Implement HKDF for WebCrypto (blink-side)

Source/bindings/modules/v8/ScriptValueSerializerForModules.cpp

Index: Source/bindings/modules/v8/ScriptValueSerializerForModules.cpp
diff --git a/Source/bindings/modules/v8/ScriptValueSerializerForModules.cpp b/Source/bindings/modules/v8/ScriptValueSerializerForModules.cpp
index 08add9b64a162f1c2349c1a1f0b7f4b41428265f..c2432bce179f24c9c4ded5c230e1a7137fe0bdf3 100644
--- a/Source/bindings/modules/v8/ScriptValueSerializerForModules.cpp
+++ b/Source/bindings/modules/v8/ScriptValueSerializerForModules.cpp
@@ -30,6 +30,7 @@ enum CryptoKeyAlgorithmTag {
     RsaPssTag = 13,
     EcdsaTag = 14,
     EcdhTag = 15,
+    HkdfTag = 16,
     // Maximum allowed value is 2^32-1
 };
 
@@ -61,6 +62,7 @@ enum CryptoKeySubTag {
     // ID 3 was used by RsaKeyTag, while still behind experimental flag.
     RsaHashedKeyTag = 4,
     EcKeyTag = 5,
+    KdfKeyTag = 6,
     // Maximum allowed value is 255
 };
 
@@ -122,8 +124,8 @@ bool SerializedScriptValueWriterForModules::writeCryptoKey(const WebCryptoKey& k
         doWriteEcKey(key);
         break;
     case WebCryptoKeyAlgorithmParamsTypeNone:
-        ASSERT_NOT_REACHED();
-        return false;
+        ASSERT(WebCryptoAlgorithm::isKdf(key.algorithm().id()));
+        doWriteKdfKey(key);

[eroman, 2015/01/09 03:07:29]

Given the switch statement on params type, I think a better naming is to call
these "key without params" or some such thing, rather than KdfKey.

How about:

  doWriteKeyWithoutParams(key)

I suggest this because an understanding of the KDF class of algorithms and what
params they do and don't have is a more fuzzy concept in my opinion. Whereas a
key without any params is something readers immediately get. (The crypto
knowledge as much as possible is kept out of Blink).

[nharper, 2015/01/09 04:45:52]

I think this is reasonable, but the changes needed would be in more than just
this file (otherwise we're just pushing this inconsistency around the
serialization/deserialization code here). Specifically, it would be changing
WebCryptoKeyAlgorithm::createKdf() to be WebCryptoKeyAlgorithm::create() (or
create an explicit 1-arg constructor for WebCryptoKeyAlgorithm), and have it not
care about what type of algorithm it is, just that it's an algorithm with no
params. WebCryptoAlgorithm::isKdf() would also want to be changed to something
like WebCryptoAlgorithm::hasNoParams(WebCryptoAlgorithmId id).

Should I go ahead and make those changes (I don't know if I'll run into more
changes that will need to be made, but I think it will make it all consistent),
or should I leave it as is?

[nharper, 2015/01/09 21:21:09]

We discussed this, and I've changed it.

     }
 
     doWriteKeyUsages(key.usages(), key.extractable());
@@ -184,6 +186,13 @@ void SerializedScriptValueWriterForModules::doWriteEcKey(const WebCryptoKey& key
     doWriteNamedCurve(key.algorithm().ecParams()->namedCurve());
 }
 
+void SerializedScriptValueWriterForModules::doWriteKdfKey(const WebCryptoKey& key)
+{
+    append(static_cast<uint8_t>(KdfKeyTag));
+
+    doWriteAlgorithmId(key.algorithm().id());
+}
+
 void SerializedScriptValueWriterForModules::doWriteAlgorithmId(WebCryptoAlgorithmId id)
 {
     switch (id) {
@@ -215,6 +224,8 @@ void SerializedScriptValueWriterForModules::doWriteAlgorithmId(WebCryptoAlgorith
         return doWriteUint32(EcdsaTag);
     case WebCryptoAlgorithmIdEcdh:
         return doWriteUint32(EcdhTag);
+    case WebCryptoAlgorithmIdHkdf:
+        return doWriteUint32(HkdfTag);
     }
     ASSERT_NOT_REACHED();
 }
@@ -359,6 +370,10 @@ bool SerializedScriptValueReaderForModules::readCryptoKey(v8::Handle<v8::Value>*
         if (!doReadEcKey(algorithm, type))
             return false;
         break;
+    case KdfKeyTag:
+        if (!doReadKdfKey(algorithm, type))
+            return false;
+        break;
     default:
         return false;
     }
@@ -458,6 +473,16 @@ bool SerializedScriptValueReaderForModules::doReadEcKey(WebCryptoKeyAlgorithm& a
     return !algorithm.isNull();
 }
 
+bool SerializedScriptValueReaderForModules::doReadKdfKey(WebCryptoKeyAlgorithm& algorithm, WebCryptoKeyType& type)
+{
+    WebCryptoAlgorithmId kdf;
+    if (!doReadAlgorithmId(kdf))
+        return false;
+    algorithm = WebCryptoKeyAlgorithm::createKdf(kdf);
+    type = WebCryptoKeyTypeSecret;
+    return !algorithm.isNull();
+}
+
 bool SerializedScriptValueReaderForModules::doReadAlgorithmId(WebCryptoAlgorithmId& id)
 {
     uint32_t rawId;
@@ -507,6 +532,9 @@ bool SerializedScriptValueReaderForModules::doReadAlgorithmId(WebCryptoAlgorithm
     case EcdhTag:
         id = WebCryptoAlgorithmIdEcdh;
         return true;
+    case HkdfTag:
+        id = WebCryptoAlgorithmIdHkdf;
+        return true;
     }
 
     return false;