CA 证书验证与 2 CA iOS

Question

我目前有一个特定的场景。

在 didReceiveAuthenticationChallenge 上，对于 URLRequest 任务，我需要检查 CA 证书是否与我的应用程序包中的 CA 证书相同，如果没有正常评估链。 这是我的代码：

func URLSession(session: NSURLSession!, task: NSURLSessionTask!, didReceiveChallenge challenge: NSURLAuthenticationChallenge!, completionHandler: ((NSURLSessionAuthChallengeDisposition, NSURLCredential!) -> Void)!){
    if let trust = challenge.protectionSpace.serverTrust, challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust, self.trust(chain: trust) {
        completionHander(URLSession.AuthChallengeDisposition.useCredential, URLCredential(trust: trust))
        return
    }
    completionHander(URLSession.AuthChallengeDisposition.cancelAuthenticationChallenge, URLCredential(trust: challenge.protectionSpace.serverTrust!))
}

func trust(chain: SecTrust) -> Bool {
    var trusted = false
    if let certificate = SecTrustGetCertificateAtIndex(chain, 0) {
        // HERE  I NEED TO COMPARE THE CERTIFICATE WITH MY LOCAL CERTIFICATE
        trusted = self.trust(certificate: certificate)
    }
    if !trusted {
    // Evaluate normal chain
        var secResult = SecTrustResultType.invalid
        SecTrustEvaluate(chain, &secResult)
        trusted = secResult == .proceed
    }
    return trusted
}

问题是：这个程序正确吗？ 以及如何将服务器 CA 证书与本地证书进行比较？