How do you add CloudFront in front of API Gateway

Question

API Gateway (APIG), while it uses CloudFront (CF) it does not support CDN edge caching. When I configured a CF distribution to use APIG as the custom origin, I get a permission denied error.

How do I configure CF to fix this?

Answer 1

Until API Gateway (APIG) supports edge caching via its internal use of CloudFront (CF), I have come up with a workaround.

You can indeed put CF dist in front of APIG, the trick is to force HTTPS only "Viewer Protocol Policy" AND to NOT forward the HOST header because APIG needs SNI.

I setup my CF "Default Cache Behavior Settings" to not forward any headers, and forced "Viewer Protocol Policy" to "HTTPS Only" and it works. Hope this helps others.

Here is a CloudFormation resource object that has all the required configuration (Note: I use the convention <stage>--<app name> for StackName):

CloudFront:  
  Type: AWS::CloudFront::Distribution
  Properties:
    DistributionConfig:
      Enabled: true
      IPV6Enabled: true
      HttpVersion: http2
      Comment: !Join [ '--', [!Ref 'AWS::StackName', ' Cloud Front']]
      Aliases: [!Ref CloudFrontCname]
      ViewerCertificate:
        AcmCertificateArn: !Ref AcmCertificateArn
        SslSupportMethod: sni-only
        MinimumProtocolVersion: TLSv1.1_2016
      Origins:
      - Id: APIGOrigin
        DomainName: !Sub
          - ${apigId}.execute-api.${AWS::Region}.amazonaws.com
          - { apigId: !Ref ApiGatewayLambdaProxy }
        OriginPath: !Sub
          - /${Stage}
          - { Stage: !Select [ "0", !Split [ '--', !Ref 'AWS::StackName' ] ] }
        CustomOriginConfig:
          # HTTPPort: 80
          HTTPSPort: 443
          OriginProtocolPolicy: https-only
        OriginCustomHeaders:
          - HeaderName: 'Verify-From-Cf'
            HeaderValue: !Ref VerifyFromCfHeaderVal
      DefaultCacheBehavior:
        AllowedMethods: ["DELETE", "GET", "HEAD", "OPTIONS", "PATCH", "POST", "PUT"]
        CachedMethods: ["GET", "HEAD", "OPTIONS"]
        ForwardedValues:
          Headers:
          - Access-Control-Request-Headers
          - Access-Control-Request-Method
          - Origin
          - Authorization
          # - Host APIG needs to use SNI
          QueryString: true
        TargetOriginId: APIGOrigin
        ViewerProtocolPolicy: https-only
        Compress: true
        DefaultTTL: 0
      CustomErrorResponses:
      - ErrorCachingMinTTL: 0
        ErrorCode: 400
      - ErrorCachingMinTTL: 1
        ErrorCode: 403
      - ErrorCachingMinTTL: 5
        ErrorCode: 500
DNSARecord:    
  Type: AWS::Route53::RecordSet
  Properties:
    Comment: !Ref 'AWS::StackName'
    Name: !Ref CloudFrontCname
    Type: A
    HostedZoneName: !Join ['.', [ !Select [1, !Split ['.', !Ref CloudFrontCname]], !Select [2, !Split ['.', !Ref CloudFrontCname]], '']]
    AliasTarget:
      HostedZoneId: !Ref Route53HostedZoneId
      DNSName: !GetAtt CloudFront.DomainName
DNSAAAARecord:    
  Type: AWS::Route53::RecordSet
  Properties:
    Comment: !Ref 'AWS::StackName'
    Name: !Ref CloudFrontCname
    Type: AAAA
    HostedZoneName: !Join ['.', [ !Select [1, !Split ['.', !Ref CloudFrontCname]], !Select [2, !Split ['.', !Ref CloudFrontCname]], '']]
    AliasTarget:
      HostedZoneId: !Ref Route53HostedZoneId
      DNSName: !GetAtt C

Late 2018 updates

• CloudFormation finally supports setting SSL proto ver: MinimumProtocolVersion: TLSv1.1_2016
• I've baked this (and many other) best practices into an OSS project: aws-blueprint