(Perl) Extract PKCS7 Signature Digest

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

Chilkat Perl Downloads Perl Module for Windows, MacOS, Linux, Alpine Linux, Solaris

use chilkat();

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

$crypt = chilkat::CkCrypt2->new();

$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 != 1) {
    print $crypt->lastErrorText() . "\r\n";
    exit;
}

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

# Load the .p7m into memory...
$pkcs7Data = chilkat::CkBinData->new();
$pkcs7Data->LoadFile($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 = chilkat::CkStringBuilder->new();
$hexStr = $pkcs7Data->getEncodedChunk(0,2,"hex");
$sbBase64->Append($hexStr);

$bHaveBase64 = 0;
if ($sbBase64->ContentsEqual("4D49",1) == 1) {
    $bHaveBase64 = 1;
    $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() != 1) {
        print $crypt->lastErrorText() . "\r\n";
        exit;
    }

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