man > rush.rc(5)

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

NAME
       rush.rc - configuration rules for remote user shell

DESCRIPTION
       The  file /etc/rush.rc contains a set of rules that the rush(8) shell uses in order to deter‐
       mine whether the user is allowed to execute the requested command and to set up the  environ‐
       ment for its execution.

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

       Except for comments and empty lines, each line of the configuration file consists of the key‐
       word and optional value, and constitutes a statement.  Exceedingly long lines  may  be  split
       across  multiple physical lines, by ending each line with a backslash immediately followed by
       a newline.  Statements fall into two major classes: section and regular statements.   A  sec‐
       tion  statement serves as a container for one or more regular statements that pursue the same
       goal, thus playing the role of a chapter in a book.  A regular statement modifies  a  certain
       aspect of the program's behavior.

       The overall file structure is as follows:

         rush 2.0

         global
           keyword value
           ...

         rule A
           keyword value
           ...

         rule B
           keyword value
           ...


       A  configuration  file  must begin with a rush statement indicating the version of the syntax
       this file uses.  Current versions of rush implement syntax version 2.0.  In  the  absence  of
       the initial rush statement, the program will treat the configuration file as written in lega‐
       cy configuration syntax (see http://www.gnu.org.ua/software/rush/manual/1.x for details).

       There  are  two  section statements: global and rule.  The global section contains statements
       configuring the behavior of the program in general.  There can be as many  global  statements
       in the configuration as you consider necessary, each of them affecting the material up to the
       next global statement, or end of the file, whichever occurs first.

       Examples  of statements that can be used in a global section are: debug, which sets the debug
       verbosity level, message, which configures error messages, etc.  See the global  section  for
       the full list.

       One  or  more  rule statements constitute the core of the configuration.  Each rule statement
       provides a recipe for serving a specific class of input commands.  When rush is invoked  with
       a  specific  command, it will scan the configuration file looking for a rule that matches the
       requested command line.  If such a rule is found, it will be applied.   Commands  that  don't
       match any rule will be rejected.

       A rule statement may be followed by a tag, an arbitrary sequence of non-whitespace characters
       serving as a label for this rule.  This sequence will be used in diagnostic messages to iden‐
       tify this rule.  In the absence of user-supplied tag, the default one will be generated, con‐
       sisting  of the # symbol followed by the ordinal number of the rule in the configuration file
       (started with 1).

       To match a particular command, each rule should contain the match statement.  Its argument is
       a conditional expression that can contain comparison and boolean operators.  The operands can
       refer to the command line using shell-like variables: $command to refer to the entire command
       line, $#, referring to the number of arguments in the command line (the command itself  being
       counted as one of the arguments), $0 meaning the command name, and $1, $2, etc., referring to
       the  particular command line arguments (arguments past the ninth one can be accessed as, e.g.
       ${10}).  For example, the following rule:

         rule
           match $command == "ls"

       will match only the ls command without arguments.

       The ~ (tilde) operator denotes regular expression matching.  For example, the following  rule
       matches ls command, optionally preceded with any path prefix:

         rule
           match $0 ~ "^(.*/)?ls$"

       Match expressions can contain terms of arbitrary complexity.  Consider the following example:

         rule
           match $0 ~ "^(.*/)?ls$" && $# == 2 \
                 && $1 !~ "^(/|/etc)$"

       This rule will match any ls command having exactly one argument, unless that argument is / or
       /etc.   Notice  the use of the !~ operator to denote the negated regular expression matching,
       and the use of backslash to split a single expression across two physical lines.

       Variables are referenced using the same syntax as in shell.  For example, ${1:-/bin}  expands
       to  the  value  of the first parameter, if it is supplied, or to the string "/bin" otherwise.
       For details. see the section REFERENCE: VARIABLE EXPANSION.

