From 073737c8acc51c4a9366ece74afd134e11c70d35 Mon Sep 17 00:00:00 2001
From: Pierre Ossman <ossman@cendio.se>
Date: Fri, 4 Sep 2020 16:16:44 +0200
Subject: [PATCH] Handle empty rects from the server

These are very pointless for the server to send, but not a violation of
the protocol so we need to be able to handle them. We've seen this
happen in real world scenarios a few times.
---
 kasmweb/core/decoders/copyrect.js |  5 +++
 kasmweb/core/decoders/tight.js    |  8 +++++
 kasmweb/tests/test.copyrect.js    | 17 ++++++++++
 kasmweb/tests/test.hextile.js     | 17 ++++++++++
 kasmweb/tests/test.raw.js         | 34 +++++++++++++++++++
 kasmweb/tests/test.rre.js         | 17 ++++++++++
 kasmweb/tests/test.tight.js       | 55 +++++++++++++++++++++++++++++++
 7 files changed, 153 insertions(+)

diff --git a/kasmweb/core/decoders/copyrect.js b/kasmweb/core/decoders/copyrect.js
index 0e0536a..9e6391a 100644
--- a/kasmweb/core/decoders/copyrect.js
+++ b/kasmweb/core/decoders/copyrect.js
@@ -15,6 +15,11 @@ export default class CopyRectDecoder {
 
         let deltaX = sock.rQshift16();
         let deltaY = sock.rQshift16();
+
+        if ((width === 0) || (height === 0)) {
+            return true;
+        }
+
         display.copyImage(deltaX, deltaY, x, y, width, height);
 
         return true;
diff --git a/kasmweb/core/decoders/tight.js b/kasmweb/core/decoders/tight.js
index be9f1cc..dfe90f2 100644
--- a/kasmweb/core/decoders/tight.js
+++ b/kasmweb/core/decoders/tight.js
@@ -162,6 +162,10 @@ export default class TightDecoder {
         const uncompressedSize = width * height * 3;
         let data;
 
+        if (uncompressedSize === 0) {
+            return true;
+        }
+
         if (uncompressedSize < 12) {
             if (sock.rQwait("TIGHT", uncompressedSize)) {
                 return false;
@@ -217,6 +221,10 @@ export default class TightDecoder {
 
         let data;
 
+        if (uncompressedSize === 0) {
+            return true;
+        }
+
         if (uncompressedSize < 12) {
             if (sock.rQwait("TIGHT", uncompressedSize)) {
                 return false;
diff --git a/kasmweb/tests/test.copyrect.js b/kasmweb/tests/test.copyrect.js
index fcf4219..afb778f 100644
--- a/kasmweb/tests/test.copyrect.js
+++ b/kasmweb/tests/test.copyrect.js
@@ -57,4 +57,21 @@ describe('CopyRect Decoder', function () {
 
         expect(display).to.have.displayed(targetData);
     });
+
+    it('should handle empty rects', function () {
+        display.fillRect(0, 0, 4, 4, [ 0x00, 0x00, 0xff ]);
+        display.fillRect(2, 0, 2, 2, [ 0x00, 0xff, 0x00 ]);
+        display.fillRect(0, 2, 2, 2, [ 0x00, 0xff, 0x00 ]);
+
+        testDecodeRect(decoder, 1, 2, 0, 0, [0x00, 0x00, 0x00, 0x00], display, 24);
+
+        let targetData = new Uint8Array([
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255
+        ]);
+
+        expect(display).to.have.displayed(targetData);
+    });
 });
diff --git a/kasmweb/tests/test.hextile.js b/kasmweb/tests/test.hextile.js
index 7c97527..bac415f 100644
--- a/kasmweb/tests/test.hextile.js
+++ b/kasmweb/tests/test.hextile.js
@@ -206,4 +206,21 @@ describe('Hextile Decoder', function () {
         let data = [45];  // an invalid subencoding
         expect(() => testDecodeRect(decoder, 0, 0, 4, 4, data, display, 24)).to.throw();
     });
+
+    it('should handle empty rects', function () {
+        display.fillRect(0, 0, 4, 4, [ 0x00, 0x00, 0xff ]);
+        display.fillRect(2, 0, 2, 2, [ 0x00, 0xff, 0x00 ]);
+        display.fillRect(0, 2, 2, 2, [ 0x00, 0xff, 0x00 ]);
+
+        testDecodeRect(decoder, 1, 2, 0, 0, [], display, 24);
+
+        let targetData = new Uint8Array([
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255
+        ]);
+
+        expect(display).to.have.displayed(targetData);
+    });
 });
diff --git a/kasmweb/tests/test.raw.js b/kasmweb/tests/test.raw.js
index b42e4f3..4830bbb 100644
--- a/kasmweb/tests/test.raw.js
+++ b/kasmweb/tests/test.raw.js
@@ -86,4 +86,38 @@ describe('Raw Decoder', function () {
 
