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>
7 files changed
tree: c35e9c7337e2893bd2959b9ac9932bc749baa2c7
  1. acme/
  2. argon2/
  3. bcrypt/
  4. blake2b/
  5. blake2s/
  6. blowfish/
  7. bn256/
  8. cast5/
  9. chacha20poly1305/
  10. cryptobyte/
  11. curve25519/
  12. ed25519/
  13. hkdf/
  14. internal/
  15. md4/
  16. nacl/
  17. ocsp/
  18. openpgp/
  19. otr/
  20. pbkdf2/
  21. pkcs12/
  22. poly1305/
  23. ripemd160/
  24. salsa20/
  25. scrypt/
  26. sha3/
  27. ssh/
  28. tea/
  29. twofish/
  30. xtea/
  31. xts/
  32. .gitattributes
  33. .gitignore
  34. AUTHORS
  35. codereview.cfg
  36. CONTRIBUTING.md
  37. CONTRIBUTORS
  38. LICENSE
  39. PATENTS
  40. README.md
README.md

Go Cryptography

This repository holds supplementary Go cryptography libraries.

Download/Install

The easiest way to install is to run go get -u golang.org/x/crypto/.... You can also manually git clone the repository to $GOPATH/src/golang.org/x/crypto.

Report Issues / Send Patches

This repository uses Gerrit for code changes. To learn how to submit changes to this repository, see https://golang.org/doc/contribute.html.

The main issue tracker for the crypto repository is located at https://github.com/golang/go/issues. Prefix your issue with “x/crypto:” in the subject line, so it is easy to find.

Note that contributions to the cryptography package receive additional scrutiny due to their sensitive nature. Patches may take longer than normal to receive feedback.