Oracle Cloud Infrastructure’s Identity and Access Management (IAM) service now supports explicit deny policies, providing administrators with the ability to explicitly block unwanted actions and enforce more precise access controls across the tenancy. This enhancement strengthens guardrails for security-sensitive environments by allowing fine-grained restrictions that override existing permissions.
What Are IAM Deny Policies?
Deny policies in OCI IAM are a strategic extension to the traditional allow-only model. Historically, IAM in OCI operated under an implicit deny model: everything is denied by default unless explicitly allowed. However, deny policies introduce a new capability where administrators can explicitly specify actions or access that must be prevented, even if they are otherwise allowed by existing policies.
By design:
- Deny policies override allow policies to enforce explicit restriction.
- They help enforce organizational security standards, compliance requirements, and guardrails.
Key Characteristics
Opt-In Feature
IAM deny policies are disabled by default. A tenancy administrator must explicitly enable the functionality through the OCI Console under the Policies page. Once enabled, the feature is irreversible through the UI, underscoring its security impact.
Default Administrative Exemptions
To mitigate the risk of accidental lockouts due to overly broad deny statements, the default administrators group in the default domain is exempt from deny policies. This ensures that administrative access remains intact even if an aggressive deny policy is authored.
Policy Precedence
Deny policies take precedence over allow policies during evaluation. If a deny rule applies, it will block the specified action irrespective of any existing allow permissions that might otherwise permit it.
Syntax and Composition
Deny policy syntax closely mirrors the structure of traditional allow policies. The only difference is that statements begin with deny, deny admit, or deny endorse instead of allow. This aligns with OCI’s consistent policy statement pattern of:
<action> <subject> to <verb> <resource> in <location> [where <condition>]
Example Deny Statement:
deny group DevTeam to manage bucket-family in compartment Prod where request.operation = ‘DeleteBucket’
This policy prevents the DevTeam group from deleting buckets in the Prod compartment, even if they have other broader permissions that would otherwise allow it.
Practical Use Cases
- Guardrails for Production Resources
In a multi-environment tenancy (e.g., Dev, QA, Prod), deny policies are useful to protect critical resources:
- Prevent accidental deletions or modifications of production storage, compute, or network components.
- Ensure only specified teams can perform sensitive operations.
Example:
deny any-user to manage network-family in compartment Prod where request.operation = ‘DeleteVcn’
This blocks all users from deleting virtual cloud networks (VCNs) in the production compartment.
- Separation of Duties
Organizations can enforce stricter role demarcation by explicitly blocking actions for one group while allowing them for others:
- Block low-privilege groups from modifying governance resources.
- Restrict specific administrative actions to security or compliance team members only.
Best Practices
To ensure deny policies enhance security without unintended consequences, consider the following best practices:
- Enable with caution: Since the feature is permanent once activated, ensure stakeholders agree on the governance implications.
- Limit scope and conditions: Use targeted conditions (e.g., compartments, operations) to avoid overly broad restrictions.
- Preserve administrative access: Do not remove exemptions for default administrative groups unless absolutely required.
- Review known issues: Be aware of limitations (e.g., tag-based denies may take time to propagate, and some dynamic group conditions may not be supported).
Enabling IAM Deny Policies
To enable deny policies in OCI:
- Navigate to the Policies list in the OCI Console.
- From the Actions menu, select Policy settings.
- Select Enable IAM Deny Policy.
- Confirm to activate the feature; the system will create a default deny policy that restricts who can author further deny policies.
Conclusion
OCI IAM Deny Policies represent a significant step forward in access control governance, enabling organisations to define precise, explicit restrictions that complement existing allow rules. By adopting deny policies thoughtfully, administrators can reinforce security boundaries, protect critical environments, and tailor access controls in alignment with compliance and operational requirements.
For comprehensive guidance, always consult the official OCI documentation and align deny policy design with broader security governance frameworks.
