1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
|
/**
* GNU LibreJS - A browser add-on to block nonfree nontrivial JavaScript.
*
* Copyright (C) 2018 Giorgio Maone <giorgio@maone.net>
* Copyright (C) 2022 Yuchen Pei <id@ypei.org>
*
* This file is part of GNU LibreJS.
*
* GNU LibreJS is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GNU LibreJS is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU LibreJS. If not, see <http://www.gnu.org/licenses/>.
*/
/**
An abstraction layer over the StreamFilter API, allowing its clients to process
only the "interesting" HTML and script requests and leaving the other alone
*/
const { ResponseMetaData } = require('./ResponseMetaData');
const listeners = new WeakMap();
const webRequestEvent = browser.webRequest.onHeadersReceived;
class ResponseProcessor {
static install(handler, types = ['main_frame', 'sub_frame', 'script']) {
if (listeners.has(handler)) return false;
const listener =
async request => await new ResponseTextFilter(request).process(handler);
listeners.set(handler, listener);
webRequestEvent.addListener(
listener,
{ urls: ['<all_urls>'], types },
['blocking', 'responseHeaders']
);
return true;
}
static uninstall(handler) {
const listener = listeners.get(handler);
if (listener) {
webRequestEvent.removeListener(listener);
}
}
}
Object.assign(ResponseProcessor, {
// control flow values to be returned by handler.pre() callbacks
ACCEPT: {},
REJECT: { cancel: true },
CONTINUE: null
});
class ResponseTextFilter {
constructor(request) {
this.request = request;
const { type, statusCode } = request;
const md = this.metaData = new ResponseMetaData(request);
this.canProcess = // we want to process html documents and scripts only
(statusCode < 300 || statusCode >= 400) && // skip redirections
!md.disposition && // skip forced downloads
(type === 'script' || /\bhtml\b/i.test(md.contentType));
}
async process(handler) {
if (!this.canProcess) return ResponseProcessor.ACCEPT;
const { metaData, request } = this;
const response = { request, metaData }; // we keep it around allowing callbacks to store state
if (typeof handler.pre !== 'function' || typeof handler.post !== 'function') {
throw new Error('handler should have a pre and post function.');
}
const res = await handler.pre(response);
if (res) return res;
const { requestId } = request;
// create a filter to modify response data, see
// Mozilla/Add-ons/WebExtensions/API/webRequest/filterResponseData
const filter = browser.webRequest.filterResponseData(requestId);
let buffer = [];
filter.ondata = event => {
buffer.push(event.data);
};
filter.onstop = async _ => {
// concatenate chunks
const size = buffer.reduce((sum, chunk) => sum + chunk.byteLength, 0)
let allBytes = new Uint8Array(size);
let pos = 0;
for (const chunk of buffer) {
allBytes.set(new Uint8Array(chunk), pos);
pos += chunk.byteLength;
}
buffer = null; // allow garbage collection
if (allBytes.indexOf(0) !== -1) {
console.debug('Warning: zeroes in bytestream, probable cached encoding mismatch.', request);
if (request.type === 'script') {
console.debug('It\'s a script, trying to refetch it.');
response.text = await (await fetch(request.url, { cache: 'reload', credentials: 'include' })).text();
} else {
console.debug('It\'s a %s, trying to decode it as UTF-16.', request.type);
response.text = new TextDecoder('utf-16be').decode(allBytes, { stream: true });
}
} else {
response.text = metaData.decode(allBytes);
}
let editedText = null;
try {
editedText = await handler.post(response);
} catch (e) {
console.error(e);
}
if (editedText !== null && editedText !== response.text) {
// we changed the content, let's re-encode
const encoded = new TextEncoder().encode(editedText);
// pre-pending the UTF-8 BOM will force the charset per HTML 5 specs
allBytes = new Uint8Array(encoded.byteLength + 3);
allBytes.set(ResponseMetaData.UTF8BOM, 0); // UTF-8 BOM
allBytes.set(encoded, 3);
}
filter.write(allBytes);
filter.close();
}
return ResponseProcessor.ACCEPT;
}
}
module.exports = { ResponseProcessor };
|
