Cross-account IAM roles are a powerful security feature in AWS that enables secure access to resources across different AWS accounts. This capability is essential for organizations managing multiple accounts, such as separate accounts for development, testing, and production environments.
An IAM r…Cross-account IAM roles are a powerful security feature in AWS that enables secure access to resources across different AWS accounts. This capability is essential for organizations managing multiple accounts, such as separate accounts for development, testing, and production environments.
An IAM role is an AWS identity with specific permissions that can be assumed by trusted entities. Unlike IAM users, roles do not have permanent credentials. Instead, when a role is assumed, AWS provides temporary security credentials.
How Cross-account Roles Work:
1. Trust Relationship: The account owning the resources (trusting account) creates an IAM role with a trust policy that specifies which external account (trusted account) can assume the role.
2. Permissions Policy: The role includes permissions defining what actions can be performed on resources in the trusting account.
3. Assuming the Role: Users or applications from the trusted account use AWS Security Token Service (STS) to assume the role and receive temporary credentials.
Key Benefits:
- Enhanced Security: Temporary credentials reduce the risk associated with long-term access keys. Credentials automatically expire after a specified duration.
- Centralized Management: Organizations can maintain separate accounts while allowing controlled access between them.
- Audit Trail: AWS CloudTrail logs all role assumption activities, providing visibility into who accessed what resources and when.
- Least Privilege: Roles can be configured with specific permissions, ensuring users only have access to necessary resources.
Common Use Cases:
- Third-party vendors accessing your AWS resources securely
- Shared services across organizational accounts
- Consolidated billing and management scenarios
- Cross-account resource sharing for collaboration
Best Practices:
- Use external IDs to prevent confused deputy attacks
- Implement MFA requirements for sensitive role assumptions
- Regularly review and audit cross-account access
- Apply the principle of least privilege when defining permissions
Cross-account IAM roles are fundamental to AWS security architecture, enabling secure collaboration while maintaining proper access controls.
Cross-account IAM Roles: Complete Guide for AWS Cloud Practitioner
Why Cross-account IAM Roles Are Important
Cross-account IAM roles are a fundamental security mechanism in AWS that enables secure access between different AWS accounts. Organizations often operate multiple AWS accounts for various reasons such as separating development from production environments, managing different business units, or implementing security boundaries. Cross-account roles provide a secure way to grant access across these account boundaries without sharing long-term credentials.
What Are Cross-account IAM Roles?
A cross-account IAM role is an IAM role in one AWS account that can be assumed by principals (users, applications, or services) from a different AWS account. This mechanism allows you to delegate access to resources in your account to trusted entities in another account.
Key Components: - Trusting Account: The account that owns the resources and creates the role - Trusted Account: The account that contains the users or services that need access - Trust Policy: Defines which principals from the trusted account can assume the role - Permissions Policy: Defines what actions the role can perform once assumed
How Cross-account IAM Roles Work
1. Role Creation: An administrator in Account A creates an IAM role with a trust policy that specifies Account B as trusted
2. Permission Assignment: The role is given permissions policies that define what resources can be accessed
3. Role Assumption: A user or service in Account B calls the AWS Security Token Service (STS) AssumeRole API
5. Resource Access: The entity uses these temporary credentials to access resources in Account A
Benefits: - No need to create IAM users in multiple accounts - No sharing of long-term credentials - Temporary credentials that automatically expire - Centralized access management - Audit trail through AWS CloudTrail
Common Use Cases
- Centralized Security Account: Security team members assume roles in other accounts for auditing - Resource Sharing: Allowing a partner organization to access specific S3 buckets - Multi-account Architecture: Developers accessing resources across development, staging, and production accounts - AWS Organizations: Managing access across organizational units
Exam Tips: Answering Questions on Cross-account IAM Roles
Key Points to Remember:
1. Trust Relationship is Essential: Cross-account access requires a trust policy that explicitly allows the external account to assume the role
2. Temporary Credentials: When a role is assumed, AWS STS provides temporary security credentials, not permanent access keys
3. No User Creation Required: You do not need to create separate IAM users in the target account; roles eliminate this need
4. AssumeRole API: Remember that the STS AssumeRole action is used to obtain temporary credentials
5. Best Practice: Cross-account roles are the recommended method for granting cross-account access rather than sharing access keys
Question Patterns to Watch For:
- Questions about securely sharing resources between accounts should point to cross-account roles - Scenarios involving partner access or third-party access typically involve cross-account roles - Questions mentioning temporary credentials and cross-account access relate to STS and role assumption - When asked about alternatives to sharing credentials between accounts, cross-account roles are the answer
Common Distractors to Avoid:
- Creating IAM users in multiple accounts (less secure, harder to manage) - Sharing access keys between accounts (security risk) - Using root account credentials (never recommended) - Resource-based policies alone (sometimes correct but roles are often more appropriate for user access)