B4X

Create/Verify XML Signature with External Text Reference

See more XML Digital Signatures Examples

Demonstrates how to create an XML digital signature where the referenced data is external. In this case, the data is a text file located at the following URL: https://www.chilkatsoft.com/helloWorld.txt B4X

Dim success As Boolean = False

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

'  This example inserts an XML signature into the following XML:

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

'  Build the above XML to be signed.
Dim xml As ChilkatXml
xml.Initialize
xml.Tag = "abc"
xml.UpdateChildContent("xyz|name", "helloWorld.txt")
xml.UpdateChildContent("xyz|url", "https://www.chilkatsoft.com/helloWorld.txt")

Dim cert As ChilkatCert
cert.Initialize("cert")

success = cert.LoadPfxFile("qa_data/pfx/test_secret.pfx", "secret")
If success = False Then
    Log(cert.LastErrorText)
    Return
End If


Dim gen As ChilkatXmlDSigGen
gen.Initialize("gen")

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

'  Get the content of the text data to be referenced.
Dim http As ChilkatHttp
http.Initialize("http")
Dim sbExternalTxt As ChilkatStringBuilder
sbExternalTxt.Initialize
success = http.QuickGetSb("https://www.chilkatsoft.com/helloWorld.txt", sbExternalTxt)
If success = False Then
    Log(http.LastErrorText)
    Return
End If


success = gen.AddExternalTextRef("https://www.chilkatsoft.com/helloWorld.txt", sbExternalTxt, "utf-8", False, "sha256", "")
If success = False Then
    Log(gen.LastErrorText)
    Return
End If


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

Dim bUsePrivateKey As Boolean = True
success = gen.SetX509Cert(cert, bUsePrivateKey)
If success <> True Then
    Log(gen.LastErrorText)
    Return
End If


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

'  Now create and insert the Signature
Dim sbXml As ChilkatStringBuilder
sbXml.Initialize
xml.GetXmlSb(sbXml)
success = gen.CreateXmlDSigSb(sbXml)
If success <> True Then
    Log(gen.LastErrorText)
    Return
End If


'  Examine the XML with the digital signature inserted
Log(sbXml.GetAsString)

'  Here is the output:

'  <?xml version="1.0" encoding="utf-8"?>
'  <abc>
'      <xyz>
'          <name>helloWorld.txt</name>
'          <url>https://www.chilkatsoft.com/helloWorld.txt</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/helloWorld.txt">
'        <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
'        <ds:DigestValue>f4OxZX/x/FO5LcGBSKHWXfwtSx+j1ncoSt3SABJtkGk=</ds:DigestValue>
'      </ds:Reference>
'    </ds:SignedInfo>
'    <ds:SignatureValue>syFSl...pZDiFQ==</ds:SignatureValue>
'    <ds:KeyInfo>
'      <ds:X509Data>
'        <ds:X509Certificate>MIIHAz...GwnUZWCaDE=</ds:X509Certificate>
'      </ds:X509Data>
'    </ds:KeyInfo>
'  </ds:Signature></xyz>
'  </abc>

'  Let's verify the signature...
Dim verifier As ChilkatXmlDSig
verifier.Initialize
success = verifier.LoadSignatureSb(sbXml)
If success <> True Then
    Log(verifier.LastErrorText)
    Return
End If


'  Let's examine the external references, and fetch the data for each..
Dim sbExternalData As ChilkatStringBuilder
sbExternalData.Initialize
Dim numRefs As Int = verifier.NumReferences
Dim i As Int = 0
Do While i < numRefs
    Dim bExternal As Boolean = verifier.IsReferenceExternal(i)
    If bExternal = True Then
        Dim uri As String = verifier.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.
        sbExternalData.Clear
        success = http.QuickGetSb(uri, sbExternalData)
        If success = False Then
            Log(http.LastErrorText)
            Return
        End If


        success = verifier.SetRefDataSb(i, sbExternalData, "utf-8")
        If success = False Then
            Log(verifier.LastErrorText)
            Return
        End If

    End If

    i = i + 1
Loop

'  Now that we have the external data available, we can verify the reference digest(s) and the signature.
Dim bVerified As Boolean = verifier.VerifySignature(True)
If bVerified <> True Then
    Log(verifier.LastErrorText)
    Return
End If


Log("Signature verified!")