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pam_krb5(5) System Administrator's Manual pam_krb5(5)

NAME
pam_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 information to be in the pam subsec-
tion of the appdefaults section.

DIRECTIVES
Directives which take a true, false, or a PAM service name can also be selectively disabled for specific PAM services
using the related "no_" option (exceptions to "debug = true" can be made using "no_debug", for example).

debug = true|false|service [...]
turns on debugging via syslog(3). Debug messages are logged with priority LOG_DEBUG.

debug_sensitive = true|false|service [...]
turns on debugging of sensitive information via syslog(3). Debug messages are logged with priority LOG_DEBUG.

addressless = true|false|service [...]
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 deprecated in favor of the libdefaults
noaddresses directive.

afs_cells = cell.example.com [...]
tells pam_krb5.so to obtain tokens for the listed cells, 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 = /var/tmp
specifies the directory in which to place credential cache files. The default is /tmp.

ccname_template = KEYRING:krb5cc_%U_%P

ccname_template = FILE:%d/krb5cc_%U_XXXXXX
specifies the location in which to place the user's session-specific credential cache. This value is treated as a
template, and these sequences are substituted:
%u login name
%U login UID
%p principal name
%r realm name
%h home directory
%d the default ccache directory (as set with ccache_dir)
%P the current process ID
%% literal '%'

The default is FILE:%d/krb5cc_%U_XXXXXX".

chpw_prompt = true|false|service [...]
tells pam_krb5.so to allow expired passwords to be changed during authentication attempts. While this is the tra-
ditional 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 uncon-
ditionally 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|false|service [...]
tells pam_krb5.so to accept the presence of pre-existing Kerberos credentials provided by the calling application
in the default credential cache as sufficient to authenticate the user, and to skip any account management checks.
The default is false.

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|false|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. The default is "sshd".

forwardable = true|false|service [...]
controls whether or not credentials are forwardable. This directive is deprecated in favor of the libdefaults
forwardable directive.

hosts = hostname [...]
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|service [...]
tells pam_krb5.so to completely ignore the presence of AFS, preventing any attempts to obtain new tokens on behalf
of the calling application.

ignore_unknown_principals=true|false|service [...]

ignore_unknown_spn=true|false|service [...]

ignore_unknown_upn=true|false|service [...]
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|service [...]
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

keytab = FILE:/etc/krb5.keytab imap=FILE:/etc/imap.keytab
specifies the name of a keytab file to search for a service key for use in validating TGTs. The location can be
specified on a per-service basis by specifying a list of locations in the form pam_service=location. The default
is FILE:/etc/krb5.keytab.

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\(.*)
$1ATEXAMPLE.COM" would map any user with a name of the form "EXAMPLE\whatever" to a principal name of "what-
everATEXAMPLE.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.

preauth_options =
controls the preauthentication options which pam_krb5 passes to libkrb5, if the system-defaults need to be over-
ridden. The list is treated as a template, and these sequences are substituted:
%u login name
%U login UID
%p principal name
%r realm name
%h home directory
%d the default ccache directory (as set with ccache_dir)
%P the current process ID
%% literal '%'

proxiable = true|false|service [...]
controls whether or not credentials are proxiable. If not specified, 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 resem-
ble 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 principal name.

pwhelp = filename
specifies the name of a text file whose contents will be displayed to clients who attempt to change their pass-
words. There is no default.

renew_lifetime = 36000
default renewable lifetime, in seconds. 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|service [...]
controls whether or not pam_krb5.so will allow the Kerberos library to ask the user for a password or other infor-
mation, if the previously-entered password is somehow insufficient for authenticating the user. This is commonly
needed to allow a user to log in when that user's password has expired. The default is true.

If the calling application does not properly support PAM conversations (possibly due to limitations of a network
protocol which it is serving), this may be need to be disabled for that application to prevent it from supplying
the user's current password in a password-changing situations when a new password is called for.

ticket_lifetime = 36000
default credential lifetime, in seconds.

tokens = true|false|service [...]
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. For correctly-written applications, this flag is not necessary.

token_strategy = rxk5,2b[,...]
controls how, and using which format, pam_krb5.so should attept to set AFS tokens for the user's session. By
default, the module is configured with "token_strategy = v4,524,2b,rxk5". Recognized strategy names include:
rxk5 rxk5 (requires OpenAFS 1.6 or later)
2b rxkad "2b" (requires OpenAFS 1.2.8 or later)

use_shmem = true|false|service [...]
tells pam_krb5.so to pass credentials from the authentication service function to the session management service
function using shared memory for specific services. By default, the module is configured with "use_shmem = sshd".

validate = true|false|service [...]
specifies whether or not to attempt validation of the TGT. The default is false.

EXAMPLE
[appdefaults]
pam = {
ticket_lifetime = 36000
renew_lifetime = 36000
forwardable = 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
keytab = FILE:/etc/krb5.keytab httpd=FILE:/etc/httpd.keytab
}
}

FILES
/etc/krb5.conf