Lua

Create XML Signature with External XML 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 an XML file located at the following URL: https://www.chilkatsoft.com/data/helloWorld.xml Lua

local chilkat = require("chilkat")

-- 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.
local xml = chilkat.Xml.new()
xml.tag = "abc"
xml:update_child_content("xyz|name", "helloWorld.xml")
xml:update_child_content("xyz|url", "https://www.chilkatsoft.com/data/helloWorld.xml")

local cert = chilkat.Cert.new()

local success = cert:load_pfx_file("qa_data/pfx/test_secret.pfx", "secret")
if not success then
    print(cert.last_error_text)
    return
end

local gen = chilkat.XmlDSigGen.new()

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

-- Get the content of the XML data to be referenced.
local http = chilkat.Http.new()
local sbExternalXml = chilkat.StringBuilder.new()
success = http:quick_get_sb("https://www.chilkatsoft.com/data/helloWorld.xml", sbExternalXml)
if not success then
    print(http.last_error_text)
    return
end

success = gen:add_external_xml_ref("https://www.chilkatsoft.com/data/helloWorld.xml", sbExternalXml, "sha256", "EXCL_C14N", "")
if not success then
    print(gen.last_error_text)
    return
end

-- Provide the private key for signing via the certificate, and indicate that
-- we want the base64 of the certificate embedded in the KeyInfo.
gen.key_info_type = "X509Data"
gen.x509_type = "Certificate"

local bUsePrivateKey = true
success = gen:set_x509_cert(cert, bUsePrivateKey)
if not success then
    print(gen.last_error_text)
    return
end

-- 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
local sbXml = chilkat.StringBuilder.new()
xml:get_xml_sb(sbXml)
success = gen:create_xml_dsig_sb(sbXml)
if not success then
    print(gen.last_error_text)
    return
end

-- Examine the XML with the digital signature inserted
print(sbXml:get_as_string())

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

-- Let's examine the external references, and fetch the data for each..
local sbExternalData = chilkat.StringBuilder.new()
local numRefs = verifier.num_references
local i = 0
while i < numRefs do
    local bExternal = verifier:is_reference_external(i)
    if bExternal then
        local uri = verifier:reference_uri(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:quick_get_sb(uri, sbExternalData)
        if not success then
            print(http.last_error_text)
            return
        end

        -- 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.
        local canonXml = verifier:canonicalize_xml(sbExternalData:get_as_string(), "EXCL_C14N", false)
        sbExternalData:set_string(canonXml)

        success = verifier:set_ref_data_sb(i, sbExternalData, "utf-8")
        if not success then
            print(verifier.last_error_text)
            return
        end
    end

    i = i + 1
end

-- Now that we have the external data available, we can verify the reference digest(s) and the signature.
local bVerified = verifier:verify_signature(true)
if not bVerified then
    print(verifier.last_error_text)
    return
end

print("Signature verified!")