Using iOS Keychain with AWS Amplify authentication?

My app uses AWS Amplify’s withAuthenticator (from aws-amplify-react-native) to handle user authentication; essentially the basic boiler plate app plus

export default withAuthenticator( App )

But out of the box this does not save or retrieve the user’s password in the OS (in my current case iOS) keychain, and it’s unclear

  1. where to find the user’s password, and
  2. how to save the user’s password in the OS keychain.

As near as I can tell Amplify’s Auth has no methods for retrieve the password, though I gather the way to store the password is to use expo-secure-store.

I’m sure this is a very basic question — since signing in without platform keychain integration is pretty much useless — but I can’t find any good examples, and my documentation search is coming up against dead ends. Any getting off to the right start is appreciated!