# -*- coding: utf-8 -*- """ flask_principal ~~~~~~~~~~~~~~~ Identity management for Flask. :copyright: (c) 2012 by Ali Afshar. :license: MIT, see LICENSE for more details. """ from __future__ import with_statement __version__ = '0.3.5' import sys from functools import partial, wraps from collections import deque from collections import namedtuple from flask import g, session, current_app, abort, request from flask.signals import Namespace PY3 = sys.version_info[0] == 3 signals = Namespace() identity_changed = signals.signal('identity-changed', doc=""" Signal sent when the identity for a request has been changed. Actual name: ``identity-changed`` Authentication providers should send this signal when authentication has been successfully performed. Flask-Principal connects to this signal and causes the identity to be saved in the session. For example:: from flaskext.principal import Identity, identity_changed def login_view(req): username = req.form.get('username') # check the credentials identity_changed.send(app, identity=Identity(username)) """) identity_loaded = signals.signal('identity-loaded', doc=""" Signal sent when the identity has been initialised for a request. Actual name: ``identity-loaded`` Identity information providers should connect to this signal to perform two major activities: 1. Populate the identity object with the necessary authorization provisions. 2. Load any additional user information. For example:: from flaskext.principal import identity_loaded, RoleNeed, UserNeed @identity_loaded.connect def on_identity_loaded(sender, identity): # Get the user information from the db user = db.get(identity.name) # Update the roles that a user can provide for role in user.roles: identity.provides.add(RoleNeed(role.name)) # Save the user somewhere so we only look it up once identity.user = user """) Need = namedtuple('Need', ['method', 'value']) """A required need This is just a named tuple, and practically any tuple will do. The ``method`` attribute can be used to look up element 0, and the ``value`` attribute can be used to look up element 1. """ UserNeed = partial(Need, 'id') UserNeed.__doc__ = """A need with the method preset to `"id"`.""" RoleNeed = partial(Need, 'role') RoleNeed.__doc__ = """A need with the method preset to `"role"`.""" TypeNeed = partial(Need, 'type') TypeNeed.__doc__ = """A need with the method preset to `"type"`.""" ActionNeed = partial(Need, 'action') ActionNeed.__doc__ = """A need with the method preset to `"action"`.""" ItemNeed = namedtuple('ItemNeed', ['method', 'value', 'type']) """A required item need An item need is just a named tuple, and practically any tuple will do. In addition to other Needs, there is a type, for example this could be specified as:: ItemNeed('update', 27, 'posts') ('update', 27, 'posts') # or like this And that might describe the permission to update a particular blog post. In reality, the developer is free to choose whatever convention the permissions are. """ class PermissionDenied(RuntimeError): """Permission denied to the resource""" class Identity(object): """Represent the user's identity. :param id: The user id :param auth_type: The authentication type used to confirm the user's identity. The identity is used to represent the user's identity in the system. This object is created on login, or on the start of the request as loaded from the user's session. Once loaded it is sent using the `identity-loaded` signal, and should be populated with additional required information. Needs that are provided by this identity should be added to the `provides` set after loading. """ def __init__(self, id, auth_type=None): self.id = id self.auth_type = auth_type self.provides = set() def can(self, permission): """Whether the identity has access to the permission. :param permission: The permission to test provision for. """ return permission.allows(self) def __repr__(self): return '<{0} id="{1}" auth_type="{2}" provides={3}>'.format( self.__class__.__name__, self.id, self.auth_type, self.provides ) class AnonymousIdentity(Identity): """An anonymous identity""" def __init__(self): Identity.__init__(self, None) class IdentityContext(object): """The context of an identity for a permission. .. note:: The principal is usually created by the flaskext.Permission.require method call for normal use-cases. The principal behaves as either a context manager or a decorator. The permission is checked for provision in the identity, and if available the flow is continued (context manager) or the function is executed (decorator). """ def __init__(self, permission, http_exception=None): self.permission = permission self.http_exception = http_exception """The permission of this principal """ @property def identity(self): """The identity of this principal """ return g.identity def can(self): """Whether the identity has access to the permission """ return self.identity.can(self.permission) def __call__(self, f): @wraps(f) def _decorated(*args, **kw): with self: rv = f(*args, **kw) return rv return _decorated def __enter__(self): # check the permission here if not self.can(): if self.http_exception: abort(self.http_exception, self.permission) raise PermissionDenied(self.permission) def __exit__(self, *args): return False class Permission(object): """Represents needs, any of which must be present to access a resource :param needs: The needs for this permission """ def __init__(self, *needs): """A set of needs, any of which must be present in an identity to have access. """ self.needs = set(needs) self.excludes = set() def _bool(self): return bool(self.can()) def __nonzero__(self): """Equivalent to ``self.can()``. """ return self._bool() def __bool__(self): """Equivalent to ``self.can()``. """ return self._bool() def __and__(self, other): """Does the same thing as ``self.union(other)`` """ return self.union(other) def __or__(self, other): """Does the same thing as ``self.difference(other)`` """ return self.difference(other) def __contains__(self, other): """Does the same thing as ``other.issubset(self)``. """ return other.issubset(self) def __repr__(self): return '<{0} needs={1} excludes={2}>'.format( self.