       Although important, the match statement is not mandatory in a rule statement.  If it  is  ab‐
       sent,  the rule will match any command line.  This is normally used in fall-through rules.  A
       fall-through rule applies modifications to the  command  environment.   After  applying  such
       rule,  the  scanning  resumes at the rule that follows it. Fall-through rules are marked with
       the fall-through statement.

   set
       A rule can modify the command line and environment in which it will  be  executed.   The  set
       statement  is provided for altering the command line or its parts.  It takes three arguments:
       the variable name or index, the operator and the value.  For example, the statement:

         set command = "/bin/sftp-server -u 002"

       replaces the entire command line.  To replace particular arguments, use the [N] syntax, where
       N is the index of the argument in the command line.  For example, to set the first argument:

         set [1] = "/tmp"

       The part to the right of the equals sign can contain a transformation, i.e. a string followed
       by the ~ operand and a s-expression of the form s/regexp/replacement/[flags].   Parenthesized
       groups  in  regexp  can  be  referred to in replacement using the backreference construct \N,
       where N is the 1-based ordinal number of the group.  For  example,  the  following  statement
       sets the second argument to the directory part of the first one:

         set [2] = "$1" ~ "s/(.*)\\//\\1/"

       Two  points  are  worth noticing.  First, the left operand of ~ undergoes variable expansion.
       Secondly, the right-hand side operand is quoted and therefore each backslash in it has to  be
       escaped.

       The  special  operator =~ is used if the resulted value is assigned to the same variable that
       served as its argument.  For example, the two statements below are equivalent:

         set [1] =~ "s/(.*)\\//\\1/"
         set [1] = "$1" ~ "s/(.*)\\//\\1/"

       Parenthesized groups matched by the most recent set statement remain available for use in the
       statements that follow it in the rule.  To refer to the group from the recent  matching,  use
       the  following  construct: %N.  For example, the following two statements set the first argu‐
       ment to the directory part, and second argument to the base name of the original $1 value:

         set [1] =~ "s/(.*)\\/(.*)/\\1/"
         set [2] = %2

       The set statement operates not only on positional arguments and built-in variables, but  also
       on  arbitrary user-defined variables.  A user-defined variable springs into existence when it
       first appears as a left-hand side argument to the set statement.  The name  of  the  variable
       must  follow the usual rules for variable names: it must begin with an alphabetical character
       or underscore and contain only letters, digits and underscores.  References  to  user-defined
       variables follow the same syntax as for built-in ones.

       The following example uses temporary variable temp to swap two arguments:

         set temp = $1
         set [1] = $2
         set [2] = $temp


   unset
       Variable definitions can be removed using the unset statement.  It takes variable name or po‐
       sitional argument index as its argument:

         unset temp

       When  index  is  given, the corresponding positional argument is removed and all arguments to
       the right of it are shifted one position left to occupy the released slot.  For example, giv‐
       en the command line

         scp -d -v -t /incoming

       the statement

         unset 1

       will reduce it to

         scp -v -t /incoming


   delete
       The delete statement provides a generalization of unset for positional arguments.   It  takes
       one  or  two  argument  indexes as arguments.  When used with one index, it provides the same
       functionality as unset.  When two indices are given, it deletes all arguments  between  those
       indices (inclusive).  For example, the statement

         delete 1 2

       will change the command line from the above example to

         scp -t /incoming

       Using  negative  indices,  one can indicate arguments counting from right to left.  Thus, the
       following will delete all arguments starting from the third:

         delete 3 -1


   remopt
       Whereas delete and unset remove arguments at given positions, the remopt statement allows you
       to remove specific command line options from the command line.  This is useful to  ensure  no
       potentially  harmful options can be passed by the user.  The statement takes one or two argu‐
       ments.  First argument supplies the short option letter.  For example, the following  removes
       all occurrences of the -A option:

         remopt A

       If  there  is a long-option equivalent, it can be supplied as the second argument.  For exam‐
       ple, if --all is an alias for -A, the above statement would be rewritten as:

         remopt A all

       Notice, that the initial dash or double-dash is omitted from both the short and  long  option
       designation.

       When looking for long option in the command line, remopt will recognize its possible abbrevi‐
       ations.  In the example above, eventual occurrences of --al will be removed as well.

