Security Identifier (SID) to User Identifier (uid) Resolution
Cole, Timothy D.
timothy_d_cole at md.northgrum.com
Tue Jan 4 21:47:15 GMT 2000
> -----Original Message-----
> From: Cole, Timothy D.
> Sent: Tuesday, January 04, 2000 16:39
> To: Multiple recipients of list SAMBA-TECHNICAL
> Subject: RE: Security Identifier (SID) to User Identifier (uid)
> Resolution System
> > -----Original Message-----
> > From: Steve Langasek [SMTP:vorlon at netexpress.net]
> > Sent: Tuesday, January 04, 2000 15:04
> > To: Cole, Timothy D.
> > Cc: Multiple recipients of list SAMBA-TECHNICAL
> > Subject: RE: Security Identifier (SID) to User Identifier (uid)
> > Resolution System
> > On Wed, 5 Jan 2000, Cole, Timothy D. wrote:
> > > On another note, although it's not really relevent to Samba, over
> > > the holiday I was actually pondering sticking a SURS-like table in a
> > hidden
> > > inode on an ext2/3 filesystem, mapping between uids/gids on the disk
> > > SIDs. The kernel patch would also include a SURS-like mapping table
> > > in-kernel, which would map between SIDs and "system" uids/gids (which
> > might
> > > well be different from those on disk).
> > > The kernel table would be filled out from userspace, having a few
> > > initial entries for root and the like hard-coded. SIDs with no
> > > entry would map to uid/gid -2 (nobody), until such time as a mapping
> > were
> > > added from userspace. Mapping between fs uids/gids and "system"
> > uids/gids
> > > would be done by the filesystem driver, so none of the existing
> > interfaces
> > > would really have to change -- no hits from comparing SIDs everywhere,
> > it's
> > > still all word-size integers.
> > Intriguing. It's probably not that important for a first
> > but
> > would it be possible to make the default 'nobody' SID mapping
> > via
> > a mount option?
> Hmm, that's a good idea. Yes, I would think it'd be trivial to do.
> The actual kernel table lookup (which would be independent of the
> filesystems) would still return -2, but since the fs driver would be the
> doing the lookup, it could return whatever uid/gid it wanted in that case.
> Or, better, the lookup function could take a parameter for the
> uid/gid to fall back on, which would of course be supplied by the caller,
> normally fs driver. Yes, that seems like a better design to me.
Luke has a point though (I just read and responded to his message);
you don't really want to squash a bunch of SIDs into the same user.
-2/nobody isn't really a user, so that's not quite the same thing.
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