Use REST API to verify user password

Is there a REST API in Kentico for validating user passwords?

Background: We are looking to move to single sign-on (SSO), using a separate identity provider (IDP) for logins via OIDC. We'd prefer that users continue to use their existing usernames and passwords when logging into the IDP. We can't just copy existing user passwords from Kentico to the IDP because they are all hashed. However, the IDP offers the ability to validate a user's password when they login. They do this in the following way:

1. User enters username and password into IDP
2. If IDP finds that username and password do not exist in its database, it makes a REST call to external system (Kentico) validating that the username and password are correct
3. If the external system validates that the username and password are correct, the IDP creates a new user account in its database using the username and password.

I'm asking to see if Kentico has a REST API that supports step #2 above. We are using Kentico 12.1.

Thank you,

Paul