make it work

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

authentik/api/authentication.py

@@ -73,6 +73,11 @@ def auth_user_lookup(raw_header: bytes) -> User | None:
     if user:
         CTX_AUTH_VIA.set("secret_key")
         return user
+    # then try to auth via expression JWT
+    user = token_expression_jwt(auth_credentials)
+    if user:
+        CTX_AUTH_VIA.set("expression_jwt")
+        return user
     raise AuthenticationFailed("Token invalid/expired")
 
 
@@ -90,6 +95,13 @@ def token_secret_key(value: str) -> User | None:
     return outpost.user
 
 
+def token_expression_jwt(value: str) -> User | None:
+    """Authenticate API call made by Expressions"""
+    from authentik.lib.expression.evaluator import authenticate_token
+
+    return authenticate_token(value)
+
+
 class TokenAuthentication(BaseAuthentication):
     """Token-based authentication using HTTP Bearer authentication"""
 

authentik/core/expression/evaluator.py

@@ -36,7 +36,7 @@ class PropertyMappingEvaluator(BaseEvaluator):
             _filename = model.name
         else:
             _filename = str(model)
-        super().__init__(filename=_filename)
+        super().__init__(user=user, filename=_filename)
         req = PolicyRequest(user=User())
         req.obj = model
         if user:

authentik/lib/expression/evaluator.py

@@ -3,6 +3,8 @@
 import re
 import socket
 from collections.abc import Iterable
+from datetime import timedelta
+from functools import lru_cache
 from ipaddress import ip_address, ip_network
 from pathlib import Path
 from tempfile import gettempdir
@@ -34,7 +36,9 @@ from authentik_client.configuration import Configuration
 from cachetools import TLRUCache, cached
 from django.conf import settings
 from django.core.exceptions import FieldError
+from django.utils.timezone import now
 from guardian.shortcuts import get_anonymous_user
+from jwt import PyJWTError, decode, encode
 from rest_framework.serializers import ValidationError
 from RestrictedPython import compile_restricted, limited_builtins, safe_builtins, utility_builtins
 from sentry_sdk.hub import Hub
@@ -42,14 +46,12 @@ from sentry_sdk.tracing import Span
 from structlog.stdlib import get_logger
 
 from authentik.core.models import (
-    USER_ATTRIBUTE_CHANGE_EMAIL,
-    USER_ATTRIBUTE_CHANGE_NAME,
-    USER_ATTRIBUTE_CHANGE_USERNAME,
     User,
 )
 from authentik.events.models import Event
 from authentik.lib.config import CONFIG
-from authentik.lib.utils.http import get_http_session
+from authentik.lib.utils.errors import exception_to_string
+from authentik.lib.utils.http import authentik_user_agent, get_http_session
 from authentik.lib.utils.reflection import get_apps
 from authentik.policies.models import Policy, PolicyBinding
 from authentik.policies.process import PolicyProcess
@@ -82,6 +84,23 @@ API_CLIENTS = {
     "TenantsApi": TenantsApi,
 }
 
+JWT_AUD = "goauthentik.io/api/expression"
+
+
+@lru_cache
+def get_api_token_secret():
+    return "foo"
+
+
+def authenticate_token(raw_value: str):
+    """Authenticate API call from evaluator token"""
+    try:
+        jwt = decode(raw_value, get_api_token_secret(), ["HS256"], audience=JWT_AUD)
+        return User.objects.filter(uuid=jwt["sub"]).first()
+    except PyJWTError as exc:
+        LOGGER.debug("failed to auth", exc=exc)
+        return None
+
 
 class BaseEvaluator:
     """Validate and evaluate python-based expressions"""
@@ -94,8 +113,14 @@ class BaseEvaluator:
     # Filename used for exec
     _filename: str
 
