System clock and sftp connection

September 7, 2010 at 13:48:01
Specs: Windows XP
We have 2 servers (server-A on internal network, and server-B on the DMZ).

Server-A connects via sftp to servers on internet using server-B as proxy. Everything was working normally until few days ago. On the server-A logs, we started noticing this exception:
com.maverick.ssh.SshException: Unexpected terminaton: Conduit is closed

On the server-B (proxy on dmz) logs, we saw:
[2010-08-31 20:30:07,063] ERROR Per[-]: read error: Connection reset by peer
[2010-08-31 20:30:07,063] INFO Per[-]: close: CloseCode.CONNECTION_RESET

We checked the firewall, network and everything else that we could think of.. None of these layers had any changes recently.. Finally we noticed the system time on server-B was off by 6 minutes compared to server-A. When we synch'd the time on server-B with server-A, sftp connection started working. We still cannot believe that we have fixed the issue, is timestamp that critical for a successful sftp connection? Are we missing anything else? Please let me know.

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September 7, 2010 at 17:17:32
Did you try running the command with the -vvv argument?

sftp -vvv <host>

Using the -vvv argument will print out a lot of diagnostic information and might indicate the reason for the failure.

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September 9, 2010 at 07:54:13
Unfortunately, I cannot do that because the sftp functionality is provided to us by a third party product. The product has options to turn on debugging. The debug messages don't show anything about system clock or any useful information...

I did some search on internet, saw in couple of posts where they talked about verifying the system time on both servers were on sync.. Does sftp uses system time for (ssh) handshake at all?

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