| 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
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380 |
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
9
4
1
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
| // © 2013 - 2016 Rob Wu <rob@robwu.nl>
// Released under the MIT license
'use strict';
var httpProxy = require('http-proxy');
var net = require('net');
var url = require('url');
var regexp_tld = require('./regexp-top-level-domain');
var getProxyForUrl = require('proxy-from-env').getProxyForUrl;
var help_text = {};
function showUsage(help_file, headers, response) {
var isHtml = /\.html$/.test(help_file);
headers['content-type'] = isHtml ? 'text/html' : 'text/plain';
if (help_text[help_file] != null) {
response.writeHead(200, headers);
response.end(help_text[help_file]);
} else {
require('fs').readFile(help_file, 'utf8', function(err, data) {
if (err) {
console.error(err);
response.writeHead(500, headers);
response.end();
} else {
help_text[help_file] = data;
showUsage(help_file, headers, response); // Recursive call, but since data is a string, the recursion will end
}
});
}
}
/**
* Check whether the specified hostname is valid.
*
* @param hostname {string} Host name (excluding port) of requested resource.
* @return {boolean} Whether the requested resource can be accessed.
*/
function isValidHostName(hostname) {
return !!(
regexp_tld.test(hostname) ||
net.isIPv4(hostname) ||
net.isIPv6(hostname)
);
}
/**
* Adds CORS headers to the response headers.
*
* @param headers {object} Response headers
* @param request {ServerRequest}
*/
function withCORS(headers, request) {
headers['access-control-allow-origin'] = '*';
if (request.headers['access-control-request-method']) {
headers['access-control-allow-methods'] = request.headers['access-control-request-method'];
delete request.headers['access-control-request-method'];
}
if (request.headers['access-control-request-headers']) {
headers['access-control-allow-headers'] = request.headers['access-control-request-headers'];
delete request.headers['access-control-request-headers'];
}
headers['access-control-expose-headers'] = Object.keys(headers).join(',');
return headers;
}
/**
* Performs the actual proxy request.
*
* @param req {ServerRequest} Incoming http request
* @param res {ServerResponse} Outgoing (proxied) http request
* @param proxy {HttpProxy}
*/
function proxyRequest(req, res, proxy) {
var location = req.corsAnywhereRequestState.location;
req.url = location.path;
var proxyOptions = {
changeOrigin: false,
prependPath: false,
target: location,
headers: {
host: location.host,
},
};
var proxyThroughUrl = req.corsAnywhereRequestState.getProxyForUrl(location.href);
if (proxyThroughUrl) {
proxyOptions.target = proxyThroughUrl;
proxyOptions.toProxy = true;
// If a proxy URL was set, req.url must be an absolute URL. Then the request will not be sent
// directly to the proxied URL, but through another proxy.
req.url = location.href;
}
// Start proxying the request
proxy.web(req, res, proxyOptions);
}
/**
* "Allow observer to modify headers or abort response"
* https://github.com/nodejitsu/node-http-proxy/blob/v1.11.1/lib/http-proxy/passes/web-incoming.js#L147
*
* This method modifies the response headers of the proxied response.
* If a redirect is detected, the response is not sent to the client,
* and a new request is initiated.
*
* @param response {ClientRequest} The response of the proxied request
* @param req {IncomingMessage} Incoming HTTP request, augmented with property corsAnywhereRequestState
* @param req.corsAnywhereRequestState {object}
* @param req.corsAnywhereRequestState.location {object} See parseURL
* @param req.corsAnywhereRequestState.getProxyForUrl {function} See proxyRequest
* @param req.corsAnywhereRequestState.proxyBaseUrl {string} Base URL of the CORS API endpoint
* @param req.corsAnywhereRequestState.maxRedirects {number} Maximum number of redirects
* @param req.corsAnywhereRequestState.redirectCount_ {number} Internally used to count redirects
* @param res {ServerResponse} Outgoing (proxied) HTTP request
*
* @this {HttpProxy}
*/
function onProxyResponse(response, req, res) {
var proxy = this;
var requestState = req.corsAnywhereRequestState;
var statusCode = response.statusCode;
if (!requestState.redirectCount_) {
res.setHeader('x-request-url', requestState.location.href);
}
// Handle redirects
if (statusCode === 301 || statusCode === 302 || statusCode === 303 || statusCode === 307 || statusCode === 308) {
var locationHeader = response.headers.location;
if (locationHeader) {
locationHeader = url.resolve(requestState.location.href, locationHeader);
if (statusCode === 301 || statusCode === 302 || statusCode === 303) {
// Exclude 307 & 308, because they are rare, and require preserving the method + request body
requestState.redirectCount_ = requestState.redirectCount_ + 1 || 1;
if (requestState.redirectCount_ <= requestState.maxRedirects) {
// Handle redirects within the server, because some clients (e.g. Android Stock Browser)
// cancel redirects.
