cygsshd fails due to bad ownership or modes of /cygdrive/c/Users

[marco atzeri]

On Wed, Feb 7, 2024 at 3:26 AM Frank-Ulrich Sommer via Cygwin
<cygwin@cygwin.com> wrote:
> On 06.02.2024 22:22, Brian Inglis via Cygwin wrote:
> > On 2024-02-05 18:36, Eliot Moss via Cygwin wrote:
> >> On 2/5/2024 8:28 PM, Frank-Ulrich Sommer via Cygwin wrote:
> >>> On 05.02.2024 00:53, Frank-Ulrich Sommer via Cygwin wrote:
> >>>> I'm trying to run cygsshd on my PC with Windows 11 and connect from a linux machine. I have added the public key to /cygdrive/c/Users/xxx/.ssh/authorized_keys and created a symbolic link from  /cygdrive/c/Users/xxx/.ssh to /home/xxx/.ssh. As usual I checked the access rights and mode of the .ssh directory (700 and belongs to user xxx) and the authorized_keys file (600 and also belongs to user xxx) and also of the home directory (had to change ownership).

> The problem seems to be that OpenSSH does not even arrive at checking the home diretory or the .ssh directory. It starts checking every directory in the path and fails already at "/cygdrive/c/Users". Now that I know how to get the sources I added debug output to the error message. OpenSSH sees this directory as belonging to user with UID 18 and it has mode 4750. Mode ist checked not to contain 0022 which is fine here. Then it checks that the owner is the correct system user and the only criteria is that the UID must be zero. Only for AIX and HPUX the user "bin" with UID 2 is also accepted. So this check fails and OpenSSH assumes that the directory does not belong to the correct privileged system user.
>
> I think the only way to fix this with the current OpenSSH is disabling strict mode, but normally I'm quite reluctant to do something like that.2
>

what is the issue on using /home/USER/.ssh folder ?

I prefer to leave the Cygwin Home and the Windows Home well separated
to avoid this ACL collision

 $ set | grep -i ^home
HOME=/home/matzeri
HOMEDRIVE=C:
HOMEPATH='\Users\matzeri'