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<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter28.PAM-Based Distributed Authentication</title><link rel="stylesheet" href="../samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.73.1"><link rel="start" href="index.html" title="The Official Samba 3.2.x HOWTO and Reference Guide"><link rel="up" href="optional.html" title="PartIII.Advanced Configuration"><link rel="prev" href="ProfileMgmt.html" title="Chapter27.Desktop Profile Management"><link rel="next" href="integrate-ms-networks.html" title="Chapter29.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">Chapter28.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">PartIII.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>Chapter28.PAM-Based Distributed Authentication</h2></div><div><div class="author"><h3 class="author"><span class="firstname">John</span> <span class="othername">H.</span> <span class="surname">Terpstra</span></h3><div class="affiliation"><span class="orgname">Samba Team<br></span><div class="address"><p><code class="email">&lt;<a class="email" href="mailto:jht@samba.org">jht@samba.org</a>&gt;</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">&lt;<a class="email" href="mailto:vorlon@netexpress.net">vorlon@netexpress.net</a>&gt;</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#id2658156">Features and Benefits</a></span></dt><dt><span class="sect1"><a href="pam.html#id2658787">Technical Discussion</a></span></dt><dd><dl><dt><span class="sect2"><a href="pam.html#id2658841">PAM Configuration Syntax</a></span></dt><dt><span class="sect2"><a href="pam.html#id2659838">Example System Configurations</a></span></dt><dt><span class="sect2"><a href="pam.html#id2660145"><code class="filename">smb.conf</code> PAM Configuration</a></span></dt><dt><span class="sect2"><a href="pam.html#id2660225">Remote CIFS Authentication Using <code class="filename">winbindd.so</code></a></span></dt><dt><span class="sect2"><a href="pam.html#id2660328">Password Synchronization Using <code class="filename">pam_smbpass.so</code></a></span></dt></dl></dd><dt><span class="sect1"><a href="pam.html#id2660722">Common Errors</a></span></dt><dd><dl><dt><span class="sect2"><a href="pam.html#id2660733">pam_winbind Problem</a></span></dt><dt><span class="sect2"><a href="pam.html#id2660831">Winbind Is Not Resolving Users and Groups</a></span></dt></dl></dd></dl></div><p>
<a class="indexterm" name="id2658081"></a>
<a class="indexterm" name="id2658088"></a>
<a class="indexterm" name="id2658094"></a>
<a class="indexterm" name="id2658101"></a>
This chapter should help you to deploy Winbind-based authentication on any PAM-enabled
UNIX/Linux system. Winbind can be used to enable user-level application access authentication
from any MS Windows NT domain, MS Windows 200x Active Directory-based
domain, or any Samba-based domain environment. It will also help you to configure PAM-based local host access
controls that are appropriate to your Samba configuration.
</p><p>
<a class="indexterm" name="id2658118"></a>
<a class="indexterm" name="id2658125"></a>
In addition to knowing how to configure Winbind into PAM, you will learn generic PAM management
possibilities and in particular how to deploy tools like <code class="filename">pam_smbpass.so</code> to your advantage.
</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
The use of Winbind requires more than PAM configuration alone.
Please refer to <a class="link" href="winbind.html" title="Chapter24.Winbind: Use of Domain Accounts">Winbind: Use of Domain Accounts</a>, for further information regarding Winbind.
</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2658156"></a>Features and Benefits</h2></div></div></div><p>
<a class="indexterm" name="id2658164"></a>
<a class="indexterm" name="id2658171"></a>
<a class="indexterm" name="id2658178"></a>
<a class="indexterm" name="id2658185"></a>
<a class="indexterm" name="id2658194"></a>
<a class="indexterm" name="id2658201"></a>
<a class="indexterm" name="id2658208"></a>
<a class="indexterm" name="id2658214"></a>
A number of UNIX systems (e.g., Sun Solaris), as well as the xxxxBSD family and Linux,
now utilize the Pluggable Authentication Modules (PAM) facility to provide all authentication, 
authorization, and resource control services. Prior to the introduction of PAM, a decision
to use an alternative to the system password database (<code class="filename">/etc/passwd</code>) 
would require the provision of alternatives for all programs that provide security services.
Such a choice would involve provision of alternatives to programs such as <code class="literal">login</code>, 
<code class="literal">passwd</code>, <code class="literal">chown</code>, and so on.
</p><p>
<a class="indexterm" name="id2658256"></a>
<a class="indexterm" name="id2658263"></a>
<a class="indexterm" name="id2658270"></a>
<a class="indexterm" name="id2658276"></a>
PAM provides a mechanism that disconnects these security programs from the underlying
authentication/authorization infrastructure. PAM is configured by making appropriate modifications to one file,
<code class="filename">/etc/pam.conf</code> (Solaris), or by editing individual control files that are
located in <code class="filename">/etc/pam.d</code>.
</p><p>
<a class="indexterm" name="id2658303"></a>
<a class="indexterm" name="id2658310"></a>
On PAM-enabled UNIX/Linux systems, it is an easy matter to configure the system to use any
authentication backend so long as the appropriate dynamically loadable library modules
are available for it. The backend may be local to the system or may be centralized on a
remote server.