       If  the  option takes an argument, follow the first argument by a colon.  For example, to re‐
       move occurrences of the options -r along with its arguments write

         remopt r:

       The long option equivalent can be specified as well, e.g.:

         remopt r: root

       This will recognize all possible ways of option usage in the command line, such as:  -r  ARG,
       -rARG,  --root=ARG,  or  --root ARG.  -afr ARG In each case, both the option and its argument
       will be removed, so that the modified command line will remain valid.  Short option appearing
       in a cluster will be recognized, .e.g -afr ARG will be replaced by -af.  Finally, if the  op‐
       tion takes an optional argument, follow its short letter by two colons, as in:

         remopt r:: root


   insert
       Arguments  can also be inserted at arbitrary positions.  The insert statement is provided for
       this purpose.  Its syntax is similar to set:

         insert [N] = value

       and

         insert [N] = value ~ s/regex/replace/

       where N is the position where to insert the new argument. All  arguments  starting  from  Nth
       will  be shifted one position to the right, and the value will be stored in the Nth slot.  In
       the second form, the value to be inserted is computed by applying the replacement  expression
       to value.

REFERENCE: LEXICAL STRUCTURE
       A  statement consists of a keyword and arguments, separated by any amount of whitespace.  Ar‐
       guments can be one of the following:

       Identifiers
              Identifiers begin with a letter and consist of letters, digits, underscores and  dash‐
              es.  They serve as keywords and variable names.

       Decimal numbers
              A sequence of decimal digits, optionally preceded by a minus or plus sign.

       Unquoted strings
              An  unquoted  string  is  any  contiguous sequence of any characters, except newlines,
              whitespace and the following special characters: \, ", !, =, <, >, (, ), {, },  [,  ],
              $, %, &, |, ~, #.

       Quoted strings
              A quoted string is a sequence of characters enclosed in double-quotes.  Quoted strings
              are subject to backslash interpretation, backreference interpretation and variable ex‐
              pansion.

              During  backslash  interpretation, the escape sequences are recognized and replaced as
              per table below:

                      Sequence    Replaced with
                      \a          Audible bell character (ASCII 7)
                      \b          Backspace character (ASCII 8)
                      \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.
                      \%          Percent sign

              In addition, the sequence \newline is removed from the string.   This  allows  one  to
              split long strings over several physical lines.

              During the backreference interpretation, references to parenthesized groups in regular
              expression are replaced with the actual content of the corresponding group in the most
              recently  matched  string.   A reference is %{N} where N is a decimal number.  If N is
              one digit, curly braces can be omitted: %N If the % character resulted  from  previous
              backslash interpretation, no backreference interpretation occurs.

              Strings  used in the left-hand side of a comparison expression are subject to variable
              expansion.  This is discussed later.

       Backreferences
              The construct %{N} is replaced with the substring that matched the  Nth  parenthesized
              subgroup  in  a  most recently performed regular expression match.  If N is one digit,
              curly braces can be omitted.

       Variable references
              Variable references consist of a $ sign, followed by the positional argument number or
              variable name, optionally enclosed in curly braces.  Positional arguments greater than
              9 must be enclosed in curly braces.  The variable name must follow the rules for valid
              identifiers: it must begin with a letter and consist of  letters,  digits  and  under‐
              scores.   Variable  name  in curly braces can be followed by -, =, ?, or +, optionally
              preceded by : as summarized in the table below:

                      Reference             Meaning
                      ${VAR:-WORD}          Use Default Values
                      ${VAR:=WORD}          Assign Default Values
                      ${VAR:?WORD}          Display Error if Null or Unset
                      ${VAR:+WORD}          Use Alternate Value

              where WORD stands for any valid token as described in this section.  See  the  section
              REFERENCE:  VARIABLE  EXPANSION,  for  a  detailed discussion of these forms and their
              meaning.