-    def __init__(self, filename: str | None = None):
+    _user: User
+
+    # Timeout in seconds, used for the expiration of the API key
+    timeout = 30
+
+    def __init__(self, user: User, filename: str | None = None):
         self._filename = filename if filename else "BaseEvaluator"
+        self._user = user
         # update website/docs/expressions/_objects.md
         # update website/docs/expressions/_functions.md
         self._globals = {
@@ -113,12 +138,6 @@ class BaseEvaluator:
             "requests": get_http_session(),
             "resolve_dns": BaseEvaluator.expr_resolve_dns,
             "reverse_dns": BaseEvaluator.expr_reverse_dns,
-            # Temporary addition of config until #7590 is through and this is not needed anymore
-            "CONFIG": CONFIG,
-            "USER_ATTRIBUTE_CHANGE_EMAIL": USER_ATTRIBUTE_CHANGE_EMAIL,
-            "USER_ATTRIBUTE_CHANGE_NAME": USER_ATTRIBUTE_CHANGE_NAME,
-            "USER_ATTRIBUTE_CHANGE_USERNAME": USER_ATTRIBUTE_CHANGE_USERNAME,
-            "api": self.get_api_client(),
         }
         for app in get_apps():
             # Load models from each app
@@ -127,18 +146,34 @@ class BaseEvaluator:
         self._globals.update(API_CLIENTS)
         self._context = {}
 
+    def get_token(self) -> str:
+        """Generate API token to be used by the API Client"""
+        _now = now()
+        return encode(
+            {
+                "aud": JWT_AUD,
+                "iss": f"goauthentik.io/expression/{self._filename}",
+                "sub": str(self._user.uuid),
+                "iat": int(_now.timestamp()),
+                "exp": int((_now + timedelta(seconds=self.timeout)).timestamp()),
+            },
+            get_api_token_secret(),
+        )
+
     def get_api_client(self):
-        token = ""
+        token = self.get_token()
         config = Configuration(
-            f"unix://{str(_tmp.joinpath('authentik-core.sock'))}",
+            f"unix://{str(_tmp.joinpath('authentik-core.sock'))}/api/v3",
             api_key={
                 "authentik": token,
             },
-            api_key_prefix={"authentik": "Bearer "},
+            api_key_prefix={"authentik": "Bearer"},
         )
         if settings.DEBUG:
-            config.host = "http://localhost:8000"
+            config.host = "http://localhost:8000/api/v3"
-        return ApiClient(config)
+        client = ApiClient(config)
+        client.user_agent = authentik_user_agent()
+        return client
 
     @cached(cache=TLRUCache(maxsize=32, ttu=lambda key, value, now: now + 180))
     @staticmethod
@@ -296,6 +331,9 @@ class BaseEvaluator:
                         **utility_builtins,
                     }
                 _locals = self._context
+                # We need to create the API Client later so that the token is valid
+                # from when the execution starts
+                self._globals["api"] = self.get_api_client()
                 # Yes this is an exec, yes it is potentially bad. Since we limit what variables are
                 # available here, and these policies can only be edited by admins, this is a risk
                 # we're willing to take.
@@ -303,6 +341,7 @@ class BaseEvaluator:
                 exec(ast_obj, self._globals, _locals)  # nosec # noqa
                 result = _locals["result"]
             except Exception as exc:
+                print(exception_to_string(exc))
                 # So, this is a bit questionable. Essentially, we are edit the stacktrace
                 # so the user only sees information relevant to them
                 # and none of our surrounding error handling

authentik/policies/expression/api.py

@@ -14,12 +14,12 @@ class ExpressionPolicySerializer(PolicySerializer):
     def validate_expression(self, expr: str) -> str:
         """validate the syntax of the expression"""
         name = "temp-policy" if not self.instance else self.instance.name
-        PolicyEvaluator(name).validate(expr)
+        PolicyEvaluator(self.context["request"].user, name).validate(expr)
         return expr
 
     class Meta:
         model = ExpressionPolicy
-        fields = PolicySerializer.Meta.fields + ["expression"]
+        fields = PolicySerializer.Meta.fields + ["expression", "execution_user"]
 
 
 class ExpressionPolicyViewSet(UsedByMixin, ModelViewSet):

authentik/policies/expression/apps.py

@@ -1,11 +1,12 @@
 """Authentik policy_expression app config"""
 
