1pam_krb5(8) System Administrator's Manual pam_krb5(8)
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6 pam_krb5 - Kerberos 5 authentication
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10 auth required //usr/$LIB/security/pam_krb5.so
11 session optional //usr/$LIB/security/pam_krb5.so
12 account sufficient //usr/$LIB/security/pam_krb5.so
13 password sufficient //usr/$LIB/security/pam_krb5.so
14
17 The pam_krb5.so module is designed to allow smooth integration of Ker‐
18 beros 5 password-checking for applications which use PAM. It creates
19 session-specific credential caches. If the system is an AFS client, it
20 will also attempt to obtain tokens for the local cell, the cell which
21 contains the user's home directory, and any explicitly-configured
22 cells.
23 When a user logs in, the module's authentication function performs a
25 simple password check and, if possible, obtains Kerberos 5 credentials,
26 caching them for later use. When the application requests initializa‐
27 tion of credentials (or opens a session), the usual ticket files are
28 created. When the application subsequently requests deletion of cre‐
29 dentials or closing of the session, the module deletes the ticket
30 files. When the application requests account management, if the module
31 did not participate in authenticating the user, it will signal libpam
32 to ignore the module. If the module did participate in authenticating
33 the user, it will check for an expired user password and verify the
34 user's authorization using the .k5login file of the user being authen‐
35 ticated, which is expected to be accessible to the module.
36
39 debug turns on debugging via syslog(3). Debugging messages are logged
40 with priority LOG_DEBUG.
41 debug_sensitive
44 turns on debugging of sensitive information via syslog(3).
45 Debug messages are logged with priority LOG_DEBUG.
46 afs_cells=cell.example.com[,...]
49 tells pam_krb5.so to obtain tokens for the named cells, in addi‐
50 tion to the local cell, for the user. The module will guess the
51 principal name of the AFS service for the named cells, or it can
52 be specified by giving cell in the form cellname=principalname.
53 always_allow_localname
56 tells pam_krb5.so, when performing an authorization check using
57 the target user's .k5login file, to always allow access when the
58 principal name being authenticated maps to the local user's name
59 (as configured using the auth_to_local_names and auth_to_local
60 settings in krb5.conf(5), if your implementation provides those
61 settings). Otherwise, if the file exists and can be read, but
62 the principal is not explicitly listed, access is typically
63 denied. This setting is disabled by default.
64 armor = true|false|service [...]
67 attempt to use armoring when communicating with the KDC. This
68 option is currently mainly only useful for testing, as the
69 keytab method should not be expected to work when the module is
70 called from an unprivileged process, and the pkinit method
71 requires that the KDC is properly configured to offer anonymous
72 PKINIT, and that the client is also properly configured to trust
73 the KDC's CA. The default is false.
74 armor_strategy = keytab,pkinit
77 controls how the module will attempt to obtain tickets for use
78 as armor. The value should be a comma-separated list of meth‐
79 ods. Supported methods include ketyab and pkinit. The default
80 is keytab,pkinit.
81 banner=Kerberos 5
84 tells pam_krb5.so how to identify itself when users attempt to
85 change their passwords. The default setting is "Kerberos 5".
86 ccache_dir=/tmp
89 tells pam_krb5.so which directory to use for storing credential
90 caches. The default setting is /tmp.
91 ccname_template=DIR:/run/user/%U/krb5cc_XXXXXX
94 specifies the location in which to place the user's session-spe‐
95 cific credential cache. This value is treated as a template,
96 and these sequences are substituted:
97 %u login name
98 %U login UID
99 %p principal name
100 %r principal's realm name
101 %h home directory
102 %d the default ccache directory (as set with ccache_dir)
103 %P the current process ID
104 %% literal '%'
105 If the resulting template does not end with "XXXXXX", a suffix
106 will be added to the configured value. If not set, the module
107 attempts to read the default used by libkrb5 from krb5.conf(5),
108 and if one is not found, the default is
109 DIR:/run/user/%U/krb5cc_XXXXXX".
110 chpw_prompt
113 tells pam_krb5.so to allow expired passwords to be changed dur‐
114 ing authentication attempts. While this is the traditional
115 behavior exhibited by "kinit", it is inconsistent with the
116 behavior expected by PAM, which expects authentication to
117 (appear to) succeed, only to have password expiration be flagged
118 by a subsequent call to the account management function. Some
119 applications which don't handle password expiration correctly
120 will fail unconditionally if the user's password is expired, and
121 this flag can be used to attempt to work around this bug in
122 those applications. The default is false.
123 cred_session
126 specifies that pam_krb5 should create and destroy credential
127 caches, as it does when the calling application opens and closes
128 a PAM session, when the calling application establishes and
129 deletes PAM credentials. This is done to compensate for appli‐
130 cations which expect to create a credential cache but which
131 don't use PAM session management. It is usually a harmless
132 redundancy in applications which don't require it, so this
133 option is enabled by default except for these services: "sshd".
134 external
137 external=sshd
139 tells pam_krb5.so to use Kerberos credentials provided by the
140 calling application during session setup. This is most often
141 useful for obtaining AFS tokens.
142 ignore_afs=true|false|service [...]
145 tells pam_krb5.so to completely ignore the presence of AFS, pre‐
146 venting any attempts to obtain new tokens on behalf of the call‐
147 ing application.
