feat(dash): [ClearKey] Construct pssh box based on ContentProtection …

…content in the mpd.
shaka-project · Apr 8, 2022 · 4b66e2c · 4b66e2c
1 parent 57c7324
commit 4b66e2c
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Showing 2 changed files with 93 additions and 3 deletions.
diff --git a/lib/dash/content_protection.js b/lib/dash/content_protection.js
@@ -68,7 +68,7 @@ shaka.dash.ContentProtection = class {
 
       if (parsedNonCenc.length) {
         drmInfos = ContentProtection.convertElements_(
-            defaultInit, parsedNonCenc, keySystemsByURI);
+            defaultInit, parsedNonCenc, keySystemsByURI, keyIds);
 
         // If there are no drmInfos after parsing, then add a dummy entry.
         // This may be removed in parseKeyIds.
@@ -366,16 +366,48 @@ shaka.dash.ContentProtection = class {
     ];
   }
 
+  /**
+   * Creates ClearKey initData from Default_KID value.
+   * @param {shaka.dash.ContentProtection.Element} element
+   * @param {!Set.<string>} keyIds
+   * @return {?Array.<shaka.extern.InitDataOverride>}
+   * @private
+   */
+  static getInitDataClearKey_(element, keyIds) {
+    if (keyIds.size == 0) {
+      return null;
+    }
+
+    const Uint8ArrayUtils = shaka.util.Uint8ArrayUtils;
+    const [first] = keyIds;
+    const data = Uint8ArrayUtils.fromHex(first);
+
+    const systemId = new Uint8Array([
+      0x10, 0x77, 0xef, 0xec, 0xc0, 0xb2, 0x4d, 0x02,
+      0xac, 0xe3, 0x3c, 0x1e, 0x52, 0xe2, 0xfb, 0x4b,
+    ]);
+
+    const pssh = shaka.util.Pssh.createPsshClearKey(data, systemId);
+    return [
+      {
+        initData: pssh,
+        initDataType: 'cenc',
+        keyId: element.keyId,
+      },
+    ];
+  }
+
   /**
    * Creates DrmInfo objects from the given element.
    *
    * @param {Array.<shaka.extern.InitDataOverride>} defaultInit
    * @param {!Array.<shaka.dash.ContentProtection.Element>} elements
    * @param {!Object.<string, string>} keySystemsByURI
+   * @param {!Set.<string>} keyIds
    * @return {!Array.<shaka.extern.DrmInfo>}
    * @private
    */
-  static convertElements_(defaultInit, elements, keySystemsByURI) {
+  static convertElements_(defaultInit, elements, keySystemsByURI, keyIds) {
     const ContentProtection = shaka.dash.ContentProtection;
     const ManifestParserUtils = shaka.util.ManifestParserUtils;
     const licenseUrlParsers = ContentProtection.licenseUrlParsers_;
@@ -391,7 +423,14 @@ shaka.dash.ContentProtection = class {
             'Init data must be null or non-empty.');
 
         const proInitData = ContentProtection.getInitDataFromPro_(element);
-        const initData = element.init || defaultInit || proInitData;
+        let clearKeyInitData = null;
+        if (element.schemeUri ===
+              shaka.dash.ContentProtection.ClearKeySchemeUri_) {
+          clearKeyInitData =
+            ContentProtection.getInitDataClearKey_(element, keyIds);
+        }
+        const initData = element.init || defaultInit || proInitData ||
+          clearKeyInitData;
         const info = ManifestParserUtils.createDrmInfo(keySystem, initData);
         const licenseParser = licenseUrlParsers.get(keySystem);
         if (licenseParser) {
@@ -607,3 +646,11 @@ shaka.dash.ContentProtection.CencNamespaceUri_ = 'urn:mpeg:cenc:2013';
  */
 shaka.dash.ContentProtection.ClearKeyNamespaceUri_ =
   'http://dashif.org/guidelines/clearKey';
+
+
+/**
+ * @const {string}
+ * @private
+ */
+shaka.dash.ContentProtection.ClearKeySchemeUri_ =
+    'urn:uuid:e2719d58-a985-b3c9-781a-b030af78d30e';
diff --git a/lib/util/pssh.js b/lib/util/pssh.js
@@ -124,6 +124,49 @@ shaka.util.Pssh = class {
     return psshBox;
   }
 
+  /**
+   * Creates a ClearKey cenc pssh blob from the given system ID and data.
+   * Data will contain one key id.
+   * Based on https://www.w3.org/TR/eme-initdata-cenc/
+   * @param {!Uint8Array} data
+   * @param {!Uint8Array} systemId
+   * @return {!Uint8Array}
+   */
+  static createPsshClearKey(data, systemId) {
+    goog.asserts.assert(systemId.byteLength == 16, 'Invalid system ID length');
+    const dataLength = data.length;
+    const psshSize = 0x4 +              // pssh size (4 bytes)
+                     0x4 +              // 'pssh' (4 bytes)
+                     0x4 +              // version (1 byte) + flags (3 bytes)
+                     systemId.length +  // system id (16 bytes)
+                     0x4 +              // KID count (4 bytes)
+                     dataLength +       // KID value (16 bytes)
+                     0x4;               // size of data (4 bytes)
+
+    /** @type {!Uint8Array} */
+    const psshBox = new Uint8Array(psshSize);
+    /** @type {!DataView} */
+    const psshData = shaka.util.BufferUtils.toDataView(psshBox);
+
+    let byteCursor = 0;
+    psshData.setUint32(byteCursor, psshSize);
+    byteCursor += 0x4;
+    psshData.setUint32(byteCursor, 0x70737368);  // 'pssh'
+    byteCursor += 0x4;
+    psshData.setUint32(byteCursor, 0x01000000);  // version = 1
+    byteCursor += 0x4;
+    psshBox.set(systemId, byteCursor);
+    byteCursor += systemId.length;
+    psshData.setUint32(byteCursor, 0x00000001); // KID_count
+    byteCursor += 0x4;
+    psshBox.set(data, byteCursor); // add kid
+    byteCursor += dataLength;
+    psshData.setUint32(byteCursor, 0x00000000);
+    byteCursor += 0x4;
+
+    goog.asserts.assert(byteCursor === psshSize, 'PSSH invalid length.');
+    return psshBox;
+  }
 
   /**
    * Normalise the initData array. This is to apply browser specific