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RUSH.RC(5)                             Rush User Reference                             RUSH.RC(5)

NAME
       rush.rc - configuration rules for rush.

DESCRIPTION
       The file /etc/rush.rc contains a set of rules that the rush (1) shell uses in order to de-
       termine whether the user is allowed to execute the requested command and to set up the en-
       vironment for its execution.

       Empty  lines  are ignored.  Lines beginning with a pound sign are comments and are ignored
       as well.

       A statement consists of a keyword and optional argument, separated by any amount of white-
       space.   Depending  on the keyword, the statement may treat its argument as a single value
       or as multiple values.

       If the keyword requires multiple values, its argument is split into words using  the  fol-
       lowing algorithm:

       1.     Any sequence of one or more non-whitespace characters is a word.

       2.     Any sequence of characters enclosed in single or double quotes is a word.

       3.     Words are separated by any amount of white space.

       4.     If  the keyword expects s-expressions these are treated as words, even if they con-
              tain white space.

       Arguments obtained as a result of rules (1) and (2) are subject to  backslash  interpreta-
       tion, during which the following escape sequences are replaced with single characters:

               Sequence    Replaced with
               \a          Audible bell character (ASCII 7)
               \b          Backspace character (ASCII 8)
               \e          Escape character (ASCII 27)
               \f          Form-feed character (ASCII 12)
               \n          Newline character (ASCII 10)
               \r          Carriage return character (ASCII 13)
               \t          Horizontal tabulation character (ASCII 9)
               \v          Vertical tabulation character (ASCII 11)
               \\          A single backslash
               \"          A double-quote.

       Any escape sequence not listed in this table is replaced with its second character.

       Statements  are  delimited  by newline characters.  Length of a statement line is not lim-
       ited.  To improve readability, long statements may be split over several  lines  by  using
       backslash as a last character on line.

GLOBAL STATEMENTS
       include FILE
              Include the content of the named FILE.

              If  FILE  starts with ~/, these two characters are replaced with the full path name
              of current user home directory.

              If FILE is a directory, that directory is searched for a file whose name  coincides
              with the current user name.  If such a file is found, it is included.

              In any case, if the named file does not exist, no error is reported, and parsing of
              the configuration file continues.

       include-security ARG...
              Configures the security checks that a file must pass in order to be included in the
              configuration  by  the include statement.  The arguments are a whitespace-separated
              list of check names.  The following check names are available:

              all    Enable all checks.

              owner  The file must be owned by root.

              iwgrp, groupwritablefile
                     Reject group-writable files.

              iwoth, worldwritablefile
                     Reject world-writable files.

              dir_iwgrp, groupwritabledir
                     Reject files that reside in a group writable directory.

              dir_iwoth, worldwritabledir
                     Reject files that reside in a world writable directory.

              link   The file may not be is a symbolic link to a file  residing  in  a  group  or
                     world writable directory.

       debug NUMBER
              Sets  the debugging level.  The greater is the NUMBER, the more verbose is the log-
              ging.  The debugging information is reported via syslog(3) using authpriv, priority
              debug.

              Currently, three debugging levels are implemented:

              1      A  minimum debugging level, and the only one whose messages are logged using
                     the priority notice.  At this level, rush only logs requests and  rules  se-
                     lected to handle them.

              2      List all actions executed when serving requests.

              3      Verbosely describe parsing of the configuration file.

       regex FLAGS
              Defines what kind of regular expressions will be used in subsequent command, match,
              and transform statements.

              Each flag is a word specifying some regular expression feature.  It can be preceded
              by  +  to  enable this feature (this is the default), or by - to disable it.  Valid
              flags are:

              extended
                     Use POSIX Extended Regular Expression syntax.  This is the default.

              basic  Use basic regular expressions.  Equivalent to -extended.

              icase  Do not differentiate case.  Subsequent regex matches will be  case  insensi-
                     tive.

       usage-error TEXT
              Define a textual message which is returned to the remote party if a usage error oc-
              curs.  The default is

              You are not permitted to execute this command.

       nologin-error TEXT
              Define a textual message which is returned to the remote user if there is  no  such
              user name in the password database.  The default is:

              You do not have interactive login access to this machine.

       config-error TEXT
              Define  a  textual  message which is returned to the remote party if a system error
              occurs.   The default is:

              A system error occurred while attempting to execute command.

