Networking with NSURLSession

1. App Transport Security

• Protecting Customer Data

• What is App Transport Security (ATS)?
  • Disallows cleartext HTTP URL loads
  • Encourages best practice secure connections
  • Defaults to stronger security
  • Allows configuration via app's Info.plist

NSAppTransportSecurity
    NSExceptionDomains
      "example.com"
        NSIncludesSubdomains = YES
        NSExceptionRequiresForwardSecrecy = NO 
        NSExceptionMinimumTLSVersion = "TLSv1.1"

NSAppTransportSecurity
  NSExceptionDomains
   "media.example.com"
     NSExceptionAllowsInsecureHTTPLoads = YES

NSAppTransportSecurity
   NSAllowsArbitraryLoads = YES

NSAppTransportSecurity NSAllowsArbitraryLoads
NSExceptionDomains
   "secure.example.com"
     NSExceptionAllowsInsecureHTTPLoads = NO

• Configuring ATS

• Diagnosing issues

  • Active when you build your app for iOS 9 and OS X El Capitan
  • "http://" to "https://" is automatic
  • Use NSAllowsArbitrary Loads for quick triage
  • Log NSURLSession errors
  • CFNETWORK_DIAGNOSTICS=1

• Protecting Customer Data

• Next steps

  • Use HTTPS for new projects
  • Transition existing apps from HTTP to HTTPS
  • Use exceptions where needed

2. New Protocol Support in NSURLSession

• HTTP/2

  • Adoption on the client
  • NSURLSession supports HTTP/2 protocol automatically
  • No source code changes needed

let sessionConfig = NSURLSessionConfiguration.defaultSessionConfiguration()
let session = NSURLSession(configuration: sessionConfig)
let url = NSURL(string: "https://www.example.com")!
let task = session.dataTaskWithURL(url) {
     (data: NSData?, response: NSURLResponse?, error: NSError?) in 
        ...
}task?.resume()

3. API Changes

• NSURLConnection

• Deprecated in OS X 10.11 and iOS 9.0

  • Not going away, apps using it will still work
  • New features will be added to NSURLSession

• Not supported on watchOS

• Switching to NSURLSession is easy

• Switching to NSURLSession

  let queue: NSOperationQueue = ...
  let url = NSURL(string: "https://www.example.com")!
  let request = NSURLRequest(URL: url)
  NSURLConnection.sendAsynchronousRequest(request, queue: queue) { 
    (response: NSURLResponse?, data: NSData?, error: NSError?) in 
        ...
  }
  

  let queue: NSOperationQueue = ...
  let url = NSURL(string: "https://www.example.com")!
  let request = NSURLRequest(URL: url)
  NSURLConnection.sendAsynchronousRequest(request, queue: queue) {
  (response: NSURLResponse?, data: NSData?, error: NSError?) in
  ...
  }
  let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
  (data: NSData?, response: NSURLResponse?, error: NSError?) in
  ...
  }
  task?.resume()

4. New NSURLSession API

• Sharing Cookies

• Between Apps and Extensions
  • Apps and their extensions have different cookie storages by default
  • Can use application groups to get a shared data containerOS X 10.11 and iOS 9 introduce new API to create a shared cookie storage

5. New NSHTTPCookieStorage API

let ident = "group.mycompany.mygroupname"let cookieStorage =  NSHTTPCookieStorage.sharedCookieStorageForGroupContainerIdentifier( identifier: ident)
let config = NSURLSessionConfiguration.defaultSessionConfiguration()config.HTTPCookieStorage = cookieStorage
let session = NSURLSession(configuration: config)

6. NSURLSessionStreamTask

• Asynchronous read

  let task = NSURLSession.sharedSession().streamTaskWithHostName("chat.example.com", port: 5555)!
  task.resume()
  task.readDataOfMinLength(16384, maxLength:65536, timeout: 30.0) {
   (data: NSData?, eof: Bool, error: NSError?) in
    ...
   }
  
  let task = NSURLSession.sharedSession().streamTaskWithHostName("chat.example.com", port: 5555)!
  task.resume()
  let data: NSData = ...task.writeData(data, timeout: 30.0) { (error: NSError?) in
    ...
  }
  

• Enabling TLS

  let task = NSURLSession.sharedSession().streamTaskWithHostName("chat.example.com", port: 5555)!
  task.startSecureConnection()
  task.resume()
  let data: NSData = ...task.writeData(data, timeout: 30.0) { (error: NSError?) in
    ...
  }
  

• NSStream support

  let streamTask: NSURLSessionStreamTask = ...
  streamTask.captureStreams()
  

• NSStream support

  func URLSession(session: NSURLSession,streamTask: NSURLSessionStreamTask, didBecomeInputStream inputStream: NSInputStream, outputStream: NSOutputStream) {
  // Can pass inputStream / outputStream to APIs that consume NSStreams
  }
  

• Other (informational) delegate methods

  optional func URLSession(session: NSURLSession, betterRouteDiscoveredForStreamTask streamTask: NSURLSessionStreamTask)
  

• Other (informational) delegate methods

  optional func URLSession(session: NSURLSession, betterRouteDiscoveredForStreamTaskstreamTask: NSURLSessionStreamTask)
  optional func URLSession(session: NSURLSession, readClosedForStreamTask streamTask:NSURLSessionStreamTask)
  optional func URLSession(session: NSURLSession, writeClosedForStreamTask streamTask:NSURLSessionStreamTask)
  

• DataTask conversion

  func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, didReceiveResponse response: NSURLResponse, completionHandler: (NSURLSessionResponseDisposition) -> Void) {
     completionHandler(.BecomeStream)
  }
  func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, didBecomeStreamTask streamTask: NSURLSessionStreamTask) {
  }