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
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.
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=princi‐
palname.
always_allow_localname = true|false|service [...]
tells pam_krb5.so, when performing an authorization check using
the target user's .k5login file, to always allow access when the
principal name being authenticated maps to the local user's name
(as configured using the auth_to_local_names and auth_to_local
settings in krb5.conf(5), if your implementation provides those
settings). Otherwise, if the file exists and can be read, but
the principal is not explicitly listed, access is typically
denied. This setting is disabled by default.
armor = true|false|service [...]
attempt to use armoring when communicating with the KDC. This
option is currently mainly only useful for testing, as the
keytab method should not be expected to work when the module is
called from an unprivileged process, and the pkinit method
requires that the KDC is properly configured to offer anonymous
PKINIT, and that the client is also properly configured to trust
the KDC's CA. The default is false.
armor_strategy = keytab,pkinit
controls how the module will attempt to obtain tickets for use
as armor. The value should be a comma-separated list of methods.
Supported methods include ketyab and pkinit. The default is
keytab,pkinit.
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-spe‐
cific credential cache. This value is treated as a template,
and these sequences are substituted:
%u login name
%U login UID
%p principal name
%r principal's realm name
%h home directory
%d the default ccache directory (as set with ccache_dir)
%P the current process ID
%% literal '%'
If the resulting template does not end with "XXXXXX", a suffix
will be added to the configured value. If not set, the module
attempts to read the default used by libkrb5 from krb5.conf(5),
and if one is not found, the default is
FILE:%d/krb5cc_%U_XXXXXX".
chpw_prompt = true|false|service [...]
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.
cred_session=true|false|service [...]
specifies that pam_krb5 should create and destroy credential
caches, as it does when the calling application opens and closes
a PAM session, when the calling application establishes and
deletes PAM credentials. This is done to compensate for appli‐
cations which expect to create a credential cache but which
don't use PAM session management. It is usually a harmless
redundancy in applications which don't require it, so this
option is enabled by default except for this list of services:
"sshd".
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 sshd-
rekey gssftp".
ignore_afs=true|false|service [...]
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_k5login=true|false|service [...]
specifies which other not pam_krb5 should skip checking the
user's .k5login file to verify that the principal name of the
client being authenticated is authorized to access the user
account. (Actually, the check is performed by a function
offered by the Kerberos library, which controls which files it
will consult.) The default is false, which causes pam_krb5 to
perform the check.
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\\(.*)$ $1@EXAMPLE.COM" would
map any user with a name of the form "EXAMPLE\whatever" to a
principal 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.
preauth_options =
controls the preauthentication options which pam_krb5 passes to
libkrb5, if the system-defaults need to be overridden. The list
is treated as a template, and these sequences are substituted:
%u login name
%U login UID
%p principal name
%r principal's realm name
%h home directory
%d the default ccache directory (as set with ccache_dir)
%P the current process ID
%% literal '%'
A list of recognized values should be listed in the kinit(1)
manual page as parameters for its -X option.
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.
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 information, 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 false during password changes, and true otherwise.
If the calling application does not properly support PAM conver‐
sations (possibly due to limitations of a network protocol which
it is serving), this may be need to be disabled for that appli‐
cation to prevent it from supplying the user's current password
in a password-changing situation when a new password is called
for.
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 neces‐
sary.
token_strategy = rxk5,2b[,...]
controls how, and using which format, pam_krb5.so should attempt
to set AFS tokens for the user's session. By default, the mod‐
ule is configured with "token_strategy = 2b". Recognized strat‐
egy names include:
rxk5 rxk5 (requires OpenAFS 1.6 or later)
2b rxkad "2b" (requires OpenAFS 1.2.8 or later)
trace = true|false|service [...]
turns on libkrb5's library tracing. Trace messages are logged
to syslog(3) with priority LOG_DEBUG.
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 mod‐
ule is configured with "use_shmem = sshd".
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.
validate_user_user = true|false|service [...]
specifies whether or not, when attempting validation of the TGT,
to attempt user-to-user authentication using a previously-
obtainted TGT in the default ccache if validation can't be per‐
formed using a keytab. The default is false.
EXAMPLE
[appdefaults]
pam = {
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
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 2013/09/21 pam_krb5(5)
