[Bug 3802] New: Secure forwardings, check connecting user

[bugzilla-daemon at mindrot.org]

https://bugzilla.mindrot.org/show_bug.cgi?id=3802

            Bug ID: 3802
           Summary: Secure forwardings, check connecting user
           Product: Portable OpenSSH
           Version: 9.9p2
          Hardware: Other
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P5
         Component: Miscellaneous
          Assignee: unassigned-bugs at mindrot.org
          Reporter: psz at maths.usyd.edu.au

Openssh tries to keep port forwardings secure e.g. via the GatewayPorts
setting; -X may be secured with xauth, and forwarding UNIX sockets may
be safe. Still, IP forwarding is unsafe on multi-user machines: anyone
can connect to -L and -D forwardings when the ssh client machine is
multi-user, or to -R forwardings when the sshd server machine is
multi-user.

Please secure IP forwardings by checking the connecting user, ensuring
same user as that of the ssh client, or the one logged in to sshd.

These checks would be similar to say identd:
https://en.wikipedia.org/wiki/Ident_protocol
easy on Linux (via netlink calls or looking in /proc/net/tcp), and
probably possible on Windows and MacOS. (I do not know about others.)

If it would help, I may try to provide patches for Linux.

Thanks, Paul
--
Paul Szabo       psz at maths.usyd.edu.au      
www.maths.usyd.edu.au/u/psz
School of Mathematics and Statistics   University of Sydney   
Australia

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