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cors-anywhere-docker/lib/cors-anywhere.js

463 lines
18 KiB
JavaScript

// © 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'] = '*';
var corsMaxAge = request.corsAnywhereRequestState.corsMaxAge;
if (request.method === 'OPTIONS' && corsMaxAge) {
headers['access-control-max-age'] = corsMaxAge;
}
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,
},
// HACK: Get hold of the proxyReq object, because we need it later.
// https://github.com/nodejitsu/node-http-proxy/blob/v1.11.1/lib/http-proxy/passes/web-incoming.js#L144
buffer: {
pipe: function(proxyReq) {
var proxyReqOn = proxyReq.on;
// Intercepts the handler that connects proxyRes to res.
// https://github.com/nodejitsu/node-http-proxy/blob/v1.11.1/lib/http-proxy/passes/web-incoming.js#L146-L158
proxyReq.on = function(eventName, listener) {
if (eventName !== 'response') {
return proxyReqOn.call(this, eventName, listener);
}
return proxyReqOn.call(this, 'response', function(proxyRes) {
if (onProxyResponse(proxy, proxyReq, proxyRes, req, res)) {
try {
listener(proxyRes);
} catch (err) {
// Wrap in try-catch because an error could occur:
// "RangeError: Invalid status code: 0"
// https://github.com/Rob--W/cors-anywhere/issues/95
// https://github.com/nodejitsu/node-http-proxy/issues/1080
// Forward error (will ultimately emit the 'error' event on our proxy object):
// https://github.com/nodejitsu/node-http-proxy/blob/v1.11.1/lib/http-proxy/passes/web-incoming.js#L134
proxyReq.emit('error', err);
}
}
});
};
return req.pipe(proxyReq);
},
},
};
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
try {
proxy.web(req, res, proxyOptions);
} catch (err) {
proxy.emit('error', err, req, res);
}
}
/**
* 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.
*
* client (req) -> CORS Anywhere -> (proxyReq) -> other server
* client (res) <- CORS Anywhere <- (proxyRes) <- other server
*
* @param proxy {HttpProxy}
* @param proxyReq {ClientRequest} The outgoing request to the other server.
* @param proxyRes {ServerResponse} The response from the other server.
* @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 response to the client that wanted to proxy the HTTP request.
*
* @returns {boolean} true if http-proxy should continue to pipe proxyRes to res.
*/
function onProxyResponse(proxy, proxyReq, proxyRes, req, res) {
var requestState = req.corsAnywhereRequestState;
var statusCode = proxyRes.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 = proxyRes.headers.location;
var parsedLocation;
if (locationHeader) {
locationHeader = url.resolve(requestState.location.href, locationHeader);
parsedLocation = parseURL(locationHeader);
}
if (parsedLocation) {
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 = parsedLocation;
// Remove all listeners (=reset events to initial state)
req.removeAllListeners();
// Remove the error listener so that the ECONNRESET "error" that
// may occur after aborting a request does not propagate to res.
// https://github.com/nodejitsu/node-http-proxy/blob/v1.11.1/lib/http-proxy/passes/web-incoming.js#L134
proxyReq.removeAllListeners('error');
proxyReq.once('error', function catchAndIgnoreError() {});
proxyReq.abort();
// Initiate a new proxy request.
proxyRequest(req, res, proxy);
return false;
}
}
proxyRes.headers.location = requestState.proxyBaseUrl + '/' + locationHeader;
}
}
// Strip cookies
delete proxyRes.headers['set-cookie'];
delete proxyRes.headers['set-cookie2'];
proxyRes.headers['x-final-url'] = requestState.location.href;
withCORS(proxyRes.headers, req);
return true;
}
/**
* @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]) {
if (/^https?:/i.test(req_url)) {
// The pattern at top could mistakenly parse "http:///" as host="http:" and path=///.
return null;
}
// Scheme is omitted.
if (req_url.lastIndexOf('//', 0) === -1) {
// "//" is omitted.
req_url = '//' + req_url;
}
req_url = (match[4] === '443' ? 'https:' : 'http:') + req_url;
}
var parsed = url.parse(req_url);
if (!parsed.hostname) {
// "http://:1/" and "http:/notenoughslashes" could end up here.
return null;
}
return parsed;
}
// Request handler factory
function getHandler(options, proxy) {
var corsAnywhere = {
handleInitialRequest: null, // Function that may handle the request instead, by returning a truthy value.
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.
checkRateLimit: null, // Function that may enforce a rate-limit by returning a non-empty string.
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.
corsMaxAge: 0, // If set, an Access-Control-Max-Age header with this value (in seconds) will be added.
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.
if (corsAnywhere.requireHeader) {
if (typeof corsAnywhere.requireHeader === 'string') {
corsAnywhere.requireHeader = [corsAnywhere.requireHeader.toLowerCase()];
} else if (!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) {
req.corsAnywhereRequestState = {
getProxyForUrl: corsAnywhere.getProxyForUrl,
maxRedirects: corsAnywhere.maxRedirects,
corsMaxAge: corsAnywhere.corsMaxAge,
};
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 (corsAnywhere.handleInitialRequest && corsAnywhere.handleInitialRequest(req, res, location)) {
return;
}
if (!location) {
// Special case http:/notenoughslashes, because new users of the library frequently make the
// mistake of putting this application behind a server/router that normalizes the URL.
// See https://github.com/Rob--W/cors-anywhere/issues/238#issuecomment-629638853
if (/^\/https?:\/[^/]/i.test(req.url)) {
res.writeHead(400, 'Missing slash', cors_headers);
res.end('The URL is invalid: two slashes are needed after the http(s):.');
return;
}
// 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;
}
var rateLimitMessage = corsAnywhere.checkRateLimit && corsAnywhere.checkRateLimit(origin);
if (rateLimitMessage) {
res.writeHead(429, 'Too Many Requests', cors_headers);
res.end('The origin "' + origin + '" has sent too many requests.\n' + rateLimitMessage);
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;
req.corsAnywhereRequestState.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
secure: process.env.NODE_TLS_REJECT_UNAUTHORIZED !== '0',
};
// Allow user to override defaults and add own options
if (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;
if (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.
// Prior to Node 13.x, the stream would have ended.
// As of Node 13.x, we must explicitly close it.
if (res.writableEnded === false) {
res.end();
}
return;
}
// When the error occurs after setting headers but before writing the response,
// then any previously set headers must be removed.
var headerNames = res.getHeaderNames ? res.getHeaderNames() : Object.keys(res._headers || {});
headerNames.forEach(function(name) {
res.removeHeader(name);
});
res.writeHead(404, {'Access-Control-Allow-Origin': '*'});
res.end('Not found because of proxy error: ' + err);
});
return server;
};