-from django.apps import AppConfig
+from authentik.blueprints.apps import ManagedAppConfig
 
 
-class AuthentikPolicyExpressionConfig(AppConfig):
+class AuthentikPolicyExpressionConfig(ManagedAppConfig):
     """Authentik policy_expression app config"""
 
     name = "authentik.policies.expression"
     label = "authentik_policies_expression"
     verbose_name = "authentik Policies.Expression"
+    default = True

authentik/policies/expression/evaluator.py

@@ -6,6 +6,7 @@ from typing import TYPE_CHECKING, Optional
 from django.http import HttpRequest
 from structlog.stdlib import get_logger
 
+from authentik.core.models import User
 from authentik.flows.planner import PLAN_CONTEXT_SSO
 from authentik.lib.expression.evaluator import BaseEvaluator
 from authentik.policies.exceptions import PolicyException
@@ -24,8 +25,8 @@ class PolicyEvaluator(BaseEvaluator):
 
     policy: Optional["ExpressionPolicy"] = None
 
-    def __init__(self, policy_name: str | None = None):
+    def __init__(self, user: User, policy_name: str | None = None):
-        super().__init__(policy_name or "PolicyEvaluator")
+        super().__init__(user, policy_name or "PolicyEvaluator")
         self._messages = []
         # update website/docs/expressions/_objects.md
         # update website/docs/expressions/_functions.md
@@ -44,6 +45,8 @@ class PolicyEvaluator(BaseEvaluator):
         if request.http_request:
             self.set_http_request(request.http_request)
         self._context["request"] = request
+        if not self._user:
+            self._user = request.user
         self._context["context"] = request.context
 
     def set_http_request(self, request: HttpRequest):

authentik/policies/expression/migrations/0005_expressionpolicy_execution_user.py

@@ -0,0 +1,26 @@
+# Generated by Django 5.0.3 on 2024-03-20 12:14
+
+import django.db.models.deletion
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("authentik_policies_expression", "0004_expressionpolicy_authentik_p_policy__fb6feb_idx"),
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="expressionpolicy",
+            name="execution_user",
+            field=models.ForeignKey(
+                default=None,
+                null=True,
+                on_delete=django.db.models.deletion.SET_DEFAULT,
+                to=settings.AUTH_USER_MODEL,
+            ),
+        ),
+    ]

authentik/policies/expression/models.py

@@ -12,6 +12,9 @@ from authentik.policies.types import PolicyRequest, PolicyResult
 class ExpressionPolicy(Policy):
     """Execute arbitrary Python code to implement custom checks and validation."""
 
+    execution_user = models.ForeignKey(
+        "authentik_core.User", default=None, null=True, on_delete=models.SET_DEFAULT
+    )
     expression = models.TextField()
 
     @property
@@ -26,17 +29,11 @@ class ExpressionPolicy(Policy):
 
     def passes(self, request: PolicyRequest) -> PolicyResult:
         """Evaluate and render expression. Returns PolicyResult(false) on error."""
-        evaluator = PolicyEvaluator(self.name)
+        evaluator = PolicyEvaluator(self.execution_user, self.name)
         evaluator.policy = self
         evaluator.set_policy_request(request)
         return evaluator.evaluate(self.expression)
 
-    def save(self, *args, **kwargs):
-        evaluator = PolicyEvaluator(self.name)
-        evaluator.policy = self
-        evaluator.validate(self.expression)
-        return super().save(*args, **kwargs)
-
     class Meta(Policy.PolicyMeta):
         verbose_name = _("Expression Policy")
         verbose_name_plural = _("Expression Policies")

authentik/policies/expression/signals.py

@@ -0,0 +1,13 @@
+from django.db.models.signals import pre_save
+from django.dispatch import receiver
+
+from authentik.policies.expression.evaluator import PolicyEvaluator
+from authentik.policies.expression.models import ExpressionPolicy
+
+
+@receiver(pre_save, sender=ExpressionPolicy)
+def pre_save_expression_policy(sender: type[ExpressionPolicy], instance: ExpressionPolicy, **_):
+    """Ensure policy is valid before saving"""
+    evaluator = PolicyEvaluator(instance.execution_user, instance.name)
+    evaluator.policy = instance
+    evaluator.validate(instance.expression)

