Re: [Patch] Allow to disable root privileges with CYGWIN=noroot

[Christian Franke <Christian dot Franke at t-online dot de>]

Corinna Vinschen wrote:
> If you plan to run a Cygwin application with restricted rights from your
> administrative account, the IMHO right way would be to start the Cygwin
> application through another application which creates a *really*
> restricted user token using the Win32 function CreateRestrictedToken and
> then call cygwin_set_impersonation_token/execv to start the restricted
> process.  A Cygwin tool which accomplishes that would be much more
> useful and much more generic than this patch, IMHO.
>
>   
I agree, let's forget the patch.

But I'm not sure how cygwin_set_impersonation_token() could be of any 
help here. This function sets user.external_token which is only used in 
seteuid32(). Setuid/seteuid() cannot be used because the restricted 
token is not related to another user id.

A quick test with native calls works for me:

 HANDLE t, rt;
 OpenProcessToken (GetCurrentProcess (), TOKEN_ALL_ACCESS, &t);
 CreateRestrictedToken (t, DISABLE_MAX_PRIVILEGE, 0, ..., 0, &rt);
 CreateProcessAsUser (rt, 0, "c:/cygwin/bin/mintty...", ...);

BTW: CreateRestrictedToken is apparently missing in 
/usr/include/w32api/*.h, but it is present in libadvapi32.a

Christian