Re: ACL using netgroups

[Pierangelo Masarati <ando@sys-net.it>]

Claudio Strizzolo wrote:
> > > Checking configuration files for slurpd: /etc/openldap/userauth.acl:
> > > line 82: group "cn=linuxa,ou=netgroup,dc=example,dc=com":
> > > inappropriate syntax: 1.3.6.1.1.1.0.0
> > > <access clause> ::= access to <what> [ by <who> <access> [ <control> 
> > > ] ]+
> >
> > Could you please post a few sample lines of cn=linuxa 
>
> Here they are:
>
> # linuxa, netgroup, example.com
> dn: cn=linuxa,ou=netgroup,dc=example,dc=com
> objectClass: nisNetgroup
> objectClass: top
> cn: linuxa
> nisNetgroupTriple: (pclx01.example.com,-,-)
> nisNetgroupTriple: (pclx02.example.com,-,-)
> nisNetgroupTriple: (pclx03.example.com,-,-)
> (...)
As already pointed out by Kurt, the "group" access requires the member 
attr to have DN syntax (or, as an exception, nameUID syntax: that of 
uniqueMember, in short, for historical reasons).  The syntax of 
nisNetgroupTriple is 1.3.6.1.1.1.0.0 which is not DN syntax.  Moreover, 
the nisNetgroupTriple does not provide an equality rule, which means it 
wouldn't be possible to compare instances of it, assuming one can 
extract the hostname portion.

I don't see a clear solution to your problem which does not include 
hacking the code.  Perhaps you should consider redesigning your database 
and your access control olicies: if you want to use grouping for access 
control purposes, you should use LDAP groups ("groupOfNames" abjectClass 
and "member" attribute); in any case, you shouldn't use peernames in 
access control, as that require reverse lookups which are inherently 
unsafe and thus inappropriate for access control which is related to 
security.  You should rather require authentication (any client which 
doesn't support authentication shouldn't even be considered), and group 
user DNs for access control purposes.

If you really really need to live with using netgroups for 
authentication, you could develop a "dynacl" module; there's an example 
in contrib/slapd-modules/acl/ which allows grouping in terms of posix 
groups, based on the uidNumber.  That plugin is not meant for 
production, nor it should be seen as a valid idea to base access control 
design on, but just as an example of how to code custom access checking.

p.



Ing. Pierangelo Masarati
OpenLDAP Core Team

SysNet s.n.c.
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