man > AUDITD.CONF(5)

AUDITD.CONF(5)                     System Administration Utilities                    AUDITD.CONF(5)

NAME
       auditd.conf - audit daemon configuration file

DESCRIPTION
       The file /etc/audit/auditd.conf contains configuration information specific to the audit dae‐
       mon.  Each line should contain one configuration keyword, an equal sign, and then followed by
       appropriate configuration information. All option names and values are case insensitive.  The
       keywords  recognized are listed and described below. Each line should be limited to 160 char‐
       acters or the line will be skipped. You may add comments to the file  by  starting  the  line
       with a '#' character.


       local_events
              This  yes/no  keyword  specifies  whether or not to include local events. Normally you
              want local events so the default value is yes. Cases where you would set this to no is
              when you want to aggregate events only from the network. At the moment, this is useful
              if the audit daemon is running in a container. This option can only  be  set  once  at
              daemon start up. Reloading the config file has no effect.

       log_file
              This  keyword specifies the full path name to the log file where audit records will be
              stored. It must be a regular file.

       write_logs
              This yes/no keyword determines whether or not to write logs to the disk.  Normally you
              want this so the default is yes.

       log_format
              The log format describes how the information should be stored on disk. There are 2 op‐
              tions: raw and enriched. If set to RAW, the audit records will be stored in  a  format
              exactly  as  the  kernel  sends  it.  The  ENRICHED  option will resolve all uid, gid,
              syscall, architecture, and socket address information  before  writing  the  event  to
              disk.  This aids in making sense of events created on one system but reported/analyzed
              on another system.  The NOLOG option is now deprecated. If you were setting this  for‐
              mat, now you should set the write_logs option to no.

       log_group
              This  keyword  specifies  the group that is applied to the log file's permissions. The
              default is root. The group name can be either numeric or spelled out.

       priority_boost
              This is a non-negative number that tells the audit daemon how much of a priority boost
              it should take. The default is 4. No change is 0.

       flush  Valid values are none, incremental, incremental_async, data,  and  sync.   If  set  to
              none,  no  special effort is made to flush the audit records to disk. If set to incre‐
              mental, Then the freq parameter is used to determine how often an  explicit  flush  to
              disk  is issued.  The incremental_async parameter is very much like incremental except
              the flushing is done asynchronously for higher performance. The data  parameter  tells
              the  audit  daemon  to keep the data portion of the disk file sync'd at all times. The
              sync option tells the audit daemon to keep both the data and  meta-data  fully  sync'd
              with every write to disk. The default value is incremental_async.

       freq   This  is  a  non-negative number that tells the audit daemon how many records to write
              before issuing an explicit flush to disk command. This value is only  valid  when  the
              flush keyword is set to incremental or incremental_async.

       num_logs
              This  keyword  specifies  the  number  of  log files to keep if rotate is given as the
              max_log_file_action.  If the number is < 2, logs are not rotated. This number must  be
              999  or  less.  The default is 0 - which means no rotation. As you increase the number
              of log files being rotated, you may need to adjust the kernel backlog setting  upwards
              since it takes more time to rotate the files. This is typically done in /etc/audit/au‐
              dit.rules.  If  log  rotation is configured to occur, the daemon will check for excess
              logs and remove them in effort to keep disk space available. The excess log  check  is
              only done on startup and when a reconfigure results in a space check.

       name_format
              This option controls how computer node names are inserted into the audit event stream.
              It has the following choices: none, hostname, fqd, numeric, and user.  None means that
              no  computer  name is inserted into the audit event.  hostname is the name returned by
              the gethostname syscall. The fqd means that it takes the hostname and resolves it with
              dns for a fully qualified domain name of that machine.  Numeric is similar to fqd  ex‐
              cept it resolves the IP address of the machine. In order to use this option, you might
              want  to  test  that 'hostname -i' or 'domainname -i' returns a numeric address. Also,
              this option is not recommended if dhcp is used because you could  have  different  ad‐
              dresses over time for the same machine.  User is an admin defined string from the name
              option. The default value is none.

       name   This  is  the admin defined string that identifies the machine if user is given as the
              name_format option.

       max_log_file
              This keyword specifies the maximum file size in megabytes. When this limit is reached,
              it will trigger a configurable action. The value given must be numeric.