       Comparison and boolean operators

                      &&                    Boolean AND
                      ||                    Boolean OR
                      !                     Boolean negation
                      ==                    Equality (string or numeric)
                      !=                    Inequality (string or numeric)
                      <                     Less than
                      <=                    Less than or equal to
                      >                     Greater than
                      >=                    Greater than or equal to
                      ~                     Regexp matching
                      !~                    Negated regexp matching
                      in                    Membership in set of strings
                      group                 Membership in UNIX group
                      =                     Assignment
                      =~                    Regular expression substitution


REFERENCE: VARIABLE EXPANSION
       Most statements in the configuration file undergo variable  expansion  prior  to  their  use.
       During  variable expansion, references to variables in the string are replaced with their ac‐
       tual values.  A variable reference has two basic forms:

         $V
         ${V}

       where V is either the name of the variable (request, environment, or  user-defined),  or  the
       index  of  the  positional  variable.   The notation in curly braces serves several purposes.
       First, it is obligatory if V is an index of the  positional  variable  that  is  negative  or
       greater  than  9.   Secondly, it should be used if the variable reference is immediately fol‐
       lowed by an alphanumeric symbol, which will  otherwise  be  considered  part  of  it  (as  in
       ${home}dir).   Finally, this form allows for specifying the action to take if the variable is
       undefined or expands to an empty value.

       The following special forms are recognized:

       ${VARIABLE:-WORD}
              Use Default Values.  If VARIABLE is unset or null, the expansion of WORD is substitut‐
              ed.  Otherwise, the value of VARIABLE is substituted.

       ${VARIABLE:=WORD}
              Assign Default Values.  If VARIABLE is unset or null, the expansion  of  WORD  is  as‐
              signed to the variable.  The value of VARIABLE is then substituted.

       ${VARIABLE:?WORD}
              Display  Error  if Null or Unset.  If VARIABLE is null or unset, the expansion of WORD
              (or a message to that effect if WORD is not present) is output to the current  logging
              channel.  Otherwise, the value of VARIABLE is substituted.

       ${VARIABLE:+WORD}
              Use  Alternate Value.  If VARIABLE is null or unset, nothing is substituted, otherwise
              the expansion of WORD is substituted.

REFERENCE: STATEMENTS
       There are three global statements, two of which can contain multiple substatements:

       rush 2.0
              Declares the version of the syntax this configuration file is written in.   This  must
              be  the  first statement in the configuration file.  If this statement is missing, the
              configuration file will be treated as legacy configuration file from previous versions
              of GNU rush.  For the discussion of the legacy configuration  file,  please  refer  to
              http://www.gnu.org.ua/software/rush/manual/1.x.

       global Defines global settings.

       rule [TAG]
              Contains a set of rules for a certain class of input command lines.

   global
       Introduces global settings.  This statement is followed by one or more substatements.  Global
       settings  end  at  the  nearest rule statement that follows.  They remain in effect until the
       next global statement is encountered which alters them.

       The following statements may appear in this section.

       expand-undefined BOOL
              Controls how undefined variables are expanded.  If BOOL is true, references  to  unde‐
              fined  variables are replaced with empty values.  If it is false (the default), an er‐
              ror message is issued and program terminates.

              Any of the following values can be used as a synonym for true: yes, on, t, 1.

              The following values can be used as synonyms for false: no, off, nil, 0.

       debug NUM
              Set debugging level.  The bigger NUM is, the more verbose is the logging.  The  debug‐
              ging information is reported via syslog at facility authpriv, priority debug.

       sleep-time NUM
              Set  the time in seconds to sleep before exiting on error.  This statement is intended
              as a measure against brute-force attacks.  Default sleep time is 5 seconds.

       message CLASS TEXT
              Define a textual message which is returned to the remote party if an error of the giv‐
              en CLASS occurs.  Valid classes are:

           usage-error
                  This error is reported when rush has been invoked improperly.   The  default  text
                  is:

                  "You are not permitted to execute this command."

           nologin-error
                  A  message  which  is returned if there is no such user name in the password data‐
                  base.  Defaults to:

                  "You are not permitted to execute this command."

