storage: download integrity check

Author: stephenplusplus

lib/storage/file.js

@@ -24,6 +24,7 @@ var crypto = require('crypto');
 var duplexify = require('duplexify');
 var request = require('request');
 var streamEvents = require('stream-events');
+var through = require('through2');
 
 /**
  * @type module:common/util
@@ -172,7 +173,6 @@ File.prototype.copy = function(destination, callback) {
   });
 };
 
-
 /**
  * Create a readable stream to read the contents of the remote file. It can be
  * piped to a writable stream or listened to for 'data' events to read a file's
@@ -194,34 +194,67 @@ File.prototype.copy = function(destination, callback) {
  *   .on('error', function(err) {});
  */
 File.prototype.createReadStream = function() {
-  var storage = this.bucket.storage;
-  var dup = duplexify();
+  var that = this;
+  var throughStream = through();
+
+  this.getMetadata(function(err, metadata) {
+    if (err) {
+      throughStream.emit('error', err);
+      throughStream.end();
+      return;
+    }
+
+    createAuthorizedReq(metadata.mediaLink);
+  });
+
+  return throughStream;
+
+  // Authenticate the request, then pipe the remote API request to the stream
+  // returned to the user.
   function createAuthorizedReq(uri) {
-    var reqOpts = { uri: uri };
-    storage.makeAuthorizedRequest_(reqOpts, {
+    var reqOpts = {
+      uri: uri
+    };
+
+    that.bucket.storage.makeAuthorizedRequest_(reqOpts, {
       onAuthorized: function(err, authorizedReqOpts) {
         if (err) {
-          dup.emit('error', err);
-          dup.end();
+          throughStream.emit('error', err);
+          throughStream.end();
           return;
         }
-        dup.setReadable(request(authorizedReqOpts));
-      }
-    });
-  }
-  if (this.metadata.mediaLink) {
-    createAuthorizedReq(this.metadata.mediaLink);
-  } else {
-    this.getMetadata(function(err, metadata) {
-      if (err) {
-        dup.emit('error', err);
-        dup.end();
-        return;
+
+        // For data integrity, hash the contents of the stream as we receive it
+        // from the server.
+        var localMd5Hash = crypto.createHash('md5');
+
+        request(authorizedReqOpts)
+          .on('data', function(chunk) {
+            localMd5Hash.update(chunk);
+          })
+
+          .on('complete', function() {
+            localMd5Hash = localMd5Hash.digest('base64');
+
+            if (that.metadata.md5Hash === localMd5Hash) {
+              throughStream.emit('complete');
+            } else {
+              var error = new Error([
+                'The downloaded data did not match the data from the server. ',
+                'To be sure the content is the same, you should download the',
+                'file again.'
+              ].join(''));
+
+              throughStream.emit('error', error);
+            }
+
+            throughStream.end();
+          })
+
+          .pipe(throughStream);
       }
-      createAuthorizedReq(metadata.mediaLink);
     });
   }
-  return dup;
 };
 
 /**

regression/storage.js

@@ -142,7 +142,7 @@ describe('storage', function() {
       });
     });
 
-    it('should read/write from/to a file in a directory', function(done) {
+    it.only('should read/write from/to a file in a directory', function(done) {
       var file = bucket.file('directory/file');
       var contents = 'test';
 
@@ -152,12 +152,17 @@ describe('storage', function() {
 
       writeStream.on('error', done);
       writeStream.on('complete', function() {
+        var data = new Buffer('');
+
         file.createReadStream()
+          .on('error', done)
           .on('data', function(chunk) {
-            assert.equal(String(chunk), contents);
+            data = Buffer.concat([data, chunk]);
           })
-          .on('error', done)
-          .on('end', done);
+          .on('complete', function() {
+            assert.equal(data.toString(), contents);
+            done();
+          });
       });
     });
 

test/storage/file.js

@@ -24,6 +24,7 @@ var duplexify = require('duplexify');
 var extend = require('extend');
 var nodeutil = require('util');
 var request = require('request');
+var stream = require('stream');
 var url = require('url');
 var util = require('../../lib/common/util');
 
@@ -243,13 +244,15 @@ describe('File', function() {
     });
 
     it('should create an authorized request', function(done) {
-      request_Override = function(opts) {
+      file.bucket.storage.makeAuthorizedRequest_ = function(opts) {
         assert.equal(opts.uri, metadata.mediaLink);
         done();
       };
+
       file.getMetadata = function(callback) {
         callback(null, metadata);
       };
+
       file.createReadStream();
     });
 
@@ -272,33 +275,32 @@ describe('File', function() {
 
     it('should get readable stream from request', function(done) {
       var fakeRequest = { a: 'b', c: 'd' };
-      file.getMetadata = function(callback) {
-        callback(null, metadata);
-      };
+
+      // Faking a stream implementation so we can simulate an actual Request
+      // request. The only thing we want to know is if the data passed to
+      // request was correct.
       request_Override = function(req) {
+        if (!(this instanceof request_Override)) {
+          return new request_Override(req);
+        }
+
+        stream.Readable.call(this);
+        this._read = util.noop;
+
         assert.deepEqual(req, fakeRequest);
         done();
       };
-      file.bucket.storage.makeAuthorizedRequest_ = function(opts, callback) {
-        (callback.onAuthorized || callback)(null, fakeRequest);
-      };
-      file.createReadStream();
-    });
+      nodeutil.inherits(request_Override, stream.Readable);
 
-    it('should set readable stream', function() {
-      var dup = duplexify();
       file.getMetadata = function(callback) {
         callback(null, metadata);
       };
-      request_Override = function() {
-        return dup;
-      };
+
       file.bucket.storage.makeAuthorizedRequest_ = function(opts, callback) {
-        (callback.onAuthorized || callback)();
+        (callback.onAuthorized || callback)(null, fakeRequest);
       };
+
       file.createReadStream();
-      assert.deepEqual(readableStream, dup);
-      readableStream = null;
     });
   });