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https://github.com/holinnn/deny

Python authorization library
https://github.com/holinnn/deny

api authorization falcon fastapi permissions python sanic

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Python authorization library

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README 

        
# deny



Library for managing permissions in your Python 3.7+ projects.  

For example, it can be used to grant access to some API endpoints based on policies you defined.



## Installation



```

pip install deny

```



## Usage



First define the permissions needed in your project:



```python 

from deny import AutoPermission, Permission



class ProfilePermissions:

    view = Permission(name="view_project")

    edit = AutoPermission()  # name will be automatically set to "ProjectPermissions.edit"



class SessionPermissions:

    create = AutoPermission()

    delete = AutoPermission()

```



Then create policies that will be used to grant the permissions:



```python

from deny import Policy, authorize



class LoggedInUser:

    @authorize(SessionPermissions.delete)

    async def can_logout(self):

        return True



class AnonymousUser(Policy):

    @authorize(SessionPermissions.create)

    async def can_login(self):

        return True



class UserPolicy(LoggedInUser, Policy):

    def __init__(self, current_user_id: int):

        """You should inject any dependency this policy relies on.

        Here we just save the current user ID, but you might need 

        a connection to a database, a whole user object, etc.

        """

        self._current_user_id = current_user_id



    @authorize(ProfilePermissions.edit)

    async def can_edit_profile(self, user_id: int) -> bool:

        """Only current user can edit his own profile."""

        return self._current_user_id == user_id



    @authorize(ProfilePermissions.view)

    async def can_view_profile(self, user_id: int) -> bool:

        """Everybody can view the user profiles."""

        return True

```



Finally create an Ability with the right policy and check if the permissions are granted:



```python

from deny import Ability



def get_ability(current_user_id: Optional[int]) -> Ability:

    if current_user_id:

        policy = UserPolicy(current_user_id)

    else:

        policy = AnonymousUser()



    return Ability(policy=policy)



################

# Logged in user

ability = get_ability(1)

await ability.can(ProfilePermissions.view, 1) # True

await ability.can(ProfilePermissions.view, 2) # True

await ability.can(ProfilePermissions.edit, 1) # True

await ability.authorize(ProfilePermissions.edit, 1) # does not throw any error

await ability.can(ProfilePermissions.edit, 2) # False

await ability.authorize(ProfilePermissions.edit, 2) # throw an UnauthorizedError

await ability.can(SessionPermission.create) # False

await ability.can(ProfilePermissions.delete) # True



################

# Anonymous user

ability = get_ability(None)

await ability.can(ProfilePermissions.view, 1) # False

await ability.can(ProfilePermissions.view, 2) # False

await ability.can(ProfilePermissions.edit, 1) # False

await ability.authorize(ProfilePermissions.edit, 1) # throw an UnauthorizedError

await ability.can(ProfilePermissions.edit, 2) # False

await ability.authorize(ProfilePermissions.edit, 2) # throw an UnauthorizedError

await ability.can(SessionPermission.create) # True

await ability.can(ProfilePermissions.delete) # False

```



You can see the full example in [examples/usage.py](https://github.com/holinnn/deny/tree/main/examples/usage.py) (you will need `asyncio` to run it, `pip install asyncio`)



## Web frameworks



Deny can be used with any web framework.  

But it comes with some helper functions for [Falcon](https://falcon.readthedocs.io/en/stable/), [Sanic](https://sanic.dev/en/), [FastAPI](https://fastapi.tiangolo.com/) and [Flask](https://flask.palletsprojects.com/).



Here is an example for the [Sanic](https://sanic.dev/en/) web framework:

```python 

from sanic import Sanic

from sanic.request import Request

from sanic.response import HTTPResponse, json



from deny import Ability, AutoPermission, Policy, authorize as policy_authorize

from deny.errors import UnauthorizedError

from deny.ext.sanic import authorize



class ProjectPermissions:

    view = AutoPermission()



class UserPolicy(Policy):

    @authorize(ProjectPermissions.view)

    async def can_view_project(self, request: Request, id: int) -> bool:

        return id == 1



app = Sanic("example")



@app.middleware("request")

async def inject_ability(request: Request) -> None:

    request.ctx.ability = Ability(policy=UserPolicy())



@app.get("/projects/")

@authorize(ProjectPermissions.view)

async def get(request: Request, id: int) -> HTTPResponse:

    return json({"id": id})



@app.exception(UnauthorizedError)

async def unauthorized_handler(request: Request, exc: Exception):

    return json({"error": str(exc)}, status=403)

```



You can find the examples for each of those frameworks in the [examples/](https://github.com/holinnn/deny/tree/main/examples) folder from this repository.



## Sync support



By default all the classes provided by `deny` are built to run in an asynchronous environement.  

If you run in a synchronous environement (without `async`, `await`), then import from `deny.sync` instead of `deny`.  

See [examples/sync.py](https://github.com/holinnn/deny/tree/main/examples/sync.py) for a full example.