I think we completely missed my earlier point. My question was around
whether we need to have exceptions in Deny and Allow beyond just Allow or
Deny policy items. I used the MSFT example to see if they have implemented
exceptions to Deny, which I did not find any. I am not suggesting that we
ask the users to order the policies and Ranger follow the order.
We can open a separate thread on whether Ranger needs to use an explicit
hierarchy for policy evaluation or not. For the current discussion, I don't
see a specific use case where we would need a deny or allow exception and
not fulfilled by just allow or deny functionality.
Let us take the use case we discussed earlier. The group "interns" got
denied,but we want to exclude one user ("Scott") from that, I am suggesting
to have the particular user ("Scott") included in the Allow section of
policy and group "interns" included in Deny section of the same policy.
Ranger should evaluate the both Allow and Deny in the same policy and
deduce that user "Scott" can access the resource while anyone else in group
"interns" is denied to access the resource. The policy creation in the UI
is much simpler than having to specify "Scott" as an exception to Deny and
then specifying "Scott" for Allow.
On Wed, Oct 14, 2015 at 11:36 AM, Madhan Neethiraj <
[email protected]> wrote:
> Microsoft DACL also talks about exceptions, but the model relies on the
> users to setup ACE in specific order – see below.
>
> From
> https://msdn.microsoft.com/en-us/library/windows/desktop/aa446597(v=vs.85).aspx
> :
>
> "In most cases, you can control access to an object by using
> access-allowed ACEs; you do not need to explicitly deny access to an
> object. The exception is when an ACE allows access to a group and you want
> to deny access to a member of the group. To do this, place an access-denied
> ACE for the user in the DACL ahead of the access-allowed ACE for the group.
> Note that the order of the ACEs
> <https://msdn.microsoft.com/en-us/library/windows/desktop/aa379298(v=vs.85).aspx>
> is
> important because the system reads the ACEs in sequence until access is
> granted or denied. The user's access-denied ACE must appear first;
> otherwise, when the system reads the group's access allowed ACE, it will
> grant access to the restricted user."
>
> This approach of relying on ordering of policy items (equivalent of ACEs
> above) can work for Ranger as well. However Microsoft DACL model evaluates
> only one DACL to determine access to an object; compare this with Ranger
> where there could be multiple policies that can be evaluated for a resource
> – for example to determine access to a finance.invoice.ssn column, Ranger
> would evaluate policies that are applicable for finance database,
> finance.invoice table and finance.invoice.ssn column. To guarantee
> consistent authorization result, that relies on proper ordering of
> allow/deny policy items in each policy, would require the policies to be
> evaluated in a specific order – either most-specific-to-most-generic
> (column policy, table policy, database policy) or most-generic-to
> most-specific. And it might be very challenging, if not impossible, to
> ensure a policy order given our support for wildcard specification – for
> example, should a policy for “/finance/*2015/*” be evaluated before a
> policy for “/finance/invoice*/*” while determining access for a file named
> “/finance/invoice2015/vendor1.txt”?
>
> I think this approach would make the policy authoring very difficult and
> confusing, in addition to being not able to support certain scenarios like
> “deny at a higher level (like for a database), even if access might be
> allowed at a lower level (for a table/column)”, “allow at a higher level,
> but deny at a lower level). The current implementation (in tag-policy
> branch of Ranger) is much less confusing and offers building blocks that
> can be used to support more usecases and can guarantee consistent results
> for a given set of policies. If we are after simplicity, the DACL model
> does not seem to be the right choice..
>
> Thanks,
> Madhan
>
>
> From: Balaji Ganesan
> Reply-To: "[email protected]"
> Date: Wednesday, October 14, 2015 at 10:31 AM
>
> To: "[email protected]"
> Subject: Re: [DISCUSS] Policy model enhancement to support
> deny-conditions and exceptions
>
> >> My proposal is to just keep the policy to have only allow and deny with
> NO exceptions. In your use case, if we allow "finance" group and deny
> "intern" group, then anyone in intern group would not be allowed while
> everyone else in finance group will get access. If there is a person in
> intern group who needs access, then user need to be taken out of the intern
> group or we need to add only the users who specifically need to be denied.
