sshd exits during login attempt on WinXP 2003 x64 if user running sshd is different from user running ssh

[Brian Kasper]

I've been wrestling with this problem for a long time, and I think I've 
reduced the failure mode to a single, deterministic cause -- which might 
help someone more familiar with the code suggest a fix.

At first, Cygwin ssh/sshd worked fine on my WinXP 2003 x64 system.  I 
installed Cygwin as administrator, and generally ran as another user 
("kasper").  At some point, possibly after a reboot, "ssh localhost" 
began to fail.

I stopped the sshd service, and started experimenting with running sshd 
from the command line with the '-d' option so I could watch the 
debugging output.

Here are the results in a nutshell:

If I run "c:\cygwin\usr\sbin\sshd -d" in a Windows command prompt 
started as user "kasper" and then run "ssh localhost" in another command 
prompt started as user kasper, everything WORKS.

If I run "c:\cygwin\usr\sbin\sshd -d" in a Windows command prompt 
started as user "administrator" and then run "ssh localhost" in another 
command prompt started as user "administrator", everything WORKS.

If I run "c:\cygwin\usr\sbin\sshd -d" in a Windows command prompt 
started as user "administrator" and then run "ssh -l kasper localhost" 
in another command prompt started as user "administrator", the session 
FAILS with the message "/bin/bash: Permission denied".

If I run "c:\cygwin\usr\sbin\sshd -d" in a Windows command prompt 
started as user "administrator" and then run "ssh localhost" in a 
command prompt started as user "kasper", the session FAILS after these 
sshd debugging messages:

debug1: test whether pkalg/pkblob are acceptable
debug1: temporarily_use_uid: 1003/513 (e=500/513)
seteuid 1003: Permission denied
debug1: do_cleanup

It looks like there is a nontrivial issue with user permissions under 
the x64 version of Windows XP 2003.  Is there something additional I can 
do to help debug this?

I've attached the output of "cygcheck -s -v -r" (as cygcheck.out), as 
well as logs of the sshd debugging output for one successful and one 
failed login attempt.

-Brian Kasper
  kasper@aero.org
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