Create a Cognito Authentication Backend via CloudFormation

cognito.yaml

AWSTemplateFormatVersion: '2010-09-09'
Description: Cognito Stack
Parameters:
  AuthName:
    Type: String
    Description: Unique Auth Name for Cognito Resources

Resources:
  # Creates a role that allows Cognito to send SNS messages
  SNSRole:
    Type: "AWS::IAM::Role"
    Properties:
      AssumeRolePolicyDocument: 
        Version: "2012-10-17"
        Statement:
          - Effect: "Allow"
            Principal: 
              Service: 
                - "cognito-idp.amazonaws.com"
            Action: 
              - "sts:AssumeRole"
      Policies:
        - PolicyName: "CognitoSNSPolicy"
          PolicyDocument: 
            Version: "2012-10-17"
            Statement: 
              - Effect: "Allow"
                Action: "sns:publish"
                Resource: "*"

  # Creates a user pool in cognito for your app to auth against
  # This example requires MFA and validates the phone number to use as MFA
  # Other fields can be added to the schema
  UserPool:
    Type: "AWS::Cognito::UserPool"
    Properties:
      UserPoolName: !Sub ${AuthName}-user-pool
      AutoVerifiedAttributes:
        - phone_number
      MfaConfiguration: "ON"
      SmsConfiguration:
        ExternalId: !Sub ${AuthName}-external
        SnsCallerArn: !GetAtt SNSRole.Arn
      Schema:
        - Name: name
          AttributeDataType: String
          Mutable: true
          Required: true
        - Name: email
          AttributeDataType: String
          Mutable: false
          Required: true
        - Name: phone_number
          AttributeDataType: String
          Mutable: false
          Required: true
        - Name: slackId
          AttributeDataType: String
          Mutable: true
  
  # Creates a User Pool Client to be used by the identity pool
  UserPoolClient:
    Type: "AWS::Cognito::UserPoolClient"
    Properties:
      ClientName: !Sub ${AuthName}-client
      GenerateSecret: false
      UserPoolId: !Ref UserPool
  
  # Creates a federeated Identity pool
  IdentityPool:
    Type: "AWS::Cognito::IdentityPool"
    Properties:
      IdentityPoolName: !Sub ${AuthName}Identity
      AllowUnauthenticatedIdentities: true
      CognitoIdentityProviders: 
        - ClientId: !Ref UserPoolClient
          ProviderName: !GetAtt UserPool.ProviderName

  # Create a role for unauthorized acces to AWS resources. Very limited access. Only allows users in the previously created Identity Pool
  CognitoUnAuthorizedRole:
    Type: "AWS::IAM::Role"
    Properties:
      AssumeRolePolicyDocument: 
        Version: "2012-10-17"
        Statement:
          - Effect: "Allow"
            Principal: 
              Federated: "cognito-identity.amazonaws.com"
            Action: 
              - "sts:AssumeRoleWithWebIdentity"
            Condition:
              StringEquals: 
                "cognito-identity.amazonaws.com:aud": !Ref IdentityPool
              "ForAnyValue:StringLike":
                "cognito-identity.amazonaws.com:amr": unauthenticated
      Policies:
        - PolicyName: "CognitoUnauthorizedPolicy"
          PolicyDocument: 
            Version: "2012-10-17"
            Statement: 
              - Effect: "Allow"
                Action:
                  - "mobileanalytics:PutEvents"
                  - "cognito-sync:*"
                Resource: "*"

  # Create a role for authorized acces to AWS resources. Control what your user can access. This example only allows Lambda invokation
  # Only allows users in the previously created Identity Pool
  CognitoAuthorizedRole:
    Type: "AWS::IAM::Role"
    Properties:
      AssumeRolePolicyDocument: 
        Version: "2012-10-17"
        Statement:
          - Effect: "Allow"
            Principal: 
              Federated: "cognito-identity.amazonaws.com"
            Action: 
              - "sts:AssumeRoleWithWebIdentity"
            Condition:
              StringEquals: 
                "cognito-identity.amazonaws.com:aud": !Ref IdentityPool
              "ForAnyValue:StringLike":
                "cognito-identity.amazonaws.com:amr": authenticated
      Policies:
        - PolicyName: "CognitoAuthorizedPolicy"
          PolicyDocument: 
            Version: "2012-10-17"
            Statement: 
              - Effect: "Allow"
                Action:
                  - "mobileanalytics:PutEvents"
                  - "cognito-sync:*"
                  - "cognito-identity:*"
                Resource: "*"
              - Effect: "Allow"
                Action:
                  - "lambda:InvokeFunction"
                Resource: "*"
  
  # Assigns the roles to the Identity Pool
  IdentityPoolRoleMapping:
    Type: "AWS::Cognito::IdentityPoolRoleAttachment"
    Properties:
      IdentityPoolId: !Ref IdentityPool
      Roles:
        authenticated: !GetAtt CognitoAuthorizedRole.Arn
        unauthenticated: !GetAtt CognitoUnAuthorizedRole.Arn

Outputs:
  UserPoolId:
    Value: !Ref UserPool
    Export:
      Name: "UserPool::Id"
  UserPoolClientId:
    Value: !Ref UserPoolClient
    Export:
      Name: "UserPoolClient::Id"
  IdentityPoolId:
    Value: !Ref IdentityPool
    Export:
      Name: "IdentityPool::Id"

description.md

This creates a starting point for a simple Authentication backend using AWS Cognito. With this you can create everything you need for the backend to register, login, and access AWS Lambda and other services.

To get started builing a client...

Identity: https://github.com/aws/amazon-cognito-identity-js

Serverless: https://blog.rackspace.com/part-1-building-server-less-architecture-aws