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authentik/passbook/policies/expression/evaluator.py

85 lines
3.3 KiB
Python

"""passbook expression policy evaluator"""
import re
from typing import TYPE_CHECKING, Any, Dict
from django.core.exceptions import ValidationError
from jinja2.exceptions import TemplateSyntaxError, UndefinedError
from jinja2.nativetypes import NativeEnvironment
from structlog import get_logger
from passbook.factors.view import AuthenticationView
from passbook.policies.struct import PolicyRequest, PolicyResult
if TYPE_CHECKING:
from passbook.core.models import User
class Evaluator:
"""Validate and evaulate jinja2-based expressions"""
_env: NativeEnvironment
def __init__(self):
self._env = NativeEnvironment()
# update passbook/policies/expression/templates/policy/expression/form.html
# update docs/policies/expression/index.md
self._env.filters["regex_match"] = Evaluator.jinja2_filter_regex_match
self._env.filters["regex_replace"] = Evaluator.jinja2_filter_regex_replace
@staticmethod
def jinja2_filter_regex_match(value: Any, regex: str) -> bool:
"""Jinja2 Filter to run re.search"""
return re.search(regex, value) is None
@staticmethod
def jinja2_filter_regex_replace(value: Any, regex: str, repl: str) -> str:
"""Jinja2 Filter to run re.sub"""
return re.sub(regex, repl, value)
@staticmethod
def jinja2_func_is_group_member(user: "User", group_name: str) -> bool:
"""Check if `user` is member of group with name `group_name`"""
return user.groups.filter(name=group_name).exists()
def _get_expression_context(
self, request: PolicyRequest, **kwargs
) -> Dict[str, Any]:
"""Return dictionary with additional global variables passed to expression"""
# update passbook/policies/expression/templates/policy/expression/form.html
# update docs/policies/expression/index.md
kwargs["pb_is_sso_flow"] = request.http_request.session.get(
AuthenticationView.SESSION_IS_SSO_LOGIN, False
)
kwargs["pb_is_group_member"] = Evaluator.jinja2_func_is_group_member
kwargs["pb_logger"] = get_logger()
return kwargs
def evaluate(self, expression_source: str, request: PolicyRequest) -> PolicyResult:
"""Parse and evaluate expression.
If the Expression evaluates to a list with 2 items, the first is used as passing bool and
the second as messages.
If the Expression evaluates to a truthy-object, it is used as passing bool."""
try:
expression = self._env.from_string(expression_source)
except TemplateSyntaxError as exc:
return PolicyResult(False, str(exc))
try:
result = expression.render(
request=request, **self._get_expression_context(request)
)
if isinstance(result, list) and len(result) == 2:
return PolicyResult(*result)
if result:
return PolicyResult(result)
return PolicyResult(False)
except UndefinedError as exc:
return PolicyResult(False, str(exc))
def validate(self, expression: str):
"""Validate expression's syntax, raise ValidationError if Syntax is invalid"""
try:
self._env.from_string(expression)
return True
except TemplateSyntaxError as exc:
raise ValidationError("Expression Syntax Error") from exc