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   1 <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 25. PAM-Based Distributed Authentication</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.60.1"><link rel="home" href="index.html" title="SAMBA Project Documentation"><link rel="up" href="optional.html" title="Part III. Advanced Configuration"><link rel="previous" href="ProfileMgmt.html" title="Chapter 24. Desktop Profile Management"><link rel="next" href="integrate-ms-networks.html" title="Chapter 26. 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 25. 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 25. 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><tt class="email">&lt;<a href="mailto:jht@samba.org">jht@samba.org</a>&gt;</tt></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><tt class="email">&lt;<a href="mailto:vorlon@netexpress.net">vorlon@netexpress.net</a>&gt;</tt></p></div></div></div></div><div><p class="pubdate">May 31, 2003</p></div></div><div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><a href="pam.html#id2958910">Features and Benefits</a></dt><dt><a href="pam.html#id2959235">Technical Discussion</a></dt><dd><dl><dt><a href="pam.html#id2959266">PAM Configuration Syntax</a></dt><dt><a href="pam.html#id2960262">Example System Configurations</a></dt><dt><a href="pam.html#id2960612">smb.conf PAM Configuration</a></dt><dt><a href="pam.html#id2960701">Remote CIFS Authentication Using winbindd.so</a></dt><dt><a href="pam.html#id2960824">Password Synchronization Using pam_smbpass.so</a></dt></dl></dd><dt><a href="pam.html#id2961283">Common Errors</a></dt><dd><dl><dt><a href="pam.html#id2961296">pam_winbind Problem</a></dt><dt><a href="pam.html#id2961406">Winbind Is Not Resolving Users and Groups</a></dt></dl></dd></dl></div><p>
   2 This chapter should help you to deploy Winbind-based authentication on any PAM-enabled
   3 UNIX/Linux system. Winbind can be used to enable User-Level application access authentication
   4 from any MS Windows NT Domain, MS Windows 200x Active Directory-based
   5 domain, or any Samba-based domain environment. It will also help you to configure PAM-based local host access
   6 controls that are appropriate to your Samba configuration.
   7 </p><p>
   8 In addition to knowing how to configure Winbind into PAM, you will learn generic PAM management
   9 possibilities and in particular how to deploy tools like <tt class="filename">pam_smbpass.so</tt> to your advantage.
  10 </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
  11 The use of Winbind requires more than PAM configuration alone.
  12 Please refer to <link linkend="winbind">, for further information regarding Winbind.
  13 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2958910"></a>Features and Benefits</h2></div></div><div></div></div><p>
  14 A number of UNIX systems (e.g., Sun Solaris), as well as the xxxxBSD family and Linux,
  15 now utilize the Pluggable Authentication Modules (PAM) facility to provide all authentication,
  16 authorization and resource control services. Prior to the introduction of PAM, a decision
  17 to use an alternative to the system password database (<tt class="filename">/etc/passwd</tt>)
  18 would require the provision of alternatives for all programs that provide security services.
  19 Such a choice would involve provision of alternatives to programs such as: <b class="command">login</b>,
  20 <b class="command">passwd</b>, <b class="command">chown</b>, and so on.
  21 </p><p>
  22 PAM provides a mechanism that disconnects these security programs from the underlying
  23 authentication/authorization infrastructure. PAM is configured by making appropriate modifications to  one file
  24 <tt class="filename">/etc/pam.conf</tt> (Solaris), or by editing individual control files that are
  25 located in <tt class="filename">/etc/pam.d</tt>.
  26 </p><p>
  27 On PAM-enabled UNIX/Linux systems, it is an easy matter to configure the system to use any
  28 authentication backend so long as the appropriate dynamically loadable library modules
  29 are available for it. The backend may be local to the system, or may be centralized on a
  30 remote server.
  31 </p><p>
  32 PAM support modules are available for:
  33 </p><div class="variablelist"><dl><dt><span class="term"><tt class="filename">/etc/passwd</tt></span></dt><dd><p>
  34                 There are several PAM modules that interact with this standard UNIX user
  35                 database. The most common are called: <tt class="filename">pam_unix.so</tt>, <tt class="filename">pam_unix2.so</tt>, <tt class="filename">pam_pwdb.so</tt>
  36                 and <tt class="filename">pam_userdb.so</tt>.
  37                 </p></dd><dt><span class="term">Kerberos</span></dt><dd><p>
  38                 The <tt class="filename">pam_krb5.so</tt> module allows the use of any Kerberos compliant server.
  39                 This tool is used to access MIT Kerberos, Heimdal Kerberos, and potentially
  40                 Microsoft Active Directory (if enabled).
  41                 </p></dd><dt><span class="term">LDAP</span></dt><dd><p>
  42                 The <tt class="filename">pam_ldap.so</tt> module allows the use of any LDAP v2 or v3 compatible backend
  43                 server. Commonly used LDAP backend servers include: OpenLDAP v2.0 and v2.1,
  44                 Sun ONE iDentity server, Novell eDirectory server, Microsoft Active Directory.
  45                 </p></dd><dt><span class="term">NetWare Bindery</span></dt><dd><p>
  46                 The <tt class="filename">pam_ncp_auth.so</tt> module allows authentication off any bindery-enabled
  47                 NetWare Core Protocol-based server.
  48                 </p></dd><dt><span class="term">SMB Password</span></dt><dd><p>
  49                 This module, called <tt class="filename">pam_smbpass.so</tt>, will allow user authentication off
  50                 the passdb backend that is configured in the Samba <tt class="filename">smb.conf</tt> file.
