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8f797be836
- can be used via html class like:
$clean_html = html::purify($html);
- using it now in eTemplate to remove malicious code from html:
a) when displaying "formatted text"
b) when "formatted text" get's input by the user
374 lines
14 KiB
Plaintext
Executable File
374 lines
14 KiB
Plaintext
Executable File
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Install
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How to install HTML Purifier
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HTML Purifier is designed to run out of the box, so actually using the
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library is extremely easy. (Although... if you were looking for a
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step-by-step installation GUI, you've downloaded the wrong software!)
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While the impatient can get going immediately with some of the sample
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code at the bottom of this library, it's well worth reading this entire
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document--most of the other documentation assumes that you are familiar
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with these contents.
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---------------------------------------------------------------------------
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1. Compatibility
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HTML Purifier is PHP 5 only, and is actively tested from PHP 5.0.5 and
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up. It has no core dependencies with other libraries. PHP
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4 support was deprecated on December 31, 2007 with HTML Purifier 3.0.0.
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These optional extensions can enhance the capabilities of HTML Purifier:
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* iconv : Converts text to and from non-UTF-8 encodings
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* bcmath : Used for unit conversion and imagecrash protection
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* tidy : Used for pretty-printing HTML
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---------------------------------------------------------------------------
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2. Reconnaissance
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A big plus of HTML Purifier is its inerrant support of standards, so
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your web-pages should be standards-compliant. (They should also use
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semantic markup, but that's another issue altogether, one HTML Purifier
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cannot fix without reading your mind.)
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HTML Purifier can process these doctypes:
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* XHTML 1.0 Transitional (default)
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* XHTML 1.0 Strict
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* HTML 4.01 Transitional
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* HTML 4.01 Strict
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* XHTML 1.1
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...and these character encodings:
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* UTF-8 (default)
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* Any encoding iconv supports (with crippled internationalization support)
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These defaults reflect what my choices would be if I were authoring an
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HTML document, however, what you choose depends on the nature of your
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codebase. If you don't know what doctype you are using, you can determine
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the doctype from this identifier at the top of your source code:
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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...and the character encoding from this code:
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<meta http-equiv="Content-type" content="text/html;charset=ENCODING">
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If the character encoding declaration is missing, STOP NOW, and
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read 'docs/enduser-utf8.html' (web accessible at
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http://htmlpurifier.org/docs/enduser-utf8.html). In fact, even if it is
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present, read this document anyway, as many websites specify their
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document's character encoding incorrectly.
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---------------------------------------------------------------------------
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3. Including the library
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The procedure is quite simple:
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require_once '/path/to/library/HTMLPurifier.auto.php';
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This will setup an autoloader, so the library's files are only included
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when you use them.
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Only the contents in the library/ folder are necessary, so you can remove
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everything else when using HTML Purifier in a production environment.
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If you installed HTML Purifier via PEAR, all you need to do is:
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require_once 'HTMLPurifier.auto.php';
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Please note that the usual PEAR practice of including just the classes you
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want will not work with HTML Purifier's autoloading scheme.
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Advanced users, read on; other users can skip to section 4.
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Autoload compatibility
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----------------------
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HTML Purifier attempts to be as smart as possible when registering an
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autoloader, but there are some cases where you will need to change
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your own code to accomodate HTML Purifier. These are those cases:
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PHP VERSION IS LESS THAN 5.1.2, AND YOU'VE DEFINED __autoload
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Because spl_autoload_register() doesn't exist in early versions
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of PHP 5, HTML Purifier has no way of adding itself to the autoload
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stack. Modify your __autoload function to test
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HTMLPurifier_Bootstrap::autoload($class)
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For example, suppose your autoload function looks like this:
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function __autoload($class) {
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require str_replace('_', '/', $class) . '.php';
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return true;
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}
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A modified version with HTML Purifier would look like this:
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function __autoload($class) {
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if (HTMLPurifier_Bootstrap::autoload($class)) return true;
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require str_replace('_', '/', $class) . '.php';
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return true;
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}
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Note that there *is* some custom behavior in our autoloader; the
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original autoloader in our example would work for 99% of the time,
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but would fail when including language files.
