a user runs **sudo** with the **-v **option. It has the following possible values: all All the user's _sudoers_ file entries for the current host must have the NOPASSWD flag set to avoid entering a password. always The user must always enter a password to use the **-v **option. any At least one of the user's _sudoers_ file entries for the current host must have the NOPASSWD flag set to avoid entering a password. never The user need never enter a password to use the **-v **option. If no value is specified, a value of _all_ is implied. Negating the option re‐ sults in a value of _never_ being used. The default value is _all_. **Lists that can be used in a boolean context**: env_check Environment variables to be removed from the user's environment unless they are considered “safe”. For all variables except TZ, “safe” means that the variable's value does not contain any ‘%’ or ‘/’ characters. This can be used to guard against printf-style format vulnerabilities in poorly-written programs. The TZ variable is considered unsafe if any of the following are true: **• **It consists of a fully-qualified path name, optionally prefixed with a colon (‘:’), that does not match the location of the _zoneinfo_ directory. **• **It contains a _.._ path element. **• **It contains white space or non-printable characters. **• **It is longer than the value of PATH_MAX. The argument may be a double-quoted, space-separated list or a single value without double-quotes. The list can be replaced, added to, deleted from, or disabled by using the ‘=’, ‘+=’, ‘-=’, and ‘!’ operators respectively. Regardless of whether the _env_reset_ option is enabled or disabled, vari‐ ables specified by _env_check_ will be preserved in the environment if they pass the aforementioned check. The global list of environment variables to check is displayed when **sudo **is run by **root **with the **-V **option. env_delete Environment variables to be removed from the user's environment when the _env_reset_ option is not in effect. The argument may be a double-quoted, space-separated list or a single value without double-quotes. The list can be replaced, added to, deleted from, or disabled by using the ‘=’, ‘+=’, ‘-=’, and ‘!’ operators respectively. The global list of environment vari‐ ables to remove is displayed when **sudo **is run by **root **with the **-V **option. Many operating systems will remove potentially dangerous variables from the environment of any set-user-ID process (such as **sudo**). env_keep Environment variables to be preserved in the user's environment when the _env_reset_ option is in effect. This allows fine-grained control over the environment **sudo**-spawned processes will receive. The argument may be a double-quoted, space-separated list or a single value without double- quotes. The list can be replaced, added to, deleted from, or disabled by using the ‘=’, ‘+=’, ‘-=’, and ‘!’ operators respectively. The global list of variables to keep is displayed when **sudo **is run by **root **with the **-V **op‐ tion. Preserving the HOME environment variable has security implications since many programs use it when searching for configuration or data files. Adding HOME to _env_keep_ may enable a user to run unrestricted commands via **sudo **and is strongly discouraged. Users wishing to edit files with **sudo** should run **sudoedit **(or **sudo -e**) to get their accustomed editor configura‐ tion instead of invoking the editor directly. log_servers A list of one or more servers to use for remote event and I/O log storage, separated by white space. Log servers must be running **sudo_logsrvd **or an‐ other service that implements the protocol described by [_sudo_logsrv.proto_(5)](https://www.chedong.com/phpMan.php/man/sudologsrv.proto/5/markdown). Server addresses should be of the form “host[:port][(tls)]”. The host por‐ tion may be a host name, an IPv4 address, or an IPv6 address in square brackets. If the optional _tls_ flag is present, the connection will be secured with Transport Layer Security (TLS) version 1.2 or 1.3. Versions of TLS prior to 1.2 are not supported. If a port is specified, it may either be a port number or a well-known ser‐ vice name as defined by the system service name database. If no port is specified, port 30343 will be used for plaintext connections and port 30344 will be used for TLS connections. When _log_servers_ is set, event log data will be logged both locally (see the _syslog_ and _log_file_ settings) as well as remotely, but I/O log data will only be logged remotely. If multiple hosts are specified, they will be attempted in reverse order. If no log servers are available, the user will not be able to run a command unless either the _ignore_iolog_errors_ flag (I/O logging enabled) or the _ignore_log_errors_ flag (I/O logging dis‐ abled) is set. Likewise, if the connection to the log server is inter‐ rupted while **sudo **is running, the command will be terminated unless the _ignore_iolog_errors_ flag (I/O logging enabled) or the _ignore_log_errors_ flag (I/O logging disabled) is set. This setting is only supported by version 1.9.0 or higher. passprompt_regex A list of POSIX extended regular expressions used to match password prompts in the terminal output. As an extension, if the regular expression begins with “(?i)”, it will be matched in a case-insensitive manner. Each regular expression is limited to 1024 characters. This option is only used when _log_passwords_ has been disabled. The default value is “[Pp]assword[: ]*” This setting is only supported by version 1.9.10 or higher. ## GROUP PROVIDER PLUGINS The **sudoers **plugin supports its own plugin interface to allow non-Unix group lookups which can query a group source other than the standard Unix group database. This can be used to implement support for the _nonunix_group_ syntax described earlier. Group provider plugins are specified via the _group_plugin_ setting. The argument to _group_plugin_ should consist of the plugin path, either fully-qualified or relative to the _/usr/libexec/sudo_ directory, followed by any configuration options the plugin requires. These options (if specified) will be passed to the plugin's initialization function. If op‐ tions are present, the string must be enclosed in double quotes (""). The following group provider plugins are installed by default: group_file The _group_file_ plugin supports an alternate group file that uses the same syntax as the _/etc/group_ file. The path to the group file should be specified as an option to the plugin. For example, if the group file to be used is _/etc/sudo-group_: Defaults group_plugin="group_file.so /etc/sudo-group" system_group The _system_group_ plugin supports group lookups via the standard C library functions [_getgrnam_(3)](https://www.chedong.com/phpMan.php/man/getgrnam/3/markdown) and [_getgrid_(3)](https://www.chedong.com/phpMan.php/man/getgrid/3/markdown). This plugin can be used