(Xojo Plugin) Verify an XML Signature with Multiple References

Demonstrates how to verify an XML digital signature that contains multiple references.

Chilkat Xojo Plugin Download Xojo Plugin for Windows, Linux, Mac OS X, and ARM, ARM64

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

// An example of an enveloping XML signature with mulitple references is available at
// https://www.chilkatsoft.com/exampleData/envelopedMultipleRefs.xml

// This example will show how to verify the signature and all references, and also how
// to verify each reference individually.  This is useful to distinguish which part
// of the XML signature validation failed.  It could be that one or more of the references
// failed because of a hash computation mismatch.  Or it could be that the signature over
// the SignedInfo failed.  

// First, let's grab the sample XML signature.
Dim http As New Chilkat.Http
Dim sbXml As New Chilkat.StringBuilder
Dim success As Boolean
success = http.QuickGetSb("https://www.chilkatsoft.com/exampleData/envelopedMultipleRefs.xml",sbXml)
If (success <> True) Then
    System.DebugLog(http.LastErrorText)
    Return
End If

// Load the XML containing the signature to be verified.
Dim verifier As New Chilkat.XmlDSig
success = verifier.LoadSignatureSb(sbXml)
If (success <> True) Then
    System.DebugLog(verifier.LastErrorText)
    Return
End If

Dim verifyReferenceDigests As Boolean
verifyReferenceDigests = True

// The quick way to validate all references and the signature over the SignedInfo
// is to call VerifySignature with verifyReferenceDigests equal to True.
Dim verified As Boolean
verified = verifier.VerifySignature(verifyReferenceDigests)
System.DebugLog("Signature and all reference digests verified = " + Str(verified))

// Let's pretend the call to VerifySignature returned False.  Something did not validate.
// Was it one or more of the References that did not hash to the correct value?
// Or was it the signature over the SignedInfo that failed?
// We can check just the signature over the SignedInfo by passing False to VerifySignature.
// This allows us to skip the hashing and checking each Reference.  
verifyReferenceDigests = False
Dim signedInfoVerified As Boolean
signedInfoVerified = verifier.VerifySignature(verifyReferenceDigests)
System.DebugLog("Neglecting the reference hashes, the SignedInfo validation result = " + Str(signedInfoVerified))

// We can also verify each reference digest separately
Dim numRefs As Int32
numRefs = verifier.NumReferences
Dim i As Int32
i = 0
While i < numRefs
    Dim refDigestVerified As Boolean
    refDigestVerified = verifier.VerifyReferenceDigest(i)
    System.DebugLog("Reference " + Str(i) + " digest verified = " + Str(refDigestVerified))
    i = i + 1
Wend

// For this sample XML signature with 3 References, we get the following output:

// Signature and all reference digests verified = True
// Neglecting the reference hashes, the SignedInfo validation result = True
// Reference 0 digest verified = True
// Reference 1 digest verified = True
// Reference 2 digest verified = Tru