[Bug 3057] New: Fork-bomb when misconfiguring a host to ProxyJump onto itself

bugzilla-daemon at bugzilla.mindrot.org bugzilla-daemon at bugzilla.mindrot.org
Wed Aug 14 18:14:20 AEST 2019


https://bugzilla.mindrot.org/show_bug.cgi?id=3057

            Bug ID: 3057
           Summary: Fork-bomb when misconfiguring a host to ProxyJump onto
                    itself
           Product: Portable OpenSSH
           Version: 7.9p1
          Hardware: Other
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P5
         Component: ssh
          Assignee: unassigned-bugs at mindrot.org
          Reporter: andrej at kacian.sk

Following configuration causes ssh to spawn endless copies of itself
when user tries to connect to the specified host.

Host foo
ProxyJump foo

# or more generic
Host *
ProxyJump %h

I have reproduced this on 7.9p1 on Suse Linux Enterprise Server 15 and
on 7.4p1 on Debian Stretch (currently oldstable).

Depending on limits configured on the server, this, like any other
forkbomb, can cause all kinds of fun behavior on the local server.

Perhaps the client could check for this edge case and avoid trying to
make an impossible proxy connection.

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