  51                 </p></dd><dt><span class="term">SMB Server</span></dt><dd><p>
  52                 The <tt class="filename">pam_smb_auth.so</tt> module is the original MS Windows networking authentication
  53                 tool. This module has been somewhat outdated by the Winbind module.
  54                 </p></dd><dt><span class="term">Winbind</span></dt><dd><p>
  55                 The <tt class="filename">pam_winbind.so</tt> module allows Samba to obtain authentication from any
  56                 MS Windows Domain Controller. It can just as easily be used to authenticate
  57                 users for access to any PAM-enabled application.
  58                 </p></dd><dt><span class="term">RADIUS</span></dt><dd><p>
  59                 There is a PAM RADIUS (Remote Access Dial-In User Service) authentication
  60                 module. In most cases, administrators will need to locate the source code
  61                 for this tool and compile and install it themselves. RADIUS protocols are
  62                 used by many routers and terminal servers.
  63                 </p></dd></dl></div><p>
  64 Of the above, Samba provides the <tt class="filename">pam_smbpasswd.so</tt> and the <tt class="filename">pam_winbind.so</tt> modules alone.
  65 </p><p>
  66 Once configured, these permit a remarkable level of flexibility in the location and use
  67 of distributed Samba Domain Controllers that can provide wide area network bandwidth
  68 efficient authentication services for PAM-capable systems. In effect, this allows the
  69 deployment of centrally managed and maintained distributed authentication from a
  70 single-user account database.
  71 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2959235"></a>Technical Discussion</h2></div></div><div></div></div><p>
  72 PAM is designed to provide the system administrator with a great deal of flexibility in
  73 configuration of the privilege granting applications of their system. The local
  74 configuration of system security controlled by PAM is contained in one of two places:
  75 either the single system file, <tt class="filename">/etc/pam.conf</tt>, or the
  76 <tt class="filename">/etc/pam.d/</tt> directory.
  77 </p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2959266"></a>PAM Configuration Syntax</h3></div></div><div></div></div><p>
  78 In this section we discuss the correct syntax of and generic options respected by entries to these files.
  79 PAM-specific tokens in the configuration file are case insensitive. The module paths, however, are case
  80 sensitive since they indicate a file's name and reflect the case
  81 dependence of typical file systems.
  82 The case-sensitivity of the arguments to any given module is defined for each module in turn.
  83 </p><p>
  84 In addition to the lines described below, there are two special characters provided for the convenience
  85 of the system administrator: comments are preceded by a &#8220;<span class="quote">#</span>&#8221; and extend to the next end-of-line; also,
  86 module specification lines may be extended with a &#8220;<span class="quote">\</span>&#8221; escaped newline.
  87 </p><p>
  88 If the PAM authentication module (loadable link library file) is located in the
  89 default location, then it is not necessary to specify the path. In the case of
  90 Linux, the default location is <tt class="filename">/lib/security</tt>. If the module
  91 is located outside the default, then the path must be specified as:
  92 </p><p>
  93 </p><pre class="programlisting">
  94 auth  required  /other_path/pam_strange_module.so
  95 </pre><p>
  96 </p><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2959332"></a>Anatomy of <tt class="filename">/etc/pam.d</tt> Entries</h4></div></div><div></div></div><p>
  97 The remaining information in this subsection was taken from the documentation of the Linux-PAM
  98 project. For more information on PAM, see
  99 <ulink url="http://ftp.kernel.org/pub/linux/libs/pam/">The Official Linux-PAM home page.</ulink>
 100 </p><p>
 101 A general configuration line of the <tt class="filename">/etc/pam.conf</tt> file has the following form:
 102 </p><p>
 103 </p><pre class="programlisting">
 104 service-name   module-type   control-flag   module-path   args
 105 </pre><p>
 106 </p><p>
 107 Below, we explain the meaning of each of these tokens. The second (and more recently adopted)
 108 way of configuring Linux-PAM is via the contents of the <tt class="filename">/etc/pam.d/</tt> directory.
 109 Once we have explained the meaning of the above tokens, we will describe this method.
 110 </p><div class="variablelist"><dl><dt><span class="term">service-name</span></dt><dd><p>
 111                 The name of the service associated with this entry. Frequently, the service name is the conventional
 112                 name of the given application. For example, <b class="command">ftpd</b>, <b class="command">rlogind</b> and
 113                 <b class="command">su</b>, and so on.
 114                 </p><p>
 115                 There is a special service-name reserved for defining a default authentication mechanism. It has
 116                 the name <i class="parameter"><tt>OTHER</tt></i> and may be specified in either lower- or upper-case characters.
 117                 Note, when there is a module specified for a named service, the <i class="parameter"><tt>OTHER</tt></i>
 118                 entries are ignored.
 119                 </p></dd><dt><span class="term">module-type</span></dt><dd><p>
 120                 One of (currently) four types of module. The four types are as follows:
 121                 </p><div class="itemizedlist"><ul type="disc"><li><p>
 122                         <i class="parameter"><tt>auth:</tt></i> This module type provides two aspects of authenticating the user.
