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Old 10-16-2013, 09:39 AM
jimbobmcgee jimbobmcgee is offline
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Join Date: Apr 2005
Posts: 21
Alternative means to handle failed authentications

I'm having some trouble preventing spurious connections to my load balanced SFTP servers, because the load balancer proxies the connection to the server, thus obscuring the source IP with its own (making the Deny Hosts feature effective useless).

I appreciate that the lack of SSH inspection is a limitation of the load balancer in question (and not VShell), so I've started looking at possible alternatives, both leveraging the Authentication Failed trigger to do either of the following:
  1. Tally the source port (as determined by the load balancer, and seen by VShell) to the source IP (as seen by the load balancer) and denying said source IP in the load balancer's access list (using the load balancer's API)
  2. Wait a number of seconds (i.e. to significantly slow down the rate of automated connection attempts)
I can't do the first, because there is no substitution variable for the client port that I can use in the trigger, so I can't pass the port number to the trigger script without strenuously mining the log file.

I can't do the second, because the trigger appears to run out-of-band, so the wait does not impose itself on the connection in question. This would probably also affect the first since, if the trigger does not wait, the connection could be gone from the load balancer before the script can tally the port to an IP.

Is there any way I can make the trigger run in-band (e.g. can a "wait for exit" option be added to the trigger definition)?

Instead, is there any way a tarpitting-style wait option could be added natively to the VShell app?

Are there any other thoughts on how I might achieve some measure of control over spurious connections (without resorting to taking the service out of load balancing)?

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authentication , triggers , vshell

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