mediagoblin/plugins/api/tools.py

   1 # GNU MediaGoblin -- federated, autonomous media hosting
   2 # Copyright (C) 2011, 2012 MediaGoblin contributors.  See AUTHORS.
   3 #
   4 # This program is free software: you can redistribute it and/or modify
   5 # it under the terms of the GNU Affero General Public License as published by
   6 # the Free Software Foundation, either version 3 of the License, or
   7 # (at your option) any later version.
   8 #
   9 # This program is distributed in the hope that it will be useful,
  10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 # GNU Affero General Public License for more details.
  13 #
  14 # You should have received a copy of the GNU Affero General Public License
  15 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 import logging
  18 import json
  19
  20 from functools import wraps
  21 from urlparse import urljoin
  22 from werkzeug.exceptions import Forbidden
  23 from werkzeug.wrappers import Response
  24 from mediagoblin import mg_globals
  25 from mediagoblin.tools.pluginapi import PluginManager
  26 from mediagoblin.storage.filestorage import BasicFileStorage
  27
  28 _log = logging.getLogger(__name__)
  29
  30
  31 class Auth(object):
  32     '''
  33     An object with two significant methods, 'trigger' and 'run'.
  34
  35     Using a similar object to this, plugins can register specific
  36     authentication logic, for example the GET param 'access_token' for OAuth.
  37
  38     - trigger: Analyze the 'request' argument, return True if you think you
  39       can handle the request, otherwise return False
  40     - run: The authentication logic, set the request.user object to the user
  41       you intend to authenticate and return True, otherwise return False.
  42
  43     If run() returns False, an HTTP 403 Forbidden error will be shown.
  44
  45     You may also display custom errors, just raise them within the run()
  46     method.
  47     '''
  48     def trigger(self, request):
  49         raise NotImplemented()
  50
  51     def __call__(self, request, *args, **kw):
  52         raise NotImplemented()
  53
  54
  55 def json_response(serializable, _disable_cors=False, *args, **kw):
  56     '''
  57     Serializes a json objects and returns a werkzeug Response object with the
  58     serialized value as the response body and Content-Type: application/json.
  59
  60     :param serializable: A json-serializable object
  61
  62     Any extra arguments and keyword arguments are passed to the
  63     Response.__init__ method.
  64     '''
  65     response = Response(json.dumps(serializable), *args, content_type='application/json', **kw)
  66
  67     if not _disable_cors:
  68         cors_headers = {
  69                 'Access-Control-Allow-Origin': '*',
  70                 'Access-Control-Allow-Methods': 'POST, GET, OPTIONS',
  71                 'Access-Control-Allow-Headers': 'Content-Type, X-Requested-With'}
  72         (response.headers.set(key, value) for key, value in cors_headers)
  73
  74     return response
  75
  76
  77 def get_entry_serializable(entry, urlgen):
  78     '''
  79     Returns a serializable dict() of a MediaEntry instance.
  80
  81     :param entry: A MediaEntry instance
  82     :param urlgen: An urlgen instance, can be found on the request object passed
  83     to views.
  84     '''
  85     return {
  86             'user': entry.get_uploader.username,
  87             'user_id': entry.get_uploader.id,
  88             'user_bio': entry.get_uploader.bio,
  89             'user_bio_html': entry.get_uploader.bio_html,
  90             'user_permalink': urlgen('mediagoblin.user_pages.user_home',
  91                 user=entry.get_uploader.username,
  92                 qualified=True),
  93             'id': entry.id,
  94             'created': entry.created.isoformat(),
  95             'title': entry.title,
  96             'license': entry.license,
  97             'description': entry.description,
  98             'description_html': entry.description_html,
  99             'media_type': entry.media_type,
 100             'state': entry.state,
 101             'permalink': entry.url_for_self(urlgen, qualified=True),
 102             'media_files': get_media_file_paths(entry.media_files, urlgen)}
 103
 104
 105 def get_media_file_paths(media_files, urlgen):
 106     '''
 107     Returns a dictionary of media files with `file_handle` => `qualified URL`
 108
 109     :param media_files: dict-like object consisting of `file_handle => `listy
 110     filepath` pairs.
 111     :param urlgen: An urlgen object, usually found on request.urlgen.
 112     '''
 113     media_urls = {}
 114
 115     for key, val in media_files.items():
 116         if isinstance(mg_globals.public_store, BasicFileStorage):
 117             # BasicFileStorage does not provide a qualified URI
 118             media_urls[key] = urljoin(
 119                     urlgen('index', qualified=True),
 120                     mg_globals.public_store.file_url(val))
 121         else:
 122             media_urls[key] = mg_globals.public_store.file_url(val)
 123
 124     return media_urls
 125
 126
 127 def api_auth(controller):
 128     '''
 129     Decorator, allows plugins to register auth methods that will then be
 130     evaluated against the request, finally a worthy authenticator object is
 131     chosen and used to decide whether to grant or deny access.
 132     '''
 133     @wraps(controller)
 134     def wrapper(request, *args, **kw):
 135         auth_candidates = []
 136
 137         for auth in PluginManager().get_hook_callables('auth'):
 138             if auth.trigger(request):
 139                 _log.debug('{0} believes it is capable of authenticating this request.'.format(auth))
 140                 auth_candidates.append(auth)
 141
 142         # If we can't find any authentication methods, we should not let them
 143         # pass.
 144         if not auth_candidates:
 145             raise Forbidden()
 146
 147         # For now, just select the first one in the list
 148         auth = auth_candidates[0]
 149
 150         _log.debug('Using {0} to authorize request {1}'.format(
 151             auth, request.url))
 152
 153         if not auth(request, *args, **kw):
 154             if getattr(auth, 'errors', []):
 155                 return json_response({
 156                         'status': 403,
 157                         'errors': auth.errors})
 158
 159             raise Forbidden()
 160
 161         return controller(request, *args, **kw)
 162
 163     return wrapper