GET succeeds with NSURLSession but fails with AFHTTPSessionManager

Question

I'm having trouble getting an image from S3 using a presigned url and AFNetworking 3.0. I can get the image using NSMutableURLRequest and an NSURLSession, but I get a 403 error when I use an AFHTTPSessionManager and the same NSMutableURLRequest. (I actually want to load the image by just calling setImageWithURLRequest, which is also giving me a 403 error, but I wrote this code that uses AFHTTPSessionManager to try to debug the issue.) What could I be doing wrong with AFNetworking?

let request = NSMutableURLRequest()
request.HTTPMethod = "GET"
request.URL = coverPhotoUrl // A presigned url to an image on S3

// The operation succeeds if I uncomment the NSURLSession line
// and comment out the AFHTTPSessionManager line.
//NSURLSession.sharedSession().dataTaskWithRequest(request) {
AFHTTPSessionManager().dataTaskWithRequest(request) {
    date, response, error in
    if let error = error {
        Log.error?.message("request failed: \(error.localizedDescription)")
    } else {
        Log.debug?.message("request succeeded.")
    }
}
.resume()

Answer 1

AFNetworking was failing the request due to content type issues. setImageWithURL worked after I changed the S3 files' content type from binary/octet to image/jpeg.

Getting S3 to set the content type was also difficult. In case it's of use to anyone else, S3 ignored the content type in my PUT requests until I specified a content length. I just used a dummy length of 1 when generating the presigned URL despite the fact that the actual files are far longer.