           config-error
                  Define a textual message which is returned if the configuration file contained er‐
                  rors.  Default is:

                  "Local configuration error occurred."

           system-error
                  Define a textual message which is returned if a system error occurs.  Default is:

                  "A system error occurred while attempting to execute command."

       regexp FLAG [FLAG...]
              Configure the type of regular expressions to be used by subsequent match, set, and in‐
              sert statements.  Each FLAG is a word specifying a regular expression feature.  It can
              be preceded by a plus sing to enable this feature (this is the default), or by the mi‐
              nus sign to disable it.  Valid flags are:

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

           basic  Use basic regular expressions.  Equivalent to -extended.

           icase or ignore-case
                  Do not differentiate case.  Subsequent regex matches will be case insensitive.

       include-security FLAG [FLAG...]
              Configure the security checks for include files.  Valid flags are:

           all    Enable all checks.

           owner  The file must be owned by root.

           iwgrp or groupwritablefile
                  Forbid group writable files.

           iwoth or worldwritablefile
                  Forbid world writable files.

           dir_iwgrp or groupwritabledir
                  Forbid files that reside in group writable directories.

           dir_iwoth or worldwritabledir
                  Forbid files that reside in world writable directories.

           link   Forbid symbolic links to files residing in group or world writable directories.

       Each of the above keywords can be prefixed by no, which reverses its  meaning.   The  special
       keyword none disables all checks.

       acct-umask MASK
              Set umask used when accessing accounting database files.  Default value is 022.

       acct-dir-mode MODE
              Set mode bits for the accounting directory.  The argument is the mode in octal.

       acct-file-mode MODE
              Set mode bits for the wtmp and utmp files.

   rule
       Defines  a  rule.  This is a block statement, which means that all statements located between
       it and the next rule statement (or end of file, whichever occurs first) modify the definition
       of that rule.

       The syntax is:

         rule TAG

       Optional TAG argument supplies the identifier for that rule.  It is used in  diagnostic  mes‐
       sages.   If  tag is missing, rush will supply a default one, which is constructed by concate‐
       nating the # character and the ordinal number of rule in the configuration file,  in  decimal
       notation.  Rule numbering starts from 1.

       A rule can contain the following statements:

       match EXPR
              Defines  conditions  that decide whether the rule matches the particular request.  The
              EXPR argument is a comparison expression.  It can be a simple comparison expression or
              a boolean expression involving several other expressions.

              A simple expression is either a comparison or a membership test.  A comparison has the
              general syntax

                lhs op rhs

              where lhs and rhs are operands and op is the operation.  The lhs is  either  a  string
              (quoted  or unquoted), or a variable reference.  The rhs is a string or number.  Prior
              to evaluating simple expression, its LHS undergoes variable expansion.   In  contrast,
              the RHS operand is always treated verbatim.

              The comparison operator OP is one of the following:

                      ==                    Equality (string or numeric)
                      !=                    Inequality (string or numeric)
                      <                     Less than
                      <=                    Less than or equal to
                      >                     Greater than
                      >=                    Greater than or equal to
                      ~                     Regexp matching
                      !~                    Negated regexp matching

              Two membership tests are available.  The in test has the form

                LHS in ( STRING ... )

              and evaluates to true if LHS matches one of the strings in parentheses.  LHS undergoes
              variable expansion and backreference interpretation prior to comparison.

              The group test has the following syntax:

                group GRP

              It  returns  true if the requesting user is a member of the group GRP.  Several groups
              can be given in parentheses:

                group (GRP ...)

              in which case the test return true if the user is a member of at least one of the men‐
              tioned groups.

