(PHP Extension) Extract PKCS7 Signature Digest

Demonstrates how to extract a signature digest from a PKCS7 signature.

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 Crypt API to have been previously unlocked.
// See Unlock Chilkat Crypt for sample code.

$crypt = new CkCrypt2();

$p7mFile = 'qa_data/p7m/test.pdf.p7m';
$outPath = 'qa_output/test.pdf';

// First let's see if this .p7m signature can be verified, and the original file extracted.
$verified = $crypt->VerifyP7M($p7mFile,$outPath);
if ($verified != true) {
    print $crypt->lastErrorText() . "\n";
    exit;
}

// How many signers?
// (The NumSignerCerts property is set whenever a signature is verified.)
print 'Num Signers: ' . $crypt->get_NumSignerCerts() . "\n";

// Load the .p7m into memory...
$pkcs7Data = new CkBinData();
$pkcs7Data->LoadFile($p7mFile);

// Check to see if this .p7m contains the binary bytes, or if it's
// already base64 encoded.  Get the 1st two bytes.  If the first two 
// bytes are the us-ascii values "MI", then we have base64.
$sbBase64 = new CkStringBuilder();
$hexStr = $pkcs7Data->getEncodedChunk(0,2,'hex');
$sbBase64->Append($hexStr);

$bHaveBase64 = false;
if ($sbBase64->ContentsEqual('4D49',true) == true) {
    $bHaveBase64 = true;
    $sbBase64->Clear();
    $sbBase64->AppendBd($pkcs7Data,'utf-8',0,0);
}

// Get each signer's signature digest.
$crypt->put_EncodingMode('base64');
$i = 0;

while ($i < $crypt->get_NumSignerCerts()) {
    if ($bHaveBase64) {
        $digest = $crypt->pkcs7ExtractDigest($i,$sbBase64->getAsString());
    }
    else {
        $digest = $crypt->pkcs7ExtractDigest($i,$pkcs7Data->getEncoded('base64'));
    }

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

    print 'Signer ' . ($i + 1) . ' digest = ' . $digest . "\n";
    $i = $i + 1;
}


?>