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re2o/api/permissions.py
2018-07-22 22:59:49 +02:00

285 lines
10 KiB
Python

# -*- mode: python; coding: utf-8 -*-
# Re2o est un logiciel d'administration développé initiallement au rezometz. Il
# se veut agnostique au réseau considéré, de manière à être installable en
# quelques clics.
#
# Copyright © 2018 Maël Kervella
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
"""Defines the permission classes used in the API.
"""
from rest_framework import permissions, exceptions
from re2o.acl import can_create, can_edit, can_delete, can_view_all
from . import acl
def can_see_api(*_, **__):
"""Check if a user can view the API.
Returns:
A function that takes a user as an argument and returns
an ACL tuple that assert this user can see the API.
"""
return lambda user: acl.can_view(user)
def _get_param_in_view(view, param_name):
"""Utility function to retrieve an attribute in a view passed in argument.
Uses the result of `{view}.get_{param_name}()` if existing else uses the
value of `{view}.{param_name}` directly.
Args:
view: The view where to look into.
param_name: The name of the attribute to look for.
Returns:
The result of the getter function if found else the value of the
attribute itself.
Raises:
AssertionError: None of the getter function or the attribute are
defined in the view.
"""
assert hasattr(view, 'get_'+param_name) \
or getattr(view, param_name, None) is not None, (
'cannot apply {} on a view that does not set '
'`.{}` or have a `.get_{}()` method.'
).format(self.__class__.__name__, param_name, param_name)
if hasattr(view, 'get_'+param_name):
param = getattr(view, 'get_'+param_name)()
assert param is not None, (
'{}.get_{}() returned None'
).format(view.__class__.__name__, param_name)
return param
return getattr(view, param_name)
class ACLPermission(permissions.BasePermission):
"""A permission class used to check the ACL to validate the permissions
of a user.
The view must define a `.get_perms_map()` or a `.perms_map` attribute.
See the wiki for the syntax of this attribute.
"""
def get_required_permissions(self, method, view):
"""Build the list of permissions required for the request to be
accepted.
Args:
method: The HTTP method name used for the request.
view: The view which is responding to the request.
Returns:
The list of ACL functions to apply to a user in order to check
if he has the right permissions.
Raises:
AssertionError: None of `.get_perms_map()` or `.perms_map` are
defined in the view.
rest_framework.exception.MethodNotAllowed: The requested method
is not allowed for this view.
"""
perms_map = _get_param_in_view(view, 'perms_map')
if method not in perms_map:
raise exceptions.MethodNotAllowed(method)
return [can_see_api()] + list(perms_map[method])
def has_permission(self, request, view):
"""Check that the user has the permissions to perform the request.
Args:
request: The request performed.
view: The view which is responding to the request.
Returns:
A boolean indicating if the user has the permission to
perform the request.
Raises:
AssertionError: None of `.get_perms_map()` or `.perms_map` are
defined in the view.
rest_framework.exception.MethodNotAllowed: The requested method
is not allowed for this view.
"""
# Workaround to ensure ACLPermissions are not applied
# to the root view when using DefaultRouter.
if getattr(view, '_ignore_model_permissions', False):
return True
if not request.user or not request.user.is_authenticated:
return False
perms = self.get_required_permissions(request.method, view)
return all(perm(request.user)[0] for perm in perms)
class AutodetectACLPermission(permissions.BasePermission):
"""A permission class used to autodetect the ACL needed to validate the
permissions of a user based on the queryset of the view.
The view must define a `.get_queryset()` or a `.queryset` attribute.
Attributes:
perms_map: The mapping of each valid HTTP method to the required
model-based ACL permissions.
perms_obj_map: The mapping of each valid HTTP method to the required
object-based ACL permissions.
"""
perms_map = {
'GET': [can_see_api, lambda model: model.can_view_all],
'OPTIONS': [can_see_api, lambda model: model.can_view_all],
'HEAD': [can_see_api, lambda model: model.can_view_all],
'POST': [can_see_api, lambda model: model.can_create],
'PUT': [], # No restrictions, apply to objects
'PATCH': [], # No restrictions, apply to objects
'DELETE': [], # No restrictions, apply to objects
}
perms_obj_map = {
'GET': [can_see_api, lambda obj: obj.can_view],
'OPTIONS': [can_see_api, lambda obj: obj.can_view],
'HEAD': [can_see_api, lambda obj: obj.can_view],
'POST': [], # No restrictions, apply to models
'PUT': [can_see_api, lambda obj: obj.can_edit],
'PATCH': [can_see_api, lambda obj: obj.can_edit],
'DELETE': [can_see_api, lambda obj: obj.can_delete],
}
def get_required_permissions(self, method, model):
"""Build the list of model-based permissions required for the
request to be accepted.
Args:
method: The HTTP method name used for the request.
view: The view which is responding to the request.
Returns:
The list of ACL functions to apply to a user in order to check
if he has the right permissions.
Raises:
rest_framework.exception.MethodNotAllowed: The requested method
is not allowed for this view.
"""
if method not in self.perms_map:
raise exceptions.MethodNotAllowed(method)
return [perm(model) for perm in self.perms_map[method]]
def get_required_object_permissions(self, method, obj):
"""Build the list of object-based permissions required for the
request to be accepted.
Args:
method: The HTTP method name used for the request.
view: The view which is responding to the request.
Returns:
The list of ACL functions to apply to a user in order to check
if he has the right permissions.
Raises:
rest_framework.exception.MethodNotAllowed: The requested method
is not allowed for this view.
"""
if method not in self.perms_obj_map:
raise exceptions.MethodNotAllowed(method)
return [perm(obj) for perm in self.perms_obj_map[method]]
def _queryset(self, view):
return _get_param_in_view(view, 'queryset')
def has_permission(self, request, view):
"""Check that the user has the model-based permissions to perform
the request.
Args:
request: The request performed.
view: The view which is responding to the request.
Returns:
A boolean indicating if the user has the permission to
perform the request.
Raises:
AssertionError: None of `.get_queryset()` or `.queryset` are
defined in the view.
rest_framework.exception.MethodNotAllowed: The requested method
is not allowed for this view.
"""
# Workaround to ensure ACLPermissions are not applied
# to the root view when using DefaultRouter.
if getattr(view, '_ignore_model_permissions', False):
return True
if not request.user or not request.user.is_authenticated:
return False
queryset = self._queryset(view)
perms = self.get_required_permissions(request.method, queryset.model)
return all(perm(request.user)[0] for perm in perms)
def has_object_permission(self, request, view, obj):
"""Check that the user has the object-based permissions to perform
the request.
Args:
request: The request performed.
view: The view which is responding to the request.
Returns:
A boolean indicating if the user has the permission to
perform the request.
Raises:
rest_framework.exception.MethodNotAllowed: The requested method
is not allowed for this view.
"""
# authentication checks have already executed via has_permission
user = request.user
perms = self.get_required_object_permissions(request.method, obj)
if not all(perm(request.user)[0] for perm in perms):
# If the user does not have permissions we need to determine if
# they have read permissions to see 403, or not, and simply see
# a 404 response.
if request.method in SAFE_METHODS:
# Read permissions already checked and failed, no need
# to make another lookup.
raise Http404
read_perms = self.get_required_object_permissions('GET', obj)
if not read_perms(request.user)[0]:
raise Http404
# Has read permissions.
return False
return True