[389-users] Re: ACI limiting read to groups a user is member of

[Grant Byers]

On 18/2/20 7:56 am, William Brown wrote:
> > On 17 Feb 2020, at 19:25, thierry bordaz <tbordaz(a)redhat.com&gt; wrote:
> >
> >
> >
> > On 2/17/20 5:26 AM, Grant Byers wrote:
> >> Got it..
> >>
> >>
> >> (userattr = "uniqueMember#USERDN")
> > It allows  a member of a groupofUniqueName to read/search that group. If you are also
> supporting GroupofName groups you may want to add the bind rule
> (userasttr="member#userDN").
> > With this rule, targetfilter is useless and you may remove it as it is quite
> expensive to evaluate.
>  I'm still not 100% on what Grant's goal is here Thierry. I don't know if
> it's "anyone can read groups" or "can only read groups you are a member
> of".
>
>  I'd also say what's your threat/risk model. Knowledge of group membership is not
> a security risk, so a simple rule like what I proposed (all read member/memberUid) for
> anyone is probably fine ...
>
>  Anyway, if you want more advice Grant, I think we need to know exactly what you want to
> achieve :)
>
>  Thanks
>  

All sorted yesterday, thanks. And yes, I'm only allowing users to see 
groups they are a member of (we're only using groupofuniquenames 
w/memberof).


Whilst group membership exposure may not be a direct security risk 
itself, it is information disclosure. If someone wants to do something 
nefarious, one of the first things they're going to do is look at what 
users have which access. We'd like to limit that in our environment, and 
have done now. I like these bind types. They're neat.


> > best regards
> > thierry
> >>
> >> Thanks!
> >>
> >> On 17/2/20 2:02 pm, Grant Byers wrote:
> >>> On 17/2/20 1:24 pm, William Brown wrote:
> >>>>> On 17 Feb 2020, at 12:19, Grant Byers
> <Grant.Byers(a)aarnet.edu.au&gt; wrote:
> >>>>>
> >>>>> Hi,
> >>>>>
> >>>>> In an effort to tighten search and read permissions on our internal
> >>>>> directory server, we've limited accounts to read certain
> attributes of
> >>>>> "self". They have search on the entire tree, but otherwise
> no read
> >>>>> perms. This is all well and good for clients that utilize the
> memberOf
> >>>>> attribute of self, but not so good for applications that utilize
> >>>>> memberUid, or insist on searching for groupOfUniqueNames or
> >>>>> groupOfNames  then enumerating them programmatically to determine
> which
> >>>>> groups the user belongs to after binding as the user.
> >>>>>
> >>>>> So. I've been reading docs and haven't been able to find
> anything, but I
> >>>>> was wanting to do something like this;
> >>>>>
> >>>>>
> >>>>> dn: ou=groups,dc=example,dc=com
> >>>>> aci: (targetattr = "*")
> >>>>>     (targetfilter =
> "(&(objectClass=groupOfUniqueNames)(uniqueMember={{rdn
> >>>>> of self}})")
> >>>>>     (version 3.0; acl "Allow authenticated users to read own
> group
> >>>>> membership"; allow (read,compare,search)
> >>>>>     (userdn="ldap:///all");)
> >>>>>
> >>>>>
> >>>>> where the target filter limits results to only those that match
> >>>>> uniqueMember={{rdn of self}}
> >>>>>
> >>>>>
> >>>>> Is this possible?
> >>>> Yes, but I'd suggest you tighten it up a bit. targetattr = * is
> really dangerous, it really means everything, including internal system attributes.
> >>>>
> >>>> You probably want "(targetattr = "objectClass || uniquemember
> || cn || memberUid || member || memberOf")(targetfilter = "....")
> >>>>
> >>>> There is a section in the redhat ds guide that may help a lot
> >>>>
> >>>>
> https://access.redhat.com/documentation/en-us/red_hat_directory_server/10...
> >>>>
> >>>> In general, keep your aci's as targeted and as specific as
> possible.
> >>>>
> >>>> I'm very happy to review these further if you need :)
> >>> For sure, I'll definitely be restricting attributes (as I have done
> with
> >>> other targeted ACIs).  I'm working toward least privilege.
> >>>
> >>>
> >>> I've reviewed that doco multiple times now, but still don't see how
> this
> >>> is possible. I must be missing something! I assume it has to be
> >>> targetfilter. Am I to do something like this?
> >>>
> >>>
> >>> (targetfilter =
> "(&(objectClass=groupOfUniqueNames)(uniqueMember=ldap:///self?dn)")
> >>>
> >>>
> >>> Thanks,
> >>>
> >>> Grant
> >>>
> >>>
> >>>>> Thanks,
> >>>>> Grant
> >>>>> _______________________________________________
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> >>>> —
> >>>> Sincerely,
> >>>>
> >>>> William Brown
> >>>>
> >>>> Senior Software Engineer, 389 Directory Server
> >>>> SUSE Labs
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>  —
>  Sincerely,
>
>  William Brown
>
>  Senior Software Engineer, 389 Directory Server
>  SUSE Labs
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