(DataFlex) Extract PKCS7 Signature Digest

Demonstrates how to extract a signature digest from a PKCS7 signature.

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

Use ChilkatAx-win32.pkg

Procedure Test
    Handle hoCrypt
    String sP7mFile
    String sOutPath
    Boolean iVerified
    Variant vPkcs7Data
    Handle hoPkcs7Data
    Boolean iSuccess
    Handle hoSbBase64
    String sHexStr
    Boolean iBHaveBase64
    Integer i
    String sDigest
    String sTemp1
    Integer iTemp1
    Boolean bTemp1

    // This example requires the Chilkat Crypt API to have been previously unlocked.
    // See Unlock Chilkat Crypt for sample code.

    Get Create (RefClass(cComChilkatCrypt2)) To hoCrypt
    If (Not(IsComObjectCreated(hoCrypt))) Begin
        Send CreateComObject of hoCrypt
    End

    Move "qa_data/p7m/test.pdf.p7m" To sP7mFile
    Move "qa_output/test.pdf" To sOutPath

    // First let's see if this .p7m signature can be verified, and the original file extracted.
    Get ComVerifyP7M Of hoCrypt sP7mFile sOutPath To iVerified
    If (iVerified <> True) Begin
        Get ComLastErrorText Of hoCrypt To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // How many signers?
    // (The NumSignerCerts property is set whenever a signature is verified.)
    Get ComNumSignerCerts Of hoCrypt To iTemp1
    Showln "Num Signers: " iTemp1

    // Load the .p7m into memory...
    Get Create (RefClass(cComChilkatBinData)) To hoPkcs7Data
    If (Not(IsComObjectCreated(hoPkcs7Data))) Begin
        Send CreateComObject of hoPkcs7Data
    End
    Get ComLoadFile Of hoPkcs7Data sP7mFile To iSuccess

    // Check to see if this .p7m contains the binary bytes, or if it's
    // already base64 encoded.  Get the 1st two bytes.  If the first two 
    // bytes are the us-ascii values "MI", then we have base64.
    Get Create (RefClass(cComChilkatStringBuilder)) To hoSbBase64
    If (Not(IsComObjectCreated(hoSbBase64))) Begin
        Send CreateComObject of hoSbBase64
    End
    Get ComGetEncodedChunk Of hoPkcs7Data 0 2 "hex" To sHexStr
    Get ComAppend Of hoSbBase64 sHexStr To iSuccess

    Move False To iBHaveBase64
    Get ComContentsEqual Of hoSbBase64 "4D49" True To bTemp1
    If (bTemp1 = True) Begin
        Move True To iBHaveBase64
        Send ComClear To hoSbBase64
        Get pvComObject of hoPkcs7Data to vPkcs7Data
        Get ComAppendBd Of hoSbBase64 vPkcs7Data "utf-8" 0 0 To iSuccess
    End

    // Get each signer's signature digest.
    Set ComEncodingMode Of hoCrypt To "base64"
    Move 0 To i

    While (i < (ComNumSignerCerts(hoCrypt)))
        If (iBHaveBase64) Begin
            Get ComGetAsString Of hoSbBase64 To sTemp1
            Get ComPkcs7ExtractDigest Of hoCrypt i sTemp1 To sDigest
        End
        Else Begin
            Get ComGetEncoded Of hoPkcs7Data "base64" To sTemp1
            Get ComPkcs7ExtractDigest Of hoCrypt i sTemp1 To sDigest
        End

        Get ComLastMethodSuccess Of hoCrypt To bTemp1
        If (bTemp1 <> True) Begin
            Get ComLastErrorText Of hoCrypt To sTemp1
            Showln sTemp1
            Procedure_Return
        End

        Showln "Signer " (i + 1) " digest = " sDigest
        Move (i + 1) To i
    Loop



End_Procedure