Password KDFs

A password key derivation function is designed to be expensive. For example, Argon2id consumes both CPU time and memory, making large batches of offline guesses much more costly.

import argon2 from "argon2";

export async function hashPassword(password: string): Promise<string> {
  return argon2.hash(password, {
    type: argon2.argon2id,
    memoryCost: 19 * 1024,
    timeCost: 2,
    parallelism: 1,
  });
}

Suppose your app already has users whose passwords are stored as 64-character SHA-256 hashes. Ruh-roh. Simply adding an Argon2-only verifier would lock them out!

You'll need to verify both formats during the migration, but create only Argon2id hashes for new or changed passwords:

// this regex matches exactly 64 hex characters
// meaning (in our system) it's a legacy SHA-256 hash
if (/^[a-f0-9]{64}$/i.test(passwordHash)) {
  return verifyLegacyPassword(password, passwordHash);
}

// this string starts with "$argon2id$" meaning
// the password was hashed with Argon2id
if (passwordHash.startsWith("$argon2id$")) {
  return argon2.verify(passwordHash, password);
}

return false;

Bearly Secure stores passwords with fast SHA-256 hashes. Adopt Argon2id for every new or changed password without breaking existing legacy accounts.

1. In src/auth/passwords.ts, import argon2 from argon2.
2. Change hashPassword to return an Argon2id hash with the following options:
   • type: "argon2id"
   • memoryCost: 19 * 1024
   • timeCost: 2
   • parallelism: 1
3. Change verifyPassword:
   1. Check for and verify legacy SHA-256 hashes.
   2. Try to verify Argon2id hashes.
   3. Reject malformed or incorrect hashes.
4. Update the /account/email route handler to await the password check.

Run and submit the CLI tests from the project root.