</p><p>
PAM support modules are available for:
</p><div class="variablelist"><dl><dt><span class="term"><code class="filename">/etc/passwd</code></span></dt><dd><p>
<a class="indexterm" name="id2658340"></a>
<a class="indexterm" name="id2658347"></a>
<a class="indexterm" name="id2658354"></a>
<a class="indexterm" name="id2658360"></a>
<a class="indexterm" name="id2658367"></a>
<a class="indexterm" name="id2658374"></a>
		There are several PAM modules that interact with this standard UNIX user database. The most common are called
		<code class="filename">pam_unix.so</code>, <code class="filename">pam_unix2.so</code>, <code class="filename">pam_pwdb.so</code> and
		<code class="filename">pam_userdb.so</code>.
		</p></dd><dt><span class="term">Kerberos</span></dt><dd><p>
<a class="indexterm" name="id2658417"></a>
<a class="indexterm" name="id2658424"></a>
<a class="indexterm" name="id2658430"></a>
<a class="indexterm" name="id2658437"></a>
<a class="indexterm" name="id2658444"></a>
		The <code class="filename">pam_krb5.so</code> module allows the use of any Kerberos-compliant server.
		This tool is used to access MIT Kerberos, Heimdal Kerberos, and potentially
		Microsoft Active Directory (if enabled).
		</p></dd><dt><span class="term">LDAP</span></dt><dd><p>
<a class="indexterm" name="id2658470"></a>
<a class="indexterm" name="id2658476"></a>
<a class="indexterm" name="id2658483"></a>
<a class="indexterm" name="id2658490"></a>
<a class="indexterm" name="id2658497"></a>
<a class="indexterm" name="id2658504"></a>
		The <code class="filename">pam_ldap.so</code> module allows the use of any LDAP v2- or v3-compatible backend
		server. Commonly used LDAP backend servers include OpenLDAP v2.0 and v2.1,
		Sun ONE iDentity server, Novell eDirectory server, and Microsoft Active Directory.
		</p></dd><dt><span class="term">NetWare Bindery</span></dt><dd><p>
<a class="indexterm" name="id2658531"></a>
<a class="indexterm" name="id2658538"></a>
<a class="indexterm" name="id2658545"></a>
<a class="indexterm" name="id2658552"></a>
		The <code class="filename">pam_ncp_auth.so</code> module allows authentication off any bindery-enabled
		NetWare Core Protocol-based server.
		</p></dd><dt><span class="term">SMB Password</span></dt><dd><p>
<a class="indexterm" name="id2658577"></a>
<a class="indexterm" name="id2658584"></a>
<a class="indexterm" name="id2658591"></a>
		This module, called <code class="filename">pam_smbpass.so</code>, allows user authentication of
		the passdb backend that is configured in the Samba <code class="filename">smb.conf</code> file.
		</p></dd><dt><span class="term">SMB Server</span></dt><dd><p>
<a class="indexterm" name="id2658622"></a>
<a class="indexterm" name="id2658629"></a>
		The <code class="filename">pam_smb_auth.so</code> module is the original MS Windows networking authentication
		tool. This module has been somewhat outdated by the Winbind module.
		</p></dd><dt><span class="term">Winbind</span></dt><dd><p>
<a class="indexterm" name="id2658654"></a>
<a class="indexterm" name="id2658661"></a>
<a class="indexterm" name="id2658668"></a>
<a class="indexterm" name="id2658675"></a>
		The <code class="filename">pam_winbind.so</code> module allows Samba to obtain authentication from any
		MS Windows domain controller. It can just as easily be used to authenticate
		users for access to any PAM-enabled application.
		</p></dd><dt><span class="term">RADIUS</span></dt><dd><p>
<a class="indexterm" name="id2658701"></a>
		There is a PAM RADIUS (Remote Access Dial-In User Service) authentication
		module. In most cases, administrators need to locate the source code
		for this tool and compile and install it themselves. RADIUS protocols are
		used by many routers and terminal servers.
		</p></dd></dl></div><p>
<a class="indexterm" name="id2658720"></a>
<a class="indexterm" name="id2658727"></a>
Of the modules listed, Samba provides the <code class="filename">pam_smbpasswd.so</code> and the
<code class="filename">pam_winbind.so</code> modules alone.
</p><p>
<a class="indexterm" name="id2658751"></a>
<a class="indexterm" name="id2658758"></a>
<a class="indexterm" name="id2658765"></a>
<a class="indexterm" name="id2658772"></a>
Once configured, these permit a remarkable level of flexibility in the location and use
of distributed Samba domain controllers that can provide wide-area network bandwidth,
efficient authentication services for PAM-capable systems. In effect, this allows the
deployment of centrally managed and maintained distributed authentication from a
single-user account database.
