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129 lines
6.0 KiB
C
129 lines
6.0 KiB
C
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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is mozilla.org HTML Sanitizer code.
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*
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* The Initial Developer of the Original Code is
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* Ben Bucksch <mozilla@bucksch.org>.
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* Portions created by the Initial Developer are Copyright (C) 2002
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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* Netscape
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either of the GNU General Public License Version 2 or later (the "GPL"),
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* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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/* Cleans up HTML source from unwanted tags/attributes
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This class implements a content sink, which takes a parsed HTML document
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and removes all tags and attributes that are not explicitly allowed.
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This may improve the viewing experience of the user and/or the
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security/privacy.
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What is allowed is defined by a string (format described before the
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implementation of |mozHTMLSanitizer::ParsePrefs()|). The sytnax of the
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definition is not very rich - you can only (dis)allow certain tags and
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attributes, but not where they may appear. (This makes the implementation
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much more simple.) E.g. it is impossible to disallow ordinary text as a
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direct child of the <head> node or to disallow multiple <head> nodes.
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We also remove some known bad attribute values like javascript: URLs.
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Draconian attitude.
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Currently, the output of this class is unparsed (!) HTML source, which
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means that each document has to go through the parser twice. Of course,
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that is a performance killer. There are some reasons for for me doing it
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that way:
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* There is, to my knowledge, no interface to hook up such modifiers
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in the document display data flow. We have a nice interface for doing
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the modifications (the DOM), but no place to get the DOM and to invoke
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this code. As I don't want to hack this directly into the html sink,
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I'd have to create a generic interface first, which is too much work for
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me at the moment.
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* It is quite easy to hook up modifiers for the (unparsed) data stream,
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both in netwerk (for the browser) and esp. in libmime (for Mailnews).
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* It seems like the safest method - it is easier to debug (you have the
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HTML source output to check) and is less prone to security-relevant bugs
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and regressions, because in the case of a bug, it will probably fall back
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to not outputting, which is safer than erring on the side of letting
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something slip through (most of the alternative approaches listed below
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are probably vulnerable to the latter).
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* It should be possible to later change this class to output a parsed HTML
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document.
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So, in other words, I had the choice between better design and better
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performance. I choose design. Bad performance has an effect on the users
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of this class only, while bad design has an effect on all users and
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programmers.
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That being said, I have some ideas, how do make it much more efficient, but
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they involve hacking core code.
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* At some point when we have DOM, but didn't do anything with it yet
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(in particular, didn't load any external objects or ran any javascript),
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walk the DOM and delete everything the user doesn't explicitly like.
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* There's this nice GetPref() in the HTMLContentSink. It isn't used exactly
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as I would like to, but that should be doable. Bascially, before
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processing any tag (e.g. in OpenContainer or AddLeaf), ask that
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function, if the tag is allowed. If not, just return.
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In any case, there's the problem, how the users of the renderer
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(e.g. Mailnews) can tell it to use the sanitizer and which tags are
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allowed (the browser may want to allow more tags than Mailnews).
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That probably means that I have to hack into the docshell (incl. its
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interface) or similar, which I would really like to avoid.
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Any ideas appreciated.
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*/
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#ifndef _mozISanitizingSerializer_h__
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#define _mozISanitizingSerializer_h__
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#include "nsISupports.h"
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class nsAString;
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#define MOZ_SANITIZINGHTMLSERIALIZER_CONTRACTID "@mozilla.org/layout/htmlsanitizer;1"
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/* starting interface: nsIContentSerializer */
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#define MOZ_ISANITIZINGHTMLSERIALIZER_IID_STR "feca3c34-205e-4ae5-bd1c-03c686ff012b"
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#define MOZ_ISANITIZINGHTMLSERIALIZER_IID \
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{0xfeca3c34, 0x205e, 0x4ae5, \
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{ 0xbd, 0x1c, 0x03, 0xc6, 0x86, 0xff, 0x01, 0x2b }}
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class mozISanitizingHTMLSerializer : public nsISupports {
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public:
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NS_DECLARE_STATIC_IID_ACCESSOR(MOZ_ISANITIZINGHTMLSERIALIZER_IID)
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NS_IMETHOD Initialize(nsAString* aOutString,
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PRUint32 aFlags,
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const nsAString& allowedTags) = 0;
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// This function violates string ownership rules, see impl.
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};
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NS_DEFINE_STATIC_IID_ACCESSOR(mozISanitizingHTMLSerializer,
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MOZ_ISANITIZINGHTMLSERIALIZER_IID)
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#endif
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