summaryrefslogtreecommitdiff
path: root/docs/htmldocs/pam.html
blob: 3b257d50ca01d7ea4cc8bcf9e51e7bfc6ec715de (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<HTML
><HEAD
><TITLE
>Configuring PAM for distributed but centrally 
managed authentication</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
REL="HOME"
TITLE="SAMBA Project Documentation"
HREF="samba-howto-collection.html"><LINK
REL="UP"
TITLE="Optional configuration"
HREF="optional.html"><LINK
REL="PREVIOUS"
TITLE="UNIX Permission Bits and Windows NT Access Control Lists"
HREF="unix-permissions.html"><LINK
REL="NEXT"
TITLE="Hosting a Microsoft Distributed File System tree on Samba"
HREF="msdfs.html"></HEAD
><BODY
CLASS="CHAPTER"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>SAMBA Project Documentation</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="unix-permissions.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="msdfs.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="CHAPTER"
><H1
><A
NAME="PAM"
></A
>Chapter 12. Configuring PAM for distributed but centrally 
managed authentication</H1
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="AEN1926"
>12.1. Samba and PAM</A
></H1
><P
>A number of Unix systems (eg: Sun Solaris), as well as the 
xxxxBSD family and Linux, now utilize the Pluggable Authentication 
Modules (PAM) facility to provide all authentication, 
authorization and resource control services. Prior to the 
introduction of PAM, a decision to use an alternative to 
the system password database (<TT
CLASS="FILENAME"
>/etc/passwd</TT
>) 
would require the provision of alternatives for all programs that provide 
security services. Such a choice would involve provision of 
alternatives to such programs as: <B
CLASS="COMMAND"
>login</B
>, 
<B
CLASS="COMMAND"
>passwd</B
>, <B
CLASS="COMMAND"
>chown</B
>, etc.</P
><P
>PAM provides a mechanism that disconnects these security programs 
from the underlying authentication/authorization infrastructure.
PAM is configured either through one file <TT
CLASS="FILENAME"
>/etc/pam.conf</TT
> (Solaris), 
or by editing individual files that are located in <TT
CLASS="FILENAME"
>/etc/pam.d</TT
>.</P
><P
>The following is an example <TT
CLASS="FILENAME"
>/etc/pam.d/login</TT
> configuration file. 
This example had all options been uncommented is probably not usable 
as it stacks many conditions before allowing successful completion 
of the login process. Essentially all conditions can be disabled 
by commenting them out except the calls to <TT
CLASS="FILENAME"
>pam_pwdb.so</TT
>.</P
><P
><PRE
CLASS="PROGRAMLISTING"
>#%PAM-1.0
# The PAM configuration file for the `login' service
#
auth 		required	pam_securetty.so
auth 		required	pam_nologin.so
# auth 		required	pam_dialup.so
# auth 		optional	pam_mail.so
auth		required	pam_pwdb.so shadow md5
# account    	requisite  	pam_time.so
account		required	pam_pwdb.so
session		required	pam_pwdb.so
# session 	optional	pam_lastlog.so
# password   	required   	pam_cracklib.so retry=3
password	required	pam_pwdb.so shadow md5</PRE
></P
><P
>PAM allows use of replacable modules. Those available on a 
sample system include:</P
><P
><PRE
CLASS="PROGRAMLISTING"
>$ /bin/ls /lib/security
pam_access.so    pam_ftp.so          pam_limits.so     
pam_ncp_auth.so  pam_rhosts_auth.so  pam_stress.so     
pam_cracklib.so  pam_group.so        pam_listfile.so   
pam_nologin.so   pam_rootok.so       pam_tally.so      
pam_deny.so      pam_issue.so        pam_mail.so       
pam_permit.so    pam_securetty.so    pam_time.so       
pam_dialup.so    pam_lastlog.so      pam_mkhomedir.so  
pam_pwdb.so      pam_shells.so       pam_unix.so       
pam_env.so       pam_ldap.so         pam_motd.so       
pam_radius.so    pam_smbpass.so      pam_unix_acct.so  
pam_wheel.so     pam_unix_auth.so    pam_unix_passwd.so
pam_userdb.so    pam_warn.so         pam_unix_session.so</PRE
></P
><P
>The following example for the login program replaces the use of 
the <TT
CLASS="FILENAME"
>pam_pwdb.so</TT
> module which uses the system 
password database (<TT
CLASS="FILENAME"
>/etc/passwd</TT
>,
<TT
CLASS="FILENAME"
>/etc/shadow</TT
>, <TT
CLASS="FILENAME"
>/etc/group</TT
>) with 
the module <TT
CLASS="FILENAME"
>pam_smbpass.so</TT
> which uses the Samba 
database which contains the Microsoft MD4 encrypted password 
hashes. This database is stored in either 
<TT
CLASS="FILENAME"
>/usr/local/samba/private/smbpasswd</TT
>, 
<TT
CLASS="FILENAME"
>/etc/samba/smbpasswd</TT
>, or in 
<TT
CLASS="FILENAME"
>/etc/samba.d/smbpasswd</TT
>, depending on the 
Samba implementation for your Unix/Linux system. The 
<TT
CLASS="FILENAME"
>pam_smbpass.so</TT
> module is provided by 
Samba version 2.2.1 or later. It can be compiled by specifying the 
<B
CLASS="COMMAND"
>--with-pam_smbpass</B
> options when running Samba's
<TT
