SSH Tunnel Concerns ..

SSH Tunnel Concerns ..

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Subject Author Date
SSH Tunnel Concerns .. Jack 07-05-2004
Posted by Jack on July 5, 2004, 8:53 am
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we have been asked by a division to open a port on the firewall to
allow ssh tunnelling from the internal network to remote servers.
this is for support purposes and will re-direct html and telnet that
are 'currently' unix ... the remote servers are not maintained by
anyone with a brain so its safe to assume they will not be kept upto
date with os patches etc, and theres always the chance that these
could change to a w32 platform without us knowing.

i just need someone to clarify or correct me in some of my concerns ..

my problems with doing this are, other than putting destination ip
address rules on the firewall you loose all control from a security
admin point of view. another concern is lets say the os changes to
win32 (theres no reason why they would/need to tell us this), but if
they start re-directing all ports then you then open yourself up to
passing windows worms etc right ? .. or even any unix exploits on an
unpatched system ..

the other problem being this could be used to bypass all the corporate
browser config and go via the tunnel on a go anywhere internet
connection ..

thoughts people ?


Posted by Bill Unruh on July 5, 2004, 4:13 pm
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nospam@dds.co.uk (Jack) writes:

]we have been asked by a division to open a port on the firewall to
]allow ssh tunnelling from the internal network to remote servers.

So any connection starts internally and is directed outward to the server?
Or are external connections from the outside world also redirected?

]this is for support purposes and will re-direct html and telnet that
]are 'currently' unix ... the remote servers are not maintained by
]anyone with a brain so its safe to assume they will not be kept upto
]date with os patches etc, and theres always the chance that these
]could change to a w32 platform without us knowing.

Why in the world you would allow telnet is beyond me. even if it is on an
ssh tunnel, I would not allow it.

]i just need someone to clarify or correct me in some of my concerns ..

]my problems with doing this are, other than putting destination ip
]address rules on the firewall you loose all control from a security
]admin point of view. another concern is lets say the os changes to

Control over what? It is unclear to me what is being allowed here.


]win32 (theres no reason why they would/need to tell us this), but if
]they start re-directing all ports then you then open yourself up to
]passing windows worms etc right ? .. or even any unix exploits on an

From where to where?

]unpatched system ..

]the other problem being this could be used to bypass all the corporate
]browser config and go via the tunnel on a go anywhere internet
]connection ..

By whom? The suggested topology is unclear to me.


]thoughts people ?


Posted by on July 5, 2004, 5:35 pm
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On 5 Jul 2004 08:53:06 -0700, nospam@dds.co.uk (Jack) wrote:

>we have been asked by a division to open a port on the firewall to
>allow ssh tunnelling from the internal network to remote servers.
>this is for support purposes and will re-direct html and telnet that
>are 'currently' unix ... the remote servers are not maintained by
>anyone with a brain so its safe to assume they will not be kept upto
>date with os patches etc, and theres always the chance that these
>could change to a w32 platform without us knowing.
>
>i just need someone to clarify or correct me in some of my concerns ..
>
>my problems with doing this are, other than putting destination ip
>address rules on the firewall you loose all control from a security
>admin point of view. another concern is lets say the os changes to
>win32 (theres no reason why they would/need to tell us this), but if
>they start re-directing all ports then you then open yourself up to
>passing windows worms etc right ? .. or even any unix exploits on an
>unpatched system ..
>
>the other problem being this could be used to bypass all the corporate
>browser config and go via the tunnel on a go anywhere internet
>connection ..
>
>thoughts people ?


It's a tunnel. Unless the inside server is properly configured, then
yes they can punch very large holes in your firewall.

-Chris




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