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PAM_KRB5(8)		     System Manager's Manual		     PAM_KRB5(8)

NAME
     pam_krb5 -- Kerberos 5 PAM module

SYNOPSIS
     /usr/lib/pam_krb5.so

DESCRIPTION
     The Kerberos 5 service module for PAM, typically /usr/lib/pam_krb5.so, pro-
     vides  functionality for three PAM categories: authentication, account man-
     agement, and password management.	It also provides null functions for ses-
     sion management.  The pam_krb5.so module is a shared object that can be dy-
     namically loaded to provide the necessary functionality upon  demand.   Its
     path is specified in the PAM configuration file.

   Kerberos 5 Authentication Module
     The  Kerberos  5  authentication component provides functions to verify the
     identity of a user (pam_sm_authenticate()) and to set user specific creden-
     tials  (pam_sm_setcred()).   pam_sm_authenticate()  converts  the	supplied
     username  into  a	Kerberos principal, by appending the default local realm
     name.  It also supports usernames with explicit realm names.   If	a  realm
     name is supplied, then upon a successful return, it changes the username by
     mapping the principal name into a local username (calling krb5_aname_to_lo-
     calname()).  This typically just means the realm name is stripped.

     It  prompts  the user for a password and obtains a new Kerberos TGT for the
     principal.  The TGT is verified by obtaining a service ticket for the local
     host.

     When prompting for the current password, the authentication module will use
     the prompt "Password for <principal>:".

     The pam_sm_setcred() function stores the newly acquired  credentials  in  a
     credentials  cache,  and sets the environment variable KRB5CCNAME appropri-
     ately.  The credentials cache should be destroyed by  the	user  at  logout
     with kdestroy(1).

     The following options may be passed to the authentication module:

     debug	     syslog(3) debugging information at LOG_DEBUG level.

     no_warn	     suppress  warning messages to the user.  These messages in-
		     clude reasons why the user's authentication attempt was de-
		     clined.

     use_first_pass  If the authentication module is not the first in the stack,
		     and a previous module obtained the  user's  password,  that
		     password  is used to authenticate the user.  If this fails,
		     the authentication module returns failure without prompting
		     the user for a password.  This option has no effect if  the
		     authentication  module  is the first in the stack, or if no
		     previous modules obtained the user's password.

     try_first_pass  This option is similar to the use_first_pass option, except
		     that if the previously obtained password fails, the user is
		     prompted for another password.

     forwardable     Obtain forwardable Kerberos credentials for the user.

     no_ccache	     Do not save  the  obtained  credentials  in  a  credentials
		     cache.   This is a useful option if the authentication mod-
		     ule is used for services such as ftp or pop, where the user
		     would not be able to destroy them.  [This is not  a  recom-
		     mendation to use the module for those services.]

     ccache=name     Use  name	as  the  credentials cache.  name must be in the
		     form type:residual.  The special tokens `%u', to  designate
		     the  decimal  UID	of  the user; and `%p', to designate the
		     current process ID; can be used in name.

     no_user_check   Do not verify if a user exists on the  local  system.  This
		     option implies the no_ccache option because there is no se-
		     cure local uid/gid for the cache file.

   Kerberos 5 Account Management Module
     The  Kerberos 5 account management component provides a function to perform
     account management, pam_sm_acct_mgmt().  The function verifies that the au-
     thenticated principal is allowed to login to  the	local  user  account  by
     calling krb5_kuserok() (which checks the user's .k5login file).

   Kerberos 5 Password Management Module
     The  Kerberos 5 password management component provides a function to change
     passwords (pam_sm_chauthtok()).  The username supplied  (the  user  running
     the passwd(1) command, or the username given as an argument) is mapped into
     a	Kerberos  principal name, using the same technique as in the authentica-
     tion module.  Note that if a realm name was explicitly supplied during  au-
     thentication,  but  not  during  a password change, the mapping done by the
     password management module may not result in the same principal as was used
     for authentication.

     Unlike when changing a Unix password, the password management  module  will
     allow  any  user  to change any principal's password (if the user knows the
     principal's old password, of course).  Also unlike  Unix,	root  is  always
     prompted for the principal's old password.

     The  password  management	module uses the same heuristics as kpasswd(1) to
     determine how to contact the Kerberos password server.

     The following options may be passed to the password management module:

     debug	     syslog(3) debugging information at LOG_DEBUG level.

     use_first_pass  If the password management module is not the first  in  the
		     stack,  and a previous module obtained the user's old pass-
		     word, that password is used to authenticate the  user.   If
		     this  fails, the password management module returns failure
		     without prompting the user for the old password.	If  suc-
		     cessful, the new password entered to the previous module is
		     also  used  as the new Kerberos password.	If the new pass-
		     word fails, the password management module returns  failure
		     without prompting the user for a new password.

     try_first_pass  This option is similar to the use_first_pass option, except
		     that  if the previously obtained old or new passwords fail,
		     the user is prompted for them.

   Kerberos 5 Session Management Module
     The Kerberos 5 session management component provides functions to	initiate
     (pam_sm_open_session())  and  terminate  (pam_sm_close_session()) sessions.
     Since session management is not defined under Kerberos  5,  both  of  these
     functions	simply	return	success.   They are provided only because of the
     naming conventions for PAM modules.

ENVIRONMENT
     KRB5CCNAME  Location of the credentials cache.

FILES
     /tmp/krb5cc_uid  default credentials cache (uid is the decimal UID  of  the
		      user).
     $HOME/.k5login   file  containing	Kerberos principals that are allowed ac-
		      cess.

SEE ALSO
     kdestroy(1), passwd(1), syslog(3), pam.conf(5), pam(8)

NOTES
     Applications should not call  pam_authenticate()  more  than  once  between
     calls to pam_start() and pam_end() when using the Kerberos 5 PAM module.

FreeBSD 8.1			   May 3, 2010			     PAM_KRB5(8)
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