(Lianja) Create XML Signature with External XML Reference

Demonstrates how to create an XML digital signature where the referenced data is external. In this case, the data is an XML file located at the following URL: https://www.chilkatsoft.com/data/helloWorld.xml

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

// This example inserts an XML signature in the following XML:

// <?xml version="1.0" encoding="UTF-8" standalone="no"?>
// <abc>
//   <xyz>
// 	<name>helloWorld.xml</name>
// 	<url>https://www.chilkatsoft.com/data/helloWorld.xml</url>
//   </xyz>
// </abc>

// Build the above XML to be signed.
loXml = createobject("CkXml")
loXml.Tag = "abc"
loXml.UpdateChildContent("xyz|name","helloWorld.xml")
loXml.UpdateChildContent("xyz|url","https://www.chilkatsoft.com/data/helloWorld.xml")

loCert = createobject("CkCert")

llSuccess = loCert.LoadPfxFile("qa_data/pfx/test_secret.pfx","secret")
if (llSuccess = .F.) then
    ? loCert.LastErrorText
    release loXml
    release loCert
    return
endif

loGen = createobject("CkXmlDSigGen")

// Indicate the location within the XML the Signature will be inserted.
loGen.SigLocation = "abc|xyz"

// Get the content of the XML data to be referenced.
loHttp = createobject("CkHttp")
loSbExternalXml = createobject("CkStringBuilder")
llSuccess = loHttp.QuickGetSb("https://www.chilkatsoft.com/data/helloWorld.xml",loSbExternalXml)
if (llSuccess = .F.) then
    ? loHttp.LastErrorText
    release loXml
    release loCert
    release loGen
    release loHttp
    release loSbExternalXml
    return
endif

llSuccess = loGen.AddExternalXmlRef("https://www.chilkatsoft.com/data/helloWorld.xml",loSbExternalXml,"sha256","EXCL_C14N","")
if (llSuccess = .F.) then
    ? loGen.LastErrorText
    release loXml
    release loCert
    release loGen
    release loHttp
    release loSbExternalXml
    return
endif

// Provide the private key for signing via the certificate, and indicate that
// we want the base64 of the certificate embedded in the KeyInfo.
loGen.KeyInfoType = "X509Data"
loGen.X509Type = "Certificate"

llBUsePrivateKey = .T.
llSuccess = loGen.SetX509Cert(loCert,llBUsePrivateKey)
if (llSuccess <> .T.) then
    ? loGen.LastErrorText
    release loXml
    release loCert
    release loGen
    release loHttp
    release loSbExternalXml
    return
endif

// Indicate we want an indented signature for readability.
// This can be removed after debugging is finished..
loGen.Behaviors = "IndentedSignature"

// Now create and insert the Signature
loSbXml = createobject("CkStringBuilder")
loXml.GetXmlSb(loSbXml)
llSuccess = loGen.CreateXmlDSigSb(loSbXml)
if (llSuccess <> .T.) then
    ? loGen.LastErrorText
    release loXml
    release loCert
    release loGen
    release loHttp
    release loSbExternalXml
    release loSbXml
    return
endif

// Examine the XML with the digital signature inserted
? loSbXml.GetAsString()

// Here is the output:

// <?xml version="1.0" encoding="utf-8"?>
// <abc>
//     <xyz>
//         <name>helloWorld.xml</name>
//         <url>https://www.chilkatsoft.com/data/helloWorld.xml</url>
//     <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#rsa-sha256"/>
//     <ds:Reference URI="https://www.chilkatsoft.com/data/helloWorld.xml">
//       <ds:Transforms>
//         <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
//       </ds:Transforms>
//       <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
//       <ds:DigestValue>H/s775OZhel6wdBhe02l4LK6m0lkplOisKxAbVwWxp0=</ds:DigestValue>
//     </ds:Reference>
//   </ds:SignedInfo>
//   <ds:SignatureValue>UruwnBqh..Ll4IzUA==</ds:SignatureValue>
//   <ds:KeyInfo>
//     <ds:X509Data>
//       <ds:X509Certificate>MIIHAz...nUZWCaDE=</ds:X509Certificate>
//     </ds:X509Data>
//   </ds:KeyInfo>
// </ds:Signature></xyz>
// </abc>

// Let's verify the signature...
loVerifier = createobject("CkXmlDSig")
llSuccess = loVerifier.LoadSignatureSb(loSbXml)
if (llSuccess <> .T.) then
    ? loVerifier.LastErrorText
    release loXml
    release loCert
    release loGen
    release loHttp
    release loSbExternalXml
    release loSbXml
    release loVerifier
    return
endif

// Let's examine the external references, and fetch the data for each..
loSbExternalData = createobject("CkStringBuilder")
lnNumRefs = loVerifier.NumReferences
i = 0
do while i < lnNumRefs
    llBExternal = loVerifier.IsReferenceExternal(i)
    if (llBExternal = .T.) then
        lcUri = loVerifier.ReferenceUri(i)

        // We're assuming the URI is an https:// or http:// URL...
        // Let's also assume we know that the referenced data is text and we want the utf-8 byte representation.
        loSbExternalData.Clear()
        llSuccess = loHttp.QuickGetSb(lcUri,loSbExternalData)
        if (llSuccess = .F.) then
            ? loHttp.LastErrorText
            release loXml
            release loCert
            release loGen
            release loHttp
            release loSbExternalXml
            release loSbXml
            release loVerifier
            release loSbExternalData
            return
        endif

        // Because the referenced external data was explicitly XML, it was the canonicalized XML that was digested.
        // We need to canonicalize the XML in the same way as when signed.
        lcCanonXml = loVerifier.CanonicalizeXml(loSbExternalData.GetAsString(),"EXCL_C14N",.F.)
        loSbExternalData.SetString(lcCanonXml)

        llSuccess = loVerifier.SetRefDataSb(i,loSbExternalData,"utf-8")
        if (llSuccess = .F.) then
            ? loVerifier.LastErrorText
            release loXml
            release loCert
            release loGen
            release loHttp
            release loSbExternalXml
            release loSbXml
            release loVerifier
            release loSbExternalData
            return
        endif

    endif

    i = i + 1
enddo

// Now that we have the external data available, we can verify the reference digest(s) and the signature.
llBVerified = loVerifier.VerifySignature(.T.)
if (llBVerified <> .T.) then
    ? loVerifier.LastErrorText
    release loXml
    release loCert
    release loGen
    release loHttp
    release loSbExternalXml
    release loSbXml
    release loVerifier
    release loSbExternalData
    return
endif

? "Signature verified!"


release loXml
release loCert
release loGen
release loHttp
release loSbExternalXml
release loSbXml
release loVerifier
release loSbExternalData