Exercise 6: Cloud Identity Federation Vulnerability

Objective:

Understand how misconfigured identity federation settings can be exploited by attackers to impersonate legitimate users. Learn the risks of weak identity federation implementations and apply best practices to secure federated identity systems.

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Scenario:

You are evaluating an organization’s federated identity setup. The organization uses AWS Cognito with a third-party Identity Provider (IdP), such as Active Directory Federation Services (ADFS). You identify weak configurations in the federation setup, such as improper token validation or excessive trust levels. Your task is to simulate an attack, demonstrate the impact, and provide mitigation recommendations.

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Lab Setup:

Prerequisites:

1. AWS account (free-tier works for this lab).
2. Basic knowledge of AWS Cognito, OAuth 2.0, and federated identity.
3. Installed tools:
   • Postman (Download Postman)
   • OpenID/OAuth tools for token generation and validation.

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Steps to Set Up the Lab:

1. Configure AWS Cognito as an Identity Provider (IdP):
   • In the AWS Management Console, navigate to Cognito > Manage User Pools > Create a user pool:
     • Name: pentesterworld-federation.
     • Enable self-registration and choose attributes like email, name, etc.
   • Enable Federation:
     • Under Identity providers, add an external IdP (e.g., OpenID Connect or SAML).
     • Configure the external IdP, such as ADFS or any OpenID Connect provider (e.g., Auth0).
   • Set up an App Client:
     • Go to App clients and create a client for the federated application.
     • Enable OAuth 2.0 flows (e.g., Authorization Code Grant).
2. Simulate a Weak Configuration:
   • Configure the IdP with relaxed security settings, such as:
     • Overly broad scopes: Allow excessive access to user attributes or resources.
     • Weak token validation: Disable signature verification for incoming tokens.
   • Add a test user in the external IdP and federate it with AWS Cognito.
3. Deploy a Test Application:
   • Use a simple front-end web application (or Postman) to initiate the OAuth 2.0 flow and retrieve access tokens.

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Exercise: Exploiting Weak Federation Settings

Objective:

Simulate an attacker exploiting weak configurations to impersonate a legitimate user or gain unauthorized access.

1. Exploit Improper Token Validation:
   • Obtain an access token from the external IdP (e.g., using Postman to simulate an OAuth 2.0 flow).
   • Modify the token payload to impersonate another user by altering the sub or email claim.
   • Send the modified token to an AWS resource (e.g., API Gateway or S3) and observe if access is granted.
2. Exploit Excessive Trust Levels:
   • Enumerate roles or permissions granted by AWS Cognito to the federated identity.
   • Use the access token to assume roles with excessive permissions (e.g., administrator roles).
   • Demonstrate unauthorized access to resources.
3. Simulate Token Replay:
   • Use the same access token in multiple requests without expiration or invalidation.
   • Observe if session hijacking is possible.

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Tools Required:

1. AWS Cognito: For identity federation setup.
2. Postman: To simulate OAuth 2.0 flows and send API requests.
3. JWT.io: To decode and modify tokens for testing.

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Deliverables:

1. Exploit Report:
   • Evidence of exploiting weak token validation or excessive trust levels.
   • Screenshots of unauthorized access to resources or impersonation attacks.
2. Recommendations for Securing Identity Federation:
   • Detailed strategies to implement MFA and stronger federation security.

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Solution:

1. Identified Vulnerabilities:
   • Improper Token Validation: Missing or disabled token signature verification allowed attackers to modify tokens.
   • Excessive Trust: Overly permissive roles allowed federated identities to access sensitive resources.
   • Token Replay: Access tokens were reused without invalidation or expiration checks.
2. Consequences:
   • Unauthorized Access: Attackers can impersonate legitimate users or gain elevated privileges.
   • Data Breach: Sensitive resources and data are exposed.
   • Regulatory Violations: Non-compliance with data protection regulations like GDPR or HIPAA.
3. Prevention Techniques:
   • Enforce Token Validation:
     • Enable strict token signature verification in AWS Cognito and other resources.
     • Use libraries like AWS Amplify or AWS SDKs to handle token validation.
   • Implement Multi-Factor Authentication (MFA):
     • Require MFA for all users, including federated identities.
     • Use device-based authentication where applicable.
   • Follow the Principle of Least Privilege:
     • Assign minimal permissions to federated roles.
     • Regularly audit and review role trust policies.
   • Enable Session Management:
     • Configure short-lived access tokens and enforce refresh token usage.
     • Invalidate tokens upon user logout or inactivity.
   • Monitor Identity Federation:
     • Use AWS CloudTrail to log and monitor federated access attempts.
     • Set up alerts for suspicious activity.

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Conclusion:

This exercise demonstrates how weak configurations in identity federation can be exploited to impersonate users or gain unauthorized access. By enforcing robust token validation, implementing MFA, and adhering to the principle of least privilege, organizations can secure their federated identity systems against similar attacks.