1 <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 27. PAM-Based Distributed Authentication</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.68.1"><link rel="start" href="index.html" title="The Official Samba-3 HOWTO and Reference Guide"><link rel="up" href="optional.html" title="Part III. Advanced Configuration"><link rel="prev" href="ProfileMgmt.html" title="Chapter 26. Desktop Profile Management"><link rel="next" href="integrate-ms-networks.html" title="Chapter 28. Integrating MS Windows Networks with Samba"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 27. PAM-Based Distributed Authentication</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ProfileMgmt.html">Prev</a> </td><th width="60%" align="center">Part III. Advanced Configuration</th><td width="20%" align="right"> <a accesskey="n" href="integrate-ms-networks.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="pam"></a>Chapter 27. PAM-Based Distributed Authentication</h2></div><div><div class="author"><h3 class="author"><span class="firstname">John</span> <span class="othername">H.</span> <span class="surname">Terpstra</span></h3><div class="affiliation"><span class="orgname">Samba Team<br></span><div class="address"><p><code class="email"><<a href="mailto:jht@samba.org">jht@samba.org</a>></code></p></div></div></div></div><div><div class="author"><h3 class="author"><span class="firstname">Stephen</span> <span class="surname">Langasek</span></h3><div class="affiliation"><div class="address"><p><code class="email"><<a href="mailto:vorlon@netexpress.net">vorlon@netexpress.net</a>></code></p></div></div></div></div><div><p class="pubdate">May 31, 2003</p></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="pam.html#id2631822">Features and Benefits</a></span></dt><dt><span class="sect1"><a href="pam.html#id2632453">Technical Discussion</a></span></dt><dd><dl><dt><span class="sect2"><a href="pam.html#id2632506">PAM Configuration Syntax</a></span></dt><dt><span class="sect2"><a href="pam.html#id2633504">Example System Configurations</a></span></dt><dt><span class="sect2"><a href="pam.html#id2633811"><code class="filename">smb.conf</code> PAM Configuration</a></span></dt><dt><span class="sect2"><a href="pam.html#id2633878">Remote CIFS Authentication Using <code class="filename">winbindd.so</code></a></span></dt><dt><span class="sect2"><a href="pam.html#id2633978">Password Synchronization Using <code class="filename">pam_smbpass.so</code></a></span></dt></dl></dd><dt><span class="sect1"><a href="pam.html#id2634372">Common Errors</a></span></dt><dd><dl><dt><span class="sect2"><a href="pam.html#id2634383">pam_winbind Problem</a></span></dt><dt><span class="sect2"><a href="pam.html#id2634481">Winbind Is Not Resolving Users and Groups</a></span></dt></dl></dd></dl></div><p>
2 <a class="indexterm" name="id2631747"></a>
3 <a class="indexterm" name="id2631753"></a>
4 <a class="indexterm" name="id2631760"></a>
5 <a class="indexterm" name="id2631767"></a>
6 This chapter should help you to deploy Winbind-based authentication on any PAM-enabled
7 UNIX/Linux system. Winbind can be used to enable user-level application access authentication
8 from any MS Windows NT domain, MS Windows 200x Active Directory-based
9 domain, or any Samba-based domain environment. It will also help you to configure PAM-based local host access
10 controls that are appropriate to your Samba configuration.
12 <a class="indexterm" name="id2631784"></a>
13 <a class="indexterm" name="id2631791"></a>
14 In addition to knowing how to configure Winbind into PAM, you will learn generic PAM management
15 possibilities and in particular how to deploy tools like <code class="filename">pam_smbpass.so</code> to your advantage.
16 </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
17 The use of Winbind requires more than PAM configuration alone.
18 Please refer to <a href="winbind.html" title="Chapter 23. Winbind: Use of Domain Accounts">Winbind: Use of Domain Accounts</a>, for further information regarding Winbind.
19 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2631822"></a>Features and Benefits</h2></div></div></div><p>
20 <a class="indexterm" name="id2631830"></a>
21 <a class="indexterm" name="id2631837"></a>
22 <a class="indexterm" name="id2631844"></a>
23 <a class="indexterm" name="id2631850"></a>
24 <a class="indexterm" name="id2631860"></a>
25 <a class="indexterm" name="id2631867"></a>
26 <a class="indexterm" name="id2631873"></a>
27 <a class="indexterm" name="id2631880"></a>
28 A number of UNIX systems (e.g., Sun Solaris), as well as the xxxxBSD family and Linux,
29 now utilize the Pluggable Authentication Modules (PAM) facility to provide all authentication,
30 authorization, and resource control services. Prior to the introduction of PAM, a decision
31 to use an alternative to the system password database (<code class="filename">/etc/passwd</code>)
32 would require the provision of alternatives for all programs that provide security services.
33 Such a choice would involve provision of alternatives to programs such as <span><strong class="command">login</strong></span>,
34 <span><strong class="command">passwd</strong></span>, <span><strong class="command">chown</strong></span>, and so on.
36 <a class="indexterm" name="id2631922"></a>
37 <a class="indexterm" name="id2631929"></a>
38 <a class="indexterm" name="id2631936"></a>
39 <a class="indexterm" name="id2631942"></a>
40 PAM provides a mechanism that disconnects these security programs from the underlying
41 authentication/authorization infrastructure. PAM is configured by making appropriate modifications to one file,
42 <code class="filename">/etc/pam.conf</code> (Solaris), or by editing individual control files that are
43 located in <code class="filename">/etc/pam.d</code>.
