(CkPython) Extract PKCS7 Signature Digest

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

Chilkat Python Downloads install with pip pip3 install chilkat or download... Python Module for Windows, MacOS, Linux, Alpine Linux, Solaris

import sys
import chilkat

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

crypt = chilkat.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())
    sys.exit()

# How many signers?
# (The NumSignerCerts property is set whenever a signature is verified.)
print("Num Signers: " + str(crypt.get_NumSignerCerts()))

# Load the .p7m into memory...
pkcs7Data = chilkat.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 = chilkat.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())
        sys.exit()

    print("Signer " + str(i + 1) + " digest = " + digest)
    i = i + 1