On 01/15/2014 05:03 AM, Shu Ming wrote:

Background

In Kimchi, now we have a basic authentication model based on PAM.  In this model, all the authenticated user get all of the privileges to access the resources in Kimchi. However, it is too simple to cause some security holes and classifying the user with different roles is a way to address the holes. Roles with very fine grained privileges need huge effort and time, so here we are trying to split the effort with several steps.  And we will discuss the first step of the effort in the below which can be achieved in a certain time bound and reserve the forward compatibility for future extensions.

First step of the effort

I think managing kimchi users roles will be the next step of authorization.

The idea for now (Kimchi 1.2) is differ between root and non-root users. What does that mean?
Users in "sudo" linux group will have full access to kimchi. And user not in this group will have limited access to kimchi.
Users with "sudo" privilege will act as admin.

In this step, the goal is to authorize the user's action on a resource by roles. The user action here is applied by the REST API exposed by Kimchi.  Every action on Kimchi resources should be checked based on the user's role.  In this step, we will not try to have roles in a very fine granularity. Naturally, three permanent roles will be created by default, the system administrator role, the infrastructure role and the user role.

   * The system administrator get the privileges to manage the roles for the other users including assigning a role to a user, removing the role from a user &etc.  A default user "admink" will be created by default with a system administrator role assigned to it. And the role of the user "admink" can not be modified.

   * The infrastructure role get the privileges to  manage the physical resources and virtual resources including network's creation and deletion, create or delete storage storage pools or storage volumes' creation and deletion, adding a user to the user list of storage storage pool &etc.

   * The user role get the privileges to apply action on VMs including VMs' starting and stopping, viewing the VM console by VNC &etc.

   * Some of the change can be enhanced on the existing REST API like "DELETE /storagepools/poo1/vo1".  But we need create new REST APIs for actions like adding a role for a user like " PUT /users/user1 {role: "user role"}"

   * Database is needed to store the user information including roles and resource user list

From my view, the roles will be user groups in linux system.
So add an user to a role is add him to a group and we don't need to keep the info internally.
Internally we will only have the map: user group => allowed URIs

Beside the privileges inherited from the user's role, Kimchi will check if a user get the permission to access a resource based on a tuple.  The tuple is composed from both the privileges of the user and the user list of the resource. An example is, if a user try ti delete a storage volume from the stroage pool,  Kimchi will check if it is assigned a infrastructure role and if it is in the user list of the storage pool.

Next step of the effort

*  The roles are defined in a very fine granularity containing the privileges precisely matching what the system administrator expects. 

*  Existing roles can by customized by the system administrator from a set of previleges.   The set of privileges should be pre-defined and hierarchy.

* The system administrator can create new roles with customized privileges

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