iOS 11 HTTPS network request failure with self-signed cert

I wonder if the security policy is changed

iOS 11 does have a number of security policy changes related to HTTPS server trust evaluation.

like self-signed cert is totally prohibited on iOS 11?

But this is not one of them.

For the details you should watch WWDC 2017 Session 701 Your Apps and Evolving Network Security Standards.

It can be resolved by adding [

NSAllowsArbitraryLoads

]

Some sort of ATS exception would have been required even on earlier systems.

For testing purpose, we use a self-signed cert …

I strongly recommend against using a self-signed certificate for testing. There is another, better approach you can use, namely, a custom CA. QA1948 HTTPS and Test Servers discusses the problems with using a self-signed certificate, explains why using a custom CA is better, and gives links to resources that’ll help you set this up.

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

Hi eskimo,

we use self signed certificate too with tls 1.2 and sha256.

We have ca. 2600 Devices in our enveronment. how can we trust our certificate with on 2500 devices ? we use airwatch and ios 11 dont trust our root certificate. ios 10 works fine.

how can we trust our certificate with on 2500 devices ?

This is a very different question from the one posed by hanxuanfromtoronto and it’s somewhat outside of my area of expertise.

Most folks with that many devices use some sort of MDM-based management solution to manage them. That management solution will let deploy a configuration profile containing your root certificate to those devices.

It sounds like you’re trying to do that and it’s not working. If that’s the case then you’ll need to get in touch with folks experienced in this sort of thing:

• The support channel for the management solution you’re using

• AppleCare’s enterprise support options (there’s some links in this post)

• The Apple Support Communities, run by AppleCare, and specifically the in Business and Education topic areas

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

Hi,

I have a problem very similar to the one hanxuanfromtoronto has. When starting a network connection using URLSession on iOS11 with a self-signed certificate, I receive the _kCFStreamErrorCodeKey=-9802 while it used to work fine on iOS10. I verify the server certificate this way:

    func urlSession(_ session: URLSession,  
                    didReceive challenge: URLAuthenticationChallenge,
                    completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void)
    {
        if challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust {
            if challenge.protectionSpace.host == myserver {
         
                if let certFile = Bundle.main.path(forResource: "my-cert", ofType: "cer"),
                    let data = try? Data(contentsOf: URL(fileURLWithPath: certFile)),
                    let cert = SecCertificateCreateWithData(nil, data as CFData),
                    let trust = challenge.protectionSpace.serverTrust
                {
                    SecTrustSetAnchorCertificates(trust, [cert] as CFArray)
                    completionHandler(.useCredential, URLCredential(trust: trust))
                } else {
                    completionHandler(.cancelAuthenticationChallenge, nil)
                }
            } else {
                completionHandler(.performDefaultHandling, nil)
            }
        }
    }

Some investigation showed that setting the following in my Info.plist circumvents the problem:

  <key>NSAppTransportSecurity</key>
  <dict>
       <key>NSAllowsArbitraryLoads</key>
       <false/>
       <key>NSExceptionDomains</key>
       <dict>
            <key>my-server.com</key>
            <dict>
                 <key>NSExceptionRequiresForwardSecrecy</key>
                 <false/>
            </dict>
       </dict>
  </dict>

This suggests that the cipher suite my server uses seems to be deprecated in iOS11. So I tried the following:

$ curl https://my-server.com/some/path -k -v
...
* TLS 1.2 connection using TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
* Server certificate: my-server.com
...

So, my server actually supports the cipher suite TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, which is said to be supported here: https://developer.apple.com/library/content/documentation/General/Reference/InfoPlistKeyReference/Articles/CocoaKeys.html#//apple_ref/doc/uid/TP40009251-SW57

I also checked my server certificate, it is using SHA-256 and a key length of 2048 bit so this should be fine (additionally, if the certificate was weak, setting NSExceptionRequiresForwardSecrecy to false should not solve the problem?).

Watching the WWDC 2017 Session 701 mentioned by eskimo did not get me further either.

Maybe the documentation I linked to is not updated for iOS 11 and the cipher suite my server uses is actually deprecated now? Or am I just getting this wrong?

Thanks for help and suggestions!

Some investigation showed that setting the following in my Info.plist circumvents the problem:

Well, that’s weird. Setting

NSExceptionRequiresForwardSecrecy

shouldn’t magically allow you to connect to a server whose root is not trusted. Doing that requires either

NSExceptionAllowsInsecureHTTPLoads

or one of the global ‘arbitrary loads’ settings.