45 <a class="indexterm" name="id2631969"></a>
46 <a class="indexterm" name="id2631976"></a>
47 On PAM-enabled UNIX/Linux systems, it is an easy matter to configure the system to use any
48 authentication backend so long as the appropriate dynamically loadable library modules
49 are available for it. The backend may be local to the system or may be centralized on a
52 PAM support modules are available for:
53 </p><div class="variablelist"><dl><dt><span class="term"><code class="filename">/etc/passwd</code></span></dt><dd><p>
54 <a class="indexterm" name="id2632006"></a>
55 <a class="indexterm" name="id2632013"></a>
56 <a class="indexterm" name="id2632020"></a>
57 <a class="indexterm" name="id2632026"></a>
58 <a class="indexterm" name="id2632033"></a>
59 <a class="indexterm" name="id2632040"></a>
60 There are several PAM modules that interact with this standard UNIX user database. The most common are called
61 <code class="filename">pam_unix.so</code>, <code class="filename">pam_unix2.so</code>, <code class="filename">pam_pwdb.so</code> and
62 <code class="filename">pam_userdb.so</code>.
63 </p></dd><dt><span class="term">Kerberos</span></dt><dd><p>
64 <a class="indexterm" name="id2632083"></a>
65 <a class="indexterm" name="id2632089"></a>
66 <a class="indexterm" name="id2632096"></a>
67 <a class="indexterm" name="id2632103"></a>
68 <a class="indexterm" name="id2632110"></a>
69 The <code class="filename">pam_krb5.so</code> module allows the use of any Kerberos-compliant server.
70 This tool is used to access MIT Kerberos, Heimdal Kerberos, and potentially
71 Microsoft Active Directory (if enabled).
72 </p></dd><dt><span class="term">LDAP</span></dt><dd><p>
73 <a class="indexterm" name="id2632136"></a>
74 <a class="indexterm" name="id2632142"></a>
75 <a class="indexterm" name="id2632149"></a>
76 <a class="indexterm" name="id2632156"></a>
77 <a class="indexterm" name="id2632163"></a>
78 <a class="indexterm" name="id2632170"></a>
79 The <code class="filename">pam_ldap.so</code> module allows the use of any LDAP v2- or v3-compatible backend
80 server. Commonly used LDAP backend servers include OpenLDAP v2.0 and v2.1,
81 Sun ONE iDentity server, Novell eDirectory server, and Microsoft Active Directory.
82 </p></dd><dt><span class="term">NetWare Bindery</span></dt><dd><p>
83 <a class="indexterm" name="id2632197"></a>
84 <a class="indexterm" name="id2632204"></a>
85 <a class="indexterm" name="id2632211"></a>
86 <a class="indexterm" name="id2632218"></a>
87 The <code class="filename">pam_ncp_auth.so</code> module allows authentication off any bindery-enabled
88 NetWare Core Protocol-based server.
89 </p></dd><dt><span class="term">SMB Password</span></dt><dd><p>
90 <a class="indexterm" name="id2632243"></a>
91 <a class="indexterm" name="id2632250"></a>
92 <a class="indexterm" name="id2632257"></a>
93 This module, called <code class="filename">pam_smbpass.so</code>, allows user authentication of
94 the passdb backend that is configured in the Samba <code class="filename">smb.conf</code> file.
95 </p></dd><dt><span class="term">SMB Server</span></dt><dd><p>
96 <a class="indexterm" name="id2632288"></a>
97 <a class="indexterm" name="id2632294"></a>
98 The <code class="filename">pam_smb_auth.so</code> module is the original MS Windows networking authentication
99 tool. This module has been somewhat outdated by the Winbind module.
100 </p></dd><dt><span class="term">Winbind</span></dt><dd><p>
101 <a class="indexterm" name="id2632320"></a>
102 <a class="indexterm" name="id2632327"></a>
103 <a class="indexterm" name="id2632334"></a>
104 <a class="indexterm" name="id2632340"></a>
105 The <code class="filename">pam_winbind.so</code> module allows Samba to obtain authentication from any
106 MS Windows domain controller. It can just as easily be used to authenticate
107 users for access to any PAM-enabled application.
108 </p></dd><dt><span class="term">RADIUS</span></dt><dd><p>
109 <a class="indexterm" name="id2632367"></a>
110 There is a PAM RADIUS (Remote Access Dial-In User Service) authentication
111 module. In most cases, administrators need to locate the source code
112 for this tool and compile and install it themselves. RADIUS protocols are
113 used by many routers and terminal servers.
114 </p></dd></dl></div><p>
115 <a class="indexterm" name="id2632386"></a>
116 <a class="indexterm" name="id2632393"></a>
117 Of the modules listed, Samba provides the <code class="filename">pam_smbpasswd.so</code> and the
118 <code class="filename">pam_winbind.so</code> modules alone.
120 <a class="indexterm" name="id2632416"></a>
121 <a class="indexterm" name="id2632424"></a>
122 <a class="indexterm" name="id2632431"></a>
123 <a class="indexterm" name="id2632437"></a>
124 Once configured, these permit a remarkable level of flexibility in the location and use
125 of distributed Samba domain controllers that can provide wide-area network bandwidth,
126 efficient authentication services for PAM-capable systems. In effect, this allows the
127 deployment of centrally managed and maintained distributed authentication from a
128 single-user account database.