RULES
       Statements are grouped into rules.  A rule begins with the following construct

       rule TAG
              The TAG argument is optional.  If it is given, it supplies a a (presumably  unique)
              identifier, which will be used to label this rule.  Every diagnostic regarding this
              rule will be marked with this tag.  For rules without explicit  tag,  default  tags
              will  be  supplied,  constructed by concatenating a pound character and the ordinal
              number of rule in the configuration  file,  in  decimal  notation  (rule  numbering
              starts from 1).

       The statements that can be used within a rule fall into several distinct categories.

   Conditionals
       A  conditional statement evaluates to a boolean value.  All conditionals are tested in or-
       der of their appearance in the rule and are tied together using boolean shortcut AND eval-
       uation:  if  any  of them yields false, the rest of statements is skipped and next rule is
       tried.

       command REGEX
              True, if the current command line matches regular expression  REGEX.   By  default,
              POSIX  extended  regular  expressions are used.  This, however can be changed using
              the regex (see below).

       match[N] IREGEX
              True, if the Nth word from the command line matches regular expression REGEX.   No-
              tice,  that  square brackets form part of the statement syntax.  A special symbol $
              can be used instead of N to denote the last word.

              The command line is split into words using the same rules as used in /bin/sh.

       argc OP NUM
              Compare the number of command line arguments to NUM.  The  comparison  operator  OP
              can be one of the following: = (or ==), !=, <, <=, >, >=.

       uid [OP] UID
              Compare  the  UID  of the user who started rush to UID.  The latter may be either a
              numeric UID or a name of an existing user.  The comparison operator OP has the same
              values as discussed above.  If absent, == is assumed.

       gid [OP] GID
              Compare  the  GID  of the user who started rush to GID.  It can be either a numeric
              value or a name of an existing group.  The comparison operator OP has the same val-
              ues as discussed above.  If absent, == is assumed.

       user NAMES
              Argument is a whitespace-separated list of user names.  This condition yields true,
              if the user name matches one of the listed names.  String comparisons are case-sen-
              sitive.

       group NAMES
              Argument  is  a  whitespace-separated  list  of group names.  This condition yields
              true, if the the name of any group the user is a member of matches  one  of  listed
              names.  String comparisons are case-sensitive.

   Transformations
       These statements transform the command line.

       set PATTERN
              Replaces entire command line with the expansion of PATTERN.

       set[N] PATTERN
              Replaces  the  Nth word in the command line with the expansion of PATTERN.  Notice,
              that square brackets are part of the statement syntax.

       delete[N]
              Deletes the Nth word.

       delete N M
              Deletes words between N and M, inclusive.

       transform EXPR
              Apply a sed(1) expression EXPR to entire command line.  For example, the  statement
              below adds a -t option after the command name:

                     transform s/^[^[:space:]]+/& -t/

       transform PATTERN EXPR
              Applies  the sed(1) expression EXPR to the expansion of PATTERN and replaces entire
              command line with the result.

       transform[N] EXPR
              Applies expression EXPR to the Nth word from the command line.  Notice, that square
              brackets are part of the statement syntax.

       transform[N] PATTERN EXPR
              Applies  the expression EXPR to the expansion of PATTERN and replaces N word in the
              command line with the result.

              E.g. to replace the 0th argument with the base name of the command prefixed with  a
              dash:

                     transform[0] ${^} s,.*/,-,

       map[N] FILE DELIM PATTERN KN VN DFL
              Expand  the  PATTERN  and  scan  the  disk file FILE for the record whose KNth word
              matches the expansion (words are delimited with characters from DELIM).  If  found,
              replace the Nth command line word with the VNth word from the record.

