1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter�28.�PAM-Based Distributed Authentication</title><link rel="stylesheet" href="../samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.74.0"><link rel="home" href="index.html" title="The Official Samba 3.5.x HOWTO and Reference Guide"><link rel="up" href="optional.html" title="Part�III.�Advanced Configuration"><link rel="prev" href="ProfileMgmt.html" title="Chapter�27.�Desktop Profile Management"><link rel="next" href="integrate-ms-networks.html" title="Chapter�29.�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�28.�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�28.�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="orgname">Samba Team</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 class="email" 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 class="email" 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#id2665025">Features and Benefits</a></span></dt><dt><span class="sect1"><a href="pam.html#id2665655">Technical Discussion</a></span></dt><dd><dl><dt><span class="sect2"><a href="pam.html#id2665709">PAM Configuration Syntax</a></span></dt><dt><span class="sect2"><a href="pam.html#id2666709">Example System Configurations</a></span></dt><dt><span class="sect2"><a href="pam.html#id2667015">smb.conf PAM Configuration</a></span></dt><dt><span class="sect2"><a href="pam.html#id2667096">Remote CIFS Authentication Using winbindd.so</a></span></dt><dt><span class="sect2"><a href="pam.html#id2667199">Password Synchronization Using pam_smbpass.so</a></span></dt></dl></dd><dt><span class="sect1"><a href="pam.html#id2667593">Common Errors</a></span></dt><dd><dl><dt><span class="sect2"><a href="pam.html#id2667604">pam_winbind Problem</a></span></dt><dt><span class="sect2"><a href="pam.html#id2667702">Winbind Is Not Resolving Users and Groups</a></span></dt></dl></dd></dl></div><p> 2<a class="indexterm" name="id2664949"></a> 3<a class="indexterm" name="id2664956"></a> 4<a class="indexterm" name="id2664963"></a> 5<a class="indexterm" name="id2664969"></a> 6This chapter should help you to deploy Winbind-based authentication on any PAM-enabled 7UNIX/Linux system. Winbind can be used to enable user-level application access authentication 8from any MS Windows NT domain, MS Windows 200x Active Directory-based 9domain, or any Samba-based domain environment. It will also help you to configure PAM-based local host access 10controls that are appropriate to your Samba configuration. 11</p><p> 12<a class="indexterm" name="id2664987"></a> 13<a class="indexterm" name="id2664994"></a> 14In addition to knowing how to configure Winbind into PAM, you will learn generic PAM management 15possibilities 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> 17The use of Winbind requires more than PAM configuration alone. 18Please refer to <a class="link" href="winbind.html" title="Chapter�24.�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="id2665025"></a>Features and Benefits</h2></div></div></div><p> 20<a class="indexterm" name="id2665033"></a> 21<a class="indexterm" name="id2665039"></a> 22<a class="indexterm" name="id2665046"></a> 23<a class="indexterm" name="id2665053"></a> 24<a class="indexterm" name="id2665062"></a> 25<a class="indexterm" name="id2665069"></a> 26<a class="indexterm" name="id2665076"></a> 27<a class="indexterm" name="id2665083"></a> 28A number of UNIX systems (e.g., Sun Solaris), as well as the xxxxBSD family and Linux, 29now utilize the Pluggable Authentication Modules (PAM) facility to provide all authentication, 30authorization, and resource control services. Prior to the introduction of PAM, a decision 31to use an alternative to the system password database (<code class="filename">/etc/passwd</code>) 32would require the provision of alternatives for all programs that provide security services. 33Such a choice would involve provision of alternatives to programs such as <code class="literal">login</code>, 34<code class="literal">passwd</code>, <code class="literal">chown</code>, and so on. 35</p><p> 36<a class="indexterm" name="id2665124"></a> 37<a class="indexterm" name="id2665131"></a> 38<a class="indexterm" name="id2665138"></a> 39<a class="indexterm" name="id2665145"></a> 40PAM provides a mechanism that disconnects these security programs from the underlying 41authentication/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 43located in <code class="filename">/etc/pam.d</code>. 44</p><p> 45<a class="indexterm" name="id2665171"></a> 46<a class="indexterm" name="id2665178"></a> 47On PAM-enabled UNIX/Linux systems, it is an easy matter to configure the system to use any 48authentication backend so long as the appropriate dynamically loadable library modules 49are available for it. The backend may be local to the system or may be centralized on a 50remote server. 