[Samba] Samba4, idmap.ldb & ID_TYPE_BOTH

Rowland Penny rowlandpenny at googlemail.com
Sat Feb 21 14:37:59 MST 2015

On 21/02/15 19:26, Andrew Bartlett wrote:
> On Thu, 2015-02-19 at 17:15 +0000, Rowland Penny wrote:
>> This all leads me to my questions, why, when it comes to idmap.ldb,
>> can
>> a user also be a group and a group can also be a user and why was it
>> setup like this in the first place ? , there must be a reason for it.
> It goes like this:
>   - Groups can own files (there are groups like domain administrators
> that own files in sysvol)

Does domain administrators own the files ? as I posted earlier, trying 
to reset sysvol is failing for me and the relevant part of the ACL is this:


This is the start of the ACL and if we expand it for better reading 
'O:LA' 'G:DA 'D:P(A;OICI'. The first part is the owner, the second is 
the group and the third is the start of the ACEs. So the owner (O) is LA 
which is 'Local Administrator' and the group (G) is DA which is 'Domain 
Administrators' , as I read it, Domain Administrators doesn't own the 
files, or am I missing something?
>   - We don't (eg in sidHistory, or when files are migrated, preserving
> permissions, from a workstation or from a domain that is not trusted)
> always know if an incoming SID is a user or group.

does windows know from the SID what the object is? and if not, what does 
windows do?

>   - Working out if an arbitrary SID is a user or group takes time and
> network operations, which may fail.  ID_TYPE_BOTH is both fast and
> deterministic in this respect.

And in my opinion (which is worth very little) it is a kludge, also does 
a group actually try to connect (note, I do not know if this happens, 
which is why I am asking) and if so how ? a group doesn't have a 
password so how can it authenticate?

> My view is that we should always have mapped SIDs to both a UID and GID,
> and I understand that in general, we are doing that now in new backends.
> See for example idmap_rid and idmap_autorid.
> The only tricky bit is that while a user can be put in an extra group to
> pick up any permissions assigned to it as a group, a group can't get
> user-based permissions, so can't obtain the extra rights associated with
> file ownership.

Again I ask, what file ownership? can you please name a file that a 
windows group owns, sorry if I am coming across as negative here, but I 
am struggling to understand just how a group can own files, I am used to 
files belonging to a user and members of a group being allowed access to 


> Andrew Bartlett

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