>
> <<Users who are not comfortable with the idea of “excludes” can continue
> to use only allow and deny in the policies. Users who are comfortable with
> “excludes” can choose to use it to simplify their policy management.>>
>
> The question here is whether exceptions are really needed in the product.
> We need to keep the product simple
> Questions is what use cases can exceptions clearly solve above and beyond
> simply access grant and access deny policy line items. As an example, I am
> looking at MSFT for how they have have implemented deny-access
> https://msdn.microsoft.com/en-us/library/windows/desktop/aa446597(v=vs.85).aspx.
> The use case MSFT is trying to solve it denying access to specific users
> who are part of the group which is provided access. I think most of the
> deny-access use cases would be for specific users, not for large sets of
> groups.
>
>
> On Tue, Oct 13, 2015 at 11:47 PM, Madhan Neethiraj <
> [email protected]> wrote:
>
>> >> For argument sakes, finance could be the higher level group and intern
>> could be a sub group in a hierarchy. There could be n number of sub groups.
>> We could provide access by adding n-1 groups to the policy. We can argue
>> whether n<10 or n>50, depending on the answer it would make sense to add
>> all groups which needs access or specify deny groups which don't need access
>>
>> The groups may not fall into nice hierarchies – for example, interns
>> group might consist of users from various orgs in a company (not just from
>> finance group). In such cases, the only choice is to setup Ranger policies
>> with individual users (and not groups).
>>
>> >> My proposal is to just keep the policy to have only allow and deny
>> with NO exceptions. In your use case, if we allow "finance" group and deny
>> "intern" group, then anyone in intern group would not be allowed while
>> everyone else in finance group will get access. If there is a person in
>> intern group who needs access, then user need to be taken out of the intern
>> group or we need to add only the users who specifically need to be denied.
>>
>> Users who are not comfortable with the idea of “excludes” can continue to
>> use only allow and deny in the policies. Users who are comfortable with
>> “excludes” can choose to use it to simplify their policy management.
>>
>> Thanks,
>> Madhan
>>
>> From: Balaji Ganesan
>> Reply-To: "[email protected]"
>> Date: Tuesday, October 13, 2015 at 10:24 PM
>>
>> To: "[email protected]"
>> Subject: Re: [DISCUSS] Policy model enhancement to support
>> deny-conditions and exceptions
>>
>> <<Are you suggesting that the security admins create policies that list
>> individual users, instead of using groups? Wouldn’t that make security
>> administration more painful, in a reasonably large organization? For every
>> change in users role (or group) or an employee joining/leaving the org, all
>> security policies have to be reviewed and updated.. Many ACLs support both
>> users and groups to alleviate this issue.>>
>> For argument sakes, finance could be the higher level group and intern
>> could be a sub group in a hierarchy. There could be n number of sub groups.
>> We could provide access by adding n-1 groups to the policy. We can argue
>> whether n<10 or n>50, depending on the answer it would make sense to add
>> all groups which needs access or specify deny groups which don't need access
>>
>> My proposal is to just keep the policy to have only allow and deny with
>> NO exceptions. In your use case, if we allow "finance" group and deny
>> "intern" group, then anyone in intern group would not be allowed while
>> everyone else in finance group will get access. If there is a person in
>> intern group who needs access, then user need to be taken out of the intern
>> group or we need to add only the users who specifically need to be denied.
>>
>> On Tue, Oct 13, 2015 at 9:48 PM, Madhan Neethiraj <[email protected]>
>> wrote:
>>
>>> Balaji,
>>>
>>> >> why cannot user clearly specific users or groups that would need
>>> specific access. Why is there a need to give access to finance group as a
>>> whole when we know there is a subset of user who do not need access to the
>>> the finance database? or clearly specify users who need to be denied?
>>> Are you suggesting that the security admins create policies that list
>>> individual users, instead of using groups? Wouldn’t that make security
>>> administration more painful, in a reasonably large organization? For every
>>> change in users role (or group) or an employee joining/leaving the org, all
>>> security policies have to be reviewed and updated.. Many ACLs support both
>>> users and groups to alleviate this issue.
>>>
>>>
>>> From: Balaji Ganesan
>>> Reply-To: "[email protected]"
>>> Date: Tuesday, October 13, 2015 at 9:01 PM
>>>
>>> To: "[email protected]"
>>> Subject: Re: [DISCUSS] Policy model enhancement to support
>>> deny-conditions and exceptions
>>>
>>> Madhan, Fantastic job in putting together in the wiki. Thank you.