</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2658787"></a>Technical Discussion</h2></div></div></div><p>
<a class="indexterm" name="id2658795"></a>
<a class="indexterm" name="id2658802"></a>
<a class="indexterm" name="id2658809"></a>
<a class="indexterm" name="id2658816"></a>
PAM is designed to provide system administrators with a great deal of flexibility in
configuration of the privilege-granting applications of their system. The local
configuration of system security controlled by PAM is contained in one of two places:
either the single system file <code class="filename">/etc/pam.conf</code> or the
<code class="filename">/etc/pam.d/</code> directory.
</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2658841"></a>PAM Configuration Syntax</h3></div></div></div><p>
<a class="indexterm" name="id2658849"></a>
<a class="indexterm" name="id2658856"></a>
In this section we discuss the correct syntax of and generic options respected by entries to these files.
PAM-specific tokens in the configuration file are case insensitive. The module paths, however, are case
sensitive, since they indicate a file's name and reflect the case dependence of typical file systems.  The
case sensitivity of the arguments to any given module is defined for each module in turn.
</p><p>
In addition to the lines described below, there are two special characters provided for the convenience
of the system administrator: comments are preceded by a &#8220;<span class="quote">#</span>&#8221; and extend to the next end-of-line; also,
module specification lines may be extended with a &#8220;<span class="quote">\</span>&#8221;-escaped newline. 
</p><p>
<a class="indexterm" name="id2658887"></a>
<a class="indexterm" name="id2658894"></a>
If the PAM authentication module (loadable link library file) is located in the
default location, then it is not necessary to specify the path. In the case of
Linux, the default location is <code class="filename">/lib/security</code>. If the module
is located outside the default, then the path must be specified as:
</p><pre class="programlisting">
auth  required  /other_path/pam_strange_module.so
</pre><p>
</p><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2658920"></a>Anatomy of <code class="filename">/etc/pam.d</code> Entries</h4></div></div></div><p>
The remaining information in this subsection was taken from the documentation of the Linux-PAM
project. For more information on PAM, see 
<a class="ulink" href="http://ftp.kernel.org/pub/linux/libs/pam/" target="_top">the Official Linux-PAM home page</a>.
</p><p>
<a class="indexterm" name="id2658946"></a>
A general configuration line of the <code class="filename">/etc/pam.conf</code> file has the following form:
</p><pre class="programlisting">
service-name   module-type   control-flag   module-path   args
</pre><p>
</p><p>
We explain the meaning of each of these tokens. The second (and more recently adopted)
way of configuring Linux-PAM is via the contents of the <code class="filename">/etc/pam.d/</code> directory.
Once we have explained the meaning of the tokens, we describe this method.
</p><div class="variablelist"><dl><dt><span class="term">service-name</span></dt><dd><p>
<a class="indexterm" name="id2658991"></a>
<a class="indexterm" name="id2658998"></a>
<a class="indexterm" name="id2659004"></a>
		The name of the service associated with this entry. Frequently, the service-name is the conventional
		name of the given application  for example, <code class="literal">ftpd</code>, <code class="literal">rlogind</code> and
		<code class="literal">su</code>, and so on.
		</p><p>
		There is a special service-name reserved for defining a default authentication mechanism. It has
		the name <em class="parameter"><code>OTHER</code></em> and may be specified in either lower- or uppercase characters.
		Note, when there is a module specified for a named service, the <em class="parameter"><code>OTHER</code></em>
		entries are ignored.
		</p></dd><dt><span class="term">module-type</span></dt><dd><p>
		One of (currently) four types of module. The four types are as follows:
		</p><div class="itemizedlist"><ul type="disc"><li><p>
<a class="indexterm" name="id2659072"></a>
<a class="indexterm" name="id2659079"></a>
			<em class="parameter"><code>auth:</code></em> This module type provides two aspects of authenticating the user.
			It establishes that the user is who he or she claims to be by instructing the application
			to prompt the user for a password or other means of identification. Second, the module can
			grant group membership (independently of the <code class="filename">/etc/groups</code> file)
			or other privileges through its credential-granting properties.
			</p></li><li><p>
<a class="indexterm" name="id2659108"></a>
<a class="indexterm" name="id2659115"></a>
			<em class="parameter"><code>account:</code></em> This module performs non-authentication-based account management.
			It is typically used to restrict/permit access to a service based on the time of day, currently
		 	available system resources (maximum number of users), or perhaps the location of the user 
			login. For example, the &#8220;<span class="quote">root</span>&#8221; login may be permitted only on the console.
			</p></li><li><p>
<a class="indexterm" name="id2659142"></a>
			<em class="parameter"><code>session:</code></em> Primarily, this module is associated with doing things that need
			to be done for the user before and after he or she can be given service. Such things include logging
			information concerning the opening and closing of some data exchange with a user, mounting
			directories, and so on.
			</p></li><li><p>
<a class="indexterm" name="id2659164"></a>
			<em class="parameter"><code>password:</code></em> This last module type is required for updating the authentication
			token associated with the user. Typically, there is one module for each
			&#8220;<span class="quote">challenge/response</span>&#8221; authentication <em class="parameter"><code>(auth)</code></em> module type.