 123                         It establishes that the user is who he claims to be by instructing the application
 124                         to prompt the user for a password or other means of identification. Secondly, the module can
 125                         grant group membership (independently of the <tt class="filename">/etc/groups</tt> file discussed
 126                         above) or other privileges through its credential granting properties.
 127                         </p></li><li><p>
 128                         <i class="parameter"><tt>account:</tt></i> This module performs non-authentication-based account management.
 129                         It is typically used to restrict/permit access to a service based on the time of day, currently
 130                         available system resources (maximum number of users) or perhaps the location of the applicant
 131                         user &#8220;<span class="quote">root</span>&#8221; login only on the console.
 132                         </p></li><li><p>
 133                         <i class="parameter"><tt>session:</tt></i> Primarily, this module is associated with doing things that need
 134                         to be done for the user before and after they can be given service. Such things include the logging
 135                         of information concerning the opening and closing of some data exchange with a user, mounting
 136                         directories, and so on.
 137                         </p></li><li><p>
 138                         <i class="parameter"><tt>password:</tt></i> This last module type is required for updating the authentication
 139                         token associated with the user. Typically, there is one module for each &#8220;<span class="quote">challenge/response</span>&#8221;
 140                         -based authentication <i class="parameter"><tt>(auth)</tt></i> module type.
 141                         </p></li></ul></div></dd><dt><span class="term">control-flag</span></dt><dd><p>
 142                 The control-flag is used to indicate how the PAM library will react to the success or failure of the
 143                 module it is associated with. Since modules can be stacked (modules of the same type execute in series,
 144                 one after another), the control-flags determine the relative importance of each module. The application
 145                 is not made aware of the individual success or failure of modules listed in the
 146                 <tt class="filename">/etc/pam.conf</tt> file. Instead, it receives a summary success or fail response from
 147                 the Linux-PAM library. The order of execution of these modules is that of the entries in the
 148                 <tt class="filename">/etc/pam.conf</tt> file; earlier entries are executed before later ones.
 149                 As of Linux-PAM v0.60, this control-flag can be defined with one of two syntaxes.
 150                 </p><p>
 151                 The simpler (and historical) syntax for the control-flag is a single keyword defined to indicate the
 152                 severity of concern associated with the success or failure of a specific module. There are four such
 153                 keywords: <i class="parameter"><tt>required, requisite, sufficient and optional</tt></i>.
 154                 </p><p>
 155                 The Linux-PAM library interprets these keywords in the following manner:
 156                 </p><div class="itemizedlist"><ul type="disc"><li><p>
 157                         <i class="parameter"><tt>required:</tt></i> This indicates that the success of the module is required for the
 158                         module-type facility to succeed. Failure of this module will not be apparent to the user until all
 159                         of the remaining modules (of the same module-type) have been executed.
 160                         </p></li><li><p>
 161                         <i class="parameter"><tt>requisite:</tt></i> Like required, however, in the case that such a module returns a
 162                         failure, control is directly returned to the application. The return value is that associated with
 163                         the first required or requisite module to fail. This flag can be used to protect against the
 164                         possibility of a user getting the opportunity to enter a password over an unsafe medium. It is
 165                         conceivable that such behavior might inform an attacker of valid accounts on a system. This
 166                         possibility should be weighed against the not insignificant concerns of exposing a sensitive
 167                         password in a hostile environment.
 168                         </p></li><li><p>
 169                         <i class="parameter"><tt>sufficient:</tt></i> The success of this module is deemed <i class="parameter"><tt>sufficient</tt></i> to satisfy
 170                         the Linux-PAM library that this module-type has succeeded in its purpose. In the event that no
 171                         previous required module has failed, no more &#8220;<span class="quote">stacked</span>&#8221; modules of this type are invoked.
 172                         (In this case, subsequent required modules are not invoked). A failure of this module is not deemed
 173                         as fatal to satisfying the application that this module-type has succeeded.
 174                         </p></li><li><p>
 175                         <i class="parameter"><tt>optional:</tt></i> As its name suggests, this control-flag marks the module as not
 176                         being critical to the success or failure of the user's application for service. In general,
 177                         Linux-PAM ignores such a module when determining if the module stack will succeed or fail.
 178                         However, in the absence of any definite successes or failures of previous or subsequent stacked
 179                         modules, this module will determine the nature of the response to the application. One example of
 180                         this latter case, is when the other modules return something like PAM_IGNORE.
 181                         </p></li></ul></div><p>
 182                 The more elaborate (newer) syntax is much more specific and gives the administrator a great deal of control
 183                 over how the user is authenticated. This form of the control flag is delimited with square brackets and
 184                 consists of a series of <i class="parameter"><tt>value=action</tt></i> tokens:
 185                 </p><pre class="programlisting">
 186 [value1=action1 value2=action2 ...]
