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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<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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