How to use NSURLConnection to connect with SSL for an untrusted cert?

Question

I have the following simple code to connect to a SSL webpage

NSMutableURLRequest *urlRequest=[NSMutableURLRequest requestWithURL:url];
[ NSURLConnection sendSynchronousRequest: urlRequest returningResponse: nil error: &error ];

Except it gives an error if the cert is a self signed one Error Domain=NSURLErrorDomain Code=-1202 UserInfo=0xd29930 "untrusted server certificate". Is there a way to set it to accept connections anyway (just like in a browser you can press accept) or a way to bypass it?

Answer 1

NSURLRequest has a private method called setAllowsAnyHTTPSCertificate:forHost:, which will do exactly what you'd like. You could define the allowsAnyHTTPSCertificateForHost: method on NSURLRequest via a category, and set it to return YES for the host that you'd like to override.

Answer 2

If you're unwilling (or unable) to use private APIs, there's an open source (BSD license) library called ASIHTTPRequest that provides a wrapper around the lower-level CFNetwork APIs. They recently introduced the ability to allow HTTPS connections using self-signed or untrusted certificates with the -setValidatesSecureCertificate: API. If you don't want to pull in the whole library, you could use the source as a reference for implementing the same functionality yourself.

Answer 3

Nathan de Vries, Can you please explain me in more detail about NRURLRequest and setAllowsAnyHTTPSCertificate:forHost:?

Answer 4

There is a supported API for accomplishing this! Add something like this to your NSURLConnection delegate:

- (BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace:(NSURLProtectionSpace *)protectionSpace {
  return [protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust];
}

- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge {
  if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust])
    if ([trustedHosts containsObject:challenge.protectionSpace.host])
      [challenge.sender useCredential:[NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust] forAuthenticationChallenge:challenge];

  [challenge.sender continueWithoutCredentialForAuthenticationChallenge:challenge];
}

Note that connection:didReceiveAuthenticationChallenge: can send its message to challenge.sender (much) later, after presenting a dialog box to the user if necessary, etc.

Answer 5

I can't take any credit for this, but this one I found worked really well for my needs. "shouldAllowSelfSignedCert" is my BOOL variable. Just add to your NSURLConnection delegate and you should be rockin for a quick bypass on a per connection basis.

    - (BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace:(NSURLProtectionSpace *)space {
     if([[space authenticationMethod] isEqualToString:NSURLAuthenticationMethodServerTrust]) {
          if(shouldAllowSelfSignedCert) {
               return YES; // Self-signed cert will be accepted
          } else {
               return NO;  // Self-signed cert will be rejected
          }
          // Note: it doesn't seem to matter what you return for a proper SSL cert
          //       only self-signed certs
     }
     // If no other authentication is required, return NO for everything else
     // Otherwise maybe YES for NSURLAuthenticationMethodDefault and etc.
     return NO;
}

Answer 6

The category workaround posted by Nathan de Vries will pass the AppStore private API checks, and is useful in cases where you do not have control of the NSUrlConnection object. One example is NSXMLParser which will open the URL you supply, but does not expose the NSURLRequest or NSURLConnection.

In iOS 4 the workaround still seems to work, but only on the device, the Simulator does not invoke the allowsAnyHTTPSCertificateForHost: method anymore.