 187 </pre><p>
 188                 Here, <i class="parameter"><tt>value1</tt></i> is one of the following return values:
 189 </p><pre class="screen">
 190 <i class="parameter"><tt>success; open_err; symbol_err; service_err; system_err; buf_err;</tt></i>
 191 <i class="parameter"><tt>perm_denied; auth_err; cred_insufficient; authinfo_unavail;</tt></i>
 192 <i class="parameter"><tt>user_unknown; maxtries; new_authtok_reqd; acct_expired; session_err;</tt></i>
 193 <i class="parameter"><tt>cred_unavail; cred_expired; cred_err; no_module_data; conv_err;</tt></i>
 194 <i class="parameter"><tt>authtok_err; authtok_recover_err; authtok_lock_busy;</tt></i>
 195 <i class="parameter"><tt>authtok_disable_aging; try_again; ignore; abort; authtok_expired;</tt></i>
 196 <i class="parameter"><tt>module_unknown; bad_item;</tt></i> and <i class="parameter"><tt>default</tt></i>.
 197 </pre><p>
 198 </p><p>
 199                 The last of these <i class="parameter"><tt>(default)</tt></i> can be used to set the action for those return values that are not explicitly defined.
 200                 </p><p>
 201                 The <i class="parameter"><tt>action1</tt></i> can be a positive integer or one of the following tokens:
 202                 <i class="parameter"><tt>ignore; ok; done; bad; die;</tt></i> and <i class="parameter"><tt>reset</tt></i>.
 203                 A positive integer, J, when specified as the action, can be used to indicate that the next J modules of the
 204                 current module-type will be skipped. In this way, the administrator can develop a moderately sophisticated
 205                 stack of modules with a number of different paths of execution. Which path is taken can be determined by the
 206                 reactions of individual modules.
 207                 </p><div class="itemizedlist"><ul type="disc"><li><p>
 208                         <i class="parameter"><tt>ignore:</tt></i> When used with a stack of modules, the module's return status will not
 209                         contribute to the return code the application obtains.
 210                         </p></li><li><p>
 211                         <i class="parameter"><tt>bad:</tt></i> This action indicates that the return code should be thought of as indicative
 212                         of the module failing. If this module is the first in the stack to fail, its status value will be used
 213                         for that of the whole stack.
 214                         </p></li><li><p>
 215                         <i class="parameter"><tt>die:</tt></i> Equivalent to bad with the side effect of terminating the module stack and
 216                         PAM immediately returning to the application.
 217                         </p></li><li><p>
 218                         <i class="parameter"><tt>ok:</tt></i> This tells PAM that the administrator thinks this return code should
 219                         contribute directly to the return code of the full stack of modules. In other words, if the former
 220                         state of the stack would lead to a return of PAM_SUCCESS, the module's return code will override
 221                         this value. Note, if the former state of the stack holds some value that is indicative of a modules
 222                         failure, this <i class="parameter"><tt>ok</tt></i> value will not be used to override that value.
 223                         </p></li><li><p>
 224                         <i class="parameter"><tt>done:</tt></i> Equivalent to <i class="parameter"><tt>ok</tt></i> with the side effect of terminating the module stack and
 225                         PAM immediately returning to the application.
 226                         </p></li><li><p>
 227                         <i class="parameter"><tt>reset:</tt></i> Clears all memory of the state of the module stack and starts again with
 228                         the next stacked module.
 229                         </p></li></ul></div><p>
 230                 Each of the four keywords: <i class="parameter"><tt>required; requisite; sufficient;</tt></i> and <i class="parameter"><tt>optional</tt></i>,
 231                 have an equivalent expression in terms of the [...] syntax. They are as follows:
 232                 </p><p>
 233                 </p><div class="itemizedlist"><ul type="disc"><li><p>
 234                         <i class="parameter"><tt>required</tt></i> is equivalent to <i class="parameter"><tt>[success=ok new_authtok_reqd=ok ignore=ignore default=bad]</tt></i>.
 235                         </p></li><li><p>
 236                         <i class="parameter"><tt>requisite</tt></i> is equivalent to <i class="parameter"><tt>[success=ok new_authtok_reqd=ok ignore=ignore default=die]</tt></i>.
 237                         </p></li><li><p>
 238                                         <i class="parameter"><tt>sufficient</tt></i> is equivalent to <i class="parameter"><tt>[success=done new_authtok_reqd=done default=ignore]</tt></i>.
 239                         </p></li><li><p>
 240                         <i class="parameter"><tt>optional</tt></i> is equivalent to <i class="parameter"><tt>[success=ok new_authtok_reqd=ok default=ignore]</tt></i>.
 241                         </p></li></ul></div><p>
 242                 </p><p>
 243                 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,
 244                 the notion of client plug-in agents was introduced. This is something that makes it possible for PAM to support
 245                 machine-machine authentication using the transport protocol inherent to the client/server application. With the
 246                 <i class="parameter"><tt>[ ... value=action ... ]</tt></i> control syntax, it is possible for an application to be configured
 247                 to support binary prompts with compliant clients, but to gracefully fall over into an alternative authentication
 248                 mode for older, legacy applications.
 249                 </p></dd><dt><span class="term">module-path</span></dt><dd><p>
 250                 The path-name of the dynamically loadable object file; the pluggable module itself. If the first character of the
 251                 module path is &#8220;<span class="quote">/</span>&#8221;, it is assumed to be a complete path. If this is not the case, the given module path is appended
 252                 to the default module path: <tt class="filename">/lib/security</tt> (but see the notes above).
