From: Roland Mainz <roland.mainz@nrubsig.org>
To: cygwin@cygwin.com
Subject: Re: Will all SIDs fit into |SECURITY_MAX_SID_SIZE| bytes ? / was: Re: Switching groups with newgrp - how to get the new group with |GetTokenInformation()| ?
Date: Sun, 25 Feb 2024 22:04:29 +0100 [thread overview]
Message-ID: <CAKAoaQmL4wQ526dQ_-ASHCMum8L2sKiR_LnP-ba+R+39ZCMKVw@mail.gmail.com> (raw)
In-Reply-To: <Zdo8B-IhG_dYAjGo@calimero.vinschen.de>
On Sat, Feb 24, 2024 at 7:57 PM Corinna Vinschen via Cygwin
<cygwin@cygwin.com> wrote:
>
> 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.
Erm... why ACLs? I was asking about the memory allocation size for an SID.
Example:
Right now our code uses two calls to |LookupAccountNameA()| for the
conversion from a Windows account name to Windows SID.
The first call gets the allocation size for a SID, our code then
allocates that memory, and then does a second call to
|LookupAccountNameA()| to fill that memory with that SID.
If |SECURITY_MAX_SID_SIZE| (currently 68 bytes) is the maximum memory
size a Windows syscall can return for a SID, then the code above could
be simplified to a |sidmem =
malloc(SECURITY_MAX_SID_SIZE)|+|LookupAccountNameA(..., sidmem, ...)|.
The same could be done in many many other places, leading to a
considerable reduction of Win32 system library calls.
Question is whether the assumption about |SECURITY_MAX_SID_SIZE| is correct...
----
Bye,
Roland
--
__ . . __
(o.\ \/ /.o) roland.mainz@nrubsig.org
\__\/\/__/ MPEG specialist, C&&JAVA&&Sun&&Unix programmer
/O /==\ O\ TEL +49 641 3992797
(;O/ \/ \O;)
next prev parent reply other threads:[~2024-02-25 21:04 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-22 17:38 Roland Mainz
2024-02-22 19:11 ` Corinna Vinschen
2024-02-23 13:03 ` Roland Mainz
2024-02-23 15:47 ` Corinna Vinschen
2024-02-23 18:45 ` Roland Mainz
2024-02-23 21:15 ` Dan Shelton
2024-02-24 13:11 ` Corinna Vinschen
2024-03-05 22:38 ` Dan Shelton
2024-03-06 13:01 ` Corinna Vinschen
2024-03-09 21:26 ` Glenn Strauss
2024-03-11 1:30 ` Dan Shelton
2024-03-11 3:49 ` Brian Inglis
2024-03-11 16:54 ` Corinna Vinschen
2024-03-11 1:28 ` Dan Shelton
2024-03-11 16:56 ` Corinna Vinschen
2024-04-19 23:44 ` Dan Shelton
2024-04-26 9:04 ` Andrey Repin
2024-02-24 16:57 ` Brian Inglis
2024-02-24 12:53 ` Corinna Vinschen
2024-02-24 14:38 ` Will all SIDs fit into |SECURITY_MAX_SID_SIZE| bytes ? / was: " Roland Mainz
2024-02-24 18:57 ` Corinna Vinschen
2024-02-25 21:04 ` Roland Mainz [this message]
2024-02-25 22:32 ` gs-cygwin.com
2024-02-26 4:17 ` gs-cygwin.com
2024-02-26 16:12 ` [EXTERNAL] " Lavrentiev, Anton (NIH/NLM/NCBI) [C]
2024-02-26 9:20 ` Corinna Vinschen
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