Updating ed25519-dalek breaks agent server

[gotlougit]

Hello, I've been using russh as the SSH implementation for sshield, which aims to be a more secure SSH agent server.

I was updating my dependencies and noticed that an upgrade for russh broke the agent. I bisected russh and found commit 43edc32 was the culprit. Scanning the agent server code, I don't really see anything that would break the agent.

Running ssh -T <sample-server> with the updated russh gives me this output:

debug1: Found key in /home/gotlou/.ssh/known_hosts:2
debug1: rekey out after <redacted> blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey in after <redacted> blocks
debug1: get_agent_identities: ssh_fetch_identitylist: incomplete message

Whereas it should be:

debug1: Found key in /home/gotlou/.ssh/known_hosts:2
debug1: rekey out after <redacted> blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey in after <redacted> blocks
debug1: get_agent_identities: agent returned <redacted> keys

I think there is some issue with the way the russh agent sends the public keys to the ssh client, perhaps there was a conversion or two that was overlooked while upgrading to ed25519-dalek 2.0?

[Eugeny]

I think I might have found it - let me know if the fix works for you!

[gotlougit]

This fixed it, thank you very much!