ssh: fix certificate authentication with OpenSSH 7.2-7.7

OpenSSH 7.2-7.7 advertises support for rsa-sha2-256 and rsa-sha2-512
in the "server-sig-algs" extension but doesn't support these
algorithms for certificate authentication, so if the server rejects
the key try to use the obtained algorithm as if "server-sig-algs" had
not been implemented.

Fixes golang/go#58371

Change-Id: Id49960d3dedd32a21e2c6c2689b1696e05398286
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/510155
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Run-TryBot: Nicola Murino <nicola.murino@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Nicola Murino <nicola.murino@gmail.com>
2 files changed
tree: faf0ede16173b4db863bdef8fccbe7b6b93fad55
  1. acme/
  2. argon2/
  3. bcrypt/
  4. blake2b/
  5. blake2s/
  6. blowfish/
  7. bn256/
  8. cast5/
  9. chacha20/
  10. chacha20poly1305/
  11. cryptobyte/
  12. curve25519/
  13. ed25519/
  14. hkdf/
  15. internal/
  16. md4/
  17. nacl/
  18. ocsp/
  19. openpgp/
  20. otr/
  21. pbkdf2/
  22. pkcs12/
  23. poly1305/
  24. ripemd160/
  25. salsa20/
  26. scrypt/
  27. sha3/
  28. ssh/
  29. tea/
  30. twofish/
  31. x509roots/
  32. xtea/
  33. xts/
  34. .gitattributes
  35. .gitignore
  36. codereview.cfg
  37. CONTRIBUTING.md
  38. go.mod
  39. go.sum
  40. LICENSE
  41. PATENTS
  42. README.md
README.md

Go Cryptography

Go Reference

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.