(Chilkat2-Python) Extract PKCS7 Signature Digest

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

Chilkat2 Python Downloads install with pip pip3 install chilkat2 or download... Python Module for Windows, Linux, Alpine Linux, MacOS, Solaris

import sys
import chilkat2

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

crypt = chilkat2.Crypt2()

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.NumSignerCerts))

# Load the .p7m into memory...
pkcs7Data = chilkat2.BinData()
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 = chilkat2.StringBuilder()
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.EncodingMode = "base64"
i = 0

while i < crypt.NumSignerCerts :
    if (bHaveBase64):
        digest = crypt.Pkcs7ExtractDigest(i,sbBase64.GetAsString())
    else:
        digest = crypt.Pkcs7ExtractDigest(i,pkcs7Data.GetEncoded("base64"))

    if (crypt.LastMethodSuccess != True):
        print(crypt.LastErrorText)
        sys.exit()

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