pam_krb5
pam_krb5(8) System Administrator’s Manual pam_krb5(8)
NAME
pam_krb5 - Kerberos 5 authentication
SYNOPSIS
auth required /lib/security/pam_krb5.so
session optional /lib/security/pam_krb5.so
account sufficient /lib/security/pam_krb5.so
password sufficient /lib/security/pam_krb5.so
DESCRIPTION
The pam_krb5.so module is designed to allow smooth integration of Ker-
beros 5 password-checking for applications which use PAM. It creates
session-specific credential cache files, and can obtain Kerberos IV
credentials using a krb524 service or a v4-capable KDC. If the system
is an AFS client, it will also attempt to obtain tokens for the local
cell.
When a user logs in, the module’s authentication function performs a
simple password check and, if possible, obtains Kerberos 5 and Ker-
beros IV credentials, caching them for later use. When the applica-
tion requests initialization of credentials (or opens a session), the
usual ticket files are created. When the application subsequently
requests deletion of credentials or closing of the session, the module
deletes the ticket files. When the application requests account man-
agement, if the module did not participate in authenticating the user,
it will signal libpam to ignore the module. If the module did partic-
ipate in authenticating the user, it will check for an expired user
password and verify the user’s authorization using the .k5login file
of the user being authenticated, which is expected to be accessible to
the module.
ARGUMENTS
debug turns on debugging via syslog(3). Debugging messages are
logged with priority LOG_DEBUG.
addressless
tells pam_krb5.so to obtain credentials without address lists.
This may be necessary if your network uses NAT, and should oth-
erwise not be used. This option is deprecated in favor of the
noaddresses flag in the libdefaults section of krb5.conf(5).
hosts=host
tells pam_krb5.so to obtain credentials using the address of
the given host in addition to the addresses of interfaces on
the local workstation. For example, if your workstation is
behind a masquerading firewall, specifying the firewall’s out-
ward-facing address here should allow Kerberos authentication
to succeed. This option is deprecated in favor of the
extra_addresses flag in the libdefaults section of
krb5.conf(5).
afs_cells=cell1.example.com
tells pam_krb5.so to obtain tokens for cell1.example.com and
cell2.example.com, in addition to the local cell, for the user.
banner=Kerberos
tells pam_krb5.so how to identify itself when users attempt to
change their passwords. The default setting is "Kerberos 5".
ccache_dir=/tmp
tells pam_krb5.so which directory to use for storing credential
caches. The default setting is /tmp.
external
external=sshd
tells pam_krb5.so to use Kerberos credentials provided by the
calling application during session setup. This is most often
useful for obtaining a krb4 ticket.
forwardable
tells pam_krb5.so that credentials it obtains should be forward-
able. This option is deprecated in favor of the forwardable
option in the libdefaults section of krb5.conf(5).
keytab=/etc/krb5.keytab
tells pam_krb5.so the location of a keytab to use when validating
credentials obtained from KDCs.
krb4_convert
tells pam_krb5.so to obtain Kerberos IV credentials for users, in
addition to Kerberos 5 credentials.
no_krb4_convert_524
tells pam_krb5.so not to try to obtain Kerberos IV credentials
for users using the krb524 service. This option modifies the
krb4_convert option. If this option is specified, pam_krb5 will
only attempt to obtain Kerberos IV credentials using the KDC,
unless no_krb4_use_as_req is also specified.
no_krb4_use_as_req
tells pam_krb5.so not to try to obtain Kerberos IV credentials
for users using the KDC. This option modifies the krb4_convert
option. If this option is specified, pam_krb5 will only attempt
to obtain Kerberos IV credentials using the krb524 service,
unless no_krb4_convert_524 is also specified.
minimum_uid=0
tells pam_krb5.so to ignore authentication attempts by users with
UIDs below the specified number.
no_user_check
tells pam_krb5.so to not check if a user exists on the local sys-
tem, to skip authorization checks using the user’s .k5login file,
and to create ccache files owned by the current process’s UID.
This is useful for situations where a non-privileged server pro-
cess needs to use Kerberized services on behalf of remote users
who may not have local access. Note that such a server should
have an encrypted connection with its client in order to avoid
allowing the user’s password to be eavesdropped.
proxiable
tells pam_krb5.so that credentials it obtains should be proxi-
able. This option is deprecated in favor of the proxiable option
in the libdefaults section of krb5.conf(5).
realm=realm
overrides the default realm set in /etc/krb5.conf, which
pam_krb5.so will attempt to authenticate users to.
renew_lifetime=36000
sets the default renewable lifetime for credentials. This option
is deprecated in favor of the renew_lifetime option in the libde-
faults section of krb5.conf(5).
ticket_lifetime=36000
sets the default lifetime for credentials.
tokens
signals that pam_krb5.so should obtain tokens during authentica-
tion 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.
try_first_pass
tells pam_krb5.so to check the previously-entered password as
with use_first_pass, but to prompt the user for another one if
the previously-entered one fails. This is the default mode of
operation.
use_first_pass
tells pam_krb5.so to get the user’s entered password as it was
stored by a module listed earlier in the stack, usually pam_unix
or pam_pwdb, instead of prompting the user for it.
use_authtok
tells pam_krb5.so to never prompt for new passwords when changing
passwords. This is useful if you are using pam_cracklib.so to
try to enforce use of less-easy-to-guess passwords.
validate
tells pam_krb5.so to verify that the TGT obtained from the
realm’s servers has not been spoofed. Note that the process
which is performing authentication must be able to read the
keytab in order for validation to be possible.
FILES
/etc/krb5.conf
SEE ALSO
pam_krb5(5) krb5.conf(5)
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"
component.
AUTHOR
Nalin Dahyabhai <nalin@redhat.com>
Red Hat Linux 2008/04/10 pam_krb5(8)