              Compound boolean expression combine one or more expressions using logical operators

                      &&                    Boolean AND
                      ||                    Boolean OR
                      !                     Boolean negation


       set NAME = VALUE
              Sets the variable NAME to VALUE,  which  undergoes  backreference  interpretation  and
              variable expansion.

       set [N] = VALUE
              Sets the command line argument N to VALUE

       set NAME = VALUE ~ S-EXPR
              Applies  the sed(1)-like search-and-replace expression S-EXPR to VALUE and assigns the
              result to the variable NAME.  Both VALUE and S-EXPR are subject to variable  expansion
              and backreference interpretation.

       set [N] = VALUE ~ S-EXPR
              Similar to the above, but assigns the result to the Nth command line argument.

       set NAME =~ S-EXPR
              This is a shortcut for

                set NAME = $NAME ~ S-EXPR

              i.e.  it  applies the search-and-replace expression S-EXPR to the current value of the
              variable NAME and stores the resulting string as its new value.

       set [N] =~ S-EXPR
              A shortcut for

                set [N] = $N ~ S-EXPR


       The S-EXPR, is a sed replace expression of the form:

         s/REGEXP/REPLACE/[FLAGS]

       where REGEXP is a regular expression, REPLACE is a replacement for each  part  of  the  input
       that  matches REGEXP and optional FLAGS are flag letters that control the substitution.  Both
       REGEXP and REPLACE are described in sed(1).

       As in sed, you can give several replace expressions, separated by semicolons.

       The supported FLAGS are:

       g      Apply the replacement to all matches to the REGEXP, not just the first.

       i      Use case-insensitive matching.

       x      REGEXP is an extended regular expression.

       NUMBER Only replace the NUMBERth match of the REGEXP.

       Notice, that the POSIX standard does not specify what should happen when you mix  the  g  and
       NUMBER modifiers.  Rush follows the GNU sed implementation in this regard, so the interaction
       is  defined to be: ignore matches before the NUMBERth, and then match and replace all matches
       from the NUMBERth on.

       Also notice, that usually S-EXPR is a quoted string, and as such it is subject  to  backslash
       interpretation.   It is therefore important to properly escape backslashes, especially in the
       REPLACE part.  E.g.

         set bindir = $program ~ "s/(.*)\\//\\1/"


       insert [N] = VALUE
              Shift command line arguments starting from the Nth one position to the right and store
              VALUE in the Nth slot. VALUE is subject to variable expansion and backreference inter‐
              pretation.

       insert [N] = VALUE ~ S-EXPR
              Shift command line arguments starting from the Nth one position to the right, apply S-
              EXPR to VALUE and store the result in the Nth slot.  Both S-EXPR and VALUE are subject
              to variable expansion and backreference interpretation.

       unset NAME
              Unset the variable NAME.

       unset N
              Unset the positional argument N (an integer number greater than 0), shifting  the  re‐
              maining arguments one position left.  This is the same as delete N.

       remopt SOPT
              Remove  from  the  command line all occurrences of the short option described by SOPT.
              The SOPT argument is the short option letter, optionally followed by a colon  if  that
              option takes a mandatory argument, or by two colons if it takes an optional argument.

       remopt SOPT LOPT
              Same  as the above.  LOPT supplies the long option equivalent for the short option de‐
              scribed by SOPT.

       delete N
              Delete Nth argument.

       delete I J
              Delete arguments between I and J, inclusive.

       map NAME FILE DELIM KEY KN VN
              This statement uses file lookup to find a new value for the variable NAME.   The  FILE
              argument  supplies the name of the map file.  It must begin with / or ~/.  Before use,
              the file permissions and ownership are checked using the criteria supplied in the  in‐
              clude-security statement (see the global section).

              The  map  file  consists of records, separated by newline characters.  Each record, in
              turn, consists of fields, separated by characters listed in the DELIM argument.  If it
              contains a space character, then fields may be delimited by any amount  of  whitespace
              characters  (spaces  and/or  tabulations).   Otherwise, exactly one character delimits
              fields.  Fields within a record are numbered starting from 1.

              The map action operates as follows.  First, variable expansion and  backreference  in‐
              terpretation  is  performed  on  the  KEY argument.  The result will be used as actual
              lookup key.  Then, FILE is scanned for a record whose KNth field  matches  the  lookup
              key.   If such a record is found, the value of its VNth field is assigned to the vari‐
              able.  Otherwise, if DEFAULT is supplied, it is assigned to the variable.   Otherwise,
              the variable remains unchanged.

       map [N] FILE DELIM KEY KN VN DEFAULT
              Same as above, but the result of the lookup is assigned to Nth argument.