// Set header for debugging purposes. Do not try to parse it!
res.setHeader('X-CORS-Redirect-' + requestState.redirectCount_, statusCode + ' ' + locationHeader);
req.method = 'GET';
req.headers['content-length'] = '0';
delete req.headers['content-type'];
requestState.location = parseURL(locationHeader);
// ### Dispose the current proxied request
// Haha - hack! This should be fixed when (if?) node-http-proxy supports cancelation of requests..
// Shadow all methods that mutate the |res| object.
// See https://github.com/nodejitsu/node-http-proxy/blob/v1.11.1/lib/http-proxy/passes/web-outgoing.js#L73-L100
var setHeader = res.setHeader;
var writeHead = res.writeHead;
res.setHeader = res.writeHead = function noop() {};
response.on = function noop2() {};
response.pipe = function(res) {
res.setHeader = setHeader;
res.writeHead = writeHead;
// Trigger proxyReq.abort() (this is not of any imporance, it's just used to stop wasting resources.)
// https://github.com/nodejitsu/node-http-proxy/blob/v1.11.1/lib/http-proxy/passes/web-incoming.js#L125-L128
req.emit('aborted');
// Remove all listeners (=reset events to initial state)
req.removeAllListeners();
// Initiate a new proxy request.
proxyRequest(req, res, proxy);
};
return;
}
}
response.headers.location = requestState.proxyBaseUrl + '/' + locationHeader;
}
}
// Strip cookies
delete response.headers['set-cookie'];
delete response.headers['set-cookie2'];
response.headers['x-final-url'] = requestState.location.href;
withCORS(response.headers, req);
}
/**
* @param req_url {string} The requested URL (scheme is optional).
* @return {object} URL parsed using url.parse
*/
function parseURL(req_url) {
var match = req_url.match(/^(?:(https?:)?\/\/)?(([^\/?]+?)(?::(\d{0,5})(?=[\/?]|$))?)([\/?][\S\s]*|$)/i);
// ^^^^^^^ ^^^^^^^^ ^^^^^^^ ^^^^^^^^^^^^
// 1:protocol 3:hostname 4:port 5:path + query string
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
// 2:host
if (!match) {
return null;
}
if (!match[1]) {
// Scheme is omitted.
if (req_url.lastIndexOf('//', 0) === -1) {
// "//" is omitted.
req_url = '//' + req_url;
}
req_url = (match[4] === '443' ? 'https:' : 'http:') + req_url;
}
return url.parse(req_url);
}
// Request handler factory
function getHandler(options, proxy) {
var corsAnywhere = {
getProxyForUrl: getProxyForUrl, // Function that specifies the proxy to use
maxRedirects: 5, // Maximum number of redirects to be followed.
originBlacklist: [], // Requests from these origins will be blocked.
originWhitelist: [], // If non-empty, requests not from an origin in this list will be blocked.
redirectSameOrigin: false, // Redirect the client to the requested URL for same-origin requests.
requireHeader: null, // Require a header to be set?
removeHeaders: [], // Strip these request headers.
setHeaders: {}, // Set these request headers.
helpFile: __dirname + '/help.txt',
};
Object.keys(corsAnywhere).forEach(function(option) {
if (Object.prototype.hasOwnProperty.call(options, option)) {
corsAnywhere[option] = options[option];
}
});
// Convert corsAnywhere.requireHeader to an array of lowercase header names, or null.