       max_log_file_action
              This parameter tells the system what action to take when the system has detected  that
              the  max  file  size limit has been reached. Valid values are ignore, syslog, suspend,
              rotate and keep_logs.  If set to ignore, the audit daemon does nothing.  syslog  means
              that  it  will issue a warning to syslog.  suspend will cause the audit daemon to stop
              writing records to the disk. The daemon will still be alive. The  rotate  option  will
              cause  the  audit  daemon to rotate the logs. It should be noted that logs with higher
              numbers are older than logs with lower numbers. This is the same  convention  used  by
              the  logrotate  utility.  The keep_logs option is similar to rotate except it does not
              use the num_logs setting. This prevents audit logs from being overwritten. The  effect
              is that logs accumulate and are not deleted - which will trigger the space_left_action
              if  the volume fills up. This is best used in combination with an external script used
              to archive logs on a periodic basis.

       verify_email
              This option determines if the email address given in action_mail_acct  is  checked  to
              see  if  the  domain  name  can  be  resolved.  This  option  must be given before ac‐
              tion_mail_acct or the default value of yes will be used.

       action_mail_acct
              This option should contain a valid email address or  alias.  The  default  address  is
              root.  If  the  email address is not local to the machine, you must make sure you have
              email properly configured on your machine and network. Also, this option requires that
              /usr/lib/sendmail exists on the machine.

       space_left
              If the free space in the filesystem containing log_file drops below  this  value,  the
              audit  daemon  takes  the  action  specified  by  space_left_action.   If the value of
              space_left is specified as a whole number, it is interpreted as an  absolute  size  in
              megabytes (MiB).  If the value is specified as a number between 1 and 99 followed by a
              percentage sign (e.g., 5%), the audit daemon calculates the absolute size in megabytes
              based  on  the  size  of the filesystem containing log_file.  (E.g., if the filesystem
              containing log_file is 2 gigabytes in size, and space_left is set to 25%, then the au‐
              dit daemon sets space_left to approximately 500 megabytes.  Note that this calculation
              is performed when the audit daemon starts, so if you resize the filesystem  containing
              log_file while the audit daemon is running, you should send the audit daemon SIGHUP to
              re-read the configuration file and recalculate the correct percentage.

       space_left_action
              This  parameter tells the system what action to take when the system has detected that
              it is starting to get low on disk space.  Valid values  are  ignore,  syslog,  rotate,
              email, exec, suspend, single, and halt.  If set to ignore, the audit daemon does noth‐
              ing.   syslog  means that it will issue a warning to syslog.  rotate will rotate logs,
              losing the oldest to free up space.  Email means that it will send a  warning  to  the
              email  account specified in action_mail_acct as well as sending the message to syslog.
              exec /path-to-script will execute the  script.  You  cannot  pass  parameters  to  the
              script. The script is also responsible for telling the auditd daemon to resume logging
              once its completed its action. This can be done by adding service auditd resume to the
              script.   suspend will cause the audit daemon to stop writing records to the disk. The
              daemon will still be alive. The single option will cause the audit daemon to  put  the
              computer  system  in  single user mode. The halt option will cause the audit daemon to
              shutdown the computer system. Except for rotate, it will perform this action just  one
              time.

       admin_space_left
              This  is  a  numeric  value in megabytes that tells the audit daemon when to perform a
              configurable action because the system is running low on disk space.  This  should  be
              considered  the  last chance to do something before running out of disk space. The nu‐
              meric value for this parameter should be lower than the number for space_left. You may
              also append a percent sign (e.g. 1%) to the number to have the audit daemon  calculate
              the number based on the disk partition size.

       admin_space_left_action
              This  parameter tells the system what action to take when the system has detected that
              it is low on disk space.  Valid values are ignore, syslog, rotate, email,  exec,  sus‐
              pend,  single,  and  halt.   If  set to ignore, the audit daemon does nothing.  Syslog
              means that it will issue a warning to syslog.  rotate will  rotate  logs,  losing  the
              oldest to free up space.  Email means that it will send a warning to the email account
              specified  in  action_mail_acct as well as sending the message to syslog.  exec /path-
              to-script will execute the script. You cannot  pass  parameters  to  the  script.  The
              script  is  also  responsible for telling the auditd daemon to resume logging once its
              completed its action. This can be done by adding service auditd resume to the  script.
              Suspend  will  cause  the audit daemon to stop writing records to the disk. The daemon
              will still be alive. The single option will cause the audit daemon to put the computer
              system in single user mode. The halt option will cause the audit  daemon  to  shutdown
              the computer system. Except for rotate, it will perform this action just one time.

       disk_full_action
              This  parameter tells the system what action to take when the system has detected that
              the partition to which log files are written has become full. Valid values are ignore,
              syslog, rotate, exec, suspend, single, and halt.  If set to ignore, the  audit  daemon
              will  issue  a syslog message but no other action is taken.  Syslog means that it will
              issue a warning to syslog.  rotate will rotate logs, losing  the  oldest  to  free  up
              space.   exec  /path-to-script  will execute the script. You cannot pass parameters to
              the script. The script is also responsible for telling the  auditd  daemon  to  resume
              logging g once its completed its action. This can be done by adding service auditd re‐
              sume  to  the  script.  Suspend will cause the audit daemon to stop writing records to
              the disk. The daemon will still be alive. The single option will cause the audit  dae‐
              mon  to put the computer system in single user mode.  halt option will cause the audit
              daemon to shutdown the computer system.

