[PATCH] Specify signature algorithm during server hostkeys prove

[Maxime Rey]

Hello,

I've found that when using the ssh agent and sshd together, there is an issue
when using multiple host keys. Specifically, after the key exchange phase,
when a client requests proof of ownership for the host keys via the
"hostkeys-prove-00 at openssh.com" request, the server prepares the response
without specifying the signature algoorithm in case of non-RSA keys.

This leads to "SSH_ERR_INVALID_ARGUMENT" when verifying the signature in :

openssh-portable/authfd.c line 
if ((r = sshkey_check_sigtype(sig, len, alg)) != 0)

To resolve this, I explicitly sets the signature
algorithm, ensuring proper verification for all key types.

I would appreciate any feedback or suggestions regarding this issue.

Best regards,
Maxime

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