(PureBasic) PKCS11 Sign PDF using Certificate and Private Key on Smart Card / USB Token

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Sample code showing how to use PKCS11 to sign a PDF with a certificate and private key stored on a smart card or USB token.

Note: This example requires Chilkat v9.5.0.88 or later.

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IncludeFile "CkPkcs11.pb"
IncludeFile "CkCert.pb"
IncludeFile "CkJsonObject.pb"
IncludeFile "CkPdf.pb"

Procedure ChilkatExample()

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

    ; Note: Chilkat's PKCS11 implementation runs on Windows, Linux, Mac OS X, and other supported operating systems.

    pkcs11.i = CkPkcs11::ckCreate()
    If pkcs11.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; This example is tested on Windows using a Giesecke and Devrient Sm@rtCafe Expert 3.2 smart card.
    CkPkcs11::setCkSharedLibPath(pkcs11, "aetpkss1.dll")

    success.i = CkPkcs11::ckInitialize(pkcs11)
    If success = 0
        Debug CkPkcs11::ckLastErrorText(pkcs11)
        CkPkcs11::ckDispose(pkcs11)
        ProcedureReturn
    EndIf

    ; We need to call Discover to get the slot ID.
    onlyTokensPresent.i = 1
    jsonPkcs11.i = CkJsonObject::ckCreate()
    If jsonPkcs11.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkPkcs11::ckDiscover(pkcs11,onlyTokensPresent,jsonPkcs11)
    If success = 0
        Debug CkPkcs11::ckLastErrorText(pkcs11)
        CkPkcs11::ckDispose(pkcs11)
        CkJsonObject::ckDispose(jsonPkcs11)
        ProcedureReturn
    EndIf

    ; Make sure we have at least one slot.
    If CkJsonObject::ckSizeOfArray(jsonPkcs11,"slot") <= 0
        Debug "No occuplied slots."
        CkPkcs11::ckDispose(pkcs11)
        CkJsonObject::ckDispose(jsonPkcs11)
        ProcedureReturn
    EndIf

    ; Get the ID of the 1st slot
    slotID.i = CkJsonObject::ckIntOf(jsonPkcs11,"slot[0].id")

    ; Open a session.
    readWrite.i = 1
    success = CkPkcs11::ckOpenSession(pkcs11,slotID,readWrite)
    If success = 0
        Debug CkPkcs11::ckLastErrorText(pkcs11)
        CkPkcs11::ckDispose(pkcs11)
        CkJsonObject::ckDispose(jsonPkcs11)
        ProcedureReturn
    EndIf

    ; Make it an authenticated session by calling Login.
    userType.i = 1
    ; Make sure to use the correct PIN for your smart card..
    pin.s = "0000"
    success = CkPkcs11::ckLogin(pkcs11,userType,pin)
    If success = 0
        Debug CkPkcs11::ckLastErrorText(pkcs11)
        success = CkPkcs11::ckCloseSession(pkcs11)
        CkPkcs11::ckDispose(pkcs11)
        CkJsonObject::ckDispose(jsonPkcs11)
        ProcedureReturn
    EndIf

    ; Get the certificate (on the smart card) that has a private key.
    cert.i = CkCert::ckCreate()
    If cert.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkPkcs11::ckFindCert(pkcs11,"privateKey","",cert)
    If success = 1
        Debug "Cert with private key: " + CkCert::ckSubjectCN(cert)
    Else
        Debug "No certificates having a private key were found."
        success = CkPkcs11::ckCloseSession(pkcs11)
        CkPkcs11::ckDispose(pkcs11)
        CkJsonObject::ckDispose(jsonPkcs11)
        CkCert::ckDispose(cert)
        ProcedureReturn
    EndIf

    ; --------------------------------------------------------------------------
    ; At this point, we have the cert to be used for signing.
    ; Our PDF signing code is the same as for a cert obtained from any other source..

    pdf.i = CkPdf::ckCreate()
    If pdf.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; Load a PDF to be signed.
    success = CkPdf::ckLoadFile(pdf,"qa_data/pdf/hello.pdf")
    If success = 0
        Debug CkPdf::ckLastErrorText(pdf)
        success = CkPkcs11::ckCloseSession(pkcs11)
        CkPkcs11::ckDispose(pkcs11)
        CkJsonObject::ckDispose(jsonPkcs11)
        CkCert::ckDispose(cert)
        CkPdf::ckDispose(pdf)
        ProcedureReturn
    EndIf

    json.i = CkJsonObject::ckCreate()
    If json.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkJsonObject::ckUpdateInt(json,"page",1)
    CkJsonObject::ckUpdateString(json,"appearance.y","top")
    CkJsonObject::ckUpdateString(json,"appearance.x","left")
    CkJsonObject::ckUpdateString(json,"appearance.fontScale","10.0")
    CkJsonObject::ckUpdateString(json,"signingAlgorithm","pss")
    CkJsonObject::ckUpdateString(json,"hashAlgorithm","sha256")

    i.i = 0
    CkJsonObject::setCkI(json, i)
    CkJsonObject::ckUpdateString(json,"appearance.text[i]","Digitaly signed by: Xyz Widgets, Inc.")
    i = i + 1
    CkJsonObject::setCkI(json, i)
    CkJsonObject::ckUpdateString(json,"appearance.text[i]","current_dt")
    i = i + 1
    CkJsonObject::setCkI(json, i)
    CkJsonObject::ckUpdateString(json,"appearance.text[i]","blah blah blah")

    ; The certificate is internally linked to the Pkcs11 object, which is currently in an authenticated session.
    success = CkPdf::ckSetSigningCert(pdf,cert)

    success = CkPdf::ckSignPdf(pdf,json,"qa_output/out.pdf")
    If success = 0
        Debug CkPdf::ckLastErrorText(pdf)
        success = CkPkcs11::ckCloseSession(pkcs11)
        CkPkcs11::ckDispose(pkcs11)
        CkJsonObject::ckDispose(jsonPkcs11)
        CkCert::ckDispose(cert)
        CkPdf::ckDispose(pdf)
        CkJsonObject::ckDispose(json)
        ProcedureReturn
    EndIf

    ; --------------------------------------------------------------------------

    ; Revert to an unauthenticated session by calling Logout.
    success = CkPkcs11::ckLogout(pkcs11)
    If success = 0
        Debug CkPkcs11::ckLastErrorText(pkcs11)
        success = CkPkcs11::ckCloseSession(pkcs11)
        CkPkcs11::ckDispose(pkcs11)
        CkJsonObject::ckDispose(jsonPkcs11)
        CkCert::ckDispose(cert)
        CkPdf::ckDispose(pdf)
        CkJsonObject::ckDispose(json)
        ProcedureReturn
    EndIf

    ; When finished, close the session.
    ; It is important to close the session (memory leaks will occur if the session is not properly closed).
    success = CkPkcs11::ckCloseSession(pkcs11)
    If success = 0
        Debug CkPkcs11::ckLastErrorText(pkcs11)
        CkPkcs11::ckDispose(pkcs11)
        CkJsonObject::ckDispose(jsonPkcs11)
        CkCert::ckDispose(cert)
        CkPdf::ckDispose(pdf)
        CkJsonObject::ckDispose(json)
        ProcedureReturn
    EndIf

    Debug "Success."


    CkPkcs11::ckDispose(pkcs11)
    CkJsonObject::ckDispose(jsonPkcs11)
    CkCert::ckDispose(cert)
    CkPdf::ckDispose(pdf)
    CkJsonObject::ckDispose(json)


    ProcedureReturn
EndProcedure