Catch error due to invalid status code (#95)

lib/cors-anywhere.js

@@ -101,7 +101,18 @@ function proxyRequest(req, res, proxy) {
           }
           return proxyReqOn.call(this, 'response', function(proxyRes) {
             if (onProxyResponse(proxy, proxyReq, proxyRes, req, res)) {
-              listener(proxyRes);
+              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);
+              }
             }
           });
         };
@@ -400,6 +411,14 @@ exports.createServer = function createServer(options) {
       // the headers because it would generate an error.
       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);
   });

test/test.js

@@ -332,6 +332,28 @@ describe('Proxy errors', function() {
     });
   });
 
+  var bad_status_http_server;
+  var bad_status_http_server_url;
+  before(function() {
+    bad_status_http_server = require('net').createServer(function(socket) {
+      socket.setEncoding('utf-8');
+      socket.on('data', function(data) {
+        if (data.indexOf('\r\n') >= 0) {
+          // Assume end of headers.
+          socket.write('HTTP/1.0 0\r\n');
+          socket.write('Content-Length: 0\r\n');
+          socket.end('\r\n');
+        }
+      });
+    });
+    bad_status_http_server_url = 'http://127.0.0.1:' + bad_status_http_server.listen(0).address().port;
+  });
+  after(function(done) {
+    bad_status_http_server.close(function() {
+      done();
+    });
+  });
+
   var bad_tcp_server;
   var bad_tcp_server_url;
   before(function() {
@@ -369,6 +391,13 @@ describe('Proxy errors', function() {
       .expect(404, 'Not found because of proxy error: Error: Parse Error', done);
   });
 
+  it('Invalid HTTP status code', function(done) {
+    request(cors_anywhere)
+      .get('/' + bad_status_http_server_url)
+      .expect('Access-Control-Allow-Origin', '*')
+      .expect(404, 'Not found because of proxy error: RangeError: Invalid status code: 0', done);
+  });
+
   it('Content-Encoding invalid body', function(done) {
     // The HTTP status can't be changed because the headers have already been
     // sent.