Maybe the documentation I linked to is not updated for iOS 11 and the cipher suite my server uses is actually deprecated now?

No,

TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256

is a fine cypher suite.

If the server in question is available on the wider Internet and you want to publicise that fact, please post its address. Otherwise you should open a DTS tech support incident and I can look help you out privately.

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

Thanks eskimo & christopher_james — I’m working on the same project as hanxuanfromtoronto and the NSExceptionRequiresForwardSecrecy did in fact resolve our issue. I found this document on TLS changes in iOS 11 and it sounds like the issue is our server doesn’t support the forward secrecy stuff. I’m going to have our server-side folks look into that but at least we’ve resolved it for the meantime!

I did some more investigation and found out the problem is, at least in my case, acutally about the certificate and not the cipher suite. I changed my server to use a system-trusted CA-signed certificate, toggled off the custom root-certificate verification code inside the app and now it works.

The strange thing about this is that NSExceptionRequiresForwardSecrecy solved the issue, since as far as I know this is all about the used cipher suite and not about the certificate. Also, I double checked that my certificate fulfills the ATS requirements (no SHA-1, at least 2048bit), so in theory it should be possible to connect. The error _kCFStreamErrorCodeKey=-9802 (errSSLFatalAlert) is also not quite helpful.

Is there some documentation on what NSExceptionRequiresForwardSecrecy actually does? Seems like it is slightly more than turning off some old cipher suites. And is there any list about when exactly errSSLFatalAlert (-9802) is thrown?

Thanks in advance!

I changed my server to use a system-trusted CA-signed certificate, toggled off the custom root-certificate verification code inside the app and now it works.

To be clear, this is what I recommend in virtually all cases. Disabling the default HTTPS server trust evaluation and relying on your own is very error prone, and the consequences of such an error can be very bad.

Is there some documentation on what

NSExceptionRequiresForwardSecrecy

actually does?

That’s a tricky question to answer. The documented effect of

NSExceptionRequiresForwardSecrecy

is that it enables some extra cypher suites. As you’ve noticed, it can have other effects (we saw this back when ATS was introduced; see this thread for details). It’s best not to rely on those.

Seems like it is slightly more than turning off some old cipher suites. And is there any list about when exactly

errSSLFatalAlert

(-9802) is thrown?

errSSLFatalAlert

means exactly what it says on the tin: the remote peer disconnected the connection with a fatal alert. Alas, this doesn’t help you much when it comes to debugging because other factors can cause that. For example, I’ve seen situations where servers throw a fatal alert because the client had the temerity to request a higher TLS version number.

Which isn’t to say that iOS is behaving correctly here, just that you can’t learn much from the error.

If you want to dig into this you’ll need to look at:

• A system log, to see if the iOS TLS code has logged any info about what went wrong

• A packet trace, to compare the failing and non-failing cases and to see if there really was a fatal alert and, if so, what the alert code was

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

If we go back to the main topic how to enable in iOS 11 to work with self signed certificate.

I tried with

NSExceptionAllowsInsecureHTTPLoads

setting, but with no success.

I have found out that ATS exception domains wont work with IP, so I need actual domain. I have used test "bad ssl" site: https://self-signed.badssl.com/. I am using this site because I want to be sure everything is fine from server perspective. So I have configure:

The problem is that this still does not work. How can I make it work? With what setting? I am using WKWebView with Cordova.

If we go back to the main topic how to enable in iOS 11 to work with self signed certificate.

Sure.

I have found out that ATS exception domains wont work with IP, so I need actual domain.

Correct.

I have used test "bad ssl" site …. I am using this site because I want to be sure everything is fine from server perspective.

Yep, that’s an excellent choice.

Here’s what I did:

1. I created a new app with the following ATS dictionary:

   <key>NSAppTransportSecurity</key>
   <dict>
       <key>NSExceptionDomains</key>
       <dict>
           <key>self-signed.badssl.com</key>
           <dict>
               <key>NSExceptionAllowsInsecureHTTPLoads</key>
               <true/>
           </dict>
       </dict>
   </dict>

