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- pam_xauth — PAM module to forward xauth keys between users
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- DESCRIPTION
- 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
- 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.
- 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 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.
- AUTHOR
- pam_xauth was written by Nalin Dahyabhai <nalin@redhat.com>, based on original
- version by Michael K. Johnson <johnsonm@redhat.com>.
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