Verify S/MIME Signature

Perl example to verify an S/MIME signature and unwrap the S/MIME to get the original MIME prior to signing/encrypting.

Download Chilkat Perl Module

use chilkat;

$mime = new chilkat::CkMime();

#  Any string argument automatically begins the 30-day trial.
$success = $mime->UnlockComponent("30-day trial");
if ($success != 1) {
    print "MIME component unlock failed" . "\n";
    exit;
}

#  Load an S/MIME message from a file:
$success = $mime->LoadMimeFile("signedMime.txt");
if ($success != 1) {
    print $mime->lastErrorText() . "\n";
    exit;
}

#  The ContainsEncryptedParts/ContainsSignedParts methods
#  can be called to determine if the MIME is encrypted and/or signed:
$isEncrypted = $mime->ContainsEncryptedParts();
$isSigned = $mime->ContainsSignedParts();

#  We don't want the "unwrap extras".  You'll see what those
#  are in a few moments...
$mime->put_UnwrapExtras(0);

#  To verify the signature, call UnwrapSecurity.  This will
#  verify the signature(s) and decrypt the S/MIME and restore
#  the MIME to the unsigned/unencrypted state.
#  The results of what was found are present in the MIME object's
#  properties, as well as extra header fields that are added
#  to the unwrapped MIME.
$success = $mime->UnwrapSecurity();
if ($success != 1) {
    #  UnwrapSecurity returns _TRUE_ if all signatures were
    #  verified and all parts decrypted.
    print $mime->lastErrorText() . "\n";
    exit;
}

#  The mime.UnwrapExtras property controls whether or not
#  these additional fields are added to the unwrapped MIME:
# 
#  X-NumPartsSigned: 1
#  X-SignaturesValid: yes
#  X-NumPartsEncrypted: 1
#  X-Decrypted: no
# 
#  The X-NumPartsSigned/X-SignaturesValid headers are added
#  if the MIME was signed.
# 
#  The X-NumPartsEncrypted/X-Decrypted headers are added
#  if the MIME was encrypted.
# 

#  If the MIME was signed, get the certificate used for signing.
if ($isSigned == 1) {
    #  The NumSignerCerts property indicates how many certificates
    #  were used for signing.  This example will assume the value is 1.
    #  To get the 1st signer cert, call GetSignerCert with an index of 0:

    $signerCert = $mime->GetSignerCert(0);
    if (!($signerCert eq null )) {
        print "**** Signer Cert: " . $signerCert->subjectCN() . "\r\n";
    }

}

#  If the MIME was encrypted, get the certificate used for encryption:
if ($isEncrypted == 1) {
    #  The NumEncryptCerts property indicates how many certificates
    #  were used for encrypting.  This example will assume the value is 1.
    #  To get the 1st encrypt cert, call GetEncryptCert with an index of 0:

    $encryptCert = $mime->GetEncryptCert(0);
    if (!($encryptCert eq null )) {
        print "**** Encrypt Cert: " . $encryptCert->subjectCN() . "\r\n";
    }

}

#  Display the unwrapped MIME:
print $mime->getMime() . "\r\n";

#  Save the unwrapped MIME to a file:
$mime->SaveMime("unwrappedMime.txt");