Possible Security Hole in SSHD w/ CYGWIN?

David Willis david_willis@comcast.net
Tue Feb 9 06:43:00 GMT 2016


I noticed that when connecting via SSH to a CYGWIN-based SSHD server, if the
user connects to a network share (i.e. they CD to the share UNC path in the
BASH/CYGWIN shell), they get connected as the privileged server user account
created for privilege separation when SSHD is configured w/ ssh-host-config.
In other words, they have the rights of that account, and if that account
happens to be a domain admin (or even a local admin on the box hosting the
share), that user has full admin rights on that share, when in fact they
should have the rights assigned to the user account they SSH'd in with.

To reproduce, connect via SSH (from either a Linux or CYGWIN/Windows client)
to a CYGWIN-based SSHD server using a normal privileged user account (an
account preferably that is not an admin either on the client or server
machine). Once connected to the Windows SSHD server, CD to a UNC path of a
network share. Once CD'd to that path, check Computer Management on that
server, and go to Shares->Open Sessions, and you will see that the user
connected is the privileged SSHD server account (and it will obviously show
as being connected from the machine you are SSH'd into).

Anyone else ever notice this before?

Running OpenSSH v7 BTW, SSH client is Win7, SSH server Win7, file share
server Win2008R2



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