LCOV - code coverage report
Current view: directory - objdir/dist/include - mozISanitizingSerializer.h (source / functions) Found Hit Coverage
Test: app.info Lines: 1 0 0.0 %
Date: 2012-06-02 Functions: 1 0 0.0 %

       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
      29                 :  * of those above. If you wish to allow use of your version of this file only
      30                 :  * under the terms of either the GPL or the LGPL, and not to allow others to
      31                 :  * use your version of this file under the terms of the MPL, indicate your
      32                 :  * decision by deleting the provisions above and replace them with the notice
      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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