PKCE: Where to Store Code Verifier?

The Proof Key for Code Exchange (PKCE) is a security mechanism used in OAuth 2.0 authorization to prevent attackers from obtaining authorization tokens by intercepting authorization requests.

PKCE works by generating a code verifier and a code challenge. The code verifier is a long, randomly generated string of characters, while the code challenge is a shorter, hashed version of the code verifier. The code challenge is included in the authorization request, while the code verifier is stored securely on the client. When the authorization server receives the authorization request, it verifies that the code challenge matches the hashed value of the code verifier. If they match, the authorization server issues an authorization token to the client.

Where to Store Code Verifier?

The code verifier should be stored securely on the client. This can be done in a number of ways, including:

• In a database: The code verifier can be stored in a database on the client's server. This is a relatively secure option, as the database can be protected with access control lists (ACLs) and other security measures.

• In a file: The code verifier can be stored in a file on the client's server. This is a less secure option than storing the code verifier in a database, as the file can be more easily accessed by attackers.

• In memory: The code verifier can be stored in memory on the client. This is the least secure option, as the code verifier can be easily accessed by attackers if they gain access to the client's memory.

Best Practices for Storing Code Verifier

Regardless of where you choose to store the code verifier, there are a few best practices you should follow to keep it secure:

• Use a strong code verifier: The code verifier should be a long, randomly generated string of characters. This will make it difficult for attackers to guess or brute-force the code verifier.

• Store the code verifier securely: The code verifier should be stored in a secure location on the client. This could be a database, a file, or in memory.

• Limit access to the code verifier: Only authorized personnel should have access to the code verifier. This will help to prevent unauthorized access to the code verifier.

• Monitor the code verifier: The code verifier should be monitored for suspicious activity. This could include attempts to access the code verifier, or changes to the code verifier.

Conclusion

The code verifier is a critical part of the PKCE security mechanism. By storing the code verifier securely, you can help to protect your application from attacks.

Frequently Asked Questions

1. What is the PKCE code verifier?

The PKCE code verifier is a long, randomly generated string of characters that is used to generate the code challenge. The code challenge is included in the authorization request, while the code verifier is stored securely on the client.

2. Why is it important to store the code verifier securely?

The code verifier is a critical part of the PKCE security mechanism. By storing the code verifier securely, you can help to protect your application from attacks.

3. Where can I store the code verifier?

The code verifier can be stored in a number of places, including a database, a file, or in memory. The best place to store the code verifier will depend on the specific needs of your application.

4. What are some best practices for storing the code verifier securely?

Some best practices for storing the code verifier securely include using a strong code verifier, storing the code verifier in a secure location, limiting access to the code verifier, and monitoring the code verifier for suspicious activity.

5. What should I do if my code verifier is compromised?

If your code verifier is compromised, you should immediately revoke the authorization token associated with the code verifier. You should also investigate the compromise and take steps to prevent it from happening again.