pam_krb5(5)						Standards, Environments, and Macros					       pam_krb5(5)

NAME

       pam_krb5 - authentication, account, session, and password management PAM modules for Kerberos V5

SYNOPSIS

       /usr/lib/security/pam_krb5.so.1

DESCRIPTION

       The Kerberos V5 service module for PAM provides functionality for all four PAM modules: authentication, account management, session manage-
       ment, and password management. The service module is a shared object that can be dynamically loaded to provide the necessary  functionality
       upon demand. Its path is specified in the PAM configuration file.

   Kerberos Authentication Module
       The Kerberos V5 authentication component provides functions to verify the identity of a user, pam_sm_authenticate(), and to manage the Ker-
       beros credentials cache, pam_sm_setcred().

       pam_sm_authenticate() authenticates a user principal through the Kerberos authentication service. If the authentication request is success-
       ful, the authentication service sends a ticket-granting ticket (TGT) back to the service module, which then verifies that the TGT came from
       a valid Key Distribution Center (KDC) by attempting to get a service ticket for the local host service. For  this  to  succeed,	the  local
       host's  keytab  file  (/etc/krb5/krb5.keytab)  must  contain  the  entry  for  the local host service.  For example, in the file host/host-
       name.com@REALM, hostname.com is the fully qualified local hostname and REALM is	the  default  realm  of  the  local  host  as  defined	in
       /etc/krb5/krb5.conf.  If  the  host  entry is not found in the keytab file, the authentication fails. Administrators may optionally disable
       this "strict" verification by setting the "verify_ap_req_nofail = false" in /etc/krb5/krb5.conf. See krb5.conf(4) for more details on  this
       option. This allows TGT verification to succeed in the absence of a keytab host principal entry.

       pam_sm_authenticate(3PAM) may be passed the following flag:

       PAM_DISALLOW_NULL_AUTHTOK

	   This flag is ignored. The Kerberos authentication mechanism will not allow an empty password string by default.

       pam_sm_setcred()  creates  and  modifies the user's credential cache. This function initializes the user's credential cache, if it does not
       already exist, and stores the initial credentials for later use by Kerberized network applications. The following flags may be set  in  the
       flags field. They are best described by their effect on the user's credential cache.

       PAM_ESTABLISH_CRED

	   Stores  the initial credentials in the user's credential cache so that the user may access Kerberos network services. If the credential
	   cache exists, then this function is functionally equivalent to using the PAM_REFRESH_CRED flag. That is,  the  user's  credentials  are
	   refreshed. If the credential cache does not exist, then it is created, and new credentials are stored in it.

       PAM_DELETE_CRED

	   This flag has no effect on the credential cache and always returns PAM_SUCCESS. The credential cache is not deleted because there is no
	   accurate method to determine if the credentials are needed by another process. The credential cache may be deleted with the kdestroy(1)
	   command.

       PAM_REINITIALIZE_CRED

	   Deletes  the  user's existing credential cache, if it exists, and creates a new credential cache. The new credentials are stored in the
	   new cache and the user's ticket lifetime and renewable life time values are reset.

       PAM_REFRESH_CRED

	   Extends lifetime of user's credentials. Does not wipe out the credentials cache, but instead just extends the lifetime  of  the  user's
	   TGT. Notice that this function fails if the user's renewable ticket lifetime has expired.

       The following options can be passed to the Kerberos V5 authentication module:

       debug	       Provides syslog(3C) debugging information at LOG_DEBUG level.

       nowarn	       Turns off warning messages.

   Kerberos V5 Account Management Module
       The  Kerberos  account  management component provides a function to perform account management, pam_sm_acct_mgmt(). This function checks to
       see if the pam_krb5 authentication module has noted that the user's password has not expired. The following options may be passed in to the
       Kerberos V5 account management module:

       debug	       Provides syslog(3C) debugging information at LOG_DEBUG level

       nowarn	       Turns off warning messages. Also, does not query KDC for impending password expiration information used to warn the user.

   Kerberos V5 Session Management Module
       The Kerberos V5 session management component provides functions to initiate pam_sm_open_session() and terminate pam_sm_close_session() Ker-
       beros sessions. For Kerberos V5, both pam_sm_open_session and pam_sm_close_session() are null functions, returning PAM_IGNORE.

