SocketRocket and iOS certificate pinning

Question

I'm currently using SocketRocket as the WebSocket implementation for my iOS applications and would like to pin my server's CA as a trusted certificate with the SR_SSLPinnedCertificates property. I'm looking for a good example of loading one or more certificates to pass into SocketRocket. I've got the following code to work but I'm not sure it's correct or if there is a more straight-forward approach.

CFArrayRef keyref = NULL;
NSString *path = [[NSBundle mainBundle] pathForResource:@"certificate" ofType:@"p12"];
NSData *data = [[NSData alloc] initWithContentsOfFile:path];
OSStatus status = SecPKCS12Import((__bridge CFDataRef)data, (__bridge CFDictionaryRef)[NSDictionary dictionaryWithObject:@"eftl_key_pass" forKey:(__bridge id)kSecImportExportPassphrase], &keyref);
if (status == noErr) {
    CFDictionaryRef identityDict = CFArrayGetValueAtIndex(keyref, 0);
    SecIdentityRef identityRef = (SecIdentityRef)CFDictionaryGetValue(identityDict, kSecImportItemIdentity);
    SecCertificateRef certRef = NULL;
    SecIdentityCopyCertificate(identityRef, &certRef);
}

Answer 1

Certificate pinning with SocketRocket is done thus:

First, we need to initialize SocketRocket from an NSURLRequest, rather than from an NSURL.

NSURL *url = [[NSURL alloc] initWithString:@"wss://path-to-socket:1234"];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];

Then, let's set up the certificate. It's crucial that your certificate be in the binary DER format, rather than the base64-encoded PEM. The certificate file should be in your main bundle.

NSString *cerPath = [[NSBundle mainBundle] pathForResource:@"myOwnCertificate" ofType:@"cer"];
NSData *certData = [[NSData alloc] initWithContentsOfFile:cerPath];
CFDataRef certDataRef = (__bridge CFDataRef)certData;
SecCertificateRef certRef = SecCertificateCreateWithData(NULL, certDataRef);
id certificate = (__bridge id)certRef;

We then set the request's pinned certificates to an array containing just the one we set up previously.

[request setSR_SSLPinnedCertificates:@[certificate]];

And now we can finalize the socket.

SRWebSocket *socket = [[SRWebSocket alloc] initWithURLRequest:request];       
[socket open];

Answer 2

For the code in Swift:

if let pinnedCertificatePath = NSBundle.mainBundle().pathForResource("subdomain.yourwebsite.com", ofType: "der"),
let pinnedCertificateData = NSData(contentsOfFile: pinnedCertificatePath),
let cert = SecCertificateCreateWithData(nil, pinnedCertificateData) {
    request.SR_SSLPinnedCertificates = [cert]

    // make the websocket call!
    let ws = SRWebSocket(URLRequest: request)
    // configure the websocket
    ws.open()
} else {
    NSLog("Failed to open websocket, could not find pinned certificate!")
}