Background

Currently CloudStack provides very limited IAM services and there are several drawbacks within those services:

• Offers few roles out of the box (user and admin) with prebaked access control for these roles. There is no way to create additional roles with customized permissions.
• Some resources have access control baked into them. E.g., shared networks, projects etc.
• We have to create special dedicate API to grant permissions.

Goal for this feature would be to address these limitations and offer true IAM services in a phased manner

Architecture and Design description

IAM Taxonomy

Group

Group contains a number of CloudStack accounts. Customers should be able to Create, Edit, List and Delete Groups. Editing includes adding or removing accounts to or from a group. For backwards compatibility, out of box, CloudStack will provide 3 default groups:

• Root Admin Group
• Domain Admin Group
• End User Group

Account

Account is just our current CloudStack Account, all the permission controls are done at Account level. We can assign an Account to more than one Group.

User

CloudStack user just contains login credentials, and this is not the level that we are performing permission control.

Policy

Policy is a set of permission. Customer should be able to attach several policies to a Group to define the permission for that group. By default, we have the following 3 types of policy templates:

1. Root Admin Policy: have permissions to all resources in the CloudStack for allowed APIs.
2. Domain Admin Policy: have permissions to all resources under the belonging domain for allowed APIs.
3. Resource Owner Policy: have permissions to all owned resources for allowed APIs.

Other than that, customer should be able to define customized policies by grant or deny permission to customize permissions for the group. So far, for cross-account permission grant, we are currently supporting the following 3 types of granting/denying:

• Grant by Domain and Resource Type: grant permissions to all resources of the given resource type under the given domain.
• Grant by Account and Resource Type: grant permissions to all resources of the given resource type under the given account.
• Grant by individual resource: grant permission to an individual resource.

Permission

A policy consists of set of Permissions. A Permission is a way of defining access control.
Using Permission, customer defines what actions are allowed or denied, on what resources, under which account or domain.

A single permission definition consists of:

• Action (API Name)
• Allow / Deny
• Scope (Account | Domain | Resource)
• Scope Id (Id of the above defined scope)
• Resource Type

Response View (Column Filter)

Currently CloudStack supports two different views: Full View for root admin user, Restricted View for domain admin and end user. With IAM added, we still need to support this for newly added account groups. Analogy to row filter controlled by Permission, this is like column filter. For this release, we are not supporting dynamic column filter at API level, instead, out-of-box, we will provide two static response views: Full View and Restricted View. When user is creating a group, they can specify what kind of view that this group account should see.

IAM Schema

IAM API

New API's

• createAclGroup
  1. String name - name of the ACL group. Required
  2. String description - short decsription
  3. String domainId - UUID of the domain of the account owning the acl group

• deleteAclGroup
  1. String id - UUID of the ACL group. Required

• listAclGroups
  1. String name - name of the ACL group.
  2. String id - UUID of the ACL group.

• addAccountToAclGroup
  1. String id - UUID of the ACL group. Required
  2. List<String> accounts - comma separated list of account id that are going to be assigned to the acl group

• removeAccountFromAclGroup
  1. String id - UUID of the ACL group. Required
  2. List<String> accounts - comma separated list of account id that are going to be removed from the acl group

• createAclPolicy
  1. String name - name of the ACL Policy. Required
  2. String description - short decsription
  3. String domainId - UUID of the domain of the account owning the acl policy
  4. String sourcePolicyId - UUID of the policy which should be used as a template to generate the new policy

• deleteAclPolicy
  1. String id - UUID of the ACL Policy. Required

• listAclPolicies
  1. String name - name of the ACL policy.
  2. String id - UUID of the ACL policy.

