pam_krb5

Section: System Administrator's Manual (5)
Updated: 2006/02/06
Index Return to Main Contents

 

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 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 deprecated 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.

existing_ticket=true
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.
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, preventing any attempts to obtain new tokens on behalf of the calling 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 credentials 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 credentials 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 credentials using the KDC. This option modifies the krb4_convert option. If disabled, pam_krb5 will only attempt to obtain Kerberos 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 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.

proxiable=[true|false]
controls whether or not credentials are proxiable. If not specified, they are. This directive is deprecated in favor of the libdefaults proxiable directive.

pwhelp=
specifies the name of a text file whose contents will be displayed 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]
validate=login sshd
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
    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 ALSO

pam_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" component.

 

AUTHOR

Nalin Dahyabhai <nalin@redhat.com>


 

Index

NAME
DESCRIPTION
DIRECTIVES
EXAMPLE
FILES
SEE ALSO
BUGS
AUTHOR

linux.jgfs.net manual pages