access.conf - the login access control table file
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, or
ALL (which always matches). To
differentiate user entries from group entries, group entries should be written
with brackets, e.g.
(group).
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 if and only
if
pam_get_item(3), when called with an
item_type of
PAM_RHOST, returns NULL or an empty string (and therefore the
origins field is compared against the return value of
pam_get_item(3) called with an
item_type of
PAM_TTY or,
absent that,
PAM_SERVICE).
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.
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
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 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
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.
pam_access(8),
pam.d(5),
pam(7)
Original
login.access(5) manual was provided by Guido van Rooij which was
renamed to to reflect relation to default config file.
Network address / netmask description and example text was introduced by Mike
Becher <
[email protected]>.