UIWebView to view self signed websites (No private api, not NSURLConnection) – is it possible?

There’s a load of questions which ask this: Can I get UIWebView to view a self signed HTTPS website?

And the answers always involve either:

  • iOS JavaScript bridge
  • Freeing iOS UIWebView resources after usage
  • NSExceptionDomains xcode 8 not working
  • Gesture recognition with UIWebView
  • UIWebView and CSS fixed position
  • Check if an URL has got http:// prefix
    1. Use the private api call for NSURLRequest: allowsAnyHTTPSCertificateForHost
    2. Use NSURLConnection instead and the delegate canAuthenticateAgainstProtectionSpace etc

    For me, these won’t do.
    (1) – means I can’t submit to the app store successfully.
    (2) – using NSURLConnection means the CSS, images and other things that have to be fetched from the server after receiving the initial HTML page do not load.

    Does anyone know how to use UIWebView to view a self-signed https webpage please, which does not involve the two methods above?

    Or – If using NSURLConnection can in fact be used to render a webpage complete with CSS, images and everything else – that would be great!

    Cheers,
    Stretch.

    8 Solutions Collect From Internet About “UIWebView to view self signed websites (No private api, not NSURLConnection) – is it possible?”

    Finally I got it!

    What you can do is this:

    Initiate your request using UIWebView as normal. Then – in webView:shouldStartLoadWithRequest – we reply NO, and instead start an NSURLConnection with the same request.

    Using NSURLConnection, you can communicate with a self-signed server, as we have the ability to control the authentication through the extra delegate methods which are not available to a UIWebView. So using connection:didReceiveAuthenticationChallenge we can authenticate against the self signed server.

    Then, in connection:didReceiveData, we cancel the NSURLConnection request, and start the same request again using UIWebView – which will work now, because we’ve already got through the server authentication 🙂

    Here are the relevant code snippets below.

    Note: Instance variables you will see are of the following type:
    UIWebView *_web
    NSURLConnection *_urlConnection
    NSURLRequest *_request

    (I use an instance var for _request as in my case it’s a POST with lots of login details, but you could change to use the request passed in as arguments to the methods if you needed.)

    #pragma mark - Webview delegate
    
    // Note: This method is particularly important. As the server is using a self signed certificate,
    // we cannot use just UIWebView - as it doesn't allow for using self-certs. Instead, we stop the
    // request in this method below, create an NSURLConnection (which can allow self-certs via the delegate methods
    // which UIWebView does not have), authenticate using NSURLConnection, then use another UIWebView to complete
    // the loading and viewing of the page. See connection:didReceiveAuthenticationChallenge to see how this works.
    - (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType;
    {
        NSLog(@"Did start loading: %@ auth:%d", [[request URL] absoluteString], _authenticated);
    
        if (!_authenticated) {
            _authenticated = NO;
    
            _urlConnection = [[NSURLConnection alloc] initWithRequest:_request delegate:self];
    
            [_urlConnection start];
    
            return NO;
        }
    
        return YES;
    }
    
    
    #pragma mark - NURLConnection delegate
    
    - (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge;
    {
        NSLog(@"WebController Got auth challange via NSURLConnection");
    
        if ([challenge previousFailureCount] == 0)
        {
            _authenticated = YES;
    
            NSURLCredential *credential = [NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust];
    
            [challenge.sender useCredential:credential forAuthenticationChallenge:challenge];
    
        } else
        {
            [[challenge sender] cancelAuthenticationChallenge:challenge];
        }
    }
    
    - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response;
    {
        NSLog(@"WebController received response via NSURLConnection");
    
        // remake a webview call now that authentication has passed ok.
        _authenticated = YES;
        [_web loadRequest:_request];
    
        // Cancel the URL connection otherwise we double up (webview + url connection, same url = no good!)
        [_urlConnection cancel];
    }
    
    // We use this method is to accept an untrusted site which unfortunately we need to do, as our PVM servers are self signed.
    - (BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace:(NSURLProtectionSpace *)protectionSpace
    {
        return [protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust];
    }
    

    I hope this helps others with the same issue I was having!

    Stretch’s answer appears to be a great workaround, but it uses deprecated APIs. So, I thought it might be worthy of an upgrade to the code.

