AWS APIGatewayv2 Authorizers

Table of Contents

Introduction
HTTP APIs
WebSocket APIs
- Lambda Authorizer
- IAM Authorizers
Import Issues
- DotNet Namespace
- Java Package

Introduction

API Gateway supports multiple mechanisms for controlling and managing access to your HTTP API. They are mainly classified into Lambda Authorizers, JWT authorizers, and standard AWS IAM roles and policies. More information is available at Controlling and managing access to an HTTP API.

HTTP APIs

Access control for HTTP APIs is managed by restricting which routes can be invoked via.

Authorizers and scopes can either be applied to the API, or specifically for each route.

Default Authorization

When using default authorization, all routes of the API will inherit the configuration.

In the example below, all routes will require the manage:books scope present in order to invoke the integration.

from aws_cdk.aws_apigatewayv2_authorizers import HttpJwtAuthorizer


issuer = "https://test.us.auth0.com"
authorizer = HttpJwtAuthorizer("DefaultAuthorizer", issuer,
    jwt_audience=["3131231"]
)

api = apigwv2.HttpApi(self, "HttpApi",
    default_authorizer=authorizer,
    default_authorization_scopes=["manage:books"]
)

Route Authorization

Authorization can also be configured for each Route. When a route authorization is configured, it takes precedence over default authorization.

The example below showcases default authorization, along with route authorization. It also shows how to remove authorization entirely for a route.

GET /books and GET /books/{id} use the default authorizer settings on the api
POST /books will require the ['write:books'] scope
POST /login removes the default authorizer (unauthenticated route)

from aws_cdk.aws_apigatewayv2_authorizers import HttpJwtAuthorizer
from aws_cdk.aws_apigatewayv2_integrations import HttpUrlIntegration


issuer = "https://test.us.auth0.com"
authorizer = HttpJwtAuthorizer("DefaultAuthorizer", issuer,
    jwt_audience=["3131231"]
)

api = apigwv2.HttpApi(self, "HttpApi",
    default_authorizer=authorizer,
    default_authorization_scopes=["read:books"]
)

api.add_routes(
    integration=HttpUrlIntegration("BooksIntegration", "https://get-books-proxy.example.com"),
    path="/books",
    methods=[apigwv2.HttpMethod.GET]
)

api.add_routes(
    integration=HttpUrlIntegration("BooksIdIntegration", "https://get-books-proxy.example.com"),
    path="/books/{id}",
    methods=[apigwv2.HttpMethod.GET]
)

api.add_routes(
    integration=HttpUrlIntegration("BooksIntegration", "https://get-books-proxy.example.com"),
    path="/books",
    methods=[apigwv2.HttpMethod.POST],
    authorization_scopes=["write:books"]
)

api.add_routes(
    integration=HttpUrlIntegration("LoginIntegration", "https://get-books-proxy.example.com"),
    path="/login",
    methods=[apigwv2.HttpMethod.POST],
    authorizer=apigwv2.HttpNoneAuthorizer()
)

JWT Authorizers

JWT authorizers allow the use of JSON Web Tokens (JWTs) as part of OpenID Connect and OAuth 2.0 frameworks to allow and restrict clients from accessing HTTP APIs.

When configured, API Gateway validates the JWT submitted by the client, and allows or denies access based on its content.

The location of the token is defined by the identitySource which defaults to the HTTP Authorization header. However it also supports a number of other options. It then decodes the JWT and validates the signature and claims, against the options defined in the authorizer and route (scopes). For more information check the JWT Authorizer documentation.

Clients that fail authorization are presented with either 2 responses:

401 - Unauthorized - When the JWT validation fails
403 - Forbidden - When the JWT validation is successful but the required scopes are not met

from aws_cdk.aws_apigatewayv2_authorizers import HttpJwtAuthorizer
from aws_cdk.aws_apigatewayv2_integrations import HttpUrlIntegration


issuer = "https://test.us.auth0.com"
authorizer = HttpJwtAuthorizer("BooksAuthorizer", issuer,
    jwt_audience=["3131231"]
)

api = apigwv2.HttpApi(self, "HttpApi")

api.add_routes(
    integration=HttpUrlIntegration("BooksIntegration", "https://get-books-proxy.example.com"),
    path="/books",
    authorizer=authorizer
)

User Pool Authorizer

User Pool Authorizer is a type of JWT Authorizer that uses a Cognito user pool and app client to control who can access your API. After a successful authorization from the app client, the generated access token will be used as the JWT.

Clients accessing an API that uses a user pool authorizer must first sign in to a user pool and obtain an identity or access token. They must then use this token in the specified identitySource for the API call. More information is available at using Amazon Cognito user pools as authorizer.

import aws_cdk.aws_cognito as cognito
from aws_cdk.aws_apigatewayv2_authorizers import HttpUserPoolAuthorizer
from aws_cdk.aws_apigatewayv2_integrations import HttpUrlIntegration


user_pool = cognito.UserPool(self, "UserPool")

authorizer = HttpUserPoolAuthorizer("BooksAuthorizer", user_pool)

api = apigwv2.HttpApi(self, "HttpApi")

api.add_routes(
    integration=HttpUrlIntegration("BooksIntegration", "https://get-books-proxy.example.com"),
    path="/books",
    authorizer=authorizer
)

Lambda Authorizers

Lambda authorizers use a Lambda function to control access to your HTTP API. When a client calls your API, API Gateway invokes your Lambda function and uses the response to determine whether the client can access your API.

