(Visual FoxPro) 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

The in.dat file contains the original data that was signed, and can contain text or binary data of any type. The above OpenSSL command does the following:

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

Chilkat ActiveX Downloads

ActiveX for 32-bit and 64-bit Windows

LOCAL loPubKey
LOCAL lnSuccess
LOCAL loBdFileData
LOCAL loBdSig
LOCAL loRsa

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

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.PublicKey')
loPubKey = CreateObject('Chilkat.PublicKey')

* Load the public key from an PEM file:
lnSuccess = loPubKey.LoadFromFile("pubKey.pem")
IF (lnSuccess <> 1) THEN
    ? loPubKey.LastErrorText
    RELEASE loPubKey
    CANCEL
ENDIF

* Load the data of the original file that was signed.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loBdFileData = CreateObject('Chilkat.BinData')
lnSuccess = loBdFileData.LoadFile("in.dat")

* Load the signature.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loBdSig = CreateObject('Chilkat.BinData')
lnSuccess = loBdSig.LoadFile("signature.sig")

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Rsa')
loRsa = CreateObject('Chilkat.Rsa')

* Import the public key into the RSA component:
lnSuccess = loRsa.ImportPublicKeyObj(loPubKey)
IF (lnSuccess <> 1) THEN
    ? loRsa.LastErrorText
    RELEASE loPubKey
    RELEASE loBdFileData
    RELEASE loBdSig
    RELEASE loRsa
    CANCEL
ENDIF

* OpenSSL uses big-endian.
loRsa.LittleEndian = 0

lnSuccess = loRsa.VerifyBd(loBdFileData,"sha256",loBdSig)
IF (lnSuccess <> 1) THEN
    ? loRsa.LastErrorText
    ? "The signature was invalid."
    RELEASE loPubKey
    RELEASE loBdFileData
    RELEASE loBdSig
    RELEASE loRsa
    CANCEL
ENDIF

? "The signature was verified."

RELEASE loPubKey
RELEASE loBdFileData
RELEASE loBdSig
RELEASE loRsa