• attachAclPolicyToAclGroup
  1. String id - UUID of the ACL group. Required
  2. List<String> policies - comma separated list of policy ids that are going to be assigned to the acl group

• removeAclPolicyFromAclGroup
  1. String id - UUID of the ACL group. Required
  2. List<String> policies- comma separated list of policy ids that are going to be revoked from the acl group

• createAclPermission
  1. String action - name of the API allowed/denied. Required
  2. String permission - "Allow"/ "Deny"
  3. String scope- ("Account" / "Domain" / "Resource")
  4. String scope id - UUID of the Scope
  5. String resourceType

• addAclPermissionToAclPolicy
  1. String id - UUID of the ACL policy. Required
  2. List<String> permissionIds - comma separated list of permission ids that are going to be added to the acl policy

• removeAclPermissionFromAclPolicy
  1. String id - UUID of the ACL policy. Required
  2. List<String> permission Ids - comma separated list of permission ids that are going to be removed from the acl policy

IAM Interface

IAM Interface to check Entity Access

CloudStack currently has a domain-tree based implementation of access checks, namely com.cloud.acl.DomainChecker. This implementation is based on an adapter interface of Cloudstack - org.apache.cloudstack.acl.SecurityChecker that defines the basic ACL interface to check ownership and access control to objects within the account/ domain.

The IAM plugin will provide another implementation 'PolicyBasedAccessChecker' of the SecurityChecker interface. We will also have to add to this interface some more methods or change some signatures to facilitate group, policy and api name (action) based access control.

/**
* SecurityChecker checks the ownership and access control to objects within
*/
public interface SecurityChecker extends Adapter {

...

/**
* Checks if the account can access the object.
*
* @param caller
* account to check against.
* @param entity
* object that the account is trying to access.
* @param accessType
*
* @param action
*
* @return true if access allowed. false if this adapter cannot provide permission.
* @throws PermissionDeniedException
* if this adapter is suppose to authenticate ownership and the check failed.
*/
boolean checkAccess(Account caller, ControlledEntity entity, AccessType accessType, String action) throws PermissionDeniedException;

....
}

The implementation will check if a given user is permitted to invoke the given 'action' on the given resource by looking at the account's groups and the associated policies of those groups.

For given user, resource and given api name,

• Find all groups the user belongs too.
• Find all 'effective' policies the groups are associated to. Effective includes all policy associations in the DB and the dynamic 'Resource Owner' policy if the resource is owned by the user
• If any policy 'Allows' the API, grant permission to make this call
• Else, if any policy 'Denies' the API, deny permission to make this call
• Else, if no Allow or Deny entry is found for any policy for this API, deny the permission

IAM Interface to check API Access

IAM Plugin 'PolicyBasedAccessChecker' will implement the APIChecker interface.

// APIChecker checks the ownership and access control to API requests
public interface APIChecker extends Adapter {
    // Interface for checking access for a role using apiname
    // If true, apiChecker has checked the operation
    // If false, apiChecker is unable to handle the operation or not implemented
    // On exception, checkAccess failed don't allow
    boolean checkAccess(User user, String apiCommandName) throws PermissionDeniedException;
}

The API permissions are also stored in the same db schema as the entity permissions. Since the above entity access already checks if the user is allowed to invoke the given API for the given resource, we need not have one more check just to see if the user can invoke the API.

So PolicyBasedAccessChecker :: checkAccess(User user, String apiCommandName), can return true always and rely on the entity based access check.

IAM Interface to facilitate Query APIs

Besides SecurityChecker and APIChecker interface, IAM plugin will also implement another QueryChecker interface to allow CloudStack to do proper row filter in ListAPI based on caller's policy.

/**
* QueryChecker returns granted domain, or account or resources for caller.
*/
public interface QueryChecker extends Adapter {

...

/**
* List granted domains for the caller, given a specific entity type.
*
* @param caller account to check against.
* @param entityType entity type
* @return list of domain Ids granted to the caller account.
*/
List<Long> getAuthorizedDomains(Account caller, String entityType);

/**
* List denied domains for the caller, given a specific entity type.
*
* @param caller account to check against.
* @param entityType entity type
* @return list of domain Ids granted to the caller account.
*/
List<Long> getDeniedDomains(Account caller, String entityType);

/**
* List granted accounts for the caller, given a specific entity type.
*
* @param caller account to check against.
* @param entityType entity type
* @return list of domain Ids granted to the caller account.
*/
List<Long> getAuthorizedAccounts(Account caller, String entityType);

