Python and Objective-C code that enables an iOS app to upload images directly to an S3 bucket using a secure authorization header generated by a python server Code is a Fork from Stackoverflow answer: http://stackoverflow.com/questions/4481311/architectural-and-design-question-about-uploading-photos-from-iphone-app-and-s3 Let me know what you th…

gistfile1.m

- (void)uploadImage:(UIImage *)image
{
    //Set up the upload request from our server
    NSURL *url = [NSURL URLWithString:@"http://<your-server-url-here>/"];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    
    AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
        
        // Pull out any required information out of the response
        NSString *serverDate = [JSON valueForKeyPath:@"date_string"];
        NSString *serverHmacDigest = [JSON valueForKeyPath:@"auth_string"];
        NSString *S3AccessKey = [JSON valueForKeyPath:@"s3_key"];
        NSString *S3BucketName = [JSON valueForKeyPath:@"bucket_name"];
        NSString *content_type = [JSON valueForKeyPath:@"content_type"];
        NSString *full_pathname = [JSON valueForKeyPath:@"full_pathname"];
        NSString *filename = [JSON valueForKeyPath:@"filename"];
        
        // Create the headers.
        NSMutableDictionary *headers = [[NSMutableDictionary alloc] init];
        [headers setObject:content_type forKey:@"Content-Type"];
        NSString *host = [NSString stringWithFormat:@"%@.s3.amazonaws.com", S3BucketName];
        [headers setObject:host forKey:@"Host"];
        [headers setObject:serverDate forKey:@"Date"];
        NSString *authorization = [NSString stringWithFormat:@"AWS %@:%@", S3AccessKey, serverHmacDigest];
        [headers setObject:authorization forKey:@"Authorization"];
        
        // Create the new Amazon S3 request.
        NSMutableURLRequest *postrequest = [[NSMutableURLRequest alloc] init];
        [postrequest setAllHTTPHeaderFields:headers];
        NSData *imageData = UIImageJPEGRepresentation(image, 0.7);
        [postrequest setHTTPBody:imageData];
        [postrequest setHTTPMethod:@"PUT"];
        NSString *postUrl = [NSString stringWithFormat:@"http://%@.s3.amazonaws.com/images/%@", S3BucketName, filename];
        [postrequest setURL:[NSURL URLWithString:postUrl]];
        
        // Set up the POST request to Amazon S3
        AFXMLRequestOperation *operation = [AFXMLRequestOperation XMLParserRequestOperationWithRequest:postrequest success:^(NSURLRequest *request, NSHTTPURLResponse *response, NSXMLParser *XMLParser) {
            
            //At this point, we have successfully uploaded the photo to Amazon.
            
            // TODO: Do shit after upload
            NSLog(@"Image uploaded: %@", postUrl);
            
        } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, NSXMLParser *XMLParser){
            NSLog(@"Error uploading image to Amazon S3: %@", error);
        }];
        
        NSOperationQueue *queue = [[NSOperationQueue alloc] init];
        [queue addOperation:operation];
        
    } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON) {
        NSLog(@"Error requesting authorization headers from app server: %@", error);
    }];
    
    [operation start];
}

view.py

def request_upload_location(request):

    # DO NOT PASS BACK SECRET!
    _S3_SECRET = "<secret here>"
    _S3_ACCESS_KEY = "<key here>"
    _S3_BUCKET_NAME = "<bucket name here>"
    filename = str(uuid.uuid4()) +".jpeg" #TODO: Support for other non-jpeg file types
    content_type = "image/jpeg"


    now = datetime.utcnow()
    date_string = now.strftime("%a, %d %b %Y %H:%M:%S +0000")
    full_pathname = '/%s/images/%s' % (_S3_BUCKET_NAME, filename)
    string_to_sign = "PUT\n\n%s\n%s\n%s" % (content_type, date_string, full_pathname)
    h = hmac.new(_S3_SECRET, string_to_sign, sha)
    auth_string = base64.encodestring(h.digest()).strip()

    output = { "bucket_name": _S3_BUCKET_NAME,
        "filename": filename,
        "full_pathname" : full_pathname,
        "date_string" : date_string,
        "auth_string" : auth_string,
        "content_type" : content_type,
        "s3_key" : _S3_ACCESS_KEY,
    }

    return HttpResponse(json.dumps(output), content_type="application/json")