			</p></li></ul></div></dd><dt><span class="term">control-flag</span></dt><dd><p>
		The control-flag is used to indicate how the PAM library will react to the success or failure of the
		module it is associated with. Since modules can be stacked (modules of the same type execute in series,
		one after another), the control-flags determine the relative importance of each module. The application
		is not made aware of the individual success or failure of modules listed in the
		<code class="filename">/etc/pam.conf</code> file. Instead, it receives a summary success or fail response from
		the Linux-PAM library. The order of execution of these modules is that of the entries in the
		<code class="filename">/etc/pam.conf</code> file; earlier entries are executed before later ones.
		As of Linux-PAM v0.60, this control-flag can be defined with one of two syntaxes.
		</p><p>
<a class="indexterm" name="id2659228"></a>
<a class="indexterm" name="id2659235"></a>
<a class="indexterm" name="id2659242"></a>
<a class="indexterm" name="id2659249"></a>
		The simpler (and historical) syntax for the control-flag is a single keyword defined to indicate the
		severity of concern associated with the success or failure of a specific module. There are four such
		keywords: <em class="parameter"><code>required</code></em>, <em class="parameter"><code>requisite</code></em>,
		<em class="parameter"><code>sufficient</code></em>, and <em class="parameter"><code>optional</code></em>.
		</p><p>
		The Linux-PAM library interprets these keywords in the following manner:
		</p><div class="itemizedlist"><ul type="disc"><li><p>
			<em class="parameter"><code>required:</code></em> This indicates that the success of the module is required for the
			module-type facility to succeed. Failure of this module will not be apparent to the user until all
			of the remaining modules (of the same module-type) have been executed.
			</p></li><li><p>
			<em class="parameter"><code>requisite:</code></em> Like required, except that if such a module returns a
			failure, control is directly returned to the application. The return value is that associated with
			the first required or requisite module to fail. This flag can be used to protect against the
			possibility of a user getting the opportunity to enter a password over an unsafe medium. It is
			conceivable that such behavior might inform an attacker of valid accounts on a system. This
			possibility should be weighed against the not insignificant concerns of exposing a sensitive
			password in a hostile environment.
			</p></li><li><p>
			<em class="parameter"><code>sufficient:</code></em> The success of this module is deemed <em class="parameter"><code>sufficient</code></em> to satisfy
			the Linux-PAM library that this module-type has succeeded in its purpose. In the event that no
			previous required module has failed, no more &#8220;<span class="quote">stacked</span>&#8221; modules of this type are invoked.
			(In this case, subsequent required modules are not invoked). A failure of this module is not deemed
			as fatal to satisfying the application that this module-type has succeeded.
			</p></li><li><p>
            <em class="parameter"><code>optional:</code></em> As its name suggests, this control-flag marks the module as not
			being critical to the success or failure of the user's application for service. In general,
			Linux-PAM ignores such a module when determining if the module stack will succeed or fail.
			However, in the absence of any definite successes or failures of previous or subsequent stacked
			modules, this module will determine the nature of the response to the application. One example of
			this latter case is when the other modules return something like PAM_IGNORE.
			</p></li></ul></div><p>
		The more elaborate (newer) syntax is much more specific and gives the administrator a great deal of control
		over how the user is authenticated. This form of the control-flag is delimited with square brackets and
		consists of a series of <em class="parameter"><code>value=action</code></em> tokens:
		</p><pre class="programlisting">
[value1=action1 value2=action2 ...]
</pre><p>
		Here, <em class="parameter"><code>value1</code></em> is one of the following return values:
</p><pre class="screen">
<em class="parameter"><code>success; open_err; symbol_err; service_err; system_err; buf_err;</code></em>
<em class="parameter"><code>perm_denied; auth_err; cred_insufficient; authinfo_unavail;</code></em>
<em class="parameter"><code>user_unknown; maxtries; new_authtok_reqd; acct_expired; session_err;</code></em>
<em class="parameter"><code>cred_unavail; cred_expired; cred_err; no_module_data; conv_err;</code></em>
<em class="parameter"><code>authtok_err; authtok_recover_err; authtok_lock_busy;</code></em>
<em class="parameter"><code>authtok_disable_aging; try_again; ignore; abort; authtok_expired;</code></em>
<em class="parameter"><code>module_unknown; bad_item;</code></em> and <em class="parameter"><code>default</code></em>.
</pre><p>
</p><p>
		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.
		</p><p>
		The <em class="parameter"><code>action1</code></em> can be a positive integer or one of the following tokens: 
		<em class="parameter"><code>ignore</code></em>; <em class="parameter"><code>ok</code></em>; <em class="parameter"><code>done</code></em>;
		<em class="parameter"><code>bad</code></em>; <em class="parameter"><code>die</code></em>; and <em class="parameter"><code>reset</code></em>.
		A positive integer, J, when specified as the action, can be used to indicate that the next J modules of the
		current module-type will be skipped. In this way, the administrator can develop a moderately sophisticated
		stack of modules with a number of different paths of execution. Which path is taken can be determined by the
		reactions of individual modules.
		</p><div class="itemizedlist"><ul type="disc"><li><p>
			<em class="parameter"><code>ignore:</code></em> When used with a stack of modules, the module's return status will not
			contribute to the return code the application obtains.
