(Visual FoxPro) 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

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

LOCAL loXml
LOCAL loCert
LOCAL lnSuccess
LOCAL loGen
LOCAL loHttp
LOCAL loSbExternalXml
LOCAL lnBUsePrivateKey
LOCAL loSbXml
LOCAL loVerifier
LOCAL loSbExternalData
LOCAL lnNumRefs
LOCAL i
LOCAL lnBExternal
LOCAL lcUri
LOCAL lcCanonXml
LOCAL lnBVerified

* 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.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Xml')
loXml = CreateObject('Chilkat.Xml')
loXml.Tag = "abc"
loXml.UpdateChildContent("xyz|name","helloWorld.xml")
loXml.UpdateChildContent("xyz|url","https://www.chilkatsoft.com/data/helloWorld.xml")

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Cert')
loCert = CreateObject('Chilkat.Cert')

lnSuccess = loCert.LoadPfxFile("qa_data/pfx/test_secret.pfx","secret")
IF (lnSuccess = 0) THEN
    ? loCert.LastErrorText
    RELEASE loXml
    RELEASE loCert
    CANCEL
ENDIF

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.XmlDSigGen')
loGen = CreateObject('Chilkat.XmlDSigGen')

* 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.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Http')
loHttp = CreateObject('Chilkat.Http')
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.StringBuilder')
loSbExternalXml = CreateObject('Chilkat.StringBuilder')
lnSuccess = loHttp.QuickGetSb("https://www.chilkatsoft.com/data/helloWorld.xml",loSbExternalXml)
IF (lnSuccess = 0) THEN
    ? loHttp.LastErrorText
    RELEASE loXml
    RELEASE loCert
    RELEASE loGen
    RELEASE loHttp
    RELEASE loSbExternalXml
    CANCEL
ENDIF

lnSuccess = loGen.AddExternalXmlRef("https://www.chilkatsoft.com/data/helloWorld.xml",loSbExternalXml,"sha256","EXCL_C14N","")
IF (lnSuccess = 0) THEN
    ? loGen.LastErrorText
    RELEASE loXml
    RELEASE loCert
    RELEASE loGen
    RELEASE loHttp
    RELEASE loSbExternalXml
    CANCEL
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"

lnBUsePrivateKey = 1
lnSuccess = loGen.SetX509Cert(loCert,lnBUsePrivateKey)
IF (lnSuccess <> 1) THEN
    ? loGen.LastErrorText
    RELEASE loXml
    RELEASE loCert
    RELEASE loGen
    RELEASE loHttp
    RELEASE loSbExternalXml
    CANCEL
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
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.StringBuilder')
loSbXml = CreateObject('Chilkat.StringBuilder')
loXml.GetXmlSb(loSbXml)
lnSuccess = loGen.CreateXmlDSigSb(loSbXml)
IF (lnSuccess <> 1) THEN
    ? loGen.LastErrorText
    RELEASE loXml
    RELEASE loCert
    RELEASE loGen
    RELEASE loHttp
    RELEASE loSbExternalXml
    RELEASE loSbXml
    CANCEL
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...
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.XmlDSig')
loVerifier = CreateObject('Chilkat.XmlDSig')
lnSuccess = loVerifier.LoadSignatureSb(loSbXml)
IF (lnSuccess <> 1) THEN
    ? loVerifier.LastErrorText
    RELEASE loXml
    RELEASE loCert
    RELEASE loGen
    RELEASE loHttp
    RELEASE loSbExternalXml
    RELEASE loSbXml
    RELEASE loVerifier
    CANCEL
ENDIF

* Let's examine the external references, and fetch the data for each..
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.StringBuilder')
loSbExternalData = CreateObject('Chilkat.StringBuilder')
lnNumRefs = loVerifier.NumReferences
i = 0
DO WHILE i < lnNumRefs
    lnBExternal = loVerifier.IsReferenceExternal(i)
    IF (lnBExternal = 1) 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()
        lnSuccess = loHttp.QuickGetSb(lcUri,loSbExternalData)
        IF (lnSuccess = 0) THEN
            ? loHttp.LastErrorText
            RELEASE loXml
            RELEASE loCert
            RELEASE loGen
            RELEASE loHttp
            RELEASE loSbExternalXml
            RELEASE loSbXml
            RELEASE loVerifier
            RELEASE loSbExternalData
            CANCEL
        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",0)
        loSbExternalData.SetString(lcCanonXml)

        lnSuccess = loVerifier.SetRefDataSb(i,loSbExternalData,"utf-8")
        IF (lnSuccess = 0) THEN
            ? loVerifier.LastErrorText
            RELEASE loXml
            RELEASE loCert
            RELEASE loGen
            RELEASE loHttp
            RELEASE loSbExternalXml
            RELEASE loSbXml
            RELEASE loVerifier
            RELEASE loSbExternalData
            CANCEL
        ENDIF

    ENDIF

    i = i + 1
ENDDO

* Now that we have the external data available, we can verify the reference digest(s) and the signature.
lnBVerified = loVerifier.VerifySignature(1)
IF (lnBVerified <> 1) THEN
    ? loVerifier.LastErrorText
    RELEASE loXml
    RELEASE loCert
    RELEASE loGen
    RELEASE loHttp
    RELEASE loSbExternalXml
    RELEASE loSbXml
    RELEASE loVerifier
    RELEASE loSbExternalData
    CANCEL
ENDIF

? "Signature verified!"

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