129 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2632453"></a>Technical Discussion</h2></div></div></div><p>
130 <a class="indexterm" name="id2632461"></a>
131 <a class="indexterm" name="id2632467"></a>
132 <a class="indexterm" name="id2632475"></a>
133 <a class="indexterm" name="id2632482"></a>
134 PAM is designed to provide system administrators with a great deal of flexibility in
135 configuration of the privilege-granting applications of their system. The local
136 configuration of system security controlled by PAM is contained in one of two places:
137 either the single system file <code class="filename">/etc/pam.conf</code> or the
138 <code class="filename">/etc/pam.d/</code> directory.
139 </p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2632506"></a>PAM Configuration Syntax</h3></div></div></div><p>
140 <a class="indexterm" name="id2632514"></a>
141 <a class="indexterm" name="id2632521"></a>
142 In this section we discuss the correct syntax of and generic options respected by entries to these files.
143 PAM-specific tokens in the configuration file are case insensitive. The module paths, however, are case
144 sensitive, since they indicate a file's name and reflect the case dependence of typical file systems. The
145 case sensitivity of the arguments to any given module is defined for each module in turn.
147 In addition to the lines described below, there are two special characters provided for the convenience
148 of the system administrator: comments are preceded by a “<span class="quote">#</span>” and extend to the next end-of-line; also,
149 module specification lines may be extended with a “<span class="quote">\</span>”-escaped newline.
151 <a class="indexterm" name="id2632553"></a>
152 <a class="indexterm" name="id2632560"></a>
153 If the PAM authentication module (loadable link library file) is located in the
154 default location, then it is not necessary to specify the path. In the case of
155 Linux, the default location is <code class="filename">/lib/security</code>. If the module
156 is located outside the default, then the path must be specified as:
157 </p><pre class="programlisting">
158 auth required /other_path/pam_strange_module.so
160 </p><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2632585"></a>Anatomy of <code class="filename">/etc/pam.d</code> Entries</h4></div></div></div><p>
161 The remaining information in this subsection was taken from the documentation of the Linux-PAM
162 project. For more information on PAM, see
163 <a href="http://ftp.kernel.org/pub/linux/libs/pam/" target="_top">the Official Linux-PAM home page</a>.
165 <a class="indexterm" name="id2632611"></a>
166 A general configuration line of the <code class="filename">/etc/pam.conf</code> file has the following form:
167 </p><pre class="programlisting">
168 service-name module-type control-flag module-path args
171 We explain the meaning of each of these tokens. The second (and more recently adopted)
172 way of configuring Linux-PAM is via the contents of the <code class="filename">/etc/pam.d/</code> directory.
173 Once we have explained the meaning of the tokens, we describe this method.
174 </p><div class="variablelist"><dl><dt><span class="term">service-name</span></dt><dd><p>
175 <a class="indexterm" name="id2632657"></a>
176 <a class="indexterm" name="id2632663"></a>
177 <a class="indexterm" name="id2632670"></a>
178 The name of the service associated with this entry. Frequently, the service-name is the conventional
179 name of the given application for example, <span><strong class="command">ftpd</strong></span>, <span><strong class="command">rlogind</strong></span> and
180 <span><strong class="command">su</strong></span>, and so on.
182 There is a special service-name reserved for defining a default authentication mechanism. It has
183 the name <em class="parameter"><code>OTHER</code></em> and may be specified in either lower- or uppercase characters.
184 Note, when there is a module specified for a named service, the <em class="parameter"><code>OTHER</code></em>
186 </p></dd><dt><span class="term">module-type</span></dt><dd><p>
187 One of (currently) four types of module. The four types are as follows:
188 </p><div class="itemizedlist"><ul type="disc"><li><p>
189 <a class="indexterm" name="id2632738"></a>
190 <a class="indexterm" name="id2632745"></a>
191 <em class="parameter"><code>auth:</code></em> This module type provides two aspects of authenticating the user.
192 It establishes that the user is who he or she claims to be by instructing the application
193 to prompt the user for a password or other means of identification. Second, the module can
194 grant group membership (independently of the <code class="filename">/etc/groups</code> file)
195 or other privileges through its credential-granting properties.
197 <a class="indexterm" name="id2632774"></a>
198 <a class="indexterm" name="id2632781"></a>
199 <em class="parameter"><code>account:</code></em> This module performs non-authentication-based account management.
200 It is typically used to restrict/permit access to a service based on the time of day, currently
201 available system resources (maximum number of users), or perhaps the location of the user
202 login. For example, the “<span class="quote">root</span>” login may be permitted only on the console.
204 <a class="indexterm" name="id2632808"></a>
205 <em class="parameter"><code>session:</code></em> Primarily, this module is associated with doing things that need
206 to be done for the user before and after he or she can be given service. Such things include logging
207 information concerning the opening and closing of some data exchange with a user, mounting
208 directories, and so on.
210 <a class="indexterm" name="id2632830"></a>
211 <em class="parameter"><code>password:</code></em> This last module type is required for updating the authentication
212 token associated with the user. Typically, there is one module for each
213 “<span class="quote">challenge/response</span>” authentication <em class="parameter"><code>(auth)</code></em> module type.
214 </p></li></ul></div></dd><dt><span class="term">control-flag</span></dt><dd><p>
215 The control-flag is used to indicate how the PAM library will react to the success or failure of the
216 module it is associated with. Since modules can be stacked (modules of the same type execute in series,
217 one after another), the control-flags determine the relative importance of each module. The application
218 is not made aware of the individual success or failure of modules listed in the
219 <code class="filename">/etc/pam.conf</code> file. Instead, it receives a summary success or fail response from
220 the Linux-PAM library. The order of execution of these modules is that of the entries in the
221 <code class="filename">/etc/pam.conf</code> file; earlier entries are executed before later ones.
