Example of NTLM authentication in iOS using NSURLSession

ntlm_authentication_example.swift

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var execButton: UIButton!
    
    var username: String? = nil
    var password: String? = nil
    
    lazy var conn: NSURLSession = {
        let config = NSURLSessionConfiguration.ephemeralSessionConfiguration()
        let session = NSURLSession(configuration: config, delegate: self, delegateQueue: nil)
        return session
    }()
    
    @IBAction func execButtonTapped(sender: UIButton) {
        let url = NSURL(string: "http://somentlmurlc.om")
        let request = NSMutableURLRequest(URL: url!, cachePolicy: .ReloadIgnoringLocalCacheData, timeoutInterval: 60000)
        
        let body = "some body"
        
        request.HTTPMethod = "POST"
        request.HTTPBody = body.dataUsingEncoding(NSUTF8StringEncoding)
        
        let task = conn.dataTaskWithRequest(request)
        task.resume()
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
    
    func login(username: String?, password: String?) {
        self.username = username
        self.password = password
    }
    
    func presentLogin() {
        let alertView = UIAlertController(title: "Please login", message: "You need to provide credentials to make this call.", preferredStyle: .Alert)
        
        let loginAction = UIAlertAction(title: "Login", style: .Default) { action in
            let username = alertView.textFields![0] as UITextField
            let password = alertView.textFields![1] as UITextField
            
            self.login(username.text, password: password.text)
        }
        
        let cancelAction = UIAlertAction(title: "Cancel", style: .Cancel) { _ in }
        
        alertView.addTextFieldWithConfigurationHandler { textField in
            textField.placeholder = "Username"
        }
        
        alertView.addTextFieldWithConfigurationHandler { textField in
            textField.placeholder = "Password"
            textField.secureTextEntry = true
        }
        
        alertView.addAction(cancelAction)
        alertView.addAction(loginAction)
        
        self.presentViewController(alertView, animated: true, completion: {})
    }

    func doesHaveCredentials() -> Bool {
        guard let _ = self.username else { return false }
        guard let _ = self.password else { return false }
        
        return true
    }
}


extension ViewController: NSURLSessionDelegate {

    func URLSession(session: NSURLSession, didReceiveChallenge challenge: NSURLAuthenticationChallenge, completionHandler: (NSURLSessionAuthChallengeDisposition, NSURLCredential?) -> Void) {
        
        print("got challenge")
        
        guard challenge.previousFailureCount == 0 else {
            print("too many failures")
            self.username = nil
            self.password = nil
            challenge.sender?.cancelAuthenticationChallenge(challenge)
            completionHandler(.CancelAuthenticationChallenge, nil)
            return
        }
        
        guard challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodNTLM else {
            print("unknown authentication method \(challenge.protectionSpace.authenticationMethod)")
            challenge.sender?.cancelAuthenticationChallenge(challenge)
            completionHandler(.CancelAuthenticationChallenge, nil)
            return
        }
        
        guard self.doesHaveCredentials() else {
            challenge.sender?.cancelAuthenticationChallenge(challenge)
            completionHandler(.CancelAuthenticationChallenge, nil)
            dispatch_async(dispatch_get_main_queue(), {
                self.presentLogin()
            })
            return
        }
        
        let credentials = NSURLCredential(user: self.username!, password: self.password!, persistence: .ForSession)
        challenge.sender?.useCredential(credentials, forAuthenticationChallenge: challenge)
        completionHandler(.UseCredential, credentials)
    }
    
}

extension ViewController: NSURLSessionDataDelegate {
    
    func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, didReceiveResponse response: NSURLResponse, completionHandler: (NSURLSessionResponseDisposition) -> Void) {
        guard let httpResponse = response as? NSHTTPURLResponse else { return }
        
        print(httpResponse.description)
    }
    
    func URLSession(session: NSURLSession, task: NSURLSessionTask, didCompleteWithError error: NSError?) {
        print("done with error")
    }
    
}

Thank you for this gist. It really helped me a lot and saved me a few hours :D