Class

NSURLAuthenticationChallenge

NSURLAuthenticationChallenge encapsulates a challenge from a server requiring authentication from the client.

Overview

Most apps do not create authentication challenges themselves. However, you might need to create authentication challenge objects when adding support for custom networking protocols, as part of your custom NSURLProtocol subclasses.

Instead, your app receives authentication challenges in various NSURLSession, NSURLConnection, and NSURLDownload delegate methods, such as URLSession:task:didReceiveChallenge:completionHandler:. These objects provide the information you’ll need when deciding how to handle a server’s request for authentication. At the core of that authentication challenge is a protection space that defines the type of authentication being requested, the host and port number, the networking protocol, and (where applicable) the authentication realm (a group of related URLs on the same server that share a single set of credentials).

Your app responds to authentication challenges by providing an NSURLCredential object. The details depend on the API you are using and on the type of challenge.

At a high level, if you’re providing the user’s credentials to a server or proxy, the proposedCredential method provides a credential that matches the criteria specified in the protection space, retrieved from the NSURLCredentialStorage class handling the request (assuming such a credential exists).

If the previousFailureCount method returns 0 and the proposed credential exists, the proposed credential has not yet been tried, which means you should try it. If it returns a nonzero result, then the server has rejected the proposed credential, and you should use that credential to populate a password or certificate chooser dialog, then provide a new credential. You can create password-based credentials by calling the credentialWithUser:password:persistence: method or create certificate-based credentials with the credentialWithIdentity:certificates:persistence:.

If the authentication’s protection space uses the NSURLAuthenticationMethodServerTrust authentication method, the request is asking you to verify the server’s authenticity. In this case, the proposedCredential method provides a credential based on the certificates that the server provided as part of its initial TLS handshake. Most apps should request default handling for authentication challenges based on a server trust protection space, but if you need to override the default TLS validation behavior, you can do so as described in Overriding TLS Chain Validation Correctly.

For more information about how URL sessions handle the different types of authentication challenges, see NSURLSession and URL Session Programming Guide.

Symbols

Creating an authentication challenge instance

- initWithAuthenticationChallenge:sender:

Returns an initialized NSURLAuthenticationChallenge object copying the properties from challenge, and setting the authentication sender to sender.

- initWithProtectionSpace:proposedCredential:previousFailureCount:failureResponse:error:sender:

Returns an initialized NSURLAuthenticationChallenge object for the specified protection space, credential, failure count, server response, error, and sender.

Getting authentication challenge properties

error

The error object representing the last authentication failure.

failureResponse

The URL response object representing the last authentication failure.

previousFailureCount

The receiver’s count of failed authentication attempts.

proposedCredential

The proposed credential for this challenge.

protectionSpace

The receiver’s protection space.

sender

The receiver’s sender.

Relationships

Inherits From

Conforms To