Lua Requires Chilkat v9.5.0.69+

Verify XML Digital Signature having KeyName

See more XML Digital Signatures Examples

Demonstrates how to verify an XML digital signature where the KeyInfo part contains the KeyName element.
In this case, the public key is not specifically stored in the signed XML.
Rather, application specific information about the key is stored in the KeyName element.
This example uses the KeyName to find and matching public key. Lua

local chilkat = require("chilkat")

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

-- The signed XML to be verified in this example contains the following:
--
-- <?xml version="1.0" encoding="UTF-8" standalone="no"?>
-- <Envelope>
--   <Header>
--     <Security>
--     <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/2009/xmldsig11#dsa-sha256"/><ds:Reference URI="#abc"><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>XTjDIHSEsDNTO9yn4cKtyXjRUjPFXkOQOLYI5mueZhk=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>NXOIMevGCqFl0Dwtp2KkqkT05GRV8CjmHZ9LhFpt8/d7+lkIi7mITA==</ds:SignatureValue><ds:KeyInfo><ds:KeyName>dsaKey_123</ds:KeyName></ds:KeyInfo></ds:Signature></Security>
--   </Header>
--   <Body Id="abc">
--     <z:FooBar xmlns:z="https://www.example-code.com"/>
--   </Body>
-- </Envelope>
--

-- The above XML is available at https://www.chilkatsoft.com/exampleData/signedUsingKeyName.xml
-- First we'll fetch the signed XML:

local url = "https://www.chilkatsoft.com/exampleData/signedUsingKeyName.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 signature to be verified.
success = verifier:load_signature_sb(sbXml)
if not success then
    print(verifier.last_error_text)
    return
end

-- (The Chilkat XML Digital Signature API has the capability to handle XML documents with multiple signatures.
-- We know in advance that this signed XML has just one Signature, so we leave the dsig.Selector property at the
-- default value of 0.)

-- Let's get the KeyInfo XML so we can then get the KeyName.
local xmlKeyInfo = verifier:get_key_info()
if not verifier.last_method_success then
    print("There is no KeyInfo available in the Signature.")
    return
end

-- Examine the XML:
print(xmlKeyInfo:get_xml())

-- The KeyInfo XML that is returned looks like this:
--
--     <ds:KeyInfo>
--         <ds:KeyName>dsaKey_123</ds:KeyName>
--     </ds:KeyInfo>
--

-- Get the KeyName.
local sbKeyName = chilkat.StringBuilder.new()
sbKeyName:append(xmlKeyInfo:get_child_content("*:KeyName"))

-- sbKeyName contains "dsaKey_123"
print(sbKeyName:get_as_string())

-- The application now locates and loads the public key for verification
-- based on the key name.  This example will do the following:
-- If the key name equals "dsaKey_123", then load the DSA key from
-- "qa_data/dsa/dsa1024_public.pem"
--

if not sbKeyName:contents_equal("dsaKey_123", false) then
    print("I don't know this key...")
    return
end

-- The DSA public key used in this example is available at:
-- https://www.chilkatsoft.com/exampleData/dsa1024_public.zip
local pubKey = chilkat.PublicKey.new()
success = pubKey:load_from_file("qa_data/dsa/dsa1024_public.pem")
if not success then
    print(pubKey.last_error_text)
    return
end

-- Provide the DSA public key to the XML DSig verifier:
verifier:set_public_key(pubKey)

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