pam_krb5(5) System Administrator's Manual pam_krb5(5)NAMEpam_krb5 - Kerberos 5 authentication
DESCRIPTION
pam_krb5.so reads its configuration information from the appdefaults
section of krb5.conf(5). You should read the krb5.conf(5) man page
before continuing here. The module expects its configuration informa‐
tion to be in the pam subsection of the appdefaults section.
DIRECTIVES
debug=[true|false]
turns on debugging via syslog(3). Debug messages are logged
with priority LOG_DEBUG.
debug_sensitive=[true|false]
turns on debugging of sensitive information via syslog(3).
Debug messages are logged with priority LOG_DEBUG.
addressless=[true|false]
if set, requests a TGT with no address information. This can be
necessary if you are using Kerberos through a NAT, or on systems
whose IP addresses change regularly. This directive is depre‐
cated in favor of the libdefaults noaddresses directive.
afs_cells=cell1.example.com cell2.example.com
tells pam_krb5.so to obtain tokens for cell1.example.com and
cell2.example.com, in addition to the local cell and the cell
which contains the user's home directory, for the user. The
module will guess the principal name of the AFS service for the
listed cells, or it can be specified by listing cells in the
form cellname=principalname.
banner=Kerberos 5
specifies what sort of password the module claims to be changing
whenever it is called upon to change passwords. The default is
Kerberos 5.
ccache_dir=/tmp
specifies the directory in which to place credential cache
files.
chpw_prompt=[true|false]
chpw_prompt=screensaver
tells pam_krb5.so to allow expired passwords to be changed dur‐
ing authentication attempts. While this is the traditional
behavior exhibited by "kinit", it is inconsistent with the
behavior expected by PAM, which expects authentication to
(appear to) succeed, only to have password expiration be flagged
by a subsequent call to the account management function. Some
applications which don't handle password expiration correctly
will fail unconditionally if the user's password is expired, and
this flag can be used to attempt to work around this bug in
those applications. The default is false.
existing_ticket=true
tells pam_krb5.so to accept the presence of pre-existing Ker‐
beros credentials provided by the calling application in the
default credential cache as sufficient to authenticate the user,
and to skip any account management checks.
DANGER! Unless validation is also in use, it is relatively easy
to produce a credential cache which looks "good enough" to fool
pam_krb5.so.
external=true
external=sshd ftp
tells pam_krb5.so to use Kerberos credentials provided by the
calling application during session setup. This is most often
useful for obtaining AFS tokens or a krb4 ticket.
forwardable=[true|false]
controls whether or not credentials are forwardable. This
directive is deprecated in favor of the libdefaults forwardable
directive.
hosts=hostnames
specifies which other hosts credentials obtained by pam_krb5
will be good on. If your host is behind a firewall, you should
add the IP address or name that the KDC sees it as to this list.
This directive is deprecated in favor of the libdefaults
extra_addresses directive.
ignore_afs=[true|false]
tells pam_krb5.so to completely ignore the presence of AFS, pre‐
venting any attempts to obtain new tokens on behalf of the call‐
ing application.
ignore_unknown_principals=[true|false]
ignore_unknown_spn=[true|false]
ignore_unknown_upn=[true|false]
specifies which other not pam_krb5 should return a PAM_IGNORE
code to libpam instead of PAM_USER_UNKNOWN for users for whom
the determined principal name is expired or does not exist.
initial_prompt=[true|false]
tells pam_krb5.so whether or not to ask for a password before
attempting authentication. If one is needed and pam_krb5.so has
not prompted for it, the Kerberos library should trigger a
request for a password.
keytab=FILE:/etc/krb5.keytab
specifies the name of a keytab file to search for a service key
for use in validating TGTs.
krb4_convert=[true|false]
controls whether or not pam_krb5 tries to get Kerberos IV cre‐
dentials from the KDC (or using the krb524d service on the KDC)
and create ticket files with them. Unless you've converted
everything on your network over to use Kerberos 5, you'll want
to leave this set to true. Note that this may require valid
Kerberos IV configuration data to be present in /etc/krb.conf
and /etc/krb.realms. This option is poorly named. This option
is forced to true if AFS is detected.
