(CkPython) Duplicate openssl dgst -sha256 -sign private.pem -out sha256.sig in.dat

Demonstrates how to duplicate this OpenSSL command:

openssl dgst -sha256 -sign private.pem -out sha256.sig in.dat

1. Creates a SHA256 digest of the contents of the input file
2. Signs the SHA256 digest using the private key.

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import sys
import chilkat

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

pkey = chilkat.CkPrivateKey()

# Load the private key from an PEM file:
success = pkey.LoadPemFile("private.pem")
if (success != True):
    print(pkey.lastErrorText())
    sys.exit()

rsa = chilkat.CkRsa()

# Import the private key into the RSA component:
success = rsa.ImportPrivateKeyObj(pkey)
if (success != True):
    print(rsa.lastErrorText())
    sys.exit()

# OpenSSL uses big-endian.
rsa.put_LittleEndian(False)

# Load the file to be signed.
bdFileData = chilkat.CkBinData()
success = bdFileData.LoadFile("in.dat")

bdSig = chilkat.CkBinData()
success = rsa.SignBd(bdFileData,"sha256",bdSig)
if (success != True):
    print(rsa.lastErrorText())
    sys.exit()

# Save the binary signature to a file.
success = bdSig.WriteFile("signature.sig")
if (success != True):
    print("Failed to write signature.sig.")
    sys.exit()

print("Success.")