[fix] Count empty fragments toward the limit (#2329)

Ensure that empty fragments are counted against the `maxFragments`
limit.

Author: LeSingh1

lib/receiver.js

@@ -77,6 +77,7 @@ class Receiver extends Writable {
 
     this._totalPayloadLength = 0;
     this._messageLength = 0;
+    this._numFragments = 0;
     this._fragments = [];
 
     this._errored = false;
@@ -500,29 +501,26 @@ class Receiver extends Writable {
       return;
     }
 
+    if (this._maxFragments > 0 && ++this._numFragments > this._maxFragments) {
+      const error = this.createError(
+        RangeError,
+        'Too many message fragments',
+        false,
+        1008,
+        'WS_ERR_TOO_MANY_BUFFERED_PARTS'
+      );
+
+      cb(error);
+      return;
+    }
+
     if (this._compressed) {
       this._state = INFLATING;
       this.decompress(data, cb);
       return;
     }
 
     if (data.length) {
-      if (
-        this._maxFragments > 0 &&
-        this._fragments.length >= this._maxFragments
-      ) {
-        const error = this.createError(
-          RangeError,
-          'Too many message fragments',
-          false,
-          1008,
-          'WS_ERR_TOO_MANY_BUFFERED_PARTS'
-        );
-
-        cb(error);
-        return;
-      }
-
       //
       // This message is not compressed so its length is the sum of the payload
       // length of all fragments.
@@ -562,22 +560,6 @@ class Receiver extends Writable {
           return;
         }
 
-        if (
-          this._maxFragments > 0 &&
-          this._fragments.length >= this._maxFragments
-        ) {
-          const error = this.createError(
-            RangeError,
-            'Too many message fragments',
-            false,
-            1008,
-            'WS_ERR_TOO_MANY_BUFFERED_PARTS'
-          );
-
-          cb(error);
-          return;
-        }
-
         this._fragments.push(buf);
       }
 
@@ -604,6 +586,7 @@ class Receiver extends Writable {
     this._totalPayloadLength = 0;
     this._messageLength = 0;
     this._fragmented = 0;
+    this._numFragments = 0;
     this._fragments = [];
 
     if (this._opcode === 2) {

test/receiver.test.js

@@ -988,7 +988,7 @@ describe('Receiver', () => {
     });
   });
 
-  it('emits an error if there are too many message fragments (1/2)', (done) => {
+  it('emits an error if there are too many message fragments (1/3)', (done) => {
     const receiver = new Receiver({ maxFragments: 2 });
 
     receiver.on('error', (err) => {
@@ -1014,7 +1014,23 @@ describe('Receiver', () => {
     );
   });
 
-  it('emits an error if there are too many message fragments (2/2)', (done) => {
+  it('emits an error if there are too many message fragments (2/3)', (done) => {
+    const receiver = new Receiver({ maxFragments: 2 });
+
+    receiver.on('error', (err) => {
+      assert.ok(err instanceof RangeError);
+      assert.strictEqual(err.code, 'WS_ERR_TOO_MANY_BUFFERED_PARTS');
+      assert.strictEqual(err.message, 'Too many message fragments');
+      assert.strictEqual(err[kStatusCode], 1008);
+      done();
+    });
+
+    receiver.write(Buffer.from([0x02, 0x00]));
+    receiver.write(Buffer.from([0x00, 0x00]));
+    receiver.write(Buffer.from([0x00, 0x00]));
+  });
+
+  it('emits an error if there are too many message fragments (3/3)', (done) => {
     const perMessageDeflate = new PerMessageDeflate();
     perMessageDeflate.accept([{}]);