Java

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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import com.chilkatsoft.chilkat2.Cert;
import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.Mime;

public class ChilkatExample {

    public static void main(String[] args) {
        Mime mime = new Mime();
        try {
            mime.loadMimeFile("qa_data/signed.eml");

            // 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.
            mime.verify();
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        int n = mime.getNumSignerCerts();
        Cert cert = new Cert();
        for (int i = 0; i < n; i++) {
            try {
                mime.lastSignerCert(i, cert);
            } catch (ChilkatException e) {
                System.out.println(e.getLastErrorText());
                return;
            }

            System.out.println("Signer " + i + ": " + cert.getSubjectCN() + " (issued by " + cert.getIssuerCN() + ")");
        }
    }
}