[OleksandrMorskyi]

Fixes #892

When SSH_HOST_PUBLIC_KEY or SSH_KNOWN_HOSTS_FILE is used, HostKeyAlgorithms is now set to the type(s) of the configured host key(s). Previously the client negotiated its default preference (ECDSA first), so a pinned ED25519 key never matched when the server also offered ECDSA.

• Pinned key: algorithm derived from the key type (RSA also allows rsa-sha2-256/512)
• known_hosts: algorithms of all keys known for the host; unknown hosts keep the default behavior
• Tests: in-memory SFTP server with ED25519 + ECDSA host keys, covering pin and known_hosts for both types plus mismatch cases. Without the fix, the two ED25519 cases fail.
• Docs: note that any host key type can be used

[m90]

This looks good, thank you. I wonder if we can also test this behavior in the integration test, e.g. by providing a non-ecdsa key instead?

[OleksandrMorskyi]

Good idea, thanks! I added a fourth step to the SSH integration test: the backup container is restarted with the server’s ED25519 host key pinned (the test server offers both ECDSA and ED25519), and the test checks that the backup is uploaded. Without the fix it fails with ssh: host key mismatch.

[m90]

This is now released in v2.50.1, thanks a lot 🎩