(Chilkat2-Python) Duplicate openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

Demonstrates how to duplicate this OpenSSL command:

openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

1. Creates a SHA256 digest of the contents of the input file.
2. Verifies the SHA256 digest using the public key.

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

import sys
import chilkat2

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

pubKey = chilkat2.PublicKey()

# Load the public key from an PEM file:
success = pubKey.LoadFromFile("pubKey.pem")
if (success != True):
    print(pubKey.LastErrorText)
    sys.exit()

# Load the data of the original file that was signed.
bdFileData = chilkat2.BinData()
success = bdFileData.LoadFile("in.dat")

# Load the signature.
bdSig = chilkat2.BinData()
success = bdSig.LoadFile("signature.sig")

rsa = chilkat2.Rsa()

# Import the public key into the RSA component:
success = rsa.ImportPublicKeyObj(pubKey)
if (success != True):
    print(rsa.LastErrorText)
    sys.exit()

# OpenSSL uses big-endian.
rsa.LittleEndian = False

success = rsa.VerifyBd(bdFileData,"sha256",bdSig)
if (success != True):
    print(rsa.LastErrorText)
    print("The signature was invalid.")
    sys.exit()

print("The signature was verified.")