sshd and consequences of HostKeyAgent

[Igor Bukanov]

Hello,

I tried to use HostKeyAgent with sshd 6.7 under Linux. That worked for
Linux clients. However, when I tried to connect from OpenSSH 6.2 under
Mac OS X, the server disconnects:

debug2: bits set: 1026/2048
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
Connection closed by 84.22.97.209

When I disabled HostKeyAgent and switched HostKey back to the private
keys, then I could connect from the Mac client again.This implies that
HostKeyAgent somehow affects the bytes that are sent to the client.

Why is it so? I.e. shouldn't HostKeyAgent just be an implementation
detail that should not affect the client in any way?