51</p><p> 52PAM 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="id2665208"></a> 55<a class="indexterm" name="id2665215"></a> 56<a class="indexterm" name="id2665222"></a> 57<a class="indexterm" name="id2665229"></a> 58<a class="indexterm" name="id2665236"></a> 59<a class="indexterm" name="id2665242"></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="id2665285"></a> 65<a class="indexterm" name="id2665292"></a> 66<a class="indexterm" name="id2665299"></a> 67<a class="indexterm" name="id2665305"></a> 68<a class="indexterm" name="id2665312"></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="id2665338"></a> 74<a class="indexterm" name="id2665345"></a> 75<a class="indexterm" name="id2665352"></a> 76<a class="indexterm" name="id2665358"></a> 77<a class="indexterm" name="id2665365"></a> 78<a class="indexterm" name="id2665372"></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="id2665400"></a> 84<a class="indexterm" name="id2665406"></a> 85<a class="indexterm" name="id2665413"></a> 86<a class="indexterm" name="id2665420"></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="id2665445"></a> 91<a class="indexterm" name="id2665452"></a> 92<a class="indexterm" name="id2665459"></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="id2665490"></a> 97<a class="indexterm" name="id2665497"></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="id2665522"></a> 102<a class="indexterm" name="id2665529"></a> 103<a class="indexterm" name="id2665536"></a> 104<a class="indexterm" name="id2665543"></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="id2665569"></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="id2665589"></a> 116<a class="indexterm" name="id2665596"></a> 117Of 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. 119</p><p> 120<a class="indexterm" name="id2665619"></a> 121<a class="indexterm" name="id2665626"></a> 122<a class="indexterm" name="id2665633"></a> 123<a class="indexterm" name="id2665640"></a> 124Once configured, these permit a remarkable level of flexibility in the location and use 125of distributed Samba domain controllers that can provide wide-area network bandwidth, 126efficient authentication services for PAM-capable systems. In effect, this allows the 127deployment of centrally managed and maintained distributed authentication from a 128single-user account database. 129</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2665655"></a>Technical Discussion</h2></div></div></div><p> 130<a class="indexterm" name="id2665663"></a> 131<a class="indexterm" name="id2665670"></a> 132<a class="indexterm" name="id2665677"></a> 133<a class="indexterm" name="id2665684"></a> 134PAM is designed to provide system administrators with a great deal of flexibility in 135configuration of the privilege-granting applications of their system. The local 136configuration of system security controlled by PAM is contained in one of two places: 137either 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="id2665709"></a>PAM Configuration Syntax</h3></div></div></div><p> 140<a class="indexterm" name="id2665717"></a> 141<a class="indexterm" name="id2665724"></a> 142In this section we discuss the correct syntax of and generic options respected by entries to these files. 143PAM-specific tokens in the configuration file are case insensitive. The module paths, however, are case 144sensitive, since they indicate a file's name and reflect the case dependence of typical file systems. The 145case sensitivity of the arguments to any given module is defined for each module in turn. 146</p><p> 147In addition to the lines described below, there are two special characters provided for the convenience 148of the system administrator: comments are preceded by a “<span class="quote">#</span>” and extend to the next end-of-line; also, 149module specification lines may be extended with a “<span class="quote">\</span>”-escaped newline. 150</p><p> 151<a class="indexterm" name="id2665755"></a> 152<a class="indexterm" name="id2665762"></a> 153If the PAM authentication module (loadable link library file) is located in the 154default location, then it is not necessary to specify the path. In the case of 155Linux, the default location is <code class="filename">/lib/security</code>. If the module 156is located outside the default, then the path must be specified as: 157</p><pre class="programlisting"> 158auth required /other_path/pam_strange_module.so 159</pre><p> 160</p><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2665788"></a>Anatomy of <code class="filename">/etc/pam.d</code> Entries</h4></div></div></div><p> 161The remaining information in this subsection was taken from the documentation of the Linux-PAM 162project. For more information on PAM, see 163<a class="ulink" href="http://ftp.kernel.org/pub/linux/libs/pam/" target="_top">the Official Linux-PAM home page</a>. 164</p><p> 165<a class="indexterm" name="id2665814"></a> 166A general configuration line of the <code class="filename">/etc/pam.conf</code> file has the following form: 167</p><pre class="programlisting"> 168service-name module-type control-flag module-path args 169</pre><p> 170</p><p> 171We explain the meaning of each of these tokens. The second (and more recently adopted) 172way of configuring Linux-PAM is via the contents of the <code class="filename">/etc/pam.d/</code> directory. 