AWS Cognito JWT authentication library for FastAPI
Project description
FastAPI - Cognito
FastAPI library that ease usage of AWS Cognito Auth. This library provides basic functionalities for decoding, validation and parsing Cognito JWT tokens and for now it does not support sign up and sign in features.
Requirements
- Python >=3.8
- FastAPI
- AWS Cognito Service
How to install
Pip Command
pip install fastapi-cognito
How to use
This is the simple example of how to use this package:
- Create app
from fastapi import FastAPI
app = FastAPI()
All mandatory fields are added in CognitoSettings
BaseSettings object. Settings can be added in different ways.
You can provide all required settings in .yaml or .json files,
or your global BaseSettings object. Note that userpools
field is Dict and
FIRST user pool in a dict will be set as default automatically if
userpool_name
is not provided in CognitoAuth object.
All fields shown in example below, are also required in .json or .yaml file
(with syntax matching those files.)
- Provide settings that are mandatory for CognitoAuth to work. You can provide
one or more userpools.
app_client_id
field for userpool besides string, can contain multiple string values provided within list, tuple or set
from pydantic_settings import BaseSettings
from pydantic.types import Any
class Settings(BaseSettings):
check_expiration: bool = True
jwt_header_prefix: str = "Bearer"
jwt_header_name: str = "Authorization"
userpools: dict[str, dict[str, Any]] = {
"eu": {
"region": "USERPOOL_REGION",
"userpool_id": "USERPOOL_ID",
"app_client_id": ["APP_CLIENT_ID_1", "APP_CLIENT_ID_2"] # Example with multiple ids
},
"us": {
"region": "USERPOOL_REGION",
"userpool_id": "USERPOOL_ID",
"app_client_id": "APP_CLIENT_ID"
},
...
}
settings = Settings()
This example below shows how global BaseSettings object can be mapped to CognitoSettings and passed as param to CognitoAuth. If we were using .yaml or .json, we should call .from_yaml(path) or .from_json(path) methods on CognitoSettings object.
- Instantiate CognitoAuth and pass previously created settings as settings param.
from fastapi_cognito import CognitoAuth, CognitoSettings
# default userpool(eu) will be used if there is no userpool_name param provided.
cognito_eu = CognitoAuth(
settings=CognitoSettings.from_global_settings(settings)
)
cognito_us = CognitoAuth(
settings=CognitoSettings.from_global_settings(settings), userpool_name="us"
)
- This is a simple endpoint that requires authentication, it uses FastAPI dependency injection to resolve all required operations and get Cognito JWT.
from fastapi_cognito import CognitoToken
from fastapi import Depends
@app.get("/")
def hello_world(auth: CognitoToken = Depends(cognito_eu.auth_required)):
return {"message": "Hello world"}
Optional authentication
If authentication should be optional, we can use cognito_eu.auth_optional
Example:
from fastapi_cognito import CognitoToken
from fastapi import Depends
@app.get("/")
def hello_world(auth: CognitoToken = Depends(cognito_eu.auth_optional)):
return {"message": "Hello world"}
Custom Token Model
This feature adds possiblity to use any token type for authentication(e.g. parsing ID token).
In case your token payload contains additional values, you can provide custom
token model instead of CognitoToken
. If there is no custom token model
provided, CognitoToken
will be set as a default model. Custom model should
be provided to CognitoAuth
object, and should be set as type of auth
variable for endpoint dependency.
Example:
class CustomTokenModel(CognitoToken):
custom_value: Optional[str] = None
cognito = CognitoAuth(
settings=CognitoSettings.from_global_settings(settings),
# Here we provide custom token model
custom_model=CustomTokenModel
)
@app.get("/")
# Type of `auth` should be custom token Class
def hello_world(auth: CustomTokenModel = Depends(cognito.auth_required)):
return {"message": f"Hello {auth.custom_value}"}
Custom Cognito attributes
Custom attributes in Cognito starts with custom:
, which is the issue for
parsing this variable with pydantic because of the colon. To parse custom
attributes, add the full name of Cognito attribute to Pydantic Field alias.
class CustomTokenModel(CognitoToken):
custom_value: Optional[str] = Field(alias="custom:custom_attr")
Pydantic will automatically parse value by alias if specified. Make sure that you have default value set if attribute is optional.
OpenAPI docs authentication
To use tokens to authenticate requests using OpenAPI docs, you can create wrapper class.
from fastapi.security import HTTPBearer
from starlette.requests import Request
from fastapi_cognito import CognitoToken
class CognitoAuth(HTTPBearer):
async def __call__(self, request: Request) -> CognitoToken:
return await cognito.auth_required(request=request)
cognito_auth = CognitoAuth()
@router.get("/")
async def test_endpoint(auth: CognitoToken = Depends(cognito_auth)):
return JSONResponse(
status_code=200, content={"detail": "Success"}
)
This will show button for adding authentication token to the request.
Using custom JWKS URL for userpool
If you need to use custom JWKS URL for userpool, for example when you're running cognito-local for local development, you can specify JWKS_URL configuration per userpool.
class Settings(BaseSettings):
userpools: dict[str, dict[str, Any]] = {
"eu": {
"region": "USERPOOL_REGION",
"userpool_id": "USERPOOL_ID",
"app_client_id": "APP_CLIENT_ID",
"jwks_url": "https://local-cognito-idp:port/jwks.json"
}
...
}
By setting this configuration, CognitoAuth will automatically use this url to
retrieve JWKS for userpool. If configuration is not set, CognitoAuth will
generate URL in the following format
https://cognito-idp.<region>.amazonaws.com/<userpool_id>/.well-known/jwks.json
and will use that URL to retrieve JWKS.
There is global configuration through environment variable
AWS_COGNITO_KEYS_URL
which is supported for backward
compatibility with previous dependency on cognitojwt
library.
CognitoAuth will prioritise in the following order:
jwks_url
configuration per userpool,AWS_COGNITO_KEYS_URL
environment variable if set,- default value of
https://cognito-idp.<region>.amazonaws.com/<userpool_id>/.well-known/jwks.json
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