2 .\" $Id: pam_krb5.5,v 1.5 2000/01/05 00:59:56 fcusack Exp $
9 .Nd Kerberos 5 PAM module
11 .Pa /usr/lib/pam_krb5.so
13 The Kerberos 5 service module for PAM, typically
14 .Pa /usr/lib/pam_krb5.so ,
15 provides functionality for three PAM categories:
18 and password management.
19 It also provides null functions for session management.
22 module is a shared object
23 that can be dynamically loaded to provide
24 the necessary functionality upon demand.
25 Its path is specified in the
26 PAM configuration file.
27 .Ss Kerberos 5 Authentication Module
28 The Kerberos 5 authentication component
29 provides functions to verify the identity of a user
30 .Pq Fn pam_sm_authenticate
31 and to set user specific credentials
32 .Pq Fn pam_sm_setcred .
33 .Fn pam_sm_authenticate
34 converts the supplied username into a Kerberos principal,
35 by appending the default local realm name.
36 It also supports usernames with explicit realm names.
37 If a realm name is supplied, then upon a successful return, it
38 changes the username by mapping the principal name into a local username
40 .Fn krb5_aname_to_localname ) .
41 This typically just means
42 the realm name is stripped.
44 It prompts the user for a password and obtains a new Kerberos TGT for
46 The TGT is verified by obtaining a service
47 ticket for the local host.
49 When prompting for the current password, the authentication
50 module will use the prompt
51 .Dq Li "Password for <principal>:" .
55 function stores the newly acquired credentials in a credentials cache,
56 and sets the environment variable
59 The credentials cache should be destroyed by the user at logout with
62 The following options may be passed to the authentication module:
63 .Bl -tag -width ".Cm use_first_pass"
66 debugging information at
70 suppress warning messages to the user.
71 These messages include
72 reasons why the user's
73 authentication attempt was declined.
75 If the authentication module is not the first in the stack,
76 and a previous module obtained the user's password, that password is
77 used to authenticate the user.
78 If this fails, the authentication
79 module returns failure without prompting the user for a password.
80 This option has no effect if the authentication module is
81 the first in the stack, or if no previous modules obtained the
84 This option is similar to the
86 option, except that if the previously obtained password fails, the
87 user is prompted for another password.
89 Obtain forwardable Kerberos credentials for the user.
91 Do not save the obtained credentials in a credentials cache.
93 useful option if the authentication module is used for services such
94 as ftp or pop, where the user would not be able to destroy them.
96 is not a recommendation to use the module for those services.]
97 .It Cm ccache Ns = Ns Ar name
100 as the credentials cache.
103 .Ar type : Ns Ar residual .
106 to designate the decimal UID of the user;
109 to designate the current process ID; can be used in
112 Do not verify if a user exists on the local system. This option implies the
114 option because there is no secure local uid/gid for the cache file.
116 .Ss Kerberos 5 Account Management Module
117 The Kerberos 5 account management component
118 provides a function to perform account management,
119 .Fn pam_sm_acct_mgmt .
120 The function verifies that the authenticated principal is allowed
121 to login to the local user account by calling
123 (which checks the user's
126 .Ss Kerberos 5 Password Management Module
127 The Kerberos 5 password management component
128 provides a function to change passwords
129 .Pq Fn pam_sm_chauthtok .
130 The username supplied (the
133 command, or the username given as an argument) is mapped into
134 a Kerberos principal name, using the same technique as in
135 the authentication module.
136 Note that if a realm name was
137 explicitly supplied during authentication, but not during
138 a password change, the mapping
139 done by the password management module may not result in the
140 same principal as was used for authentication.
145 password, the password management module will
146 allow any user to change any principal's password (if the user knows
147 the principal's old password, of course).
151 is always prompted for the principal's old password.
153 The password management module uses the same heuristics as
155 to determine how to contact the Kerberos password server.
157 The following options may be passed to the password management
159 .Bl -tag -width ".Cm use_first_pass"
162 debugging information at
165 .It Cm use_first_pass
166 If the password management module is not the first in the stack,
167 and a previous module obtained the user's old password, that password is
168 used to authenticate the user.
169 If this fails, the password
171 module returns failure without prompting the user for the old password.
172 If successful, the new password entered to the previous module is also
173 used as the new Kerberos password.
174 If the new password fails,
175 the password management module returns failure without
176 prompting the user for a new password.
177 .It Cm try_first_pass
178 This option is similar to the
180 option, except that if the previously obtained old or new passwords fail,
181 the user is prompted for them.
183 .Ss Kerberos 5 Session Management Module
184 The Kerberos 5 session management component
185 provides functions to initiate
186 .Pq Fn pam_sm_open_session
188 .Pq Fn pam_sm_close_session
190 Since session management is not defined under Kerberos 5,
191 both of these functions simply return success.
193 only because of the naming conventions for PAM modules.
195 .Bl -tag -width "KRB5CCNAME"
197 Location of the credentials cache.
200 .Bl -tag -width ".Pa /tmp/krb5cc_ Ns Ar uid" -compact
201 .It Pa /tmp/krb5cc_ Ns Ar uid
202 default credentials cache
204 is the decimal UID of the user).
205 .It Pa $HOME/.k5login
206 file containing Kerberos principals that are allowed access.
215 Applications should not call
217 more than once between calls to
221 when using the Kerberos 5 PAM module.