 253                 </p><p>
 254                 The arguments are a list of tokens that are passed to the module when it is invoked, much like arguments to a typical
 255                 Linux shell command. Generally, valid arguments are optional and are specific to any given module. Invalid arguments
 256                 are ignored by a module, however, when encountering an invalid argument, the module is required to write an error
 257                 to syslog(3). For a list of generic options, see the next section.
 258                 </p><p>
 259                 If you wish to include spaces in an argument, you should surround that argument with square brackets. For example:
 260                 </p><pre class="programlisting">
 261 squid auth required pam_mysql.so user=passwd_query passwd=mada \
 262 db=eminence [query=select user_name from internet_service where \
 263 user_name=&#8220;<span class="quote">%u</span>&#8221; and password=PASSWORD(&#8220;<span class="quote">%p</span>&#8221;) and service=&#8220;<span class="quote">web_proxy</span>&#8221;]
 264 </pre><p>
 265                 When using this convention, you can include &#8220;<span class="quote">[</span>&#8221; characters inside the string, and if you wish to have a &#8220;<span class="quote">]</span>&#8221;
 266                 character inside the string that will survive the argument parsing, you should use &#8220;<span class="quote">\[</span>&#8221;. In other words:
 267                 </p><pre class="programlisting">
 268 [..[..\]..]    --&gt;   ..[..]..
 269 </pre><p>
 270                 Any line in one of the configuration files that is not formatted correctly will generally tend (erring on the
 271                 side of caution) to make the authentication process fail. A corresponding error is written to the system log files
 272                 with a call to syslog(3).
 273                 </p></dd></dl></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2960262"></a>Example System Configurations</h3></div></div><div></div></div><p>
 274 The following is an example <tt class="filename">/etc/pam.d/login</tt> configuration file.
 275 This example had all options uncommented and is probably not usable
 276 because it stacks many conditions before allowing successful completion
 277 of the login process. Essentially all conditions can be disabled
 278 by commenting them out, except the calls to <tt class="filename">pam_pwdb.so</tt>.
 279 </p><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2960294"></a>PAM: Original Login Config</h4></div></div><div></div></div><pre class="programlisting">
 280 #%PAM-1.0
 281 # The PAM configuration file for the &#8220;<span class="quote">login</span>&#8221; service
 282 #
 283 auth         required    pam_securetty.so
 284 auth         required    pam_nologin.so
 285 # auth       required    pam_dialup.so
 286 # auth       optional    pam_mail.so
 287 auth         required    pam_pwdb.so shadow md5
 288 # account    requisite   pam_time.so
 289 account      required    pam_pwdb.so
 290 session      required    pam_pwdb.so
 291 # session    optional    pam_lastlog.so
 292 # password   required    pam_cracklib.so retry=3
 293 password     required    pam_pwdb.so shadow md5
 294 </pre></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2960324"></a>PAM: Login Using <tt class="filename">pam_smbpass</tt></h4></div></div><div></div></div><p>
 295 PAM allows use of replaceable modules. Those available on a sample system include:
 296 </p><p><tt class="prompt">$</tt><b class="userinput"><tt>/bin/ls /lib/security</tt></b>
 297 </p><pre class="programlisting">
 298 pam_access.so    pam_ftp.so          pam_limits.so
 299 pam_ncp_auth.so  pam_rhosts_auth.so  pam_stress.so
 300 pam_cracklib.so  pam_group.so        pam_listfile.so
 301 pam_nologin.so   pam_rootok.so       pam_tally.so
 302 pam_deny.so      pam_issue.so        pam_mail.so
 303 pam_permit.so    pam_securetty.so    pam_time.so
 304 pam_dialup.so    pam_lastlog.so      pam_mkhomedir.so
 305 pam_pwdb.so      pam_shells.so       pam_UNIX.so
 306 pam_env.so       pam_ldap.so         pam_motd.so
 307 pam_radius.so    pam_smbpass.so      pam_UNIX_acct.so
 308 pam_wheel.so     pam_UNIX_auth.so    pam_UNIX_passwd.so
 309 pam_userdb.so    pam_warn.so         pam_UNIX_session.so
 310 </pre><p>
 311 The following example for the login program replaces the use of
 312 the <tt class="filename">pam_pwdb.so</tt> module that uses the system
 313 password database (<tt class="filename">/etc/passwd</tt>,
 314 <tt class="filename">/etc/shadow</tt>, <tt class="filename">/etc/group</tt>) with
 315 the module <tt class="filename">pam_smbpass.so</tt>, which uses the Samba
 316 database which contains the Microsoft MD4 encrypted password
 317 hashes. This database is stored in either
 318 <tt class="filename">/usr/local/samba/private/smbpasswd</tt>,
 319 <tt class="filename">/etc/samba/smbpasswd</tt>, or in
 320 <tt class="filename">/etc/samba.d/smbpasswd</tt>, depending on the
 321 Samba implementation for your UNIX/Linux system. The
 322 <tt class="filename">pam_smbpass.so</tt> module is provided by
 323 Samba version 2.2.1 or later. It can be compiled by specifying the
 324 <tt class="option">--with-pam_smbpass</tt> options when running Samba's
 325 <b class="command">configure</b> script. For more information
 326 on the <tt class="filename">pam_smbpass</tt> module, see the documentation
 327 in the <tt class="filename">source/pam_smbpass</tt> directory of the Samba
 328 source distribution.