krb4_convert_524=[true|false]
controls whether or not pam_krb5 tries to get Kerberos IV cre‐
dentials using the krb524d service. This option modifies the
krb4_convert option. If disabled, pam_krb5 will only attempt to
obtain Kerberos IV credentials using the KDC (unless the
krb4_use_as_req option is also disabled).
krb4_use_as_req=[true|false]
controls whether or not pam_krb5 tries to get Kerberos IV cre‐
dentials using the KDC. This option modifies the krb4_convert
option. If disabled, pam_krb5 will only attempt to obtain Ker‐
beros IV credentials using the krb524d service (unless the
krb4_convert_524 option is also disabled).
mappings=[regex1 regex2]
specifies that pam_krb5 should derive the user's principal name
from the Unix user name by first checking if the user name
matches regex1, and formulating a principal name using regex2.
For example, "mappings = EXAMPLE\(.*) $1@EXAMPLE.COM" would map
any user with a name of the form "EXAMPLE\whatever" to a princi‐
pal name of "whatever@EXAMPLE.COM". This is primarily targeted
at allowing pam_krb5 to be used to authenticate users whose user
information is provided by winbindd(8). This will frequently
require the reverse to be configured by setting up an
auth_to_local rule elsewhere in krb5.conf(5).
minimum_uid=0
specifies the minimum UID of users being authenticated. If a
user with a UID less than this value attempts authentication,
the request will be ignored.
multiple_ccaches=true|false|service [...]
specifies that pam_krb5 should maintain multiple credential
caches for applications that both set credentials and open a PAM
session, but which set the KRB5CCNAME variable after doing only
one of the two. This option is usually not necessary for most
services.
novalidate = service [...]
specifies a list of services for which validation of the TGT
using the local keytab should not be attempted, despite the set‐
ting of the validate option. There is no default setting.
proxiable=[true|false]
controls whether or not credentials are proxiable. If not spec‐
ified, they are. This directive is deprecated in favor of the
libdefaults proxiable directive.
null_afs=true|false|service [...]
tells pam_krb5.so, when it attempts to set tokens, to try to get
credentials for services with names which resemble afs@REALM
before attempting to get credentials for services with names
resembling afs/cell@REALM. The default is to assume that the
cell's name is the instance in the AFS service's Kerberos prin‐
cipal name.
pwhelp = filename
specifies the name of a text file whose contents will be dis‐
played to clients who attempt to change their passwords. There
is no default.
renew_lifetime=36000
default renewable lifetime. This specifies how much time you
have after getting credentials to renew them. This directive is
deprecated in favor of the libdefaults renew_lifetime directive.
subsequent_prompt=[true|false]
controls whether or not pam_krb5.so will allow the Kerberos
library to ask the user for a password or other information, if
the previously-entered password is somehow insufficient for
authenticating the user.
ticket_lifetime=36000
default credential lifetime.
tokens=[true|false]
tokens=imap ftp
signals that pam_krb5.so should create an AFS PAG and obtain
tokens during authentication in addition to session setup. This
is primarily useful in server applications which need to access
a user's files but which do not open PAM sessions before doing
so.
use_shmem=true
use_shmem=sshd ftp
tells pam_krb5.so to pass credentials from the authentication
service function to the session management service function
using shared memory for specific services.
validate = true|false|service [...]
specifies whether or not to attempt validation of the TGT using
the local keytab. The default is true. The libdefaults ver‐
ify_ap_req_nofail setting can affect whether or not errors read‐
ing the keytab which are encountered during validation will be
suppressed.
EXAMPLE
[appdefaults]
pam = {
ticket_lifetime = 36000
renew_lifetime = 36000
forwardable = true
krb4_convert = true
validate = true
ccache_dir = /var/tmp
external = sshd
tokens = imap ftpd
TEST.EXAMPLE.COM = {
debug = true
afs_cells = testcell.example.com othercell.example.com
}
}
FILES
/etc/krb5.conf
SEE ALSOpam_krb5(8)BUGS
Probably, but let's hope not. If you find any, please file them in the
bug database at http://bugzilla.redhat.com/ against the "pam_krb5" com‐
ponent.
AUTHOR
Nalin Dahyabhai <nalin@redhat.com>
Red Hat Linux 2006/02/06 pam_krb5(5)
