Lua Requires Chilkat v9.5.0.69+

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. Lua

local chilkat = require("chilkat")

-- 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..

local url = "https://www.chilkatsoft.com/exampleData/xmlsig_external_jpg_reference.xml"
local http = chilkat.Http.new()
local sbXml = chilkat.StringBuilder.new()
local success = http:quick_get_sb(url, sbXml)
if not success then
    print(http.last_error_text)
    return
end

local verifier = chilkat.XmlDSig.new()

-- 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.
success = verifier:load_signature_sb(sbXml)
if not success then
    print(verifier.last_error_text)
    return
end

-- 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">
local refUri = verifier:reference_uri(0)
if not verifier.last_method_success then
    print("No reference URI found.")
    return
end

-- Download the JPG data to be verified.
local jpgData = chilkat.BinData.new()
success = http:quick_get_bd(refUri, jpgData)
if not success then
    print(http.last_error_text)
    return
end

-- Provide the JPG data to the verifier
verifier:set_ref_data_bd(0, jpgData)

-- Verify the signature
local bVerified = verifier:verify_signature(true)
print("Signature verified = " .. tostring(bVerified))