Get the S/MIME Signer's Certificate

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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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    success := false

    mime := chilkat.NewMime()
    success = mime.LoadMimeFile("qa_data/signed.eml")
    if success == false {
        fmt.Println(mime.LastErrorText())
        mime.DisposeMime()
        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.
    success = mime.Verify()
    if success != true {
        fmt.Println(mime.LastErrorText())
        mime.DisposeMime()
        return
    }

    n := mime.NumSignerCerts()
    cert := chilkat.NewCert()
    var i int
    for i = 0; i <= n - 1; i++ {
        success = mime.LastSignerCert(i,cert)
        if success == false {
            fmt.Println(mime.LastErrorText())
            mime.DisposeMime()
            cert.DisposeCert()
            return
        }

        fmt.Println("Signer ", i, ": ", cert.SubjectCN(), " (issued by ", cert.IssuerCN(), ")")
    }


    mime.DisposeMime()
    cert.DisposeCert()