iOS Amazon S3 Image Upload from Scratch - ios

Question

Over the past week I have been trying to get this to work. What I am trying to do is upload an image to an S3 service as part of the pretty hacky way that this API that I am working with uses to upload images. The API is documented here: http://www.thingiverse.com/developers/upload-guide . I am having problems with step 2. They want you do upload to S3, then tell their other servers that the file is uploaded to S3, rather than doing it for you. Regardless, this is the code that I am using to upload the image:
+ (NSString *)uploadPictureWithParameters:(NSDictionary *)parameters toURL:(NSString *)actionURL withImage:(UIImage *)sourceImage {
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
[request setCachePolicy:NSURLRequestReloadIgnoringLocalCacheData];
[request setHTTPShouldHandleCookies:NO];
[request setTimeoutInterval:30];
[request setHTTPMethod:#"POST"];
NSString *boundaryConstant = #"-------------------------acebdf13572468";
NSString *contentType = [NSString stringWithFormat:#"multipart/form-data; boundary=%#", boundaryConstant];
[request setValue:contentType forHTTPHeaderField: #"Content-Type"];
NSMutableData *body = [NSMutableData data];
NSLog(#"%#", [parameters allKeys]);
if ([parameters objectForKey:#"AWSAccessKeyId"]) {
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"AWSAccessKeyId\"\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"%#\r\n", [parameters objectForKey:#"AWSAccessKeyId"]] dataUsingEncoding:NSUTF8StringEncoding]];
}
if ([parameters objectForKey:#"bucket"]) {
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"bucket\"\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"%#\r\n", [parameters objectForKey:#"bucket"]] dataUsingEncoding:NSUTF8StringEncoding]];
}
if ([parameters objectForKey:#"key"]) {
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"key\"\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"%#\r\n", [parameters objectForKey:#"key"]] dataUsingEncoding:NSUTF8StringEncoding]];
}
if ([parameters objectForKey:#"acl"]) {
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"acl\"\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"%#\r\n", [parameters objectForKey:#"acl"]] dataUsingEncoding:NSUTF8StringEncoding]];
}
if ([parameters objectForKey:#"success_action_redirect"]) {
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"success_action_redirect\"\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"%#\r\n", [parameters objectForKey:#"success_action_redirect"]] dataUsingEncoding:NSUTF8StringEncoding]];
}
if ([parameters objectForKey:#"policy"]) {
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"policy\"\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"%#\r\n", [parameters objectForKey:#"policy"]] dataUsingEncoding:NSUTF8StringEncoding]];
}
if ([parameters objectForKey:#"signature"]) {
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"signature\"\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"%#\r\n", [parameters objectForKey:#"signature"]] dataUsingEncoding:NSUTF8StringEncoding]];
}
if ([parameters objectForKey:#"Content-Type"]) {
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"Content-Type\"\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"%#\r\n", [parameters objectForKey:#"Content-Type"]] dataUsingEncoding:NSUTF8StringEncoding]];
}
if ([parameters objectForKey:#"Content-Disposition"]) {
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"Content-Disposition\"\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-disposition: attachment; filename=photo.png\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
}
// This would put them in the wrong order:
/*for (NSString *param in [parameters allKeys]) {
[body appendData:[[NSString stringWithFormat:#"---------------------------%#\r\n", boundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"%#\"\r\n\r\n", param] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"%#\r\n", [parameters objectForKey:param]] dataUsingEncoding:NSUTF8StringEncoding]];
}*/
NSLog(#"%d", body.length);
UIImage *resizedImage = [sourceImage resizedImageToFitInSize:CGSizeMake(700, 700) scaleIfSmaller:NO];
NSData *imageData = UIImagePNGRepresentation(resizedImage);
if (imageData) {
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"%#\"; filename=\"photo.png\"\r\n", #"file"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Type: image/png\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
NSString *requestBody = [[NSString alloc] initWithData:body encoding:NSUTF8StringEncoding];
NSLog(#"Request Body: %#", requestBody);
[body appendData:imageData];
[body appendData:[[NSString stringWithFormat:#"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
}
[body appendData:[[NSString stringWithFormat:#"--%#--\r\n", boundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
NSLog(#"%d", body.length);
NSString *requestBody = [[NSString alloc] initWithData:body encoding:NSUTF8StringEncoding];
NSLog(#"Request Body After Image: %#", requestBody);
[request setHTTPBody:body];
NSString *postLength = [NSString stringWithFormat:#"%d", [body length]];
[request setValue:postLength forHTTPHeaderField:#"Content-Length"];
NSString * urlString = [NSString stringWithFormat:#"%#", actionURL];
NSLog(#"%#", urlString);
NSURL *aUrl = [NSURL URLWithString: urlString];
[request setURL:aUrl];
NSError * error = nil;
NSData *returnData = [NSURLConnection sendSynchronousRequest: request returningResponse: nil error: &error];
NSLog(#"%p, %#", error, error.localizedDescription);
NSString *responseString = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];
//NSDictionary *JSONDictionary = [NSJSONSerialization JSONObjectWithData:returnData options:kNilOptions error:&error];
return responseString;
}
The error that I am getting from that is this:
Invalid according to Policy: Policy Condition failed: ["eq", "$Content-Disposition", ""]
I've been researching this online and it seems that the errors produced by S3 are typically not of much relevance to the error. So, can anyone tell me what I am doing incorrectly here?
Thanks