173Once 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="id2665859"></a> 176<a class="indexterm" name="id2665866"></a> 177<a class="indexterm" name="id2665873"></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, <code class="literal">ftpd</code>, <code class="literal">rlogind</code> and 180 <code class="literal">su</code>, and so on. 181 </p><p> 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> 185 entries are ignored. 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="id2665941"></a> 190<a class="indexterm" name="id2665947"></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. 196 </p></li><li><p> 197<a class="indexterm" name="id2665977"></a> 198<a class="indexterm" name="id2665983"></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. 203 </p></li><li><p> 204<a class="indexterm" name="id2666010"></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. 209 </p></li><li><p> 210<a class="indexterm" name="id2666032"></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. 223 </p><p> 224<a class="indexterm" name="id2666096"></a> 225<a class="indexterm" name="id2666103"></a> 226<a class="indexterm" name="id2666110"></a> 227<a class="indexterm" name="id2666117"></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>. 232 </p><p> 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. 238 </p></li><li><p> 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. 246 </p></li><li><p> 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. 252 </p></li><li><p> 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 ...] 265</pre><p> 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>. 275</pre><p> 276</p><p> 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. 278 </p><p> 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. 289 </p></li><li><p> 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. 293 </p></li><li><p> 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. 296 </p></li><li><p> 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. 302 </p></li><li><p> 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. 305 </p></li><li><p> 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: 312 </p><p> 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>. 315 </p></li><li><p> 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>. 317 </p></li><li><p> 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>. 319 </p></li><li><p> 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> 322 </p><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). 333 </p><p> 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. 338 </p><p> 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"> 341squid auth required pam_mysql.so user=passwd_query passwd=mada \ 342db=eminence [query=select user_name from internet_service where \ 343user_name=“<span class="quote">%u</span>” and password=PASSWORD(“<span class="quote">%p</span>”) and service=“<span class="quote">web_proxy</span>”] 344</pre><p> 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">\[</span>”. In other words, 347 </p><pre class="programlisting"> 348[..[..\]..] --> ..[..].. 349</pre><p> 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="id2666709"></a>Example System Configurations</h3></div></div></div><p> 354The following is an example <code class="filename">/etc/pam.d/login</code> configuration file. 355This example had all options uncommented and is probably not usable 356because it stacks many conditions before allowing successful completion 357of the login process. Essentially, all conditions can be disabled 358by 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="id2666735"></a>PAM: Original Login Config</h4></div></div></div><p> 360 </p><pre class="programlisting"> 361#%PAM-1.0 362# The PAM configuration file for the “<span class="quote">login</span>” service 363# 364auth required pam_securetty.so 365auth required pam_nologin.so 366# auth required pam_dialup.so 367# auth optional pam_mail.so 368auth required pam_pwdb.so shadow md5 369# account requisite pam_time.so 370account required pam_pwdb.so 371session required pam_pwdb.so 372# session optional pam_lastlog.so 373# password required pam_cracklib.so retry=3 374password required pam_pwdb.so shadow md5 375</pre><p> 376</p></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2666763"></a>PAM: Login Using <code class="filename">pam_smbpass</code></h4></div></div></div><p> 377PAM 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"> 380pam_access.so pam_ftp.so pam_limits.so 381pam_ncp_auth.so pam_rhosts_auth.so pam_stress.so 382pam_cracklib.so pam_group.so pam_listfile.so 383pam_nologin.so pam_rootok.so pam_tally.so 384pam_deny.so pam_issue.so pam_mail.so 385pam_permit.so pam_securetty.so pam_time.so 386pam_dialup.so pam_lastlog.so pam_mkhomedir.so 387pam_pwdb.so pam_shells.so pam_unix.so 388pam_env.so pam_ldap.so pam_motd.so 389pam_radius.so pam_smbpass.so pam_unix_acct.so 390pam_wheel.so pam_unix_auth.so pam_unix_passwd.so 391pam_userdb.so pam_warn.so pam_unix_session.so 392</pre><p> 393The following example for the login program replaces the use of 394the <code class="filename">pam_pwdb.so</code> module that uses the system 395password database (<code class="filename">/etc/passwd</code>, 396<code class="filename">/etc/shadow</code>, <code class="filename">/etc/group</code>) with 397the module <code class="filename">pam_smbpass.so</code>, which uses the Samba 398database containing the Microsoft MD4 encrypted password 399hashes. 