one-time JWT token with JWT ID claim

Question

I'm trying to figure out how to issue a one-time use JWT token for password reset feature and still keeping it stateless. Came across Single-Use Tokens w/ JWT which basically suggests to include hash of current password which in turn gets invalidated once the password is changed successfully.

I don't feel comfortable including the password hash in JWT so I researched a bit and found JWT ID specification but that requires to store the ID somewhere so it can be checked on token validation.

So my question is, what are the security concerns if I include the current password hash in the password reset link token which is sent over email?

Is it better to use a JWT ID and add that as a column somewhere in the database instead of using the password?

Answer 1

I hesitate to roll my own security, but just for the fun of it here is an idea.

Instead of including the password hash, follow this process when generating the JWT:

1. Obtain the password hash
2. Obtain a server-side secret key (256 bits entropy should do it)
3. Compute an expiration timestamp, say an hour from the current time
4. Create a new hash over 1 + 2 + 3
5. Include the hash and the expiration timestamp in the JWT

To validate a password reset request:

1. Obtain the password hash
2. Obtain the server-side secret key
3. Read (and check) the expiration timestamp from the JWT
4. Compute a new hash over 1 + 2 +3
5. Compare to the hash in the JWT

This way you don't expose the password hash, and it cannot be brute-forced without also brute-forcing the secret key (which would take millions of years). And you also preclude the hash from reuse by embedding the timestamp in it.