From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <corinna@sourceware.org>
Received: by sourceware.org (Postfix, from userid 2155)
	id DD9983858295; Mon,  4 Mar 2024 10:26:14 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org DD9983858295
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cygwin.com;
	s=default; t=1709547974;
	bh=twcPHXQTOdFpIIZehLE1ztAiPqKiPGeJHFlMhvN44Es=;
	h=Date:From:To:Subject:Reply-To:References:In-Reply-To:From;
	b=QDG+EmbOp8fMVMd+BkXgXeW0WjnFPvg3ZNsyq1ymyx6OozidDCvLC4U2plkzCGz9z
	 5A5Mliyn510/XjClFFbgLH2Z1EEC71UyjHxcog5KBfvQZdHOt1llOmuSkKB96Pf2da
	 DO3JKihvSE6vIL52oA9VOFWJTHp6r9dTUohlaDtk=
Received: by calimero.vinschen.de (Postfix, from userid 500)
	id E86FDA8063B; Mon,  4 Mar 2024 11:26:12 +0100 (CET)
Date: Mon, 4 Mar 2024 11:26:12 +0100
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: UNIX nobody/nogroup mapping to which Windows SID/account?
Message-ID: <ZeWhxD_jfjaIocLI@calimero.vinschen.de>
Reply-To: cygwin@cygwin.com
Mail-Followup-To: cygwin@cygwin.com
References: <CANH4o6P_ONdFmMoAuOP8RbCQ0XEWagdPVeM7chY3B1CfJ5hAAw@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <CANH4o6P_ONdFmMoAuOP8RbCQ0XEWagdPVeM7chY3B1CfJ5hAAw@mail.gmail.com>
List-Id: <cygwin.cygwin.com>

On Mar  3 14:45, Martin Wege via Cygwin wrote:
> Hello,
> 
> How can we map UNIX "nobody"/"nogroup" to Win32 SIDs/accounts? Cygwin
> has entries for "nobody" in /etc/passwd and "nogroup" in /etc/group,
> but these accounts have SIDs returned by /usr/bin/getent passwd and
> /usr/bin/getent group which LookupAccountSidA() does not recognise.
> 
> So what is the correct Win32 solution?

I urge you to read the entire thread starting at

https://sourceware.org/legacy-ml/cygwin/2016-06/msg00347.html

There's a *LOT* of information in there in terms of discussing and
creating the nobody/nogroup mapping.

Bottom line is, there's no nobody account equivalent on Windows and no
resolvable SID/Name pair.  Thus, we decided to use the SID S-1-0-65534
mapped to uid/gid 65534 for this purpose.  This doesn't matter to native
Windows, it's just some foreign SID.  But it's resolvable inside Cygwin:

  $ getent passwd S-1-0-65534
  no+body:*:65534:65534:U-no\body,S-1-0-65534:/:/sbin/nologin
  $  getent group S-1-0-65534
  no+body:S-1-0-65534:65534:


Corinna