pam_env -- PAM module to set/unset environment variables
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DESCRIPTION

   The pam_env PAM module allows the (un)setting of environment variables.
   Supported is the use of previously set environment variables as well as
   PAM_ITEMs such as PAM_RHOST.

   Rules for (un)setting of variables can be defined in an own config
   file. The path to this file can be specified with the conffile option.
   If this file does not exist, the default rules are taken from the
   config files /etc/security/pam_env.conf and
   /etc/security/pam_env.conf.d/*.conf. If the file
   /etc/security/pam_env.conf does not exist, the rules are taken from the
   files %vendordir%/security/pam_env.conf,
   %vendordir%/security/pam_env.conf.d/*.conf and
   /etc/security/pam_env.conf.d/*.conf in that order.

   By default rules for (un)setting of variables are taken from the config
   file /etc/security/pam_env.conf. If this file does not exist
   %vendordir%/security/pam_env.conf is used. An alternate file can be
   specified with the conffile option, which overrules all other files.

   By default rules for (un)setting of variables are taken from the config
   file /etc/security/pam_env.conf. An alternate file can be specified
   with the conffile option.

   Environment variables can be defined in a file with simple KEY=VAL
   pairs on separate lines. The path to this file can be specified with
   the envfile option. If this file has not been defined, the settings are
   read from the files /etc/environment and /etc/environment.d/*. If the
   file /etc/environment does not exist, the settings are read from the
   files %vendordir%/environment, %vendordir%/environment.d/* and
   /etc/environment.d/* in that order. And last but not least, with the
   readenv option this mechanism can be completely disabled.

   Second a file (/etc/environment by default) with simple KEY=VAL pairs
   on separate lines will be read. If this file does not exist,
   %vendordir%/etc/environment is used. With the envfile option an
   alternate file can be specified, which overrules all other files. And
   with the readenv option this can be completely disabled.

   Second a file (/etc/environment by default) with simple KEY=VAL pairs
   on separate lines will be read. With the envfile option an alternate
   file can be specified. And with the readenv option this can be
   completely disabled.

   Third it will read a user configuration file ($HOME/.pam_environment by
   default). The default file can be changed with the user_envfile option
   and it can be turned on and off with the user_readenv option.

   Since setting of PAM environment variables can have side effects to
   other modules, this module should be the last one on the stack.

   This module is only executed if the main application calls
   pam_setcred(3) or pam_open_session(3). The module does nothing and
   returns PAM_IGNORE if called by pam_authenticate(3).

OPTIONS

   conffile=/path/to/pam_env.conf
          Indicate an alternative pam_env.conf style configuration file to
          override the default. This can be useful when different services
          need different environments.

   debug
          A lot of debug information is printed with syslog(3).

   envfile=/path/to/environment
          Indicate an alternative environment file to override the
          default. The syntax are simple KEY=VAL pairs on separate lines.
          The export instruction can be specified for bash compatibility,
          but will be ignored. This can be useful when different services
          need different environments.

   readenv=0|1
          Turns on or off the reading of the file specified by envfile (0
          is off, 1 is on). By default this option is on.

   user_envfile=filename
          Indicate an alternative .pam_environment file to override the
          default. The syntax is the same as for
          /etc/security/pam_env.conf. The filename is relative to the user
          home directory. This can be useful when different services need
          different environments.

   user_readenv=0|1
          Turns on or off the reading of the user specific environment
          file. 0 is off, 1 is on. By default this option is off as user
          supplied environment variables in the PAM environment could
          affect behavior of subsequent modules in the stack without the
          consent of the system administrator.

          Due to problematic security this functionality is deprecated
          since the 1.5.0 version and will be removed completely at some
          point in the future.

EXAMPLES

   These are some example lines which might be specified in
   /etc/security/pam_env.conf.

   Set the REMOTEHOST variable for any hosts that are remote, default to
   "localhost" rather than not being set at all
      REMOTEHOST     DEFAULT=localhost OVERRIDE=@{PAM_RHOST}

   Set the DISPLAY variable if it seems reasonable
      DISPLAY        DEFAULT=${REMOTEHOST}:0.0 OVERRIDE=${DISPLAY}

   Now some simple variables
      PAGER          DEFAULT=less
      MANPAGER       DEFAULT=less
      LESS           DEFAULT="M q e h15 z23 b80"
      NNTPSERVER     DEFAULT=localhost
      PATH           DEFAULT=${HOME}/bin:/usr/local/bin:/bin\
      :/usr/bin:/usr/local/bin/X11:/usr/bin/X11
      XDG_DATA_HOME  DEFAULT=@{HOME}/share/

   Silly examples of escaped variables, just to show how they work.
      DOLLAR         DEFAULT=\$
      DOLLARDOLLAR   DEFAULT=        OVERRIDE=\$${DOLLAR}
      DOLLARPLUS     DEFAULT=\${REMOTEHOST}${REMOTEHOST}
      ATSIGN         DEFAULT=""      OVERRIDE=\@