 329 </p><pre class="programlisting">
 330 #%PAM-1.0
 331 # The PAM configuration file for the &#8220;<span class="quote">login</span>&#8221; service
 332 #
 333 auth        required    pam_smbpass.so nodelay
 334 account     required    pam_smbpass.so nodelay
 335 session     required    pam_smbpass.so nodelay
 336 password    required    pam_smbpass.so nodelay
 337 </pre><p>
 338 The following is the PAM configuration file for a particular
 339 Linux system. The default condition uses <tt class="filename">pam_pwdb.so</tt>.
 340 </p><pre class="programlisting">
 341 #%PAM-1.0
 342 # The PAM configuration file for the &#8220;<span class="quote">samba</span>&#8221; service
 343 #
 344 auth       required     pam_pwdb.so nullok nodelay shadow audit
 345 account    required     pam_pwdb.so audit nodelay
 346 session    required     pam_pwdb.so nodelay
 347 password   required     pam_pwdb.so shadow md5
 348 </pre><p>
 349 In the following example, the decision has been made to use the
 350 <b class="command">smbpasswd</b> database even for basic Samba authentication. Such a
 351 decision could also be made for the <b class="command">passwd</b> program and would
 352 thus allow the <b class="command">smbpasswd</b> passwords to be changed using the
 353 <b class="command">passwd</b> program:
 354 </p><pre class="programlisting">
 355 #%PAM-1.0
 356 # The PAM configuration file for the &#8220;<span class="quote">samba</span>&#8221; service
 357 #
 358 auth       required     pam_smbpass.so nodelay
 359 account    required     pam_pwdb.so audit nodelay
 360 session    required     pam_pwdb.so nodelay
 361 password   required     pam_smbpass.so nodelay smbconf=/etc/samba.d/smb.conf
 362 </pre><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
 363 also possible to pass information obtained within one PAM module through
 364 to the next module in the PAM stack. Please refer to the documentation for
 365 your particular system implementation for details regarding the specific
 366 capabilities of PAM in this environment. Some Linux implementations also
 367 provide the <tt class="filename">pam_stack.so</tt> module that allows all
 368 authentication to be configured in a single central file. The
 369 <tt class="filename">pam_stack.so</tt> method has some devoted followers
 370 on the basis that it allows for easier administration. As with all issues in
 371 life though, every decision makes trade-offs, so you may want to examine the
 372 PAM documentation for further helpful information.
 373 </p></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2960612"></a><tt class="filename">smb.conf</tt> PAM Configuration</h3></div></div><div></div></div><p>
 374         There is an option in <tt class="filename">smb.conf</tt> called <a class="indexterm" name="id2960633"></a><i class="parameter"><tt>obey pam restrictions</tt></i>.
 375 The following is from the online help for this option in SWAT;
 376 </p><p>
 377 When Samba is configured to enable PAM support (i.e., <tt class="option">--with-pam</tt>), this parameter will
 378 control whether or not Samba should obey PAM's account and session management directives. The default behavior
 379 is to use PAM for cleartext authentication only and to ignore any account or session management. Samba always
 380 ignores PAM for authentication in the case of <a class="indexterm" name="id2960663"></a><i class="parameter"><tt>encrypt passwords</tt></i> = yes.
 381 The reason is that PAM modules cannot support the challenge/response authentication mechanism needed in the presence of SMB
 382 password encryption.
 383 </p><p>Default: <a class="indexterm" name="id2960684"></a><i class="parameter"><tt>obey pam restrictions</tt></i> = no</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2960701"></a>Remote CIFS Authentication Using <tt class="filename">winbindd.so</tt></h3></div></div><div></div></div><p>
 384 All operating systems depend on the provision of users credentials acceptable to the platform.
 385 UNIX requires the provision of a user identifier (UID) as well as a group identifier (GID).
 386 These are both simple integer type numbers that are obtained from a password backend such
 387 as <tt class="filename">/etc/passwd</tt>.
 388 </p><p>
 389 Users and groups on a Windows NT server are assigned a relative ID (RID) which is unique for
 390 the domain when the user or group is created. To convert the Windows NT user or group into
 391 a  UNIX user or group, a mapping between RIDs and UNIX user and group IDs is required. This
 392 is one of the jobs that winbind performs.
 393 </p><p>
 394 As Winbind users and groups are resolved from a server, user and group IDs are allocated
 395 from a specified range. This is done on a first come, first served basis, although all
 396 existing users and groups will be mapped as soon as a client performs a user or  group
 397 enumeration command. The allocated UNIX IDs are stored in a database file under the Samba
 398 lock directory and will be remembered.
 399 </p><p>
 400 The astute administrator will realize from this that the combination of <tt class="filename">pam_smbpass.so</tt>,
 401 <b class="command">winbindd</b> and a distributed <a class="indexterm" name="id2960770"></a><i class="parameter"><tt>passdb backend</tt></i>,
 402 such as <i class="parameter"><tt>ldap</tt></i>, will allow the establishment of a centrally managed, distributed user/password
 403 database that can also be used by all PAM-aware (e.g., Linux) programs and applications. This arrangement can have
 404 particularly potent advantages compared with the use of Microsoft Active Directory Service (ADS) in so far as
 405 the reduction of wide area network authentication traffic.