         expect(display).to.have.displayed(targetData);
     });
+
+    it('should handle empty rects', function () {
+        display.fillRect(0, 0, 4, 4, [ 0x00, 0x00, 0xff ]);
+        display.fillRect(2, 0, 2, 2, [ 0x00, 0xff, 0x00 ]);
+        display.fillRect(0, 2, 2, 2, [ 0x00, 0xff, 0x00 ]);
+
+        testDecodeRect(decoder, 1, 2, 0, 0, [], display, 24);
+
+        let targetData = new Uint8Array([
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255
+        ]);
+
+        expect(display).to.have.displayed(targetData);
+    });
+
+    it('should handle empty rects in low colour mode', function () {
+        display.fillRect(0, 0, 4, 4, [ 0x00, 0x00, 0xff ]);
+        display.fillRect(2, 0, 2, 2, [ 0x00, 0xff, 0x00 ]);
+        display.fillRect(0, 2, 2, 2, [ 0x00, 0xff, 0x00 ]);
+
+        testDecodeRect(decoder, 1, 2, 0, 0, [], display, 8);
+
+        let targetData = new Uint8Array([
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255
+        ]);
+
+        expect(display).to.have.displayed(targetData);
+    });
 });
diff --git a/kasmweb/tests/test.rre.js b/kasmweb/tests/test.rre.js
index 78b5eaa..583cd5a 100644
--- a/kasmweb/tests/test.rre.js
+++ b/kasmweb/tests/test.rre.js
@@ -81,4 +81,21 @@ describe('RRE Decoder', function () {
 
         expect(display).to.have.displayed(targetData);
     });
+
+    it('should handle empty rects', function () {
+        display.fillRect(0, 0, 4, 4, [ 0x00, 0x00, 0xff ]);
+        display.fillRect(2, 0, 2, 2, [ 0x00, 0xff, 0x00 ]);
+        display.fillRect(0, 2, 2, 2, [ 0x00, 0xff, 0x00 ]);
+
+        testDecodeRect(decoder, 1, 2, 0, 0, [ 0x00, 0xff, 0xff, 0xff, 0xff ], display, 24);
+
+        let targetData = new Uint8Array([
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255
+        ]);
+
+        expect(display).to.have.displayed(targetData);
+    });
 });
diff --git a/kasmweb/tests/test.tight.js b/kasmweb/tests/test.tight.js
index 10ef971..d89cf57 100644
--- a/kasmweb/tests/test.tight.js
+++ b/kasmweb/tests/test.tight.js
@@ -210,6 +210,61 @@ describe('Tight Decoder', function () {
         // Not implemented yet
     });
 
+    it('should handle empty copy rects', function () {
+        display.fillRect(0, 0, 4, 4, [ 0x00, 0x00, 0xff ]);
+        display.fillRect(2, 0, 2, 2, [ 0x00, 0xff, 0x00 ]);
+        display.fillRect(0, 2, 2, 2, [ 0x00, 0xff, 0x00 ]);
+
+        testDecodeRect(decoder, 1, 2, 0, 0, [ 0x00 ], display, 24);
+
+        let targetData = new Uint8Array([
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255
+        ]);
+
+        expect(display).to.have.displayed(targetData);
+    });
+
+    it('should handle empty palette rects', function () {
+        display.fillRect(0, 0, 4, 4, [ 0x00, 0x00, 0xff ]);
+        display.fillRect(2, 0, 2, 2, [ 0x00, 0xff, 0x00 ]);
+        display.fillRect(0, 2, 2, 2, [ 0x00, 0xff, 0x00 ]);
+
+        testDecodeRect(decoder, 1, 2, 0, 0,
+                       [ 0x40, 0x01, 0x01,
+                         0xff, 0xff, 0xff,
+                         0xff, 0xff, 0xff ], display, 24);
+
+        let targetData = new Uint8Array([
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255
+        ]);
+
+        expect(display).to.have.displayed(targetData);
+    });
+
+    it('should handle empty fill rects', function () {
+        display.fillRect(0, 0, 4, 4, [ 0x00, 0x00, 0xff ]);
+        display.fillRect(2, 0, 2, 2, [ 0x00, 0xff, 0x00 ]);
+        display.fillRect(0, 2, 2, 2, [ 0x00, 0xff, 0x00 ]);
+
+        testDecodeRect(decoder, 1, 2, 0, 0,
+                       [ 0x80, 0xff, 0xff, 0xff ], display, 24);
+
+        let targetData = new Uint8Array([
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255, 0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255,
+            0x00, 0xff, 0x00, 255, 0x00, 0xff, 0x00, 255, 0x00, 0x00, 0xff, 255, 0x00, 0x00, 0xff, 255
+        ]);
+
+        expect(display).to.have.displayed(targetData);
+    });
+
     it('should handle JPEG rects', function (done) {
         let data = [
             // Control bytes