/**
* List denied accounts for the caller, given a specific entity type.
*
* @param caller account to check against.
* @param entityType entity type
* @return list of domain Ids granted to the caller account.
*/
List<Long> getDeniedAccounts(Account caller, String entityType);

/**
* List granted resources for the caller, given a specific entity type.
*
* @param caller account to check against.
* @param entityType entity type
* @return list of domain Ids granted to the caller account.
*/
List<Long> getAuthorizedResources(Account caller, String entityType);

/**
* List denied resources for the caller, given a specific entity type.
*
* @param caller account to check against.
* @param entityType entity type
* @return list of domain Ids granted to the caller account.
*/
List<Long> getDeniedResources(Account caller, String entityType);
}

By invoking these QueryChecker APIs, CloudStack API engine can pre-construct proper SQL where clause to achieve proper row filter for accessibility control.

Response View

Currently CloudStack provides different response views for Root admin and non-root user, some response fields are only visible to root admin. Basically we have provided two static response views (Full view and Restricted view), domain admin will also a User view. With new IAM service introduced, we should also allow customers to be able to specify what view should be applied to the new Acl group when they are creating a new customized Acl group, for example, customer care group. To achieve that, we will implement as follows:

1. We will have a column in AclGroup db table to record what view to be used for this group. From Acl group creation UI, user can pick which view to be associated with this group. Note that in this release, we are not going to support full-fledged column filter (that is, allowing users to pick arbitrary columns to be see for each API). We are only supporting static view association at the Acl group level.
2. We will separate all current both admin and user allowed API commands to two classes: API for admin and API for user. For example, previous ListVMsCmd will be splitted into two classes: ListVMsCmdByAdmin and ListVMsCmd.

   @APICommand(name = "listVirtualMachines", description = "List the virtual machines owned by the account.", responseObject = UserVmResponse.class, responseView = ResponseView.Restricted)
   public class ListVMsCmd extends BaseListTaggedResourcesCmd {
   ......
   }
   
   @APICommand(name = "listVirtualMachines", description = "List the virtual machines owned by the account.", responseObject = UserVmResponse.class, responseView = ResponseView.Full)
   public class ListVMsCmdByAdmin extends ListVMsCmd {
       /////////////////////////////////////////////////////
       //////////////// API parameters /////////////////////
       /////////////////////////////////////////////////////
   
       @Parameter(name=ApiConstants.HOST_ID, type=CommandType.UUID, entityType=HostResponse.class,
               description="the host ID")
       private Long hostId;
   
       @Parameter(name=ApiConstants.POD_ID, type=CommandType.UUID, entityType=PodResponse.class,
               description="the pod ID")
       private Long podId;
   
       @Parameter(name=ApiConstants.STORAGE_ID, type=CommandType.UUID, entityType=StoragePoolResponse.class,
               description="the storage ID where vm's volumes belong to")
       private Long storageId;
   }
   

   Note that ListVMsCmdByAdmin and ListVMsCmd are sharing the same API name "listVirtualMachines". From client perspective, this is transparent to them, CloudStack API client will still just invoke previous listVirtualMachine API, and CloudStack API server will internally consult with IAM plugin to determine the group associated with the invoking user and then determine which internal Cmd class to be invoked. There is a new attribute "responseView" introduced for @APICommand annoation, which can be used to instruct CloudStack to generate different response view. By separating the command class into admin cmd class and user cmd class, we can also restrict valid input parameters for different account. For example, in this case, when Admin invokes listVirtualMachine api, he/she can pass hostId, podId and storageId, which parameters are not applicable for end user.

Default Policy

Default Policy Generation Flow

For backward compatibility, out-of-box, we provided 3 default policies: Root admin policy, domain admin policy, and end user policy. The process to populate permissions for these default policies are as follows:

1. Parse all API command classes to check if they are annotated with "authorized" attribute. If so, populate a permission entry for that API for the default policy mapped to that authorized role.
2. Parse commands.property, create or override permission entries for each API for default policy mapped to API authorized roles.

When user creates a customized policy, he can specify a source policy from list of default policies. Then we will create new mapping between these default policy permission entries and the new policy in acl_policy_permission_map table.

