mirror of https://gitlab.crans.org/bde/nk20
226 lines
8.2 KiB
Python
226 lines
8.2 KiB
Python
# Copyright (C) 2018-2020 by BDE ENS Paris-Saclay
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# SPDX-License-Identifier: GPL-3.0-or-later
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import functools
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import json
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import operator
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from django.contrib.contenttypes.models import ContentType
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from django.core.exceptions import ValidationError
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from django.db import models
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from django.db.models import F, Q, Model
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from django.utils.translation import gettext_lazy as _
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class InstancedPermission:
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def __init__(self, model, query, type, field, mask):
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self.model = model
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self.query = query
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self.type = type
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self.field = field
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self.mask = mask
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def applies(self, obj, permission_type, field_name=None):
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"""
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Returns True if the permission applies to
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the field `field_name` object `obj`
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"""
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if not isinstance(obj, self.model.model_class()):
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# The permission does not apply to the model
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return False
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if self.type == 'add':
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if permission_type == self.type:
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# Don't increase indexes
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obj.pk = 0
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# Force insertion, no data verification, no trigger
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Model.save(obj, force_insert=True)
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ret = obj in self.model.model_class().objects.filter(self.query).all()
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# Delete testing object
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Model.delete(obj)
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return ret
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if permission_type == self.type:
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if self.field and field_name != self.field:
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return False
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return obj in self.model.model_class().objects.filter(self.query).all()
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else:
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return False
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def __repr__(self):
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if self.field:
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return _("Can {type} {model}.{field} in {query}").format(type=self.type, model=self.model, field=self.field, query=self.query)
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else:
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return _("Can {type} {model} in {query}").format(type=self.type, model=self.model, query=self.query)
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def __str__(self):
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return self.__repr__()
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class PermissionMask(models.Model):
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rank = models.PositiveSmallIntegerField(
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unique=True,
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verbose_name=_('rank'),
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)
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description = models.CharField(
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max_length=255,
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unique=True,
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verbose_name=_('description'),
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)
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def __str__(self):
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return self.description
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class Permission(models.Model):
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PERMISSION_TYPES = [
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('add', 'add'),
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('view', 'view'),
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('change', 'change'),
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('delete', 'delete')
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]
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model = models.ForeignKey(ContentType, on_delete=models.CASCADE, related_name='+')
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# A json encoded Q object with the following grammar
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# query -> [] | {} (the empty query representing all objects)
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# query -> ["AND", query, …] AND multiple queries
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# | ["OR", query, …] OR multiple queries
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# | ["NOT", query] Opposite of query
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# query -> {key: value, …} A list of fields and values of a Q object
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# key -> string A field name
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# value -> int | string | bool | null Literal values
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# | [parameter] A parameter
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# | {"F": oper} An F object
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# oper -> [string] A parameter
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# | ["ADD", oper, …] Sum multiple F objects or literal
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# | ["SUB", oper, oper] Substract two F objects or literal
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# | ["MUL", oper, …] Multiply F objects or literals
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# | int | string | bool | null Literal values
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# | ["F", string] A field
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#
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# Examples:
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# Q(is_superuser=True) := {"is_superuser": true}
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# ~Q(is_superuser=True) := ["NOT", {"is_superuser": true}]
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query = models.TextField()
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type = models.CharField(max_length=15, choices=PERMISSION_TYPES)
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mask = models.ForeignKey(
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PermissionMask,
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on_delete=models.PROTECT,
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)
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field = models.CharField(max_length=255, blank=True)
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description = models.CharField(max_length=255, blank=True)
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class Meta:
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unique_together = ('model', 'query', 'type', 'field')
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def clean(self):
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self.query = json.dumps(json.loads(self.query))
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if self.field and self.type not in {'view', 'change'}:
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raise ValidationError(_("Specifying field applies only to view and change permission types."))
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def save(self, **kwargs):
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self.full_clean()
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super().save()
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@staticmethod
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def compute_f(oper, **kwargs):
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if isinstance(oper, list):
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if oper[0] == 'ADD':
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return functools.reduce(operator.add, [Permission.compute_f(oper, **kwargs) for oper in oper[1:]])
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elif oper[0] == 'SUB':
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return Permission.compute_f(oper[1], **kwargs) - Permission.compute_f(oper[2], **kwargs)
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elif oper[0] == 'MUL':
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return functools.reduce(operator.mul, [Permission.compute_f(oper, **kwargs) for oper in oper[1:]])
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elif oper[0] == 'F':
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return F(oper[1])
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else:
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field = kwargs[oper[0]]
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for i in range(1, len(oper)):
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field = getattr(field, oper[i])
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return field
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else:
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return oper
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@staticmethod
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def compute_param(value, **kwargs):
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if not isinstance(value, list):
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return value
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field = kwargs[value[0]]
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for i in range(1, len(value)):
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if isinstance(value[i], list):
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if value[i][0] in kwargs:
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field = Permission.compute_param(value[i], **kwargs)
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continue
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field = getattr(field, value[i][0])
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params = []
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call_kwargs = {}
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for j in range(1, len(value[i])):
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param = Permission.compute_param(value[i][j], **kwargs)
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if isinstance(param, dict):
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for key in param:
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val = Permission.compute_param(param[key], **kwargs)
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call_kwargs[key] = val
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else:
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params.append(param)
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field = field(*params, **call_kwargs)
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else:
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field = getattr(field, value[i])
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return field
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def _about(self, query, **kwargs):
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if len(query) == 0:
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# The query is either [] or {} and
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# applies to all objects of the model
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# to represent this we return a trivial request
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return Q(pk=F("pk"))
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if isinstance(query, list):
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if query[0] == 'AND':
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return functools.reduce(operator.and_, [self._about(query, **kwargs) for query in query[1:]])
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elif query[0] == 'OR':
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return functools.reduce(operator.or_, [self._about(query, **kwargs) for query in query[1:]])
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elif query[0] == 'NOT':
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return ~self._about(query[1], **kwargs)
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elif isinstance(query, dict):
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q_kwargs = {}
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for key in query:
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value = query[key]
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if isinstance(value, list):
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# It is a parameter we query its return value
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q_kwargs[key] = Permission.compute_param(value, **kwargs)
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elif isinstance(value, dict):
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# It is an F object
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q_kwargs[key] = Permission.compute_f(value['F'], **kwargs)
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else:
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q_kwargs[key] = value
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return Q(**q_kwargs)
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else:
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# TODO: find a better way to crash here
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raise Exception("query {} is wrong".format(self.query))
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def about(self, **kwargs):
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"""
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Return an InstancedPermission with the parameters
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replaced by their values and the query interpreted
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"""
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query = json.loads(self.query)
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query = self._about(query, **kwargs)
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return InstancedPermission(self.model, query, self.type, self.field, self.mask)
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def __str__(self):
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if self.field:
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return _("Can {type} {model}.{field} in {query}").format(type=self.type, model=self.model, field=self.field, query=self.query)
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else:
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return _("Can {type} {model} in {query}").format(type=self.type, model=self.model, query=self.query)
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