DataFlex

Duplicating OpenSSL rsautl (creating RSA signatures)

See more RSA Examples

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.

The new OpenSsl* methods are designed to duplicate OpenSSL's rsautil signature functionality. DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Variant vPrivKey
    Handle hoPrivKey
    Handle hoRsa
    String sStrData
    Variant vBd
    Handle hoBd
    String sHexSig
    Variant vPubKey
    Handle hoPubKey
2    Handle hoRsa2
    Variant vBd2
    Handle hoBd2
    String sOriginalData
    String sTemp1

    Move False To iSuccess

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

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

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

    Get Create (RefClass(cComChilkatRsa)) To hoRsa
    If (Not(IsComObjectCreated(hoRsa))) Begin
        Send CreateComObject of hoRsa
    End
    Get pvComObject of hoPrivKey to vPrivKey
    Get ComUsePrivateKey Of hoRsa vPrivKey To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoRsa To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Move "secret" To sStrData
    Get Create (RefClass(cComChilkatBinData)) To hoBd
    If (Not(IsComObjectCreated(hoBd))) Begin
        Send CreateComObject of hoBd
    End
    Get ComAppendString Of hoBd sStrData "utf-8" To iSuccess

    Get pvComObject of hoBd to vBd
    Get ComSignRawBd Of hoRsa vBd To iSuccess
    Get ComGetEncoded Of hoBd "hex" 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 = False) Begin
        Get ComLastErrorText Of hoPubKey To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get Create (RefClass(cComChilkatRsa)) To hoRsa2
    If (Not(IsComObjectCreated(hoRsa2))) Begin
        Send CreateComObject of hoRsa2
    End
    Get pvComObject of hoPubKey to vPubKey
    Get ComUsePublicKey Of hoRsa2 vPubKey To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoRsa2 To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get Create (RefClass(cComChilkatBinData)) To hoBd2
    If (Not(IsComObjectCreated(hoBd2))) Begin
        Send CreateComObject of hoBd2
    End
    Get ComAppendEncoded Of hoBd2 sHexSig "hex" To iSuccess

    // Recover the original data.
    Get pvComObject of hoBd2 to vBd2
    Get ComVerifyRawBd Of hoRsa2 vBd2 To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoRsa2 To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get ComGetString Of hoBd2 "utf-8" To sOriginalData
    Showln sOriginalData


End_Procedure