   Kerberos V5 Password Management Module
       The Kerberos V5 password management component provides a function to change passwords, pam_sm_chauthtok(), in the Key  Distribution  Center
       (KDC) database. The following flags may be passed to pam_sm_chauthtok(3PAM):

       PAM_CHANGE_EXPIRED_AUTHTOK

	   The password service should only update the user's Kerberos password if it is expired. Otherwise, this function returns PAM_IGNORE. The
	   default behaviour is to always change the user's Kerberos password.

       PAM_PRELIM_CHECK

	   This is a null function that always returns PAM_SUCCESS.

       PAM_UPDATE_AUTHTOK

	   This flag is necessary to change the user's Kerberos password. If this flag is not set, pam_krb5 returns PAM_SYSTEM_ERR.

       The following option can be passed to the Kerberos V5 password module:

       debug	       Provides syslog(3C) debugging information at LOG_DEBUG level.

ERRORS

       The following error codes are returned for pam_sm_authenticate():

       PAM_AUTH_ERR

	   Authentication failure

       PAM_BUF_ERR

	   Memory buffer error.

       PAM_IGNORE

	   The user is "root" and the root key exists in the default keytab.

       PAM_SUCCESS

	   Successfully obtained Kerberos credentials .

       PAM_SYSTEM_ERR

	   System error.

       PAM_USER_UNKNOWN

	   An unknown Kerberos principal was requested.

       The following error codes are returned for pam_sm_setcred():

       PAM_AUTH_ERR

	   Authentication failure.

       PAM_BUF_ERR

	   Memory buffer error.

       PAM_IGNORE

	   The user is "root" and the root key exists in the default keytab.

       PAM_SYSTEM_ERR

	   System error.

       PAM_SUCCESS

	   Successfully modified the Kerberos credential cache.

       The following error codes are returned for pam_sm_acct_mgmt():

       PAM_AUTH_ERR

	   Authentication failure.

       PAM_IGNORE

	   Kerberos service module pam_sm_authenticate() was never called, or the user is "root" and the root key exists in the default keytab.

       PAM_NEW_AUTHTOK_REQD

	   Obtain new authentication token from the user.

       PAM_SERVICE_ERR

	   Error in underlying service module.

       PAM_SUCCESS

	   Kerberos principal account is valid.

       PAM_SYSTEM_ERR

	   System error.

       PAM_USER_UNKNOWN

	   An unknown Kerberos principal was requested.

       The following error code is returned for pam_sm_open_session() and pam_sm_close_session():

       PAM_IGNORE

	   These two functions are null functions in pam_krb5:

       The following error codes are returned for pam_sm_chauthtok():

       PAM_AUTH_ERR

	   Authentication failure.

       PAM_IGNORE

	   The user has not been authenticated by Kerberos service module pam_sm_authenticate(), or the user is "root" and the root key exists	in
	   the default keytab.

       PAM_NEW_AUTHTOK_REQD

	   User's Kerberos password has expired.

       PAM_SERVICE_ERR

	   Error in module. At least one input parameter is missing.

       PAM_SYSTEM_ERR

	   System error.

       PAM_USER_UNKNOWN

	   An unknown Kerberos principal was requested.

       PAM_SUCCESS

	   Successfully changed the user's Kerberos password.

EXAMPLES

       Example 1: Authenticate Users Through Kerberos as First Choice

       The  following  is  an excerpt of a sample pam.conf configuration file that authenticates users through the Kerberos authentication service
       and authenticates through the Unix login only if the Kerberos authentication fails. This arrangement is helpful	when  a  majority  of  the
       users  are  networked  by means of Kerberos and when there are only a few non-Kerberos type user accounts, such as root. The service illus-
       trated below is for dtlogin.

       dtlogin auth requisite	       pam_smartcard.so.1
       dtlogin auth requisite	       pam_authtok_get.so.1
       dtlogin auth required	       pam_dhkeys.so.1
       dtlogin auth required	       pam_unix_cred.so.1
       dtlogin auth sufficient	       pam_krb5.so.1
       dtlogin auth required	       pam_unix_auth.so.1

       Note that these changes should not be made to the existing krlogin, krsh, and ktelnet service  entries.	Those  services  require  Kerberos
       authentication, so using a seemingly sufficient control flag would not provide the necessary functionality for privacy and integrity. There
       should be no need to change those entries.

