(Swift 3,4,5...) Trust Specific Root CA Certificates

Demonstrates how to trust specific root CA certificates and none others.

Chilkat Downloads for the Swift Programming Language MAC OS X (Cocoa) Objective-C/Swift Libs iOS Objective-C/Swift Libs

func chilkatTest() {
    // This example assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // This example will trust the Amazon root CA certificates provided at 
    // https://www.amazontrust.com/repository/

    // I've previously downloaded the root CA certificates to DER format.
    // Add each to the Chilkat TrustedRoots singleton object.

    let tRoots = CkoTrustedRoots()!

    let caCert = CkoCert()!
    var success: Bool = caCert.load(fromFile: "qa_data/certs/aws_root_ca/AmazonRootCA1.cer")
    if success == false {
        print("\(caCert.lastErrorText!)")
        return
    }

    success = tRoots.add(caCert)

    // Continue with the others.
    // For brevity, we're not checking return values for success/failure.
    success = caCert.load(fromFile: "qa_data/certs/aws_root_ca/AmazonRootCA2.cer")
    success = tRoots.add(caCert)

    success = caCert.load(fromFile: "qa_data/certs/aws_root_ca/AmazonRootCA3.cer")
    success = tRoots.add(caCert)

    success = caCert.load(fromFile: "qa_data/certs/aws_root_ca/AmazonRootCA4.cer")
    success = tRoots.add(caCert)

    success = caCert.load(fromFile: "qa_data/certs/aws_root_ca/SFSRootCAG2.cer")
    success = tRoots.add(caCert)

    // Indicate we don't want to automatically trust the operating system's installed root CA certificates.
    // On a Windows operating system, this would be the registry-based CA certificate stores. 
    // On a Linux system, this could be /etc/ssl/certs/ca-certificates.crt, if it exists.
    tRoots.trustSystemCaRoots = false

    // Activate the trusted roots object.
    // Once activated, all Chilkat objects that use TLS connections (HTTP, REST, Socket, MailMan, IMAP, FTP, etc.)
    // will fail the TLS handshake if the server certificate is not verified and rooted with one of our explicitly trusted root certificates.
    success = tRoots.activate()

    let http = CkoHttp()!

    // Note: We also need to explicitly indicate that server certificates are to be verified.
    http.requireSslCertVerify = true

    // For example, the following should fail because www.chilkatsoft.com's server certificate is not rooted in one of the explicitly trusted root CA certs.
    success = http.download("https://www.chilkatsoft.com/helloWorld.txt", saveToPath: "qa_output/helloWorld.txt")
    if success != true {
        // The above Download should fail.
        print("\(http.lastErrorText!)")

        // There should be a message in the LastErrorText indicating that we were "Unable to build certificate chain to root.."
    }

    // However, we should be able to make TLS connections to good.sca1a.amazontrust.com
    success = http.download("https://good.sca1a.amazontrust.com/", saveToPath: "qa_output/valid.html")
    if success != true {
        print("\(http.lastErrorText!)")
        return
    }

    // We can still examine the LastErrorText and we'll find this message within:  
    // "The public key was successfully validated against the public key of the explicitly trusted root cert."
    print("\(http.lastErrorText!)")

    print("Success!")

}