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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>3.5. Authentication token management</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="Linux-PAM_MWG.html" title="The Linux-PAM Module Writers' Guide"><link rel="up" href="mwg-expected-of-module.html" title="Chapter 3. What is expected of a module"><link rel="prev" href="mwg-expected-of-module-session.html" title="3.4. Session management"><link rel="next" href="mwg-see-options.html" title="Chapter 4. Generic optional arguments"></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">3.5. Authentication token management</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="mwg-expected-of-module-session.html">Prev</a> </td><th width="60%" align="center">Chapter 3. What is expected of a module</th><td width="20%" align="right"> <a accesskey="n" href="mwg-see-options.html">Next</a></td></tr></table><hr></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="mwg-expected-of-module-chauthtok"></a>3.5. Authentication token management</h2></div></div></div><p>
        To be correctly initialized, <em class="parameter"><code>PAM_SM_PASSWORD</code></em>
        must be <span class="command"><strong>#define</strong></span>'d prior to including
        <code class="function">&lt;security/pam_modules.h&gt;</code>. This will
        ensure that the prototypes for static modules are properly declared.
      </p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="mwg-pam_sm_chauthtok"></a>3.5.1. Service function to alter authentication token</h3></div></div></div><div class="funcsynopsis"><pre class="funcsynopsisinfo">#define PAM_SM_PASSWORD</pre><pre class="funcsynopsisinfo">#include &lt;security/pam_modules.h&gt;</pre><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">PAM_EXTERN int <b class="fsfunc">pam_sm_chauthtok</b>(</code></td><td><var class="pdparam">pamh</var>, </td><td> </td></tr><tr><td> </td><td><var class="pdparam">flags</var>, </td><td> </td></tr><tr><td> </td><td><var class="pdparam">argc</var>, </td><td> </td></tr><tr><td> </td><td><var class="pdparam">argv</var><code>)</code>;</td><td> </td></tr></table><div class="paramdef-list"><code>pam_handle_t *<var class="pdparam">pamh</var></code>;<br><code>int <var class="pdparam">flags</var></code>;<br><code>int <var class="pdparam">argc</var></code>;<br><code>const char **<var class="pdparam">argv</var></code>;</div><div class="funcprototype-spacer"> </div></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a name="mwg-pam_sm_chauthtok-description"></a>3.5.1.1. DESCRIPTION</h4></div></div></div><p>
      The <code class="function">pam_sm_chauthtok</code> function is the service
      module's implementation of the
      <span class="citerefentry"><span class="refentrytitle">pam_chauthtok</span>(3)</span> interface.
    </p><p>
      This function is used to (re-)set the authentication token of the user.
    </p><p>
       Valid flags, which may be logically OR'd with
       <span class="emphasis"><em>PAM_SILENT</em></span>, are:
    </p><div class="variablelist"><dl class="variablelist"><dt><span class="term">PAM_SILENT</span></dt><dd><p>
             Do not emit any messages.
          </p></dd><dt><span class="term">PAM_CHANGE_EXPIRED_AUTHTOK</span></dt><dd><p>
            This argument indicates to the module that the users
            authentication token (password) should only be changed if
            it has expired. This flag is optional and
            <span class="emphasis"><em>must</em></span> be combined with one of the
            following two flags. Note, however, the following two options
            are <span class="emphasis"><em>mutually exclusive</em></span>.
          </p></dd><dt><span class="term">PAM_PRELIM_CHECK</span></dt><dd><p>
            This indicates that the modules are being probed as to
            their ready status for altering the user's authentication
            token. If the module requires access to another system over
            some network it should attempt to verify it can connect to
            this system on receiving this flag. If a module cannot establish
            it is ready to update the user's authentication token it should
            return <span class="emphasis"><em>PAM_TRY_AGAIN</em></span>, this
            information will be passed back to the application.
          </p><p>
             If the control value <span class="emphasis"><em>sufficient</em></span> is used in
             the password stack, the <span class="emphasis"><em>PAM_PRELIM_CHECK</em></span> section
             of the modules following that control value is not always executed.
          </p></dd><dt><span class="term">PAM_UPDATE_AUTHTOK</span></dt><dd><p>
            This informs the module that this is the call it should change
            the authorization tokens. If the flag is logically OR'd with
            <span class="emphasis"><em>PAM_CHANGE_EXPIRED_AUTHTOK</em></span>, the
            token is only changed if it has actually expired.
          </p></dd></dl></div><p>
      The PAM library calls this function twice in succession. The first
      time with <span class="emphasis"><em>PAM_PRELIM_CHECK</em></span> and then,
      if the module does not return
      <span class="emphasis"><em>PAM_TRY_AGAIN</em></span>, subsequently with
      <span class="emphasis"><em>PAM_UPDATE_AUTHTOK</em></span>. It is only on
      the second call that the authorization token is (possibly) changed.
    </p></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a name="mwg-pam_sm_chauthtok-return_values"></a>3.5.1.2. RETURN VALUES</h4></div></div></div><div class="variablelist"><dl class="variablelist"><dt><span class="term">PAM_AUTHTOK_ERR</span></dt><dd><p>
             The module was unable to obtain the new authentication token.
          </p></dd><dt><span class="term">PAM_AUTHTOK_RECOVERY_ERR</span></dt><dd><p>
            The module was unable to obtain the old authentication token.
          </p></dd><dt><span class="term">PAM_AUTHTOK_LOCK_BUSY</span></dt><dd><p>
            Cannot change the authentication token since it is currently
            locked.
          </p></dd><dt><span class="term">PAM_AUTHTOK_DISABLE_AGING</span></dt><dd><p>
            Authentication token aging has been disabled.
          </p></dd><dt><span class="term">PAM_PERM_DENIED</span></dt><dd><p>
            Permission denied.
          </p></dd><dt><span class="term">PAM_TRY_AGAIN</span></dt><dd><p>
            Preliminary check was unsuccessful. Signals an immediate
            return to the application is desired.
          </p></dd><dt><span class="term">PAM_SUCCESS</span></dt><dd><p>
             The authentication token was successfully updated.
          </p></dd><dt><span class="term">PAM_USER_UNKNOWN</span></dt><dd><p>
            User unknown to password service.
          </p></dd></dl></div></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="mwg-expected-of-module-session.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="mwg-expected-of-module.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="mwg-see-options.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">3.4. Session management </td><td width="20%" align="center"><a accesskey="h" href="Linux-PAM_MWG.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 4. Generic optional arguments</td></tr></table></div></body></html>