openssl-decrypt.xml

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

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type class="union"><type>string</type><type>false</type></type><methodname>openssl_decrypt</methodname>
   <methodparam><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 class="union"><type>string</type><type>null</type></type><parameter>tag</parameter><initializer>&null;</initializer></methodparam>
   <methodparam choice="opt"><type>string</type><parameter>aad</parameter><initializer>""</initializer></methodparam>
  </methodsynopsis>
  <para>
   Takes a raw or base64 encoded string and decrypts it using a given method and passphrase.
  </para>

 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>data</parameter></term>
     <listitem>
      <para>
       The encrypted message to be decrypted.
      </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> can be one of
        <constant>OPENSSL_RAW_DATA</constant>,
        <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 in AEAD cipher mode. If it is incorrect, the authentication fails and the function returns &false;.
      </para>
      <caution>
       <simpara>
        The length of the <parameter>tag</parameter> is not checked by the function.
        It is the caller's responsibility to ensure that the length of the tag
        matches the length of the tag retrieved when <function>openssl_encrypt</function>
        has been called. Otherwise the decryption may succeed if the given tag only
        matches the start of the proper tag.
       </simpara>
      </caution>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>aad</parameter></term>
     <listitem>
      <para>
       Additional authenticated data.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   The decrypted 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 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>8.1.0</entry>
      <entry><parameter>tag</parameter> is now nullable.</entry>
     </row>
     <row>
      <entry>7.1.0</entry>
      <entry>The <parameter>tag</parameter> and <parameter>aad</parameter> parameters were added.</entry>
     </row>
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>

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

</refentry>
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