 406 </p><div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Warning</h3><p>
 407 The RID to UNIX ID database is the only location where the user and group  mappings are
 408 stored by <b class="command">winbindd</b>. If this file is deleted or corrupted, there is no way for <b class="command">winbindd</b>
 409 to determine which user and group IDs correspond to Windows NT user and group RIDs.
 410 </p></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2960824"></a>Password Synchronization Using <tt class="filename">pam_smbpass.so</tt></h3></div></div><div></div></div><p>
 411 <tt class="filename">pam_smbpass</tt> is a PAM module that can be used on conforming systems to
 412 keep the <tt class="filename">smbpasswd</tt> (Samba password) database in sync with the UNIX
 413 password file. PAM (Pluggable Authentication Modules) is an API supported
 414 under some UNIX operating systems, such as Solaris, HPUX and Linux, that provides a
 415 generic interface to authentication mechanisms.
 416 </p><p>
 417 This module authenticates a local <tt class="filename">smbpasswd</tt> user database. If you require
 418 support for authenticating against a remote SMB server, or if you are
 419 concerned about the presence of SUID root binaries on your system, it is
 420 recommended that you use <tt class="filename">pam_winbind</tt> instead.
 421 </p><p>
 422 Options recognized by this module are shown in <link linkend="smbpassoptions">.
 423 </p><div class="table"><a name="smbpassoptions"></a><p class="title"><b>Table 25.1. Options recognized by <i class="parameter"><tt>pam_smbpass</tt></i></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="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">do 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 &#8220;<span class="quote">auth</span>&#8221; context; used to update smbpasswd file with a password used for successful authentication.</td></tr><tr><td align="left">smbconf=<i class="replaceable"><tt>file</tt></i></td><td align="justify">specify an alternate path to the <tt class="filename">smb.conf</tt> file.</td></tr></tbody></table></div><p>
 424 </p><p>
 425 The following are examples of the use of <tt class="filename">pam_smbpass.so</tt> in the format of Linux
 426 <tt class="filename">/etc/pam.d/</tt> files structure. Those wishing to implement this
 427 tool on other platforms will need to adapt this appropriately.
 428 </p><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2961083"></a>Password Synchronization Configuration</h4></div></div><div></div></div><p>
 429 A sample PAM configuration that shows the use of pam_smbpass to make
 430 sure <tt class="filename">private/smbpasswd</tt> is kept in sync when <tt class="filename">/etc/passwd (/etc/shadow)</tt>
 431 is changed. Useful when an expired password might be changed by an
 432 application (such as <b class="command">ssh</b>).
 433 </p><pre class="programlisting">
 434 #%PAM-1.0
 435 # password-sync
 436 #
 437 auth       requisite    pam_nologin.so
 438 auth       required     pam_UNIX.so
 439 account    required     pam_UNIX.so
 440 password   requisite    pam_cracklib.so retry=3
 441 password   requisite    pam_UNIX.so shadow md5 use_authtok try_first_pass
 442 password   required     pam_smbpass.so nullok use_authtok try_first_pass
 443 session    required     pam_UNIX.so
 444 </pre></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2961136"></a>Password Migration Configuration</h4></div></div><div></div></div><p>
 445 A sample PAM configuration that shows the use of <tt class="filename">pam_smbpass</tt> to migrate
 446 from plaintext to encrypted passwords for Samba. Unlike other methods,
 447 this can be used for users who have never connected to Samba shares:
 448 password migration takes place when users <b class="command">ftp</b> in, login using <b class="command">ssh</b>, pop
 449 their mail, and so on.
 450 </p><pre class="programlisting">
 451 #%PAM-1.0
 452 # password-migration
 453 #
 454 auth       requisite   pam_nologin.so
 455 # pam_smbpass is called IF pam_UNIX succeeds.
 456 auth       requisite   pam_UNIX.so
 457 auth       optional    pam_smbpass.so migrate
 458 account    required    pam_UNIX.so
 459 password   requisite   pam_cracklib.so retry=3
 460 password   requisite   pam_UNIX.so shadow md5 use_authtok try_first_pass
 461 password   optional    pam_smbpass.so nullok use_authtok try_first_pass
 462 session    required    pam_UNIX.so
 463 </pre></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2961191"></a>Mature Password Configuration</h4></div></div><div></div></div><p>
 464 A sample PAM configuration for a mature <tt class="filename">smbpasswd</tt> installation.
 465 <tt class="filename">private/smbpasswd</tt> is fully populated, and we consider it an error if
 466 the SMB password does not exist or does not match the UNIX password.
 467 </p><pre class="programlisting">
 468 #%PAM-1.0
 469 # password-mature
 470 #
 471 auth       requisite    pam_nologin.so
 472 auth       required     pam_UNIX.so
 473 account    required     pam_UNIX.so
 474 password   requisite    pam_cracklib.so retry=3
 475 password   requisite    pam_UNIX.so shadow md5 use_authtok try_first_pass
 476 password   required     pam_smbpass.so use_authtok use_first_pass
 477 session    required     pam_UNIX.so
 478 </pre></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2961236"></a>Kerberos Password Integration Configuration</h4></div></div><div></div></div><p>
 479 A sample PAM configuration that shows <i class="parameter"><tt>pam_smbpass</tt></i> used together with
 480 <i class="parameter"><tt>pam_krb5</tt></i>. This could be useful on a Samba PDC that is also a member of
 481 a Kerberos realm.
