openssh bugs - Aug 2021 - [Bug 3334] document `none` keyword for ProxyJump

https://bugzilla.mindrot.org/show_bug.cgi?id=3334

            Bug ID: 3334
           Summary: document `none` keyword for ProxyJump
           Product: Portable OpenSSH
           Version: 8.6p1
          Hardware: Other
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P5
         Component: Documentation
          Assignee: unassigned-bugs at mindrot.org
          Reporter: calestyo at scientia.net

Hey.

I think ssh_config?s ProxyJump should also mention the apparently
working `none` keyword (just like ProxyCommand).

This is needed to do things like:
Host login.example.org
   ProxyJump none

Host *.example.org
   ProxyJump login.example.org

to not end up in an endless loop.

Cheers,
Chris.

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https://bugzilla.mindrot.org/show_bug.cgi?id=3334

Darren Tucker <dtucker at dtucker.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dtucker at dtucker.net
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED
             Blocks|                            |3302

--- Comment #1 from Darren Tucker <dtucker at dtucker.net> ---
(In reply to Christoph Anton Mitterer from comment #0)
> I think ssh_config?s ProxyJump should also mention the apparently
> working `none` keyword (just like ProxyCommand).
Yep, it's handled in parse_jump().  Added to man page.
> to not end up in an endless loop.
ssh will now detect trivial loops for you:

$ cat tmp 
Host *.example.org
   ProxyJump login.example.org
$ ./ssh -F tmp login.example.org
jumphost loop via login.example.org

You can still construct non-trivial ones though.

Thanks for the report.


Referenced Bugs:

https://bugzilla.mindrot.org/show_bug.cgi?id=3302
[Bug 3302] Tracking bug for openssh-8.7
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https://bugzilla.mindrot.org/show_bug.cgi?id=3334

--- Comment #2 from Christoph Anton Mitterer <calestyo at scientia.net>
---
> Host *.example.org
>    ProxyJump login.example.org
> 
> to not end up in an endless loop.

That should then also be documented,... plus more concrete what's
actually happening like:

If one *just* have:
> Host *.example.org
>    ProxyJump login.example.org
=> it's clear... no recursion

but what when one has:
> Host login.example.org
>    SomeOtherStuff
> Host *.example.org
>    ProxyJump login.example.org
In that case, would SomeOtherStuff still be loaded?
Or similarly if login.example.org had another ProxyJump to another
host?

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--- Comment #3 from Darren Tucker <dtucker at dtucker.net> ---
(In reply to Christoph Anton Mitterer from comment #2)
[...]
> but what when one has:
> 
> > Host login.example.org
> >    SomeOtherStuff
> > Host *.example.org
> >    ProxyJump login.example.org
> 
> In that case, would SomeOtherStuff still be loaded?
Yes.  The parser is first-match for each keyword.  From ssh_config(5):

     For each parameter, the first obtained value will be used.  The
     configuration files contain sections separated by Host
specifications,
     and that section is only applied for hosts that match one of the
patterns
     given in the specification.  The matched host name is usually the
one
     given on the command line (see the CanonicalizeHostname option for
     exceptions).

     Since the first obtained value for each parameter is used, more
host-
     specific declarations should be given near the beginning of the
file, and
     general defaults at the end.
> Or similarly if login.example.org had another ProxyJump to another
> host?
Then it'll get used.   It'll only report a jumphost loop if the host,
port and user are all end up all identical.

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED

--- Comment #4 from Damien Miller <djm at mindrot.org> ---
closing bugs resolved before openssh-8.9

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