auth.py

from django.conf import settings
from django.contrib.auth.models import User
import cx_Oracle

class OracleBackend(object):
    """Authenticate by attempting to establish an oracle connection.
    Uses the database from the settings.  The django user module is
    still used for management, just not authentication."""
    def authenticate(self, username=None, password=None):
        try:
            dsn = cx_Oracle.makedsn(settings.DATABASE_HOST, settings.DATABASE_PORT, settings.DATABASE_NAME)
            connection = cx_Oracle.connect(str('%s/%s@%s' % (username, password, dsn)))
            connection.close()
            # valid, so log them in:
            try:
                user = User.objects.get(username=username)
            except User.DoesNotExist:
                user = User(username=username, password='')
                user.set_unusable_password()
                user.is_staff = True
                user.is_superuser = False

                user.save()
            return user
        except: # probably DatabaseError, but I'll catch everything to be safe
            return None

middleware.py

class UserDBConnection(object):
    """If the user is logged in (assumed if their password is in the
    session!), the global connection object is updated to use their
    connection credentials instead of the default Django ones."""
    def process_request(self, request):
        if 'password' in request.session:
            from django import db
            from django.conf import settings
            username = request.user.username
            password = request.session['password']

            db.connection.settings_dict['DATABASE_USER'] = username
            db.connection.settings_dict['DATABASE_PASSWORD'] = password
        return None

models.py

def set_schema(sender, **kwargs):
    from django.db import connection
    from django.conf import settings 
    cursor = connection.cursor()
    cursor.execute('alter session set current_schema=%s' % settings.DEFAULT_SCHEMA)
if set_schema not in connection_created.receivers:
    connection_created.connect(set_schema)