Generic cred APIs (RE: Security Identifier (SID) ...)

Nicolas Williams Nicolas.Williams at
Wed Jan 5 21:29:29 GMT 2000

On Thu Jan 06 2000, Cole, Timothy D. (timothy_d_cole at wrote:
> > -----Original Message----- 
> > From: Luke Kenneth Casson Leighton [SMTP:lkcl at] 
> > Sent: Wednesday, January 05, 2000 11:59 
> > To: 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: 
> > 
> > AH! you're talking about a _kernel_ level implemntation that uses this 
> > stuff, not samba. 
> > 
>         Yes; that's what I meant when I said I was getting off on a tangent 
> :) 
> > ok... having created a uid / gid, it's permanent, so it's ok. ither 
> > representations are then nothing to do with this. it's _external_ 
> > representiations that, say, samba or winbind use, that sid/uid converion 
> > becomes imprtant. 
> > 
>         Pretty much. The kernel table would more likely be (indirectly) 
> updated from winbind or whatnot, rather than the other way around. The main 
> clever thing that would allow would be using uids and gids even with a 
> mounted NTFS filesystem, and everything still working as expected. 

There was a thread before this one in the XAD list which started when
Luke Howard asked wether Luke Leighton really did want "SIDs in the
kernel". Out of that thread came Luke's SURS proposal and then the
thread moved here.

What we really need is generic credential-type neutral APIs for:

 - getting/setting process credentials (think effective vs. real

 - getting/setting a file's credentials (thing stat/chown/chgrp/chmod)

 - NSS APIs for resolving user/groupnames and credentials to each other

 - Kernel APIs for filesystem drivers to compare process credentials to
   file credentials; to copy process credentials to a file; etc...

This means that kernels should support more than one type of credential
per-process and, therefore, that they should store those credentials.

This is motivated by the superiority of SIDs to POSIX UIDs/GIDs.

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