code review 6775043: crypto/tls: add support for ECDH ECDSA

crypto/tls: add support for ECDH ECDSA

Add support for ECDH ECDSA (RFC4492). ECDH ECDSA implements a TLS key
agreement where the client generates an ephemeral EC public/private
key pair and signs it. The pre-master secret is then calculated using
ECDH. Alternatively a fixed client EC public/private key pair can be
used.

[jsing, 2012-11-24 16:14:42]

Hello agl@golang.org (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://go.googlecode.com/hg/

[agl1, 2012-11-26 15:33:06]

I stopped the review at this point.

Fixed ECDH is a very obscure corner of TLS that very little supports.
Client-auth with fixed ECDH is basically unheard of.

I'm hesitant that we want the cost of code this odd. Are you sure that you don't
want ECDHE_ECDSA?

https://codereview.appspot.com/6775043/diff/17001/src/pkg/crypto/tls/cipher_s...
File src/pkg/crypto/tls/cipher_suites.go (right):

https://codereview.appspot.com/6775043/diff/17001/src/pkg/crypto/tls/cipher_s...
src/pkg/crypto/tls/cipher_suites.go:59: {TLS_ECDH_ECDSA_WITH_RC4_128_SHA, 16,
20, 0, ecdhECDSAKA, true, cipherRC4, macSHA1},
ECDH_ECDSA, not ECDHE_ECDSA? That's a very obscure ciphersuite and probably not
what you wanted.

https://codereview.appspot.com/6775043/diff/17001/src/pkg/crypto/tls/common.go
File src/pkg/crypto/tls/common.go (right):

https://codereview.appspot.com/6775043/diff/17001/src/pkg/crypto/tls/common.g...
src/pkg/crypto/tls/common.go:99: certTypeRSAFixedECDH   = 65 // A certificate
containing an ECDH-capable public key, signed with RSA.
"A certificate containing an ECDH public value, signed with RSA"

https://codereview.appspot.com/6775043/diff/17001/src/pkg/crypto/tls/common.g...
src/pkg/crypto/tls/common.go:100: certTypeECDSAFixedECDH = 66 // A certificate
containing an ECDH-capable public key, signed with ECDSA.
ditto, but with ECDSA of course.

https://codereview.appspot.com/6775043/diff/17001/src/pkg/crypto/tls/handshak...
File src/pkg/crypto/tls/handshake_client.go (right):

https://codereview.appspot.com/6775043/diff/17001/src/pkg/crypto/tls/handshak...
src/pkg/crypto/tls/handshake_client.go:199: case certTypeECDSAFixedECDH:
client auth with fixed ECDH is even more obscure than fixed ECDH server-side!