			</p></li><li><p>
            <em class="parameter"><code>bad:</code></em> This action indicates that the return code should be thought of as indicative
			of the module failing. If this module is the first in the stack to fail, its status value will be used
			for that of the whole stack.
			</p></li><li><p>
            <em class="parameter"><code>die:</code></em> Equivalent to bad with the side effect of terminating the module stack and
			PAM immediately returning to the application.
			</p></li><li><p>
           <em class="parameter"><code>ok:</code></em> This tells PAM that the administrator thinks this return code should
			contribute directly to the return code of the full stack of modules. In other words, if the former
			state of the stack would lead to a return of PAM_SUCCESS, the module's return code will override
			this value. Note, if the former state of the stack holds some value that is indicative of a module's
			failure, this <em class="parameter"><code>ok</code></em> value will not be used to override that value.
			</p></li><li><p>
            <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
			PAM immediately returning to the application.
                        </p></li><li><p>
           <em class="parameter"><code>reset:</code></em> Clears all memory of the state of the module stack and starts again with
			the next stacked module.
			</p></li></ul></div><p>
		Each of the four keywords, <em class="parameter"><code>required</code></em>; <em class="parameter"><code>requisite</code></em>;
		<em class="parameter"><code>sufficient</code></em>; and <em class="parameter"><code>optional</code></em>, have an equivalent expression in terms
		of the [...] syntax. They are as follows:
		</p><p>
		</p><div class="itemizedlist"><ul type="disc"><li><p>
			<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>.
			</p></li><li><p>
			<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>.
			</p></li><li><p>
			<em class="parameter"><code>sufficient</code></em> is equivalent to <em class="parameter"><code>[success=done  new_authtok_reqd=done  default=ignore]</code></em>.
			</p></li><li><p>
			<em class="parameter"><code>optional</code></em> is equivalent to <em class="parameter"><code>[success=ok new_authtok_reqd=ok default=ignore]</code></em>.
			</p></li></ul></div><p>
		</p><p>
		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,
		the notion of client plug-in agents was introduced. This makes it possible for PAM to support
		machine-machine authentication using the transport protocol inherent to the client/server application. With the
		<em class="parameter"><code>[ ... value=action ... ]</code></em> control syntax, it is possible for an application to be configured
		to support binary prompts with compliant clients, but to gracefully fail over into an alternative authentication
		mode for legacy applications.
		</p></dd><dt><span class="term">module-path</span></dt><dd><p>
		The pathname of the dynamically loadable object file; the pluggable module itself. If the first character of the
		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
		to the default module path: <code class="filename">/lib/security</code> (but see the previous notes).
		</p><p>
		The arguments are a list of tokens that are passed to the module when it is invoked, much like arguments to a typical
		Linux shell command. Generally, valid arguments are optional and are specific to any given module. Invalid arguments
		are ignored by a module; however, when encountering an invalid argument, the module is required to write an error
		to syslog(3). For a list of generic options, see the next section.
		</p><p>
		If you wish to include spaces in an argument, you should surround that argument with square brackets. For example:
		</p><pre class="programlisting">
squid auth required pam_mysql.so user=passwd_query passwd=mada \
db=eminence [query=select user_name from internet_service where \
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;]
</pre><p>
		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;
		character inside the string that will survive the argument parsing, you should use &#8220;<span class="quote">\[</span>&#8221;. In other words,
		</p><pre class="programlisting">
[..[..\]..]    --&gt;   ..[..]..
</pre><p>
		Any line in one of the configuration files that is not formatted correctly will generally tend (erring on the
		side of caution) to make the authentication process fail. A corresponding error is written to the system log files
		with a call to syslog(3). 
		</p></dd></dl></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2659838"></a>Example System Configurations</h3></div></div></div><p>
The following is an example <code class="filename">/etc/pam.d/login</code> configuration file. 
This example had all options uncommented and is probably not usable 
because it stacks many conditions before allowing successful completion 
of the login process. Essentially, all conditions can be disabled 
by commenting them out, except the calls to <code class="filename">pam_pwdb.so</code>.
