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pam_krb5 - Kerberos 5 PAM module

 

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,
      provides functionality for three PAM categories: authentication, account
      management, and password management.  It also provides null functions for
      session management.  The pam_krb5.so 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 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 cre‐
      dentials (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_localname()).  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
                      include reasons why the user’s authentication attempt was
                      declined.
 
      use_first_pass  If the authentication module is not the first in the
                      stack, and a previous module obtained the user’s pass‐
                      word, 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
                      module is used for services such as ftp or pop, where the
                      user would not be able to destroy them.  [This is not a
                      recommendation 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 desig‐
                      nate the decimal UID of the user; and ‘%p’, to designate
                      the current process ID; can be used in name.
 
    Kerberos 5 Account Management Module
      The Kerberos 5 account management component provides a function to per‐
      form account management, pam_sm_acct_mgmt().  The function verifies that
      the authenticated 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
      authentication module.  Note that if a realm name was explicitly supplied
      during authentication, 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
                      password, 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 successful, the new password entered to the previous
                      module is also used as the new Kerberos password.  If the
                      new password 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 pass‐
                      words fail, the user is prompted for them.
 
    Kerberos 5 Session Management Module
      The Kerberos 5 session management component provides functions to initi‐
      ate (pam_sm_open_session()) and terminate (pam_sm_close_session()) ses‐
      sions.  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
                       access.
      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.
 

Sections

Based on BSD UNIX
FreeBSD is an advanced operating system for x86 compatible (including Pentium and Athlon), amd64 compatible (including Opteron, Athlon64, and EM64T), UltraSPARC, IA-64, PC-98 and ARM architectures. It is derived from BSD, the version of UNIX developed at the University of California, Berkeley. It is developed and maintained by a large team of individuals. Additional platforms are in various stages of development.