222 As of Linux-PAM v0.60, this control-flag can be defined with one of two syntaxes.
224 <a class="indexterm" name="id2632894"></a>
225 <a class="indexterm" name="id2632901"></a>
226 <a class="indexterm" name="id2632908"></a>
227 <a class="indexterm" name="id2632914"></a>
228 The simpler (and historical) syntax for the control-flag is a single keyword defined to indicate the
229 severity of concern associated with the success or failure of a specific module. There are four such
230 keywords: <em class="parameter"><code>required</code></em>, <em class="parameter"><code>requisite</code></em>,
231 <em class="parameter"><code>sufficient</code></em>, and <em class="parameter"><code>optional</code></em>.
233 The Linux-PAM library interprets these keywords in the following manner:
234 </p><div class="itemizedlist"><ul type="disc"><li><p>
235 <em class="parameter"><code>required:</code></em> This indicates that the success of the module is required for the
236 module-type facility to succeed. Failure of this module will not be apparent to the user until all
237 of the remaining modules (of the same module-type) have been executed.
239 <em class="parameter"><code>requisite:</code></em> Like required, except that if such a module returns a
240 failure, control is directly returned to the application. The return value is that associated with
241 the first required or requisite module to fail. This flag can be used to protect against the
242 possibility of a user getting the opportunity to enter a password over an unsafe medium. It is
243 conceivable that such behavior might inform an attacker of valid accounts on a system. This
244 possibility should be weighed against the not insignificant concerns of exposing a sensitive
245 password in a hostile environment.
247 <em class="parameter"><code>sufficient:</code></em> The success of this module is deemed <em class="parameter"><code>sufficient</code></em> to satisfy
248 the Linux-PAM library that this module-type has succeeded in its purpose. In the event that no
249 previous required module has failed, no more “<span class="quote">stacked</span>” modules of this type are invoked.
250 (In this case, subsequent required modules are not invoked). A failure of this module is not deemed
251 as fatal to satisfying the application that this module-type has succeeded.
253 <em class="parameter"><code>optional:</code></em> As its name suggests, this control-flag marks the module as not
254 being critical to the success or failure of the user's application for service. In general,
255 Linux-PAM ignores such a module when determining if the module stack will succeed or fail.
256 However, in the absence of any definite successes or failures of previous or subsequent stacked
257 modules, this module will determine the nature of the response to the application. One example of
258 this latter case is when the other modules return something like PAM_IGNORE.
259 </p></li></ul></div><p>
260 The more elaborate (newer) syntax is much more specific and gives the administrator a great deal of control
261 over how the user is authenticated. This form of the control-flag is delimited with square brackets and
262 consists of a series of <em class="parameter"><code>value=action</code></em> tokens:
263 </p><pre class="programlisting">
264 [value1=action1 value2=action2 ...]
266 Here, <em class="parameter"><code>value1</code></em> is one of the following return values:
267 </p><pre class="screen">
268 <em class="parameter"><code>success; open_err; symbol_err; service_err; system_err; buf_err;</code></em>
269 <em class="parameter"><code>perm_denied; auth_err; cred_insufficient; authinfo_unavail;</code></em>
270 <em class="parameter"><code>user_unknown; maxtries; new_authtok_reqd; acct_expired; session_err;</code></em>
271 <em class="parameter"><code>cred_unavail; cred_expired; cred_err; no_module_data; conv_err;</code></em>
272 <em class="parameter"><code>authtok_err; authtok_recover_err; authtok_lock_busy;</code></em>
273 <em class="parameter"><code>authtok_disable_aging; try_again; ignore; abort; authtok_expired;</code></em>
274 <em class="parameter"><code>module_unknown; bad_item;</code></em> and <em class="parameter"><code>default</code></em>.
277 The last of these (<em class="parameter"><code>default</code></em>) can be used to set the action for those return values that are not explicitly defined.
279 The <em class="parameter"><code>action1</code></em> can be a positive integer or one of the following tokens:
280 <em class="parameter"><code>ignore</code></em>; <em class="parameter"><code>ok</code></em>; <em class="parameter"><code>done</code></em>;
281 <em class="parameter"><code>bad</code></em>; <em class="parameter"><code>die</code></em>; and <em class="parameter"><code>reset</code></em>.
282 A positive integer, J, when specified as the action, can be used to indicate that the next J modules of the
283 current module-type will be skipped. In this way, the administrator can develop a moderately sophisticated
284 stack of modules with a number of different paths of execution. Which path is taken can be determined by the
285 reactions of individual modules.
286 </p><div class="itemizedlist"><ul type="disc"><li><p>
287 <em class="parameter"><code>ignore:</code></em> When used with a stack of modules, the module's return status will not
288 contribute to the return code the application obtains.
290 <em class="parameter"><code>bad:</code></em> This action indicates that the return code should be thought of as indicative
291 of the module failing. If this module is the first in the stack to fail, its status value will be used
292 for that of the whole stack.
294 <em class="parameter"><code>die:</code></em> Equivalent to bad with the side effect of terminating the module stack and
295 PAM immediately returning to the application.
297 <em class="parameter"><code>ok:</code></em> This tells PAM that the administrator thinks this return code should
298 contribute directly to the return code of the full stack of modules. In other words, if the former
299 state of the stack would lead to a return of PAM_SUCCESS, the module's return code will override
300 this value. Note, if the former state of the stack holds some value that is indicative of a module's
301 failure, this <em class="parameter"><code>ok</code></em> value will not be used to override that value.
