add emsg validation and malformed box test

videojs · Feb 9, 2023 · e786dc1 · e786dc1
1 parent 54d9645
commit e786dc1
Show file tree

Hide file tree

Showing 3 changed files with 64 additions and 18 deletions.
diff --git a/lib/mp4/emsg.js b/lib/mp4/emsg.js
@@ -15,11 +15,13 @@ var parseEmsgBox = function(boxData) {
   var offset = 4;
   var version = boxData[0];
   var scheme_id_uri, 
-    value, timescale, 
+    value, 
+    timescale, 
     presentation_time, 
     presentation_time_delta, 
     event_duration, 
-    id;
+    id,
+    message_data;
   if (version === 0) {
     scheme_id_uri = uint8ToCString(boxData.subarray(offset));
     offset += scheme_id_uri.length;
@@ -48,26 +50,54 @@ var parseEmsgBox = function(boxData) {
     offset += scheme_id_uri.length;
     value = uint8ToCString(boxData.subarray(offset));
     offset += value.length;        
-  } else {
-    // Invalid EMSG box.
-    return;
   }
 
-  var message_data = new Uint8Array(boxData.subarray(offset, boxData.byteLength));
-  return { scheme_id_uri, 
-          value, 
-          timescale, 
-          presentation_time, 
-          presentation_time_delta, 
-          event_duration, 
-          id, 
-          message_data };
+  message_data = new Uint8Array(boxData.subarray(offset, boxData.byteLength));
+  var emsgBox = {
+    scheme_id_uri, 
+    value,
+    // if timescale is undefined or 0 set to 1 
+    timescale: timescale ? timescale : 1, 
+    presentation_time, 
+    presentation_time_delta, 
+    event_duration, 
+    id,
+    message_data };
+
+  return isValidEmsgBox(version, emsgBox) ? emsgBox : undefined;
 };
 
+/**
+ * Scales a presentation time or time delta with an offset with a provided timescale
+ * @param {number} presentationTime 
+ * @param {number} timescale 
+ * @param {number} timeDelta 
+ * @param {number} offset 
+ * @returns the scaled time as a number
+ */
 var scaleTime = function(presentationTime, timescale, timeDelta, offset) {
   return presentationTime || presentationTime === 0 ? presentationTime / timescale : offset + timeDelta / timescale;
 };
 
+/**
+ * Checks the emsg box data for validity based on the version
+ * @param {number} version of the emsg box to validate
+ * @param {Object} emsg the emsg data to validate
+ * @returns if the box is valid as a boolean
+ */
+var isValidEmsgBox = function(version, emsg) {
+  var hasScheme = emsg.scheme_id_uri !== '\0'
+  var isValidV0Box = version === 0 && isDefined(emsg.presentation_time_delta) && hasScheme;
+  var isValidV1Box = version === 1 && isDefined(emsg.presentation_time) && hasScheme;
+  // Only valid versions of emsg are 0 and 1
+  return !(version > 1) && isValidV0Box || isValidV1Box;
+};
+
+// Utility function to check if an object is defined
+var isDefined = function(data) {
+  return data !== undefined || data !== null;
+};
+
 module.exports = { 
   parseEmsgBox: parseEmsgBox, 
   scaleTime: scaleTime

diff --git a/test/mp4-emsg.test.js b/test/mp4-emsg.test.js
@@ -36,8 +36,14 @@ QUnit.test('Can parse a v1 emsg box', function(assert) {
   assert.deepEqual(parsedBox.message_data, messageData, 'v1 box has expected data');
 });
 
-QUnit.test('Will return undefined if the emsg box is invalid', function(assert) {
-  var badBoxData = generateEmsgBoxData(3, messageData);
+QUnit.test('Will return undefined if the emsg version is invalid', function(assert) {
+  var badBoxData = generateEmsgBoxData(2, messageData);
   var parsedBox = emsg.parseEmsgBox(badBoxData);
   assert.equal(parsedBox, undefined, 'parsed box is undefined');
 });
+
+QUnit.test('Will return undefined if the emsg data is malformed', function(assert) {
+  var badBoxData = generateEmsgBoxData(3, messageData);
+  var parsedBox = emsg.parseEmsgBox(badBoxData);
+  assert.equal(parsedBox, undefined, 'malformed box is undefined');
+});
diff --git a/test/utils/mp4-helpers.js b/test/utils/mp4-helpers.js
@@ -340,8 +340,8 @@ var generateEmsgBoxData = function(version, messageData) {
       0x75, 0x72, 0x6E, 0x3A, 0x66, 0x6F, 0x6F, 0x3A, 0x62, 0x61, 0x72, 0x3A, 0x32, 0x30, 0x32, 0x33, 0x00, // urn:foo:bar:2023\0
       0x66, 0x6F, 0x6F, 0x2E, 0x62, 0x61, 0x72, 0x2E, 0x76, 0x61, 0x6C, 0x75, 0x65, 0x00 // foo.bar.value\0
     ]);
-  } else {
-    // Invalid EMSG box
+  } else if (version === 2) {
+    // Invalid version only
     emsgProps = new Uint8Array([
       0x02, // version
       0x00, 0x00, 0x00, //flags
@@ -352,6 +352,16 @@ var generateEmsgBoxData = function(version, messageData) {
       0x75, 0x72, 0x6E, 0x3A, 0x66, 0x6F, 0x6F, 0x3A, 0x62, 0x61, 0x72, 0x3A, 0x32, 0x30, 0x32, 0x33, 0x00, // urn:foo:bar:2023\0
       0x66, 0x6F, 0x6F, 0x2E, 0x62, 0x61, 0x72, 0x2E, 0x76, 0x61, 0x6C, 0x75, 0x65, 0x00 // foo.bar.value\0
     ]);
+  } else {
+    emsgProps = new Uint8Array([
+      // malformed emsg data
+      0x00, 0x00, 0x00, 0x64, // timescale = 100
+      // no presentation_time
+      0x00, 0x00, 0x00, 0x01, // event_duration = 1
+      // no id
+      0x75, 0x72, 0x6E, 0x3A, 0x66, 0x6F, 0x6F, 0x3A, 0x62, 0x61, 0x72, 0x3A, 0x32, 0x30, 0x32, 0x33, 0x00, // urn:foo:bar:2023\0
+      0x66, 0x6F, 0x6F, 0x2E, 0x62, 0x61, 0x72, 0x2E, 0x76, 0x61, 0x6C, 0x75, 0x65, 0x00 // foo.bar.value\0
+    ]);
   }
 
   // concat the props and messageData