AWS SAM API with Cognito User Pools authorizer - amazon-web-services

Question

How can I create an API with AWS SAM that does authorization using Cognito User Pools authorizer?
Theres AWS::ApiGateway::Authorizer. But ...
{
"Type" : "AWS::ApiGateway::Authorizer",
"Properties" : {
"AuthorizerCredentials" : String,
"AuthorizerResultTtlInSeconds" : Integer,
"AuthorizerUri" : String,
"IdentitySource" : String,
"IdentityValidationExpression" : String,
"Name" : String,
"ProviderARNs" : [ String, ... ],
"RestApiId" : String,
"Type" : String
}
}
it looks like RestApiId refers to the API which uses this authorizer? But with AWS SAM, my APIs are defined like
Resources:
Ec2Index:
Type: AWS::Serverless::Function
Properties:
Handler: ec2/index.handler
Runtime: nodejs6.10
CodeUri: ./src
FunctionName: 'ApiEc2IndexHandler'
Description: 'List EC2 resources'
Timeout: 30
Role: 'arn:aws:iam::598545985414:role/awsmanagement-lambda-management'
Events:
Ec2Index:
Type: Api
Properties:
Path: /ec2
Method: get
I dont get how do I associate them together?

Answer 1

You can now reference the implicitly created api gateway with 'ServerlessRestApi'.
So in your SAM template add this piece of regular Cloudformation and everything will work fine
ApiCognitoAuthorizer:
Type: AWS::ApiGateway::Authorizer
Properties:
IdentitySource: 'method.request.header.Authorization'
Name: ApiCognitoAuthorizer
ProviderARNs:
- 'arn:aws:cognito-idp:{region}:{userpoolIdentifier}'
RestApiId: !Ref ServerlessRestApi
Type: COGNITO_USER_POOLS

Answer 2

I'm not certain you can specify an authorizer in SAM but you can embed Swagger in SAM files which can do this. It's a new feature as of Feb. 17 [ref].
I'm definitely not an expert on Swagger or SAM but it seems like you would want something like:
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: Simple API Endpoint configured using Swagger specified inline and backed by a Lambda function
Resources:
Ec2Index:
Type: AWS::Serverless::Api
Properties:
StageName: <stage>
DefinitionBody:
swagger: 2.0
info:
title:
Ref: AWS::StackName
securityDefinitions:
cognitoUserPool:
type: apiKey,
name: "Authorization"
in: header
x-amazon-apigateway-authtype: cognito_user_pools
x-amazon-apigateway-authorizer:
type: cognito_user_pools
providerARNs:
- arn:aws:cognito-idp:${AWS::Region}:{AWS::AccountId}:userpool/<user_pool_id>
paths:
"/ec2":
get:
security:
- cognitoUserPool: []
x-amazon-apigateway-integration:
httpMethod: POST
type: aws_proxy
uri:
Fn::Sub: arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${Ec2IndexLamb.Arn}/invocations
responses: {}
swagger: '2.0'
Ec2IndexLamb:
Type: AWS::Serverless::Function
Properties:
Handler: ec2/index.handler
Runtime: nodejs6.10
CodeUri: ./src
FunctionName: 'ApiEc2IndexHandler'
Description: 'List EC2 resources'
Timeout: 30
Role: 'arn:aws:iam::598545985414:role/awsmanagement-lambda-management'
Events:
Ec2Index:
Type: Api
Properties:
Path: /ec2
Method: get
References:
https://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-integrate-with-cognito.html#apigateway-enable-cognito-user-pool
https://github.com/awslabs/serverless-application-model/blob/master/examples/2016-10-31/inline_swagger/template.yaml
Edit: Fixed Swagger 2.0 syntax for the 'security' section, it should be a list.

Answer 3

Since AWS SAM v1.8.0, you can do it using the following syntax. You can refer to this article for more information.
In short, define a Cognito Authorizer for your API using API Authorizer Object. Then, set the Auth of your lambda function to refers to this API.
MyApi:
Type: AWS::Serverless::Api
Properties:
StageName: Prod
Auth:
DefaultAuthorizer: MyCognitoAuth # OPTIONAL
Authorizers:
MyCognitoAuth:
# Can also accept an array
UserPoolArn: !GetAtt MyCognitoUserPool.Arn
Identity: # OPTIONAL
# OPTIONAL; Default: 'Authorization'
Header: MyAuthorizationHeader
# OPTIONAL
ValidationExpression: myAuthValidationExp
MyFunction:
Type: AWS::Serverless::Function
Properties:
FunctionName: MyFunction
...
Events:
Post:
Type: Api
Properties:
Path: /compute
Method: POST
RestApiId: !Ref MyApi
Auth:
Authorizer: MyCognitoAuth

Answer 4

As #simones mentioned, the following will create the Cognito User Pool authorizer (CF template).
ApiCognitoAuthorizer:
Type: AWS::ApiGateway::Authorizer
Properties:
IdentitySource: 'method.request.header.Authorization'
Name: ApiCognitoAuthorizer
ProviderARNs:
- 'arn:aws:cognito-idp:{region}:{userpoolIdentifier}'
RestApiId: !Ref ServerlessRestApi
Type: COGNITO_USER_POOLS
To attach it to a resource method, the following works (in Swagger file):
securityDefinitions:
ApiCognitoAuthorizer:
type: apiKey
name: Authorization
in: header
x-amazon-apigateway-authtype: cognito_user_pools
x-amazon-apigateway-authorizer:
type: cognito_user_pools
providerARNs:
- arn:aws:cognito-idp:{region}:{userpoolIdentifier}
Then, add to specific methods (in Swagger file):
security:
- ApiCognitoAuthorizer: []

Answer 5

You can add your Cognito User Authorizer directly to your SAM AWS::Serverless::Api.
MyApi:
Type: AWS::Serverless::Api
Properties:
StageName: Prod
Cors: "'*'"
Auth:
DefaultAuthorizer: MyCognitoAuthorizer
Authorizers:
MyCognitoAuthorizer:
UserPoolArn: 'arn:aws:cognito-.....' # YOUR COGNITO USER POOL ARN
and on your AWS::Serverless::Function you can add a function authorizer if you have not set the default one. Or you can deactivate it using Authorizer: 'NONE'.
Auth:
Authorizer: MyCognitoAuthorizer
see also documentation.