78 lines
2.9 KiB
Python
78 lines
2.9 KiB
Python
"""passbook expression policy evaluator"""
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import re
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from typing import TYPE_CHECKING, Any, Dict
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from django.core.exceptions import ValidationError
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from jinja2.exceptions import TemplateSyntaxError, UndefinedError
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from jinja2.nativetypes import NativeEnvironment
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from structlog import get_logger
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from passbook.factors.view import AuthenticationView
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from passbook.policies.struct import PolicyRequest, PolicyResult
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if TYPE_CHECKING:
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from passbook.policies.expression.models import ExpressionPolicy
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class Evaluator:
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"""Validate and evaulate jinja2-based expressions"""
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_env: NativeEnvironment
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def __init__(self):
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self._env = NativeEnvironment()
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self._env.filters["regex_match"] = Evaluator.jinja2_regex_match
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self._env.filters["regex_replace"] = Evaluator.jinja2_regex_replace
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@staticmethod
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def jinja2_regex_match(value: Any, regex: str) -> bool:
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"""Jinja2 Filter to run re.search"""
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return re.search(regex, value) is None
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@staticmethod
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def jinja2_regex_replace(value: Any, regex: str, repl: str) -> str:
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"""Jinja2 Filter to run re.sub"""
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return re.sub(regex, repl, value)
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def _get_expression_context(
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self, request: PolicyRequest, **kwargs
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) -> Dict[str, Any]:
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"""Return dictionary with additional global variables passed to expression"""
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kwargs["pb_is_sso_flow"] = request.user.session.get(
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AuthenticationView.SESSION_IS_SSO_LOGIN, False
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)
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kwargs["pb_is_group_member"] = lambda user, group: group.user_set.filter(
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pk=user.pk
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).exists()
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kwargs["pb_logger"] = get_logger()
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return kwargs
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def evaluate(self, expression_source: str, request: PolicyRequest) -> PolicyResult:
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"""Parse and evaluate expression.
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If the Expression evaluates to a list with 2 items, the first is used as passing bool and
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the second as messages.
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If the Expression evaluates to a truthy-object, it is used as passing bool."""
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try:
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expression = self._env.from_string(expression_source)
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except TemplateSyntaxError as exc:
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return PolicyResult(False, str(exc))
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try:
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result = expression.render(
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request=request, **self._get_expression_context(request)
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)
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if isinstance(result, list) and len(result) == 2:
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return PolicyResult(*result)
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if result:
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return PolicyResult(result)
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return PolicyResult(False)
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except UndefinedError as exc:
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return PolicyResult(False, str(exc))
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def validate(self, expression: str):
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"""Validate expression's syntax, raise ValidationError if Syntax is invalid"""
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try:
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self._env.from_string(expression)
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return True
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except TemplateSyntaxError as exc:
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raise ValidationError("Expression Syntax Error") from exc
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