Lianja

Verify XML Signature with External Data Reference

See more XML Digital Signatures Examples

Demonstrates how to verify an XML digital signature where the data is external. In this case, the data is a JPG file.

This example requires Chilkat v9.5.0.69 or greater.

Lianja

llSuccess = .F.

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

// The XML containing the Signature to be verified contains the following:
// <?xml version="1.0" encoding="UTF-8" standalone="no"?>
// <abc>
//   <xyz>
//     <jpg>
//         <name>starfish.jpg</name>
//         <url>https://www.chilkatsoft.com/images/starfish.jpg</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/images/starfish.jpg"><ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/><ds:DigestValue>AOU810yJV5Np/DnO29qpObqiTSTTCDvxGsX5ayiTYXI=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>MbHOti6nOh9DJP/u7u1+a1u0wRYIGEdaAVk5ehxqeBhcR4qvGvCQ7wLxcfDuwFG2grSg43ANxDYngLqZTeFb5nCfywcuNBQI8FrNRVY5hkyv6kDW1BVN8ot9qPYX9oHxJp1e+nMszIiSxqHX3XDI7YnvFt/0CyeO5JaQQEzXzIwqqb8iUNcH/bJzR6CrTf1hGuQ5MPorG0bRwbYPPHHzipUqHBinK8VbHobnxL7GQHAhR8k9gDD35kZcMxf/74U7pGO19ZzTbdJW5S7q4bVVxvsuU3itTbhHI60pOE14ibrjZtIrPZLVUD3TQqIIF04TChW2NXdYOo3+ij4ZnP8x+g==</ds:SignatureValue><ds:KeyInfo><ds:KeyValue><ds:RSAKeyValue><ds:Modulus>sXeRhM55P13FbpNcXAMR3olbw2Wa6keZIHu5YTZYUBTlYWId+pNiwUz3zFIEo+0IfYR0H27ybIycQO+1IIzJofUFNMAL3tZps2OKPlsjuCPls6kXpXhv/gvhux8LrCtp4PcKWqJ6QVOZKChc7WAx40qFWzHi57ueqRTv3x0kESqGg/VjsqyTEvb55psJO2RsfhLT7+YVh3hImRM3RDaJdkTkPuOxeFyT6N7VXD09329sLuS3QkUbE9zEKDnz9X3d8dEQdJhSI9ba5fxl8R7fu8pB67ElfzFml96X1jLFtzy1pzOT5Fc4ROcaqlYckVzdBq9sxezm6MYmDBjNAcibRw==</ds:Modulus><ds:Exponent>AQAB</ds:Exponent></ds:RSAKeyValue></ds:KeyValue></ds:KeyInfo></ds:Signature></jpg>
//   </xyz>
// </abc>

// The above XML is available at https://www.chilkatsoft.com/exampleData/xmlsig_external_jpg_reference.xml
// First fetch the XML..

lcUrl = "https://www.chilkatsoft.com/exampleData/xmlsig_external_jpg_reference.xml"
loHttp = createobject("CkHttp")
loSbXml = createobject("CkStringBuilder")
llSuccess = loHttp.QuickGetSb(lcUrl,loSbXml)
if (llSuccess <> .T.) then
    ? loHttp.LastErrorText
    release loHttp
    release loSbXml
    return
endif

loVerifier = createobject("CkXmlDSig")

// Load the XML containing the signatures to be verified.
// Note that this particular Signature already contains the RSA public key that will be used
// for verification.
llSuccess = loVerifier.LoadSignatureSb(loSbXml)
if (llSuccess <> .T.) then
    ? loVerifier.LastErrorText
    release loHttp
    release loSbXml
    release loVerifier
    return
endif

// Get the Reference URI, which in this case is the URL to the binary data that was hashed.
// This fetchs the URI attribute value from:  <ds:Reference URI="https://www.chilkatsoft.com/images/starfish.jpg">
lcRefUri = loVerifier.ReferenceUri(0)
if (loVerifier.LastMethodSuccess <> .T.) then
    ? "No reference URI found."
    release loHttp
    release loSbXml
    release loVerifier
    return
endif

// Download the JPG data to be verified.
loJpgData = createobject("CkBinData")
llSuccess = loHttp.QuickGetBd(lcRefUri,loJpgData)
if (llSuccess <> .T.) then
    ? loHttp.LastErrorText
    release loHttp
    release loSbXml
    release loVerifier
    release loJpgData
    return
endif

// Provide the JPG data to the verifier
loVerifier.SetRefDataBd(0,loJpgData)

// Verify the signature
llBVerified = loVerifier.VerifySignature(.T.)
? "Signature verified = " + str(llBVerified)


release loHttp
release loSbXml
release loVerifier
release loJpgData