in instances where the user be‐ longs to groups not present in the user's supplemental group vector. This plugin takes no options: Defaults group_plugin=system_group.so The group provider plugin API is described in detail in [_sudo_plugin_(5)](https://www.chedong.com/phpMan.php/man/sudoplugin/5/markdown). ## EVENT LOGGING **sudoers **can log events in either JSON or _sudo_ format, this section describes the _sudo_ log format. Depending on _sudoers_ configuration, **sudoers **can log events via [_syslog_(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown), to a local log file, or both. The log format is almost identical in both cases. Any control characters present in the log data are formatted in octal with a leading ‘#’ character. For example, a horizontal tab is stored as ‘#011’ and an embedded carriage return is stored as ‘#015’. In addition, space characters in the command path are stored as ‘#040’. Command line arguments that contain spaces are enclosed in single quotes (''). This makes it possible to distin‐ guish multiple command line arguments from a single argument that contains spaces. Literal single quotes and backslash characters (‘\’) in command line arguments are escaped with a backslash. ### Accepted command log entries Commands that sudo runs are logged using the following format (split into multiple lines for readability): date hostname progname: username : TTY=ttyname ; CHROOT=chroot ; \ PWD=cwd ; USER=runasuser ; GROUP=runasgroup ; TSID=logid ; \ ENV=env_vars COMMAND=command Where the fields are as follows: date The date the command was run. Typically, this is in the format “MMM, DD, HH:MM:SS”. If logging via [_syslog_(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown), the actual date format is controlled by the syslog daemon. If logging to a file and the _log_year_ option is enabled, the date will also include the year. hostname The name of the host **sudo **was run on. This field is only present when logging via [_syslog_(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown). progname The name of the program, usually _sudo_ or _sudoedit_. This field is only present when logging via [_syslog_(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown). username The login name of the user who ran **sudo**. ttyname The short name of the terminal (e.g., “console”, “tty01”, or “pts/0”) **sudo **was run on, or “unknown” if there was no terminal present. chroot The root directory that the command was run in, if one was specified. cwd The current working directory that **sudo **was run in. runasuser The user the command was run as. runasgroup The group the command was run as if one was specified on the command line. logid An I/O log identifier that can be used to replay the command's output. This is only present when the _log_input_ or _log_output_ option is enabled. env_vars A list of environment variables specified on the command line, if specified. command The actual command that was executed, including any command line arguments. Messages are logged using the locale specified by _sudoers_locale_, which defaults to the ‘C’ locale. ### Denied command log entries If the user is not allowed to run the command, the reason for the denial will follow the user name. Possible reasons include: user NOT in sudoers The user is not listed in the _sudoers_ file. user NOT authorized on host The user is listed in the _sudoers_ file but is not allowed to run commands on the host. command not allowed The user is listed in the _sudoers_ file for the host but they are not allowed to run the specified command. 3 incorrect password attempts The user failed to enter their password after 3 tries. The actual number of tries will vary based on the number of failed attempts and the value of the _passwd_tries_ option. a password is required The **-n **option was specified but a password was required. sorry, you are not allowed to set the following environment variables The user specified environment variables on the command line that were not allowed by _sudoers_. ### Error log entries If an error occurs, **sudoers **will log a message and, in most cases, send a message to the ad‐ ministrator via email. Possible errors include: parse error in /etc/sudoers near line N **sudoers **encountered an error when parsing the specified file. In some cases, the actual error may be one line above or below the line number listed, depending on the type of er‐ ror. problem with defaults entries The _sudoers_ file contains one or more unknown Defaults settings. This does not prevent **sudo **from running, but the _sudoers_ file should be checked using **visudo**. timestamp owner (username): No such user The time stamp directory owner, as specified by the _timestampowner_ setting, could not be found in the password database. unable to open/read /etc/sudoers The _sudoers_ file could not be opened for reading. This can happen when the _sudoers_ file is located on a remote file system that maps user-ID 0 to a different value. Normally, **sudoers **tries to open the _sudoers_ file using group permissions to avoid this problem. Con‐ sider either changing the ownership of _/etc/sudoers_ or adding an argument like “sudoers_uid=N” (where ‘N’ is the user-ID that owns the _sudoers_ file) to the end of the **sudoers _**Plugin_ line in the [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) file. unable to open /etc/sudoers The _/etc/sudoers_ file is missing. /etc/sudoers is not a regular file The _/etc/sudoers_ file exists but is not a regular file or symbolic link. /etc/sudoers is owned by uid N, should be 0 The _sudoers_ file has the wrong owner. If you wish to change the _sudoers_ file owner, add “sudoers_uid=N” (where ‘N’ is the user-ID that owns the _sudoers_ file) to the **sudoers _**Plugin_ line in the [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) file. /etc/sudoers is world writable The permissions on the _sudoers_ file allow all users to write to it. The _sudoers_ file must not be world-writable, the default file mode is 0440 (readable by owner and group, writable by none). The default mode may be changed via the “sudoers_mode” option to the **sudoers** _Plugin_ line in the [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) file. /etc/sudoers is owned by gid N, should be 1 The _sudoers_ file has the wrong group ownership. If you wish to change the _sudoers_ file group ownership, add “sudoers_gid=N” (where ‘N’ is the group-ID that owns the _sudoers_ file) to the **sudoers _**Plugin_ line in the [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) file. unable to open /run/sudo/ts/user-ID **sudoers **was unable to read or create the user's time stamp file. This can happen when _timestampowner_ is set to a user other than **root **and the mode on _/run/sudo_ is not searchable by group or other. The default mode for _/run/sudo_ is 0711. unable to write to /run/sudo/ts/user-ID **sudoers **was unable to write