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RSASSA-PSS Sign String to Create Base64 PCKS7 Signature

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Signs a string to create a PKCS7 signature in the base64 encoding. The signature algorithm is RSASSA-PSS with SHA256. AutoIt

Local $bSuccess = False

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

$oCrypt = ObjCreate("Chilkat.Crypt2")

; Get a digital certificate with private key from a .pfx
; (Chilkat has many different ways to provide a cert + private key for siging.
; Using a PFX is just one possible option.)
$oPfx = ObjCreate("Chilkat.Pfx")
$bSuccess = $oPfx.LoadPfxFile("qa_data/rsassa-pss/privatekey.pfx","PFX_PASSWORD")
If ($bSuccess = False) Then
    ConsoleWrite($oPfx.LastErrorText & @CRLF)
    Exit
EndIf

; Get the certificate to be used for signing.
; (The typical case for a PFX is that it contains a cert with an associated private key,
; as well as other certificates in the chain of authentication.  The cert with the private
; key should be in the first position at index 0.)

$oCert = ObjCreate("Chilkat.Cert")
$bSuccess = $oPfx.CertAt(0,$oCert)
If ($bSuccess = False) Then
    ConsoleWrite($oPfx.LastErrorText & @CRLF)
    Exit
EndIf

$oCrypt.SetSigningCert($oCert)

; Indicate that RSASSA-PSS with SHA256 should be used.
$oCrypt.SigningAlg = "pss"
$oCrypt.HashAlgorithm = "sha256"

$oCrypt.EncodingMode = "base64"

; Sign a string and return the base64 PKCS7 detached signature
Local $sOriginalText = "This is a test"
Local $sPkcs7sig = $oCrypt.SignStringENC($sOriginalText)
ConsoleWrite("Detached Signature:" & @CRLF)
ConsoleWrite($sPkcs7sig & @CRLF)

; This signature looks like this:
; MIIG5wYJKoZIhvcNAQcCoIIG2DCCBtQCAQExDzANBgl .. YToLqEwTdU87ox5g7rvw==

; The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
; then copy-and-paste the Base64 signature into the form and decode..

; The signature can be verified against the original data like this:
$bSuccess = $oCrypt.VerifyStringENC($sOriginalText,$sPkcs7sig)
ConsoleWrite("Signature verified: " & $bSuccess & @CRLF)
$bSuccess = $oCrypt.VerifyStringENC("Not the original text",$sPkcs7sig)
ConsoleWrite("Signature verified: " & $bSuccess & @CRLF)

; Now we'll create an opaque signature (the opposite of a detached signature). 
; An opaque signature is a PKCS7 message that contains both the original data and
; the signature.  The verification process extracts the original data.
Local $sOpaqueSig = $oCrypt.OpaqueSignStringENC($sOriginalText)
ConsoleWrite("Opaque Signature:" & @CRLF)
ConsoleWrite($sOpaqueSig & @CRLF)

; The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
; then copy-and-paste the Base64 signature into the form and decode..

; We can verify and extract the original data:
Local $sOrigTxt = $oCrypt.OpaqueVerifyStringENC($sOpaqueSig)
If ($oCrypt.LastMethodSuccess <> True) Then
    ConsoleWrite("Signature verification failed." & @CRLF)
    ConsoleWrite($oCrypt.LastErrorText & @CRLF)
    Exit
EndIf

ConsoleWrite("Signature verified." & @CRLF)
ConsoleWrite("Extracted text:" & $sOrigTxt & @CRLF)