__class__.__name__, self.needs, self.excludes ) def require(self, http_exception=None): """Create a principal for this permission. The principal may be used as a context manager, or a decroator. If ``http_exception`` is passed then ``abort()`` will be called with the HTTP exception code. Otherwise a ``PermissionDenied`` exception will be raised if the identity does not meet the requirements. :param http_exception: the HTTP exception code (403, 401 etc) """ return IdentityContext(self, http_exception) def test(self, http_exception=None): """ Checks if permission available and raises relevant exception if not. This is useful if you just want to check permission without wrapping everything in a require() block. This is equivalent to:: with permission.require(): pass """ with self.require(http_exception): pass def reverse(self): """ Returns reverse of current state (needs->excludes, excludes->needs) """ p = Permission() p.needs.update(self.excludes) p.excludes.update(self.needs) return p def union(self, other): """Create a new permission with the requirements of the union of this and other. :param other: The other permission """ p = Permission(*self.needs.union(other.needs)) p.excludes.update(self.excludes.union(other.excludes)) return p def difference(self, other): """Create a new permission consisting of requirements in this permission and not in the other. """ p = Permission(*self.needs.difference(other.needs)) p.excludes.update(self.excludes.difference(other.excludes)) return p def issubset(self, other): """Whether this permission needs are a subset of another :param other: The other permission """ return ( self.needs.issubset(other.needs) and self.excludes.issubset(other.excludes) ) def allows(self, identity): """Whether the identity can access this permission. :param identity: The identity """ if self.needs and not self.needs.intersection(identity.provides): return False if self.excludes and self.excludes.intersection(identity.provides): return False return True def can(self): """Whether the required context for this permission has access This creates an identity context and tests whether it can access this permission """ return self.require().can() class Denial(Permission): """ Shortcut class for passing excluded needs. """ def __init__(self, *excludes): self.excludes = set(excludes) self.needs = set() def session_identity_loader(): if 'identity.id' in session and 'identity.auth_type' in session: identity = Identity(session['identity.id'], session['identity.auth_type']) return identity def session_identity_saver(identity): session['identity.id'] = identity.id session['identity.auth_type'] = identity.auth_type session.modified = True class Principal(object): """Principal extension :param app: The flask application to extend :param use_sessions: Whether to use sessions to extract and store identification. :param skip_static: Whether to ignore static endpoints. """ def __init__(self, app=None, use_sessions=True, skip_static=False): self.identity_loaders = deque() self.identity_savers = deque() # XXX This will probably vanish for a better API self.use_sessions = use_sessions self.skip_static = skip_static if app is not None: self.init_app(app) def _init_app(self, app): from warnings import warn warn(DeprecationWarning( '_init_app is deprecated, use the new init_app ' 'method instead.'), stacklevel=1 ) self.init_app(app) def init_app(self, app): if hasattr(app, 'static_url_path'): self._static_path = app.static_url_path else: self._static_path = app.static_path app.before_request(self._on_before_request) identity_changed.connect(self._on_identity_changed, app) if self.use_sessions: self.identity_loader(session_identity_loader) self.identity_saver(session_identity_saver) def set_identity(self, identity): """Set the current identity. :param identity: The identity to set """ self._set_thread_identity(identity) for saver in self.identity_savers: saver(identity) def identity_loader(self, f): """Decorator to define a function as an identity loader. An identity loader function is called before request to find any provided identities. The first found identity is used to load from. For example:: app = Flask(__name__) principals = Principal(app) @principals.identity_loader def load_identity_from_weird_usecase(): return Identity('ali') """ self.identity_loaders.appendleft(f) return f def identity_saver(self, f): """Decorator to define a function as an identity saver. An identity loader saver is called when the identity is set to persist it for the next request. For example:: app = Flask(__name__) principals = Principal(app) @principals.identity_saver def save_identity_to_weird_usecase(identity): my_special_cookie['identity'] = identity """ self.identity_savers.appendleft(f) return f def _set_thread_identity(self, identity): g.identity = identity identity_loaded.send(current_app._get_current_object(), identity=identity) def _on_identity_changed(self, app, identity): if self._is_static_route(): return self.set_identity(identity) def _on_before_request(self): if self._is_static_route(): return g.identity = AnonymousIdentity() for loader in self.identity_loaders: identity = loader() if identity is not None: self.set_identity(identity) return def _is_static_route(self): return ( self.skip_static and (self._static_path and request.path.startswith(self._static_path)) )