Import MD5 passwords in Firebase Authentication

Question

I am after importing identities into Firebase including password hashes.

The legacy password hash algo is a salted MD5 with 16384 rounds, which seems to be common in some Drupal or Typo3 instances.

It seems that Firebase supports only 8192 rounds for MD5 though: https://firebase.google.com/docs/auth/admin/import-users?hl=en#import_users_with_md5_sha_and_pbkdf_hashed_passwords

What are my options given I don't want to force users to change their password after the migration? In other words the old password should be imported along with user profile data and users should be able to login with the same password after the migration to Firebase.

I haven't seen this in Firebase auth but is there an option to use a custom hashing validation endpoint to encode plain text on the fly just before rehashing once migrated?

Answer 1

Got an answer from Firebase support:

At the moment there is no workaround for these particular cases, the engineering team has been notified that this is an urgent feature for the product, however there is no specifics yet.