(DataFlex) Duplicating OpenSSL rsautl (creating RSA signatures)

Demonstrates how to duplicate OpenSSL rsautil RSA signatures.

The Chilkat RSA component's methods for creating RSA signatures (SignBytes, SignBytesENC, SignString, and SignStringENC) are very different from OpenSSL's rsautl command. First, we'll explain what Chilkat's signing methods do, and then what OpenSSL's rsautl does. New signing methods have been added to Chilkat RSA to duplicate OpenSSL rsautl: OpenSslSignBytes, OpenSslSignBytesENC, OpenSslSignString, and OpenSslSignStringENC.

Here's what Chilkat's RSA Sign* methods do:
(Note: Chilkat RSA's Sign* methods generate signatures according to RSA Laboratories' "PKCS #1 v2.0: RSA Cryptography Standard".)

1. Input data is hashed using the hashing algorithm specified.
2. The hash is padded using either PKCS1 v1.5 or PKCS1 PSS padding. PKCS v1.5 involves encoding to ASN.1 before padding.
3. The padded hash is finally RSA signed (i.e. modular exponentiation) and the signature is returned.

OpenSSL rsautl is very different. Here's what it does:

1. The input data is not hashed. It must be a small enough amount of data such that it can be padded and signed. PKCS v1.5 padding is always used. The data is not ASN.1 encoded before padding.
2. The PKCS v1.5 padded data is RSA signed and the signature is returned.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

Use ChilkatAx-win32.pkg

Procedure Test
    Handle hoPkey
    Boolean iSuccess
    String sPkeyXml
    Handle hoRsa
    String sStrData
    String sHexSig
    Handle hoPubkey
    String sPubkeyXml
2    Handle hoRsa2
    String sOriginalData
    String sTemp1

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

    Get Create (RefClass(cComChilkatPrivateKey)) To hoPkey
    If (Not(IsComObjectCreated(hoPkey))) Begin
        Send CreateComObject of hoPkey
    End

    // Load the private key from an RSA PEM file:
    Get ComLoadPemFile Of hoPkey "private.pem" To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoPkey To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Get the private key in XML format:
    Get ComGetXml Of hoPkey To sPkeyXml

    Get Create (RefClass(cComChilkatRsa)) To hoRsa
    If (Not(IsComObjectCreated(hoRsa))) Begin
        Send CreateComObject of hoRsa
    End

    // Import the private key into the RSA component:
    Get ComImportPrivateKey Of hoRsa sPkeyXml To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoRsa To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // This example will sign a string, and receive the signature
    // in a hex-encoded string.  Therefore, set the encoding mode
    // to "hex":
    Set ComEncodingMode Of hoRsa To "hex"

    Move "secret" To sStrData

    // Create an OpenSSL style signature:
    Get ComOpenSslSignStringENC Of hoRsa sStrData To sHexSig

    Showln sHexSig

    // Recover the data using the corresponding public key:
    Get Create (RefClass(cComChilkatPublicKey)) To hoPubkey
    If (Not(IsComObjectCreated(hoPubkey))) Begin
        Send CreateComObject of hoPubkey
    End

    // Load the public key from a PEM file:
    Get ComLoadFromFile Of hoPubkey "public.pem" To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoPubkey To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Get the public key in XML format:
    Get ComGetXml Of hoPubkey To sPubkeyXml

    Get Create (RefClass(cComChilkatRsa)) To hoRsa2
    If (Not(IsComObjectCreated(hoRsa2))) Begin
        Send CreateComObject of hoRsa2
    End

    // Import the public key into the RSA component:
    Get ComImportPublicKey Of hoRsa2 sPubkeyXml To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoRsa2 To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Set ComEncodingMode Of hoRsa2 To "hex"

    // Recover the original data.

    Get ComOpenSslVerifyStringENC Of hoRsa2 sHexSig To sOriginalData

    Showln sOriginalData


End_Procedure