Implement HKDF for webcrypto

content/child/webcrypto/status.cc

Index: content/child/webcrypto/status.cc
diff --git a/content/child/webcrypto/status.cc b/content/child/webcrypto/status.cc
index abadf001eabe73128b3da19c0ce066462ea39e28..916254187769f23a2eb92c4e27402471b748dbb8 100644
--- a/content/child/webcrypto/status.cc
+++ b/content/child/webcrypto/status.cc
@@ -328,6 +328,20 @@ Status Status::ErrorEcdhLengthTooBig(unsigned int max_length_bits) {
                     max_length_bits));
 }
 
+Status Status::ErrorHkdfLengthTooLong() {
+  return Status(blink::WebCryptoErrorTypeOperation,
+                "The length provided for HKDF is too large.");
+}
+
+Status Status::ErrorHkdfDeriveBitsLengthNotSpecified() {
+  // TODO(nharper): The spec might change so that an OperationError should be
+  // thrown here instead of a TypeError.
+  // (https://www.w3.org/Bugs/Public/show_bug.cgi?id=27771) If the spec is

[eroman, 2015/01/08 02:39:43]

nit: The last sentence seems obvious, suggest removing it.

[nharper, 2015/01/09 18:35:55]

Done.

+  // updated, this should be changed from TypeError to OperationError.
+  return Status(blink::WebCryptoErrorTypeType,
+                "Length must be specified for deriveBits.");

[eroman, 2015/01/08 02:39:43]

Can you suggest something better for this wording? When reading this it looks
like the deriveBits() method, however the length parameter is mandatory for
deriveBits().

This is the same discussion we had on the comment.

Perhaps using similar language to the comment (although it won't make much sense
to callers who haven't read the spec)?

[nharper, 2015/01/09 18:35:55]

How about "No length was specified for the HKDF Derive Bits operation." I also
doubt that a caller would ever see this, because it would only happen in
DeriveKey if GetKeyLength returns a successful status and also sets
has_length_bits to false, and it looks like none of our algorithms do that.

[eroman, 2015/01/09 19:31:53]

Can't you reproduce by calling deriveKey() on HKDF to derive an HKDF key? Can
you add a test that exercises this?

+}
+
 Status::Status(blink::WebCryptoErrorType error_type,
                const std::string& error_details_utf8)
     : type_(TYPE_ERROR),