Implement HMAC support in lib/crypto.

Implement HMAC support in lib/crypto.

R=sgjesse@google.com,benl@google.com
BUG=
TEST=

Committed: https://code.google.com/p/dart/source/detail?r=7145

[Ben Laurie (Google), 2012-04-27 13:26:33]

https://chromiumcodereview.appspot.com/10170027/diff/1/lib/crypto/crypto.dart
File lib/crypto/crypto.dart (right):

https://chromiumcodereview.appspot.com/10170027/diff/1/lib/crypto/crypto.dart...
lib/crypto/crypto.dart:20: * called after the first call to [digest] a
CryptoHashException is thrown.
I still say you should be able to call [digest] a second time.

https://chromiumcodereview.appspot.com/10170027/diff/1/lib/crypto/crypto.dart...
lib/crypto/crypto.dart:69: interface HMAC default _HMAC {
Why CryptoHash and not CryptoHMAC?

https://chromiumcodereview.appspot.com/10170027/diff/1/lib/crypto/sha_utils.dart
File lib/crypto/sha_utils.dart (right):

https://chromiumcodereview.appspot.com/10170027/diff/1/lib/crypto/sha_utils.d...
lib/crypto/sha_utils.dart:13: class _SHACryptoHashBase {
Why no longer implements CryptoHash?

[Søren Gjesse, 2012-04-27 16:46:01]

It seems that this CL is missing the file hmac.dart referenced from crypto.dart.

[Mads Ager (google), 2012-04-30 07:13:52]

Added the missing file. Sorry about that.

[Mads Ager (google), 2012-04-30 07:56:56]

https://chromiumcodereview.appspot.com/10170027/diff/1/lib/crypto/crypto.dart
File lib/crypto/crypto.dart (right):

https://chromiumcodereview.appspot.com/10170027/diff/1/lib/crypto/crypto.dart...
lib/crypto/crypto.dart:20: * called after the first call to [digest] a
CryptoHashException is thrown.
On 2012/04/27 13:26:33, Ben Laurie (Google) wrote:
> I still say you should be able to call [digest] a second time.

OK, allowed multiple calls to digest to extract the message digest.

https://chromiumcodereview.appspot.com/10170027/diff/1/lib/crypto/crypto.dart...
lib/crypto/crypto.dart:69: interface HMAC default _HMAC {
On 2012/04/27 13:26:33, Ben Laurie (Google) wrote:
> Why CryptoHash and not CryptoHMAC?

Yeah, good question. There is next to zero chance that HMAC will conflict with
anything else. I guess these should really by Hash and HMAC. Changed. If this
leads to issues with conflicts we can rename.

https://chromiumcodereview.appspot.com/10170027/diff/1/lib/crypto/sha_utils.dart
File lib/crypto/sha_utils.dart (right):

https://chromiumcodereview.appspot.com/10170027/diff/1/lib/crypto/sha_utils.d...
lib/crypto/sha_utils.dart:13: class _SHACryptoHashBase {
On 2012/04/27 13:26:33, Ben Laurie (Google) wrote:
> Why no longer implements CryptoHash?

Because it doesn't. It does not have the newInstance method. I'll add it as an
abstract method and put back the implements.

[Søren Gjesse, 2012-04-30 09:05:23]

LGTM with a few suggestions

https://chromiumcodereview.appspot.com/10170027/diff/8002/lib/crypto/hmac.dart
File lib/crypto/hmac.dart (right):

https://chromiumcodereview.appspot.com/10170027/diff/8002/lib/crypto/hmac.dar...
lib/crypto/hmac.dart:19: _hash = _hash.newInstance();
Add and use a reset() method instead? Also as an object implementing Hash is
passed it might be the right thing to do to call reset before using it.

https://chromiumcodereview.appspot.com/10170027/diff/8002/lib/crypto/sha_util...
File lib/crypto/sha_utils.dart (right):

https://chromiumcodereview.appspot.com/10170027/diff/8002/lib/crypto/sha_util...
lib/crypto/sha_utils.dart:24: 'Hash update method called after digest');
Maybe add " was retrieved" to exception text.

[Mads Ager (google), 2012-04-30 09:37:10]

https://chromiumcodereview.appspot.com/10170027/diff/8002/lib/crypto/hmac.dart
File lib/crypto/hmac.dart (right):

https://chromiumcodereview.appspot.com/10170027/diff/8002/lib/crypto/hmac.dar...
lib/crypto/hmac.dart:19: _hash = _hash.newInstance();
On 2012/04/30 09:05:23, Søren Gjesse wrote:
> Add and use a reset() method instead? Also as an object implementing Hash is
> passed it might be the right thing to do to call reset before using it.

We explicitly do not want to do that. The reason for not wanting to add reset is
that you can get 'dangling' references to hashes and get weird results. Avoiding
object reuse seems cleaner.

https://chromiumcodereview.appspot.com/10170027/diff/8002/lib/crypto/sha_util...
File lib/crypto/sha_utils.dart (right):

https://chromiumcodereview.appspot.com/10170027/diff/8002/lib/crypto/sha_util...
lib/crypto/sha_utils.dart:24: 'Hash update method called after digest');
On 2012/04/30 09:05:23, Søren Gjesse wrote:
> Maybe add " was retrieved" to exception text.

Done.