Implement ClearKey message format as JSON.

media/cdm/json_web_key.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_CDM_JSON_WEB_KEY_H_
 #define MEDIA_CDM_JSON_WEB_KEY_H_
 
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "media/base/media_export.h"
+#include "media/base/media_keys.h"
 
 namespace media {
 
+// The ClearKey license request format is a JSON object containing the
+// following members:

[xhwang, 2014/07/30 05:56:07]

provide ref to the eme spec

[jrummell, 2014/07/30 18:44:15]

Done.

+//   "kids" : An array of key IDs. Each element of the array is the base64url
+//            encoding of the octet sequence containing the key ID value.
+//   "type" : The requested SessionType.
+// An example:
+//   { "kids":["67ef0gd8pvfd0","77ef0gd8pvfd0"], "type":"temporary" }
+
+// The ClearKey license format is a JSON Web Key (JWK) Set containing
+// representation of the symmetric key to be used for decryption.
+// For each JWK in the set, the parameter values are as follows:
+//   "kty" (key type)  : "oct" (octet sequence)
+//   "alg" (algorithm) : "A128KW" (AES key wrap using a 128-bit key)
+//   "k" (key value)   : The base64url encoding of the octet sequence
+//                       containing the symmetric key value.
+//   "kid" (key ID)    : The base64url encoding of the octet sequence
+//                       containing the key ID value.
+// The JSON object may have an optional "type" member value, which may be
+// any of the SessionType values. If not specified, the default value of
+// "temporary" is used.
 // A JSON Web Key Set looks like the following in JSON:
-//   { "keys": [ JWK1, JWK2, ... ] }
+//   { "keys": [ JWK1, JWK2, ... ], "type":"temporary" }
 // A symmetric keys JWK looks like the following in JSON:
 //   { "kty":"oct",
+//     "alg":"A128KW",
 //     "kid":"AQIDBAUGBwgJCgsMDQ4PEA",
 //     "k":"FBUWFxgZGhscHR4fICEiIw" }
+
 // There may be other properties specified, but they are ignored.
 // Ref: http://tools.ietf.org/html/draft-ietf-jose-json-web-key and:
 // http://tools.ietf.org/html/draft-jones-jose-json-private-and-symmetric-key
-//
-// For EME WD, both 'kid' and 'k' are base64 encoded strings, without trailing
-// padding.
 
 // Vector of [key_id, key_value] pairs. Values are raw binary data, stored in
 // strings for convenience.
 typedef std::pair<std::string, std::string> KeyIdAndKeyPair;
 typedef std::vector<KeyIdAndKeyPair> KeyIdAndKeyPairs;
 
 // Converts a single |key|, |key_id| pair to a JSON Web Key Set.
 MEDIA_EXPORT std::string GenerateJWKSet(const uint8* key, int key_length,
                                         const uint8* key_id, int key_id_length);
 
 // Extracts the JSON Web Keys from a JSON Web Key Set. If |input| looks like
-// a valid JWK Set, then true is returned and |keys| is updated to contain
-// the list of keys found. Otherwise return false.
+// a valid JWK Set, then true is returned and |keys| and |session_type| are
+// updated to contain the values found. Otherwise return false.
 MEDIA_EXPORT bool ExtractKeysFromJWKSet(const std::string& jwk_set,
-                                        KeyIdAndKeyPairs* keys);
+                                        KeyIdAndKeyPairs* keys,
+                                        MediaKeys::SessionType* session_type);
+
+// Create a license request message for the |key_id| and |session_type|
+// specified. Currently ClearKey generates a message for each key individually,
+// so no need to take a list of |key_id|'s. |result| is updated to contain the
+// resulting JSON string.
+MEDIA_EXPORT void CreateLicenseRequest(const uint8* key_id,
+                                       int key_id_length,
+                                       MediaKeys::SessionType session_type,
+                                       std::vector<uint8>& result);

[xhwang, 2014/07/30 05:56:07]

We prefer to using pointer for output parameters:

http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Refere...

[jrummell, 2014/07/30 18:44:15]

Done.

+
+// Extract the first key from the license request message.

[xhwang, 2014/07/30 05:56:07]

From the documentation on l.18-24, a license request message contains info about
key IDs and the type. So what do you mean by "the first key from the license
request message"? From the implementation, it seems that we are extracting the
first key ID in the "kids". If so, how about renaming this to something like
ExtractFirstKeyIdFromLicenseRequest?

[jrummell, 2014/07/30 18:44:15]

Done.

+MEDIA_EXPORT bool ExtractLicenseKey(const std::vector<uint8>& message,

[xhwang, 2014/07/30 05:56:07]

what is the return value?

[jrummell, 2014/07/30 18:44:15]

Done.

+                                    std::vector<uint8>& first_key);

[xhwang, 2014/07/30 05:56:07]

ditto about passing pointer instead of ref

[jrummell, 2014/07/30 18:44:15]

Done.

 
 }  // namespace media
 
 #endif  // MEDIA_CDM_JSON_WEB_KEY_H_