              The arguments are:

              N      Index of the word in command line.

              FILE   Name  of the map file.  It must be an absolute file name (i.e. it must start
                     with / or ~/fR.

              DELIM  A string containing allowed field delimiters.

              PATTERN
                     The value of the lookup key.  Before using,  it  is  expanded  as  described
                     above.

              KN     Number of the key field in FILE.  Fields are numbered starting from 1.

              VN     Number of the value field.

              DFL    If supplied, this value is used as a replacement value, when the key was not
                     found in @var{file}.
       The map file consists of records, separated by newline characters.  Each  record  consists
       of  fields,  separated  by delimiters given the DELIM argument.  If DELIM contains a space
       character, then fields may be delimited by any amount  of  whitespace  characters  (spaces
       and/or tabulations).  Otherwise, exactly one delimiter delimits fields.

       Fields are numbered starting from 1.

   System Actions
       System actions provide interface to the operating system.

       umask MASK
              Set  the umask.  The argument is an octal value not greater than 0777.  The default
              umask is 022.

       newgrp GID
              Changes the current group ID to GID, which is either a numeric value or a  name  of
              an existing group.  The keyword can also be spelled as newgroup.

       chroot DIR
              Change  the  root directory to DIR.  This directory will be used for file names be-
              ginning with /.  A tilde at the start of DIR is replaced with the user's  home  di-
              rectory.

       chdir DIR
              Change  to the directory DIR.  The argument is subject to tilde-expansion as in ch-
              root, above.  If both chdir and chroot  are  specified,  then  chroot  is  executed
              first.

       limits RES
              Imposes  limits on system resources.  The argument consists of commands, optionally
              separated by any amount of whitespace.  A command is a single command  letter  fol-
              lowed by a number, that specifies the limit.  The command letters are case-insensi-
              tive and coincide with those used by the shell ulimit utility.

                      Command     The limit it sets
                      A           max address space (KB)
                      C           max core file size (KB)
                      D           max data size (KB)
                      F           maximum file size (KB)
                      M           max locked-in-memory address space (KB)
                      N           max number of open files
                      R           max resident set size (KB)
                      S           max stack size (KB)
                      T           max CPU time (MIN)
                      U           max number of processes
                      L           max number of logins for this user (see below)
                      P           process priority -20..20

              If some limit cannot be set, execution of the rule aborts.

              The use of the L resource automatically enables forked mode.

   Environment
       env ARG...
              Modifies the execution environment.  Arguments are a list of  specifiers  separated
              by  any  amount  of whitespace.  Each specifier can contain references to variables
              from the inherited environment.  The reference syntax is the same as in sh(1).

              The following specifiers are allowed:

              - (a dash)
                     Clear the environment.  If used, this must be the very first argument.

              -NAME  Unset the environment variable NAME.

              -NAME=VAL
                     Unset the environment variable NAME only if its value is VAL.

              NAME   Retain the environment variable NAME.

              NAME=VALUE
                     Set the environment variable NAME to the given VALUE.

              NAME+=VALUE
                     Retain the variable NAME and append VALUE to its value.  If no such variable
                     is  present  in  the environment, it is created and VALUE is assigned to it.
                     However, if VALUE starts with a punctuation character, this character is re-
                     moved from it before the assignment.  This is convenient for using this con-
                     struct with environment variables like PATH, e.g.:
                            PATH+=:/sbin

              NAME=+VALUE
                     Retain variable VALUE and add VALUE to the beginning of its  value.   If  no
                     such  variable is defined in the environment, it is created and VALUE is as-
                     signed to it.  However, if VALUE ends with  a  punctuation  character,  this
                     character is removed from it before assignment.

   Fall-Through
       fall-through
              Declares  a fall-through rule -- a special rule that does not execute the requested
              command.  Instead, when rush encounters a matching fall-through rule, it  evaluates
              it and continues scanning its configuration for the next matching rule.  Any trans-
              formations and environment modifications found in the fall-through rule take effect
              immediately,  which  means that subsequent rules will see modified command line and
              environment.  Execution of any other actions found in the fall-through rule is  de-
              layed until a usual rule is found.