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AN __autoload FUNCTION IS DECLARED AFTER OUR AUTOLOADER IS REGISTERED
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spl_autoload_register() has the curious behavior of disabling
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the existing __autoload() handler. Users need to explicitly
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spl_autoload_register('__autoload'). Because we use SPL when it
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is available, __autoload() will ALWAYS be disabled. If __autoload()
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is declared before HTML Purifier is loaded, this is not a problem:
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HTML Purifier will register the function for you. But if it is
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declared afterwards, it will mysteriously not work. This
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snippet of code (after your autoloader is defined) will fix it:
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spl_autoload_register('__autoload')
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Users should also be on guard if they use a version of PHP previous
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to 5.1.2 without an autoloader--HTML Purifier will define __autoload()
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for you, which can collide with an autoloader that was added by *you*
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later.
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For better performance
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----------------------
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Opcode caches, which greatly speed up PHP initialization for scripts
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with large amounts of code (HTML Purifier included), don't like
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autoloaders. We offer an include file that includes all of HTML Purifier's
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files in one go in an opcode cache friendly manner:
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// If /path/to/library isn't already in your include path, uncomment
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// the below line:
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// require '/path/to/library/HTMLPurifier.path.php';
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require 'HTMLPurifier.includes.php';
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Optional components still need to be included--you'll know if you try to
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use a feature and you get a class doesn't exists error! The autoloader
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can be used in conjunction with this approach to catch classes that are
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missing. Simply add this afterwards:
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require 'HTMLPurifier.autoload.php';
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Standalone version
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------------------
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HTML Purifier has a standalone distribution; you can also generate
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a standalone file from the full version by running the script
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maintenance/generate-standalone.php . The standalone version has the
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benefit of having most of its code in one file, so parsing is much
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faster and the library is easier to manage.
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If HTMLPurifier.standalone.php exists in the library directory, you
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can use it like this:
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require '/path/to/HTMLPurifier.standalone.php';
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This is equivalent to including HTMLPurifier.includes.php, except that
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the contents of standalone/ will be added to your path. To override this
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behavior, specify a new HTMLPURIFIER_PREFIX where standalone files can
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be found (usually, this will be one directory up, the "true" library
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directory in full distributions). Don't forget to set your path too!
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The autoloader can be added to the end to ensure the classes are
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loaded when necessary; otherwise you can manually include them.
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To use the autoloader, use this:
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require 'HTMLPurifier.autoload.php';
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For advanced users
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------------------
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HTMLPurifier.auto.php performs a number of operations that can be done
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individually. These are:
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HTMLPurifier.path.php
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Puts /path/to/library in the include path. For high performance,
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this should be done in php.ini.
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HTMLPurifier.autoload.php
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Registers our autoload handler HTMLPurifier_Bootstrap::autoload($class).
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You can do these operations by yourself--in fact, you must modify your own
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autoload handler if you are using a version of PHP earlier than PHP 5.1.2
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(See "Autoload compatibility" above).
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---------------------------------------------------------------------------
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4. Configuration
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HTML Purifier is designed to run out-of-the-box, but occasionally HTML
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Purifier needs to be told what to do. If you answer no to any of these
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questions, read on; otherwise, you can skip to the next section (or, if you're
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into configuring things just for the heck of it, skip to 4.3).
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* Am I using UTF-8?
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* Am I using XHTML 1.0 Transitional?
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If you answered no to any of these questions, instantiate a configuration
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object and read on:
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$config = HTMLPurifier_Config::createDefault();
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4.1. Setting a different character encoding
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You really shouldn't use any other encoding except UTF-8, especially if you
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plan to support multilingual websites (read section three for more details).
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However, switching to UTF-8 is not always immediately feasible, so we can
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adapt.
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HTML Purifier uses iconv to support other character encodings, as such,
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any encoding that iconv supports <http://www.gnu.org/software/libiconv/>
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HTML Purifier supports with this code:
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$config->set('Core', 'Encoding', /* put your encoding here */);
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An example usage for Latin-1 websites (the most common encoding for English
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websites):
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$config->set('Core', 'Encoding', 'ISO-8859-1');
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Note that HTML Purifier's support for non-Unicode encodings is crippled by the
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fact that any character not supported by that encoding will be silently
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dropped, EVEN if it is ampersand escaped. If you want to work around
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this, you are welcome to read docs/enduser-utf8.html for a fix,
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but please be cognizant of the issues the "solution" creates (for this
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reason, I do not include the solution in this document).
