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 <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)

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

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.