Handling redirects with custom NSURLProtocol and HTTP proxy

I have a custom URLProtocol where I want to redirect all traffic via a proxy server.

My current working code looks like that:

+(BOOL)canInitWithRequest:(NSURLRequest*)request
{
    if ([NSURLProtocol propertyForKey:protocolKey inRequest:request])
        return NO;
    NSString *scheme = request.URL.scheme.lowercaseString;
    return [scheme isEqualToString:@"http"] || [scheme isEqualToString:@"https"];
}
-(void)startLoading
{
    NSMutableURLRequest *request = self.request.mutableCopy;
    [NSURLProtocol setProperty:@YES forKey:protocolKey inRequest:request];
    NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
    config.requestCachePolicy = NSURLRequestReloadIgnoringLocalCacheData;
    config.connectionProxyDictionary = @
    {
        (id)kCFNetworkProxiesHTTPEnable:@YES,
        (id)kCFNetworkProxiesHTTPProxy:@"1.2.3.4",
        (id)kCFNetworkProxiesHTTPPort:@8080
    };
    m_session = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:[NSOperationQueue currentQueue]];
    [[m_session dataTaskWithRequest:request] resume];
}

This works great so far. The problem is that there are some url's which use redirection - and I want the redirection to be performed by the proxy server as well, rather than by the device. I've tried to add the following code, but it didn't help:

-(void)URLSession:(NSURLSession*)session task:(NSURLSessionTask*)task willPerformHTTPRedirection:(NSHTTPURLResponse*)response newRequest:(NSURLRequest*)newRequest completionHandler:(void (^)(NSURLRequest*))completionHandler
{
    NSMutableURLRequest *request = newRequest.mutableCopy;
    [NSURLProtocol removePropertyForKey:protocolKey inRequest:request];
    [self.client URLProtocol:self wasRedirectedToRequest:request redirectResponse:response];
    [task cancel];
    [self.client URLProtocol:self didFailWithError:[NSError errorWithDomain:NSCocoaErrorDomain code:NSUserCancelledError userInfo:nil]];
}

The problem is that the new request is not being sent to the proxy server but instead being redirected by the device itself.

Thanks.

It turned out the problem was with the redirection for an HTTPS server, while there is no HTTPS proxy defined. To use HTTPS proxy, the code should looks like:

config.connectionProxyDictionary = @
{
    @"HTTPEnable":@YES,
    (id)kCFStreamPropertyHTTPProxyHost:@"1.2.3.4",
    (id)kCFStreamPropertyHTTPProxyPort:@8080,
    @"HTTPSEnable":@YES,
    (id)kCFStreamPropertyHTTPSProxyHost:@"1.2.3.4",
    (id)kCFStreamPropertyHTTPSProxyPort:@8080
};

Source: How to programmatically add a proxy to an NSURLSession