</p><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2659865"></a>PAM: Original Login Config</h4></div></div></div><p>
	</p><pre class="programlisting">
#%PAM-1.0
# The PAM configuration file for the &#8220;<span class="quote">login</span>&#8221; service
#
auth         required    pam_securetty.so
auth         required    pam_nologin.so
# auth       required    pam_dialup.so
# auth       optional    pam_mail.so
auth         required    pam_pwdb.so shadow md5
# account    requisite   pam_time.so
account      required    pam_pwdb.so
session      required    pam_pwdb.so
# session    optional    pam_lastlog.so
# password   required    pam_cracklib.so retry=3
password     required    pam_pwdb.so shadow md5
</pre><p>
</p></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2659893"></a>PAM: Login Using <code class="filename">pam_smbpass</code></h4></div></div></div><p>
PAM allows use of replaceable modules. Those available on a sample system include:
</p><p><code class="prompt">$</code><strong class="userinput"><code>/bin/ls /lib/security</code></strong>
</p><pre class="programlisting">
pam_access.so    pam_ftp.so          pam_limits.so     
pam_ncp_auth.so  pam_rhosts_auth.so  pam_stress.so     
pam_cracklib.so  pam_group.so        pam_listfile.so   
pam_nologin.so   pam_rootok.so       pam_tally.so      
pam_deny.so      pam_issue.so        pam_mail.so       
pam_permit.so    pam_securetty.so    pam_time.so       
pam_dialup.so    pam_lastlog.so      pam_mkhomedir.so  
pam_pwdb.so      pam_shells.so       pam_unix.so       
pam_env.so       pam_ldap.so         pam_motd.so       
pam_radius.so    pam_smbpass.so      pam_unix_acct.so  
pam_wheel.so     pam_unix_auth.so    pam_unix_passwd.so
pam_userdb.so    pam_warn.so         pam_unix_session.so
</pre><p>
The following example for the login program replaces the use of 
the <code class="filename">pam_pwdb.so</code> module that uses the system 
password database (<code class="filename">/etc/passwd</code>,
<code class="filename">/etc/shadow</code>, <code class="filename">/etc/group</code>) with 
the module <code class="filename">pam_smbpass.so</code>, which uses the Samba 
database containing the Microsoft MD4 encrypted password 
hashes. This database is stored either in 
<code class="filename">/usr/local/samba/private/smbpasswd</code>, 
<code class="filename">/etc/samba/smbpasswd</code> or in 
<code class="filename">/etc/samba.d/smbpasswd</code>, depending on the 
Samba implementation for your UNIX/Linux system. The 
<code class="filename">pam_smbpass.so</code> module is provided by 
Samba version 2.2.1 or later. It can be compiled by specifying the 
<code class="option">--with-pam_smbpass</code> options when running Samba's
<code class="literal">configure</code> script. For more information
on the <code class="filename">pam_smbpass</code> module, see the documentation
in the <code class="filename">source/pam_smbpass</code> directory of the Samba 
source distribution.
</p><p>
	</p><pre class="programlisting">
#%PAM-1.0
# The PAM configuration file for the &#8220;<span class="quote">login</span>&#8221; service
#
auth        required    pam_smbpass.so nodelay
account     required    pam_smbpass.so nodelay
session     required    pam_smbpass.so nodelay
password    required    pam_smbpass.so nodelay
</pre><p>
The following is the PAM configuration file for a particular 
Linux system. The default condition uses <code class="filename">pam_pwdb.so</code>.
</p><p>
	</p><pre class="programlisting">
#%PAM-1.0
# The PAM configuration file for the &#8220;<span class="quote">samba</span>&#8221; service
#
auth       required     pam_pwdb.so nullok nodelay shadow audit
account    required     pam_pwdb.so audit nodelay
session    required     pam_pwdb.so nodelay
password   required     pam_pwdb.so shadow md5
</pre><p>
In the following example, the decision has been made to use the 
<code class="literal">smbpasswd</code> database even for basic Samba authentication. Such a 
decision could also be made for the <code class="literal">passwd</code> program and would 
thus allow the <code class="literal">smbpasswd</code> passwords to be changed using the
<code class="literal">passwd</code> program:
</p><p>
		</p><pre class="programlisting">
#%PAM-1.0
# The PAM configuration file for the &#8220;<span class="quote">samba</span>&#8221; service
#
auth       required     pam_smbpass.so nodelay
account    required     pam_pwdb.so audit nodelay
session    required     pam_pwdb.so nodelay
password   required     pam_smbpass.so nodelay smbconf=/etc/samba.d/smb.conf
</pre><p>
</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 
also possible to pass information obtained within one PAM module through 
to the next module in the PAM stack. Please refer to the documentation for 
your particular system implementation for details regarding the specific 
capabilities of PAM in this environment. Some Linux implementations also 
provide the <code class="filename">pam_stack.so</code> module that allows all 
authentication to be configured in a single central file. The 
<code class="filename">pam_stack.so</code> method has some devoted followers 
on the basis that it allows for easier administration. As with all issues in 
life, though, every decision has trade-offs, so you may want to examine the 
PAM documentation for further helpful information.
</p></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2660145"></a><code class="filename">smb.conf</code> PAM Configuration</h3></div></div></div><p>
There is an option in <code class="filename">smb.conf</code> called <a class="link" href="smb.conf.5.html#OBEYPAMRESTRICTIONS">obey pam restrictions</a>.
The following is from the online help for this option in SWAT:
</p><div class="blockquote"><blockquote class="blockquote"><p>
When Samba is configured to enable PAM support (i.e., <code class="option">--with-pam</code>), this parameter will 
control whether or not Samba should obey PAM's account and session management directives. The default behavior 
is to use PAM for clear-text authentication only and to ignore any account or session management. Samba always 
ignores PAM for authentication in the case of <a class="link" href="smb.conf.5.html#ENCRYPTPASSWORDS">encrypt passwords = yes</a>. 
