---
title: Notification Rule Expression Policies
sidebar_label: Expression Policies
---

[Notification rules](./notifications.md) with [bound expression policies](./notifications.md#3-create-a-notification-rule-and-bind-it-to-the-policy) are very powerful. The following are examples of what can be achieved.

### Trigger alert when user logs in from unknown device

This expression policy is triggered when a user logs in from an unknown device. This can be combined with a notification rule to alert administrators, or the user in question if `Send notification to event user` is enabled on the notification rule.

```python
# Check if an event has occurred
event = request.context.get("event", None)
if not event:
    ak_logger.info("no event")
    return False

# Check if the event action includes updating a model
if event.action != "login":
    ak_logger.info("event action does not match")
    return False

# Get the known device status
known_device = event.context["auth_method_args"]["known_device"]

# Alert if device is unknown
if known_device == False:
  ak_logger.info("User logged in from unknown device")
  return True
else:
  return False
```

### Change user attributes upon account deactivation

This expression policy is triggered when a user account with the `sshPublicKey` attribute set is deactivated. It saves the `sshPublicKey` attribute to a new `inactivesshPublicKey` attribute, and subsequently nullifies the `sshPublicKey` attribute.

```python
from authentik.core.models import User

# Check if an event has occurred
event = request.context.get("event", None)
if not event:
    ak_logger.info("no event")
    return False

# Check if the event action includes updating a model
if event.action != "model_updated":
    ak_logger.info("event action does not match")
    return False

model_app = event.context["model"]["app"]
model_name = event.context["model"]["model_name"]

# Check if the model that was updated is the user model
if model_app != "authentik_core" or model_name != "user":
    ak_logger.info("model does not match")

user_pk = event.context["model"]["pk"]
user = User.objects.filter(pk=user_pk).first()

# Check if an user object was found
if not user:
    ak_logger.info("user not found")
    return False

# Check if user is active
if user.is_active:
    ak_logger.info("user is active, not changing")
    return False

# Check if user has the `sshPublicKey` attribute set
if not user.attributes.get("sshPublicKey"):
    ak_logger.info("no public keys to remove")
    return False

# Save the `sshPublicKey` attribute to a new `inactiveSSHPublicKey` attribute
user.attributes["inactiveSSHPublicKey"] = user.attributes["sshPublicKey"]

# Nullify the `sshPublicKey` attribute
user.attributes["sshPublicKey"] = []

# Save the changes made to the user
user.save()

return False
```

### Alert when application is created without binding

This expression policy is triggered when a new application is created without any user, group, or policy bound to it. The notification rule can then be configured to alert an administrator. This feature is useful for ensuring limited access to applications, because by default an application without any users, groups, or policies bound to it can be accessed by all users.

```python
from authentik.core.models import Application
from authentik.policies.models import PolicyBinding

# Check if an event has occurred
event = request.context.get("event", None)
if not event:
    ak_logger.info("no event")
    return False

# Check if the event action includes creating a model
if event.action != "model_created":
    ak_logger.info("event action does not match")
    return False

model_app = event.context["model"]["app"]
model_name = event.context["model"]["model_name"]

# Check if the model that was created is the application model
if model_app != "authentik_core" or model_name != "application":
    ak_logger.info("model does not match")

application_pk = event.context["model"]["pk"]
application = Application.objects.filter(pk=application_pk).first()

# Check if an application object was found
if not application:
    ak_logger.info("application not found")
    return False

# Check if application has binding
if PolicyBinding.objects.filter(target=application).exists():
    output = PolicyBinding.objects.filter(target=application)
    ak_logger.info("application has bindings, returning true")
    return True

return False
```

### Append user addition history to group attributes

This expression policy is triggered when a user is added to a group. The policy then creates and updates a `UserAddedHistory` attribute to the group with a date/time stamp and the username of the added user. This functionality is already available within the changelog of a group, but this code can be used as a template to trigger alerts or other events.

:::info
This policy interacts with the `diff` event output. This field is only available with an enterprise license.
:::

```python
from authentik.core.models import User
from authentik.core.models import Group
from datetime import datetime

# Check if an event has occurred
event = request.context.get("event", None)
if not event:
    ak_logger.info("no event")
    return False

# Check if the event action includes updating a model
if event.action != "model_updated":
    ak_logger.info("event action does not match")
    return False

model_app = event.context["model"]["app"]
model_name = event.context["model"]["model_name"]

# Check if the model that was updated is the group model
if model_app != "authentik_core" or model_name != "group":
    ak_logger.info("model does not match")

group_pk = event.context["model"]["pk"]
group = Group.objects.filter(pk=group_pk).first()

# If user was added to group, get user object, else return false
if "add" in event.context["diff"]["users"]:
    ak_logger.info("user added to group")

    user_pk = event.context["diff"]["users"]["add"][0]
    user = User.objects.filter(pk=user_pk).first()
else:
    ak_logger.info("user not added to group")
    return False

# Check if a group object was found
if not group:
    ak_logger.info("group not found")
    return False

# Check if an user object was found
if not user:
    ak_logger.info("user not found")
    return False

if not group.attributes.get("UserAddedHistory"):
    group.attributes["UserAddedHistory"] = []

current_date_time = datetime.now().isoformat(timespec='seconds')

group.attributes["UserAddedHistory"].append(current_date_time + " - Added user: " + user.username)

# Save the changes made to the group
group.save()

return False
```