CLASS="FILENAME"
>configure</TT
> script.  For more information
on the <TT
CLASS="FILENAME"
>pam_smbpass</TT
> module, see the documentation
in the <TT
CLASS="FILENAME"
>source/pam_smbpass</TT
> directory of the Samba 
source distribution.</P
><P
><PRE
CLASS="PROGRAMLISTING"
>#%PAM-1.0
# The PAM configuration file for the `login' service
#
auth		required	pam_smbpass.so nodelay
account		required	pam_smbpass.so nodelay
session		required	pam_smbpass.so nodelay
password	required	pam_smbpass.so nodelay</PRE
></P
><P
>The following is the PAM configuration file for a particular 
Linux system. The default condition uses <TT
CLASS="FILENAME"
>pam_pwdb.so</TT
>.</P
><P
><PRE
CLASS="PROGRAMLISTING"
>#%PAM-1.0
# The PAM configuration file for the `samba' service
#
auth       required     /lib/security/pam_pwdb.so nullok nodelay shadow audit
account    required     /lib/security/pam_pwdb.so audit nodelay
session    required     /lib/security/pam_pwdb.so nodelay
password   required     /lib/security/pam_pwdb.so shadow md5</PRE
></P
><P
>In the following example the decision has been made to use the 
smbpasswd database even for basic samba authentication. Such a 
decision could also be made for the passwd program and would 
thus allow the smbpasswd passwords to be changed using the passwd 
program.</P
><P
><PRE
CLASS="PROGRAMLISTING"
>#%PAM-1.0
# The PAM configuration file for the `samba' service
#
auth       required     /lib/security/pam_smbpass.so nodelay
account    required     /lib/security/pam_pwdb.so audit nodelay
session    required     /lib/security/pam_pwdb.so nodelay
password   required     /lib/security/pam_smbpass.so nodelay smbconf=/etc/samba.d/smb.conf</PRE
></P
><P
>Note: PAM allows stacking of authentication mechanisms. It is 
also possible to pass information obtained within one PAM module through 
to the next module in the PAM stack. Please refer to the documentation for 
your particular system implementation for details regarding the specific 
capabilities of PAM in this environment. Some Linux implmentations also 
provide the <TT
CLASS="FILENAME"
>pam_stack.so</TT
> module that allows all 
authentication to be configured in a single central file. The 
<TT
CLASS="FILENAME"
>pam_stack.so</TT
> method has some very devoted followers 
on the basis that it allows for easier administration. As with all issues in 
life though, every decision makes trade-offs, so you may want examine the 
PAM documentation for further helpful information.</P
></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="AEN1970"
>12.2. Distributed Authentication</A
></H1
><P
>The astute administrator will realize from this that the 
combination of <TT
CLASS="FILENAME"
>pam_smbpass.so</TT
>, 
<B
CLASS="COMMAND"
>winbindd</B
>, and <B
CLASS="COMMAND"
>rsync</B
> (see
<A
HREF="http://rsync.samba.org/"
TARGET="_top"
>http://rsync.samba.org/</A
>)
will allow the establishment of a centrally managed, distributed 
user/password database that can also be used by all 
PAM (eg: Linux) aware programs and applications. This arrangement 
can have particularly potent advantages compared with the 
use of Microsoft Active Directory Service (ADS) in so far as 
reduction of wide area network authentication traffic.</P
></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="AEN1977"
>12.3. PAM Configuration in smb.conf</A
></H1
><P
>There is an option in smb.conf called <A
HREF="smb.conf.5.html#OBEYPAMRESTRICTIONS"
TARGET="_top"
>obey pam restrictions</A
>. 
The following is from the on-line help for this option in SWAT;</P
><P
>When Samba 2.2 is configure to enable PAM support (i.e. 
<CODE
CLASS="CONSTANT"
>--with-pam</CODE
>), this parameter will 
control whether or not Samba should obey PAM's account 
and session management directives. The default behavior 
is to use PAM for clear text authentication only and to 
ignore any account or session management. Note that Samba always 
ignores PAM for authentication in the case of 
<A
HREF="smb.conf.5.html#ENCRYPTPASSWORDS"
TARGET="_top"
>encrypt passwords = yes</A
>. 
The reason is that PAM modules cannot support the challenge/response 
authentication mechanism needed in the presence of SMB 
password encryption. </P
><P
>Default: <B
CLASS="COMMAND"
>obey pam restrictions = no</B
></P
></DIV
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="unix-permissions.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="samba-howto-collection.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="msdfs.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>UNIX Permission Bits and Windows NT Access Control Lists</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="optional.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Hosting a Microsoft Distributed File System tree on Samba</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>