# This file is part of CherryPy <http://www.cherrypy.org/>
# -*- coding: utf-8 -*-
# vim:ts=4:sw=4:expandtab:fileencoding=utf-8

import binascii

import cherrypy
from cherrypy._cpcompat import base64_decode


__doc__ = """This module provides a CherryPy 3.x tool which implements
the server-side of HTTP Basic Access Authentication, as described in
:rfc:`2617`.

Example usage, using the built-in checkpassword_dict function which uses a dict
as the credentials store::

    userpassdict = {'bird' : 'bebop', 'ornette' : 'wayout'}
    checkpassword = cherrypy.lib.auth_basic.checkpassword_dict(userpassdict)
    basic_auth = {'tools.auth_basic.on': True,
                  'tools.auth_basic.realm': 'earth',
                  'tools.auth_basic.checkpassword': checkpassword,
    }
    app_config = { '/' : basic_auth }

"""

__author__ = 'visteya'
__date__ = 'April 2009'


def checkpassword_dict(user_password_dict):
    """Returns a checkpassword function which checks credentials
    against a dictionary of the form: {username : password}.

    If you want a simple dictionary-based authentication scheme, use
    checkpassword_dict(my_credentials_dict) as the value for the
    checkpassword argument to basic_auth().
    """
    def checkpassword(realm, user, password):
        p = user_password_dict.get(user)
        return p and p == password or False

    return checkpassword


def basic_auth(realm, checkpassword, debug=False):
    """A CherryPy tool which hooks at before_handler to perform
    HTTP Basic Access Authentication, as specified in :rfc:`2617`.

    If the request has an 'authorization' header with a 'Basic' scheme, this
    tool attempts to authenticate the credentials supplied in that header.  If
    the request has no 'authorization' header, or if it does but the scheme is
    not 'Basic', or if authentication fails, the tool sends a 401 response with
    a 'WWW-Authenticate' Basic header.

    realm
        A string containing the authentication realm.

    checkpassword
        A callable which checks the authentication credentials.
        Its signature is checkpassword(realm, username, password). where
        username and password are the values obtained from the request's
        'authorization' header.  If authentication succeeds, checkpassword
        returns True, else it returns False.

    """

    if '"' in realm:
        raise ValueError('Realm cannot contain the " (quote) character.')
    request = cherrypy.serving.request

    auth_header = request.headers.get('authorization')
    if auth_header is not None:
        # split() error, base64.decodestring() error
        with cherrypy.HTTPError.handle((ValueError, binascii.Error), 400, 'Bad Request'):
            scheme, params = auth_header.split(' ', 1)
            if scheme.lower() == 'basic':
                username, password = base64_decode(params).split(':', 1)
                if checkpassword(realm, username, password):
                    if debug:
                        cherrypy.log('Auth succeeded', 'TOOLS.AUTH_BASIC')
                    request.login = username
                    return  # successful authentication

    # Respond with 401 status and a WWW-Authenticate header
    cherrypy.serving.response.headers[
        'www-authenticate'] = 'Basic realm="%s"' % realm
    raise cherrypy.HTTPError(
        401, 'You are not authorized to access that resource')