   -

2. I set the view controller to this:

   import UIKit class MainViewController : UITableViewController, URLSessionDelegate { var _session: URLSession? = nil var session: URLSession {     if let session = self._session {         return session     }     let config = URLSessionConfiguration.default     config.requestCachePolicy = .reloadIgnoringLocalCacheData     let session = URLSession(configuration: config, delegate: self, delegateQueue: .main)     self._session = session     return session } override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {     let url = URL(string: "https://self-signed.badssl.com/")!     let request = URLRequest(url: url)     self.session.dataTask(with: request) { (_, response, error) in         if let error = error as NSError? {             NSLog("transport error, error: %@ / %d", error.domain, error.code)             return         }         let response = response as! HTTPURLResponse         NSLog("response, statusCode: %d", response.statusCode)     }.resume()     self.tableView.deselectRow(at: indexPath, animated: true) } func urlSession(_ session: URLSession, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {     let method = challenge.protectionSpace.authenticationMethod     let host = challenge.protectionSpace.host     NSLog("challenge %@ for %@", method, host)     switch (method, host) {     case (NSURLAuthenticationMethodServerTrust, "self-signed.badssl.com"):         let trust = challenge.protectionSpace.serverTrust!         let credential = URLCredential(trust: trust)         completionHandler(.useCredential, credential)     default:         completionHandler(.performDefaultHandling, nil)     } } } 

   -

3. I ran the app on iOS 11 and started the test.

4. It printed:

   2017-10-17 09:34:10.986113+0100 BadSSL[59827:13596854] challenge NSURLAuthenticationMethodServerTrust for self-signed.badssl.com
   2017-10-17 09:34:11.264039+0100 BadSSL[59827:13596854] response, statusCode: 200

   -

5. I then took that authentication challenge handling code and plugged it into my standard WKWebView test app.

   func webView(_ webView: WKWebView, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {
       let method = challenge.protectionSpace.authenticationMethod
       let host = challenge.protectionSpace.host
       NSLog("challenge %@ for %@", method, host)
       switch (method, host) {
       case (NSURLAuthenticationMethodServerTrust, "self-signed.badssl.com"):
           let trust = challenge.protectionSpace.serverTrust!
           let credential = URLCredential(trust: trust)
           completionHandler(.useCredential, credential)
       default:
           completionHandler(.performDefaultHandling, nil)
       }
   }

   -

6. I set that app’s ATS exceptions as per step 1.

7. I ran the app, navigated to the site, and saw the big red

   self-signed.badssl.com

   page.

As far as I can tell this all seems to be working just fine.

WARNING The above completely disables security checking on the

self-signed.badssl.com

domain. That’s very poor form in a production app, but it makes sense for this test because I’m trying to show that you can talk to an HTTPS server regardless of its certificate. In a production app you’d want to narrow this exception by explicitly testing the certificate of the server. Or give your server a proper, CA-issued certificate, which avoids all of this drama.

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

I use AFNetworking, with you the same problem, how can I solve it?

I’ve got a couple of suggestions for you here:

• You can ask for help from the support channel for AFNetworking.

• You can dig into the AFNetworking code to work out how it interacts with the operation system, thus allowing you to map the steps I’ve described (in my 17 Oct post) into the AFNetworking world.

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

in ios 11.2 resolved our issue. under ios 11.1 we receive a message in safari " this connection is not private" in ios 11.2 we didnt. what happen in ios 11.2 ? In Relase Notes i found nothing.

I have a question to you.

You said you resolved TLS communication problems in Oct 5.

Is this problem solved in the release up to iOS version 11.1?

When it is not reflected in the release, when will it be reflected?

Some customers said they cannot login to our application or communication becomes unstable after updating iOS to version 11(maybe their OS version is up to 11.0.2).

I think this problem is related to TLS communication problems as you resolved, so I want to confirm this problem is already resolved and reflected to latest OS version or not.

Hi eskimo,

my api is https://loneworker.proraeguardian.com:9093, when set NSExceptionRequiresForwardSecrecy to false, it's ok.

But our certificate is support PFS. i receive log **** when don't set ForwardSecrecy to false.

2018-05-25 00:57:16.653797+0800 SC[4437:3189843] ATS failed system trust

2018-05-25 00:57:16.653927+0800 SC[4437:3189843] System Trust failed for [3:0x1c016ee80]

2018-05-25 00:57:16.654134+0800 SC[4437:3189843] TIC SSL Trust Error [3:0x1c016ee80]: 3:0

2018-05-25 00:57:16.654486+0800 SC[4437:3189843] NSURLSession/NSURLConnection HTTP load failed (kCFStreamErrorDomainSSL, -9802)

2018-05-25 00:57:16.654597+0800 SC[4437:3189843] Task <358A4316-A434-420D-BD92-FFBCE3391101>.<0> HTTP load failed (error code: -1200 [3:-9802])

2018-05-25 00:57:16.654952+0800 SC[4437:3189845] NSURLConnection finished with error - code -1200

Do you have any ideas?