(PureBasic) Create Enveloping XML Digital Signature

This example creates an enveloping digital signature.
An enveloping signature is where the signed data is contained within the Signature within an Object element.
This example signs non-XML text data where the XML signature constitutes the entire output.

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IncludeFile "CkBinData.pb"
IncludeFile "CkPrivateKey.pb"
IncludeFile "CkHttp.pb"
IncludeFile "CkXmlDSigGen.pb"
IncludeFile "CkZip.pb"
IncludeFile "CkStringBuilder.pb"
IncludeFile "CkZipEntry.pb"

Procedure ChilkatExample()

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

    ; Let's use the ECDSA private key at https://www.chilkatsoft.com/exampleData/secp256r1-key.zip
    ; for signing.
    http.i = CkHttp::ckCreate()
    If http.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

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

    keyUrl.s = "https://www.chilkatsoft.com/exampleData/secp256r1-key.zip"

    success.i = CkHttp::ckQuickGetBd(http,keyUrl,zipFile)
    If success <> 1
        Debug CkHttp::ckLastErrorText(http)
        CkHttp::ckDispose(http)
        CkBinData::ckDispose(zipFile)
        ProcedureReturn
    EndIf

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

    success = CkZip::ckOpenBd(zip,zipFile)
    zipEntry.i = CkZip::ckFirstMatchingEntry(zip,"*.pem")
    ecKey.i = CkPrivateKey::ckCreate()
    If ecKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkPrivateKey::ckLoadPem(ecKey,CkZipEntry::ckUnzipToString(zipEntry,0,"utf-8"))
    If success <> 1
        Debug CkPrivateKey::ckLastErrorText(ecKey)
        CkZipEntry::ckDispose(zipEntry)

        CkHttp::ckDispose(http)
        CkBinData::ckDispose(zipFile)
        CkZip::ckDispose(zip)
        CkPrivateKey::ckDispose(ecKey)
        ProcedureReturn
    EndIf

    CkZipEntry::ckDispose(zipEntry)

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

    ; Provide the ECDSA key to the XML Digital Signature generator
    CkXmlDSigGen::ckSetPrivateKey(gen,ecKey)

    ; Add an enveloped reference to the content to be signed.
    sbContent.i = CkStringBuilder::ckCreate()
    If sbContent.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkStringBuilder::ckAppend(sbContent,"This is the content that is signed.")
    CkXmlDSigGen::ckAddEnvelopedRef(gen,"abc123",sbContent,"sha256","C14N","")

    ; Generate the XML digital signature.
    ; Notice that in other examples, the sbXml passed to CreateXmlDSigSb
    ; already contains XML, and the XML signature is inserted at the location
    ; specified by the SigLocation property.  In this case, both SigLocation
    ; and sbXml are empty.  The result is that sbXml will contain just the Signature.
    sbXml.i = CkStringBuilder::ckCreate()
    If sbXml.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkXmlDSigGen::ckCreateXmlDSigSb(gen,sbXml)
    If success <> 1
        Debug CkXmlDSigGen::ckLastErrorText(gen)
        CkHttp::ckDispose(http)
        CkBinData::ckDispose(zipFile)
        CkZip::ckDispose(zip)
        CkPrivateKey::ckDispose(ecKey)
        CkXmlDSigGen::ckDispose(gen)
        CkStringBuilder::ckDispose(sbContent)
        CkStringBuilder::ckDispose(sbXml)
        ProcedureReturn
    EndIf

    ; Examine the enveloped signature, where the data is contained within the XML Signature
    Debug CkStringBuilder::ckGetAsString(sbXml)

    ; The Signature returned is compact and in a single line, like this:
    ; <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#"><ds:SignedInfo><ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/><ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256"/><ds:Reference URI="#abc123"><ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/><ds:DigestValue>tEVrbXXjeTXjF3tIojul4/sgeEGN49E1dxr/GMs8GNE=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>/pILUshwrzgdGc4bPgp85TDfbUiM9pn8EIPNRVWKuoVEtPsv4XRthUrv9aDDvajmyl2okLwTakANgtaxO1ULMw==</ds:SignatureValue><ds:KeyInfo><ds:KeyValue><ds:ECKeyValue xmlns="http://www.w3.org/2009/xmldsig11#"><ds:NamedCurve URI="urn:oid:1.2.840.10045.3.1.7" /><ds:PublicKey>BOVKaiLPKEDChhkA64UEBOXTv/VFHnhrUPN+bXqCvEl7rroAYpH5tKzbiGTtMSlp4JO9Pxg44zeX7EoWDvOrpD0=</ds:PublicKey></ds:ECKeyValue></ds:KeyValue></ds:KeyInfo><ds:Object Id="abc123">This is the content that is signed.</ds:Object></ds:Signature>

    ; XML pretty-printed, the signature is as follows, but pretty-printing introductes whitespace that breaks the signature..

    ; <?xml version="1.0" encoding="utf-8" ?>
    ; <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
    ;     <ds:SignedInfo>
    ;         <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
    ;         <ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256" />
    ;         <ds:Reference URI="#abc123">
    ;             <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256" />
    ;             <ds:DigestValue>tEVrbXXjeTXjF3tIojul4/sgeEGN49E1dxr/GMs8GNE=</ds:DigestValue>
    ;         </ds:Reference>
    ;     </ds:SignedInfo>
    ;     <ds:SignatureValue>/pILUshwrzgdGc4bPgp85TDfbUiM9pn8EIPNRVWKuoVEtPsv4XRthUrv9aDDvajmyl2okLwTakANgtaxO1ULMw==</ds:SignatureValue>
    ;     <ds:KeyInfo>
    ;         <ds:KeyValue>
    ;             <ds:ECKeyValue xmlns="http://www.w3.org/2009/xmldsig11#">
    ;                 <ds:NamedCurve URI="urn:oid:1.2.840.10045.3.1.7" />
    ;                 <ds:PublicKey>BOVKaiLPKEDChhkA64UEBOXTv/VFHnhrUPN+bXqCvEl7rroAYpH5tKzbiGTtMSlp4JO9Pxg44zeX7EoWDvOrpD0=</ds:PublicKey>
    ;             </ds:ECKeyValue>
    ;         </ds:KeyValue>
    ;     </ds:KeyInfo>
    ;     <ds:Object Id="abc123">This is the content that is signed.</ds:Object>
    ; </ds:Signature>
    ; 


    CkHttp::ckDispose(http)
    CkBinData::ckDispose(zipFile)
    CkZip::ckDispose(zip)
    CkPrivateKey::ckDispose(ecKey)
    CkXmlDSigGen::ckDispose(gen)
    CkStringBuilder::ckDispose(sbContent)
    CkStringBuilder::ckDispose(sbXml)


    ProcedureReturn
EndProcedure