(PHP Extension) Verify DKIM-Signature Headers in Downloaded Email

Downloads email from an IMAP server and verifies the DKIM-Signature header(s) in each email, if present.

Chilkat PHP Downloads PHP Extension for Windows, Linux, MacOS, Alpine Linux, Solaris

<?php

// The version number (9_5_0) should match version of the Chilkat extension used, omitting the micro-version number.
// For example, if using Chilkat v9.5.0.48, then include as shown here:
include("chilkat_9_5_0.php");

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

$imap = new CkImap();

// Connect to an IMAP server, login, select mailbox..
// Use TLS 
$imap->put_Ssl(true);
$imap->put_Port(993);
$success = $imap->Connect('imap.someMailServer.com');
if ($success == true) {
    $success = $imap->Login('myLogin','myPassword');
    if ($success == true) {
        $success = $imap->SelectMailbox('Inbox');
    }

}

if ($success != true) {
    print $imap->lastErrorText() . "\n";
    exit;
}

$dkim = new CkDkim();

// Download a max of 10 emails and verify any DKIM-Signature headers
// that are present.

// Download emails by sequence numbers (not UIDs).
$bUid = false;

$n = $imap->get_NumMessages();
if ($n > 10) {
    $n = 10;
}

$json = new CkJsonObject();
$json->put_EmitCompact(false);

// To verify DKIM-Signature headers, we need the exact unmodified MIME bytes of each email.
$mimeData = new CkBinData();
$seqNum = 1;
while ($seqNum <= $n) {
    // The FetchSingleBd method was introduced in v9.5.0.76
    $success = $imap->FetchSingleBd($seqNum,$bUid,$mimeData);
    if ($success != true) {
        print $imap->lastErrorText() . "\n";
        exit;
    }

    // Get the number of DKIM-Signature headers.
    $numDkim = $dkim->NumDkimSigs($mimeData);

    // Verify each..
    $j = 0;
    while ($j < $numDkim) {
        print '------ DKIM Signature ' . $j . "\n";

        $success = $dkim->DkimVerify($j,$mimeData);
        if ($success != true) {
            print 'Not valid.' . "\n";
        }
        else {
            print 'valid.' . "\n";
        }

        // Show the additional information about the signature verification
        $json->Load($dkim->verifyInfo());
        print $json->emit() . "\n";

        // The JSON contains information such as this:

        // 	{
        // 	  "domain": "amazonses.com",
        // 	  "selector": "7v7vs6w47njt4pimodk5mmttbegzsi6n",
        // 	  "publicKey": "MIGfMA0GCSqG...v2GvWPqGHz6uqeQIDAQAB",
        // 	  "canonicalization": "relaxed/simple",
        // 	  "algorithm": "rsa-sha256",
        // 	  "signedHeaders": "Subject:From:To:Date:Mime-Version:Content-Type:References:Message-Id:Feedback-ID",
        // 	  "verified": "yes"
        // 	}

        $j = $j + 1;
    }

    $seqNum = $seqNum + 1;
}

$success = $imap->Disconnect();

?>