React Native

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 { Cert, Mime } from '@chilkat/react-native'

function chilkatExample() {
  const mime = new Mime();
  try {
    mime.loadMimeFile('qa_data/signed.eml');
  } catch {
    console.log(mime.lastErrorText);
    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.
  try {
    mime.verify();
  } catch {
    console.log(mime.lastErrorText);
    return;
  }

  const n = mime.numSignerCerts;
  const cert = new Cert();
  for (let i = 0; i < n; i++) {
    try {
      mime.lastSignerCert(i, cert);
    } catch {
      console.log(mime.lastErrorText);
      return;
    }

    console.log(`Signer ${i}: ${cert.subjectCN} (issued by ${cert.issuerCN})`);
  }
}