Interop problem with old dropbear and new openssh

Graham Cobb g+dropbear at
Sun Oct 16 19:20:00 WST 2011

On Saturday 01 October 2011 19:58:30 Rob Landley wrote:
> On 09/30/2011 04:38 PM, Graham Cobb wrote:
> > However, recently I upgraded one of my desktops and I can no longer
> > connect to the router.  Dropbear on the router is exiting with:
> > 
> > exit before auth: bad buf_getwriteptr
> > 
> > The desktop is running "SSH-2.0-OpenSSH_5.9p1 Debian-1" (it failed with
> > 5.8 as well).  However, another desktop still running
> > "SSH-2.0-OpenSSH_5.5p1 Debian-6" still works fine.  The config files are
> > identical.
> If you'd like to try the current version, statically linked binaries of
> current dropbearmulti for several of architectures are at:

Just to close off this thread in case someone finds it in the future: I tracked 
down the set of changes in OpenSSH that caused the dropbear problem and there 
does not seem to be any option which can revert the behaviour.  So, the only 
fix is to get a newer version of dropbear.

I can report that 0.53.1 fixes the problem (0.44test2 and 0.43 were what I was 
running and both do not work).  Rob's binaries worked but in the end I built a 
smaller (non-static) version specifically for my (old) OpenWRT configuration.


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