pam_xauth − PAM module to forward xauth keys between users

SYNOPSIS [debug] [xauthpath=/path/to/xauth] [systemuser=UID] [targetuser=UID]


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.


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.

Only the session type is provided.


Memory buffer error.


Permission denied by import/export file.


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




User not known.

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

session optional

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.





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

pam_xauth was written by Nalin Dahyabhai <>, based on original version by Michael K. Johnson <>.

More Linux Commands

pcre16_free_substring(3) Perl-compatible regular expressions
This is a convenience function for freeing the store obtained by a previous call to pcre[16|32]_get_substring() or pcre[16|32]_get_named_substring(). Its only a

ssignal(3) - software signal facility - Linux manual page...
Dont use these functions under Linux. Due to a historical mistake, under Linux these functions are aliases for raise(3) and signal(2), respectively. Elsewhere,

asctime(3) - transform date and time to broken-down time or
The ctime(), gmtime() and localtime() functions all take an argument of data type time_t, which represents calendar time. When interpreted as an absolute time v

qfcvt(3) - convert a floating-point number to a string......
The functions qecvt(), qfcvt() and qgcvt() are identical to ecvt(3), fcvt(3) and gcvt(3) respectively, except that they use a long double argument number. See e

kismet(1) Wireless sniffing and monitoring - Linux man page
Kismet is an 802.11 layer2 wireless network detector, sniffer, and intrusion detection system. Kismet will work with any wireless card which supports raw monito

ldap_strdup(3) - LDAP memory allocation routines (Man Page)
These routines are used to allocate/deallocate memory used/returned by the LDAP library. ldap_memalloc(), ldap_memcalloc(), ldap_memrealloc(), and ldap_memfree(

ping6(8) - send ICMP ECHO_REQUEST to network hosts (ManPage)
ping uses the ICMP protocols mandatory ECHO_REQUEST datagram to elicit an ICMP ECHO_RESPONSE from a host or gateway. ECHO_REQUEST datagrams (pings) have an IP a

strcoll(3) - compare two strings using the current locale...
The strcoll() function compares the two strings s1 and s2. It returns an integer less than, equal to, or greater than zero if s1 is found, respectively, to be l

lockfile(1) - conditional semaphore-file creator (Man Page)
lockfile can be used to create one or more semaphore files. If lockfile cant create all the specified files (in the specified order), it waits sleeptime (defaul

request_key(2) - Request a key from the kernel's key managem
request_key() asks the kernel to find a key of the given type that matches the specified description and, if successful, to attach it to the nominated keyring a

podchecker(1) - check the syntax of POD format documentation
podchecker will read the given input files looking for POD syntax errors in the POD documentation and will print any errors it find to STDERR. At the end, it wi

getspent_r(3) - get shadow password file entry (Man Page)...
Long ago it was considered safe to have encrypted passwords openly visible in the password file. When computers got faster and people got more security-consciou

We can't live, work or learn in freedom unless the software we use is free.