x/crypto/ssh: allow a custom Config to specify CBC mode.

Cryptographic flaws are so hard to kill it can only be a matter of time
before they start crying “brains!” and holding their arms out straight.

Fixes golang/go#13776.

Change-Id: Iee1c19dbe823eb8728e283dd11083638e41f7189
Reviewed-on: https://go-review.googlesource.com/18482
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Adam Langley <agl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
1 file changed