JavaScript

Create an Opaque (Attached) S/MIME Signature

Demonstrates the Chilkat Mime.ConvertToSigned method, which creates an opaque (attached) S/MIME signature. The only argument is the signing Cert. On success the entity is replaced by a CMS/PKCS #7 signed-data structure that wraps the content inside the signature.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: An opaque signature bundles the content inside the CMS structure, so the message is a single application/pkcs7-mime blob that only S/MIME-aware software can read. It is more tamper-resistant in transit — nothing can alter the content without breaking the wrapper — at the cost of the backward compatibility a detached signature offers. Use it when every recipient is known to support S/MIME.

Note

This example is intended for running within a Chilkat.Js embedded JavaScript engine. All Chilkat JavaScript examples require Chilkat v11.4.0 or greater.

JavaScript

var success = false;

var mime = new CkMime();
success = mime.SetBodyFromPlainText("This message will be signed.");
if (success == false) {
    console.log(mime.LastErrorText);
    return;
}

//  Load the signing certificate (which must have access to its private key) from a PFX file.
//  The PFX password should come from a secure source rather than being hard-coded.
var pfxPassword = "myPfxPassword";
var cert = new CkCert();
success = cert.LoadPfxFile("qa_data/signer.pfx",pfxPassword);
if (success == false) {
    console.log(cert.LastErrorText);
    return;
}

//  Create an OPAQUE (attached) S/MIME signature.  The entity is replaced by a CMS/PKCS #7
//  signed-data structure that wraps the content inside the signature.
success = mime.ConvertToSigned(cert);
if (success == false) {
    console.log(mime.LastErrorText);
    return;
}

success = mime.SaveMime("qa_output/signed_opaque.eml");
if (success == false) {
    console.log(mime.LastErrorText);
    return;
}

console.log("Message converted to an opaque signed message.");