php-doc-en/reference/openssl/functions/openssl-verify.xml

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<refentry xmlns="http://docbook.org/ns/docbook" xml:id="function.openssl-verify">
 <refnamediv>
  <refname>openssl_verify</refname>
  <refpurpose>Verify signature</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>int</type><methodname>openssl_verify</methodname>
   <methodparam><type>string</type><parameter>data</parameter></methodparam>
   <methodparam><type>string</type><parameter>signature</parameter></methodparam>
   <methodparam><type>mixed</type><parameter>pub_key_id</parameter></methodparam>
   <methodparam choice="opt"><type>mixed</type><parameter>signature_alg</parameter><initializer>OPENSSL_ALGO_SHA1</initializer></methodparam>
  </methodsynopsis>
  <para>
   <function>openssl_verify</function> verifies that the
   <parameter>signature</parameter> is correct for the specified
   <parameter>data</parameter> using the public key associated with
   <parameter>pub_key_id</parameter>. This must be the public key
   corresponding to the private key used for signing.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>data</parameter></term>
     <listitem>
      <para>
       The string of data used to generate the signature previously
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>signature</parameter></term>
     <listitem>
      <para>
       A raw binary string, generated by <function>openssl_sign</function> or similar means
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>pub_key_id</parameter></term>
     <listitem>
      <para>
       <type>resource</type> - a key, returned by <function>openssl_get_publickey</function>
      </para>
      <para>
       <type>string</type> - a PEM formatted key, example, "-----BEGIN PUBLIC KEY-----
MIIBCgK..."
      </para>     
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>signature_alg</parameter></term>
     <listitem>
      <para>
       <type>int</type> - one of these <link linkend="openssl.signature-algos">Signature Algorithms</link>.
      </para>
      <para>
       <type>string</type> - a valid string returned by <function>openssl_get_md_methods</function> example, "sha1WithRSAEncryption" or "sha512".
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns 1 if the signature is correct, 0 if it is incorrect, and
   -1 on error.
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>openssl_verify</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
// $data and $signature are assumed to contain the data and the signature

// fetch public key from certificate and ready it
$pubkeyid = openssl_pkey_get_public("file://src/openssl-0.9.6/demos/sign/cert.pem");

// state whether signature is okay or not
$ok = openssl_verify($data, $signature, $pubkeyid);
if ($ok == 1) {
    echo "good";
} elseif ($ok == 0) {
    echo "bad";
} else {
    echo "ugly, error checking signature";
}
// free the key from memory
openssl_free_key($pubkeyid);
?>
]]>
    </programlisting>
   </example>
   <example>
    <title><function>openssl_verify</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
//data you want to sign
$data = 'my data';

//create new private and public key
$private_key_res = openssl_pkey_new(array(
    "private_key_bits" => 2048,
    "private_key_type" => OPENSSL_KEYTYPE_RSA,
));
$details = openssl_pkey_get_details($private_key_res);
$public_key_res = openssl_pkey_get_public($details['key']);

//create signature
openssl_sign($data, $signature, $private_key_res, "sha256WithRSAEncryption");

//verify signature
$ok = openssl_verify($data, $signature, $public_key_res, OPENSSL_ALGO_SHA256);
if ($ok == 1) {
    echo "valid";
} elseif ($ok == 0) {
    echo "invalid";
} else {
    echo "error: ".openssl_error_string();
}
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>openssl_sign</function></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>

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