Security Identifier (SID) to User Identifier (uid) Resolution System

[Cole, Timothy D.]

> -----Original Message-----
> From:	Luke Kenneth Casson Leighton [SMTP:lkcl at samba.org]
> Sent:	Tuesday, January 04, 2000 20:20
> To:	Cole, Timothy D.
> Cc:	Multiple recipients of list SAMBA-TECHNICAL
> Subject:	RE: Security Identifier (SID) to User Identifier (uid)
> Resolution  System
> 
> > > > 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
> > > and
> > > > > 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
> > > kernel
> > > > > 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
> > > implementation,
> > > > but
> > > > would it be possible to make the default 'nobody' SID mapping
> > > configurable
> > > > 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
> > > one
> > > 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.
> 
> 
> samba uses nobodty, by default, as the guest user.
> 
	Doh, you're right.  Yes, that wouldn't do at all then.  I'm too used
to the specific configuration here -- HP-UX doesn't ALLOW anything to become
uid -2 (we had to create a separate guest account for samba).