>>>
>>> We clearly need to show case use cases for deny exclude and allow
>>> exclude. In my opinion it is very confusing to user to construct such a
>>> policy
>>>
>>> <<Let’s say one of the users, scott who is in interns and finance
>>> groups, works on an assignment that requires select access to finance
>>> database. To enable this access, the authorization policy for the database
>>> should be updated by adding a deny-exclude, as shown below:>>
>>> In the wiki, we have created a "deny" policy for intern group and an
>>> exception for Scott. First of all, why cannot user clearly specific users
>>> or groups that would need specific access. Why is there a need to give
>>> access to finance group as a whole when we know there is a subset of user
>>> who do not need access to the the finance database? or clearly specify
>>> users who need to be denied? It is confusing to think about exceptions for
>>> deny, deny, exceptions for allow and allow.
>>>
>>>
>>> On Tue, Oct 13, 2015 at 2:43 PM, Madhan Neethiraj <[email protected]>
>>> wrote:
>>>
>>>> Bosco,
>>>>
>>>> Thanks for the review and comments. The wiki
>>>> <https://cwiki.apache.org/confluence/display/RANGER/Deny-conditions+and+excludes+in+Ranger+policies>
>>>> has been updated to address your comments. Please review.
>>>>
>>>> Thanks,
>>>> Madhan
>>>>
>>>> From: Don Bosco Durai
>>>> Reply-To: "[email protected]"
>>>> Date: Monday, October 12, 2015 at 6:20 PM
>>>> To: "[email protected]"
>>>> Subject: Re: [DISCUSS] Policy model enhancement to support
>>>> deny-conditions and exceptions
>>>>
>>>> Madhan, thanks for putting this document together. It is looking good.
>>>>
>>>> Can I make a few suggestions:
>>>>
>>>> 1. Call out each use case as separate section. E.g. 2.2.3 for "HDFS
>>>> policy that allows all finance group users to access contents of
>>>> /finance
>>>> folder, but denies access to users in interns group. Users in interns
>>>> group
>>>> will be denied the access even if they are part of finance group.”
>>>> 2. Can we also add a simple use case of global “Deny”. E.g Deny all
>>>> users from “interns” group from accessing table “Employees"
>>>> 3. The label “Exceptions”, can we make it more explicit. E.g.
>>>> “Exclude from Allow Conditions” and “Exclude from Deny Conditions”
>>>> 4. Probably one small paragraph to explain “Exceptions” will be
>>>> good. I think, this is sort of a new concept.
>>>> 5. Section 3 “Policy Evaluation”, it seems to be a flow chart. Can
>>>> we create flow chart diagram. It will be easy to understand
>>>>
>>>> Thanks again. Let me know if you need help in the documentation.
>>>>
>>>> Bosco
>>>>
>>>>
>>>> From: Madhan Neethiraj
>>>> Reply-To: <[email protected]>
>>>> Date: Monday, October 12, 2015 at 5:46 PM
>>>> To: "[email protected]"
>>>> Subject: [DISCUSS] Policy model enhancement to support deny-conditions
>>>> and exceptions
>>>>
>>>> All,
>>>>
>>>> Apache Ranger policy model enhancement to support deny-conditions and
>>>> exceptions (RANGER-606
>>>> <https://issues.apache.org/jira/browse/RANGER-606>) is available in
>>>> tag-policy
>>>> branch <https://github.com/apache/incubator-ranger/tree/tag-policy>.
>>>> This enhancement adds the capability to explicitly deny access to resources
>>>> based on users/groups, access-types and custom-conditions. It also supports
>>>> allow/deny to be specified for a wider group (like employees, public, etc)
>>>> but exclude specific users/groups who might be part of the wider groups.
>>>>
>>>> An overview of the implementation, along with few examples is available
>>>> in Apache wiki page here
>>>> <https://cwiki.apache.org/confluence/display/RANGER/Deny-conditions+and+exceptions+in+Ranger+policies>.
>>>> Please review.
>>>>
>>>> Thanks,
>>>> Madhan
>>>>
>>>>
>>>>
>>>
>>
>
