ssl_pining_urlsession

.swift

func urlSession(_ session: URLSession, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {
    if (challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust) {
        if let serverTrust = challenge.protectionSpace.serverTrust {
            var secresult = SecTrustResultType.invalid
            let status = SecTrustEvaluate(serverTrust, &secresult)
            
            if (errSecSuccess == status) {
                if let serverCertificate = SecTrustGetCertificateAtIndex(serverTrust, 0) {
                    let serverCertificateData = SecCertificateCopyData(serverCertificate)
                    let data = CFDataGetBytePtr(serverCertificateData);
                    let size = CFDataGetLength(serverCertificateData);
                    let cert1 = NSData(bytes: data, length: size)
                    let file_der = Bundle.main.path(forResource: "name-of-cert-file", ofType: "cer")
                    
                    if let file = file_der {
                        if let cert2 = NSData(contentsOfFile: file) {
                            if cert1.isEqual(to: cert2 as Data) {
                                completionHandler(URLSession.AuthChallengeDisposition.useCredential, URLCredential(trust:serverTrust))
                                return
                            }
                        }
                    }
                }
            }
        }
    }
    
    // Pinning failed
    completionHandler(URLSession.AuthChallengeDisposition.cancelAuthenticationChallenge, nil)
}