Will all SIDs fit into |SECURITY_MAX_SID_SIZE| bytes ? / was: Re: Switching groups with newgrp - how to get the new group with |GetTokenInformation()| ?

[Corinna Vinschen]

On Feb 24 15:38, Roland Mainz via Cygwin wrote:
> On Thu, Feb 22, 2024 at 8:11 PM Corinna Vinschen via Cygwin
> <cygwin@cygwin.com> wrote:
> > On Feb 22 18:38, Roland Mainz via Cygwin wrote:
> > > If I switch the current user's group with /usr/bin/newgrp, how can a
> > > (native) Win32 process use
> > > |GetTokenInformation(GetCurrentThreadToken(), ...)| to find out which
> > > group is the new "current group" (e.g. which |TokenInformationClass|
> > > should I use) ?
> >
> >   PSID sidbuf = (PSID) alloca (SECURITY_MAX_SID_SIZE);
> [snip]
> 
> Win32/NT API question: All known SIDs will fit into
> |SECURITY_MAX_SID_SIZE| bytes, right ? I'm asking because right now
> the ms-nfs41-client code assumes that all SIDs use a variable amount
> of memory, and we always have to ask the Win32/NT API about the number
> of bytes to allocate. If |SECURITY_MAX_SID_SIZE| is the global maximum
> limit for all Windows versions, then we could simplify the code a
> lot...

Yes.  ACLs are size restricted to 64K, though, but that shouldn't be
much of a problem usally.


Corinna