Verify DomainKey-Signature Headers in Downloaded Email

local chilkat = require("chilkat")

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

local imap = chilkat.Imap.new()

-- Connect to an IMAP server, login, select mailbox..
-- Use TLS
imap.ssl = true
imap.port = 993
local success = imap:connect("imap.example.com")
if success then
    success = imap:login("myLogin", "myPassword")
    if success then
        success = imap:select_mailbox("Inbox")
    end
end

if not success then
    print(imap.last_error_text)
    return
end

-- Note: DKIM-Signatures are much more common than DomainKey-Signature
-- See DKIM-Signature Verify Sample.

local dkim = chilkat.Dkim.new()

-- Download a max of 10 emails and verify any DomainKey-Signature headers
-- that are present.

-- Download emails by sequence numbers (not UIDs).
local bUid = false
local j = 0
local n = imap.num_messages
if n > 50 then
    n = 50
end

local json = chilkat.JsonObject.new()
json.emit_compact = false

-- To verify DomainKey-Signature headers, we need the exact unmodified MIME bytes of each email.
local mimeData = chilkat.BinData.new()
local seqNum = 1
while seqNum <= n do
    success = imap:fetch_single_bd(seqNum, bUid, mimeData)
    if not success then
        print(imap.last_error_text)
        return
    end

    -- Note: DKIM-Signatures are much more common than DomainKey-Signature
    -- See DKIM-Signature Verify Sample.

    -- Get the number of DomainKey-Signature headers.
    local numSigs = ERROR: Method not in Chilkat for Lua: Dkim.NumDomainKeySigs
dkim:ERROR()

    -- Verify each..
    j = 0
    while j < numSigs do
        print("------ DomainKey Signature " .. j)

        success = ERROR: Method not in Chilkat for Lua: Dkim.DomainKeyVerify
dkim:ERROR()
        if not success then
            print("Not valid.")
            print(dkim.last_error_text)
        else
            print("valid.")
        end

        -- Show the additional information about the signature verification
        json:load(dkim.verify_info)
        print(json:emit())

        -- The JSON contains information such as this:

        --     {
        --       "domain": "amazonses.com",
        --       "selector": "7v7vs6w47njt4pimodk5mmttbegzsi6n",
        --       "publicKey": "MIGfMA0GCSqG...v2GvWPqGHz6uqeQIDAQAB",
        --       "canonicalization": "relaxed/simple",
        --       "algorithm": "rsa-sha256",
        --       "signedHeaders": "Subject:From:To:Date:Mime-Version:Content-Type:References:Message-Id:Feedback-ID",
        --       "verified": "yes"
        --     }

        j = j + 1
    end

    seqNum = seqNum + 1
end

success = imap:disconnect()