openssh unix dev - Dec 2016 - Seeking assistance with pubkey authentication problem on Windows OS

Hello.

I did a bit more digging in the debug information and I have isolated the
problem, which looks like it comes directly from the source code.?
The ssh-agent.log shows the following entries during my ssh connection attempt
from the Linux machine to the Windows machine running a Win64 OpenSSH:

5772 16:13:37 990 debug1: trying public key file
C:\Users\LAW/.ssh\authorized_keys
5772 16:13:37 990 debug1: given public key is not mapped to user LAW
(profile:C:\Users\LAW)

My sshd_config file has been set with the following entry:
AuthorizedKeysFile?.ssh\authorized_keys

I have noticed that if I was to?either use the line
AuthorizedKeysFile %h\.ssh\authorized_keys
or
AuthorizedKeysFile?C:\Users\LAW\.ssh\authorized_keys
the?ssh-agent.log shows a debug entry now saying?
trying public key file C:\Users\LAW/C:\Users\LAW\.ssh\authorized_keys

Having had a dig around in the source-code for OpenSSH, the culprit is the
subroutine
expand_authorized_keys
in the file auth.c
which returns a char pointer called ret given by snprintf(ret, sizeof(ret),
"%s/%s", pw->pw_dir, file)
You can see here that the formatting?"%s/%s" is causing the insertion
of a forward-slash in the?public key filename used in the windows environment;
to this extent, the?authorized_keys?file will never be found in the windows
environment.

Would it suffice if I rebuild the Win64 OpenSSH executables with the
correction?snprintf(ret, sizeof(ret), "%s\\%s", pw->pw_dir, file),
or should I wait for an official build with this correction?


Yours sincerely,
Peter.

___________________________________________________________

Dr. Peter E. Lawrence? BSc(Ma & Comp Sc)(Hons) MSc(Ma Sc)(Res) PhD(Ma Sc)
Analyst & Software Engineer
BELGOCONTROL?(CANAC) 
Tervuursesteenweg?303 
B?-?1820?Steenokkerzeel 
Tel:?[Office]:? +32?2?206?2588
?????? [GSM]:? ?+32 4 701 80752
Email: law at belgocontrol.be
Web:??www.belgocontrol.be
?

Belgocontrol Mail Disclaimer

Please file an issue at https://github.com/PowerShell/Win32-OpenSSH. The
Windows fork is not part of the main OpenSSH project yet.

Otherwise, you may work around your issue by getting rid of this
configuration line:
AuthorizedKeysFile %h\.ssh\authorized_keys

It would default to %userprofile%\.ssh\authorized_keys.


On Wed, Dec 14, 2016 at 7:34 AM, Peter_Lawrence at belgocontrol.be <
Peter_Lawrence at belgocontrol.be> wrote:
> Hello.
>
> I did a bit more digging in the debug information and I have isolated the
> problem, which looks like it comes directly from the source code.
> The ssh-agent.log shows the following entries during my ssh connection
> attempt from the Linux machine to the Windows machine running a Win64
> OpenSSH:
>
> 5772 16:13:37 990 debug1: trying public key file
> C:\Users\LAW/.ssh\authorized_keys
> 5772 16:13:37 990 debug1: given public key is not mapped to user LAW
> (profile:C:\Users\LAW)
>
> My sshd_config file has been set with the following entry:
> AuthorizedKeysFile .ssh\authorized_keys
>
> I have noticed that if I was to either use the line
> AuthorizedKeysFile %h\.ssh\authorized_keys
> or
> AuthorizedKeysFile C:\Users\LAW\.ssh\authorized_keys
> the ssh-agent.log shows a debug entry now saying
> trying public key file C:\Users\LAW/C:\Users\LAW\.ssh\authorized_keys
>
> Having had a dig around in the source-code for OpenSSH, the culprit is the
> subroutine
> expand_authorized_keys
> in the file auth.c
> which returns a char pointer called ret given by snprintf(ret,
> sizeof(ret), "%s/%s", pw->pw_dir, file)
> You can see here that the formatting "%s/%s" is causing the
insertion of a
> forward-slash in the public key filename used in the windows environment;
> to this extent, the authorized_keys file will never be found in the windows
> environment.
>
> Would it suffice if I rebuild the Win64 OpenSSH executables with the
> correction snprintf(ret, sizeof(ret), "%s\\%s", pw->pw_dir,
file), or
> should I wait for an official build with this correction?
>
>
> Yours sincerely,
> Peter.
>
> ___________________________________________________________
>
> Dr. Peter E. Lawrence  BSc(Ma & Comp Sc)(Hons) MSc(Ma Sc)(Res) PhD(Ma
Sc)
> Analyst & Software Engineer
> BELGOCONTROL (CANAC)
> Tervuursesteenweg 303
> B - 1820 Steenokkerzeel
> Tel: [Office]:  +32 2 206 2588
>        [GSM]:   +32 4 701 80752
> Email: law at belgocontrol.be
> Web:  www.belgocontrol.be
>
>
> Belgocontrol Mail Disclaimer
> _______________________________________________
> openssh-unix-dev mailing list
> openssh-unix-dev at mindrot.org
> https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev
>