(PHP Extension) Decrypt S/MIME and Verify S/MIME Signatures

PHP Extension example to decrypt S/MIME and verify S/MIME signatures. The S/MIME is unwrapped to get the original MIME prior to signing/encrypting.

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.

$mime = new CkMime();

// Load an S/MIME message from a file:
$success = $mime->LoadMimeFile('signedMime.txt');
if ($success != true) {
    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(false);

// 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 != true) {
    // 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 == true) {
    // 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 is a CkCert
    $signerCert = $mime->GetSignerCert(0);
    if ($mime->get_LastMethodSuccess() == true) {
        print '**** Signer Cert: ' . $signerCert->subjectCN() . "\n";

    }

}

// If the MIME was encrypted, get the certificate used for encryption:
if ($isEncrypted == true) {
    // 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 is a CkCert
    $encryptCert = $mime->GetEncryptCert(0);
    if ($mime->get_LastMethodSuccess() == true) {
        print '**** Encrypt Cert: ' . $encryptCert->subjectCN() . "\n";

    }

}

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

// Save the unwrapped MIME to a file:
$success = $mime->SaveMime('unwrappedMime.txt');

?>