Manually validate TLS Certificate (ios objective-c)

Question

I am creating an iOS application that communicates with a web server using TLS. When I access the web server, it presents a certificate to my device, and I would like to validate that I can trust it.

I have the root certificate embedded in my xcode project as a der file. The code I have so far gets NSString versions of both certificates in the NSURLConnection's delegate function for authentication challenge.

Any ideas on how to validate manually?

Here's my current code:

- (void)connection:(NSURLConnection *)connection willSendRequestForAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge {
NSLog(@"Certificate challenge");
if (self.stageNum==0) {
    id <NSURLAuthenticationChallengeSender> sender=challenge.sender;
    NSURLProtectionSpace *protectionSpace=challenge.protectionSpace;
    SecTrustRef trust=[protectionSpace serverTrust];

    //Get server certificate
    SecCertificateRef certificate=SecTrustGetCertificateAtIndex(trust, 0);
    NSData *serverCertificateData=(__bridge NSData *)SecCertificateCopyData(certificate);
    NSString *serverBase64Certificate=[serverCertificateData base64EncodedStringWithOptions:0];

    //Get our certificate
    NSData *certData1 = [[NSData alloc] initWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"SUMOSRoot" ofType:@"der"]];
    NSString *certBase64=[certData1 base64EncodedStringWithOptions:0];

    //Heres where I need to compare the certificates
    //
    //

    [sender useCredential:[NSURLCredential credentialForTrust:protectionSpace.serverTrust] forAuthenticationChallenge:challenge];
}
}

Answer 1

I think this post solves your purpose. Beautifully written/explained.

http://www.techrepublic.com/blog/software-engineer/use-https-certificate-handling-to-protect-your-ios-app/

People who are too lazy to open the links, i'll add some description over here from the post.