Cis Azure Foundations 5.23

Ensure no custom subscription administrator roles exist

Description

The principle of least privilege should be followed and only necessary privileges should be assigned instead of allowing full administrative access.

Rationale

Custom roles in Azure with administrative access can obfuscate the permissions granted and introduce complexity and blind spots to the management of privileged identities. For less mature security programs without regular identity audits, the creation of Custom roles should be avoided entirely. For more mature security programs with regular identity audits, Custom Roles should be audited for use and assignment, used minimally, and the principle of least privilege should be observed when granting permissions.

Impact

Subscriptions will need to be handled by Administrators with permissions.

Audit Procedure

Using Azure Portal

1. From Azure Home select the Portal Menu.
2. Select Subscriptions.
3. Select a subscription.
4. Select Access control (IAM).
5. Select Roles.
6. Click Type and select Custom role from the drop-down menu.
7. Select View next to a role.
8. Select JSON.
9. Check for assignableScopes set to the subscription, and actions set to *.
10. Repeat steps 7-9 for each custom role.

Using Azure CLI

az role definition list --custom-role-only True

Check for entries with assignableScope of the subscription, and an action of *.

Using PowerShell

Connect-AzAccount
Get-AzRoleDefinition | Where-Object {($_.IsCustom -eq $true) -and ($_.Actions.contains('*'))}

Check the output for AssignableScopes value set to the subscription.

Using Azure Policy

• Policy ID: a451c1ef-c6ca-483d-87ed-f49761e3ffb5 - Name: 'Audit usage of custom RBAC roles'

Expected Result

No custom roles should exist with assignableScopes set to the subscription and actions set to *.

Remediation

Using Azure Portal

1. From Azure Home select the Portal Menu.
2. Select Subscriptions.
3. Select a subscription.
4. Select Access control (IAM).
5. Select Roles.
6. Click Type and select Custom role from the drop-down menu.
7. Check the box next to each role which grants subscription administrator privileges.
8. Select Delete.
9. Select Yes.

Using Azure CLI

az role definition list --custom-role-only True

Check for entries with assignableScope of the subscription, and an action of *.

To remove a violating role:

az role definition delete --name <role name>

Note that any role assignments must be removed before a custom role can be deleted. Ensure impact is assessed before deleting a custom role granting subscription administrator privileges.

Default Value

By default, no custom owner roles are created.

References

1. https://learn.microsoft.com/en-us/azure/cost-management-billing/manage/add-change-subscription-administrator
2. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-privileged-access#pa-1-separate-and-limit-highly-privilegedadministrative-users
3. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-privileged-access#pa-3-manage-lifecycle-of-identities-and-entitlements
4. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-governance-strategy#gs-2-define-and-implement-enterprise-segmentationseparation-of-duties-strategy
5. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-governance-strategy#gs-6-define-and-implement-identity-and-privileged-access-strategy
6. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-privileged-access#pa-7-follow-just-enough-administration-least-privilege-principle

CIS Controls

Profile

Level 1 | Automated