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 403Samba implementation for your UNIX/Linux system. The 404<code class="filename">pam_smbpass.so</code> module is provided by 405Samba 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<code class="literal">configure</code> script. For more information 408on the <code class="filename">pam_smbpass</code> module, see the documentation 409in the <code class="filename">source/pam_smbpass</code> directory of the Samba 410source distribution. 411</p><p> 412 </p><pre class="programlisting"> 413#%PAM-1.0 414# The PAM configuration file for the “<span class="quote">login</span>” service 415# 416auth required pam_smbpass.so nodelay 417account required pam_smbpass.so nodelay 418session required pam_smbpass.so nodelay 419password required pam_smbpass.so nodelay 420</pre><p> 421The following is the PAM configuration file for a particular 422Linux system. The default condition uses <code class="filename">pam_pwdb.so</code>. 423</p><p> 424 </p><pre class="programlisting"> 425#%PAM-1.0 426# The PAM configuration file for the “<span class="quote">samba</span>” service 427# 428auth required pam_pwdb.so nullok nodelay shadow audit 429account required pam_pwdb.so audit nodelay 430session required pam_pwdb.so nodelay 431password required pam_pwdb.so shadow md5 432</pre><p> 433In the following example, the decision has been made to use the 434<code class="literal">smbpasswd</code> database even for basic Samba authentication. Such a 435decision could also be made for the <code class="literal">passwd</code> program and would 436thus allow the <code class="literal">smbpasswd</code> passwords to be changed using the 437<code class="literal">passwd</code> program: 438</p><p> 439 </p><pre class="programlisting"> 440#%PAM-1.0 441# The PAM configuration file for the “<span class="quote">samba</span>” service 442# 443auth required pam_smbpass.so nodelay 444account required pam_pwdb.so audit nodelay 445session required pam_pwdb.so nodelay 446password required pam_smbpass.so nodelay smbconf=/etc/samba.d/smb.conf 447</pre><p> 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 449also possible to pass information obtained within one PAM module through 450to the next module in the PAM stack. Please refer to the documentation for 451your particular system implementation for details regarding the specific 452capabilities of PAM in this environment. Some Linux implementations also 453provide the <code class="filename">pam_stack.so</code> module that allows all 454authentication to be configured in a single central file. The 455<code class="filename">pam_stack.so</code> method has some devoted followers 456on the basis that it allows for easier administration. As with all issues in 457life, though, every decision has trade-offs, so you may want to examine the 458PAM 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="id2667015"></a><code class="filename">smb.conf</code> PAM Configuration</h3></div></div></div><p> 460There is an option in <code class="filename">smb.conf</code> called <a class="link" href="smb.conf.5.html#OBEYPAMRESTRICTIONS" target="_top">obey pam restrictions</a>. 461The following is from the online help for this option in SWAT: 462</p><div class="blockquote"><blockquote class="blockquote"><p> 463When Samba is configured to enable PAM support (i.e., <code class="option">--with-pam</code>), this parameter will 464control whether or not Samba should obey PAM's account and session management directives. The default behavior 465is to use PAM for clear-text authentication only and to ignore any account or session management. Samba always 466ignores PAM for authentication in the case of <a class="link" href="smb.conf.5.html#ENCRYPTPASSWORDS" target="_top">encrypt passwords = yes</a>. 467The reason is that PAM modules cannot support the challenge/response authentication mechanism needed in the presence of SMB 468password encryption. 469</p><p>Default: <a class="link" href="smb.conf.5.html#OBEYPAMRESTRICTIONS" target="_top">obey pam restrictions = no</a></p></blockquote></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2667096"></a>Remote CIFS Authentication Using <code class="filename">winbindd.so</code></h3></div></div></div><p> 470All operating systems depend on the provision of user credentials acceptable to the platform. 471UNIX requires the provision of a user identifier (UID) as well as a group identifier (GID). 