Add support for Widevine ECM v3

Widevine ECM v3 is redesigned mainly based on protobuf, and supports new features including carrying fingerprinting and service blocking information. Existing clients must upgrade the Widevine CAS plugin to use the new ECM v3.

protos/public/media_cas.proto

@@ -50,3 +50,62 @@ message EmmPayload {
   repeated Fingerprinting fingerprinting = 1;
   repeated ServiceBlocking service_blocking = 2;
 }
+
+message EcmMetaData {
+  enum CipherMode {
+    UNSPECIFIED = 0;
+    AES_CBC = 1;
+    AES_CTR = 2;
+    DVB_CSA2 = 3;
+    DVB_CSA3 = 4;
+    AES_OFB = 5;
+    AES_SCTE52 = 6;
+  }
+  // Required. The cipher mode used to encrypt/decrypt the content.
+  optional CipherMode cipher_mode = 1;
+  // Optional. The minimum age required to watch the content. The value
+  // represents actual age, with 0 means no restriction.
+  optional uint32 age_restriction = 2 [default = 0];
+}
+
+message EcmKeyData {
+  // The wrapped content key data (aka control word).
+  // Required.
+  optional bytes wrapped_key_data = 1;
+  // The ID of the entitlement key used to wrap the content key. The secure key
+  // data associated with this ID is held by the license server. The client gets
+  // the key from the license server through a license request.
+  // Required for the even key data, optional for the odd key data if it is the
+  // same as the even key data.
+  optional bytes entitlement_key_id = 2;
+  // IV for decrypting the wrapped_key_data.
+  // Required for the even key data, optional for the odd key data if it is the
+  // same as the even key data.
+  optional bytes wrapped_key_iv = 3;
+  // IV for decrypting the content stream.
+  // Optional. If not specified in the even key data, 8 bytes 0x00 will be used;
+  // If not specified in the odd key data, the same content iv in the even key
+  // data will be used.
+  optional bytes content_iv = 4;
+}
+
+message EcmPayload {
+  // Required. Meta info carried by the ECM.
+  optional EcmMetaData meta_data = 1;
+  // Required. The key data for the even slot.
+  optional EcmKeyData even_key_data = 2;
+  // Optional. The key data for the odd slot if key rotation is enabled.
+  optional EcmKeyData odd_key_data = 3;
+  // Optional. Widevine fingerprinting information.
+  optional Fingerprinting fingerprinting = 4;
+  // Optional. Widevine service blocking information.
+  optional ServiceBlocking service_blocking = 5;
+}
+
+// The payload field for an ECM with signature.
+message SignedEcmPayload {
+  // Serialized EcmPayload.
+  optional bytes serialized_payload = 1;
+  // ECC (Elliptic Curve Cryptography) signature of |serialized_payload|.
+  optional bytes signature = 2;
+}