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pam_xauth

pam_xauth(8)             System Administrator's Manual            pam_xauth(8)



NAME
       pam_xauth - forward xauth keys between users

SYNOPSIS
       session optional /lib/security/pam_xauth.so arguments

DESCRIPTION
       pam_xauth.so  is  designed to forward xauth keys (sometimes referred to
       as "cookies") between users.

       Without pam_xauth, when xauth is enabled and a user uses the su command
       to  assume  another  user's priviledges, that user is no longer able to
       access the original user's X display because the new user does not have
       the  key needed to access the display.  pam_xauth solves the problem by
       forwarding the key from the user running su (the source  user)  to  the
       user  whose identity the source user is assuming (the target user) when
       the session is created, and destroying the key when the session is torn
       down.

       This  means,  for example, that when you run su from an xterm sesssion,
       you will be able to run X programs without explicitly dealing with  the
       xauth command or ~/.Xauthority files.

       pam_xauth  will  only forward keys if xauth can list a key connected to
       the $DISPLAY environment variable.

       Primitive access control is provided by ~/.xauth/export in the invoking
       user's  home  directory  and  ~/.xauth/import in the target user's home
       directory.

       If a user has a ~/.xauth/import file, the user will only receive  cook-
       ies  from  users  listed  in  the file.  If there is no ~/.xauth/import
       file, the user will accept cookies from any other user.

       If a user has a .xauth/export file, the user will only forward  cookies
       to  users listed in the file.  If there is no ~/.xauth/export file, and
       the invoking user is not root, the user will  forward  cookies  to  any
       other user.  If there is no ~/.xauth/export file, and the invoking user
       is root, the user will not forward cookies to other users.

       Both the import and export files support wildcards (such as  *).   Both
       the  import and export files can be empty, signifying that no users are
       allowed.


ARGUMENTS
       debug  Turns on debugging messages sent to syslog.

       xauthpath=/usr/X11R6/bin/xauth
              Specify  the  path   the   xauth   program   (the   default   is
              /usr/X11R6/bin/xauth).

       systemuser=number
              Specify  the  highest  UID  which will be assumed to belong to a
              "system" user.  pam_xauth will refuse to forward credentials  to
              users  with  UID  less  than or equal to this number, except for
              root and the "targetuser", if specified.

       targetuser=number
              Specify a single target UID which is exempt from the  systemuser
              check.

IMPLEMENTATION DETAILS
       pam_xauth  will  work  only  if it is used from a setuid application in
       which the getuid() call returns the id of the user running the applica-
       tion,  and  for  which  PAM can supply the name of the account that the
       user is attempting to assume.  The typical application of this type  is
       su.    The   application   must   call   both   pam_open_session()  and
       pam_close_session() with the ruid set to the uid of  the  calling  user
       and  the  euid set to root, and must have provided as the PAM_USER item
       the name of the target user.

       pam_xauth calls xauth as the source user to extract the key  for  $DIS-
       PLAY,  then  calls xauth as the target user to merge the key into the a
       temporary database and later remove the database.

       pam_xauth cannot be told not to remove the keys  when  the  session  is
       closed.

SEE ALSO
       /usr/share/doc/pam*/html/index.html

FILES
       ~/.xauth/import ~/.xauth/export

BUGS
       Let's  hope  not,  but if you find any, please report them via the "Bug
       Track" link at http://bugzilla.redhat.com/bugzilla/

AUTHOR
       Nalin  Dahyabhai  <nalin@redhat.com>,  based  on  original  version  by
       Michael K. Johnson <johnsonm@redhat.com>



Red Hat Linux                      2003/7/24                      pam_xauth(8)