303 <em class="parameter"><code>done:</code></em> Equivalent to <em class="parameter"><code>ok</code></em> with the side effect of terminating the module stack and
304 PAM immediately returning to the application.
306 <em class="parameter"><code>reset:</code></em> Clears all memory of the state of the module stack and starts again with
307 the next stacked module.
308 </p></li></ul></div><p>
309 Each of the four keywords, <em class="parameter"><code>required</code></em>; <em class="parameter"><code>requisite</code></em>;
310 <em class="parameter"><code>sufficient</code></em>; and <em class="parameter"><code>optional</code></em>, have an equivalent expression in terms
311 of the [...] syntax. They are as follows:
313 </p><div class="itemizedlist"><ul type="disc"><li><p>
314 <em class="parameter"><code>required</code></em> is equivalent to <em class="parameter"><code>[success=ok new_authtok_reqd=ok ignore=ignore default=bad]</code></em>.
316 <em class="parameter"><code>requisite</code></em> is equivalent to <em class="parameter"><code>[success=ok new_authtok_reqd=ok ignore=ignore default=die]</code></em>.
318 <em class="parameter"><code>sufficient</code></em> is equivalent to <em class="parameter"><code>[success=done new_authtok_reqd=done default=ignore]</code></em>.
320 <em class="parameter"><code>optional</code></em> is equivalent to <em class="parameter"><code>[success=ok new_authtok_reqd=ok default=ignore]</code></em>.
321 </p></li></ul></div><p>
323 Just to get a feel for the power of this new syntax, here is a taste of what you can do with it. With Linux-PAM-0.63,
324 the notion of client plug-in agents was introduced. This makes it possible for PAM to support
325 machine-machine authentication using the transport protocol inherent to the client/server application. With the
326 <em class="parameter"><code>[ ... value=action ... ]</code></em> control syntax, it is possible for an application to be configured
327 to support binary prompts with compliant clients, but to gracefully fail over into an alternative authentication
328 mode for legacy applications.
329 </p></dd><dt><span class="term">module-path</span></dt><dd><p>
330 The pathname of the dynamically loadable object file; the pluggable module itself. If the first character of the
331 module path is “<span class="quote">/</span>”, it is assumed to be a complete path. If this is not the case, the given module path is appended
332 to the default module path: <code class="filename">/lib/security</code> (but see the previous notes).
334 The arguments are a list of tokens that are passed to the module when it is invoked, much like arguments to a typical
335 Linux shell command. Generally, valid arguments are optional and are specific to any given module. Invalid arguments
336 are ignored by a module; however, when encountering an invalid argument, the module is required to write an error
337 to syslog(3). For a list of generic options, see the next section.
339 If you wish to include spaces in an argument, you should surround that argument with square brackets. For example:
340 </p><pre class="programlisting">
341 squid auth required pam_mysql.so user=passwd_query passwd=mada \
342 db=eminence [query=select user_name from internet_service where \
343 user_name=“<span class="quote">%u</span>” and password=PASSWORD(“<span class="quote">%p</span>”) and service=“<span class="quote">web_proxy</span>”]
345 When using this convention, you can include “<span class="quote">[</span>” characters inside the string, and if you wish to have a “<span class="quote">]</span>”
346 character inside the string that will survive the argument parsing, you should use “<span class="quote">\[</span>”. In other words,
347 </p><pre class="programlisting">
348 [..[..\]..] --> ..[..]..
350 Any line in one of the configuration files that is not formatted correctly will generally tend (erring on the
351 side of caution) to make the authentication process fail. A corresponding error is written to the system log files
352 with a call to syslog(3).
353 </p></dd></dl></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2633504"></a>Example System Configurations</h3></div></div></div><p>
354 The following is an example <code class="filename">/etc/pam.d/login</code> configuration file.
355 This example had all options uncommented and is probably not usable
356 because it stacks many conditions before allowing successful completion
357 of the login process. Essentially, all conditions can be disabled
358 by commenting them out, except the calls to <code class="filename">pam_pwdb.so</code>.