to the user's time stamp file. /run/sudo/ts is owned by uid X, should be Y The time stamp directory is owned by a user other than _timestampowner_. This can occur when the value of _timestampowner_ has been changed. **sudoers **will ignore the time stamp directory until the owner is corrected. /run/sudo/ts is group writable The time stamp directory is group-writable; it should be writable only by _timestampowner_. The default mode for the time stamp directory is 0700. **sudoers **will ignore the time stamp directory until the mode is corrected. ### Notes on logging via syslog By default, **sudoers **logs messages via [_syslog_(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown). The _date_, _hostname_, and _progname_ fields are added by the system's [_syslog_(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown) function, not **sudoers **itself. As such, they may vary in for‐ mat on different systems. The maximum size of syslog messages varies from system to system. The _syslog_maxlen_ setting can be used to change the maximum syslog message size from the default value of 980 bytes. For more information, see the description of _syslog_maxlen_. ### Notes on logging to a file If the _logfile_ option is set, **sudoers **will log to a local file, such as _/var/log/sudo_. When logging to a file, **sudoers **uses a format similar to [_syslog_(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown), with a few important differ‐ ences: 1. The _progname_ field is not present. 2. The _hostname_ is only logged if the _log_host_ option is enabled. 3. The date does not include the year unless the _log_year_ option is enabled. 4. Lines that are longer than _loglinelen_ characters (80 by default) are word-wrapped and continued on the next line with a four character indent. This makes entries easier to read for a human being, but makes it more difficult to use [_grep_(1)](https://www.chedong.com/phpMan.php/man/grep/1/markdown) on the log files. If the _loglinelen_ option is set to 0 (or negated with a ‘!’), word wrap will be disabled. ## I/O LOGGING When I/O logging is enabled, **sudo **will runs the command in a pseudo-terminal, logging user input and/or output, depending on which **sudoers **flags are enabled. There are five distinct types of I/O that can be logged, each with a corresponding **sudoers **flag. ### Type Flag Description terminal input log_ttyin keystrokes entered by the user terminal output log_ttyout command output displayed to the screen standard input log_stdin input from a pipe or a file standard output log_stdout output to a pipe or a file standard error log_stderr output to a pipe or a file In addition to flags described the above, the _log_input_ flag and LOG_INPUT command tag set both _log_ttyin_ and _log_stdin_. The _log_output_ flag and LOG_OUTPUT command tag set _log_ttyout_, _log_stdout_, and _log_stderr_. To capture terminal input and output, **sudo **run the command in a pseudo-terminal, logging the input and output before passing it on to the user. To capture the standard input, standard output or standard error, **sudo **uses a pipe to interpose itself between the input or output stream, logging the I/O before passing it to the other end of the pipe. I/O can be logged either to the local machine or to a remote log server. For local logs, I/O is logged to the directory specified by the _iolog_dir_ option (_/var/log/sudo-io_ by default) using a unique session ID that is included in the **sudo **log line, prefixed with ‘TSID=’. The _iolog_file_ option may be used to control the format of the session ID. For remote logs, the _log_servers_ setting is used to specify one or more log servers running **sudo_logsrvd **or an‐ other server that implements the protocol described by [_sudo_logsrv.proto_(5)](https://www.chedong.com/phpMan.php/man/sudologsrv.proto/5/markdown). ### I/O logging pitfals When logging standard input, anything sent to the standard input will be consumed, regardless of whether or not the command run via **sudo **is actively reading the standard input. This may have unexpected results when using **sudo **in a shell script that expects to process the stan‐ dard input. For example, given the following shell script: #!/bin/sh sudo echo testing echo done It will behave as expected when the script is passed to the shell as a an argument: $ sh test.sh testing done However, if the script is passed to the shell on the standard input, the ‘sudo echo testing’ command will consume the rest of the script. This means that the ‘echo done’ statement is never executed. $ sh -s < test.sh testing There are several ways to work around this problem: 1. Redirect the standard input from _/dev/null_ when running a command via **sudo **that does not need to read the standard input. sudo echo testing < /dev/null 2. Pass the script to the shell by path name instead of via the standard input. sh test.sh 3. Disable logging the standard input for commands that do not need to read the standard input. Defaults!/bin/echo !log_stdin Depending on the command, it may not be desirable to log the standard input or standard out‐ put. For example, I/O logging of commands that send or receive large amount of data via the standard output or standard input such as [_rsync_(1)](https://www.chedong.com/phpMan.php/man/rsync/1/markdown) and [_tar_(1)](https://www.chedong.com/phpMan.php/man/tar/1/markdown) could fill up the log file sys‐ tem with superfluous data. It is possible to disable logging of the standard input and stan‐ dard output for such commands as follows: Cmnd_Alias COPY_CMDS = /usr/bin/tar, /usr/bin/cpio, /usr/bin/rsync # Log input and output but omit stdin and stdout when copying files. Defaults log_input, log_output Defaults!COPY_CMDS !log_stdin, !log_stdout However, be aware that using the _log_input_ flag or the LOG_INPUT command tag will also enable _log_stdin_. Likewise, the _log_ouput_ flag or the LOG_OUTPUT command tag will enable _log_stdout_ and _log_stderr._ Careful ordering of rules may be necessary to achieve the results that you expect. ### I/O log format For both local and remote I/O logs, each log is stored in a separate directory that contains the following files: _log_ A text file containing information about the command. The first line consists of the following colon-delimited fields: the time the command was run, the name of the user who ran **sudo**, the name of the target user, the name of the target group (op‐ tional), the terminal that **sudo **was run from, and the number of lines and columns of the terminal. The second and third lines contain the working directory the com‐ mand was run from and the path name of the command itself (with arguments if present). _log.json_ A JSON-formatted file containing information about the command. This is similar to the _log_ file but contains additional information and is easily extensible. The _log.json_ file will be used by [_sudoreplay_(8)](https://www.chedong.com/phpMan.php/man/sudoreplay/8/markdown) in preference to the _log_ file if it ex‐ ists. The file may contain the following elements: timestamp A JSON object containing time the command was run. It consists of two val‐ ues, _seconds_ and _nanoseconds_. columns The number of columns of the terminal the command ran on, or zero if no ter‐ minal was present. command The fully-qualified path of the command that was run. lines The number of lines of the terminal the command ran on, or zero if no termi‐ nal was present. runargv A JSON array representing the command's argument vector as passed to the [_execve_(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown) system call. runenv A JSON array representing the command's environment as passed to the [_execve_(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown) system call. rungid The group ID the command ran as. This element is only present when the user specifies a group on the command line. rungroup The name of the group the command ran as. This element is only present when the user specifies a group on the command line. runuid The user ID the command ran as. runuser The name of the user the command ran as. submitcwd The current working directory at the time **sudo **was run. submithost The name of the host the command was run on. submituser The name of the user who ran the command via **sudo**. ttyname The path name of the terminal the user invoked **sudo **from. If the command was run in a pseudo-terminal, _ttyname_ will be different from the terminal the command actually ran in. _timing_ Timing information used to replay the session. Each line consists of the I/O log entry type and amount of time since the last entry, followed by type-specific data. The I/O log entry types and their corresponding type-specific data are: 0 standard input, number of bytes in the entry 1 standard output, number of bytes in the entry 2 standard error, number of bytes in the entry 3 terminal input, number of bytes in the entry 4 terminal output, number of bytes in the entry 5 window change, new number lines and columns 6 bug compatibility for **sudo **1.8.7 terminal output 7 command suspend or resume, signal received _ttyin_ Raw input from the user's terminal, exactly as it was received. This file is only present if the _log_input_ or _log_ttyin_ flags are set and **sudo **was run from a termi‐ nal. No post-processing is performed. For manual viewing, you may wish to convert carriage return characters in the log to line feeds. For example: ‘gunzip -c ttyin | tr "\r" "\n"’ _stdin_ The standard input when no terminal is present, or input redirected from a pipe or file. This file is only present if the _log_input_ or _log_stdin_ flags are set and the standard input is not connected to a terminal. _ttyout_ Output from the pseudo-terminal (what the command writes to the screen). Terminal- specific post-processing is performed before the data is logged. This means that, for example, line feeds are usually converted to line feed/carriage return pairs and tabs may be expanded to spaces. This file is only present if the _log_output_ or _log_ttyout_ flags are set and **sudo **was run from a terminal. _stdout_ The standard output when no terminal is present, or output redirected to a pipe or file. This file is only present if the _log_output_ or _log_stdout_ flags are set and the standard output is not connected to a terminal. _stderr_ The standard error when no terminal is present, or output redirected to a pipe or file. This file is only present if the _log_output_ or _log_stderr_ flags are set and the standard error is not connected to a terminal. All files other than _log_ are compressed in gzip format unless the _compress_io_ flag has been disabled. Due to buffering, it is not normally possible to display the I/O logs in real-time as the program is executing. The I/O log data will not be complete until the program run by **sudo **has exited or has been terminated by a signal. The _iolog_flush_ flag can be used to dis‐ able buffering, in which case I/O log data is written to disk as soon as it is available. The output portion of an I/O log file can be viewed with the [_sudoreplay_(8)](https://www.chedong.com/phpMan.php/man/sudoreplay/8/markdown) utility, which can also be used to list or search the available logs. User input may contain sensitive information such as passwords (even if they are not echoed to the screen), which will be stored in the log file unencrypted. In most cases, logging the command output via _log_output_ or LOG_OUTPUT is all that is required. When logging input, consider disabling the _log_passwords_ flag. Since each session's I/O logs are stored in a separate directory, traditional log rotation utilities cannot be used to limit the number of I/O logs. The simplest way to limit the num‐ ber of I/O is by setting the _maxseq_ option to the maximum number of logs you wish to store. Once the I/O log sequence number reaches _maxseq_, it will be reset to zero and **sudoers **will truncate and re-use any existing I/O logs. ## FILES _/etc/sudo.conf_ Sudo front-end configuration _/etc/sudoers_ List of who can run what _/etc/group_ Local groups file _/etc/netgroup_ List of network groups _/var/log/sudo-io_ I/O log files _/run/sudo/ts_ Directory containing time stamps for the **sudoers **security policy _/var/lib/sudo/lectured_ Directory containing lecture status files for the **sudoers **security policy _/etc/environment_ Initial environment for **-i **mode on AIX and Linux systems ## EXAMPLES Below are example _sudoers_ file entries. Admittedly, some of these are a bit contrived. First, we allow a few environment variables to pass and then define our _aliases_: # Run X applications through sudo; HOME is used to find the # .Xauthority file. Other programs use HOME to locate configuration # files and this may lead to privilege escalation! Defaults env_keep += "DISPLAY HOME" # User alias specification User_Alias FULLTIMERS = millert, mikef, dowdy User_Alias PARTTIMERS = bostley, jwfox, crawl User_Alias WEBADMIN = will, wendy, wim # Runas alias specification Runas_Alias OP = root, operator Runas_Alias DB = oracle, sybase Runas_Alias ADMINGRP = adm, oper # Host alias specification Host_Alias SPARC = bigtime, eclipse, moet, anchor :\ SGI = grolsch, dandelion, black :\ ALPHA = widget, thalamus, foobar :\ HPPA = boa, nag, python Host_Alias CUNETS = 128.138.0.0/255.255.0.0 Host_Alias CSNETS = 128.138.243.0, 128.138.204.0/24, 128.138.242.0 Host_Alias SERVERS = primary, mail, www, ns Host_Alias CDROM = orion, perseus, hercules # Cmnd alias specification Cmnd_Alias DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\ /usr/sbin/restore, /usr/sbin/rrestore,\ sha224:0GomF8mNN3wlDt1HD9XldjJ3SNgpFdbjO1+NsQ== \ /home/operator/bin/start_backups Cmnd_Alias KILL = /usr/bin/kill Cmnd_Alias PRINTING = /usr/sbin/lpc, /usr/bin/lprm Cmnd_Alias SHUTDOWN = /usr/sbin/shutdown