Bug#252676: sshd failure

[Darren Tucker]

Darren Tucker wrote:
> Colin Watson wrote:
> [snip bug details]
> 
>> We're also seeing these symptoms on a server at work, although they're
>> highly intermittent and very difficult to track down.
> 
> I will look at this tomorrow.

I was able to sometimes reproduce this on Debian by connecting to the 
server PreferredAuthentications=keyboard-interactive then *immediately* 
cancelling the authentication with ctrl-C.

After some digging I think I have found the cause: waitpid will return 
zero if the process has not exited and none of the conditions listed 
under "ERRORS" in the man page have been met.  Attached is a patch to 
test for this too (which it should have done in the first place, sigh).

I have not been able to reproduce the problem with this patch.

(Interestingly, I was not able to reproduce it on Redhat by doing the 
same thing.  I'm not sure why, but Debian is running on faster, dual CPU 
box so it could be a timing issue.)

-- 
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4  37C9 C982 80C7 8FF4 FA69
     Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.
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