blueprints/schema.json

@@ -3477,6 +3477,10 @@
                     "type": "string",
                     "minLength": 1,
                     "title": "Expression"
+                },
+                "execution_user": {
+                    "type": "integer",
+                    "title": "Execution user"
                 }
             },
             "required": []

schema.yml

@@ -11852,6 +11852,10 @@ paths:
         name: execution_logging
         schema:
           type: boolean
+      - in: query
+        name: execution_user
+        schema:
+          type: integer
       - in: query
         name: expression
         schema:
@@ -33565,6 +33569,9 @@ components:
           readOnly: true
         expression:
           type: string
+        execution_user:
+          type: integer
+          nullable: true
       required:
       - bound_to
       - component
@@ -33588,6 +33595,9 @@ components:
         expression:
           type: string
           minLength: 1
+        execution_user:
+          type: integer
+          nullable: true
       required:
       - expression
       - name
@@ -38841,6 +38851,9 @@ components:
         expression:
           type: string
           minLength: 1
+        execution_user:
+          type: integer
+          nullable: true
     PatchedFlowRequest:
       type: object
       description: Flow Serializer

web/src/admin/policies/expression/ExpressionPolicyForm.ts

@@ -12,7 +12,13 @@ import { TemplateResult, html } from "lit";
 import { customElement } from "lit/decorators.js";
 import { ifDefined } from "lit/directives/if-defined.js";
 
-import { ExpressionPolicy, PoliciesApi } from "@goauthentik/api";
+import {
+    CoreApi,
+    CoreUsersListRequest,
+    ExpressionPolicy,
+    PoliciesApi,
+    User,
+} from "@goauthentik/api";
 
 @customElement("ak-policy-expression-form")
 export class ExpressionPolicyForm extends BasePolicyForm<ExpressionPolicy> {
@@ -92,6 +98,39 @@ export class ExpressionPolicyForm extends BasePolicyForm<ExpressionPolicy> {
                             </a>
                         </p>
                     </ak-form-element-horizontal>
+                    <ak-form-element-horizontal label=${msg("Execution user")} name="executionUser">
+                        <ak-search-select
+                            .fetchObjects=${async (query?: string): Promise<User[]> => {
+                                const args: CoreUsersListRequest = {
+                                    ordering: "username",
+                                };
+                                if (query !== undefined) {
+                                    args.search = query;
+                                }
+                                const users = await new CoreApi(DEFAULT_CONFIG).coreUsersList(args);
+                                return users.results;
+                            }}
+                            .renderElement=${(user: User): string => {
+                                return user.username;
+                            }}
+                            .renderDescription=${(user: User): TemplateResult => {
+                                return html`${user.name}`;
+                            }}
+                            .value=${(user: User | undefined): number | undefined => {
+                                return user?.pk;
+                            }}
+                            .selected=${(user: User): boolean => {
+                                return this.instance?.executionUser === user.pk;
+                            }}
+                            blankable
+                        >
+                        </ak-search-select>
+                        <p class="pf-c-form__helper-text">
+                            ${msg(
+                                "Configure which user the bundled API client authenticates as. When left empty, the API client will inherit the permissions of the user triggering the policy execution.",
+                            )}
+                        </p>
+                    </ak-form-element-horizontal>
                 </div>
             </ak-form-group>`;
     }

web/src/common/global.ts

@@ -44,7 +44,7 @@ export function docLink(path: string): string {
     const ak = globalAK();
     // Default case or beta build which should always point to latest
     if (!ak || ak.build !== "") {
-        return `https://goauthentik.io${path}`;
+        return `https://docs.goauthentik.io${path}`;
     }
     return `https://${ak.versionSubdomain}.goauthentik.io${path}`;
 }