description = [[
Matches SSL certificate hash against Google Certificate Catalog.  It
uses the certificate gotten from ssl-cert.nse script.
]]

---
-- @usage
-- nmap -p 443 --script ssl-cert,ssl-google-cert-catalog <host>
--
-- @output
-- PORT     STATE SERVICE
---443/tcp open  https
---| ssl-google-cert-catalog: 
---|   First/Last time saw: 19 Aug 2011 / 10 Sep 2011
---|_  Days saw between: 20

author = "Vasiliy Kulikov"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = { "safe", "discovery", "external" }
dependencies = { "ssl-cert" }

require("nmap")
require("shortport")
require("stdnse")
require("dns")


local get_cert = function(host, port)
    if nmap.registry[host.ip] and nmap.registry[host.ip][port] then
        return nmap.registry[host.ip][port]["ssl-cert"]
    end
end

local format_date = function(day_num)
    return os.date("%d %b %Y", 60 * 60 * 24 * tonumber(day_num))
end

portrule = shortport.ssl

action = function(host, port)
    local lines, sha1, query
    local cert = get_cert(host, port.number)

    if not cert then
        return nil
    end

    sha1 = stdnse.tohex(cert.digest(cert, "sha1"))
    query = sha1 .. ".certs.googlednstest.com"
    stdnse.print_debug("%s %s", SCRIPT_NAME, query)

    local status, decoded_response = dns.query(query, { dtype = "TXT" })

    lines = {}

    if status then
        local raw_start, raw_stop, delta = string.match(decoded_response, "(%d+) (%d+) (%d+)")
        local date_start, date_stop = format_date(raw_start), format_date(raw_stop)

        table.insert(lines, "First/Last time saw: " .. date_start .. " / " .. date_stop)
        table.insert(lines, "Days saw between: " .. tonumber(delta))
    else
        table.insert(lines, "No DB entry")
    end

    return stdnse.format_output(true, lines)
end