Cmnd_Alias HALT = /usr/sbin/halt Cmnd_Alias REBOOT = /usr/sbin/reboot Cmnd_Alias SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh,\ /usr/local/bin/tcsh, /usr/bin/rsh,\ /usr/local/bin/zsh Cmnd_Alias SU = /usr/bin/su Cmnd_Alias PAGERS = /usr/bin/more, /usr/bin/pg, /usr/bin/less Here we override some of the compiled in default values. We want **sudo **to log via [_syslog_(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown) using the _auth_ facility in all cases and for commands to be run with the target user's home directory as the working directory. We don't want to subject the full time staff to the **sudo** lecture and we want to allow them to run commands in a [_chroot_(2)](https://www.chedong.com/phpMan.php/man/chroot/2/markdown) “sandbox” via the **-R **option. User **millert **need not provide a password and we don't want to reset the LOGNAME or USER envi‐ ronment variables when running commands as **root**. Additionally, on the machines in the SERVERS _Host_Alias_, we keep an additional local log file and make sure we log the year in each log line since the log entries will be kept around for several years. Lastly, we dis‐ able shell escapes for the commands in the PAGERS _Cmnd_Alias_ (_/usr/bin/more_, _/usr/bin/pg_ and _/usr/bin/less_). This will not effectively constrain users with **sudo ALL **privileges. # Override built-in defaults Defaults syslog=auth,runcwd=~ Defaults>root !set_logname Defaults:FULLTIMERS !lecture,runchroot=* Defaults:millert !authenticate Defaults@SERVERS log_year, logfile=/var/log/sudo.log Defaults!PAGERS noexec The _User_ _specification_ is the part that actually determines who may run what. root ALL = (ALL) ALL %wheel ALL = (ALL) ALL We let **root **and any user in group **wheel **run any command on any host as any user. FULLTIMERS ALL = NOPASSWD: ALL Full time sysadmins (**millert**, **mikef**, and **dowdy**) may run any command on any host without au‐ thenticating themselves. PARTTIMERS ALL = ALL Part time sysadmins **bostley**, **jwfox**, and **crawl**) may run any command on any host but they must authenticate themselves first (since the entry lacks the NOPASSWD tag). jack CSNETS = ALL The user **jack **may run any command on the machines in the CSNETS alias (the networks 128.138.243.0, 128.138.204.0, and 128.138.242.0). Of those networks, only 128.138.204.0 has an explicit netmask (in CIDR notation) indicating it is a class C network. For the other networks in CSNETS, the local machine's netmask will be used during matching. lisa CUNETS = ALL The user **lisa **may run any command on any host in the CUNETS alias (the class B network 128.138.0.0). operator ALL = DUMPS, KILL, SHUTDOWN, HALT, REBOOT, PRINTING,\ sudoedit /etc/printcap, /usr/oper/bin/ The **operator **user may run commands limited to simple maintenance. Here, those are commands related to backups, killing processes, the printing system, shutting down the system, and any commands in the directory _/usr/oper/bin/_. One command in the DUMPS Cmnd_Alias includes a sha224 digest, _/home/operator/bin/start_backups_. This is because the directory containing the script is writable by the operator user. If the script is modified (resulting in a di‐ gest mismatch) it will no longer be possible to run it via **sudo**. joe ALL = /usr/bin/su operator The user **joe **may only [_su_(1)](https://www.chedong.com/phpMan.php/man/su/1/markdown) to operator. pete HPPA = /usr/bin/passwd [A-Za-z]*, !/usr/bin/passwd *root* %opers ALL = (: ADMINGRP) /usr/sbin/ Users in the **opers **group may run commands in _/usr/sbin/_ as themselves with any group in the ADMINGRP _Runas_Alias_ (the **adm **and **oper **groups). The user **pete **is allowed to change anyone's password except for **root **on the HPPA machines. Because command line arguments are matched as a single, concatenated string, the ‘*’ wildcard will match _multiple_ words. This example assumes that [_passwd_(1)](https://www.chedong.com/phpMan.php/man/passwd/1/markdown) does not take multiple user names on the command line. On systems with GNU [_getopt_(3)](https://www.chedong.com/phpMan.php/man/getopt/3/markdown), options to [_passwd_(1)](https://www.chedong.com/phpMan.php/man/passwd/1/markdown) may be speci‐ fied after the user argument. As a result, this rule will also allow: passwd username --expire which may not be desirable. bob SPARC = (OP) ALL : SGI = (OP) ALL The user **bob **may run anything on the SPARC and SGI machines as any user listed in the OP _Runas_Alias_ (**root **and **operator**.) jim +biglab = ALL The user **jim **may run any command on machines in the _biglab_ netgroup. **sudo **knows that “biglab” is a netgroup due to the ‘+’ prefix. +secretaries ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser Users in the **secretaries **netgroup need to help manage the printers as well as add and remove users, so they are allowed to run those commands on all machines. fred ALL = (DB) NOPASSWD: ALL The user **fred **can run commands as any user in the DB _Runas_Alias_ (**oracle **or **sybase**) without giving a password. john ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root* On the ALPHA machines, user **john **may su to anyone except **root **but he is not allowed to spec‐ ify any options to the [_su_(1)](https://www.chedong.com/phpMan.php/man/su/1/markdown) command. jen ALL, !SERVERS = ALL The user **jen **may run any command on any machine except for those in the SERVERS _Host_Alias_ (primary, mail, www, and ns). jill SERVERS = /usr/bin/, !SU, !SHELLS For any machine in the SERVERS _Host_Alias_, **jill **may run any commands in the directory _/usr/bin/_ except for those commands belonging to the SU and SHELLS _Cmnd_Aliases_. While not specifically mentioned in the rule, the commands in the PAGERS _Cmnd_Alias_ all reside in _/usr/bin_ and have the _noexec_ option set. steve CSNETS = (operator) /usr/local/op_commands/ The user **steve **may run any command in the directory /usr/local/op_commands/ but only as user operator. matt valkyrie = KILL On his personal workstation, valkyrie, **matt **needs to be able to kill hung processes. WEBADMIN www = (www) ALL, (root) /usr/bin/su www On the host www, any user in the WEBADMIN _User_Alias_ (will, wendy, and wim), may run any com‐ mand as user www (which owns the web pages) or simply [_su_(1)](https://www.chedong.com/phpMan.php/man/su/1/markdown) to www. ALL CDROM = NOPASSWD: /sbin/umount /CDROM,\ /sbin/mount -o nosuid\,nodev /dev/cd0a /CDROM Any user may mount or unmount a CD-ROM on the machines in the CDROM _Host_Alias_ (orion, perseus, hercules) without entering a password. This is a bit tedious for users to type, so it is a prime candidate for encapsulating in a shell script. ## SECURITY NOTES **Limitations of the **‘!’ operator It is generally not effective to “subtract” commands from **ALL **using the ‘!’ operator. A user can trivially circumvent this by copying the desired command to a different name and then ex‐ ecuting that. For example: bill ALL = ALL, !SU, !SHELLS Doesn't really prevent **bill **from running the commands listed in SU or SHELLS since he can simply copy those commands to a different name, or use a shell escape from an editor or other program. Therefore, these kind of restrictions should be considered advisory at best (and reinforced by policy). In general, if a user has sudo **ALL **there is nothing to prevent them from creating their own program that gives them a **root **shell (or making their own copy of a shell) regardless of any ‘!’ elements in the user specification. ### Security implications of fast_glob If the _fast_glob_ option is in use, it is not possible to reliably negate commands where the path name includes globbing (aka wildcard) characters. This is because the C library's [_fnmatch_(3)](https://www.chedong.com/phpMan.php/man/fnmatch/3/markdown) function cannot resolve relative paths. While this is typically only an inconve‐ nience for rules that grant privileges, it can result in a security issue for rules that sub‐ tract or revoke privileges. For example, given the following _sudoers_ file entry: john ALL = /usr/bin/passwd [a-zA-Z0-9]*, /usr/bin/chsh [a-zA-Z0-9]*,\ /usr/bin/chfn [a-zA-Z0-9]*, !/usr/bin/* root User **john **can still run ‘/usr/bin/passwd root’ if _fast_glob_ is enabled by changing to _/usr/bin_ and running ‘./passwd root’ instead. Another potential issue is that when **sudo **executes the command, it must use the command or path specified by the user instead of a path listed in the _sudoers_ file. This may lead to a time of check versus time of use race condition. ### Wildcards in command arguments Command line arguments are matched as a single, concatenated string. This mean a wildcard character such as ‘?’ or ‘*’ will match across word boundaries, which may be unexpected. For example, while a sudoers entry like: %operator ALL = /bin/cat /var/log/messages* will allow command like: $ sudo cat /var/log/messages.1 It will also allow: $ sudo cat /var/log/messages /etc/shadow which is probably not what was intended. A safer alternative is to use a regular expression for matching command line arguments. The above example can be rewritten as a regular expres‐ sion: %operator ALL = /bin/cat ^/var/log/messages[^[:space:]]*$ The regular expression will only match a single file with a name that begins with _/var/log/messages_ and does not include any white space in the name. It is often better to do command line processing outside of the _sudoers_ file in a scripting language for anything non- trivial. ### Regular expressions in command names Using a regular expression to match a command name has the same security implications as us‐ ing the _fast_glob_ option: **• **It is not possible to reliably negate commands when the path name is a regular expression. **• **When **sudo **executes the command, it must use the command or path specified by the user in‐ stead of a path listed in the _sudoers_ file. This may lead to a time of check versus time of use race condition. These issues do not apply to rules where only the command line options are matched using a regular expression. ### Preventing shell escapes Once **sudo **executes a program, that program is free to do whatever it pleases, including run other programs. This can be a security issue since it is not uncommon for a program to allow shell escapes, which lets a user bypass **sudo**'s access control and logging. Common programs that permit shell escapes include shells (obviously), editors, paginators, mail, and terminal programs. There are four basic approaches to this problem: restrict Avoid giving users access to commands that allow the user to run arbitrary com‐ mands. Many editors have a restricted mode where shell escapes are disabled, though **sudoedit **is a better solution to running editors via **sudo**. Due to the large number of programs that offer shell escapes, restricting users to the set of programs that do not is often unworkable. intercept On most systems, **sudo**'s _intercept_ functionality can be used to transparently in‐ tercept an attempt to run a new command, allow or deny it based on _sudoers_ rules, and log the result. For example, this can be used to restrict the commands run from within a privileged shell or editor. However, not all programs operate cor‐ rectly when _intercept_ is enabled. There are two underlying mechanisms that may be used to implement _intercept_ mode: _dso_ and _trace_. The _intercept_type_ setting can be used to select between them. The first mechanism, _dso_, overrides the standard C library functions that are used to execute a command. It does this by setting an environment variable (usually LD_PRELOAD) to the path of a dynamic shared object, or shared library, containing custom versions of the [_execve_(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown), [_execl_(3)](https://www.chedong.com/phpMan.php/man/execl/3/markdown), [_execle_(3)](https://www.chedong.com/phpMan.php/man/execle/3/markdown), [_execlp_(3)](https://www.chedong.com/phpMan.php/man/execlp/3/markdown), [_execv_(3)](https://www.chedong.com/phpMan.php/man/execv/3/markdown), [_execvp_(3)](https://www.chedong.com/phpMan.php/man/execvp/3/markdown), [_execvpe_(3)](https://www.chedong.com/phpMan.php/man/execvpe/3/markdown), and [_system_(3)](https://www.chedong.com/phpMan.php/man/system/3/markdown) library functions that connect back to **sudo** for a policy decision. Note, however, that this applies only to dynamically- linked executables. It is not possible to intercept commands for statically- linked executables or executables that run under binary emulation this way. Be‐ cause most dynamic loaders ignore LD_PRELOAD (or the equivalent) when running set- user-ID and set-group-ID programs, **sudoers **will not permit such programs to be run in _intercept_ mode by default. The _dso_ mechanism is incompatible with **sudo**'s SELinux RBAC support (but see below). SELinux disables LD_PRELOAD by default and interferes with file descriptor inheritance, which **sudo **relies on. The second mechanism, _trace_, is available on Linux systems that support [_seccomp_(2)](https://www.chedong.com/phpMan.php/man/seccomp/2/markdown) filtering. It uses [_ptrace_(2)](https://www.chedong.com/phpMan.php/man/ptrace/2/markdown) and [_seccomp_(2)](https://www.chedong.com/phpMan.php/man/seccomp/2/markdown) to intercept the [_execve_(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown) system call instead of pre-loading a dynamic shared object. Both static and dynamic exe‐ cutables are supported and it is compatible with **sudo**'s SELinux RBAC mode. Func‐ tions utilizing the [_execveat_(2)](https://www.chedong.com/phpMan.php/man/execveat/2/markdown) system call, such as [_fexecve_(3)](https://www.chedong.com/phpMan.php/man/fexecve/3/markdown), are not currently intercepted. Programs that rely on [_ptrace_(2)](https://www.chedong.com/phpMan.php/man/ptrace/2/markdown) themselves, such as debuggers and system call tracers (such as [_strace_(1)](https://www.chedong.com/phpMan.php/man/strace/1/markdown) and [_truss_(1)](https://www.chedong.com/phpMan.php/man/truss/1/markdown)) will be unable to function if _intercept_ is enabled in _trace_ mode. This same restriction applies to the _log_subcmds_ sudoers option. The _intercept_ feature is known to work on Solaris, *BSD, Linux, macOS, HP-UX 11.x and AIX 5.3 and above. It should be supported on most operating systems that sup‐ port the LD_PRELOAD environment variable or an equivalent. It is not possible to intercept shell built-in commands or restrict the ability to read or write sensi‐ tive files from within a shell. To enable intercept mode on a per-command basis, use the INTERCEPT tag as docu‐ mented in the User Specification section above. Here is that example again: chuck research = INTERCEPT: ALL This allows user **chuck **to run any command on the machine “research” in intercept mode. Any commands run via shell escapes will be validated and logged by **sudo**. If you are unsure whether or not your system is capable of supporting _intercept_, you can always just try it out and check whether or not external commands run via a shell are logged when _intercept_ is enabled. There is an inherent race condition between when a command is checked against **sudoers **rules and when it is actually executed. If a user is allowed to run arbi‐ trary commands, they may be able to change the [_execve_(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown) arguments in the program after the **sudoers **policy check has completed but before the new command is exe‐ cuted. Starting with version 1.9.12, the _trace_ method will verify that the com‐ mand and its arguments have not changed after [_execve_(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown) has completed but before execution of the new program has had a chance to run. This is not the case with the _dso_ method. See the description of the _intercept_verify_ setting for more in‐ formation. log There are two separate but related ways to log additional commands. The first is to enable I/O logging using the _log_output_ flag. This will log the command's out‐ put but will not create an event log entry when the additional command is run. The second is to enable the _log_subcmds_ flag in _sudoers_ which will create an event log entry every time a new command is run. If I/O logging is also enabled, the log entry will include a time offset into the I/O log to indicate when the command was run. This offset can be passed to the [_sudoreplay_(8)](https://www.chedong.com/phpMan.php/man/sudoreplay/8/markdown) utility to replay the I/O log at the exact moment when the command was run. The _log_subcmds_ flag uses the same mechanism as _intercept_ (see above) and has the same limitations. noexec **sudo**'s _noexec_ functionality can be used to prevent a program run by **sudo **from exe‐ cuting any other programs. On most systems, it uses the same LD_PRELOAD mechanism as _intercept_ (see above) and thus the same caveats apply. The _noexec_ functional‐ ity is capable of blocking execution of commands run via the [_execve_(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown), [_execl_(3)](https://www.chedong.com/phpMan.php/man/execl/3/markdown), [_execle_(3)](https://www.chedong.com/phpMan.php/man/execle/3/markdown), [_execlp_(3)](https://www.chedong.com/phpMan.php/man/execlp/3/markdown), [_exect_(3)](https://www.chedong.com/phpMan.php/man/exect/3/markdown), [_execv_(3)](https://www.chedong.com/phpMan.php/man/execv/3/markdown), [_execveat_(3)](https://www.chedong.com/phpMan.php/man/execveat/3/markdown), [_execvP_(3)](https://www.chedong.com/phpMan.php/man/execvP/3/markdown), [_execvp_(3)](https://www.chedong.com/phpMan.php/man/execvp/3/markdown), [_execvpe_(3)](https://www.chedong.com/phpMan.php/man/execvpe/3/markdown), [_fexecve_(3)](https://www.chedong.com/phpMan.php/man/fexecve/3/markdown), [_popen_(3)](https://www.chedong.com/phpMan.php/man/popen/3/markdown), [_posix_spawn_(3)](https://www.chedong.com/phpMan.php/man/posixspawn/3/markdown), [_posix_spawnp_(3)](https://www.chedong.com/phpMan.php/man/posixspawnp/3/markdown), [_system_(3)](https://www.chedong.com/phpMan.php/man/system/3/markdown), and [_wordexp_(3)](https://www.chedong.com/phpMan.php/man/wordexp/3/markdown) functions. On Linux, a [_seccomp_(2)](https://www.chedong.com/phpMan.php/man/seccomp/2/markdown) filter is used to implement _noexec_. On Solaris 10 and higher, _noexec_ uses Solaris privileges instead of the LD_PRELOAD environment variable. To enable _noexec_ for a command, use the NOEXEC tag as documented in the User Spec‐ ification section above. Here is that example again: aaron shanty = NOEXEC: /usr/bin/more, /usr/bin/vi This allows user **aaron **to run _/usr/bin/more_ and _/usr/bin/vi_ with _noexec_ enabled. This will prevent those two commands from executing other commands (such as a shell). If you are unsure whether or not your system is capable of supporting _noexec_ you can always just try it out and check whether shell escapes work when _noexec_ is enabled. Restricting shell escapes is not a panacea. Programs running as **root **are still capable of many potentially hazardous operations (such as changing or overwriting files) that could lead to unintended privilege escalation. In the specific case of an editor, a safer approach is to give the user permission to run **sudoedit **(see below). ### Secure editing The **sudoers **plugin includes **sudoedit **support which allows users to securely edit files with the editor of their choice. As **sudoedit **is a built-in command, it must be specified in the _sudoers_ file without a leading path. However, it may take command line arguments just as a normal command does. Wildcards used in _sudoedit_ command line arguments are expected to be path names, so a forward slash (‘/’) will not be matched by a wildcard. Unlike other **sudo **commands, the editor is run with the permissions of the invoking user and with the environment unmodified. More information may be found in the description of the **-e** option in [_sudo_(8)](https://www.chedong.com/phpMan.php/man/sudo/8/markdown). For example, to allow user operator to edit the “message of the day” file on any machine: operator ALL = sudoedit /etc/motd The operator user then runs **sudoedit **as follows: $ sudoedit /etc/motd The editor will run as the operator user, not **root**, on a temporary copy of _/etc/motd_. After the file has been edited, _/etc/motd_ will be updated with the contents of the temporary copy. Users should _never_ be granted **sudoedit **permission to edit a file that resides in a directory the user has write access to, either directly or via a wildcard. If the user has write ac‐ cess to the directory it is possible to replace the legitimate file