URLSession not working with URLCredential - ios

Question

I have an API I am trying to connect to and the server is Windows Authentication.
I am trying to use URLSession with URLCredential with the delegate methods
func urlSession(_ session: URLSession, didReceive challenge: URLAuthenticationChallenge, completionHandler: #escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Swift.Void){
var disposition: URLSession.AuthChallengeDisposition = URLSession.AuthChallengeDisposition.performDefaultHandling
var credential:URLCredential?
print(challenge.protectionSpace.authenticationMethod)
if challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust {
credential = URLCredential(trust: challenge.protectionSpace.serverTrust!)
if (credential != nil) {
disposition = URLSession.AuthChallengeDisposition.useCredential
}
else
{
disposition = URLSession.AuthChallengeDisposition.performDefaultHandling
}
}
else
{
disposition = URLSession.AuthChallengeDisposition.cancelAuthenticationChallenge
}
completionHandler(disposition, credential);
}
This code runs twice as after doing some printing is because there are two Authentication Methods:
NSURLAuthenticationMethodServerTrust and NSURLAuthenticationMethodNTLM when it runs through the NSURLAuthenticationMethodServerTrust everything is fine, but when it runs NSURLAuthenticationMethodNTLM I get an error on this line:
credential = URLCredential(trust: challenge.protectionSpace.serverTrust!)
saying this:
fatal error: unexpectedly found nil while unwrapping an Optional value
but only when I change this condition from
if challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust {
to
if challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodNTLM {
What Am I doing wrong?
Here is the method I am using to try to connect to that API
func loginUser(_ username: String, password: String, completion: #escaping (_ result: Bool) -> Void)
{
//Create request URL as String
let requestString = String(format:"%#", webservice) as String
//Covert URL request string to URL
guard let url = URL(string: requestString) else {
print("Error: cannot create URL")
return
}
//Convert URL to URLRequest
let urlRequest = URLRequest(url: url)
print(urlRequest)
//Add the username and password to URLCredential
credentials = URLCredential(user:username, password:password, persistence: .forSession)
print(credentials)
//Setup the URLSessionConfiguration
let config = URLSessionConfiguration.default
//Setup the URLSession
let session = URLSession(configuration: config, delegate: self, delegateQueue: nil)
//Prepare the task to get data.
let task = session.dataTask(with: urlRequest, completionHandler: { (data, response, error) in
DispatchQueue.main.async(execute: {
print(error!)
if(error == nil)
{
completion(true)
}
else
{
completion(false)
}
})
})
//Run the task to get data.
task.resume()
}

Answer 1

In the Apple documentation for URLProtectionSpace.serverTrust, it says:
nil if the authentication method of the protection space is not server trust.
So, you are trying to unwrap an optional value of nil, which of course would cause a crash.
In your case, you could probably just replace the entire function with (untested):
func urlSession(_ session: URLSession, didReceive challenge: URLAuthenticationChallenge, completionHandler: #escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Swift.Void){
var disposition: URLSession.AuthChallengeDisposition = URLSession.AuthChallengeDisposition.performDefaultHandling
print(challenge.protectionSpace.authenticationMethod)
if challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust {
disposition = URLSession.AuthChallengeDisposition.performDefaultHandling
}
else
{
disposition = URLSession.AuthChallengeDisposition.cancelAuthenticationChallenge
}
completionHandler(disposition, credential);
}