pam_xauth8Linux-PAM Manualpam_xauthPAM module to forward xauth keys between userspam_xauth.so
debug
xauthpath=/path/to/xauth
systemuser=UID
targetuser=UIDDESCRIPTION
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
su1 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
su1 from an xterm session, you will be able to run
X programs without explicitly dealing with the
xauth1 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
Print debug information.
Specify the path the xauth program (it is expected in
/usr/X11R6/bin/xauth,
/usr/bin/xauth, or
/usr/bin/X11/xauth by default).
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.
Specify a single target UID which is exempt from the
systemuser check.
MODULE TYPES PROVIDED
Only the session type is provided.
RETURN VALUESPAM_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
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
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
su1.
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
xauth1 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~/.xauth/importXXX~/.xauth/exportXXXSEE ALSOpam.conf5,
pam.d5,
pam8AUTHOR
pam_xauth was written by Nalin Dahyabhai <nalin@redhat.com>,
based on original version by
Michael K. Johnson <johnsonm@redhat.com>.