Uploading to Google cloud storage using Signed URL

I am able to upload to Google cloud storage directly using the below form submission ( after getting signed URL using Nodejs )

<form action="https://<%=fields.bucket%>.storage.googleapis.com" method="post" enctype="multipart/form-data">
    <input type="hidden" name="key" value="<%=fields.key%>">
    <input type="hidden" name="bucket" value="<%=fields.bucket%>">
    <input type="hidden" name="GoogleAccessId" value="<%=fields.GoogleAccessId%>">
    <input type="hidden" name="policy" value="<%=fields.policy%>">
    <input type="hidden" name="signature" value="<%=fields.signature%>">
    <input type="hidden" name="Content-Type" value="<%=fields['Content-Type']%>">

    <input name="file" type="file">
    <input type="submit" onclick="myFunction(event)" value="Upload">
</form>

But when using dropzone using the below approach I am getting 400 error . I got my Signed URL successfully and no issues with it . The issue is with axios post method .

 uploadOptions: {
    url: "/",
    uploadMultiple: false,
    method: "PUT",
    parallelUploads: 1,
    headers: {
              "Content-Type": "multipart/form-data"
            },
    autoProcessQueue: false,
    autoDiscover: false,
    acceptedFiles: "image/*",
    maxFilesize: 5,
    maxFiles: 10,
    clickable: "#upload",
    addRemoveLinks: true,
    preventDuplicates: true,
    dictDuplicateFile: "Duplicate Files Cannot Be Uploaded",
    previewsContainer: ".dropzone-previews",
    dictDefaultMessage: "",
    thumbnailWidth: 200,
     accept: function(file, done) {
      var self = this;


      var FileSize = file.size;
      console.log(" In accept");

      k1Object.$axios
        .$get("my-board?operation=fileUpload&name=" + file.name)
        .then(function(gcmData) {
          let postData = gcmData[1];
          let actionURL =
            "https://" + postData.bucket + ".storage.googleapis.com";
          file.uploadURL = actionURL;
          k1Object.k1FormData = gcmData[1];
                    done();
          setTimeout(function() {
          self.processFile(file);
          }, 0)
        });


    }, 
     init: function() {
      var self = this;
      this.on("processing", function(file) {
        self.options.url = file.uploadURL;
        console.log("processing");
      });
      this.on("sending", function(file, xhr, formData) {
        console.log(k1Object.k1FormData.key)
        formData.append("key", k1Object.k1FormData.key);
        formData.append("bucket", k1Object.k1FormData.bucket);
        formData.append("GoogleAccessId", k1Object.k1FormData.GoogleAccessId);
        formData.append("policy", k1Object.k1FormData.policy);
        formData.append("signature", k1Object.k1FormData.signature);
        formData.append("Content-Type", k1Object.k1FormData["Content-Type"]);

         var _send = xhr.send;
        xhr.send = function() {
          _send.call(xhr, file);
        }; 
      });
    } 
  }

400 error

<?xml version='1.0' encoding='UTF-8'?><Error><Code>MissingSecurityHeader</Code><Message>Your request was missing a required header.</Message><Details>Authorization</Details></Error>

I am not sure what fields it is expecting , I did even setup CORS rules for my bucket . Thank You .

This post helped me to resolve my issue . Basically what was wrong is that my file input was the first child of the form instead of at the end. Please see the below stackoverflow link for full answer .

https://stackoverflow.com/a/17524079/274715 .

I am still not sure why moving the file to the end helped me .