<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="pam_sm_authenticate">
  <refmeta>
    <refentrytitle>pam_sm_authenticate</refentrytitle>
    <manvolnum>3</manvolnum>
    <refmiscinfo class="source">Linux-PAM</refmiscinfo>
    <refmiscinfo class="manual">Linux-PAM Manual</refmiscinfo>
  </refmeta>

  <refnamediv xml:id="pam_sm_authenticate-name">
    <refname>pam_sm_authenticate</refname>
    <refpurpose>PAM service function for user authentication</refpurpose>
  </refnamediv>

<!-- body begins here -->

  <refsynopsisdiv>
    <funcsynopsis xml:id="pam_sm_authenticate-synopsis">
      <funcsynopsisinfo>#include &lt;security/pam_modules.h&gt;</funcsynopsisinfo>
      <funcprototype>
        <funcdef>int <function>pam_sm_authenticate</function></funcdef>
        <paramdef>pam_handle_t *<parameter>pamh</parameter></paramdef>
        <paramdef>int <parameter>flags</parameter></paramdef>
        <paramdef>int <parameter>argc</parameter></paramdef>
        <paramdef>const char **<parameter>argv</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>


  <refsect1 xml:id="pam_sm_authenticate-description">
    <title>DESCRIPTION</title>
    <para>
      The <function>pam_sm_authenticate</function> function is the service
      module's implementation of the
      <citerefentry>
        <refentrytitle>pam_authenticate</refentrytitle><manvolnum>3</manvolnum>
      </citerefentry> interface.
    </para>
    <para>
      This function performs the task of authenticating the user.
    </para>
    <para>
       Valid flags, which may be logically OR'd with
       <emphasis>PAM_SILENT</emphasis>, are:
    </para>
    <variablelist>
      <varlistentry>
        <term>PAM_SILENT</term>
        <listitem>
           <para>
             Do not emit any messages.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term>PAM_DISALLOW_NULL_AUTHTOK</term>
        <listitem>
          <para>
            Return <emphasis remap="B">PAM_AUTH_ERR</emphasis> if the
            database of authentication tokens for this authentication
            mechanism has a <emphasis>NULL</emphasis> entry for the user.
            Without this flag, such a <emphasis>NULL</emphasis> token
            will lead to a success without the user being prompted.
          </para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 xml:id="pam_sm_authenticate-return_values">
    <title>RETURN VALUES</title>
    <variablelist>
      <varlistentry>
        <term>PAM_AUTH_ERR</term>
        <listitem>
          <para>
            Authentication failure.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term>PAM_CRED_INSUFFICIENT</term>
        <listitem>
          <para>
            For some reason the application does not have sufficient
            credentials to authenticate the user.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term>PAM_AUTHINFO_UNAVAIL</term>
        <listitem>
          <para>
            The modules were not able to access the authentication
            information. This might be due to a network or hardware
            failure etc.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term>PAM_SUCCESS</term>
        <listitem>
           <para>
             The authentication token was successfully updated.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term>PAM_USER_UNKNOWN</term>
        <listitem>
          <para>
            The supplied username is not known to the authentication
            service.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term>PAM_MAXTRIES</term>
        <listitem>
          <para>
            One or more of the authentication modules has reached its
            limit of tries authenticating the user. Do not try again.
          </para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 xml:id="pam_sm_authenticate-see_also">
    <title>SEE ALSO</title>
    <para>
      <citerefentry>
        <refentrytitle>pam</refentrytitle><manvolnum>3</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>pam_authenticate</refentrytitle><manvolnum>3</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>pam_sm_setcred</refentrytitle><manvolnum>3</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>pam_strerror</refentrytitle><manvolnum>3</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>PAM</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>
    </para>
  </refsect1>
</refentry>