       The following statements modify command execution environment:

       clrenv Clear the environment.

       keepenv NAME ...
              Retain  the  listed  variables.   This  statement  should  be used in conjunction with
              clrenv.

              Argument is a whitespace delimited list of variables to retain.  Each element  in  the
              list  can  be either a variable name, or a shell-style globbing pattern, in which case
              all variables matching that pattern will be retained, or a variable name  followed  by
              an equals sign and a value, in which case it will be retained only if its actual value
              equals  the  supplied one.  For example, to retain only variables with names beginning
              with 'LC_':

                keepenv "LC_*"


       setenv NAME = VALUE
              Set the environment variable NAME.  The VALUE argument is subject to  variable  expan‐
              sion and backreference interpretation.

              For example, to modify the 'PATH' value:

                setenv PATH = "$PATH:/opt/bin"


       unsetenv NAME ...
              Unset environment variables.  See keepenv for a discussion of arguments.

       evalenv STRING
              Performs backslash interpretation, backreference interpretation and variable expansion
              on  STRING  and discards the result.  This statement is similar to the shell's "colon"
              statement.

       The following statements are system actions.  They provide interface to the operating system.

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

       newgrp GROUP-ID
              Change  the current group ID to GROUP-ID, which is either a numeric value or a name of
              an existing group.

       newgroup GROUP-ID
              Alias to the above.

       chroot DIR
              Change the root directory to DIR.  The argument is subject to tilde and  variable  ex‐
              pansions  and  backreference  interpretation.   During tilde expansion, a tilde at the
              start of string is replaced with the absolute pathname of the user's home directory.

       chdir DIR
              Change to the directory DIR.  The argument is subject to tilde and variable expansions
              and backreference interpretation.  If both chdir and chroot are specified,  chroot  is
              applied first.

       limits RES
              Impose  limits  on system resources, as defined by RES.  The argument consists of com‐
              mands, optionally separated by any amount of whitespace.  A command is a  single  com‐
              mand  letter  followed by a number, that specifies the limit.  The command letters are
              case-insensitive and coincide with those used by the shell ulimit utility:

           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 (negative = high priority)

       If some limit cannot be set, execution of the rule aborts.  In particular, the L limit can be
       regarded as a condition, rather than an action.  Setting limit L5 succeeds only  if  no  more
       than 5 rush instances are simultaneously running for the same user.  This can be used to lim‐
       it the number of simultaneously open sessions.

       The  use  of L resource automatically enables forked mode.  See the subsection Accounting and
       forked mode for details.

       fall-through or fallthrough
              Declare a fall-through rule.  After evaluating such a rule, rush continues rule match‐
              ing process from the next rule in the configuration.  Any modifications to the request
              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 delayed until a matching rule is found.

              Fall-through rules are often used to set default values for subsequent rules.

   Accounting and forked mode
       GNU rush is able to operate in two modes, which we call 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.

       There  is also another operation mode, which we call forked mode.  When running in this mode,
       rush executes the requested command in a subprocess, and remains in  memory  supervising  its
       execution.  Once the command terminates, rush exits.

       One  advantage of the forked mode is that it allows you to keep 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 to limit statement
       (see above).

       acct BOOL
              Turn accounting mode on or off, depending on BOOL.  The argument can  be  one  of  the
              following:  yes,  on, t, true, or 1, to enable accounting, and no, off, nil, false, 0,
              to disable it.

       fork BOOL
              Enable or disable forked mode.  See acct for a description of BOOL.  Enabling account‐
              ing turns the fork mode as well.  This statement is mainly designed as a way  of  dis‐
              abling the forked mode for a given rule.

   Post-process notification
       Rush  can  be  configured  to send a notification over INET or UNIX sockets, after completing
       user request.  It is done using the following statement:

       post-socket URL
              Notify URL about completing the user request.  This statement implies forked mode.