359 </p><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2633530"></a>PAM: Original Login Config</h4></div></div></div><p>
360 </p><pre class="programlisting">
362 # The PAM configuration file for the “<span class="quote">login</span>” service
364 auth required pam_securetty.so
365 auth required pam_nologin.so
366 # auth required pam_dialup.so
367 # auth optional pam_mail.so
368 auth required pam_pwdb.so shadow md5
369 # account requisite pam_time.so
370 account required pam_pwdb.so
371 session required pam_pwdb.so
372 # session optional pam_lastlog.so
373 # password required pam_cracklib.so retry=3
374 password required pam_pwdb.so shadow md5
376 </p></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2633558"></a>PAM: Login Using <code class="filename">pam_smbpass</code></h4></div></div></div><p>
377 PAM allows use of replaceable modules. Those available on a sample system include:
378 </p><p><code class="prompt">$</code><strong class="userinput"><code>/bin/ls /lib/security</code></strong>
379 </p><pre class="programlisting">
380 pam_access.so pam_ftp.so pam_limits.so
381 pam_ncp_auth.so pam_rhosts_auth.so pam_stress.so
382 pam_cracklib.so pam_group.so pam_listfile.so
383 pam_nologin.so pam_rootok.so pam_tally.so
384 pam_deny.so pam_issue.so pam_mail.so
385 pam_permit.so pam_securetty.so pam_time.so
386 pam_dialup.so pam_lastlog.so pam_mkhomedir.so
387 pam_pwdb.so pam_shells.so pam_unix.so
388 pam_env.so pam_ldap.so pam_motd.so
389 pam_radius.so pam_smbpass.so pam_unix_acct.so
390 pam_wheel.so pam_unix_auth.so pam_unix_passwd.so
391 pam_userdb.so pam_warn.so pam_unix_session.so
393 The following example for the login program replaces the use of
394 the <code class="filename">pam_pwdb.so</code> module that uses the system
395 password database (<code class="filename">/etc/passwd</code>,
396 <code class="filename">/etc/shadow</code>, <code class="filename">/etc/group</code>) with
397 the module <code class="filename">pam_smbpass.so</code>, which uses the Samba
398 database containing the Microsoft MD4 encrypted password
399 hashes. This database is stored either in
400 <code class="filename">/usr/local/samba/private/smbpasswd</code>,
401 <code class="filename">/etc/samba/smbpasswd</code> or in
402 <code class="filename">/etc/samba.d/smbpasswd</code>, depending on the
403 Samba implementation for your UNIX/Linux system. The
404 <code class="filename">pam_smbpass.so</code> module is provided by
405 Samba version 2.2.1 or later. It can be compiled by specifying the
406 <code class="option">--with-pam_smbpass</code> options when running Samba's
407 <span><strong class="command">configure</strong></span> script. For more information
408 on the <code class="filename">pam_smbpass</code> module, see the documentation
409 in the <code class="filename">source/pam_smbpass</code> directory of the Samba
412 </p><pre class="programlisting">
414 # The PAM configuration file for the “<span class="quote">login</span>” service
416 auth required pam_smbpass.so nodelay
417 account required pam_smbpass.so nodelay
418 session required pam_smbpass.so nodelay
419 password required pam_smbpass.so nodelay
421 The following is the PAM configuration file for a particular
422 Linux system. The default condition uses <code class="filename">pam_pwdb.so</code>.
424 </p><pre class="programlisting">
426 # The PAM configuration file for the “<span class="quote">samba</span>” service
428 auth required pam_pwdb.so nullok nodelay shadow audit
429 account required pam_pwdb.so audit nodelay
430 session required pam_pwdb.so nodelay
431 password required pam_pwdb.so shadow md5
433 In the following example, the decision has been made to use the
434 <span><strong class="command">smbpasswd</strong></span> database even for basic Samba authentication. Such a
435 decision could also be made for the <span><strong class="command">passwd</strong></span> program and would
436 thus allow the <span><strong class="command">smbpasswd</strong></span> passwords to be changed using the
437 <span><strong class="command">passwd</strong></span> program:
439 </p><pre class="programlisting">
441 # The PAM configuration file for the “<span class="quote">samba</span>” service
443 auth required pam_smbpass.so nodelay
444 account required pam_pwdb.so audit nodelay
445 session required pam_pwdb.so nodelay
446 password required pam_smbpass.so nodelay smbconf=/etc/samba.d/smb.conf
448 </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>PAM allows stacking of authentication mechanisms. It is
449 also possible to pass information obtained within one PAM module through
450 to the next module in the PAM stack. Please refer to the documentation for
451 your particular system implementation for details regarding the specific
452 capabilities of PAM in this environment. Some Linux implementations also
453 provide the <code class="filename">pam_stack.so</code> module that allows all
454 authentication to be configured in a single central file. The
455 <code class="filename">pam_stack.so</code> method has some devoted followers
456 on the basis that it allows for easier administration. As with all issues in
457 life, though, every decision has trade-offs, so you may want to examine the
458 PAM documentation for further helpful information.
459 </p></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2633811"></a><code class="filename">smb.conf</code> PAM Configuration</h3></div></div></div><p>
460 There is an option in <code class="filename">smb.conf</code> called <a class="indexterm" name="id2633830"></a>obey pam restrictions.
461 The following is from the online help for this option in SWAT:
462 </p><div class="blockquote"><blockquote class="blockquote"><p>
463 When Samba is configured to enable PAM support (i.e., <code class="option">--with-pam</code>), this parameter will
464 control whether or not Samba should obey PAM's account and session management directives. The default behavior
465 is to use PAM for clear-text authentication only and to ignore any account or session management. Samba always
466 ignores PAM for authentication in the case of <a class="indexterm" name="id2633853"></a>encrypt passwords = yes.
467 The reason is that PAM modules cannot support the challenge/response authentication mechanism needed in the presence of SMB
469 </p><p>Default: <a class="indexterm" name="id2633867"></a>obey pam restrictions = no</p></blockquote></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2633878"></a>Remote CIFS Authentication Using <code class="filename">winbindd.so</code></h3></div></div></div><p>
470 All operating systems depend on the provision of user credentials acceptable to the platform.
471 UNIX requires the provision of a user identifier (UID) as well as a group identifier (GID).
472 These are both simple integer numbers that are obtained from a password backend such
473 as <code class="filename">/etc/passwd</code>.
475 Users and groups on a Windows NT server are assigned a relative ID (RID) which is unique for
476 the domain when the user or group is created. To convert the Windows NT user or group into
477 a UNIX user or group, a mapping between RIDs and UNIX user and group IDs is required. This
478 is one of the jobs that winbind performs.
