tree c35e9c7337e2893bd2959b9ac9932bc749baa2c7
parent 45a5f77698d342a8c2ef8423abdf0ba6880b008a
author Ian Haken <ihaken@netflix.com> 1540778834 +0000
committer Han-Wen Nienhuys <hanwen@google.com> 1540809014 +0000

ssh: support SSH agent signature flags and custom extensions

This commit implements two new features. To preserve backwards
compatibility the new methods are added to an `ExtendedAgent` interface
which extends `Agent`. The client code implements `ExtendedAgent`
(which extends Agent) so you can call these additional methods against
SSH agents such as the OpenSSH agent. The ServeAgent method still
accepts Agent but will attempt to upcast the agent to `ExtendedAgent`
as needed, so if you supply an ExtendedAgent implementation you can
implement these additional methods (which keyring does).

The first feature is supporting the standard flags that can be passed to
SSH Sign requests, requesting that RSA signatures use SHA-256 or
SHA-512. See section 4.5.1 of the SSH agent protocol draft:
https://tools.ietf.org/html/draft-miller-ssh-agent-02

The second feature is supporting calling custom extensions from clients
and implementing custom extensions from servers. See section 4.7 of the
SSH agent protocol draft:
https://tools.ietf.org/html/draft-miller-ssh-agent-02

Change-Id: I0f74feb893762c27e921ec37604d3a46434ee6ef
GitHub-Last-Rev: 2e23fd01c0e95b664e8507682f0bd5bd61d4c146
GitHub-Pull-Request: golang/crypto#53
Reviewed-on: https://go-review.googlesource.com/c/123955
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>