ssh: support rsa-sha2-256/512 on the server side

This lets clients know we support rsa-sha2-256/512 signatures from
ssh-rsa public keys. OpenSSH prefers to break the connection rather than
attempting trial and error, apparently.

We don't enable support for the "ext-info-s" because we're not
interested in any client->server extensions.

This also replaces isAcceptableAlgo which was rejecting the
rsa-sha2-256/ public key algorithms.

Tested with OpenSSH 9.1 on macOS Ventura.

Fixes golang/go#49269
Updates golang/go#49952

Co-authored-by: Nicola Murino <>
Co-authored-by: Kristin Davidson <>
Change-Id: I4955c3b12bb45575e9977ac657bb5805b49d00c3
Run-TryBot: Filippo Valsorda <>
TryBot-Result: Gopher Robot <>
Reviewed-by: Roland Shoemaker <>
Reviewed-by: Nicola Murino <>
Reviewed-by: Michael Knyszek <>
4 files changed
tree: 4fb497ff54ec4aedb597e037db50d3570d4110ac
  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. xtea/
  32. xts/
  33. .gitattributes
  34. .gitignore
  35. codereview.cfg
  37. go.mod
  38. go.sum

Go Cryptography

Go Reference

This repository holds supplementary Go cryptography libraries.


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

Report Issues / Send Patches

This repository uses Gerrit for code changes. To learn how to submit changes to this repository, see

The main issue tracker for the crypto repository is located at 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.