472These are both simple integer numbers that are obtained from a password backend such 473as <code class="filename">/etc/passwd</code>. 474</p><p> 475Users and groups on a Windows NT server are assigned a relative ID (RID) which is unique for 476the domain when the user or group is created. To convert the Windows NT user or group into 477a UNIX user or group, a mapping between RIDs and UNIX user and group IDs is required. This 478is one of the jobs that winbind performs. 479</p><p> 480As winbind users and groups are resolved from a server, user and group IDs are allocated 481from a specified range. This is done on a first come, first served basis, although all 482existing users and groups will be mapped as soon as a client performs a user or group 483enumeration command. The allocated UNIX IDs are stored in a database file under the Samba 484lock directory and will be remembered. 485</p><p> 486The astute administrator will realize from this that the combination of <code class="filename">pam_smbpass.so</code>, 487<code class="literal">winbindd</code>, and a distributed <a class="link" href="smb.conf.5.html#PASSDBBACKEND" target="_top">passdb backend</a> 488such as <em class="parameter"><code>ldap</code></em> will allow the establishment of a centrally managed, distributed user/password 489database that can also be used by all PAM-aware (e.g., Linux) programs and applications. This arrangement can have 490particularly potent advantages compared with the use of Microsoft Active Directory Service (ADS) insofar as 491the 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> 493The RID to UNIX ID database is the only location where the user and group mappings are 494stored by <code class="literal">winbindd</code>. If this file is deleted or corrupted, there is no way for <code class="literal">winbindd</code> 495to 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="id2667199"></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 498keep the <code class="filename">smbpasswd</code> (Samba password) database in sync with the UNIX 499password file. PAM is an API supported 500under some UNIX operating systems, such as Solaris, HPUX, and Linux, that provides a 501generic interface to authentication mechanisms. 502</p><p> 503This module authenticates a local <code class="filename">smbpasswd</code> user database. If you require 504support for authenticating against a remote SMB server, or if you are 505concerned about the presence of SUID root binaries on your system, it is 506recommended that you use <code class="filename">pam_winbind</code> instead. 507</p><p> 508Options recognized by this module are shown in <a class="link" href="pam.html#smbpassoptions" title="Table�28.1.�Options recognized by pam_smbpass">next table</a>. 509</p><div class="table"><a name="smbpassoptions"></a><p class="title"><b>Table�28.1.�Options recognized by <em class="parameter"><code>pam_smbpass</code></em></b></p><div class="table-contents"><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="justify">Log more debugging info.</td></tr><tr><td align="left">audit</td><td align="justify">Like debug, but also logs unknown usernames.</td></tr><tr><td align="left">use_first_pass</td><td align="justify">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="justify">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="justify">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="justify">Do not make passwords used by this module available to other modules.</td></tr><tr><td align="left">nodelay</td><td align="justify">dDo not insert ~1-second delays on authentication failure.</td></tr><tr><td align="left">nullok</td><td align="justify">Null passwords are allowed.</td></tr><tr><td align="left">nonull</td><td align="justify">Null passwords are not allowed. Used to override the Samba configuration.</td></tr><tr><td align="left">migrate</td><td align="justify">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="justify">Specify an alternate path to the <code class="filename">smb.conf</code> file.</td></tr></tbody></table></div></div><p><br class="table-break"> 510</p><p> 511The 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 513tool 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="id2667418"></a>Password Synchronization Configuration</h4></div></div></div><p> 515The following is a sample PAM configuration that shows the use of pam_smbpass to make 516sure <code class="filename">private/smbpasswd</code> is kept in sync when <code class="filename">/etc/passwd (/etc/shadow)</code> 517is changed. It is useful when an expired password might be changed by an 518application (such as <code class="literal">ssh</code>). 