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SSH2 Disconnects Intermittently with 3.5 (1 viewing) (1) Guest
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TOPIC: SSH2 Disconnects Intermittently with 3.5
#1724
SSH2 Disconnects Intermittently with 3.5 16 Years ago  
I am connecting to a TRU64 Server with a SSH2 connection and when I use the latest versions (3.13 and now 3.5) to connect, it disconnects me after so many minutes whether I am using it or not. I have enabled keep alives to no avail.

Noteworthy: If I ssh from another unix server that I am telneted into, I can stay connected indefinitely.

Also, when I use version 2.12 from home over a vpn, it also stays connected indefinitely.

Any Ideas?

Jack

[ November 30, 2004, 12:19 PM: Message edited by: Brian T. Pence ]
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#1725
Re: SSH2 Disconnects Intermittently with 3.5 16 Years ago  
Which SSH server (and which version) are you connecting to? Look at Options->SSH Info while you are connected to be sure.

Are you getting an error message? If so, what is it? Does this seem to happen at the same time interval every time?

There was one issue in the past where the connection would die after one hour due to a key re-exchange problem with older SSH servers. The symptom was that it would occur at exactly one hour after connection, regardless of activity or keepalive setting. The connection would die at regular intervals (one hour) without any notice or error message. If, however, the time to failure seems to be fairly random, I would suspect network issues. Network issues generally come with error messages, though.

Network stability, firewalls, etc could be an issue, but it's important to distinguish whether the connection failure at work and the connection success at home (over vpn) are due to the different versions you are using or the different network topology. Try running version 2.13 and 3.50 at the same time on the same machine at work. Install version 2.13 first, then 3.50 in a separate directory. Then, you can run both at the same time. If 3.50 quits out and 2.13 keeps going, it's likely an application issue.

In other words, I'd hesitate to make the statement that since 2.13 succeeds at home and 3.50 fails at work that there is a bug in 3.50. I'd first like to establish that 2.13 also succeeds at work where 3.50 fails.
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#1726
Re: SSH2 Disconnects Intermittently with 3.5 16 Years ago  
Thanks for the quick reply.

I think you are on to something with key re-exchange problem. I don't get any errors. It simply shows the login window with an "Authentication Failed" message. It may be after one hour, but I have not sat around and timed it everytime.

The Server ID is 'SSH-2.0-3.20 SSH Secure Shell Tru64 UNIX'. I don't have this issue with HP-UX on another server using Open SSH 3.4.

I'll try v2.13 here and see if that works. If so, how can we get 3.5 to re-authenticate properly?

Thanks for you help.

Jack
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#1727
Re: SSH2 Disconnects Intermittently with 3.5 16 Years ago  
Jack,

So, you're saying that at some point during the connection the authentication dialog pops back up again and says 'authentication failed' when you did not even try to authenticate?

Authentication should happen ONCE at the beginning of the connection. Is it possible that you become disconnected and when you hit return a second connection attempt is made??? (Hitting return will start a new connection if you're disconnected). To be sure, switch the option on the 'global' tab that says 'Close application on disconnect' to the 'prompt' value. This will ensure that you know when you are getting disconnected even if no error message is supplied.

If you're saying that the authentication dialog pops back up spontaneously, we have additional issues to address. I may have you download a version that has additional logging enabled. We'll know more then.

It could be server specific. I generally use OpenSSH and your server seems to be the one from FSecure. Can you send me a copy of your sshd_config file so I can see if there are any enabled server options that may be involved here?

The authentication sequence was modified in version 3.50 and this issue may be related to that. I never had this issue reported under 2.13, so I'm going to guess it will work fine. The authentication and key re-exchange are not likely to be related.

Brian
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#1728
Re: SSH2 Disconnects Intermittently with 3.5 16 Years ago  
BTW, are you using password authentication or something else?
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#1729
Re: SSH2 Disconnects Intermittently with 3.5 16 Years ago  
Brian,

I am using password authentication.

I confirmed that 2.13 does not disconnect, but 3.5 does. It basically does what I said and the Authentication pop up window pop's up with an "Authentication Failed" screen and prompts for a password without me hitting enter. The popup is there when I get back to my desk if I have left, or just pops up after about an hour as you said.

While this pop up is up, the connection is still on the UNIX side as being connected, but if I reenter the password, my connection is reset and I lose anything that I was doing (e.g. vi session).

It also only does this against the TRU64, while the OPEN SSH on HPUX works fine.

I'll send you the SSH2_CONFIG file.

Thanks.
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#1730
Re: SSH2 Disconnects Intermittently with 3.5 16 Years ago  
Brian,

After changing 'Close application on disconnect' to the 'prompt', I received an error message box "Remote Server Disconnected: Received unexpect packet 50".

This only happens with AT 3.5 connected to TRU64 SSH2. That is not a typo on my part, that is exactly what the error message says.

Jack
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#1731
Re: SSH2 Disconnects Intermittently with 3.5 16 Years ago  
Jack,

Can you send a screen snapshot?

Brian
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#1732
Re: SSH2 Disconnects Intermittently with 3.5 16 Years ago  
Sorry, the message box with the error won't come up again. The Authentication popup is coming up again with an "Authentication Failed" message. This after about an hour of already being authenticated and logged in and working.

I can send you that screen shot. How should I get the snapshot to you? I can't seem to post it here.

Jack
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#1733
Re: SSH2 Disconnects Intermittently with 3.5 16 Years ago  
Mail it to me.

(bpence at celestialsoftware.net)
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Last Edit: 2010/08/04 10:39 By bpence.
 
Brian Pence
Celestial Software
SSH , SFTP, and Telnet in a tabbed interface for Windows XP, Vista, Mobile, and others
 
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#1734
Re: SSH2 Disconnects Intermittently with 3.5 16 Years ago  
The cause of this issue has been identified and resolved. AbsoluteTelnet was not behaving properly when key re-exchange was being initiated by the server. Absolute incorrectly thought that a new session was being started and re-attempted authentication. This behavior is wrong and resulted in the session terminating due to a protocol violation. The new version of Absolute has been updated to fix this:

http://www.celestialsoftware.net/telnet/AbsoluteTelnet3.59.exe

Enjoy!!!

Brian
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