The reason is that PAM modules cannot support the challenge/response authentication mechanism needed in the presence of SMB 
password encryption. 
</p><p>Default: <a class="link" href="smb.conf.5.html#OBEYPAMRESTRICTIONS">obey pam restrictions = no</a></p></blockquote></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2660225"></a>Remote CIFS Authentication Using <code class="filename">winbindd.so</code></h3></div></div></div><p>
All operating systems depend on the provision of user credentials acceptable to the platform.
UNIX requires the provision of a user identifier (UID) as well as a group identifier (GID).
These are both simple integer numbers that are obtained from a password backend such
as <code class="filename">/etc/passwd</code>.
</p><p>
Users and groups on a Windows NT server are assigned a relative ID (RID) which is unique for
the domain when the user or group is created. To convert the Windows NT user or group into
a  UNIX user or group, a mapping between RIDs and UNIX user and group IDs is required. This
is one of the jobs that winbind performs.
</p><p>
As winbind users and groups are resolved from a server, user and group IDs are allocated
from a specified range. This is done on a first come, first served basis, although all
existing users and groups will be mapped as soon as a client performs a user or  group 
enumeration command. The allocated UNIX IDs are stored in a database file under the Samba
lock directory and will be remembered.
</p><p>
The astute administrator will realize from this that the combination of <code class="filename">pam_smbpass.so</code>, 
<code class="literal">winbindd</code>, and a distributed <a class="link" href="smb.conf.5.html#PASSDBBACKEND">passdb backend</a>
such as <em class="parameter"><code>ldap</code></em> will allow the establishment of a centrally managed, distributed user/password
database that can also be used by all PAM-aware (e.g., Linux) programs and applications. This arrangement can have
particularly potent advantages compared with the use of Microsoft Active Directory Service (ADS) insofar as
the reduction of wide-area network authentication traffic.
</p><div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Warning</h3><p>
The RID to UNIX ID database is the only location where the user and group  mappings are 
stored by <code class="literal">winbindd</code>. If this file is deleted or corrupted, there is no way for <code class="literal">winbindd</code>
to determine which user and group IDs correspond to Windows NT user and group RIDs.
</p></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2660328"></a>Password Synchronization Using <code class="filename">pam_smbpass.so</code></h3></div></div></div><p>
<code class="filename">pam_smbpass</code> is a PAM module that can be used on conforming systems to
keep the <code class="filename">smbpasswd</code> (Samba password) database in sync with the UNIX
password file. PAM is an API supported
under some UNIX operating systems, such as Solaris, HPUX, and Linux, that provides a
generic interface to authentication mechanisms.
</p><p>
This module authenticates a local <code class="filename">smbpasswd</code> user database. If you require
support for authenticating against a remote SMB server, or if you are
concerned about the presence of SUID root binaries on your system, it is
recommended that you use <code class="filename">pam_winbind</code> instead.
</p><p>
Options recognized by this module are shown in <a class="link" href="pam.html#smbpassoptions" title="Table28.1.Options recognized by pam_smbpass">next table</a>.
</p><div class="table"><a name="smbpassoptions"></a><p class="title"><b>Table28.1.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 &#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=<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">
</p><p>
The following are examples of the use of <code class="filename">pam_smbpass.so</code> in the format of the Linux
<code class="filename">/etc/pam.d/</code> files structure. Those wishing to implement this
tool on other platforms will need to adapt this appropriately.
</p><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2660547"></a>Password Synchronization Configuration</h4></div></div></div><p>
The following is a sample PAM configuration that shows the use of pam_smbpass to make
sure <code class="filename">private/smbpasswd</code> is kept in sync when <code class="filename">/etc/passwd (/etc/shadow)</code>
is changed. It is useful when an expired password might be changed by an
application (such as <code class="literal">ssh</code>).
</p><p>
	</p><pre class="programlisting">
#%PAM-1.0
# password-sync
#
auth       requisite    pam_nologin.so
auth       required     pam_unix.so
account    required     pam_unix.so
password   requisite    pam_cracklib.so retry=3
password   requisite    pam_unix.so shadow md5 use_authtok try_first_pass
password   required     pam_smbpass.so nullok use_authtok try_first_pass
session    required     pam_unix.so
</pre></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2660593"></a>Password Migration Configuration</h4></div></div></div><p>
The following PAM configuration shows the use of <code class="filename">pam_smbpass</code> to migrate
from plaintext to encrypted passwords for Samba. Unlike other methods,
this can be used for users who have never connected to Samba shares:
password migration takes place when users <code class="literal">ftp</code> in, login using <code class="literal">ssh</code>, pop
their mail, and so on.
</p><p>
	</p><pre class="programlisting">
#%PAM-1.0
# password-migration
#
auth       requisite   pam_nologin.so
# pam_smbpass is called IF pam_unix succeeds.
auth       requisite   pam_unix.so
auth       optional    pam_smbpass.so migrate
account    required    pam_unix.so
password   requisite   pam_cracklib.so retry=3
password   requisite   pam_unix.so shadow md5 use_authtok try_first_pass
password   optional    pam_smbpass.so nullok use_authtok try_first_pass
session    required    pam_unix.so
</pre></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2660641"></a>Mature Password Configuration</h4></div></div></div><p>
The following is a sample PAM configuration for a mature <code class="filename">smbpasswd</code> installation.
