Fix PlayReady challenge format (#3120)

* KeySystemPlayReady: set utf-8 format by default for challenge request (if not set in PlayReadyKeyMessage)

* update unit test

src/streaming/protection/drm/KeySystemPlayReady.js

@@ -72,16 +72,17 @@ function KeySystemPlayReady(config) {
         for (let i = 0; i < headerNameList.length; i++) {
             headers[headerNameList[i].childNodes[0].nodeValue] = headerValueList[i].childNodes[0].nodeValue;
         }
-        // some versions of the PlayReady CDM return 'Content' instead of 'Content-Type'.
+        // Some versions of the PlayReady CDM return 'Content' instead of 'Content-Type'.
         // this is NOT w3c conform and license servers may reject the request!
         // -> rename it to proper w3c definition!
         if (headers.hasOwnProperty('Content')) {
             headers['Content-Type'] = headers.Content;
             delete headers.Content;
         }
-        // some devices (Ex: LG SmartTVs) require content-type to be defined
+        // Set Content-Type header by default if not provided in the the CDM message (<PlayReadyKeyMessage/>)
+        // or if the message contains directly the challenge itself (Ex: LG SmartTVs)
         if (!headers.hasOwnProperty('Content-Type')) {
-            headers['Content-Type'] = 'text/xml; charset=' + messageFormat;
+            headers['Content-Type'] = 'text/xml; charset=utf-8';
         }
         return headers;
     }
@@ -101,6 +102,9 @@ function KeySystemPlayReady(config) {
                 licenseRequest = BASE64.decode(Challenge);
             }
         } else {
+            // The message from CDM is not a wrapped message as on IE11 and Edge,
+            // thus it contains direclty the challenge itself
+            // (note that the xmlDoc at this point may be unreadable since it may have been interpreted as UTF-16)
             return message;
         }
 
@@ -309,4 +313,4 @@ function KeySystemPlayReady(config) {
 }
 
 KeySystemPlayReady.__dashjs_factory_name = 'KeySystemPlayReady';
-export default dashjs.FactoryMaker.getSingletonFactory(KeySystemPlayReady); /* jshint ignore:line */
+export default dashjs.FactoryMaker.getSingletonFactory(KeySystemPlayReady); /* jshint ignore:line */

test/unit/streaming.protection.drm.KeySystemPlayReady.js

@@ -96,9 +96,9 @@ describe('KeySystemPlayready', function () {
             expect(licenseRequest).to.be.undefined;   // jshint ignore:line
         });
 
-        it('should return null when getRequestHeadersFromMessage is called without parameter', function () {
+        it('should return at least Content-Type header when getRequestHeadersFromMessage is called without parameter', function () {
             const requestHeaders = keySystem.getRequestHeadersFromMessage();
-            expect(requestHeaders['Content-Type']).to.equal('text/xml; charset=utf-16');
+            expect(requestHeaders['Content-Type']).to.equal('text/xml; charset=utf-8');
         });
 
         it('should return the correct cdmData', function () {
@@ -111,4 +111,4 @@ describe('KeySystemPlayready', function () {
             expect(cdmDataString).to.equal(expectedCDMData);
         });
     });
-});
+});