(Mono C#) Trust Specific Root CA Certificates

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

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// 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.

Chilkat.TrustedRoots tRoots = new Chilkat.TrustedRoots();

Chilkat.Cert caCert = new Chilkat.Cert();
bool success = caCert.LoadFromFile("qa_data/certs/aws_root_ca/AmazonRootCA1.cer");
if (success == false) {
    Debug.WriteLine(caCert.LastErrorText);
    return;
}

success = tRoots.AddCert(caCert);

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

success = caCert.LoadFromFile("qa_data/certs/aws_root_ca/AmazonRootCA3.cer");
success = tRoots.AddCert(caCert);

success = caCert.LoadFromFile("qa_data/certs/aws_root_ca/AmazonRootCA4.cer");
success = tRoots.AddCert(caCert);

success = caCert.LoadFromFile("qa_data/certs/aws_root_ca/SFSRootCAG2.cer");
success = tRoots.AddCert(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();

Chilkat.Http http = new Chilkat.Http();

// 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","qa_output/helloWorld.txt");
if (success != true) {
    // The above Download should fail.
    Debug.WriteLine(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/","qa_output/valid.html");
if (success != true) {
    Debug.WriteLine(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."
Debug.WriteLine(http.LastErrorText);

Debug.WriteLine("Success!");