 482 </p><pre class="programlisting">
 483 #%PAM-1.0
 484 # kdc-pdc
 485 #
 486 auth       requisite   pam_nologin.so
 487 auth       requisite   pam_krb5.so
 488 auth       optional    pam_smbpass.so migrate
 489 account    required    pam_krb5.so
 490 password   requisite   pam_cracklib.so retry=3
 491 password   optional    pam_smbpass.so nullok use_authtok try_first_pass
 492 password   required    pam_krb5.so use_authtok try_first_pass
 493 session    required    pam_krb5.so
 494 </pre></div></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2961283"></a>Common Errors</h2></div></div><div></div></div><p>
 495 PAM can be fickle and sensitive to configuration glitches. Here we look at a few cases from
 496 the Samba mailing list.
 497 </p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2961296"></a>pam_winbind Problem</h3></div></div><div></div></div><p>
 498         A user reported: I have the following PAM configuration:
 499         </p><p>
 500 </p><pre class="programlisting">
 501 auth required /lib/security/pam_securetty.so
 502 auth sufficient /lib/security/pam_winbind.so
 503 auth sufficient /lib/security/pam_UNIX.so use_first_pass nullok
 504 auth required /lib/security/pam_stack.so service=system-auth
 505 auth required /lib/security/pam_nologin.so
 506 account required /lib/security/pam_stack.so service=system-auth
 507 account required /lib/security/pam_winbind.so
 508 password required /lib/security/pam_stack.so service=system-auth
 509 </pre><p>
 510 </p><p>
 511         When I open a new console with [ctrl][alt][F1], I can't log in with my user &#8220;<span class="quote">pitie</span>&#8221;.
 512         I have tried with user &#8220;<span class="quote">scienceu+pitie</span>&#8221; also.
 513         </p><p>
 514         <span class="emphasis"><em>Answer:</em></span> The problem may lie with your inclusion of <i class="parameter"><tt>pam_stack.so
 515         service=system-auth</tt></i>. That file often contains a lot of stuff that may
 516         duplicate what you are already doing. Try commenting out the <i class="parameter"><tt>pam_stack</tt></i> lines
 517         for <i class="parameter"><tt>auth</tt></i> and <i class="parameter"><tt>account</tt></i> and see if things work. If they do, look at
 518         <tt class="filename">/etc/pam.d/system-auth</tt> and copy only what you need from it into your
 519         <tt class="filename">/etc/pam.d/login</tt> file. Alternately, if you want all services to use
 520         Winbind, you can put the Winbind-specific stuff in <tt class="filename">/etc/pam.d/system-auth</tt>.
 521         </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2961406"></a>Winbind Is Not Resolving Users and Groups</h3></div></div><div></div></div><p>
 522         &#8220;<span class="quote">
 523         My <tt class="filename">smb.conf</tt> file is correctly configured. I have specified
 524         <a class="indexterm" name="id2961428"></a><i class="parameter"><tt>idmap uid</tt></i> = 12000,
 525         and <a class="indexterm" name="id2961442"></a><i class="parameter"><tt>idmap gid</tt></i> = 3000-3500
 526         and <b class="command">winbind</b> is running. When I do the following it all works fine.
 527         </span>&#8221;
 528         </p><pre class="screen">
 529 <tt class="prompt">root# </tt><b class="userinput"><tt>wbinfo -u</tt></b>
 530 MIDEARTH+maryo
 531 MIDEARTH+jackb
 532 MIDEARTH+ameds
 533 ...
 534 MIDEARTH+root
 535
 536 <tt class="prompt">root# </tt><b class="userinput"><tt>wbinfo -g</tt></b>
 537 MIDEARTH+Domain Users
 538 MIDEARTH+Domain Admins
 539 MIDEARTH+Domain Guests
 540 ...
 541 MIDEARTH+Accounts
 542
 543 <tt class="prompt">root# </tt><b class="userinput"><tt>getent passwd</tt></b>
 544 root:x:0:0:root:/root:/bin/bash
 545 bin:x:1:1:bin:/bin:/bin/bash
 546 ...
 547 maryo:x:15000:15003:Mary Orville:/home/MIDEARTH/maryo:/bin/false
 548 </pre><p>
 549         &#8220;<span class="quote">
 550         But this command fails:
 551         </span>&#8221;
 552 </p><pre class="screen">
 553 <tt class="prompt">root# </tt><b class="userinput"><tt>chown maryo a_file</tt></b>
 554 chown: 'maryo': invalid user
 555 </pre><p>
 556         &#8220;<span class="quote">This is driving me nuts! What can be wrong?</span>&#8221;
 557         </p><p>
 558         <span class="emphasis"><em>Answer:</em></span> Your system is likely running <b class="command">nscd</b>, the name service
 559         caching daemon. Shut it down, do not restart it! You will find your problem resolved.
 560         </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 24. 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 26. Integrating MS Windows Networks with Samba</td></tr></table></div></body></html>