The proposal is over ambitious in some areas, under ambitious in others. I'd suggest the following:

Assumptions:
The first objective of introducing authorization into Kimchi is to allow an admin to partition defined VMs for independent, secure use by different users.

Scenario:
Frank is the manager of a team consisting of developers and testers with a clear separation of responsibility. He already has groups created on his linux host with user id membership organized by the user's function. Frank needs to create some VMs for his teams to use. He is the sole root user on the host.
He wants the developers to be able to manage their VMs' lifecycle, but not to have permission to increase their VMs resource allocation. Developers always want as much memory as they can get away with:-)
He wants the testers to have permission to edit the resource allocation of their VMs. The software needs to be verified with different hardware configurations, and he doesn't want to have to make every edit for his testers each time they need to validate a new scenario.
Resolution:
Frank creates his VMs.
Those he has created for use by his developers, he assigns the user role to the development group for each of the VMs granting all his developers permission to see and manage the life cycle of the VMs
Those he has created for use by his testers, he assigns the admin role to the test group for each of the VMs granting all his testers permission to see and take all actions to the VMs

User Design goals
An existing system user will only see the resources and actions the user is authorized to use
An existing system sudo user will see and be able to act on all resources
Actions on a given resource can be restricted with more than binary granularity. Some authorized users may have more privilege on a resource than others. ie Some authorized users may be able to edit a VMs resource definition, while others can only manipulate its life cycle

System Design Goals
No new prerequisites are required to be installed or managed. i.e. No database prerequisite
No new user repository is required beyond what the host system is configured to use. PAM
The authorization scheme will work with read only user repositories.
Authorization information will be portable. ie. If a VM is moved from one kimchi host to another, the new host is immediately aware of the security constraints.
The system is secure. A user will not be able discover the REST API and invoke actions directly without authorization.
Kimchi managed resources can still be managed by other KVM tools, and returned to Kimchi without loss of function.
Kimchi 1.2 authorization design is extensible to cover arbitrarily fine grained constraints

Kimchi 1.2 Proposal
Users in the sudo (admin) group would continue having full access to all Kimchi functions.
Users not in the sudo (admin) group would only have access to VMs that they are authorized to use.
A VM user could have one of two roles on a given VM
        admin - user has access to all VM actions on the individual VM
        user - user has access to power on, power off, reboot, snapshot, VNC/Spice as appropriate on the individual VM

Group/role mapping will be stored in the <metadata> element of the VM Domain XML. If the VM is migrated to a new host, the metadata will go with it.

Algorithm
Login:
    If the user is a member of the sudo (admin) group
        grant all permissions and render the full Kimchi UI as today
    else
        enumerate all the groups the user is a member of, including groups of groups recursively
        for each VM determine the highest role available to the user by the various groups he is a member of
        render the kimchi frame with only a list of the authorized VMs, each with the appropriate actions
        If none, render the empty list


Kimchi 1.2+ Extensibilty
How can the 1.2 proposal be extended in future Kimchi versions as needed?
    Resource
        Other resources (network, storage) can use the same group/role authorization concept, relying on similar libvirt metadata for storage. Storage for the authorization mapping would have to be elsewhere for any resource libvirt has not defined metadata on.
    Admin granularity
        Additional roles can be introduced to allow some admins control over network while others control storage pools and volumes. Storage for these administration scoped roles would have to be defined and replicated for future cluster support.
    Role granularity
        Additional roles can be introduced beyond admin and user to allow more differentiation in what actions a specific group of users can access including custom administrator defined roles

-- 
Adam King <rak@linux.vnet.ibm.com>
IBM CSI