Error uploading file to S3 with presigned url using JQuery

Question

We are trying to upload a file to S3 using jQuery ajax & a presigned url. We generate the presigned url on the server. Currently we are trying to use FormData to upload the file.

          var uploadData = new FormData(),
            files = $(this.input).prop('files'),
            file = files[0];

          uploadData.append('file', file);

          $.ajax({
            url: '{presigned url string}',
            type: 'PUT',
            data: uploadData,
            cache: false,
            processData: false,
            contentType: false,
            success: function(response) {
              console.log('S3 upload success!');
            },
            error: function(response) {
              console.log('Error with S3 upload: ' + response.statusText);
            }
          });

This returns a SignatureDoesNotMatch error from AWS:

<Error><Code>SignatureDoesNotMatch</Code><Message>The request signature we 
calculated does not match the signature you provided. Check your key and 
signing method.</Message><StringToSignBytes>50 55 54 0a 0a 6d 75 6c 74 69 70 61 72 74 2f 66 6f 72 6d 2d 64 61 74 61 3b 20 62 6f 75 6e 64 61 72 79 3d 2d 2d 2d 2d 57 65 62 4b 69 74 46 6f 72 6d 42 6f 75 6e 64 61 72 79 67 57 6f 4a 73 42 56 79 41 4c 57 71 51 6b 73 69 0a 31 34 30 39 37 37 37 32 39 33 0a 2f 64 69 2d 6b 79 72 73 74 65 6e 2d 64 65 61 6c 73 2f 76 4e 79 4b 4e 55 4c 37 51 68 4f 30 45 4b 38 52 58 44 70 32 59 77 25 32 46 63 35 37 65 64 37 62 39 2d 64 63 61 62 2d 34 63 30 62 2d 62 36 63 30 2d 36 31 66 30 36 62 32 30 37 34 66 31 2d 74 65 73 74 2e 74 78 74</StringToSignBytes>
<RequestId>ED7C581570F547DB</RequestId><HostId>ZT6LsFYCbo1L0gYNcUwtdCWF6SNnyuUyKiL60ntJEZugx3cnDN/yH5KBjgEiBv5c</HostId><SignatureProvided>N2d7oNMVHvI6yxAXujNy8O5cF24=</SignatureProvided>
<StringToSign>PUT

multipart/form-data; boundary=----WebKitFormBoundarygWoJsBVyALWqQksi
1409777293
/test-bucket/vNyKNUL7QhO0EK8RXDp2Yw%2Fc57ed7b9-dcab-4c0b-b6c0-61f06b2074f1-test.txt</StringToSign><AWSAccessKeyId>FAKEACCESSKEY</AWSAccessKeyId></Error>  

I know that the presigned url works because I can upload the file correctly via CURL:

curl -v --upload-file {filename} {presigned url}

Answer 1

We found the issue ourselves. Here is the code we were using to generate the pre-signed url:

val dt: DateTime = new DateTime()
val expiration = DateTime.now.plusMillis(timeout.toInt)
val presignedUrlRequest: GeneratePresignedUrlRequest =
  new GeneratePresignedUrlRequest(awsBucket, key, HttpMethod.PUT)
presignedUrlRequest.setExpiration(expiration.toDate())
// WE ADDED THIS LINE
presignedUrlRequest.setContentType("multipart/form-data")

s3client.generatePresignedUrl(presignedUrlRequest).toString()

We had to set the content type in the presignedUrlRequest as well as add
headers: {'Content-Type': 'multipart/form-data'} to our ajax call.

The way we were generating the url at first worked with CURL since we weren't setting the content-type in the presignedUrlRequest and curl wasn't setting a content-type.