AWS & SRE Field Manual (Part 1): Zero-Trust Identity & Access Management (IAM)
📌 TL;DR & Problem Statement Definition: The centralized security control plane that manages authentication and authorization across all AWS cloud resources. It serves as the native AWS equivalent of Kubernetes RBAC. Problem Solved: Secures access to infrastructure resources using centralized, auditable, fine-grained, and temporary security credentials instead of distributed, static passwords and…
In the AWS & SRE Field Manual (Part 1), the focus is on Zero-Trust Identity & Access Management (IAM). This centralized security control plane manages authentication and authorization across all AWS cloud resources. It replaces the need for distributed, static passwords and access keys with temporary, auditable, fine-grained credentials.
There are four core components of IAM: users, groups, roles, and policies. Users represent individuals interacting with AWS, with access provided via console passwords, MFA, or static access key pairs. Root accounts, the initial all-powerful identities, must be protected with hardware or virtual MFA and reserved for emergency break-glass procedures.
IAM groups are logical collections of users sharing identical permission requirements. IAM roles and AWS STS (Security Token Service) provide dynamic, temporary credentials, similar to Kubernetes ServiceAccounts and EKS IRSA / Pod Identities. IAM policies are JSON documents defining who can execute specific actions against target resources under certain conditions.
The core rule of IAM is the implicit default deny, where all API requests are denied unless explicitly granted by an Allow statement. IAM policies follow a specific order of precedence for evaluation: Explicit Deny, Service Control Policies (SCPs), Resource Policies, Identity Policies, and Permissions Boundaries. This evaluation chain ensures that if any point yields an explicit deny or no policy grants an explicit allow, the request is dropped.
Permissions Boundaries define the maximum permission ceiling for an IAM entity, preventing privilege escalation even when developers create new roles with AdministratorAccess. Attribute-Based Access Control (ABAC) and Session Tags allow dynamic access based on matching metadata tags, rather than maintaining complex, static JSON policies. Cross-account access and external IDs are crucial for delegating role access to third-party SaaS vendors, preventing the confused deputy attack vector.
When implementing IAM, keep in mind the eventual consistency of IAM APIs, which may take several seconds to propagate across all AWS edge endpoints. Automation scripts and CI/CD pipelines should incorporate exponential backoff or brief delay retries in such cases.
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