Rust

Get the S/MIME Signer's Certificate

Demonstrates the Chilkat Mime.LastSignerCert method, which loads the signer certificate at a zero-based index from the most recent successful verification (or security-unwrapping) into a Cert. The first argument is the signer index and the second is the receiving Cert.

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: Verifying tells you the signature is mathematically valid, but you usually also need to know who signed — the subject, the issuer, the validity dates — to decide whether to trust it. This retrieves each signer's certificate after verification so your code can inspect and apply its own trust rules. A message can have multiple signers, so iterate from 0 to NumSignerCerts - 1.

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Rust


let mime = chilkat::Mime::new();
if mime.load_mime_file("qa_data/signed.eml").is_err() {
    println!("{}", mime.last_error_text());
    return;
}

// After a successful verification, load each signer's certificate to inspect it.  The 1st argument
// is the zero-based signer index and the 2nd is a Cert object that receives the certificate.
if mime.verify().is_err() {
    println!("{}", mime.last_error_text());
    return;
}

let n = mime.num_signer_certs();
let cert = chilkat::Cert::new();
for i in 0..n {
    if mime.last_signer_cert(i, &cert).is_err() {
        println!("{}", mime.last_error_text());
        return;
    }

    println!("Signer {}: {} (issued by {})", i, cert.subject_cn(), cert.issuer_cn());
}