entra external id jwt no email

2 min read 22-01-2025

This article explores secure ways to manage user authentication using JSON Web Tokens (JWTs) when you need to incorporate an external ID and don't rely on email addresses. We'll cover the challenges, best practices, and potential solutions. This is crucial for systems integrating with external platforms or using unique identifiers other than email for user identification.

Why Avoid Using Email in JWTs?

While convenient, using email as the primary identifier in JWTs presents several vulnerabilities:

Privacy Concerns: Email addresses are personally identifiable information (PII). Storing them directly in JWTs increases the risk of data breaches exposing user privacy.
Email Address Changes: If a user changes their email, the existing JWTs become invalid, necessitating token revocation or regeneration across the entire system—a complex undertaking.
Brute-Force Attacks: Reliance on email alone can make systems more susceptible to brute-force attacks attempting to guess valid email/password combinations.

Integrating External IDs with JWTs

The optimal approach is to use a unique, non-PII identifier, often referred to as an external ID, as the primary claim within your JWT payload. This could be a UUID, a user ID from another system, or another unique, internally generated identifier.

1. Choosing the Right External ID

Select an ID that meets these criteria:

Uniqueness: Guarantees each user has a distinct identifier.
Persistence: Remains consistent throughout the user's lifecycle.
Non-PII: Protects user privacy by avoiding sensitive personal information.
Secure Generation: Prevents unauthorized creation or duplication.

Consider using UUIDs (Universally Unique Identifiers) or similar mechanisms to generate robust and unique identifiers.

2. JWT Payload Structure

Here’s how your JWT payload might look, incorporating the external ID:

{
  "ext_id": "a1b2c3d4-e5f6-7890-1234-567890abcdef",
  "name": "John Doe", // Optional user details
  "role": "user",    // Optional user roles
  "iat": 1678886400, // Issued at timestamp
  "exp": 1678890000  // Expiration timestamp
}

Notice the "ext_id" claim contains the unique external identifier, not the email address.

3. Secure Token Generation and Management

Key Management: Use strong, well-protected cryptographic keys for signing and verifying JWTs. Rotate keys regularly.
Token Expiration: Set appropriate expiration times for JWTs to limit the impact of compromised tokens.
Token Revocation: Implement a mechanism for revoking tokens if necessary (e.g., blacklist or a dedicated revocation service).
HTTPS: Always transmit JWTs over HTTPS to prevent interception.

4. Accessing User Information

Upon receiving a valid JWT, your backend system can use the ext_id to retrieve associated user information from your database or other data stores. This prevents storing sensitive information directly within the token.

Handling Different User Scenarios

You may need to adapt your JWT structure to handle various user scenarios such as those who log in using different methods (social logins) and those who may have multiple external systems associated with their accounts.

5. Mapping External IDs to Other Systems

If you integrate with other systems, you might need a mapping mechanism to translate between your internal ext_id and identifiers used by those systems. A dedicated lookup table in your database can effectively manage these mappings.

Security Considerations: Beyond the JWT

JWTs themselves are not a silver bullet. Consider additional security measures:

Rate Limiting: Prevent brute-force attacks by limiting the number of authentication attempts.
Input Validation: Always validate user inputs to prevent injection attacks.
Regular Security Audits: Regularly review your security practices and update your systems to address vulnerabilities.

By following these best practices, you can securely integrate external IDs into your JWT-based authentication system without relying on potentially risky information like email addresses, thereby enhancing security and user privacy. Remember to always prioritize security best practices throughout your application’s architecture.