480 As winbind users and groups are resolved from a server, user and group IDs are allocated
481 from a specified range. This is done on a first come, first served basis, although all
482 existing users and groups will be mapped as soon as a client performs a user or group
483 enumeration command. The allocated UNIX IDs are stored in a database file under the Samba
484 lock directory and will be remembered.
486 The astute administrator will realize from this that the combination of <code class="filename">pam_smbpass.so</code>,
487 <span><strong class="command">winbindd</strong></span>, and a distributed <a class="indexterm" name="id2633936"></a>passdb backend
488 such as <em class="parameter"><code>ldap</code></em> will allow the establishment of a centrally managed, distributed user/password
489 database that can also be used by all PAM-aware (e.g., Linux) programs and applications. This arrangement can have
490 particularly potent advantages compared with the use of Microsoft Active Directory Service (ADS) insofar as
491 the reduction of wide-area network authentication traffic.
492 </p><div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Warning</h3><p>
493 The RID to UNIX ID database is the only location where the user and group mappings are
494 stored by <span><strong class="command">winbindd</strong></span>. If this file is deleted or corrupted, there is no way for <span><strong class="command">winbindd</strong></span>
495 to determine which user and group IDs correspond to Windows NT user and group RIDs.
496 </p></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2633978"></a>Password Synchronization Using <code class="filename">pam_smbpass.so</code></h3></div></div></div><p>
497 <code class="filename">pam_smbpass</code> is a PAM module that can be used on conforming systems to
498 keep the <code class="filename">smbpasswd</code> (Samba password) database in sync with the UNIX
499 password file. PAM is an API supported
500 under some UNIX operating systems, such as Solaris, HPUX, and Linux, that provides a
501 generic interface to authentication mechanisms.
503 This module authenticates a local <code class="filename">smbpasswd</code> user database. If you require
504 support for authenticating against a remote SMB server, or if you are
505 concerned about the presence of SUID root binaries on your system, it is
506 recommended that you use <code class="filename">pam_winbind</code> instead.
508 Options recognized by this module are shown in <a href="pam.html#smbpassoptions" title="Table 27.1. Options recognized by pam_smbpass">next table</a>.
509 </p><div class="table"><a name="smbpassoptions"></a><p class="title"><b>Table 27.1. Options recognized by <em class="parameter"><code>pam_smbpass</code></em></b></p><table summary="Options recognized by pam_smbpass" border="1"><colgroup><col align="left"><col align="justify"></colgroup><tbody><tr><td align="left">debug</td><td align="left">Log more debugging info.</td></tr><tr><td align="left">audit</td><td align="left">Like debug, but also logs unknown usernames.</td></tr><tr><td align="left">use_first_pass</td><td align="left">Do not prompt the user for passwords; take them from PAM_ items instead.</td></tr><tr><td align="left">try_first_pass</td><td align="left">Try to get the password from a previous PAM module; fall back to prompting the user.</td></tr><tr><td align="left">use_authtok</td><td align="left">Like try_first_pass, but *fail* if the new PAM_AUTHTOK has not been previously set (intended for stacking password modules only).</td></tr><tr><td align="left">not_set_pass</td><td align="left">Do not make passwords used by this module available to other modules.</td></tr><tr><td align="left">nodelay</td><td align="left">dDo not insert ~1-second delays on authentication failure.</td></tr><tr><td align="left">nullok</td><td align="left">Null passwords are allowed.</td></tr><tr><td align="left">nonull</td><td align="left">Null passwords are not allowed. Used to override the Samba configuration.</td></tr><tr><td align="left">migrate</td><td align="left">Only meaningful in an “<span class="quote">auth</span>” context; used to update smbpasswd file with a password used for successful authentication.</td></tr><tr><td align="left">smbconf=<em class="replaceable"><code>file</code></em></td><td align="left">Specify an alternate path to the <code class="filename">smb.conf</code> file.</td></tr></tbody></table></div><p>
511 The following are examples of the use of <code class="filename">pam_smbpass.so</code> in the format of the Linux
512 <code class="filename">/etc/pam.d/</code> files structure. Those wishing to implement this
513 tool on other platforms will need to adapt this appropriately.
514 </p><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2634197"></a>Password Synchronization Configuration</h4></div></div></div><p>
515 The following is a sample PAM configuration that shows the use of pam_smbpass to make
516 sure <code class="filename">private/smbpasswd</code> is kept in sync when <code class="filename">/etc/passwd (/etc/shadow)</code>
517 is changed. It is useful when an expired password might be changed by an
518 application (such as <span><strong class="command">ssh</strong></span>).
520 </p><pre class="programlisting">
524 auth requisite pam_nologin.so
525 auth required pam_unix.so
526 account required pam_unix.so
527 password requisite pam_cracklib.so retry=3
528 password requisite pam_unix.so shadow md5 use_authtok try_first_pass
529 password required pam_smbpass.so nullok use_authtok try_first_pass
530 session required pam_unix.so
531 </pre></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2634243"></a>Password Migration Configuration</h4></div></div></div><p>
532 The following PAM configuration shows the use of <code class="filename">pam_smbpass</code> to migrate
533 from plaintext to encrypted passwords for Samba. Unlike other methods,
534 this can be used for users who have never connected to Samba shares:
535 password migration takes place when users <span><strong class="command">ftp</strong></span> in, login using <span><strong class="command">ssh</strong></span>, pop
536 their mail, and so on.
538 </p><pre class="programlisting">
542 auth requisite pam_nologin.so
543 # pam_smbpass is called IF pam_unix succeeds.
