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 <instance-ocid> 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 = '<compartment-ocid>'}
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 <ocid>  (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 <name-or-ocid>          # Specific compartment only
in tenancy                             # Root — applies everywhere
in resource <resource-ocid>            # 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 = '<compartment-ocid>'}

By tag (flexible — survives instance replacement):

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

Restrictive AND rule (production workloads):

ALL {instance.compartment.id = '<comp-ocid>', instance.freeform-tags.environment = 'production'}

Testing Dynamic Group Membership

# 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.