148 ignore_k5login
151 specifies that pam_krb5 should skip checking the user's .k5login
152 file to verify that the principal name of the client being
153 authenticated is authorized to access the user account. (Actu‐
154 ally, the check is performed by a function offered by the Ker‐
155 beros library, which controls which files it will consult.) The
156 default is to perform the check.
157 ignore_unknown_principals
160 ignore_unknown_spn
162 ignore_unknown_upn
164 specifies that not pam_krb5 should return a PAM_IGNORE code to
165 libpam instead of PAM_USER_UNKNOWN for users for whom the deter‐
166 mined principal name is expired or does not exist.
167 keytab=FILE:/etc/krb5.keytab
170 tells pam_krb5.so the location of a keytab to use when validat‐
171 ing credentials obtained from KDCs.
172 minimum_uid=0
175 tells pam_krb5.so to ignore authentication attempts by users
176 with UIDs below the specified number.
177 multiple_ccaches
180 specifies that pam_krb5 should maintain multiple credential
181 caches for this service, because it both sets credentials and
182 opens a PAM session, but it sets the KRB5CCNAME variable after
183 doing only one of the two. This option is usually not necessary
184 for most services.
185 no_initial_prompt
188 tells pam_krb5.so to not ask for a password before attempting
189 authentication, and to instead allow the Kerberos library to
190 trigger a request for a password only in cases where one is
191 needed.
192 no_subsequent_prompt
195 tells pam_krb5.so to only provide the previously-entered pass‐
196 word in response to any request for a password which the Ker‐
197 beros library might make. If the calling application does not
198 properly support PAM conversations (possibly due to limitations
199 of a network protocol which it is serving), this may be need to
200 be used to prevent the application from supplying the user's
201 current password in a password-changing situations when a new
202 password is called for.
203 no_user_check
206 tells pam_krb5.so to not check if a user exists on the local
207 system, to skip authorization checks using the user's .k5login
208 file, and to create ccaches owned by the current process's UID.
209 This is useful for situations where a non-privileged server
210 process needs to use Kerberized services on behalf of remote
211 users who may not have local access. Note that such a server
212 should have an encrypted connection with its client in order to
213 avoid allowing the user's password to be eavesdropped.
214 no_validate
217 no_validate=vlock
219 tells pam_krb5.so to not attempt to use the local keytab to ver‐
220 ify that the TGT obtained from the realm's servers has not been
221 spoofed. The libdefaults verify_ap_req_nofail setting can
222 affect whether or not errors reading the keytab which are
223 encountered during validation will be suppressed.
224 null_afs
227 tells pam_krb5.so, when it attempts to set tokens, to try to get
228 credentials for services with names which resemble afs@REALM
229 before attempting to get credentials for services with names
230 resembling afs/cell@REALM. The default is to assume that the
231 cell's name is the instance in the AFS service's Kerberos prin‐
232 cipal name.
233 preauth_options=[]
236 controls the preauthentication options which pam_krb5 passes to
237 libkrb5, if the system-defaults need to be overridden. The list
238 is treated as a template, and these sequences are substituted:
239 %u login name
241 %U login UID
242 %p principal name
243 %r principal's realm name
244 %h home directory
245 %d the default ccache directory
246 %P the current process ID
247 %% literal '%'
248 A list of recognized values should be listed in the kinit(1)
250 manual page as parameters for its -X option.
251 pwhelp=filename
254 specifies the name of a text file whose contents will be dis‐
255 played to clients who attempt to change their passwords. There
256 is no default.
257 realm=realm
260 overrides the default realm set in /etc/krb5.conf, which
261 pam_krb5.so will attempt to authenticate users to.
262 tokens
265 tokens=imap
267 signals that pam_krb5.so should create a new AFS PAG and obtain
268 AFS tokens during authentication in addition to session setup.
269 This is primarily useful in server applications which need to
270 access a user's files but which do not open PAM sessions before
271 doing so. A properly-written server will not need this flag set
272 in order to function correctly.
273 trace turns on libkrb5's library tracing. Trace messages are logged
276 to syslog(3) with priority LOG_DEBUG.
277 try_first_pass
280 tells pam_krb5.so to check the previously-entered password as
281 with use_first_pass, but to prompt the user for another one if
282 the previously-entered one fails. This is the default mode of
283 operation.
284 use_first_pass
287 tells pam_krb5.so to get the user's entered password as it was
288 stored by a module listed earlier in the stack, usually pam_unix
289 or pam_pwdb, instead of prompting the user for it.
290 use_authtok
293 tells pam_krb5.so to never prompt for new passwords when chang‐
294 ing passwords. This is useful if you are using pam_cracklib or
295 pam_passwdqc to try to enforce use of less-easy-to-guess pass‐
296 words.
297 use_shmem
300 use_shmem=sshd
302 tells pam_krb5.so to pass credentials from the authentication
303 service function to the session management service function
304 using shared memory, or to do so for specific services.
305 validate_user_user
308 validate_user_user=gnome-screensaver
310 specifies that, when attempting validation of the TGT, the mod‐
311 ule should attempt user-to-user authentication using a previ‐
312 ously-obtainted TGT in the default ccache if validation can't be
313 performed using a keytab.
314
317 /etc/krb5.conf
318
321 pam_krb5(5) krb5.conf(5)
322
325 Probably, but let's hope not. If you find any, please file them in the
326 bug database at http://bugzilla.redhat.com/ against the "pam_krb5" com‐
327 ponent.
328
331 Nalin Dahyabhai <nalin@redhat.com>
332Red Hat Linux 2013/09/21 pam_krb5(8)