(PureBasic) Create XML Digital Signature using Certificate on Smart Card

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Demonstrates how to load a certificate located on a smart card or USB token and then use it for creating an XML digital signature such that the cryptographic signing happens on the smart card.

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IncludeFile "CkXml.pb"
IncludeFile "CkCert.pb"
IncludeFile "CkXmlDSigGen.pb"
IncludeFile "CkScMinidriver.pb"
IncludeFile "CkStringBuilder.pb"

Procedure ChilkatExample()

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

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

    ; Reader names (smart card readers or USB tokens) can be discovered
    ; via List Readers or Find Smart Cards
    readerName.s = "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0"
    success.i = CkScMinidriver::ckAcquireContext(scmd,readerName)
    If success = 0
        Debug CkScMinidriver::ckLastErrorText(scmd)
        CkScMinidriver::ckDispose(scmd)
        ProcedureReturn
    EndIf

    ; If successful, the name of the currently inserted smart card is available:
    Debug "Card name: " + CkScMinidriver::ckCardName(scmd)

    ; If desired, perform regular PIN authentication with the smartcard.
    ; For more details about smart card PIN authentication, see the Smart Card PIN Authentication Example
    retval.i = CkScMinidriver::ckPinAuthenticate(scmd,"user","000000")
    If retval <> 0
        Debug "PIN Authentication failed."
    EndIf

    ; You can find a cerficate using any of the following certificate parts:
    ; "subjectDN" -- The full distinguished name of the cert.
    ; "subjectDN_withTags" -- Same as above, but in a format that includes the subject part tags, such as the "CN=" in "CN=something"
    ; "subjectCN" -- The common name part (CN) of the certificate's subject.
    ; "serial" -- The certificate serial number.
    ; "serial:issuerCN" -- The certificate serial number + the issuer's common name, delimited with a colon char.
    ; These are the same certificate parts that can be retrieved by listing certificates on the smart card (or USB token).
    ; See List Certificates on Smart Card Example
    certPart.s = "subjectCN"
    partValue.s = "PIVKey E42D60A759D39147A26E0AF2FB1183C5"

    ; If the certificate is found, it is loaded into the cert object.
    cert.i = CkCert::ckCreate()
    If cert.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkScMinidriver::ckFindCert(scmd,certPart,partValue,cert)
    If success = 0
        Debug "Failed to find the certificate."
        CkScMinidriver::ckDeleteContext(scmd)
        CkScMinidriver::ckDispose(scmd)
        CkCert::ckDispose(cert)
        ProcedureReturn
    EndIf

    Debug "Successfully loaded the cert object from the smart card / USB token."

    ; Note: When successful, the cert object is internally linked to the ScMinidriver object's authenticated session.
    ; The cert object can now be used to sign or do other cryptographic operations that occur on the smart card / USB token.
    ; If your application calls PinDeauthenticate or DeleteContext, the cert will no longer be able to sign on the smart card
    ; because the smart card ScMinidriver session will no longer be authenticated or deleted.

    ; ------------------------------------------------------------------------------------------------------------
    ; We have the certificate.  Now let's do the XML digital signature..

    ; Create the following XML to be signed:

    ; <?xml version="1.0" encoding="UTF-8" standalone="no" ?>
    ; <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
    ;     <SOAP-ENV:Header>
    ;         <wsse:Security xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" SOAP-ENV:mustUnderstand="1"></wsse:Security>
    ;     </SOAP-ENV:Header>
    ;     <SOAP-ENV:Body xmlns:SOAP-SEC="http://schemas.xmlsoap.org/soap/security/2000-12" SOAP-SEC:id="Body">
    ;         <z:FooBar xmlns:z="http://example.com" />
    ;     </SOAP-ENV:Body>
    ; </SOAP-ENV:Envelope>