<code class="filename">private/smbpasswd</code> is fully populated, and we consider it an error if
the SMB password does not exist or does not match the UNIX password.
</p><p>
</p><pre class="programlisting">
#%PAM-1.0
# password-mature
#
auth       requisite    pam_nologin.so
auth       required     pam_unix.so
account    required     pam_unix.so
password   requisite    pam_cracklib.so retry=3
password   requisite    pam_unix.so shadow md5 use_authtok try_first_pass
password   required     pam_smbpass.so use_authtok use_first_pass
session    required     pam_unix.so
</pre></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2660680"></a>Kerberos Password Integration Configuration</h4></div></div></div><p>
The following is a sample PAM configuration that shows <em class="parameter"><code>pam_smbpass</code></em> used together with
<em class="parameter"><code>pam_krb5</code></em>. This could be useful on a Samba PDC that is also a member of
a Kerberos realm.
</p><p>
		</p><pre class="programlisting">
#%PAM-1.0
# kdc-pdc
#
auth       requisite   pam_nologin.so
auth       requisite   pam_krb5.so
auth       optional    pam_smbpass.so migrate
account    required    pam_krb5.so
password   requisite   pam_cracklib.so retry=3
password   optional    pam_smbpass.so nullok use_authtok try_first_pass
password   required    pam_krb5.so use_authtok try_first_pass
session    required    pam_krb5.so
</pre></div></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2660722"></a>Common Errors</h2></div></div></div><p>
PAM can be fickle and sensitive to configuration glitches. Here we look at a few cases from
the Samba mailing list.
</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2660733"></a>pam_winbind Problem</h3></div></div></div><p>
	A user reported, <span class="emphasis"><em>I have the following PAM configuration</em></span>:
	</p><p>
</p><pre class="programlisting">
auth required /lib/security/pam_securetty.so
auth sufficient /lib/security/pam_winbind.so
auth sufficient /lib/security/pam_unix.so use_first_pass nullok
auth required /lib/security/pam_stack.so service=system-auth
auth required /lib/security/pam_nologin.so
account required /lib/security/pam_stack.so service=system-auth
account required /lib/security/pam_winbind.so
password required /lib/security/pam_stack.so service=system-auth
</pre><p>
</p><p>
	<span class="emphasis"><em>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;
	I have tried with user &#8220;<span class="quote">scienceu\pitie</span>&#8221; also.</em></span>
	</p><p>
	The problem may lie with the inclusion of <em class="parameter"><code>pam_stack.so
	service=system-auth</code></em>. That file often contains a lot of stuff that may
	duplicate what you are already doing. Try commenting out the <em class="parameter"><code>pam_stack</code></em> lines
	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
	<code class="filename">/etc/pam.d/system-auth</code> and copy only what you need from it into your
	<code class="filename">/etc/pam.d/login</code> file. Alternatively, if you want all services to use
	Winbind, you can put the Winbind-specific stuff in <code class="filename">/etc/pam.d/system-auth</code>.
	</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2660831"></a>Winbind Is Not Resolving Users and Groups</h3></div></div></div><p>
	&#8220;<span class="quote">
	My <code class="filename">smb.conf</code> file is correctly configured. I have specified 
	<a class="link" href="smb.conf.5.html#IDMAPUID">idmap uid = 12000</a> 
	and <a class="link" href="smb.conf.5.html#IDMAPGID">idmap gid = 3000-3500,</a>
	and <code class="literal">winbind</code> is running. When I do the following it all works fine.
	</span>&#8221;
	</p><pre class="screen">
<code class="prompt">root# </code><strong class="userinput"><code>wbinfo -u</code></strong>
MIDEARTH\maryo
MIDEARTH\jackb
MIDEARTH\ameds
...
MIDEARTH\root

<code class="prompt">root# </code><strong class="userinput"><code>wbinfo -g</code></strong>
MIDEARTH\Domain Users
MIDEARTH\Domain Admins
MIDEARTH\Domain Guests
...
MIDEARTH\Accounts

<code class="prompt">root# </code><strong class="userinput"><code>getent passwd</code></strong>
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/bin/bash
...
maryo:x:15000:15003:Mary Orville:/home/MIDEARTH/maryo:/bin/false
</pre><p>
	&#8220;<span class="quote">
	But this command fails:
	</span>&#8221;
</p><pre class="screen">
<code class="prompt">root# </code><strong class="userinput"><code>chown maryo a_file</code></strong>
chown: 'maryo': invalid user
</pre><p>
	&#8220;<span class="quote">This is driving me nuts! What can be wrong?</span>&#8221;
	</p><p>
	Your system is likely running <code class="literal">nscd</code>, the name service
	caching daemon. Shut it down, do not restart it! You will find your problem resolved.
	</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">Chapter27.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">Chapter29.Integrating MS Windows Networks with Samba</td></tr></table></div></body></html>