[Freeipa-devel] [DRAFT2] Per-domain DNS update permissions

[Martin Kosek]

On 06/18/2012 05:37 PM, Rob Crittenden wrote:
> Martin Kosek wrote:
>> On Fri, 2012-06-15 at 10:15 -0400, Simo Sorce wrote:
>>> On Fri, 2012-06-15 at 15:22 +0200, Martin Kosek wrote:
>>>> Hello all,
>>>>
>>>> In a scope of ticket 2511 I would like to implement an ability to
>>>> delegate a DNS update permissions to chosen user (or host) without
>>>> having to give the user full "Update DNS Entries" privileges, i.e.
>>>> allow
>>>> him to modify any DNS zone or record.
>>>>
>>>> So far, this is what I would like to do (comments welcome):
>>>>
>>>> 1) Create new objectclass "idnsManagedZone" with "managedBy" attribute
>>>> in MAY list
>>>> 2) Create new DNS commands:
>>>>    a] dnszone-add-managedby [--users=USERS] [--hosts=HOSTS]
>>>>    b] dnszone-remove-managedby [--users=USERS] [--hosts=HOSTS]
>>>>    - these commands would add/remove chosen user/host DN to managedBy
>>>> attribute in chosen DNS zone
>>>> 3) Add new generic ACIs to cn=dns,$SUFFIX:
>>>> aci: (target = "ldap:///idnsname=*,cn=dns,$SUFFIX")(version 3.0;acl
>>>> "Users and hosts can add DNS entries";allow (add) userattr =
>>>> "parent[1].managedby#USERDN";)
>>>> ... add similar ACIs for UPDATE, REMOVE access
>>>>
>>>> With these steps done, all that an administrator would need to do to
>>>> delegate a management of a DNS zone "example.com" is to run this
>>>> command:
>>>> $ ipa dnszone-add-managedby example.com --users=fbar
>>>>
>>>> The only downside I found so far is that the user would already need to
>>>> have "Read DNS Entries" permission assigned, otherwise he would not be
>>>> able to actually read DNS entries (allow rules can't take precedence
>>>> over deny rule we implemented to deny public access to DNS tree).
>>>>
>>>> An admin could of course create a special privilege and role with just
>>>> "Read DNS Entries" permission and then assign it to relevant
>>>> users/groups, but this looks awkward. Any idea to make this simpler?
>>>> Maybe creating a group "dns readers" by default which would allow such
>>>> access?
>>>
>>> Change the deny rule to deny to everyone except the user in
>>> "parent[1].managedby#USERDN" ?
>>>
>>> Simo.
>>>
>>
>> Good idea, I will do that. I will just use
>> "parent[0,1].managedby#USERDN" so that user can also read the zone
>> record. This way, a selected user will have read/write access to the
>> chosen zone only, which is exactly what we want to achieve.
> 
> Yes, this sounds workable to me too.
> 
> rob
> 

There were some second thoughts about the proposed design, which I would
like to discuss so that we can eventually accept another (better)
solution for this feature.

The main concern here was that proposed solution (based on user list in
managedBy attribute in DNS zone) is not in line with the rest of
permission&privilege architecture in IPA.

Here is another idea how to address the feature (I tested it and it
would work):
1) Get rid of the deny rule on cn=dns,$SUFFIX by modifying global access
rule (a working patch attached) to avoid current and future issues with
extending ACIs (deny rules are evil).

2) Add new Managed Entry Definition and Template to automatically add
"Manage DNS zone $idsname" permission. These could be used with standard
IPA privileges, roles and thus could be assigned to users, groups,
hosts, hostgroups...

3) New DNS zone managedBy attribute won't be manageable by user, but it
will hold a DN of the managed Permission entry

4) Add the following ACIs to cn=dns,$SUFFIX:
aci: (targetattr = "*")
(version 3.0; acl "Read DNS entries"; allow (read,search,compare)
userattr = "parent[0,1].managedby#GROUPDN";)

aci: (target = "ldap:///idnsname=*,cn=dns,$SUFFIX")
(version 3.0;acl "Add dns entries";allow (add)
userattr = "parent[1].managedby#GROUPDN";)

aci: (target = "ldap:///idnsname=*,cn=dns,$SUFFIX")
(version 3.0;acl "Remove DNS entries";allow (delete)
userattr = "parent[1].managedby#GROUPDN";)

aci: (targetattr = "idnsname || cn || idnsallowdynupdate || dnsttl ||
dnsclass || arecord || aaaarecord || a6record || nsrecord || cnamerecord
|| ptrrecord || srvrecord || txtrecord || mxrecord || mdrecord   ||
hinforecord || minforecord || afsdbrecord || sigrecord || keyrecord ||
locrecord || nxtrecord ||     naptrrecord || kxrecord || certrecord ||
dnamerecord || dsrecord || sshfprecord || rrsigrecord || nsecrecord ||
idnsname || idnszoneactive || idnssoamname || idnssoarname ||
idnssoaserial || idnssoarefresh || idnssoaretry || idnssoaexpire ||
idnssoaminimum || idnsupdatepolicy || idnsallowquery ||
idnsallowtransfer || idnsallowsyncptr || idnsforwardpolicy ||
idnsforwarders")
(target = "ldap:///idnsname=*,cn=dns,$SUFFIX")(version 3.0;acl "Update
DNS Entries";allow (write) userattr = "parent[0,1].managedby#GROUPDN";)

I needed to add permission DN to the managedBy attribute so that I could
create just one set of generic ACIs without having to create a set of
ACIs for every new zone and thus let users with "Update DNS entries"
permission have a write access to the "aci" attribute.

Would this design be better than the previous one? Comments welcome.

Thanks,
Martin
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