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

    CkXml::setCkTag(xml, "SOAP-ENV:Envelope")
    CkXml::ckAddAttribute(xml,"xmlns:SOAP-ENV","http://schemas.xmlsoap.org/soap/envelope/")
    CkXml::ckUpdateAttrAt(xml,"SOAP-ENV:Header|wsse:Security",1,"xmlns:wsse","http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd")
    CkXml::ckUpdateAttrAt(xml,"SOAP-ENV:Header|wsse:Security",1,"SOAP-ENV:mustUnderstand","1")
    CkXml::ckUpdateAttrAt(xml,"SOAP-ENV:Body",1,"xmlns:SOAP-SEC","http://schemas.xmlsoap.org/soap/security/2000-12")
    CkXml::ckUpdateAttrAt(xml,"SOAP-ENV:Body",1,"SOAP-SEC:id","Body")
    CkXml::ckUpdateAttrAt(xml,"SOAP-ENV:Body|z:FooBar",1,"xmlns:z","http://example.com")

    ; Prepare for signing...
    gen.i = CkXmlDSigGen::ckCreate()
    If gen.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; Indicate where the Signature will be inserted.
    CkXmlDSigGen::setCkSigLocation(gen, "SOAP-ENV:Envelope|SOAP-ENV:Header|wsse:Security")

    ; Add a reference to the fragment of the XML to be signed.

    ; Note: "Body" refers to the XML element having an "id" equal to "Body", where "id" is case insensitive
    ; and where any namespace might qualify the attribute.  In this case, the SOAP-ENV:Body fragment is signed
    ; NOT because the tag = "Body", but because it has SOAP-SEC:id="Body"
    CkXmlDSigGen::ckAddSameDocRef(gen,"Body","sha1","EXCL_C14N","","")

    ; (You can read about the SignedInfoPrefixList in the online reference documentation.  It's optional..)
    CkXmlDSigGen::setCkSignedInfoPrefixList(gen, "wsse SOAP-ENV")

    ; Provide the private key for signing via the certificate, and indicate that
    ; we want the base64 of the certificate embedded in the KeyInfo.
    CkXmlDSigGen::setCkKeyInfoType(gen, "X509Data")
    CkXmlDSigGen::setCkX509Type(gen, "Certificate")

    ; Note: Our certificate was loaded from the smartcard and is internally linked to the authenticated ScMinidriver session.
    ; The signing will occur on the smart card using the chosen certificate.
    bUsePrivateKey.i = 1
    success = CkXmlDSigGen::ckSetX509Cert(gen,cert,bUsePrivateKey)
    If success <> 1
        Debug CkXmlDSigGen::ckLastErrorText(gen)
        CkScMinidriver::ckDispose(scmd)
        CkCert::ckDispose(cert)
        CkXml::ckDispose(xml)
        CkXmlDSigGen::ckDispose(gen)
        ProcedureReturn
    EndIf

    ; Everything's specified.  Now create and insert the Signature
    sbXml.i = CkStringBuilder::ckCreate()
    If sbXml.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkXml::ckGetXmlSb(xml,sbXml)
    success = CkXmlDSigGen::ckCreateXmlDSigSb(gen,sbXml)
    If success <> 1
        Debug CkXmlDSigGen::ckLastErrorText(gen)
        CkScMinidriver::ckDispose(scmd)
        CkCert::ckDispose(cert)
        CkXml::ckDispose(xml)
        CkXmlDSigGen::ckDispose(gen)
        CkStringBuilder::ckDispose(sbXml)
        ProcedureReturn
    EndIf

    ; Examine the XML with the digital signature inserted
    Debug CkStringBuilder::ckGetAsString(sbXml)

    ; ------------------------------------------------------------------------------------------------------------
    ; Cleanup our ScMinidriver session...

    ; When finished with operations that required authentication, you may if you wish, deauthenticate the session.
    success = CkScMinidriver::ckPinDeauthenticate(scmd,"user")
    If success = 0
        Debug CkScMinidriver::ckLastErrorText(scmd)
    EndIf

    ; Delete the context when finished with the card.
    success = CkScMinidriver::ckDeleteContext(scmd)
    If success = 0
        Debug CkScMinidriver::ckLastErrorText(scmd)
    EndIf



    CkScMinidriver::ckDispose(scmd)
    CkCert::ckDispose(cert)
    CkXml::ckDispose(xml)
    CkXmlDSigGen::ckDispose(gen)
    CkStringBuilder::ckDispose(sbXml)


    ProcedureReturn
EndProcedure