1 : /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 : /* ***** BEGIN LICENSE BLOCK *****
3 : * Version: MPL 1.1/GPL 2.0/LGPL 2.1
4 : *
5 : * The contents of this file are subject to the Mozilla Public License Version
6 : * 1.1 (the "License"); you may not use this file except in compliance with
7 : * the License. You may obtain a copy of the License at
8 : * http://www.mozilla.org/MPL/
9 : *
10 : * Software distributed under the License is distributed on an "AS IS" basis,
11 : * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
12 : * for the specific language governing rights and limitations under the
13 : * License.
14 : *
15 : * The Original Code is mozilla.org HTML Sanitizer code.
16 : *
17 : * The Initial Developer of the Original Code is
18 : * Ben Bucksch <mozilla@bucksch.org>.
19 : * Portions created by the Initial Developer are Copyright (C) 2002
20 : * the Initial Developer. All Rights Reserved.
21 : *
22 : * Contributor(s):
23 : * Netscape
24 : *
25 : * Alternatively, the contents of this file may be used under the terms of
26 : * either of the GNU General Public License Version 2 or later (the "GPL"),
27 : * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
28 : * in which case the provisions of the GPL or the LGPL are applicable instead
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31 : * use your version of this file under the terms of the MPL, indicate your
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33 : * and other provisions required by the GPL or the LGPL. If you do not delete
34 : * the provisions above, a recipient may use your version of this file under
35 : * the terms of any one of the MPL, the GPL or the LGPL.
36 : *
37 : * ***** END LICENSE BLOCK ***** */
38 :
39 : /* Cleans up HTML source from unwanted tags/attributes
40 :
41 : This class implements a content sink, which takes a parsed HTML document
42 : and removes all tags and attributes that are not explicitly allowed.
43 :
44 : This may improve the viewing experience of the user and/or the
45 : security/privacy.
46 :
47 : What is allowed is defined by a string (format described before the
48 : implementation of |mozHTMLSanitizer::ParsePrefs()|). The sytnax of the
49 : definition is not very rich - you can only (dis)allow certain tags and
50 : attributes, but not where they may appear. (This makes the implementation
51 : much more simple.) E.g. it is impossible to disallow ordinary text as a
52 : direct child of the <head> node or to disallow multiple <head> nodes.
53 :
54 : We also remove some known bad attribute values like javascript: URLs.
55 : Draconian attitude.
56 :
57 : Currently, the output of this class is unparsed (!) HTML source, which
58 : means that each document has to go through the parser twice. Of course,
59 : that is a performance killer. There are some reasons for for me doing it
60 : that way:
61 : * There is, to my knowledge, no interface to hook up such modifiers
62 : in the document display data flow. We have a nice interface for doing
63 : the modifications (the DOM), but no place to get the DOM and to invoke
64 : this code. As I don't want to hack this directly into the html sink,
65 : I'd have to create a generic interface first, which is too much work for
66 : me at the moment.
67 : * It is quite easy to hook up modifiers for the (unparsed) data stream,
68 : both in netwerk (for the browser) and esp. in libmime (for Mailnews).
69 : * It seems like the safest method - it is easier to debug (you have the
70 : HTML source output to check) and is less prone to security-relevant bugs
71 : and regressions, because in the case of a bug, it will probably fall back
72 : to not outputting, which is safer than erring on the side of letting
73 : something slip through (most of the alternative approaches listed below
74 : are probably vulnerable to the latter).
75 : * It should be possible to later change this class to output a parsed HTML
76 : document.
77 : So, in other words, I had the choice between better design and better
78 : performance. I choose design. Bad performance has an effect on the users
79 : of this class only, while bad design has an effect on all users and
80 : programmers.
81 :
82 : That being said, I have some ideas, how do make it much more efficient, but
83 : they involve hacking core code.
84 : * At some point when we have DOM, but didn't do anything with it yet
85 : (in particular, didn't load any external objects or ran any javascript),
86 : walk the DOM and delete everything the user doesn't explicitly like.
87 : * There's this nice GetPref() in the HTMLContentSink. It isn't used exactly
88 : as I would like to, but that should be doable. Bascially, before
89 : processing any tag (e.g. in OpenContainer or AddLeaf), ask that
90 : function, if the tag is allowed. If not, just return.
91 : In any case, there's the problem, how the users of the renderer
92 : (e.g. Mailnews) can tell it to use the sanitizer and which tags are
93 : allowed (the browser may want to allow more tags than Mailnews).
94 : That probably means that I have to hack into the docshell (incl. its
95 : interface) or similar, which I would really like to avoid.
96 : Any ideas appreciated.
97 : */
98 : #ifndef _mozISanitizingSerializer_h__
99 : #define _mozISanitizingSerializer_h__
100 :
101 : #include "nsISupports.h"
102 :
103 : class nsAString;
104 :
105 : #define MOZ_SANITIZINGHTMLSERIALIZER_CONTRACTID "@mozilla.org/layout/htmlsanitizer;1"
106 :
107 : /* starting interface: nsIContentSerializer */
108 : #define MOZ_ISANITIZINGHTMLSERIALIZER_IID_STR "feca3c34-205e-4ae5-bd1c-03c686ff012b"
109 :
110 : #define MOZ_ISANITIZINGHTMLSERIALIZER_IID \
111 : {0xfeca3c34, 0x205e, 0x4ae5, \
112 : { 0xbd, 0x1c, 0x03, 0xc6, 0x86, 0xff, 0x01, 0x2b }}
113 :
114 0 : class mozISanitizingHTMLSerializer : public nsISupports {
115 : public:
116 :
117 : NS_DECLARE_STATIC_IID_ACCESSOR(MOZ_ISANITIZINGHTMLSERIALIZER_IID)
118 :
119 : NS_IMETHOD Initialize(nsAString* aOutString,
120 : PRUint32 aFlags,
121 : const nsAString& allowedTags) = 0;
122 : // This function violates string ownership rules, see impl.
123 : };
124 :
125 : NS_DEFINE_STATIC_IID_ACCESSOR(mozISanitizingHTMLSerializer,
126 : MOZ_ISANITIZINGHTMLSERIALIZER_IID)
127 :
128 : #endif
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