Upload files to S3 via Cloudfront

Question

I'm trying to upload files to S3 via Cloudfront. I've created a bucket with name my-files. Bucket CORS settings:

<?xml version="1.0" encoding="UTF-8"?>
<CORSConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
    <CORSRule>
        <AllowedOrigin>*</AllowedOrigin>
        <AllowedMethod>GET</AllowedMethod>
        <AllowedMethod>PUT</AllowedMethod>
        <AllowedMethod>POST</AllowedMethod>
        <AllowedMethod>DELETE</AllowedMethod>
        <AllowedMethod>HEAD</AllowedMethod>
        <MaxAgeSeconds>3000</MaxAgeSeconds>
        <AllowedHeader>Authorization</AllowedHeader>
    </CORSRule>
</CORSConfiguration>

I've created Cloudfront distribution. Here is configuration which can be important:

General:

Delivery Method: Web
Alternate Domain Names (CNAMEs) files.example.com

Origins:

Origin Domain Name: my-files.s3.amazonaws.com
Restrict Bucket Access: Yes
Grant Read Permissions on Bucket: Yes, Update Bucket Policy

Behaviour:

Path Pattern: Default (*)
Origin: S3-my-files
Viewer Protocol Policy: HTTP and HTTPS
Allowed HTTP Methods: GET, HEAD, OPTIONS, PUT, POST, PATCH, DELETE
Whitelist Headers: Access-Control-Request-Headers, Access-Control-Request-Method, Origin
Object Caching: Use Origin Cache Headers
Restrict Viewer Access (Use Signed URLs or Signed Cookies): Yes
Trusted Signers: Self

I can create signed URL for file download and it works correctly. I can create CNAME for S3 bucket, upload a file to S3 using pre-signed URL and this also works correctly. When I'm trying to upload file via Cloudfront then I'm getting a 403 response (OPTIONS):

XMLHttpRequest cannot load http://files.example.com/. Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://0.0.0.0:5000' is therefore not allowed access. The response had HTTP status code 403.

Is it possible to use Cloudfront with signed URLs for uploading files? How can I set allowed origins to allow file uploads from localhost?

Answer 1

I suspect that error is relevant with the CORS options of your request.

With jQuery, this is currently my sample code that successfully uploading file to S3 via CloudFront (notice the crossDomain option). If you don't use jQuery, you can base on this to write your code:

$.ajax({
    type: 'POST',
    url: 'YourGetSignatureMethod', //return your signed url
    data: {
          fileName: yourFileName,
          expiration: yourPolicyExpirationDate
    },
    success: function (signedUrl) {
         //signedUrl= 'http://sampleId.cloudfront.net/video.mp4?Policy=examplePolicy&Signature=exampleSignature&Key-Pair-Id=exampleKey'
         let fileObject = yourGetFileFunction(); //returns File API
         let reader = new FileReader(); //using the FileReader API to read files
         reader.onload = function () {                                      
	     $.ajax({
		url: signedUrl,
		type: 'PUT',
		contentType: fileObject.type,
		data: reader.result,
		processData: false,
		crossDomain: true,
                success: function(){
                //upload success
                }
	    });
        }  
        reader.readAsArrayBuffer(fileObject);
    }
 });