Perl Requires Chilkat v9.5.0.76+

Verify DKIM-Signature Headers in Downloaded Email

See more DKIM / DomainKey Examples

Downloads email from an IMAP server and verifies the DKIM-Signature header(s) in each email, if present. Chilkat2 Perl

use strict;
use warnings;
use Chilkat2;

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

my $imap = Chilkat2::Imap->new;

# Connect to an IMAP server, login, select mailbox..
# Use TLS
$imap->Ssl(1);
$imap->Port(993);
my $success = $imap->Connect('imap.example.com');
if ($success) {
    $success = $imap->Login('myLogin', 'myPassword');
    if ($success) {
        $success = $imap->SelectMailbox('Inbox');
    }
}

if (!$success) {
    print $imap->LastErrorText, "\n";
    exit;
}

my $dkim = Chilkat2::Dkim->new;

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

# Download emails by sequence numbers (not UIDs).
my $bUid = 0;
my $j = 0;
my $n = $imap->NumMessages;
if ($n > 10) {
    $n = 10;
}

my $json = Chilkat2::JsonObject->new;
$json->EmitCompact(0);

# To verify DKIM-Signature headers, we need the exact unmodified MIME bytes of each email.
my $mimeData = Chilkat2::BinData->new;
my $seqNum = 1;
while ($seqNum <= $n) {
    $success = $imap->FetchSingleBd($seqNum, $bUid, $mimeData);
    if (!$success) {
        print $imap->LastErrorText, "\n";
        exit;
    }

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

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

        $success = $dkim->DkimVerify($j, $mimeData);
        if (!$success) {
            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();