130 lines
5.0 KiB
Python
130 lines
5.0 KiB
Python
"""authentik expression policy evaluator"""
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import re
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from textwrap import indent
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from typing import Any, Iterable, Optional
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from django.core.exceptions import FieldError
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from requests import Session
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from rest_framework.serializers import ValidationError
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from sentry_sdk.hub import Hub
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from sentry_sdk.tracing import Span
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from structlog.stdlib import get_logger
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from authentik.core.models import User
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LOGGER = get_logger()
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class BaseEvaluator:
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"""Validate and evaluate python-based expressions"""
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# Globals that can be used by function
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_globals: dict[str, Any]
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# Context passed as locals to exec()
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_context: dict[str, Any]
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# Filename used for exec
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_filename: str
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def __init__(self):
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# update website/docs/expressions/_objects.md
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# update website/docs/expressions/_functions.md
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self._globals = {
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"regex_match": BaseEvaluator.expr_regex_match,
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"regex_replace": BaseEvaluator.expr_regex_replace,
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"ak_is_group_member": BaseEvaluator.expr_is_group_member,
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"ak_user_by": BaseEvaluator.expr_user_by,
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"ak_logger": get_logger(),
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"requests": Session(),
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}
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self._context = {}
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self._filename = "BaseEvalautor"
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@staticmethod
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def expr_regex_match(value: Any, regex: str) -> bool:
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"""Expression Filter to run re.search"""
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return re.search(regex, value) is not None
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@staticmethod
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def expr_regex_replace(value: Any, regex: str, repl: str) -> str:
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"""Expression Filter to run re.sub"""
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return re.sub(regex, repl, value)
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@staticmethod
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def expr_user_by(**filters) -> Optional[User]:
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"""Get user by filters"""
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try:
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users = User.objects.filter(**filters)
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if users:
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return users.first()
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return None
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except FieldError:
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return None
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@staticmethod
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def expr_is_group_member(user: User, **group_filters) -> bool:
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"""Check if `user` is member of group with name `group_name`"""
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return user.ak_groups.filter(**group_filters).exists()
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def wrap_expression(self, expression: str, params: Iterable[str]) -> str:
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"""Wrap expression in a function, call it, and save the result as `result`"""
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handler_signature = ",".join(params)
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full_expression = ""
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full_expression += "from ipaddress import ip_address, ip_network\n"
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full_expression += f"def handler({handler_signature}):\n"
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full_expression += indent(expression, " ")
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full_expression += f"\nresult = handler({handler_signature})"
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return full_expression
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def evaluate(self, expression_source: str) -> Any:
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"""Parse and evaluate expression. If the syntax is incorrect, a SyntaxError is raised.
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If any exception is raised during execution, it is raised.
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The result is returned without any type-checking."""
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with Hub.current.start_span(op="lib.evaluator.evaluate") as span:
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span: Span
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span.set_data("expression", expression_source)
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param_keys = self._context.keys()
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try:
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ast_obj = compile(
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self.wrap_expression(expression_source, param_keys),
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self._filename,
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"exec",
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)
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except (SyntaxError, ValueError) as exc:
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self.handle_error(exc, expression_source)
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raise exc
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try:
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_locals = self._context
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# Yes this is an exec, yes it is potentially bad. Since we limit what variables are
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# available here, and these policies can only be edited by admins, this is a risk
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# we're willing to take.
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# pylint: disable=exec-used
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exec(ast_obj, self._globals, _locals) # nosec # noqa
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result = _locals["result"]
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except Exception as exc:
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# So, this is a bit questionable. Essentially, we are edit the stacktrace
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# so the user only sees information relevant to them
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# and none of our surrounding error handling
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exc.__traceback__ = exc.__traceback__.tb_next
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self.handle_error(exc, expression_source)
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raise exc
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return result
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# pylint: disable=unused-argument
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def handle_error(self, exc: Exception, expression_source: str): # pragma: no cover
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"""Exception Handler"""
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LOGGER.warning("Expression error", exc=exc)
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def validate(self, expression: str) -> bool:
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"""Validate expression's syntax, raise ValidationError if Syntax is invalid"""
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param_keys = self._context.keys()
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try:
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compile(
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self.wrap_expression(expression, param_keys),
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self._filename,
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"exec",
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)
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return True
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except (ValueError, SyntaxError) as exc:
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raise ValidationError(f"Expression Syntax Error: {str(exc)}") from exc
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