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amazon-web-servicesaws-lambdaaws-api-gatewayamazon-cloudfront

AWS GET request with body rejected by CloudFront

I'm build an API using AWS SAM (Lambda & API Gateway) whose contract is defined by a 3rd party.

The 3rd party calls my API with a GET request that contains JSON in the body. However, when a request is sent to the API with a body it gets rejected by CloudFront.

This is the request:

curl -X GET -H "Content-Type: application/json" --data '{"hello":"world"}' https://my-api.execute-api.us-east-2.amazonaws.com/Prod/my-api

This is the response:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<HTML>
    <HEAD>
        <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
        <TITLE>ERROR: The request could not be satisfied</TITLE>
    </HEAD>
    <BODY>
        <H1>403 ERROR</H1>
        <H2>The request could not be satisfied.</H2>
        <HR noshade size="1px">
Bad request.


        <BR clear="all">
        <HR noshade size="1px">
        <PRE>
Generated by cloudfront (CloudFront)
Request ID: 1p0St_-e3noQL-2uMxeB_2I6lkMr1mg5afvxJRmVpCdnG67Vgnhj9w==
</PRE>
        <ADDRESS></ADDRESS>
    </BODY>
</HTML>

Checking the logs, the request never hits API Gateway or the Lambda function. However, if I remove the body from the request, then it hits the Lambda function and I get the appropriate error message from the API (telling the caller that the expected body is missing.)

curl -X GET -H "Content-Type: application/json" https://my-api.execute-api.us-east-2.amazonaws.com/Prod/my-api

I'm using basic configuration of API Gateway via a SAM template. This is the relevant section:

MyApiFunction:
  Type: AWS::Serverless::Function
  Properties:
    CodeUri: bin/main.zip
    Handler: main
    Runtime: go1.x
    Tracing: Active
    Role: !Sub ${MyApiLambdaExecutorRole.Arn}
    Events:
      CatchAll:
        Type: Api
        Properties:
          Path: /my-api
          Method: GET
Solution

  • GET requests cannot contain a request body on CloudFront. Try using POST instead.

    If you want to send limited data in a GET request, you can use query parameters.

    You can see in the AWS Docs that this isn't possible here:

    https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/RequestAndResponseBehaviorCustomOrigin.html#RequestCustom-get-body

    If a viewer GET request includes a body, CloudFront returns an HTTP status code 403 (Forbidden) to the viewer.

    You could perhaps use an EC2 instance or other service that doesn't use API Gateway to handle the request.