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4.2. Setting a different doctype
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For those of you using HTML 4.01 Transitional, you can disable
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XHTML output like this:
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$config->set('HTML', 'Doctype', 'HTML 4.01 Transitional');
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Other supported doctypes include:
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* HTML 4.01 Strict
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* HTML 4.01 Transitional
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* XHTML 1.0 Strict
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* XHTML 1.0 Transitional
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* XHTML 1.1
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4.3. Other settings
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There are more configuration directives which can be read about
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here: <http://htmlpurifier.org/live/configdoc/plain.html> They're a bit boring,
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but they can help out for those of you who like to exert maximum control over
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your code. Some of the more interesting ones are configurable at the
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demo <http://htmlpurifier.org/demo.php> and are well worth looking into
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for your own system.
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For example, you can fine tune allowed elements and attributes, convert
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relative URLs to absolute ones, and even autoparagraph input text! These
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are, respectively, %HTML.Allowed, %URI.MakeAbsolute and %URI.Base, and
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%AutoFormat.AutoParagraph. The %Namespace.Directive naming convention
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translates to:
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$config->set('Namespace', 'Directive', $value);
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E.g.
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$config->set('HTML', 'Allowed', 'p,b,a[href],i');
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$config->set('URI', 'Base', 'http://www.example.com');
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$config->set('URI', 'MakeAbsolute', true);
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$config->set('AutoFormat', 'AutoParagraph', true);
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---------------------------------------------------------------------------
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5. Caching
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HTML Purifier generates some cache files (generally one or two) to speed up
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its execution. For maximum performance, make sure that
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library/HTMLPurifier/DefinitionCache/Serializer is writeable by the webserver.
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If you are in the library/ folder of HTML Purifier, you can set the
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appropriate permissions using:
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chmod -R 0755 HTMLPurifier/DefinitionCache/Serializer
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If the above command doesn't work, you may need to assign write permissions
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to all. This may be necessary if your webserver runs as nobody, but is
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not recommended since it means any other user can write files in the
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directory. Use:
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chmod -R 0777 HTMLPurifier/DefinitionCache/Serializer
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You can also chmod files via your FTP client; this option
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is usually accessible by right clicking the corresponding directory and
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then selecting "chmod" or "file permissions".
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Starting with 2.0.1, HTML Purifier will generate friendly error messages
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that will tell you exactly what you have to chmod the directory to, if in doubt,
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follow its advice.
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If you are unable or unwilling to give write permissions to the cache
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directory, you can either disable the cache (and suffer a performance
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hit):
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$config->set('Core', 'DefinitionCache', null);
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Or move the cache directory somewhere else (no trailing slash):
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$config->set('Cache', 'SerializerPath', '/home/user/absolute/path');
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---------------------------------------------------------------------------
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6. Using the code
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The interface is mind-numbingly simple:
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$purifier = new HTMLPurifier();
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$clean_html = $purifier->purify( $dirty_html );
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...or, if you're using the configuration object:
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$purifier = new HTMLPurifier($config);
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$clean_html = $purifier->purify( $dirty_html );
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That's it! For more examples, check out docs/examples/ (they aren't very
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different though). Also, docs/enduser-slow.html gives advice on what to
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do if HTML Purifier is slowing down your application.
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---------------------------------------------------------------------------
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7. Quick install
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First, make sure library/HTMLPurifier/DefinitionCache/Serializer is
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writable by the webserver (see Section 5: Caching above for details).
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If your website is in UTF-8 and XHTML Transitional, use this code:
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<?php
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require_once '/path/to/htmlpurifier/library/HTMLPurifier.auto.php';
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$purifier = new HTMLPurifier();
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$clean_html = $purifier->purify($dirty_html);
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?>
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If your website is in a different encoding or doctype, use this code:
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<?php
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require_once '/path/to/htmlpurifier/library/HTMLPurifier.auto.php';
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$config = HTMLPurifier_Config::createDefault();
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$config->set('Core', 'Encoding', 'ISO-8859-1'); // replace with your encoding
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$config->set('HTML', 'Doctype', 'HTML 4.01 Transitional'); // replace with your doctype
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$purifier = new HTMLPurifier($config);
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$clean_html = $purifier->purify($dirty_html);
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?>
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vim: et sw=4 sts=4
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