    For this code sample, I added the routines to the ViewController which contains my UIWebView. I made my UIViewController a UIWebViewDelegate and a NSURLConnectionDataDelegate. Then I added 2 data members: _Authenticated and _FailedRequest. With that, the code looks like this:

    -(BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {
        BOOL result = _Authenticated;
        if (!_Authenticated) {
            _FailedRequest = request;
            [[NSURLConnection alloc] initWithRequest:request delegate:self];
        }
        return result;
    }
    
    -(void)connection:(NSURLConnection *)connection willSendRequestForAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge {
        if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust]) {
            NSURL* baseURL = [_FailedRequest URL];
            if ([challenge.protectionSpace.host isEqualToString:baseURL.host]) {
                NSLog(@"trusting connection to host %@", challenge.protectionSpace.host);
                [challenge.sender useCredential:[NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust] forAuthenticationChallenge:challenge];
            } else
                NSLog(@"Not trusting connection to host %@", challenge.protectionSpace.host);
        }
        [challenge.sender continueWithoutCredentialForAuthenticationChallenge:challenge];
    }
    
    -(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)pResponse {
        _Authenticated = YES;
        [connection cancel];
        [_WebView loadRequest:_FailedRequest];
    }
    

    I set _Authenticated to NO when I load the view and don’t reset it. This seems to allow the UIWebView to make multiple requests to the same site. I did not try switching sites and trying to come back. That may cause the need for resetting _Authenticated. Also, if you are switching sites, you should keep a dictionary (one entry for each host) for _Authenticated instead of a BOOL.

    This is the Panacea!


    BOOL _Authenticated;
    NSURLRequest *_FailedRequest;
    
    #pragma UIWebViewDelegate
    
    -(BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request   navigationType:(UIWebViewNavigationType)navigationType {
        BOOL result = _Authenticated;
        if (!_Authenticated) {
            _FailedRequest = request;
            NSURLConnection *urlConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
            [urlConnection start];
        }
        return result;
    }
    
    #pragma NSURLConnectionDelegate
    
    -(void)connection:(NSURLConnection *)connection willSendRequestForAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge {
        if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust]) {
            NSURL* baseURL = [NSURL URLWithString:@"your url"];
            if ([challenge.protectionSpace.host isEqualToString:baseURL.host]) {
                NSLog(@"trusting connection to host %@", challenge.protectionSpace.host);
                [challenge.sender useCredential:[NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust] forAuthenticationChallenge:challenge];
            } else
                NSLog(@"Not trusting connection to host %@", challenge.protectionSpace.host);
        }
        [challenge.sender continueWithoutCredentialForAuthenticationChallenge:challenge];
    }
    
    -(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)pResponse {
    _Authenticated = YES;
        [connection cancel];
        [self.webView loadRequest:_FailedRequest];
    }
    
    - (void)viewDidLoad{
       [super viewDidLoad];
    
        NSURL *url = [NSURL URLWithString:@"your url"];
        NSURLRequest *requestURL = [NSURLRequest requestWithURL:url];
        [self.webView loadRequest:requestURL];
    
    // Do any additional setup after loading the view.
    }
    

    If you want to access a private server with a self-signed certificate just for testing you don’t have to write code. You can manually do a system-wide import of the certificate.

    To do this, you need to download the server certificate with mobile safari, which then prompts for an import.

    This would be usable under the following circumstances:

    • the number of test devices is small
    • you’re trusting the certificate of the server

    If you don’t have access to the server certificate, you can fallback to the following method for extracting it from any HTTPS-server (at least on Linux/Mac, windows guys will have to download an OpenSSL binary somewhere):

    echo "" | openssl s_client -connect $server:$port -prexit 2>/dev/null | sed -n -e '/BEGIN\ CERTIFICATE/,/END\ CERTIFICATE/ p' >server.pem
    

    Note, that depending on the OpenSSL version, the certificate may be doubled in the file, so best have a look at it with a text editor. Put the file somewhere on the network or use the

    python -m SimpleHTTPServer 8000

    shortcut to access it from your mobile safari at http://$your_device_ip:8000/server.pem.

    This is a clever workaround. However, a possibly better (although more code intensive) solution would be to use an NSURLProtocol as demonstrated in Apple’s CustomHTTPProtocol sample code. From the README:

    “CustomHTTPProtocol shows how to use an NSURLProtocol subclass to intercept the NSURLConnections made by a high-level subsystem that does not otherwise expose its network connections. In this specific case, it intercepts the HTTPS requests made by a web view and overrides server trust evaluation, allowing you to browse a site whose certificate is not trusted by default.”

