Setting Up a Private Self-Hosted OIDC Provider on AWS for Enhanced Authentication

In today’s digital landscape, securing access to cloud resources is paramount. This blog post delves into setting up a private self-hosted OpenID Connect (OIDC) provider on AWS, offering a robust solution for applications requiring secure authentication. Whether you’re managing internal tools, CI/CD pipelines, or IoT devices, this approach provides a scalable and secure authentication mechanism.

Introduction to OIDC and AWS Integration

OIDC, an extension of OAuth 2.0, enables secure authentication by issuing tokens that can be used to access resources. By hosting your own OIDC provider on AWS, you gain control over the authentication process, ensuring it aligns with your security policies. This setup is particularly beneficial for applications using AWS Lambda or API Gateway, as it allows seamless integration with AWS services.

Architecture Overview

The architecture involves three key components:

  1. OIDC Provider: Hosted on AWS, this provider authenticates users and issues tokens. It can be deployed using EC2, Lambda, or a container service like ECS.
  2. AWS Services: These include Lambda, API Gateway, and IAM, which utilize the tokens issued by the OIDC provider to grant access.
  3. Client Applications: These are your internal tools, pipelines, or devices that authenticate with the OIDC provider and use the tokens to access AWS resources.

Setting Up the OIDC Provider

To set up the OIDC provider:

  1. Choose a Technology Stack: Use libraries like Authlib or Keycloak, or implement a custom solution using AWS services.
  2. Secure Token Issuance: Ensure tokens are signed with secure certificates, stored in AWS KMS or Secrets Manager.
  3. Configure OAuth Flows: Implement the authorization code flow for web applications and token exchange for server-to-server communication.

Integration with AWS Services

  1. IAM Role Configuration: Configure IAM roles to trust your OIDC provider. Specify the provider’s URL and client ID in the trust policy.
  2. Token Exchange: Applications authenticate with the OIDC provider to obtain tokens, which are then used with AWS STS to get temporary credentials.

Real-World Use Cases

  • Internal Tools: Secure access for internal applications using a private OIDC provider.
  • CI/CD Pipelines: Automate secure access to AWS resources without hardcoding credentials.
  • IoT Devices: Enable lightweight, token-based authentication for IoT devices.

Best Practices

  • Secure Credential Management: Use AWS KMS for secure storage of private keys and credentials.
  • Regular Audits and Monitoring: Utilize CloudWatch for monitoring and audit logs to detect anomalies.
  • Least Privilege: Grant minimal necessary permissions to reduce risk.

Code Examples

Example 1: Lambda Function for Token Retrieval

import requests
import json
import boto3

def lambda_handler(event, context):
    # OIDC provider configuration
    oidc_url = 'https://your-oidc-provider/oauth2/token'
    client_id = 'your_client_id'
    client_secret = 'your_client_secret'
    
    # Request access token
    response = requests.post(
        oidc_url,
        data={
            'grant_type': 'client_credentials',
            'client_id': client_id,
            'client_secret': client_secret
        }
    )
    
    access_token = response.json()['access_token']
    
    # Assume AWS role using STS
    sts = boto3.client('sts')
    response = sts.assume_role_with_web_identity(
        RoleArn='arn:aws:iam::123456789012:role/_oidc_role',
        WebIdentityToken=access_token,
        RoleSessionName='OIDCSession'
    )
    
    return {
        'statusCode': 200,
        'body': json.dumps(response['Credentials'])
    }

Example 2: API Gateway Integration

import requests
import json
import boto3

def lambda_handler(event, context):
    # Extract token from request
    token = event.get('headers', {}).get('Authorization', '').split('Bearer ')[1]
    
    # Validate token with OIDC provider
    # (Implementation details omitted for brevity)
    
    # Assume AWS role using STS
    sts = boto3.client('sts')
    response = sts