              E.g.:
                     rule default
                         umask 002
                         env - HOME USERNAME PATH
                         fall-through

   Interactive Access
       interactive
              Marks the rule it appears in as interactive.

       When  rush  is  invoked without -c option (interactive usage), it will consider only rules
       marked with interactive keywords.  This allows for providing interactive shell access.

       The default interactive rule terminates by invoking /bin/sh.

       The command name argument (argv[0]) is set to the basename of the program  being  executed
       prefixed with a dash.

       Example:

       rule login
           interactive
           group shell
           set[0] /bin/bash

   Accounting and Forked Mode
       GNU  Rush  is  able to operate in two modes, called default and forked.  When operating in
       the default mode, the process image of rush itself is overwritten by the command being ex-
       ecuted.   Thus,  when it comes to launching the requested command, the running instance of
       rush ceases to exist.

       In forked mode, rush executes the requested command in a subprocess, and remains in memory
       supervising its execution.  Once the command terminates, the main rush process exits too.

       fork BOOL
              Enable  or disable forked mode.  The values yes, on, t, true, 1 stand for true, and
              no, off, nil, false, or 0 stand for false.

       The main advantage of the forked mode is that it allows one to run  accounting,  i.e.,  to
       note who is doing what and to keep a history of invocations.  The accounting, in turn, can
       be used to limit simultaneous executions of commands, as requested by the L command in the
       limit statement (see above).

       acct BOOL
              Turn accounting mode on or off, depending on BOOL.

       Notice,  that there is no need in explicit acct on command, if you use the limit statement
       with L command, as this enables accounting implicitly.

       Most often, accounting should affect all rules and therefore it  is  normally  used  in  a
       fall-through rule at the beginning of the configuration file, e.g.:

       rule default
           acct on
           fall-through

   Notification
       post-socket URL
              After completing the command, notify the socket at URL about the fact.  This state-
              ment implies forked mode.

       Valid formats for URL are:

       inet://HOST[:PORT]
              Connect to remote HOST using TCP/IP.  HOST is the host name or IP  address  of  the
              remote  machine.  Optional PORT specifies the port number to connect to.  It can be
              either a decimal port number or a service name from /etc/services.  If absent, TCP-
              MUX (port 1) is assumed.

       unix://FILENAME, or local://FILENAME
              Connect to a UNIX socket.

       The GNU Rush notification protocol is based on TCPMUX.

       After  establishing connection, rush sends the rule tag followed by a CRLF pair.  The rule
       tag acts as a service name.  The remote party replies with a plus or minus character,  in-
       dicating  positive or negative acknowledgment, immediately followed by an optional message
       of explanation, and terminated with a CRLF.

       If positive acknowledgment is received, rush sends a single line, consisting of  the  user
       name  and  the  executed command line, separated by a single space character.  The line is
       terminated with a CRLF.

       After sending this line, rush closes the connection.

   Exit
       exit FD MESSAGE
              Write textual message to a file descriptor, given by the optional argument FD.   If
              FD is absent, the descriptor 2 (standard error) is used.

              The MESSAGE argument is subject to backslash interpretation.

   Localization
       The following configuration directives control localization.

       locale NAME
              Sets the locale name.

       locale-dir DIR
              Sets the name of the locale directory.

       text-domain NAME
              Sets the textual domain name.

SEE ALSO
       rush(1), rushlast(1), rushwho(1).

AUTHORS
       Sergey Poznyakoff

BUG REPORTS
       Report bugs to <bug-rush AT gnu.ua>.

COPYRIGHT
       Copyright (C) 2016 Sergey Poznyakoff
       License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
       This  is free software: you are free to change and redistribute it.  There is NO WARRANTY,
       to the extent permitted by law.

RUSH.RC                                  August 20, 2016                               RUSH.RC(5)

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