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Re: [LUG] SSH tunnel port forwarding through ISA proxy?

 

Hi,

Could be worth stopping the local instance of exim to allow you to 
forward local:25 to remote:25 to see if the change of port is upsetting 
the remote exim.

It is very strange.

Bill


Grant Sewell wrote:
> Hi Bill,
>
> The confusing part for me is why the forwarding of local:26 to 
> remote:25 through my ssh tunnel doesn't seem to work when using PuTTY 
> through an MS-ISA proxy even though the forwarding of local:143 to 
> remote:143 does (through the same tunnel).  OK, forget the proxy - I 
> just managed to recreate the problem without being at College.  I used 
> the same PuTTY profile as I do when I'm at College, but removed the 
> proxy information.  It brought up a command-line fine, imap works fine 
> but smtp still doesn't.
>
> Here's my "sudo nmap -v localhost"
> Starting Nmap 4.53 ( http://insecure.org ) at 2008-11-23 09:20 GMT
> Initiating SYN Stealth Scan at 09:20
> Scanning localhost (127.0.0.1) [1714 ports]
> Discovered open port 25/tcp on 127.0.0.1
> Discovered open port 22/tcp on 127.0.0.1
> Discovered open port 26/tcp on 127.0.0.1
> Discovered open port 445/tcp on 127.0.0.1
> Discovered open port 139/tcp on 127.0.0.1
> Discovered open port 143/tcp on 127.0.0.1
> Discovered open port 5432/tcp on 127.0.0.1
> Discovered open port 5900/tcp on 127.0.0.1
> Discovered open port 631/tcp on 127.0.0.1
> Completed SYN Stealth Scan at 09:20, 0.15s elapsed (1714 total ports)
> Host localhost (127.0.0.1) appears to be up ... good.
> Interesting ports on localhost (127.0.0.1):
> Not shown: 1705 closed ports
> PORT     STATE SERVICE
> 22/tcp   open  ssh
> 25/tcp   open  smtp
> 26/tcp   open  unknown
> 139/tcp  open  netbios-ssn
> 143/tcp  open  imap
> 445/tcp  open  microsoft-ds
> 631/tcp  open  ipp
> 5432/tcp open  postgres
> 5900/tcp open  vnc
>
> Read data files from: /usr/share/nmap
> Nmap done: 1 IP address (1 host up) scanned in 0.265 seconds
>            Raw packets sent: 1714 (75.416KB) | Rcvd: 3437 (144.372KB)
>
> So nmap shows that local is accepting connections on :26, but it can't 
> identify the service.  Incidentally, the output is identical, even 
> when it does work.
>
> "telnet localhost 25" gives this:
> Trying 127.0.0.1...
> Connected to localhost.
> Escape character is '^]'.
> 220 hplaptop ESMTP Exim 4.69 Sun, 23 Nov 2008 09:26:55 +0000
>
> Whereas "telnet localhost 26" gives:
> Trying 127.0.0.1...
> Connected to localhost.
> Escape character is '^]'.
> Connection closed by foreign host.
>
> When using the command-line version (and therefore 26 --> 25 port 
> forwarding works), it gives this:
> Trying 127.0.0.1...
> Connected to localhost.
> Escape character is '^]'.
> 220 server.thymox.co.uk ESMTP Exim 4.63 Sun, 23 Nov 2008 08:49:37 +0000
>
> I've attached the saved Wireshark data from an unsuccessful connection 
> to localhost:26, in case it is of any interest.
>
> Cheers.
> Grant.

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