Using URLSessionDelegate

NSURLSessionPinningDelegate.swift

class NSURLSessionPinningDelegate: NSObject, URLSessionDelegate {

    func urlSession(_ session: URLSession, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {
        if challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust {
            if let serverTrust = challenge.protectionSpace.serverTrust {
                if #available(iOS 12.0, *) {
                    let isServerTrusted = SecTrustEvaluateWithError(serverTrust, nil)

                    if(isServerTrusted) {
                        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(for: type(of: self)).path(forResource: "easmart.co", ofType: "der")

                            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
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }

        completionHandler(.cancelAuthenticationChallenge, nil)
    }

}