USERFILE(5)

NAME
USERFILE - UUCP pathname permissions file

DESCRIPTION
The USERFILE file specifies the file system directory trees that are accessible to local users and to remote systems via UUCP.

Each line in USERFILE is of the form:

[loginname],[system] [ c ] pathname [pathname] [pathname]

The first two items are separated by a comma; any number of spaces or tabs may separate the remaining items. Lines beginning with a `#' character are comments. A trailing `\' indicates that the next line is a continuation of the current line.

Loginname is a login (from /etc/passwd) on the local machine.

System is the name of a remote machine, the same name used in L.sys(5).

c denotes the optional callback field. If a c appears here, a remote machine that calls in will be told that callback is requested, and the conversation will be terminated. The local system will then immediately call the remote host back.

Pathname is a pathname prefix that is permissible for this login and/or system.

When uucico(8) runs in master role or uucp(1) or uux(1) are run by local users, the permitted pathnames are those on the first line with a loginname that matches the name of the user who executed the command. If no such line exists, then the first line with a null (missing) loginname field is used. (Beware: uucico is often run by the superuser or the UUCP administrator through cron(8).)

When uucico runs in slave role, the permitted pathnames are those on the first line with a system field that matches the hostname of the remote machine. If no such line exists, then the first line with a null (missing) system field is used.

Uuxqt(8) works differently; it knows neither a login name nor a hostname. It accepts the pathnames on the first line that has a null system field. (This is the same line that is used by uucico when it cannot match the remote machine's hostname.)

A line with both loginname and system null, for example

    , /usr/spool/uucppublic

can be used to conveniently specify the paths for both "no match" cases if lines earlier in USERFILE did not define them. (This differs from older Berkeley and all USG versions, where each case must be individually specified. If neither case is defined earlier, a "null" line only defines the "unknown login" case.)

To correctly process loginname on systems that assign several logins per UID, the following strategy is used to determine the current loginname:

1)  If the process is attached to a terminal, a login entry exists in /var/run/utmp, and the UID for the utmp name matches the current real UID, then loginname is set to the utmp name.

2)  If the USER environment variable is defined and the UID for this name matches the current real UID, then loginname is set to the name in USER.

3)  If both of the above fail, call getpwuid(3) to fetch the first name in /etc/passwd that matches the real UID.

4)  If all of the above fail, the utility aborts.

FILES
/etc/uucp/USERFILE
/etc/uucp/UUAIDS/USERFILE	USERFILE example

SEE ALSO
uucp(1), uux(1), L.cmds(5), L.sys(5), uucico(8), uuxqt(8)

NOTES
The UUCP utilities (uucico, uucp, uux, and uuxqt) always have access to the UUCP spool files in /usr/spool/uucp, regardless of pathnames in USERFILE.

If uucp is listed in L.cmds(5), then a remote system will execute uucp on the local system with the USERFILE privileges for its login, not its hostname.

Uucico freely switches between master and slave roles during the course of a conversation, regardless of the role it was started with. This affects how USERFILE is interpreted.

WARNING
USERFILE restricts access only on strings that the UUCP utilities identify as being pathnames. If the wrong holes are left in other UUCP control files (notably L.cmds), it can be easy for an intruder to open files anywhere in the file system. Arguments to uucp(1) are safe, since it assumes all of its non-option arguments are files. Uux(1) cannot make such assumptions; hence, it is more dangerous.

BUGS
The UUCP Implementation Description explicitly states that all remote login names must be listed in USERFILE. This requirement is not enforced by Berkeley UUCP, although it is by USG UUCP.

Early versions of 4.2BSD uuxqt(8) erroneously check UUCP spool files against the USERFILE pathname permissions. Hence, on these systems it is necessary to specify /usr/spool/uucp as a valid path on the USERFILE line used by uuxqt. Otherwise, all uux(1) requests are rejected with a "PERMISSION DENIED" message.