ACCESS.CONF(5) Linux-PAM Manual ACCESS.CONF(5)
NAME
access.conf - the login access control table file
DESCRIPTION
The /etc/security/access.conf file specifies (user/group, host),
(user/group, network/netmask), (user/group, tty), (user/group,
X-$DISPLAY-value), or (user/group, pam-service-name) combinations for
which a login will be either accepted or refused.
When someone logs in, the file access.conf is scanned for the first
entry that matches the (user/group, host) or (user/group,
network/netmask) combination, or, in case of non-networked logins, the
first entry that matches the (user/group, tty) combination, or in the
case of non-networked logins without a tty, the first entry that matches
the (user/group, X-$DISPLAY-value) or (user/group, pam-service-name/)
combination. The permissions field of that table entry determines
whether the login will be accepted or refused.
Each line of the login access control table has three fields separated
by a ":" character (colon):
permission:users/groups:origins
The first field, the permission field, can be either a "+" character
(plus) for access granted or a "-" character (minus) for access denied.
The second field, the users/group field, should be a list of one or more
login names, group names, uid, gid, or ALL (which always matches). To
differentiate user entries from group entries, group entries should be
written with brackets, e.g. (group) or (gid).
The third field, the origins field, should be a list of one or more tty
names (for non-networked logins), X $DISPLAY values or PAM service names
(for non-networked logins without a tty), host names, domain names
(begin with "."), host addresses, internet network numbers (end with
"."), internet network addresses with network mask (where network mask
can be a decimal number or an internet address also), ALL (which always
matches) or LOCAL. The LOCAL keyword matches when the user connects
without a network connection (e.g., su, login). A connection through the
loopback device (e.g., ssh user@localhost) is considered a network
connection, and thus, the LOCAL keyword does not match.
If supported by the system you can use @netgroupname in host or user
patterns. The @@netgroupname syntax is supported in the user pattern
only and it makes the local system hostname to be passed to the netgroup
match call in addition to the user name. This might not work correctly
on some libc implementations causing the match to always fail.
The EXCEPT operator makes it possible to write very compact rules.
If the nodefgroup is not set, the group file is searched when a name
does not match that of the logged-in user. Only groups are matched in
which users are explicitly listed. However the PAM module does not look
at the primary group id of a user.
The "#" character at start of line (no space at front) can be used to
mark this line as a comment line.
EXAMPLES
These are some example lines which might be specified in
/etc/security/access.conf.
User root should be allowed to get access via cron, X11 terminal :0,
tty1, ..., tty5, tty6.
+:root:crond :0 tty1 tty2 tty3 tty4 tty5 tty6
User root should be allowed to get access from hosts which own the IPv4
addresses. This does not mean that the connection have to be a IPv4 one,
a IPv6 connection from a host with one of this IPv4 addresses does work,
too.
+:root:192.168.200.1 192.168.200.4 192.168.200.9
+:root:127.0.0.1
User root should get access from network 192.168.201. where the term
will be evaluated by string matching. But it might be better to use
network/netmask instead. The same meaning of 192.168.201. is
192.168.201.0/24 or 192.168.201.0/255.255.255.0.
+:root:192.168.201.
User root should be able to have access from hosts foo1.bar.org and
foo2.bar.org (uses string matching also).
+:root:foo1.bar.org foo2.bar.org
User root should be able to have access from domain foo.bar.org (uses
string matching also).
+:root:.foo.bar.org
User root should be denied to get access from all other sources.
-:root:ALL
A user with uid 1003 and a group with gid 1000 should be allowed to get
access from all other sources.
+:(1000) 1003:ALL
User foo and members of netgroup admins should be allowed to get access
from all sources. This will only work if netgroup service is available.
+:@admins foo:ALL
User john and foo should get access from IPv6 host address.
+:john foo:2001:db8:0:101::1
User john and foo should get access from IPv6 link local host address.
+:john foo:fe80::de95:818c:1b55:7e42%eth1
User john should get access from IPv6 net/mask.
+:john:2001:db8:0:101::/64
Members of group wheel should be allowed to get access from all sources.
+:(wheel):ALL
Disallow console logins to all but the shutdown, sync and all other
accounts, which are a member of the wheel group.
-:ALL EXCEPT (wheel) shutdown sync:LOCAL
All other users should be denied to get access from all sources.
-:ALL:ALL
NOTES
The default separators of list items in a field are space, ',', and
tabulator characters. Thus conveniently if spaces are put at the
beginning and the end of the fields they are ignored. However if the
list separator is changed with the listsep option, the spaces will
become part of the actual item and the line will be most probably
ignored. For this reason, it is not recommended to put spaces around the
':' characters.
An IPv6 link local host address must contain the interface identifier.
IPv6 link local network/netmask is not supported.
Hostnames should be written as Fully-Qualified Host Name (FQHN) to avoid
confusion with device names or PAM service names.
SEE ALSO
pam_access(8), pam.d(5), pam(7)
AUTHORS
Original login.access(5) manual was provided by Guido van Rooij which
was renamed to access.conf(5) to reflect relation to default config
file.
Network address / netmask description and example text was introduced by
Mike Becher <mike.becher@lrz-muenchen.de>.
[FIXME: source] 06/29/2025 ACCESS.CONF(5)
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