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 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.
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).
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 $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 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 2001/9/27 pam_xauth(8)