code review 5018045: crypto/tls: support SSLv3

crypto/tls: support SSLv3

It would be nice not to have to support this since all the clients
that we care about support TLSv1 by now. However, due to buggy
implementations of SSLv3 on the Internet which can't do version
negotiation correctly, browsers will sometimes switch to SSLv3. Since
there's no good way for a browser tell a network problem from a buggy
server, this downgrade can occur even if the server in question is
actually working correctly.

So we need to support SSLv3 for robustness :(

Fixes issue 1703.

[agl1, 2011-09-14 17:57:13]

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

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

[bradfitz, 2011-09-14 18:11:27]

LGTM

http://codereview.appspot.com/5018045/diff/3001/src/pkg/crypto/tls/cipher_sui...
File src/pkg/crypto/tls/cipher_suites.go (right):

http://codereview.appspot.com/5018045/diff/3001/src/pkg/crypto/tls/cipher_sui...
src/pkg/crypto/tls/cipher_suites.go:86: type macFunction interface {
little bit of a weird name (not a function type) but I can't think of anything
better.  macer or macSizer is probably weirder.

http://codereview.appspot.com/5018045/diff/3001/src/pkg/crypto/tls/handshake_...
File src/pkg/crypto/tls/handshake_messages.go (right):

http://codereview.appspot.com/5018045/diff/3001/src/pkg/crypto/tls/handshake_...
src/pkg/crypto/tls/handshake_messages.go:681: x[3] = byte(len(m.verifyData))
I trust this won't overflow.  I didn't audit callers.

http://codereview.appspot.com/5018045/diff/3001/src/pkg/crypto/tls/prf.go
File src/pkg/crypto/tls/prf.go (right):

http://codereview.appspot.com/5018045/diff/3001/src/pkg/crypto/tls/prf.go#new...
src/pkg/crypto/tls/prf.go:95: i++
I'd say panic on i > 10, but I guess the b[j] will effectively be the same
thing, so who cares.

[agl1, 2011-09-14 19:32:31]

*** Submitted as http://code.google.com/p/go/source/detail?r=51381e821177 ***

crypto/tls: support SSLv3

It would be nice not to have to support this since all the clients
that we care about support TLSv1 by now. However, due to buggy
implementations of SSLv3 on the Internet which can't do version
negotiation correctly, browsers will sometimes switch to SSLv3. Since
there's no good way for a browser tell a network problem from a buggy
server, this downgrade can occur even if the server in question is
actually working correctly.

So we need to support SSLv3 for robustness :(

Fixes issue 1703.

R=bradfitz
CC=golang-dev
http://codereview.appspot.com/5018045