Receiving Invalid policy document or request headers error when using fineuploader for amazon s3

Receiving Invalid policy document or request headers error when using
fineuploader for amazon s3

I am trying to use FineUploader's new feature allowing direct upload to
amazon s3. Currently, I am not able to upload photos. I am getting the
error: "Invalid policy document or request headers!"
The developers asked that questions be posted here at stackoverflow.
I am following their instructions on this page:
http://blog.fineuploader.com/2013/08/16/fine-uploader-s3-upload-directly-to-amazon-s3-from-your-browser/#guide
In setting things up, I have also emulated the example file linked to
there:
https://github.com/Widen/fine-uploader-server/blob/master/php/s3/s3demo.php
I have my javascript set up thusly with very few options:
$('#fineuploader-s3').fineUploaderS3({
request: {
endpoint: "http://thenameofmybucket.s3.amazonaws.com",
accessKey: "mypublicaccesskey"
},
signature: {
endpoint: "s3demo.php"
},
iframeSupport: {
localBlankPagePath: "/success.html"
},
cors: {
expected: true
}
});
I know there are lots of places where this could have gone wrong for me. I
have never used s3 or fineuploader before, so sorry if these are dumb
questions. But here are the places where I felt most confused in setting
up. I have a feeling the problem lies in #1:
(1) In the example javascript, this is how the path to signature is set up:
// REQUIRED: Path to our local server where requests can be signed.
signature: {
endpoint: "/s3/signtureHandler"
},
I wasn't sure if that is meant to be an empty file where some json is
created or if it's supposed to point to the php script where the function
to create the json is, in my case s3demo.php, which I copied directly.
(2) In the s3demo.php file, the only lines I changed were these:
$clientPrivateKey = $_SERVER['I put my private key here'];
$expectedBucket = "http://thenameofmybucket.s3.amazonaws.com";
function handlePreflightedRequest() {
// If you are relying on CORS, you will need to adjust the allowed
domain here.
header('Access-Control-Allow-Origin: http://mywebsitename.org');
}
(3) This is what I have for my CORS file, I wasn't sure if it was right
because the examples on the instructional page don't include the tags:
<CORSRule>
<AllowedOrigin>http://mywebsitename.org</AllowedOrigin>
<AllowedMethod>POST</AllowedMethod>
<MaxAgeSeconds>3000</MaxAgeSeconds>
<AllowedHeader>*</AllowedHeader>
</CORSRule>
(4) As detailed in the instructions, I went into IAM panel and created a
group with the policy copied from the instructions exactly, but with the
actual name of my bucket:
{
"Version":"2012-10-17",
"Statement":[{
"Effect":"Allow",
"Action":"s3:PutObject",
"Resource":"arn:aws:s3:::thenameofmybucket/*"
}]
}
, then a user from which I obtained the public and private access keys
used in the javascript and php files respectively.The username is not
specifically used anywhere in the scripts.
I'm hoping there is something really obvious that I've done incorrectly
here. Thanks for your time.