pam_xauth(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | MODULE TYPES PROVIDED | RETURN VALUES | EXAMPLES | IMPLEMENTATION DETAILS | FILES | SEE ALSO | AUTHOR | COLOPHON

PAM_XAUTH(8)                Linux-PAM Manual                PAM_XAUTH(8)

NAME         top

       pam_xauth - PAM module to forward xauth keys between users

SYNOPSIS         top

       pam_xauth.so [debug] [xauthpath=/path/to/xauth] [systemuser=UID]
                    [targetuser=UID]

DESCRIPTION         top

       The pam_xauth PAM module 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(1) command to assume another user's privileges, 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(1) from an xterm
       session, you will be able to run X programs without explicitly
       dealing with the xauth(1) 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
       cookies 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.

OPTIONS         top

       debug
           Print debug information.

       xauthpath=/path/to/xauth
           Specify the path the xauth program (it is expected in
           /usr/X11R6/bin/xauth, /usr/bin/xauth, or /usr/bin/X11/xauth
           by default).

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

MODULE TYPES PROVIDED         top

       Only the session type is provided.

RETURN VALUES         top

       PAM_BUF_ERR
           Memory buffer error.

       PAM_PERM_DENIED
           Permission denied by import/export file.

       PAM_SESSION_ERR
           Cannot determine user name, UID or access users home
           directory.

       PAM_SUCCESS
           Success.

       PAM_USER_UNKNOWN
           User not known.

EXAMPLES         top

       Add the following line to /etc/pam.d/su to forward xauth keys
       between users when calling su:

           session  optional  pam_xauth.so

IMPLEMENTATION DETAILS         top

       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
       application, 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(1). 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(1) as the source user to extract the key
       for $DISPLAY, 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 to not remove the keys when the session
       is closed.

FILES         top

       ~/.xauth/import
           XXX

       ~/.xauth/export
           XXX

SEE ALSO         top

       pam.conf(5), pam.d(5), pam(8)

AUTHOR         top

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

COLOPHON         top

       This page is part of the linux-pam (Pluggable Authentication
       Modules for Linux) project.  Information about the project can be
       found at ⟨http://www.linux-pam.org/⟩.  If you have a bug report
       for this manual page, see ⟨//www.linux-pam.org/⟩.  This page was
       obtained from the tarball Linux-PAM-1.3.0.tar.bz2 fetched from
       ⟨http://www.linux-pam.org/library/⟩ on 2021-08-27.  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

Linux-PAM Manual               04/01/2016                   PAM_XAUTH(8)