Rust

Add an S/MIME Detached Signature

Demonstrates the Chilkat Mime.AddDetachedSignature method, which creates an S/MIME detached signature. The only argument is the signing Cert, which must have access to its private key. On success the entity becomes a multipart/signed with the content and a separate signature part.

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: A detached signature (multipart/signed) keeps the original content readable alongside a separate signature part — so recipients whose software does not understand S/MIME still see the message, they just cannot verify it. That backward compatibility makes detached the usual choice for signed email. The signer proves authorship with a certificate that carries its private key.

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Rust


let mime = chilkat::Mime::new();
if mime.set_body_from_plain_text("This message will be signed.").is_err() {
    println!("{}", mime.last_error_text());
    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.
let pfx_password = "myPfxPassword".to_string();
let cert = chilkat::Cert::new();
if cert.load_pfx_file("qa_data/signer.pfx", &pfx_password).is_err() {
    println!("{}", cert.last_error_text());
    return;
}

// Create an S/MIME detached signature.  The object becomes a multipart/signed entity with the
// original content and a separate signature part.
if mime.add_detached_signature(&cert).is_err() {
    println!("{}", mime.last_error_text());
    return;
}

if mime.save_mime("qa_output/signed.eml").is_err() {
    println!("{}", mime.last_error_text());
    return;
}

println!("Detached signature added.");