       disk_error_action
              This parameter tells the system what action to take whenever there  is  an  error  de‐
              tected  when  writing  audit events to disk or rotating logs. Valid values are ignore,
              syslog, exec, suspend, single, and halt.  If set to ignore, the audit daemon will  not
              take  any action.  Syslog means that it will issue no more than 5 consecutive warnings
              to syslog.  exec /path-to-script will execute the script. You cannot  pass  parameters
              to  the  script.   Suspend  will cause the audit daemon to stop writing records to the
              disk. The daemon will still be alive. The single option will cause the audit daemon to
              put the computer system in single user mode.  halt option will cause the audit  daemon
              to shutdown the computer system.

       tcp_listen_port
              This  is  a  numeric value in the range 1..65535 which, if specified, causes auditd to
              listen on the corresponding TCP port for audit records from remote systems. The  audit
              daemon  may  be linked with tcp_wrappers. You may want to control access with an entry
              in the hosts.allow and deny files. If this is deployed on a systemd based OS, then you
              may need to adjust the 'After' directive. See the note in the auditd.service file.

       tcp_listen_queue
              This is a numeric value which indicates how many pending  (requested  but  unaccepted)
              connections  are allowed.  The default is 5.  Setting this too small may cause connec‐
              tions to be rejected if too many hosts start up at exactly the same time, such as  af‐
              ter  a  power failure. This setting is only used for aggregating servers. Clients log‐
              ging to a remote server should keep this commented out.

       tcp_max_per_addr
              This is a numeric value which indicates how many concurrent connections  from  one  IP
              address  is allowed.  The default is 1 and the maximum is 1024. Setting this too large
              may allow for a Denial of Service attack on the logging server.  Also  note  that  the
              kernel has an internal maximum that will eventually prevent this even if auditd allows
              it by config. The default should be adequate in most cases unless a custom written re‐
              covery  script runs to forward unsent events. In this case you would increase the num‐
              ber only large enough to let it in too.

       use_libwrap
              This setting determines whether or not to use tcp_wrappers to discern  connection  at‐
              tempts  that are from allowed machines. Legal values are either yes, or no The default
              value is yes.

       tcp_client_ports
              This parameter may be a single numeric value or two values separated  by  a  dash  (no
              spaces  allowed).   It  indicates  which client ports are allowed for incoming connec‐
              tions.  If not specified, any port is allowed.  Allowed values are 1..65535.  For  ex‐
              ample, to require the client use a privileged port, specify 1-1023 for this parameter.
              You will also need to set the local_port option in the audisp-remote.conf file. Making
              sure that clients send from a privileged port is a security feature to prevent log in‐
              jection attacks by untrusted users.

       tcp_client_max_idle
              This parameter indicates the number of seconds that a client may be idle (i.e. no data
              from  them at all) before auditd complains. This is used to close inactive connections
              if the client machine has a problem where it cannot shutdown the  connection  cleanly.
              Note  that  this  is  a  global setting, and must be higher than any individual client
              heartbeat_timeout setting, preferably by a factor of two.  The default is zero,  which
              disables this check.

       transport
              If set to TCP, only clear text tcp connections will be used. If set to KRB5, then Ker‐
              beros 5 will be used for authentication and encryption. The default value is TCP.

       enable_krb5
              This  option  is  deprecated. Use the transport option above instead. If set to "yes",
              Kerberos 5 will be used for authentication and encryption.  The default  is  "no".  If
              this  option is set to "yes" and it follows the transport option, it will override the
              transport setting. This would be the normal expected behavior for  backwards  compati‐
              bility.

       krb5_principal
              This  is the principal for this server.  The default is "auditd".  Given this default,
              the server will look for  a  key  named  like  auditd/hostname AT EXAMPLE.COM  stored  in
              /etc/audit/audit.key  to authenticate itself, where hostname is the canonical name for
              the server's host, as returned by a DNS lookup of its IP address.

       krb5_key_file
              Location of the key for this client's principal.  Note that the key file must be owned
              by root and mode 0400.  The default is /etc/audit/audit.key

       distribute_network
              If set to "yes", network originating events will be  distributed  to  the  audit  dis‐
              patcher for processing. The default is "no".

