Brotli transparent support

.eslintrc

@@ -7,7 +7,9 @@
     "mocha": true,
   },
   "globals": {},
-  "parserOptions": { "ecmaVersion": 8 },
+  "parserOptions": {
+    "ecmaVersion": 8
+  },
   "rules": {
     "camelcase": [
       2,
@@ -21,8 +23,13 @@
       2,
       {
         "ArrayExpression": 1,
-        "CallExpression": {"arguments": 1},
-        "FunctionDeclaration": {"body": 1, "parameters": 2},
+        "CallExpression": {
+          "arguments": 1
+        },
+        "FunctionDeclaration": {
+          "body": 1,
+          "parameters": 2
+        },
         "MemberExpression": 1,
         "ObjectExpression": 1,
         "SwitchCase": 1
@@ -61,10 +68,13 @@
     "no-undef": 2,
     "no-unused-vars": 2,
     "no-eq-null": 2,
-    "space-before-function-paren": ["error", {
+    "space-before-function-paren": [
+      "error",
+      {
         "anonymous": "always",
         "named": "never"
-    }],
+      }
+    ],
     "no-empty": [
       2,
       {
@@ -150,7 +160,10 @@
     ],
     "lines-around-comment": [
       2,
-      { "afterLineComment": true, "allowBlockEnd": true }
+      {
+        "afterLineComment": false,
+        "allowBlockEnd": true
+      }
     ],
     "semi": [
       2,
@@ -165,4 +178,4 @@
       "unix"
     ]
   }
-}
+}

README.md

@@ -195,11 +195,12 @@ instance, but this is not a reliable interface. I expect to close this
 exploit in a future release, while providing an additional hook for mutating
 the userRes before sending.
 
-##### gzip responses
+##### gzip or Brotli responses
 
-If your proxy response is gzipped, this program will automatically unzip
-it before passing to your function, then zip it back up before piping it to the
-user response.  There is currently no way to short-circuit this behavior.
+If your proxy response is gzipped or Brotli-encoded, this program will
+automatically unzip it before passing to your function, then zip it back up
+before piping it to the user response. There is currently no way to
+short-circuit this behavior.
 
 #### limit
 

app/steps/decorateUserRes.js

@@ -3,31 +3,54 @@
 var as = require('../../lib/as.js');
 var debug = require('debug')('express-http-proxy');
 var zlib = require('zlib');
+var brotli = require('iltorb');
 
-function isResGzipped(res) {
-  return res.headers['content-encoding'] === 'gzip';
+var ENCODING = {
+  gzip: 'gzip',
+  brotli: 'br'
+};
+
+function isResEncoded(res, encoding) {
+  return res.headers['content-encoding'] === encoding;
 }
 
-function zipOrUnzip(method) {
-  return function(rspData, res) {
+const id = data => Promise.resolve(data);
+
+function createGzipHandler(method) {
+  return function (data) {
     return new Promise(function (resolve, reject) {
-      if (isResGzipped(res) && rspData.length) {
-        zlib[method](rspData, function(err, buffer) {
-          if(err) {
-            reject(err);
-          } else {
-            resolve(buffer);
-          }
-        });
-      } else {
-        resolve(rspData);
+      if (!data || !data.length) {
+        return resolve(data);
       }
+      zlib[method](data, function (err, buffer) {
+        if (err) {
+          reject(err);
+        } else {
+          resolve(buffer);
+        }
+      });
+
     });
   };
 }
 
-var maybeUnzipPromise = zipOrUnzip('gunzip');
-var maybeZipPromise = zipOrUnzip('gzip');
+function createEncodingHandler(res) {
+  if (isResEncoded(res, ENCODING.gzip)) {
+    return {
+      decode: createGzipHandler('gunzip'),
+      encode: createGzipHandler('gzip')
+    };
+  } else if (isResEncoded(res, ENCODING.brotli)) {
+    return {
+      decode: brotli.decompress,
+      encode: brotli.compress
+    };
+  }
+  return {
+    decode: id,
+    encode: id
+  };
+}
 
 function verifyBuffer(rspd, reject) {
   if (!Buffer.isBuffer(rspd)) {
@@ -37,11 +60,11 @@ function verifyBuffer(rspd, reject) {
 
 function updateHeaders(res, rspdBefore, rspdAfter, reject) {
   if (!res.headersSent) {
-      res.set('content-length', rspdAfter.length);
+    res.set('content-length', rspdAfter.length);
   } else if (rspdAfter.length !== rspdBefore.length) {
-      var error = '"Content-Length" is already sent,' +
-          'the length of response data can not be changed';
-      return reject(new Error(error));
+    var error = '"Content-Length" is already sent, ' +
+      'the length of response data can not be changed';
+    return reject(new Error(error));
   }
 }
 
@@ -52,31 +75,32 @@ function decorateProxyResBody(container) {
     return Promise.resolve(container);
   }
 
-  var proxyResDataPromise = maybeUnzipPromise(container.proxy.resData, container.proxy.res);
   var proxyRes = container.proxy.res;
   var req = container.user.req;
   var res = container.user.res;
-  var originalResData; 
+  var originalResData;
 
   if (res.statusCode === 304) {
     debug('Skipping userResDecorator on response 304');
     return Promise.resolve(container);
   }
 
-  return proxyResDataPromise
-    .then(function(proxyResData){
+  const encodingHandler = createEncodingHandler(container.proxy.res);
+
+  return encodingHandler.decode(container.proxy.resData)
+    .then(function (proxyResData) {
       originalResData = proxyResData;
       return resolverFn(proxyRes, proxyResData, req, res);
     })
-    .then(function(modifiedResData) {
-      return new Promise(function(resolve, reject) {
+    .then(function (modifiedResData) {
+      return new Promise(function (resolve, reject) {
         var rspd = as.buffer(modifiedResData, container.options);
         verifyBuffer(rspd, reject);
         updateHeaders(res, originalResData, rspd, reject);
-        maybeZipPromise(rspd, container.proxy.res).then(function(buffer) {
+        encodingHandler.encode(rspd).then(function (buffer) {
           container.proxy.resData = buffer;
           resolve(container);
-        }).catch(function(error){
+        }).catch(function (error) {
           reject(error);
         });
       });

lib/as.js

@@ -10,9 +10,9 @@ function asBuffer(body, options) {
   if (Buffer.isBuffer(body)) {
     ret = body;
   } else if (typeof body === 'object') {
-    ret = new Buffer(JSON.stringify(body), options.reqBodyEncoding);
+    ret = Buffer.from(JSON.stringify(body), options.reqBodyEncoding);
   } else if (typeof body === 'string') {
-    ret = new Buffer(body, options.reqBodyEncoding);
+    ret = Buffer.from(body, options.reqBodyEncoding);
   }
   return ret;
 }