fix password is not bytes in mysql

[00Kai0]

Hi @leportella . I use mysql database as backend.
The log:

 HTTPServerRequest(protocol='http', host='localhost:8000', method='POST', uri='/hub/login?next=', version='HTTP/1.1', remote_ip='::ffff:127.0.0.1')
    Traceback (most recent call last):
      File "/home/kai/work/embark3_env/venv/lib/python3.5/site-packages/tornado/web.py", line 1592, in _execute
        result = yield result
      File "/usr/lib/python3.5/asyncio/futures.py", line 274, in result
        raise self._exception
      File "/home/kai/work/embark3_env/venv/lib/python3.5/site-packages/jupyterhub/handlers/login.py", line 82, in post
        user = yield self.login_user(data)
      File "/usr/lib/python3.5/asyncio/futures.py", line 274, in result
        raise self._exception
      File "/home/kai/work/embark3_env/venv/lib/python3.5/site-packages/jupyterhub/handlers/base.py", line 327, in login_user
        authenticated = yield self.authenticate(data)
      File "/usr/lib/python3.5/asyncio/futures.py", line 274, in result
        raise self._exception
      File "/home/kai/work/embark3_env/venv/lib/python3.5/site-packages/jupyterhub/auth.py", line 221, in get_authenticated_user
        authenticated = yield self.authenticate(handler, data)
      File "/usr/lib/python3.5/asyncio/futures.py", line 274, in result
        raise self._exception
      File "/home/kai/work/embark3_env/venv/lib/python3.5/types.py", line 243, in wrapped
        coro = func(*args, **kwargs)
      File "/home/kai/work/embark3_env/nativeauthenticator/nativeauthenticator/nativeauthenticator.py", line 114, in authenticate
        if user.is_authorized and user.is_valid_password(password):
      File "/home/kai/work/embark3_env/nativeauthenticator/nativeauthenticator/orm.py", line 26, in is_valid_password
        encoded_pw = bcrypt.hashpw(password.encode(), self.password)
      File "/home/kai/work/embark3_env/venv/lib/python3.5/site-packages/bcrypt/__init__.py", line 61, in hashpw
        raise TypeError("Unicode-objects must be encoded before hashing")
    TypeError: Unicode-objects must be encoded before hashing

The issue is that mysql can not save password as bytes although the return of bcrypt.hashpw is bytes in nativeauthenticator.py

encoded_pw = bcrypt.hashpw(pw.encode(), bcrypt.gensalt())
infos = {'username': username, 'password': encoded_pw}
infos.update(kwargs)

[yuvipanda]

Thanks for opening this, @00Kai0.

I think the problem is that the password hash is a binary byte string but we're storing it as string. I think the right solution is to change the type of the password column in https://github.com/jupyterhub/nativeauthenticator/blob/master/nativeauthenticator/orm.py#L13 to https://docs.sqlalchemy.org/en/latest/core/type_basics.html#sqlalchemy.types.BINARY or LARGEBINARY.

[yuvipanda]

This is not a problem for sqlite because it doesn't really enforce types, but would be for most other databases.

[00Kai0]

@yuvipanda , I think it works.

[leportella]

Thank you @00Kai0 !