Redirect one domain to another via Cloudfront Lambda@Edge

cloudfront_lambda_redirect

AWSTemplateFormatVersion: 2010-09-09
Description: Cloudfront redirect lambda demo

Parameters:
  FromDomain:
    Type: String
    Default: darin.dev-code.org
    Description: The domain you wish to redirect traffic from
  ToDomain:
    Type: String
    Default: code.org
    Description: The domain you wish to redirect traffic to
  HostedZoneId:
    Type: String
    Description: The HostedZoneId for the To/From Domains
  RedirectType:
    Type: String
    Default: 302
    AllowedValues:
      - 301
      - 302
    Description: The redirect type, permanent or temporary


Resources:

  PrimaryRecord:
    Type: "AWS::Route53::RecordSet"
    Properties:
      HostedZoneId: !Ref HostedZoneId
      Name: !Ref FromDomain
      Type: A
      AliasTarget:
        HostedZoneId: Z2FDTNDATAQYW2
        DNSName: !GetAtt CFDistribution.DomainName

  CFDistribution:
    Type: AWS::CloudFront::Distribution
    Properties:
      DistributionConfig:
        Enabled: "true"
        Comment: "Redirect www to root domain"
        PriceClass: PriceClass_100
        Aliases:
          - !Ref FromDomain
        DefaultCacheBehavior:
          TargetOriginId: PrimaryOrigin
          CachePolicyId: !Ref RedirectCachePolicy
          LambdaFunctionAssociations:
            - EventType: origin-request
              LambdaFunctionARN: !Ref RedirectLambdaVersion4
          ViewerProtocolPolicy: allow-all
        ViewerCertificate:
          AcmCertificateArn: !Ref Certificate
          SslSupportMethod: sni-only
        # The lambda prevents traffic from hitting this origin, but we need it regardless
        Origins:
          - Id: PrimaryOrigin
            DomainName: !Ref FromDomain
            CustomOriginConfig:
              OriginProtocolPolicy: http-only
              HTTPPort: 80

  RedirectCachePolicy:
    Type: AWS::CloudFront::CachePolicy
    Properties:
      CachePolicyConfig:
        Name: RedirectCachePolicy
        MinTTL: 3600
        MaxTTL: 31536000
        DefaultTTL: 86400
        ParametersInCacheKeyAndForwardedToOrigin: 
          EnableAcceptEncodingGzip: false
          CookiesConfig: 
            CookieBehavior: none
          HeadersConfig: 
            HeaderBehavior: whitelist
            Headers:
              - Origin
          QueryStringsConfig: 
            QueryStringBehavior: all

  Certificate:
    Type: AWS::CertificateManager::Certificate
    Properties:
      DomainName: !Ref FromDomain
      ValidationMethod: DNS
      DomainValidationOptions:
        - DomainName: !Ref FromDomain
          HostedZoneId: !Ref HostedZoneId

  RedirectLambda:
    Type: AWS::Lambda::Function
    Properties:
      Runtime: nodejs14.x
      Role: !GetAtt RedirectLambdaRole.Arn
      Handler: index.handler
      Code:
        ZipFile: !Sub |
          'use strict';

          exports.handler = (event, context, callback) => {
            const request = event.Records[0].cf.request;
            const uri = request.uri;
            const host = request.headers.host[0].value;
            const querystring = request.querystring;

            // Start building new url
            let newUrl = '${ToDomain}';

            // Append path
            if (uri) newUrl += uri;
            
            // Append query string
            if (querystring && querystring != '') newUrl += "?" + querystring;

            const response = {
              status: '${RedirectType}',
              statusDescription: '${RedirectType} Redirect to root domain',
              headers: {
                location: [{
                  key: 'Location',
                  value: newUrl
                }]
              }
            };
            callback(null, response);
          };
      Description: Redirect www traffic to root domain
      TracingConfig:
        Mode: Active

  # To make a new version, bump the NAME of this resource and all references
  RedirectLambdaVersion4:
    Type: AWS::Lambda::Version
    Properties:
      FunctionName: !Ref RedirectLambda

  RedirectLambdaRole:
    Type: "AWS::IAM::Role"
    Properties:
      Path: "/"
      ManagedPolicyArns:
        - "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
          - Sid: "AllowLambdaServiceToAssumeRole"
            Effect: "Allow"
            Action:
              - "sts:AssumeRole"
            Principal:
              Service:
                - "lambda.amazonaws.com"
                - "edgelambda.amazonaws.com"