openssl-encrypt.xml

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<refentry xml:id="function.openssl-encrypt" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>openssl_encrypt</refname>
  <refpurpose>Encrypts data</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type class="union"><type>string</type><type>false</type></type><methodname>openssl_encrypt</methodname>
   <methodparam><modifier role="attribute">#[\SensitiveParameter]</modifier><type>string</type><parameter>data</parameter></methodparam>
   <methodparam><type>string</type><parameter>cipher_algo</parameter></methodparam>
   <methodparam><modifier role="attribute">#[\SensitiveParameter]</modifier><type>string</type><parameter>passphrase</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>options</parameter><initializer>0</initializer></methodparam>
   <methodparam choice="opt"><type>string</type><parameter>iv</parameter><initializer>""</initializer></methodparam>
   <methodparam choice="opt"><type>string</type><parameter role="reference">tag</parameter><initializer>&null;</initializer></methodparam>
   <methodparam choice="opt"><type>string</type><parameter>aad</parameter><initializer>""</initializer></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>tag_length</parameter><initializer>16</initializer></methodparam>
  </methodsynopsis>
  <para>
   Encrypts given data with given method and passphrase, returns a raw
   or base64 encoded string
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>data</parameter></term>
     <listitem>
      <para>
       The plaintext message data to be encrypted.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>cipher_algo</parameter></term>
     <listitem>
      <para>
       The cipher method. For a list of available cipher methods, use <function>openssl_get_cipher_methods</function>.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>passphrase</parameter></term>
     <listitem>
      <para>
       The passphrase. If the passphrase is shorter than expected, it is silently padded with
       <literal>NUL</literal> characters; if the passphrase is longer than expected, it is
       silently truncated.
      </para>
      <caution>
       <simpara>
        There is no key derivation function used for <parameter>passphrase</parameter> as its name
        might suggest. The only operation used is padding with <literal>NUL</literal> characters
        or truncation if the length is different than expected.
       </simpara>
      </caution>
     </listitem>
    </varlistentry>
    <varlistentry>
      <term><parameter>options</parameter></term>
      <listitem>
        <para>
          <parameter>options</parameter> is a bitwise disjunction of the flags
          <constant>OPENSSL_RAW_DATA</constant>, and
          <constant>OPENSSL_ZERO_PADDING</constant>
          or <constant>OPENSSL_DONT_ZERO_PAD_KEY</constant>.
        </para>
      </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>iv</parameter></term>
     <listitem>
      <para>
       A non-&null; Initialization Vector. If the IV is shorter than expected, it is padded with
       <literal>NUL</literal> characters and warning is emitted; if the passphrase is longer
       than expected, it is truncated and warning is emitted.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>tag</parameter></term>
     <listitem>
      <para>
       The authentication tag passed by reference when using AEAD cipher mode (GCM or CCM).
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>aad</parameter></term>
     <listitem>
      <para>
       Additional authenticated data.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>tag_length</parameter></term>
     <listitem>
      <para>
       The length of the authentication <parameter>tag</parameter>. Its value can be between 4 and 16 for GCM mode.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns the encrypted string on success&return.falseforfailure;.
  </para>
 </refsect1>

 <refsect1 role="errors">
  &reftitle.errors;
  <para>
   Emits an <constant>E_WARNING</constant> level error if an unknown cipher
   algorithm is passed in via the <parameter>cipher_algo</parameter> parameter.
  </para>
  <para>
   Emits an <constant>E_WARNING</constant> level error if an empty value is passed
   in via the <parameter>iv</parameter> parameter.
  </para>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <informaltable>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>&Version;</entry>
      <entry>&Description;</entry>
     </row>
    </thead>
    <tbody>
     <row>
      <entry>7.1.0</entry>
      <entry>The <parameter>tag</parameter>, <parameter>aad</parameter> and <parameter>tag_length</parameter> parameters were added.</entry>
     </row>
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>


 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>AES Authenticated Encryption in GCM mode example for PHP 7.1+</title>
    <programlisting role="php">
<![CDATA[
<?php
//$key should have been previously generated in a cryptographically safe way, like openssl_random_pseudo_bytes
$plaintext = "message to be encrypted";
$cipher = "aes-128-gcm";
if (in_array($cipher, openssl_get_cipher_methods()))
{
    $ivlen = openssl_cipher_iv_length($cipher);
    $iv = openssl_random_pseudo_bytes($ivlen);
    $ciphertext = openssl_encrypt($plaintext, $cipher, $key, $options=0, $iv, $tag);
    //store $cipher, $iv, and $tag for decryption later
    $original_plaintext = openssl_decrypt($ciphertext, $cipher, $key, $options=0, $iv, $tag);
    echo $original_plaintext."\n";
}
?>
]]>
    </programlisting>
   </example>

   <example>
    <title>AES Authenticated Encryption example prior to PHP 7.1</title>
    <programlisting role="php">
<![CDATA[
<?php
//$key previously generated safely, ie: openssl_random_pseudo_bytes
$plaintext = "message to be encrypted";
$ivlen = openssl_cipher_iv_length($cipher="AES-128-CBC");
$iv = openssl_random_pseudo_bytes($ivlen);
$ciphertext_raw = openssl_encrypt($plaintext, $cipher, $key, $options=OPENSSL_RAW_DATA, $iv);
$hmac = hash_hmac('sha256', $ciphertext_raw, $key, $as_binary=true);
$ciphertext = base64_encode( $iv.$hmac.$ciphertext_raw );

//decrypt later....
$c = base64_decode($ciphertext);
$ivlen = openssl_cipher_iv_length($cipher="AES-128-CBC");
$iv = substr($c, 0, $ivlen);
$hmac = substr($c, $ivlen, $sha2len=32);
$ciphertext_raw = substr($c, $ivlen+$sha2len);
$original_plaintext = openssl_decrypt($ciphertext_raw, $cipher, $key, $options=OPENSSL_RAW_DATA, $iv);
$calcmac = hash_hmac('sha256', $ciphertext_raw, $key, $as_binary=true);
if (hash_equals($hmac, $calcmac))// timing attack safe comparison
{
    echo $original_plaintext."\n";
}
?>
]]>
    </programlisting>
   </example>

  </para>
 </refsect1>


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

</refentry>
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