iam-identity-management

OCI IAM and Identity Management - Expert Knowledge

NEVER Do This

NEVER use overly broad policies in production

# WRONG - grants admin to everyone, instant security audit failure
Allow any-user to manage all-resources in tenancy

# RIGHT - explicit group, specific resource, specific compartment
Allow group AppDevelopers to manage instance-family in compartment AppDev
  where target.instance.name =~ 'dev-*'

NEVER place policy in a child compartment when the target resource is in a parent

# WRONG - policy in A/B/C cannot grant access to resources in A
Policy location: Compartment A/B/C
"Allow group X to read buckets in compartment A"  # Fails silently

RIGHT - policy must be AT OR ABOVE the target compartment

Policy location: Compartment A (or root tenancy) "Allow group X to read buckets in compartment A"

This is the single most common policy misconfiguration in OCI — no error is thrown, access just fails.

**NEVER use `any-user` in production policies**
- Grants access to ALL future users, including compromised accounts
- Always fails SOC2/HIPAA/CIS audits
- Use explicit group membership: `Allow group DataReaders to read buckets in compartment SharedData`

**NEVER grant access to instances using user principal syntax**

WRONG - instances are NOT users

Allow user to read buckets in compartment X

RIGHT - use dynamic groups for instances

Allow dynamic-group app-instances to read buckets in compartment X

**NEVER hardcode resource OCIDs in dynamic group rules**

WRONG - breaks when instance is replaced

ALL {instance.id = 'ocid1.instance.oc1.phx.xxxxx'}

RIGHT - use compartment or tag matching (survives instance replacement)

ALL {instance.compartment.id = ''} ANY {instance.freeform-tags.environment = 'production'}

## IAM Permission Troubleshooting

### "404 NotAuthorizedOrNotFound"

This error is intentionally ambiguous — OCI returns 404 whether the resource doesn't exist OR the caller lacks `inspect` permission. This prevents enumeration attacks.

404 NotAuthorizedOrNotFound? │ ├─ Does the resource definitely exist? │ ├─ YES → Permission issue │ │ └─ Does caller have at least 'inspect' on that resource type? │ │ └─ Is policy at or above the target compartment? │ └─ NO → Verify OCID, compartment, region │ ├─ Using dynamic group / instance principal? │ └─ oci compute instance get --instance-id (check compartment + tags) │ └─ Does instance's compartment/tags match the dynamic group rule? │ └─ Cross-compartment access? └─ Policy must be in the compartment containing BOTH source and target OR in root (tenancy)

### "403 NotAuthorized"

Caller is identified but explicitly lacks permission.

**Common causes:**
1. **Wrong verb**: Policy grants `read` but action requires `use` or `manage`
2. **Wrong resource-type**: Granted `instance-family` but accessing `volume-family`
3. **Condition doesn't match**: `where target.instance.name = 'prod-*'` but instance is `dev-web-1`
4. **Propagation lag**: Policies take 10–60 seconds to take effect after creation/update

**Verb hierarchy** (each includes those below it):

inspect < read < use < manage

## Policy Syntax Gotchas

### Resource Type Families (Often Confused)

| Family | Includes | Common Mistake |
|--------|----------|----------------|
| `instance-family` | instances, console-connections, vnics, vnic-attachments | Does NOT include volumes |
| `volume-family` | volumes, volume-backups, volume-attachments | Separate from instance-family |
| `object-family` | buckets, objects | Objects are a separate resource type from buckets |
| `database-family` | db-systems, databases, autonomous-databases | Very broad — scope carefully |

### Conditions (WHERE clause)

Tag-based

where target.resource.tag.environment = 'production' where target.resource.freeform-tags.CostCenter = 'Engineering'

Resource name (regex)

where target.instance.name =~ 'web-*'

Request properties

where request.operation = 'LaunchInstance'

Combined conditions

where all {target.resource.tag.env = 'prod', target.compartment.name = 'AppProd'} where any {target.instance.shape = 'VM.Standard.E4.Flex', target.instance.shape = 'VM.Standard.A1.Flex'}

### Location Syntax

in compartment # Specific compartment only in tenancy # Root — applies everywhere in resource # Rare; used for delegation

Note: there is no built-in syntax for "compartment + all descendants" — to cover a subtree, put the policy in the parent compartment.

## Dynamic Group Patterns

**By compartment** (most common — covers all current and future instances):

ALL {instance.compartment.id = ''}

**By tag** (flexible — survives instance replacement):

ANY {instance.freeform-tags.app = 'webserver'}

**Restrictive AND rule** (production workloads):

ALL {instance.compartment.id = '', instance.freeform-tags.environment = 'production'}

### Testing Dynamic Group Membership

```bash
# 1. Get instance details (compartment + tags)
oci compute instance get --instance-id <instance-ocid>

# 2. Check dynamic group rule
oci iam dynamic-group get --dynamic-group-id <group-ocid>

# 3. Verify rule matches — if rule is "instance.compartment.id = X",
#    confirm the instance's compartment_id field equals X

# 4. Test from the instance (SSH in and run):
oci os ns get  # Works only if instance principal is correctly configured

Authentication Methods

Method	Use Case	Key Constraint
API Key	Local dev, CI/CD outside OCI	Manual rotation required
Instance Principal	Apps on OCI compute	Only works on OCI compute
Resource Principal	OCI Functions, Data Flow	Limited to specific services
Session Token	Console federation via IDCS	Short-lived (~1 hour)

IDCS Federation Gotchas

• OCI group names must exactly match IDCS group names (case-sensitive)
• User can log in to console but can't see resources → Missing OCI IAM policy for the federated group
• "Invalid credentials" → IDCS federation not configured in OCI tenancy settings
• Group membership doesn't sync → OCI group name doesn't match IDCS group name

Compartment Hierarchy Design

# WRONG: Flat structure — no IAM boundary between dev/prod
Tenancy
├─ Application1  (mix of dev/test/prod resources)
└─ SharedServices

# RIGHT: Environment-based hierarchy — clear blast radius, cost reporting
Tenancy
├─ Production
│  ├─ App1
│  └─ App2
├─ Development
│  ├─ App1
│  └─ App2
└─ SharedServices
   ├─ Networking
   └─ Security

Progressive Loading Reference

Load references/oci-iam-policies-reference.md when:

• Writing complex policies with multiple conditions
• Need service-specific verbs and permission lists
• Troubleshooting policy evaluation order
• Implementing least-privilege access for a specific service

Do NOT load for quick syntax examples, troubleshooting 403/404, or dynamic group rules — this file covers those.