pam_access.so [
debug
] [
nodefgroup
] [
noaudit
] [
accessfile=file
] [
fieldsep=sep
] [
listsep=sep
]
The pam_access PAM module is mainly for access management. It provides logdaemon style login access control based on login names, host or domain names, internet addresses or network numbers, or on terminal line names in case of non-networked logins.
By default rules for access management are taken from config file
/etc/security/access.conf if you don't specify
another file.
If Linux PAM is compiled with audit support the module will report when it denies access based on origin (host or tty).
The /etc/security/access.conf file specifies
(user/group, host),
(user/group, network/netmask) or
(user/group, tty)
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. 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), 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. LOCAL
keyword matches if and only if the PAM_RHOST is
not set and <origin> field is thus set from
PAM_TTY or 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.
-
accessfile=/path/to/access.conf Indicate an alternative
access.confstyle configuration file to override the default. This can be useful when different services need different access lists.-
debug A lot of debug information is printed with syslog(3).
-
noaudit Do not report logins from disallowed hosts and ttys to the audit subsystem.
-
fieldsep=separators This option modifies the field separator character that pam_access will recognize when parsing the access configuration file. For example: fieldsep=| will cause the default `:' character to be treated as part of a field value and `|' becomes the field separator. Doing this may be useful in conjunction with a system that wants to use pam_access with X based applications, since the PAM_TTY item is likely to be of the form "hostname:0" which includes a `:' character in its value. But you should not need this.
-
listsep=separators This option modifies the list separator character that pam_access will recognize when parsing the access configuration file. For example: listsep=, will cause the default ` ' (space) and `\t' (tab) characters to be treated as part of a list element value and `,' becomes the only list element separator. Doing this may be useful on a system with group information obtained from a Windows domain, where the default built-in groups "Domain Users", "Domain Admins" contain a space.
-
nodefgroup User tokens which are not enclosed in parentheses will not be matched against the group database. The backwards compatible default is to try the group database match even for tokens not enclosed in parentheses.
- PAM_SUCCESS
Access was granted.
- PAM_PERM_DENIED
Access was not granted.
- PAM_IGNORE
pam_setcredwas called which does nothing.- PAM_ABORT
Not all relevant data or options could be gotten.
- PAM_USER_UNKNOWN
The user is not known to the system.
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
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 logdaemon style login access control scheme was designed and implemented by Wietse Venema. The pam_access PAM module was developed by Alexei Nogin <alexei@nogin.dnttm.ru>. The IPv6 support and the network(address) / netmask feature was developed and provided by Mike Becher <mike.becher@lrz-muenchen.de>.