Should I Rotate the Refresh Token When Refreshing JWT Access Tokens?

Below is some advice and best practices when handling rotating refresh tokens:

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Refresh Token Rotation

Recommendation: It’s generally considered a best practice to issue a new refresh token along with the new access token whenever the /auth/refresh endpoint is called. This process is known as refresh token rotation.

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Benefits of Rotating Refresh Tokens

1. Shorter Window for Exploitation:
   If an attacker manages to steal a refresh token, using a rotating strategy minimizes the time window during which that stolen token remains valid.

2. Replay Detection:
   If the server detects an old (previously used) refresh token, it can flag a potential replay attack and potentially revoke all tokens for that session.

3. Enhanced Security Posture:
   In combination with revocation and anomaly detection, rotating tokens allow you to mitigate risks in the event of a token compromise.

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Invalidating the Old Refresh Token

When issuing a new refresh token, you need to invalidate the old one. Here are common approaches:

1. Maintain a Token Store:
   Keep a database or in-memory store where each refresh token is recorded along with its status. When a user refreshes:

   • Verify the refresh token from the database.
   • Invalidate (or remove) the used token.
   • Issue a new refresh token and store it.

   Example (pseudocode):

   JSCopied
   // Pseudocode for handling token refresh
   function refreshTokens(oldRefreshToken) {
     // Check if oldRefreshToken exists and is valid in your store
     const tokenRecord = tokenStore.find(oldRefreshToken);
     if (!tokenRecord || tokenRecord.revoked) {
       throw new Error("Invalid refresh token");
     }
   
     // Invalidate the old token
     tokenStore.invalidate(oldRefreshToken);
   
     // Generate new tokens
     const newAccessToken = generateAccessToken();
     const newRefreshToken = generateRefreshToken();
   
     // Store the new refresh token
     tokenStore.store(newRefreshToken, { userId: tokenRecord.userId, revoked: false });
   
     return { accessToken: newAccessToken, refreshToken: newRefreshToken };
   }

2. Stateless Alternatives:
   If you prefer a stateless approach with JWTs, you may:

   • Embed a token version or nonce in the refresh token.
   • Store that version/nonce in the user’s profile on the server.
   • Verify that the token’s embedded value matches the one on record.

   When the token is rotated, update the nonce. This way, the old token (with an outdated nonce) is automatically invalid.

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Considerations

• Complexity vs. Security:
  If your application is okay with storing tokens on the server (or tracking token versioning), refresh token rotation offers additional security benefits at the cost of complexity.

• Revocation Strategies:
  In case of suspected compromise, having a token store or a revocation mechanism allows you to proactively invalidate tokens.

• Monitoring and Alerts:
  When an attempt to reuse an old refresh token is detected, this might be a signal of an attack. Logging these events and triggering a security response can further fortify your system.

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Conclusion

By rotating your refresh tokens:

• You reduce the risk associated with long-lasting tokens,
• Benefit from early detection of token replay attacks, and
• Maintain a more robust security system.

Thus, issuing a new refresh token alongside the new access token is advisable if your application can handle this additional complexity.

Feel free to ask if you have more detailed questions or need further clarification.