544 auth requisite pam_unix.so
545 auth optional pam_smbpass.so migrate
546 account required pam_unix.so
547 password requisite pam_cracklib.so retry=3
548 password requisite pam_unix.so shadow md5 use_authtok try_first_pass
549 password optional pam_smbpass.so nullok use_authtok try_first_pass
550 session required pam_unix.so
551 </pre></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2634291"></a>Mature Password Configuration</h4></div></div></div><p>
552 The following is a sample PAM configuration for a mature <code class="filename">smbpasswd</code> installation.
553 <code class="filename">private/smbpasswd</code> is fully populated, and we consider it an error if
554 the SMB password does not exist or does not match the UNIX password.
556 </p><pre class="programlisting">
560 auth requisite pam_nologin.so
561 auth required pam_unix.so
562 account required pam_unix.so
563 password requisite pam_cracklib.so retry=3
564 password requisite pam_unix.so shadow md5 use_authtok try_first_pass
565 password required pam_smbpass.so use_authtok use_first_pass
566 session required pam_unix.so
567 </pre></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2634331"></a>Kerberos Password Integration Configuration</h4></div></div></div><p>
568 The following is a sample PAM configuration that shows <em class="parameter"><code>pam_smbpass</code></em> used together with
569 <em class="parameter"><code>pam_krb5</code></em>. This could be useful on a Samba PDC that is also a member of
572 </p><pre class="programlisting">
576 auth requisite pam_nologin.so
577 auth requisite pam_krb5.so
578 auth optional pam_smbpass.so migrate
579 account required pam_krb5.so
580 password requisite pam_cracklib.so retry=3
581 password optional pam_smbpass.so nullok use_authtok try_first_pass
582 password required pam_krb5.so use_authtok try_first_pass
583 session required pam_krb5.so
584 </pre></div></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2634372"></a>Common Errors</h2></div></div></div><p>
585 PAM can be fickle and sensitive to configuration glitches. Here we look at a few cases from
586 the Samba mailing list.
587 </p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2634383"></a>pam_winbind Problem</h3></div></div></div><p>
588 A user reported, <span class="emphasis"><em>I have the following PAM configuration</em></span>:
590 </p><pre class="programlisting">
591 auth required /lib/security/pam_securetty.so
592 auth sufficient /lib/security/pam_winbind.so
593 auth sufficient /lib/security/pam_unix.so use_first_pass nullok
594 auth required /lib/security/pam_stack.so service=system-auth
595 auth required /lib/security/pam_nologin.so
596 account required /lib/security/pam_stack.so service=system-auth
597 account required /lib/security/pam_winbind.so
598 password required /lib/security/pam_stack.so service=system-auth
601 <span class="emphasis"><em>When I open a new console with [ctrl][alt][F1], I can't log in with my user “<span class="quote">pitie.</span>”
602 I have tried with user “<span class="quote">scienceu\pitie</span>” also.</em></span>
604 The problem may lie with the inclusion of <em class="parameter"><code>pam_stack.so
605 service=system-auth</code></em>. That file often contains a lot of stuff that may
606 duplicate what you are already doing. Try commenting out the <em class="parameter"><code>pam_stack</code></em> lines
607 for <em class="parameter"><code>auth</code></em> and <em class="parameter"><code>account</code></em> and see if things work. If they do, look at
608 <code class="filename">/etc/pam.d/system-auth</code> and copy only what you need from it into your
609 <code class="filename">/etc/pam.d/login</code> file. Alternatively, if you want all services to use
610 Winbind, you can put the Winbind-specific stuff in <code class="filename">/etc/pam.d/system-auth</code>.
611 </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2634481"></a>Winbind Is Not Resolving Users and Groups</h3></div></div></div><p>
612 “<span class="quote">
613 My <code class="filename">smb.conf</code> file is correctly configured. I have specified
614 <a class="indexterm" name="id2634499"></a>idmap uid = 12000
615 and <a class="indexterm" name="id2634506"></a>idmap gid = 3000-3500,
616 and <span><strong class="command">winbind</strong></span> is running. When I do the following it all works fine.
618 </p><pre class="screen">
619 <code class="prompt">root# </code><strong class="userinput"><code>wbinfo -u</code></strong>
626 <code class="prompt">root# </code><strong class="userinput"><code>wbinfo -g</code></strong>
627 MIDEARTH\Domain Users
628 MIDEARTH\Domain Admins
629 MIDEARTH\Domain Guests
633 <code class="prompt">root# </code><strong class="userinput"><code>getent passwd</code></strong>
634 root:x:0:0:root:/root:/bin/bash
635 bin:x:1:1:bin:/bin:/bin/bash
637 maryo:x:15000:15003:Mary Orville:/home/MIDEARTH/maryo:/bin/false
639 “<span class="quote">
640 But this command fails:
642 </p><pre class="screen">
643 <code class="prompt">root# </code><strong class="userinput"><code>chown maryo a_file</code></strong>
644 chown: 'maryo': invalid user
646 “<span class="quote">This is driving me nuts! What can be wrong?</span>”
648 Your system is likely running <span><strong class="command">nscd</strong></span>, the name service
649 caching daemon. Shut it down, do not restart it! You will find your problem resolved.
650 </p></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ProfileMgmt.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="optional.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="integrate-ms-networks.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 26. Desktop Profile Management </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 28. Integrating MS Windows Networks with Samba</td></tr></table></div></body></html>
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