       Allowed formats for URL are:

       inet://HOSTNAME[:PORT]
              Connect to remote host HOSTNAME using TCP/IP.  HOSTNAME 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 PORT is  ab‐
              sent, tcpmux (port 1) is assumed.

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

       The notification protocol is based on TCPMUX (RFC 1078).  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 single character indicating positive (+) or negative (-) acknowledgment,
       optionally followed by a 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.

       The post-process notification feature can be used to schedule execution of some actions after
       certain rules.

   Exit rule
       exit FD TEXT
              Write textual message TEXT to file descriptor FD.

       exit TEXT
              Write textual message TEXT to standard error.  Similar to

                exit 2 TEXT

              In both cases the TEXT argument can be either a quoted string, or an identifier.

       If  it  is a quoted string, it is subject to backreference interpretation and variable expan‐
       sion.

       If TEXT is an identifier, it must be the name of a predefined error message (see the list  in
       the discussion of the message statement in global section, above).

   Interactive access
       Sometimes  it  may  be  necessary  to allow some group of users limited access to interactive
       shells.  GNU rush contains provisions for such usage.  When it is invoked without '-c' it as‐
       sumes interactive usage.  In this case only rules explicitly marked as interactive  are  con‐
       sidered, the rest of rules is ignored.

       interactive BOOL
              If  BOOL  is  true  (see  the acct statement above for allowed values), this statement
              marks the rule it appears in as interactive.  This rule will match only if rush is in‐
              voked without command line arguments.

       Unless command line transformations are  applied,  interactive  rule  finishes  by  executing
       /bin/sh.   The  first  word in the command line (argv[0]) is normally set to the base name of
       the command being executed prefixed by a minus character.

       An example

         rule login
           interactive true
           group rshell
           map program /etc/rush.shell : ${user} 1 2
           set [0] = ${program} ~ "s|^.*/||;s,^,-r,"

         rule nologin
           interactive true
           exit You don't have interactive access to this machine.

       The login rule will match interactive user requests if the user is  a  member  of  the  group
       rshell.   It  looks  up the shell to use for this in the file /etc/rush.shell.  This map file
       consists of two fields, separated by a colon.  If the shell is found, its base name, prefixed
       with -r, will be used as argv[0] (this indicates a restricted login shell).   Otherwise,  the
       trap rule nologin will be matched, which will output the given diagnostics message and termi‐
       nate rush.

   Localization
       The following statement allow you to provide translations (localizations) for the messages in
       your rush configuration:

       locale NAME
              Set  the  locale name.  To specify empty locale, use "" as NAME (recall that empty lo‐
              cale name means to use the value of the environment variable 'LC_ALL' as locale name).

       locale-dir NAME
              Set the name of the locale directory.

       text-domain NAME
              Set the textual domain name.

       An example:

         rule l10n
           locale "pl_PL"
           text-domain "rush-config"
           fall-through


   include
       The include statement forces inclusion of the named file in that file location:

       include FILE

       The statement is evaluated when parsing the configuration file, which means that FILE  under‐
       goes  only tilde expansion: the two characters ~/ appearing at the beginning of file name are
       replaced with the full path name of the current user's 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 con‐
       figuration file continues.

       Before including the file rush checks if it is secure, using the  criteria  set  in  the  in‐
       clude-security statement.  See its description in the global section, above.

       The include statement can be used only within a rule.  The included file may not contain rule
       and global statements.

SEE ALSO
       rush(8), rushlast(1), rushwho(1).

AUTHORS
       Sergey Poznyakoff

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

COPYRIGHT
       Copyright © 2016-2019 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                                     July 1, 2019                                  RUSH.RC(5)
rush.rc(5)
NAME DESCRIPTION
set unset delete remopt -rARG, --root=ARG, or --root ARG. -afr ARG In each case, both the option and its argument insert rush 2.0 global rule Accounting and forked mode Post-process notification Exit rule Interactive access Localization include
SEE ALSO AUTHORS BUG REPORTS COPYRIGHT

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