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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.8 $ -->
<chapter id="security.magicquotes">
<title>Magic Quotes</title>
<para>
Magic Quotes is a process that automagically escapes incoming data to the
PHP script. It's preferred to code with magic quotes off and to instead
escape the data at runtime, as needed.
</para>
<sect1 id="security.magicquotes.what">
<title>What are Magic Quotes</title>
<para>
When on, all <literal>'</literal> (single-quote), <literal>"</literal>
(double quote), <literal>\</literal> (backslash) and <literal>NULL</literal>
characters are escaped with a backslash automatically. This is identical
to what <function>addslashes</function> does.
</para>
<para>
There are three magic quote directives:
</para>
<itemizedlist>
<listitem>
<simpara>
<link linkend="ini.magic-quotes-gpc">magic_quotes_gpc</link>
</simpara>
<simpara>
Affects HTTP Request data (GET, POST, and COOKIE). Cannot be set at
runtime, and defaults to <emphasis>on</emphasis> in PHP.
</simpara>
<simpara>
See also <function>get_magic_quotes_gpc</function>.
</simpara>
</listitem>
<listitem>
<simpara>
<link linkend="ini.magic-quotes-runtime">magic_quotes_runtime</link>
</simpara>
<simpara>
If enabled, most functions that return data from an external source,
including databases and text files, will have quotes escaped with a
backslash. Can be set at runtime, and defaults to <emphasis>off</emphasis>
in PHP.
</simpara>
<simpara>
See also <function>set_magic_quotes_runtime</function> and
<function>get_magic_quotes_runtime</function>.
</simpara>
</listitem>
<listitem>
<simpara>
<link linkend="ini.magic-quotes-sybase">magic_quotes_sybase</link>
</simpara>
<simpara>
If enabled, a single-quote is escaped with a single-quote instead of a
backslash. If on, it completely overrides
<link linkend="ini.magic-quotes-gpc">magic_quotes_gpc</link>. Having
both directives enabled means only single quotes are escaped as
<literal>''</literal>. Double quotes, backslashes and NULL's will
remain untouched and unescaped.
</simpara>
<simpara>
See also <function>ini_get</function> for retrieving its value.
</simpara>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="security.magicquotes.why">
<title>Why use Magic Quotes</title>
<itemizedlist>
<listitem>
<simpara>
Useful for beginners
</simpara>
<simpara>
Magic quotes are implemented in PHP to help code written by beginners
from being dangerous. Although
<link linkend="security.database.sql-injection">SQL Injection</link>
is still possible with magic quotes on, the risk is reduced.
</simpara>
</listitem>
<listitem>
<simpara>
Convenience
</simpara>
<simpara>
For inserting data into a database, magic quotes essentially runs
<function>addslashes</function> on all Get, Post, and Cookie data,
and does so automagically.
</simpara>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="security.magicquotes.whynot">
<title>Why not to use Magic Quotes</title>
<itemizedlist>
<listitem>
<simpara>
Portability
</simpara>
<simpara>
Assuming it to be on, or off, affects portability. Use
<function>get_magic_quotes_gpc</function> to check for this, and code
accordingly.
</simpara>
</listitem>
<listitem>
<simpara>
Performance
</simpara>
<simpara>
Because not every piece of escaped data is inserted into a
database, there is a performance loss for escaping all this data.
Simply calling on the escaping functions (like
<function>addslashes</function>) at runtime is more efficient.
</simpara>
<simpara>
Although <filename>php.ini-dist</filename> enables these directives
by default, <filename>php.ini-recommended</filename> disables it.
This recommendation is mainly due to performance reasons.
</simpara>
</listitem>
<listitem>
<simpara>
Inconvenience
</simpara>
<simpara>
Because not all data needs escaping, it's often annoying to see escaped
data where it shouldn't be. For example, emailing from a form, and
seeing a bunch of \' within the email. To fix, this may require
excessive use of <function>stripslashes</function>.
</simpara>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="security.magicquotes.disabling">
<title>Disabling Magic Quotes</title>
<para>
The <link linkend="ini.magic-quotes-gpc">magic_quotes_gpc</link>
directive may only be disabled at the system level, and not at
runtime. In otherwords, use of <function>ini_set</function> is not
an option.
</para>
<para>
<example>
<title>Disabling magic quotes server side</title>
<para>
An example that sets the value of these directives to
<literal>Off</literal> in &php.ini;. For additional details, read the
manual section titled <link linkend="configuration.changes">How to
change configuration settings</link>.
</para>
<screen>
<![CDATA[
; Magic quotes
;
; Magic quotes for incoming GET/POST/Cookie data.
magic_quotes_gpc = Off
; Magic quotes for runtime-generated data, e.g. data from SQL, from exec(), etc.
magic_quotes_runtime = Off
; Use Sybase-style magic quotes (escape ' with '' instead of \').
magic_quotes_sybase = Off
]]>
</screen>
<para>
If access to the server configuration is unavailable, use of
<filename>.htaccess</filename> is also an option. For example:
</para>
<screen>
<![CDATA[
php_flag magic_quotes_gpc Off
]]>
</screen>
</example>
</para>
<para>
In the interest of writing portable code (code that works in any
environment), like if setting at the server level is not possible,
here's an example to disable <link linkend="ini.magic-quotes-gpc">
magic_quotes_gpc</link> at runtime. This method is inefficient so
it's preferred to instead set the appropriate directives elsewhere.
</para>
<para>
<example>
<title>Disabling magic quotes at runtime</title>
<programlisting role="php">
<![CDATA[
<?php
if (get_magic_quotes_gpc()) {
function stripslashes_deep($value)
{
$value = is_array($value) ?
array_map('stripslashes_deep', $value) :
stripslashes($value);
return $value;
}
$_POST = array_map('stripslashes_deep', $_POST);
$_GET = array_map('stripslashes_deep', $_GET);
$_COOKIE = array_map('stripslashes_deep', $_COOKIE);
$_REQUEST = array_map('stripslashes_deep', $_REQUEST);
}
?>
]]>
</programlisting>
</example>
</para>
</sect1>
</chapter>
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