Implement HKDF for WebCrypto (blink-side)

Source/modules/crypto/NormalizeAlgorithm.cpp

Index: Source/modules/crypto/NormalizeAlgorithm.cpp
diff --git a/Source/modules/crypto/NormalizeAlgorithm.cpp b/Source/modules/crypto/NormalizeAlgorithm.cpp
index 823989554d1830bcbaa42b07280068057277d59b..91c7b66890cedbcdfca993e1035365ac52548893 100644
--- a/Source/modules/crypto/NormalizeAlgorithm.cpp
+++ b/Source/modules/crypto/NormalizeAlgorithm.cpp
@@ -67,6 +67,7 @@ struct AlgorithmNameMapping {
 // Also all names must be upper case ASCII.
 const AlgorithmNameMapping algorithmNameMappings[] = {
     {"HMAC", 4, WebCryptoAlgorithmIdHmac},
+    {"HKDF", 4, WebCryptoAlgorithmIdHkdf},
     {"ECDH", 4, WebCryptoAlgorithmIdEcdh},
     {"SHA-1", 5, WebCryptoAlgorithmIdSha1},
     {"ECDSA", 5, WebCryptoAlgorithmIdEcdsa},
@@ -773,6 +774,35 @@ bool parseAesDerivedKeyParams(const Dictionary& raw, OwnPtr<WebCryptoAlgorithmPa
     return true;
 }
 
+// The WebCrypto spec hasn't been updated yet to define HKDF. I am assuming a

[eroman, 2014/12/23 20:58:24]

Please add a FIXME or a link to a bug, so that there is an action-item somewhere
to update this comment (and possibly the implementation).

[nharper, 2014/12/23 22:46:59]

Done.

+// definition along the lines of:
+//
+//    dictionary HkdfParams : Algorithm {

[eroman, 2014/12/23 20:58:24]

How confident are you that this API will match the spec changes? (Taking stuff
back is problematic).

The bigger deal would be if the reflected key parameters changed, since those
can be persisted and requires backward support forever.

[nharper, 2014/12/23 22:46:59]

I'm not confident that this will match the spec. The names of the parameters
salt and info will most likely stay the same (as I pulled them from the RFC).
It's probably more likely that the salt will be optional instead of required.
There's a chance that info will be optional, although considering that label and
context were required for what the spec called "HKDF-CTR", info will probably be
required.

Assuming the names of the parameters stay the same, how much of a problem is it
if a parameter changes from required to optional?

[eroman, 2014/12/23 23:34:29]

Changing a required parameter from required -> optional is not a problem.
Going the other direction would be.

The rule of thumb, is we don't want web pages which previously worked, to
suddenly stop working. Relaxing the constraints is pretty much always safe,
however narrowing constraints will break consumers.

+//      required HashAlgorithmIdentifier hash;
+//      required BufferSource salt;
+//      required BufferSource info;
+//    };
+//
+// It is possible that salt will be changed to be optional.

[eroman, 2014/12/23 20:58:24]

nit: no need for this comment, already covered by above in my opinion.

[nharper, 2014/12/23 22:46:59]

Done.

+bool parseHkdfParams(const Dictionary& raw, OwnPtr<WebCryptoAlgorithmParams>& params, const ErrorContext& context, AlgorithmError* error)
+{
+    WebCryptoAlgorithm hash;
+    if (!parseHash(raw, hash, context, error))
+        return false;
+    BufferSource saltBufferSource;
+    if (!getBufferSource(raw, "salt", saltBufferSource, context, error))
+        return false;
+    BufferSource infoBufferSource;
+    if (!getBufferSource(raw, "info", infoBufferSource, context, error))
+        return false;
+
+    DOMArrayPiece salt(saltBufferSource);
+    DOMArrayPiece info(infoBufferSource);
+
+    params = adoptPtr(new WebCryptoHkdfParams(hash, salt.bytes(), salt.byteLength(), info.bytes(), info.byteLength()));
+    return true;
+}
+
 bool parseAlgorithmParams(const Dictionary& raw, WebCryptoAlgorithmParamsType type, OwnPtr<WebCryptoAlgorithmParams>& params, ErrorContext& context, AlgorithmError* error)
 {
     switch (type) {
@@ -823,6 +853,9 @@ bool parseAlgorithmParams(const Dictionary& raw, WebCryptoAlgorithmParamsType ty
     case WebCryptoAlgorithmParamsTypeAesDerivedKeyParams:
         context.add("AesDerivedKeyParams");
         return parseAesDerivedKeyParams(raw, params, context, error);
+    case WebCryptoAlgorithmParamsTypeHkdfParams:
+        context.add("HkdfParams");
+        return parseHkdfParams(raw, params, context, error);
     }
     ASSERT_NOT_REACHED();
     return false;