(Ruby) Extract PKCS7 Signature Digest

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

Chilkat Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require '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 != true)
    print crypt.lastErrorText() + "\n";
    exit
end

# How many signers?
# (The NumSignerCerts property is set whenever a signature is verified.)
print "Num Signers: " + crypt.get_NumSignerCerts().to_s() + "\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 = false
if (sbBase64.ContentsEqual("4D49",true) == true)
    bHaveBase64 = true
    sbBase64.Clear()
    sbBase64.AppendBd(pkcs7Data,"utf-8",0,0)
end

# 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"))
    end

    if (crypt.get_LastMethodSuccess() != true)
        print crypt.lastErrorText() + "\n";
        exit
    end

    print "Signer " + (i + 1).to_s() + " digest = " + digest + "\n";
    i = i + 1
end