Signature Denied in PUT upload to S3 with Pre-Signed URL

Question

Why might I be getting a SignatureDoesNotMatch error from a S3 Amazon Pre-Signed Url PUT request?

I am using the AWS Javascript SDK to generate the signed putObject url and posting with a jQuery Ajax PUT request using Dropzone.js to manage file uploads.

Uploads work with curl -v -T <IMAGE> <PRE-SIGNED-URL> .

---

Request:

// Send uploads to s3 signed urls.
// @param res [Object] of signed-url's for image files.
function sendFiles(res){
  res.forEach(function(signedUrl){
    // Get file for associated Dropzone queued file.
    var file = returnFile(signedUrl.options.id);

    // signedUrl.url returns:
    // https://bucket.s3-us-west-1.amazonaws.com/path/(key:filename)Type=image%2Fjpeg&Expires=1449874843&Signature=####&x-amz-acl=public-read-write`
    $.ajax({
      url: signedUrl.url,
      type: 'PUT',
      data: file.upload,
      contentType:'multipart/form',
      dataType: 'json',
      complete:function(data){
        console.log("Done", data);
      },
      error:function(data){
        console.log("Error", data);
      }
    });
  });
}

Response:

<Code>
   SignatureDoesNotMatch
</Code>
<Message>
   The request signature we calculated does not match the signature you provided.   
   Check your key and signing method.
</Message>

Answer 1

I found a solution. This took two modifications. I hope someone could explain them better.

---

First

I had to run decodeURIComponent() on the returned s3 signed url string from the aws-sdk.

Second

I had to change three and add two new options to the ajax PUT request.

{
  data: file,
  contentType:'image/jpeg',
  dataType:"text",
  cache : false,
  processData : false
}