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<refentry id='pam_authenticate'>
  <refmeta>
    <refentrytitle>pam_authenticate</refentrytitle>
    <manvolnum>3</manvolnum>
    <refmiscinfo class='setdesc'>Linux-PAM Manual</refmiscinfo>
  </refmeta>

  <refnamediv id="pam_authenticate-name">
    <refname>pam_authenticate</refname>
    <refpurpose>account authentication</refpurpose>
  </refnamediv>

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  <refsynopsisdiv>
    <funcsynopsis id='pam_authenticate-synopsis'>
      <funcsynopsisinfo>#include &lt;security/pam_appl.h&gt;</funcsynopsisinfo>
      <funcprototype>
        <funcdef>int <function>pam_authenticate</function></funcdef>
        <paramdef>pam_handle_t *<parameter>pamh</parameter></paramdef>
        <paramdef>int <parameter>flags</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>


  <refsect1 id='pam_authenticate-description'>
    <title>DESCRIPTION</title>
    <para>
      The <function>pam_authenticate</function> function is used to
      authenticate the user. The user is required to provide an
      authentication token depending upon the authentication service,
      usually this is a password, but could also be a finger print.
    </para>
    <para>
      The PAM service module may request that the user enter their
      username via the conversation mechanism (see
      <citerefentry>
        <refentrytitle>pam_start</refentrytitle><manvolnum>3</manvolnum>
      </citerefentry> and
      <citerefentry>
        <refentrytitle>pam_conv</refentrytitle><manvolnum>3</manvolnum>
      </citerefentry>). The name of the authenticated user
       will be present in the PAM item PAM_USER. This item may be
       recovered with a call to
      <citerefentry>
        <refentrytitle>pam_get_item</refentrytitle><manvolnum>3</manvolnum>
      </citerefentry>.
    </para>
    <para>
      The <emphasis>pamh</emphasis> argument is an authentication
      handle obtained by a prior call to pam_start().
      The flags argument is the binary or of zero or more of the
      following values:
    </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>
            The PAM module service should return PAM_AUTH_ERR
            if the user does not have a registered authentication token.
          </para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 id="pam_authenticate-return_values">
    <title>RETURN VALUES</title>
    <variablelist>
      <varlistentry>
        <term>PAM_ABORT</term>
        <listitem>
          <para>
            The application should exit immediately after calling
            <citerefentry>
              <refentrytitle>pam_end</refentrytitle><manvolnum>3</manvolnum>
            </citerefentry> first.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term>PAM_AUTH_ERR</term>
        <listitem>
          <para>
            The user was not authenticated.
          </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_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>
      <varlistentry>
        <term>PAM_SUCCESS</term>
        <listitem>
           <para>
             The user was successfully authenticated.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term>PAM_USER_UNKNOWN</term>
        <listitem>
          <para>
            User unknown to authentication service.
          </para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 id='pam_authenticate-see_also'>
    <title>SEE ALSO</title>
    <para>
      <citerefentry>
        <refentrytitle>pam_start</refentrytitle><manvolnum>3</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>pam_setcred</refentrytitle><manvolnum>3</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>pam_chauthtok</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>