Sample DB Entries for Default Policy

account

acl_group

acl_group_account_map

acl_policy

acl_group_policy_map

Sample DB entries for the policy permissions for 'StartVM' operation:

acl_permission

acl_policy_permission_map

Access Check Flow

Lets consider the StartVM API is being called by a user and run through the access control usecase for each default policy.

The StartVMCmd will contain an annotation on the field that needs to be checked for access:

@APICommand(name = "startVirtualMachine", responseObject = UserVmResponse.class, description = "Starts a virtual machine.")
public class StartVMCmd extends BaseAsyncCmd {
    public static final Logger s_logger = Logger.getLogger(StartVMCmd.class.getName());

    private static final String s_name = "startvirtualmachineresponse";

    // ///////////////////////////////////////////////////
    // ////////////// API parameters /////////////////////
    // ///////////////////////////////////////////////////

    @ACL(action="startVirtualMachine")
    @Parameter(name = ApiConstants.ID, type = CommandType.UUID, entityType=UserVmResponse.class,
            required = true, description = "The ID of the virtual machine")
    private Long id;

Regular user 'domainUserA' calls this command for his own VM:

API access check

The API layer will call the APICheckers to see if the user is allowed to invoke this API. The PolicyBasedAccessChecker :: checkAccess(user, apiName) will just return true and rely on next step

Entity Access Check

The @ACL annotation invokes the SecurityChecker implementation. The PolicyBasedAccessChecker:: checkAccess(Account caller, ControlledEntity entity, AccessType accessType, String action) is invoked for the given user account and VM Id for action 'startVirtualMachine'

• Find all groups the user belongs to: groupIDs = 1
• Find all 'Effective' policies the groups are associated to: policies = 1, 6
• If any policy 'Allows' the startVirtualMachine API for this Vm Id, grant permission to make this call: Policy Id 6 and Permission Id 3 allow the API to be invoked for this user.
• In this case, since this is a regular user and the user is the owner of the VM, then he is granted access using policy Id 6.

A Domain Admin 'domainAdmin' calls this command for a VM in his domain:

Entity Access Check

• Find all groups the user belongs to: groupIDs = 3
• Find all 'Effective' policies the groups are associated to: policies = 3
• Policy Id 3 and Permission Id 2 allow 'startVirtualMachine' access for VMs in the 'Domain' scope - VMs in the domainId of the user.
• In this case, since the VM is in the domain of the user, he is granted access using policy Id 3.

A Root Admin 'admin' calls this command for any VM:

Entity Access Check

• Find all groups the user belongs to: groupIDs = 2
• Find all 'Effective' policies the groups are associated to: policies = 2
• Policy Id 3 and Permission Id 1 allow 'startVirtualMachine' access for ALL VMs .

@ACL annotation changes

• As illustrated in the above access flow, the access checks get invoked when the resource Ids in the API Cmd are annotated.
• Thus we will have to edit all existing API Cmds and add the relevant @ACL annotation on the primary resource Ids the command operates on.
• For any other resources that the command works with, the current access checks placed in the service layer will invoke the SecurityChecker.
• These current access checks pass the AccessType whereever needed or mostly pass null. Our SecurityChecker will interpret null as a 'Read' access. In the 'acl_permission' schema, all List* APIs will be marked as 'Read' AccessType entries to facilitate this access check.

Custom Group and Policy

Consider following example:

A Domain admin wants to create a 'Service Desk' group for his domain and allow 'ready only' access to the group for all VMs and Volumes within the Domain.

Steps:

• createAclGroup('Service Desk', 'Service Desk group', $domainId of the admin)
• createAclPolicy('Read Only Access', 'read only access to domain resources', $domainId of the admin)
• createAclPermission('ListVirtualMachine', 'Allow', 'Domain', $domainId, 'VirtualMachine')
• createAclPermission('ListVolumes', 'Allow', 'Domain', $domainId, 'Volume')
• addAclPermissionToAclPolicy( UUID of the 'Read Only Access' policy, List<String> permissionIds of above permissions)
• attachAclPolicyToAclGroup (groupId, policyId)
• addAccountToAclGroup(groupId, List<String> accountIds)