    Checkout the full example:
    https://developer.apple.com/library/ios/samplecode/CustomHTTPProtocol/Introduction/Intro.html

    This is a swift 2.0 compatible equivalent that works for me. I have not converted this code to use NSURLSession instead of NSURLConnection, and suspect that it would add a lot of complexity to get it right.

    var authRequest : NSURLRequest? = nil
    var authenticated = false
    var trustedDomains = [:] // set up as necessary
    
    func webView(webView: UIWebView, shouldStartLoadWithRequest request: NSURLRequest, navigationType: UIWebViewNavigationType) -> Bool {
        if !authenticated {
            authRequest = request
            let urlConnection: NSURLConnection = NSURLConnection(request: request, delegate: self)!
            urlConnection.start()
            return false
        }
        else if isWebContent(request.URL!) { // write your method for this
            return true
        }
        return processData(request) // write your method for this
    }
    
    func connection(connection: NSURLConnection, willSendRequestForAuthenticationChallenge challenge: NSURLAuthenticationChallenge) {
        if challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust {
            let challengeHost = challenge.protectionSpace.host
            if let _ = trustedDomains[challengeHost] {
                challenge.sender!.useCredential(NSURLCredential(forTrust: challenge.protectionSpace.serverTrust!), forAuthenticationChallenge: challenge)
            }
        }
        challenge.sender!.continueWithoutCredentialForAuthenticationChallenge(challenge)
    }
    
    func connection(connection: NSURLConnection, didReceiveResponse response: NSURLResponse) {
        authenticated = true
        connection.cancel()
        webview!.loadRequest(authRequest!)
    }
    

    Here the working code of swift 2.0

    var authRequest : NSURLRequest? = nil
    var authenticated = false
    
    
    func webView(webView: UIWebView, shouldStartLoadWithRequest request: NSURLRequest, navigationType: UIWebViewNavigationType) -> Bool {
                    if !authenticated {
                        authRequest = request
                        let urlConnection: NSURLConnection = NSURLConnection(request: request, delegate: self)!
                        urlConnection.start()
                        return false
                    }
                    return true
    }
    
    func connection(connection: NSURLConnection, didReceiveResponse response: NSURLResponse) {
                    authenticated = true
                    connection.cancel()
                    webView!.loadRequest(authRequest!)
    }
    
    func connection(connection: NSURLConnection, willSendRequestForAuthenticationChallenge challenge: NSURLAuthenticationChallenge) {
    
                    let host = "www.example.com"
    
                    if challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust &&
                        challenge.protectionSpace.host == host {
                        let credential = NSURLCredential(forTrust: challenge.protectionSpace.serverTrust!)
                        challenge.sender!.useCredential(credential, forAuthenticationChallenge: challenge)
                    } else {
                        challenge.sender!.performDefaultHandlingForAuthenticationChallenge!(challenge)
                    }
    }
    

    To build off of @spirographer’s answer, I put something together for a Swift 2.0 use case with NSURLSession. However, this is still NOT working. See more below.

    func webView(webView: UIWebView, shouldStartLoadWithRequest request: NSURLRequest, navigationType: UIWebViewNavigationType) -> Bool {
        let result = _Authenticated
        if !result {
            let sessionConfiguration = NSURLSessionConfiguration.defaultSessionConfiguration()
            let session = NSURLSession(configuration: sessionConfiguration, delegate: self, delegateQueue: NSOperationQueue.mainQueue())
            let task = session.dataTaskWithRequest(request) {
                (data, response, error) -> Void in
                if error == nil {
                    if (!self._Authenticated) {
                        self._Authenticated = true;
                        let pageData = NSString(data: data!, encoding: NSUTF8StringEncoding)
                        self.webView.loadHTMLString(pageData as! String, baseURL: request.URL!)
    
                    } else {
                        self.webView.loadRequest(request)
                    }
                }
            }
            task.resume()
            return false
        }
        return result
    }
    
    func URLSession(session: NSURLSession, didReceiveChallenge challenge: NSURLAuthenticationChallenge, completionHandler: (NSURLSessionAuthChallengeDisposition, NSURLCredential?) -> Void) {
        completionHandler(NSURLSessionAuthChallengeDisposition.UseCredential, NSURLCredential(forTrust: challenge.protectionSpace.serverTrust!))
    }
    

    I will get back the initial HTML response, so the page renders the plain HTML, but there is no CSS styles applied to it (seems like the request to get CSS is denied). I see a bunch of these errors:

    NSURLSession/NSURLConnection HTTP load failed (kCFStreamErrorDomainSSL, -9813)
    

    It seems like any request made with webView.loadRequest is done not within the session, which is why the connection is rejected. I do have Allow Arbitrary Loads set in Info.plist. What confuses me is why NSURLConnection would work (seemingly the same idea), but not NSURLSession.