Manual Reference Pages  - pam_krb5 (5)

NAME

pam_krb5 - Kerberos 5 authentication

CONTENTS

Description
Directives
Example
Files
Bugs
Author

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.

chpw_prompt=[true|false]
chpw_prompt=screensaver tells pam_krb5.so to allow expired passwords to be changed during 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 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.

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 setting of the validate option. There is no default setting.

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.

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 principal name.

pwhelp = filename 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|service [...] specifies whether or not to attempt validation of the TGT using the local keytab. The default is true. The libdefaults verify_ap_req_nofail setting can affect whether or not errors reading 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 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>


Red Hat Linux pam_krb5 (5) 2006/02/06
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