Lambda authorizers depending on their response, fall into either two types - Simple or IAM. You can learn about differences here.

from aws_cdk.aws_apigatewayv2_authorizers import HttpLambdaAuthorizer, HttpLambdaResponseType
from aws_cdk.aws_apigatewayv2_integrations import HttpUrlIntegration

# This function handles your auth logic
# auth_handler: lambda.Function


authorizer = HttpLambdaAuthorizer("BooksAuthorizer", auth_handler,
    response_types=[HttpLambdaResponseType.SIMPLE]
)

api = apigwv2.HttpApi(self, "HttpApi")

api.add_routes(
    integration=HttpUrlIntegration("BooksIntegration", "https://get-books-proxy.example.com"),
    path="/books",
    authorizer=authorizer
)

IAM Authorizers

API Gateway supports IAM via the included HttpIamAuthorizer and grant syntax:

from aws_cdk.aws_apigatewayv2_authorizers import HttpIamAuthorizer
from aws_cdk.aws_apigatewayv2_integrations import HttpUrlIntegration

# principal: iam.AnyPrincipal


authorizer = HttpIamAuthorizer()

http_api = apigwv2.HttpApi(self, "HttpApi",
    default_authorizer=authorizer
)

routes = http_api.add_routes(
    integration=HttpUrlIntegration("BooksIntegration", "https://get-books-proxy.example.com"),
    path="/books/{book}"
)

routes[0].grant_invoke(principal)

WebSocket APIs

You can set an authorizer to your WebSocket API’s $connect route to control access to your API.

Lambda Authorizer

Lambda authorizers use a Lambda function to control access to your WebSocket API. When a client connects to your API, API Gateway invokes your Lambda function and uses the response to determine whether the client can access your API.

from aws_cdk.aws_apigatewayv2_authorizers import WebSocketLambdaAuthorizer
from aws_cdk.aws_apigatewayv2_integrations import WebSocketLambdaIntegration

# This function handles your auth logic
# auth_handler: lambda.Function

# This function handles your WebSocket requests
# handler: lambda.Function


authorizer = WebSocketLambdaAuthorizer("Authorizer", auth_handler)

integration = WebSocketLambdaIntegration("Integration", handler)

apigwv2.WebSocketApi(self, "WebSocketApi",
    connect_route_options=apigwv2.WebSocketRouteOptions(
        integration=integration,
        authorizer=authorizer
    )
)

IAM Authorizer

IAM authorizers can be used to allow identity-based access to your WebSocket API.

from aws_cdk.aws_apigatewayv2_authorizers import WebSocketIamAuthorizer
from aws_cdk.aws_apigatewayv2_integrations import WebSocketLambdaIntegration

# This function handles your connect route
# connect_handler: lambda.Function


web_socket_api = apigwv2.WebSocketApi(self, "WebSocketApi")

web_socket_api.add_route("$connect",
    integration=WebSocketLambdaIntegration("Integration", connect_handler),
    authorizer=WebSocketIamAuthorizer()
)

# Create an IAM user (identity)
user = iam.User(self, "User")

web_socket_arn = Stack.of(self).format_arn(
    service="execute-api",
    resource=web_socket_api.api_id
)

# Grant access to the IAM user
user.attach_inline_policy(iam.Policy(self, "AllowInvoke",
    statements=[
        iam.PolicyStatement(
            actions=["execute-api:Invoke"],
            effect=iam.Effect.ALLOW,
            resources=[web_socket_arn]
        )
    ]
))

Import Issues

jsiirc.json file is missing during the stablization process of this module, which caused import issues for DotNet and Java users who attempt to use this module. Unfortunately, to guarantee backward compatibility, we cannot simply correct the namespace for DotNet or package for Java. The following outlines the workaround.

DotNet Namespace

Instead of the conventional namespace Amazon.CDK.AWS.Apigatewayv2.Authorizers, you would need to use the following namespace:

using Amazon.CDK.AwsApigatewayv2Authorizers;;

Java Package

Instead of conventional package import software.amazon.awscdk.services.apigatewayv2_authorizers.*, you would need to use the following package:

import software.amazon.awscdk.aws_apigatewayv2_authorizers.*;

// If you want to import a specific construct
import software.amazon.awscdk.aws_apigatewayv2_authorizers.WebSocketIamAuthorizer;

Export HTTP Authorizer Id

You can retrieve the authorizer’s id once it has been bound to a route to export the value.

HttpAuthorizer.fromHttpAuthorizerAttributes

from aws_cdk.aws_apigatewayv2_authorizers import HttpLambdaAuthorizer, HttpLambdaResponseType
from aws_cdk.aws_apigatewayv2_integrations import HttpUrlIntegration
from aws_cdk import CfnOutput

# This function handles your auth logic
# auth_handler: lambda.Function


authorizer = HttpLambdaAuthorizer("BooksAuthorizer", auth_handler,
    response_types=[HttpLambdaResponseType.SIMPLE]
)

api = apigwv2.HttpApi(self, "HttpApi")

api.add_routes(
    integration=HttpUrlIntegration("BooksIntegration", "https://get-books-proxy.example.com"),
    path="/books",
    authorizer=authorizer
)

# You can only access authorizerId after it's been bound to a route
# In this example we expect use CfnOutput
CfnOutput(self, "authorizerId", value=authorizer.authorizer_id)
CfnOutput(self, "authorizerType", value=authorizer.authorization_type)

Import an existing HTTP Authorizer

If you want to import av existing HTTP Authorizer you simply provide the authorizer id and authorizer type used when the authorizer was created.

from aws_cdk.aws_apigatewayv2 import HttpAuthorizer
from aws_cdk import Fn


authorizer_id = Fn.import_value("authorizerId")
authorizer_type = Fn.import_value("authorizerType")

authorizer = HttpAuthorizer.from_http_authorizer_attributes(self, "HttpAuthorizer",
    authorizer_id=authorizer_id,
    authorizer_type=authorizer_type
)