519</p><p> 520 </p><pre class="programlisting"> 521#%PAM-1.0 522# password-sync 523# 524auth requisite pam_nologin.so 525auth required pam_unix.so 526account required pam_unix.so 527password requisite pam_cracklib.so retry=3 528password requisite pam_unix.so shadow md5 use_authtok try_first_pass 529password required pam_smbpass.so nullok use_authtok try_first_pass 530session required pam_unix.so 531</pre></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2667464"></a>Password Migration Configuration</h4></div></div></div><p> 532The following PAM configuration shows the use of <code class="filename">pam_smbpass</code> to migrate 533from plaintext to encrypted passwords for Samba. Unlike other methods, 534this can be used for users who have never connected to Samba shares: 535password migration takes place when users <code class="literal">ftp</code> in, login using <code class="literal">ssh</code>, pop 536their mail, and so on. 537</p><p> 538 </p><pre class="programlisting"> 539#%PAM-1.0 540# password-migration 541# 542auth requisite pam_nologin.so 543# pam_smbpass is called IF pam_unix succeeds. 544auth requisite pam_unix.so 545auth optional pam_smbpass.so migrate 546account required pam_unix.so 547password requisite pam_cracklib.so retry=3 548password requisite pam_unix.so shadow md5 use_authtok try_first_pass 549password optional pam_smbpass.so nullok use_authtok try_first_pass 550session required pam_unix.so 551</pre></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2667512"></a>Mature Password Configuration</h4></div></div></div><p> 552The 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 554the SMB password does not exist or does not match the UNIX password. 555</p><p> 556</p><pre class="programlisting"> 557#%PAM-1.0 558# password-mature 559# 560auth requisite pam_nologin.so 561auth required pam_unix.so 562account required pam_unix.so 563password requisite pam_cracklib.so retry=3 564password requisite pam_unix.so shadow md5 use_authtok try_first_pass 565password required pam_smbpass.so use_authtok use_first_pass 566session required pam_unix.so 567</pre></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2667552"></a>Kerberos Password Integration Configuration</h4></div></div></div><p> 568The 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 570a Kerberos realm. 571</p><p> 572 </p><pre class="programlisting"> 573#%PAM-1.0 574# kdc-pdc 575# 576auth requisite pam_nologin.so 577auth requisite pam_krb5.so 578auth optional pam_smbpass.so migrate 579account required pam_krb5.so 580password requisite pam_cracklib.so retry=3 581password optional pam_smbpass.so nullok use_authtok try_first_pass 582password required pam_krb5.so use_authtok try_first_pass 583session 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="id2667593"></a>Common Errors</h2></div></div></div><p> 585PAM can be fickle and sensitive to configuration glitches. Here we look at a few cases from 586the Samba mailing list. 587</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2667604"></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>: 589 </p><p> 590</p><pre class="programlisting"> 591auth required /lib/security/pam_securetty.so 592auth sufficient /lib/security/pam_winbind.so 593auth sufficient /lib/security/pam_unix.so use_first_pass nullok 594auth required /lib/security/pam_stack.so service=system-auth 595auth required /lib/security/pam_nologin.so 596account required /lib/security/pam_stack.so service=system-auth 597account required /lib/security/pam_winbind.so 598password required /lib/security/pam_stack.so service=system-auth 599</pre><p> 600</p><p> 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> 603 </p><p> 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="id2667702"></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="link" href="smb.conf.5.html#IDMAPUID" target="_top">idmap uid = 12000</a> 615 and <a class="link" href="smb.conf.5.html#IDMAPGID" target="_top">idmap gid = 3000-3500,</a> 616 and <code class="literal">winbind</code> is running. When I do the following it all works fine. 617 </span>” 618 </p><pre class="screen"> 619<code class="prompt">root# </code><strong class="userinput"><code>wbinfo -u</code></strong> 620MIDEARTH\maryo 621MIDEARTH\jackb 622MIDEARTH\ameds 623... 624MIDEARTH\root 625 626<code class="prompt">root# </code><strong class="userinput"><code>wbinfo -g</code></strong> 627MIDEARTH\Domain Users 628MIDEARTH\Domain Admins 629MIDEARTH\Domain Guests 630... 631MIDEARTH\Accounts 632 633<code class="prompt">root# </code><strong class="userinput"><code>getent passwd</code></strong> 634root:x:0:0:root:/root:/bin/bash 635bin:x:1:1:bin:/bin:/bin/bash 636... 637maryo:x:15000:15003:Mary Orville:/home/MIDEARTH/maryo:/bin/false 638</pre><p> 639 “<span class="quote"> 640 But this command fails: 641 </span>” 642</p><pre class="screen"> 643<code class="prompt">root# </code><strong class="userinput"><code>chown maryo a_file</code></strong> 644chown: 'maryo': invalid user 645</pre><p> 646 “<span class="quote">This is driving me nuts! What can be wrong?</span>” 647 </p><p> 648 Your system is likely running <code class="literal">nscd</code>, 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�27.�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�29.�Integrating MS Windows Networks with Samba</td></tr></table></div></body></html> 651