aws-iam

name	aws-iam
description	AWS IAM deep-dive skill - principal types, policy evaluation, STS assume role, SCP guardrails, KMS key policies/grants, and AccessDenied debugging. Use when designing AWS authz/authn, cross-account access, or troubleshooting IAM/KMS/SCP AccessDenied errors.

AWS IAM

When to use

Use this skill when you are working on:

• IAM principals (users, roles, assumed-role sessions, service principals)
• Trust policies (sts:AssumeRole*) and cross-account access
• Identity-based vs resource-based policies
• Permission boundaries, session policies, and Organizations SCPs
• KMS key policies, grants, and kms:Decrypt / kms:GenerateDataKey failures
• Debugging AccessDenied in AWS (including cross-account and KMS)

What to do (workflow)

1. Identify the runtime principal (often an STS assumed-role ARN)
2. Identify the action + resource ARN(s) from the error or design requirement
3. Determine which policy layers are in play:
   • identity-based policy
   • resource-based policy
   • permission boundary
   • session policy
   • SCP (Organizations)
4. Look for explicit deny first (it wins)
5. For cross-account flows:
   • validate the trust policy (who can assume)
   • validate the permission policy (what the role can do)
   • validate any resource policy (who can access the target resource)
6. For KMS:
   • validate key policy + IAM policy + any grant constraints

References

• references/iam-authorization-model.md
• references/cross-account-and-externalid.md
• references/cross-service-confused-deputy.md
• references/kms-key-policy-and-grants.md
• references/eks-pod-identity-abac-and-lattice.md