       q_depth
              This  is  a  numeric  value that tells how big to make the internal queue of the audit
              event dispatcher. A bigger queue lets it handle a flood of events  better,  but  could
              hold  events that are not processed when the daemon is terminated. If you get messages
              in syslog about events getting dropped, increase this  value.  The  default  value  is
              2000.

       overflow_action
              This  option determines how the daemon should react to overflowing its internal queue.
              When this happens, it means that more events are being received than it can pass along
              to child processes. This error means that it is going to lose the current  event  that
              it's  trying  to dispatch. This option has the following choices: ignore, syslog, sus‐
              pend, single, and halt.  If set to ignore, the  audit  daemon  does  nothing.   syslog
              means  that it will issue a warning to syslog.  suspend will cause the audit daemon to
              stop sending events to child processes. The daemon will still be alive. The single op‐
              tion will cause the audit daemon to put the computer system in single user mode.  halt
              option will cause the audit daemon to shutdown the computer system.

       max_restarts
              This is a non-negative number that tells the audit event dispatcher how many times  it
              can try to restart a crashed plugin. The default is 10.

       plugin_dir
              This  is  the  location  that  auditd  will use to search for its plugin configuration
              files.

       end_of_event_timeout
              This is a non-negative number of seconds used by the userspace auparse() library  rou‐
              tines  and  the  aureport(8)  , ausearch(8) utilities to consider an event is complete
              when parsing an event log stream. For an event stream being processed, if the time  of
              the  current  event  is  over end_of_event_timeout seconds old, compared to co-located
              events, then the event is considered complete. See the NOTES section for more detail.

NOTES
       In a CAPP environment, the audit trail is considered so important that access to  system  re‐
       sources  must be denied if an audit trail cannot be created. In this environment, it would be
       suggested that /var/log/audit be on its own partition. This is to ensure that space detection
       is accurate and that no other process comes along and consumes part of it.

       The flush parameter should be set to sync or data.

       Max_log_file and num_logs need to be adjusted so that you get complete use of your partition.
       It should be noted that the more files that have to be rotated, the longer it  takes  to  get
       back to receiving audit events. Max_log_file_action should be set to keep_logs.

       Space_left  should  be set to a number that gives the admin enough time to react to any alert
       message and perform some maintenance to free up disk space. This would typically involve run‐
       ning the aureport -t report and moving the oldest logs to  an  archive  area.  The  value  of
       space_left  is  site  dependent since the rate at which events are generated varies with each
       deployment. The space_left_action is recommended to be set to email. If  you  need  something
       like an snmp trap, you can use the exec option to send one.

       Admin_space_left  should be set to the amount of disk space on the audit partition needed for
       admin actions to be recorded. Admin_space_left_action would be set to single so that  use  of
       the machine is restricted to just the console.

       The  disk_full_action  is  triggered  when  no  more room exists on the partition. All access
       should be terminated since no more audit capability exists. This can be set to either  single
       or halt.

       The  disk_error_action should be set to syslog, single, or halt depending on your local poli‐
       cies regarding handling of hardware malfunctions.

       Specifying a single allowed client port may make it difficult for the client to restart their
       audit subsystem, as it will be unable to recreate a connection with the same  host  addresses
       and ports until the connection closure TIME_WAIT state times out.


       Auditd events are made up of one or more records. The auditd system cannot guarantee that the
       set  of records that make up an event will occur atomically, that is the stream will have in‐
       terleaved records of different events, IE

              event0_record0
              event1_record0
              event2_record0
              event1_record3
              event2_record1
              event1_record4
              event3_record0

       The auditd system does not guarantee that the records that make up an event  will  appear  in
       order.  Thus,  when processing event streams, we need to maintain a list of events with their
       own list of records hence List of List (LOL) event processing.

       When processing an event stream we define the end of an event via

              record type = AUDIT_EOE (audit end of event type record), or
              record type = AUDIT_PROCTITLE (we note the AUDIT_PROCTITLE is always the last record),
              or
              record type = AUDIT_KERNEL (kernel events are one record events), or
              record type < AUDIT_FIRST_EVENT (only single record events appear before  this  type),
              or
              record  type  >=  AUDIT_FIRST_ANOM_MSG  (only  single  record events appear after this
              type), or
              record type >= AUDIT_MAC_UNLBL_ALLOW && record type  <=  AUDIT_MAC_CALIPSO_DEL  (these
              are also one record events), or
              for  the  stream  being  processed, the time of the event is over end_of_event_timeout
              seconds old.


FILES
       /etc/audit/auditd.conf
              Audit daemon configuration file


SEE ALSO
       auditd(8), audisp-remote.conf(5), auditd-plugins(5).


AUTHOR
       Steve Grubb

Red Hat                                      August 2018                              AUDITD.CONF(5)