Eif (corsAnywhere.requireHeader) {
Iif (typeof corsAnywhere.requireHeader === 'string') {
corsAnywhere.requireHeader = [corsAnywhere.requireHeader.toLowerCase()];
} else Iif (!Array.isArray(corsAnywhere.requireHeader) || corsAnywhere.requireHeader.length === 0) {
corsAnywhere.requireHeader = null;
} else {
corsAnywhere.requireHeader = corsAnywhere.requireHeader.map(function(headerName) {
return headerName.toLowerCase();
});
}
}
var hasRequiredHeaders = function(headers) {
return !corsAnywhere.requireHeader || corsAnywhere.requireHeader.some(function(headerName) {
return Object.hasOwnProperty.call(headers, headerName);
});
};
return function(req, res) {
var cors_headers = withCORS({}, req);
if (req.method === 'OPTIONS') {
// Pre-flight request. Reply successfully:
res.writeHead(200, cors_headers);
res.end();
return;
}
var location = parseURL(req.url.slice(1));
if (!location) {
// Invalid API call. Show how to correctly use the API
showUsage(corsAnywhere.helpFile, cors_headers, res);
return;
}
if (location.host === 'iscorsneeded') {
// Is CORS needed? This path is provided so that API consumers can test whether it's necessary
// to use CORS. The server's reply is always No, because if they can read it, then CORS headers
// are not necessary.
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('no');
return;
}
if (location.port > 65535) {
// Port is higher than 65535
res.writeHead(400, 'Invalid port', cors_headers);
res.end('Port number too large: ' + location.port);
return;
}
if (!/^\/https?:/.test(req.url) && !isValidHostName(location.hostname)) {
// Don't even try to proxy invalid hosts (such as /favicon.ico, /robots.txt)
res.writeHead(404, 'Invalid host', cors_headers);
res.end('Invalid host: ' + location.hostname);
return;
}
if (!hasRequiredHeaders(req.headers)) {
res.writeHead(400, 'Header required', cors_headers);
res.end('Missing required request header. Must specify one of: ' + corsAnywhere.requireHeader);
return;
}
var origin = req.headers.origin || '';
if (corsAnywhere.originBlacklist.indexOf(origin) >= 0) {
res.writeHead(403, 'Forbidden', cors_headers);
res.end('The origin "' + origin + '" was blacklisted by the operator of this proxy.');
return;
}
if (corsAnywhere.originWhitelist.length && corsAnywhere.originWhitelist.indexOf(origin) === -1) {
res.writeHead(403, 'Forbidden', cors_headers);
res.end('The origin "' + origin + '" was not whitelisted by the operator of this proxy.');
return;
}
if (corsAnywhere.redirectSameOrigin && origin && location.href[origin.length] === '/' &&
location.href.lastIndexOf(origin, 0) === 0) {
// Send a permanent redirect to offload the server. Badly coded clients should not waste our resources.
cors_headers.vary = 'origin';
cors_headers['cache-control'] = 'private';
cors_headers.location = location.href;
res.writeHead(301, 'Please use a direct request', cors_headers);
res.end();
return;
}
var isRequestedOverHttps = req.connection.encrypted || /^\s*https/.test(req.headers['x-forwarded-proto']);
var proxyBaseUrl = (isRequestedOverHttps ? 'https://' : 'http://') + req.headers.host;
corsAnywhere.removeHeaders.forEach(function(header) {
delete req.headers[header];
});
Object.keys(corsAnywhere.setHeaders).forEach(function(header) {
req.headers[header] = corsAnywhere.setHeaders[header];
});
req.corsAnywhereRequestState = {
location: location,
getProxyForUrl: corsAnywhere.getProxyForUrl,
maxRedirects: corsAnywhere.maxRedirects,
proxyBaseUrl: proxyBaseUrl,
};
proxyRequest(req, res, proxy);
};
}
// Create server with default and given values
// Creator still needs to call .listen()
exports.createServer = function createServer(options) {
options = options || {};
// Default options:
var httpProxyOptions = {
xfwd: true, // Append X-Forwarded-* headers
};
// Allow user to override defaults and add own options
Eif (options.httpProxyOptions) {
Object.keys(options.httpProxyOptions).forEach(function(option) {
httpProxyOptions[option] = options.httpProxyOptions[option];
});
}
var proxy = httpProxy.createServer(httpProxyOptions);
var requestHandler = getHandler(options, proxy);
var server;
Iif (options.httpsOptions) {
server = require('https').createServer(options.httpsOptions, requestHandler);
} else {
server = require('http').createServer(requestHandler);
}
// When the server fails, just show a 404 instead of Internal server error
proxy.on('error', function(err, req, res) {
if (res.headersSent) {
// This could happen when a protocol error occurs when an error occurs
// after the headers have been received (and forwarded). Do not write
// the headers because it would generate an error.
return;
}
res.writeHead(404, {'Access-Control-Allow-Origin': '*'});
res.end('Not found because of proxy error: ' + err);
});
proxy.on('proxyRes', onProxyResponse);
return server;
};
|