       The following entries check for password expiration when dealing with Kerberos and Unix password aging policies:

       other   account requisite       pam_roles.so.1
       other   account required        pam_unix_account.so.1
       other   account required        pam_krb5.so.1

       The following entries would change the Kerberos password of the user and continue to change the Unix login password only  if  the  Kerberos
       password change had failed:

       other   password required       pam_dhkeys.so.1
       other   password requisite      pam_authtok_get.so.1
       other   password requisite      pam_authtok_check.so.1
       other   password sufficient     pam_krb5.so.1
       other   password required       pam_authtok_store.so.1

       When  changing  Kerberos  based	user's	password, use kpasswd(1). When changing a non-Kerberos user's password, it is recommended that the
       repository is specified (-r) with the passwd(1) command.

       Example 2: Authenticate Users Through Kerberos Only

       The following example allows authentication only to users that have Kerberos-based accounts.

       dtlogin auth requisite	       pam_smartcard.so.1
       dtlogin auth requisite	       pam_authtok_get.so.1
       dtlogin auth required	       pam_dhkeys.so.1
       dtlogin auth required	       pam_unix_cred.so.1
       dtlogin auth binding	       pam_krb5.so.1
       dtlogin auth required	       pam_unix_auth.so.1

       Typically, you would have another service specified in the pam.conf file that would allow local users, such as database, web server, system
       administrator accounts, to log in to the host machine. For example, the "login" service name could be used for these users. Note that these
       users should not belong to any roles.

       The rest of the module types look similar to that shown in the previous example:

       other   account requisite       pam_roles.so.1
       other   account required        pam_unix_account.so.1
       other   account required        pam_krb5.so.1

       With binding specified in the following, it is important that non-Kerberos users specify the repository in which they reside using  the	-r
       option with the passwd(1) command. This configuration is also based on the assumptions that:

	 o  Kerberos users maintain only their Kerberos passwords;

	 o  changing  their  Unix  password is not necessary, given that they are authenticated only through their Kerberos passwords when logging
	    in.

       other   password required       pam_dhkeys.so.1
       other   password requisite      pam_authtok_get.so.1
       other   password requisite      pam_authtok_check.so.1
       other   password binding        pam_krb5.so.1
       other   password required       pam_authtok_store.so.1

       Example 3: Authenticate Through Kerberos Optionally

       This configuration is helpful when the majority of users are non-Kerberos users and would like to authenticate  through	Kerberos  if  they
       happened  to exist in the Kerberos database. The effect of this is similar to users voluntarily executing kinit(1) after they have success-
       fully logged in:

       dtlogin auth requisite	       pam_smartcard.so.1
       dtlogin auth requisite	       pam_authtok_get.so.1
       dtlogin auth required	       pam_dhkeys.so.1
       dtlogin auth required	       pam_unix_cred.so.1
       dtlogin auth required	       pam_unix_auth.so.1
       dtlogin auth optional	       pam_krb5.so.1

       The rest of the configuration is as follows:

       other   account requisite       pam_roles.so.1
       other   account required        pam_unix_account.so.1
       other   account required        pam_krb5.so.1

       other   password required       pam_dhkeys.so.1
       other   password requisite      pam_authtok_get.so.1
       other   password requisite      pam_authtok_check.so.1
       other   password required       pam_authtok_store.so.1
       other   password optional       pam_krb5.so.1

       Non-Kerberos users should specify their respective repositories by using the -r option when changing their password with the passwd(1) com-
       mand.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Evolving			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       kdestroy(1), kinit(1), kpasswd(1), passwd(1), ktkt_warnd(1M), libpam(3LIB), pam(3PAM), pam_sm(3PAM), pam_sm_acct_mgmt(3PAM), pam_sm_authen-
       ticate(3PAM), pam_sm_chauthtok(3PAM), pam_sm_close_session(3PAM), pam_sm_open_session(3PAM), pam_sm_setcred(3PAM), syslog(3C), pam.conf(4),
       attributes(5), krb5envvar(5), SEAM(5)

NOTES

       The interfaces in libpam(3LIB) are MT-Safe only if each thread within the multi-threaded application uses its own PAM handle.

       On successful acquisition of initial credentials (ticket-granting ticket), ktkt_warnd(1M) will be notified, to alert the user when the ini-
       tial credentials are about to expire.

SunOS 5.10							    22 Apr 2004 						       pam_krb5(5)