PHP

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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<?php

use Chilkat2\Cert;
use Chilkat2\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 (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

$n = $mime->NumSignerCerts;
$cert = new Cert();
for ($i = 0; $i < $n; $i++) {
    try {
        $mime->LastSignerCert($i, $cert);
    } catch (\Chilkat2\Exception $e) {
        echo $e->getMessage(), "\n";
        exit;
    }

    echo 'Signer ', $i, ': ', $cert->SubjectCN, ' (issued by ', $cert->IssuerCN, ")\n";
}