Question

Need to restrict SSH tunnels to a certain IP.

Asked by: CousinDupree

I have a machine I would like to use to provide remote access to workstations.  I plan to use puTTY to create a SSH tunnel and port forward traffic.  I would like to control which remote machines users can reach.  How do I accomplish this?

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Asked On
2009-09-14 at 10:38:11ID24730357
Tags

SSH

,

port forwarding

,

tunnel

,

puTTY

,

linux

Topics

Linux Network Security

,

SSH / Telnet Software

,

Linux Networking

Participating Experts
3
Points
500
Comments
5

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Answers

 

by: NopiusPosted on 2009-09-14 at 15:52:48ID: 25330032

You should use openssh version 5.
man sshd_config

Example section of sshd_config:
 
... [skip] ...
Match User username
AllowTcpForwarding yes
PermitOpen host:port
... [skip] ...

                                              
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by: lanboyoPosted on 2009-09-15 at 05:37:59ID: 25334159

What he said...  The safest thing is to restrict what the host device can access though.

 

by: CousinDupreePosted on 2009-09-15 at 14:00:30ID: 25339455

The question I have is is it possible to limit which IP Addresses can be reached by forwarding?  For example, can I allow Bob to reach his own workstation and nothing else?  Nancy to reach her own workstation and nothing else?

 

by: NopiusPosted on 2009-09-15 at 15:06:10ID: 25340106

CousinDupree you can  restrict user access only to specific IP _and_ port (with the example above) and only with OPenSSH version 5 (not 4 that is shipped by default with some distributions)

If you need to restrict to IP only, you may use iptables feature:
iptables -A OUTPUT -m owner --uid-owner XXXX -d Y.Y.Y.Y -j ACCEPT
iptables -A OUTPUT -m owner --uid-owner XXXX  -j REJECT

where XXXX is uid and Y.Y.Y.Y is a destination host.

 

by: mburdickPosted on 2009-09-15 at 18:37:55ID: 25341116

You could also insert black hole routes on the SSH server for the machines / destinations that you do NOT want people to be able to reach. Of course, that will eliminate ALL communications between the SSH server and those workstations.

20120131-EE-VQP-002

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