description = [[
Attempts to list all users on a MySQL server.
]]

---
-- @args mysqluser The username to use for authentication. If unset it
-- attempts to use credentials found by <code>mysql-brute</code> or
-- <code>mysql-empty-password</code>.
-- @args mysqlpass The password to use for authentication. If unset it
-- attempts to use credentials found by <code>mysql-brute</code> or
-- <code>mysql-empty-password</code>.
--
-- @output
-- 3306/tcp open  mysql
-- | mysql-users:  
-- |   test
-- |   root
-- |   test2
-- |   album
-- |   debian-sys-maint
-- |   horde
-- |   mediatomb
-- |_  squeezecenter


author = "Patrik Karlsson"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = {"discovery", "intrusive"}

require 'shortport'
require 'stdnse'
require 'mysql'
stdnse.silent_require 'openssl'

dependencies = {"mysql-brute", "mysql-empty-password"}

-- Version 0.1
-- Created 01/23/2010 - v0.1 - created by Patrik Karlsson <patrik@cqure.net>

portrule = shortport.port_or_service(3306, "mysql")

action = function( host, port )

	local socket = nmap.new_socket()
	local catch = function() socket:close()	end
	local try = nmap.new_try(catch)
	local result, response = {}, nil
	local users = {}
	local nmap_args = nmap.registry.args
	local status, rows
	
	-- set a reasonable timeout value
	socket:set_timeout(5000)
	
	-- first, let's see if the script has any credentials as arguments?
	if nmap_args.mysqluser then
		users[nmap_args.mysqluser] = nmap_args.mysqlpass or ""
	-- next, let's see if mysql-brute or mysql-empty-password brought us anything
	elseif nmap.registry.mysqlusers then
		-- do we have root credentials?
		if nmap.registry.mysqlusers['root'] then
			users['root'] = nmap.registry.mysqlusers['root'] 
		else
			-- we didn't have root, so let's make sure we loop over them all
			users = nmap.registry.mysqlusers
		end
	-- last, no dice, we don't have any credentials at all
	else
		stdnse.print_debug("No credentials supplied, aborting ...")
		return
	end
	
	--
	-- Iterates over credentials, breaks once it successfully recieves results
	--
	for username, password in pairs(users) do
				
		try( socket:connect(host, port) )
	
		response = try( mysql.receiveGreeting( socket ) )
		status, response = mysql.loginRequest( socket, { authversion = "post41", charset = response.charset }, username, password, response.salt )
	
		if status and response.errorcode == 0 then
			status, rows = mysql.sqlQuery( socket, "SELECT DISTINCT user FROM mysql.user" )
			if status then
				for i=1, #rows do
					table.insert(result, rows[i]['user'])
				end		
				break
			end
		end
		socket:close()
	end

	return stdnse.format_output(true, result)	

end