with a link to another file, allowing the editing of arbitrary files. To prevent this, starting with version 1.8.16, symbolic links will not be followed in writable directories and **sudoedit **will refuse to edit a file located in a writable directory unless the _sudoedit_checkdir_ option has been disabled or the invoking user is **root**. Additionally, in version 1.8.15 and higher, **sudoedit** will refuse to open a symbolic link unless either the _sudoedit_follow_ option is enabled or the _sudoedit_ command is prefixed with the FOLLOW tag in the _sudoers_ file. ### Time stamp file checks **sudoers **will check the ownership of its time stamp directory (_/run/sudo/ts_ by default) and ignore the directory's contents if it is not owned by **root **or if it is writable by a user other than **root**. Older versions of **sudo **stored time stamp files in _/tmp_; this is no longer recommended as it may be possible for a user to create the time stamp themselves on systems that allow unprivileged users to change the ownership of files they create. While the time stamp directory _should_ be cleared at reboot time, not all systems contain a _/run_ or _/var/run_ directory. To avoid potential problems, **sudoers **will ignore time stamp files that date from before the machine booted on systems where the boot time is available. Some systems with graphical desktop environments allow unprivileged users to change the sys‐ tem clock. Since **sudoers **relies on the system clock for time stamp validation, it may be possible on such systems for a user to run **sudo **for longer than _timestamp_timeout_ by setting the clock back. To combat this, **sudoers **uses a monotonic clock (which never moves backwards) for its time stamps if the system supports it. **sudoers **will not honor time stamps set far in the future. Time stamps with a date greater than current_time + 2 * TIMEOUT will be ignored and **sudoers **will log and complain. If the _timestamp_type_ option is set to “tty”, the time stamp record includes the device num‐ ber of the terminal the user authenticated with. This provides per-terminal granularity but time stamp records may still outlive the user's session. Unless the _timestamp_type_ option is set to “global”, the time stamp record also includes the session ID of the process that last authenticated. This prevents processes in different ter‐ minal sessions from using the same time stamp record. On systems where a process's start time can be queried, the start time of the session leader is recorded in the time stamp record. If no terminal is present or the _timestamp_type_ option is set to “ppid”, the start time of the parent process is used instead. In most cases this will prevent a time stamp record from being re-used without the user entering a password when logging out and back in again. ## DEBUGGING Versions 1.8.4 and higher of the **sudoers **plugin support a flexible debugging framework that can help track down what the plugin is doing internally if there is a problem. This can be configured in the [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) file. The **sudoers **plugin uses the same debug flag format as the **sudo **front-end: _subsystem_@_priority_. The priorities used by **sudoers**, in order of decreasing severity, are: _crit_, _err_, _warn_, _notice_, _diag_, _info_, _trace_, and _debug_. Each priority, when specified, also includes all pri‐ orities higher than it. For example, a priority of _notice_ would include debug messages logged at _notice_ and higher. The following subsystems are used by the **sudoers **plugin: _alias_ _User_Alias_, _Runas_Alias_, _Host_Alias_ and _Cmnd_Alias_ processing _all_ matches every subsystem _audit_ BSM and Linux audit code _auth_ user authentication _defaults_ _sudoers_ file _Defaults_ settings _env_ environment handling _ldap_ LDAP-based sudoers _logging_ logging support _match_ matching of users, groups, hosts, and netgroups in the _sudoers_ file _netif_ network interface handling _nss_ network service switch handling in **sudoers** _parser_ _sudoers_ file parsing _perms_ permission setting _plugin_ The equivalent of _main_ for the plugin. _pty_ pseudo-terminal related code _rbtree_ redblack tree internals _sssd_ SSSD-based sudoers _util_ utility functions For example: Debug sudoers.so /var/log/sudoers_debug match@info,nss@info For more information, see the [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown) manual. ## SEE ALSO [_ssh_(1)](https://www.chedong.com/phpMan.php/man/ssh/1/markdown), [_su_(1)](https://www.chedong.com/phpMan.php/man/su/1/markdown), [_fnmatch_(3)](https://www.chedong.com/phpMan.php/man/fnmatch/3/markdown), [_glob_(3)](https://www.chedong.com/phpMan.php/man/glob/3/markdown), [_mktemp_(3)](https://www.chedong.com/phpMan.php/man/mktemp/3/markdown), [_strftime_(3)](https://www.chedong.com/phpMan.php/man/strftime/3/markdown), [_sudo.conf_(5)](https://www.chedong.com/phpMan.php/man/sudo.conf/5/markdown), [_sudo_plugin_(5)](https://www.chedong.com/phpMan.php/man/sudoplugin/5/markdown), [_sudoers.ldap_(5)](https://www.chedong.com/phpMan.php/man/sudoers.ldap/5/markdown), [_sudoers_timestamp_(5)](https://www.chedong.com/phpMan.php/man/sudoerstimestamp/5/markdown), [_sudo_(8)](https://www.chedong.com/phpMan.php/man/sudo/8/markdown), [_visudo_(8)](https://www.chedong.com/phpMan.php/man/visudo/8/markdown) ## AUTHORS Many people have worked on **sudo **over the years; this version consists of code written primar‐ ily by: Todd C. Miller See the CONTRIBUTORS.md file in the **sudo **distribution (‐ tors/) for an exhaustive list of people who have contributed to **sudo**. ## CAVEATS The _sudoers_ file should **always **be edited by the **visudo **utility which locks the file and checks for syntax errors. If _sudoers_ contains syntax errors, **sudo **may refuse to run, which is a serious problem if **sudo **is your only method of obtaining superuser privileges. Recent versions of **sudoers **will attempt to recover after a syntax error by ignoring the rest of the line after encountering an error. Older versions of **sudo **will not run if _sudoers_ contains a syntax error. When using netgroups of machines (as opposed to users), if you store fully qualified host name in the netgroup (as is usually the case), you either need to have the machine's host name be fully qualified as returned by the _hostname_ command or use the _fqdn_ option in _sudoers_. ## BUGS If you believe you have found a bug in **sudo**, you can submit a bug report at ## SUPPORT Limited free support is available via the sudo-users mailing list, see to subscribe or search the archives. ## DISCLAIMER **sudo **is provided “AS IS” and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are dis‐ claimed. See the LICENSE.md file distributed with **sudo **or for complete details. Sudo 1.9.15p5 December 19, 2023 [_SUDOERS_(5)](https://www.chedong.com/phpMan.php/man/SUDOERS/5/markdown)