I need to create an application that scans fingerprints and authenticates them. I can't find anything about fingerprint permissions on the Android website.
Is it possible to use a phone's fingerprint scanner for a regular application? If so, what is the limit on the number of fingerprints it can store (I'd prefer to store them on the phone itself)
Fingerprint scanner is not a feature in Android (Now available on Android M).
So each company as Samsung, Motorola, HTC create is own API and SDK to access to fingerprint sensor.
For instance Samsung provide a SDK http://developer.samsung.com/galaxy#pass
Pass SDK allows you to use fingerprint recognition features in your application. With Pass SDK, you can provide reinforced security, since you can identify whether the current user actually is the authentic owner of the device.
If you want to enroll multiple users and check users in your app, it's not possible with Samsung device. You could only check owner of device.
I don't know SDK of other companies.
Android M have new FingerPrint API: https://developer.android.com/about/versions/marshmallow/android-6.0.html#fingerprint-authentication