local dns = require "dns"
local stdnse = require "stdnse"
local table = require "table"
local ipOps = require "ipOps"
description = [[
Checks DNS zone configuration against best practices, including RFC 1912.
The configuration checks are divided into categories which each have a number
of different tests.
]]
---
-- @usage
-- nmap -sn -Pn ns1.example.com --script dns-check-zone --script-args='dns-check-zone.domain=example.com'
--
-- @output
-- | dns-check-zone:
-- | DNS check results for domain: example.com
-- | SOA
-- | PASS - SOA REFRESH
-- | SOA REFRESH was within recommended range (7200s)
-- | PASS - SOA RETRY
-- | SOA RETRY was within recommended range (3600s)
-- | PASS - SOA EXPIRE
-- | SOA EXPIRE was within recommended range (1209600s)
-- | FAIL - SOA MNAME entry check
-- | SOA MNAME record is NOT listed as DNS server
-- | PASS - Zone serial numbers
-- | Zone serials match
-- | MX
-- | ERROR - Reverse MX A records
-- | Failed to retrieve list of mail servers
-- | NS
-- | PASS - Recursive queries
-- | None of the servers allow recursive queries.
-- | PASS - Multiple name servers
-- | Server has 2 name servers
-- | PASS - DNS name server IPs are public
-- | All DNS IPs were public
-- | PASS - DNS server response
-- | All servers respond to DNS queries
-- | PASS - Missing nameservers reported by parent
-- | All DNS servers match
-- | PASS - Missing nameservers reported by your nameservers
-- |_ All DNS servers match
--
-- @args dns-check-zone.domain the dns zone to check
--
author = "Patrik Karlsson"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = {"discovery", "safe", "external"}
local arg_domain = stdnse.get_script_args(SCRIPT_NAME .. '.domain')
hostrule = function(host) return ( arg_domain ~= nil ) end
local PROBE_HOST = "scanme.nmap.org"
local Status = {
PASS = "PASS",
FAIL = "FAIL",
}
local function isValidSOA(res)
if ( not(res) or type(res.answers) ~= "table" or type(res.answers[1].SOA) ~= "table" ) then
return false
end
return true
end
local dns_checks = {
["NS"] = {
{
desc = "Recursive queries",
func = function(domain, server)
local status, res = dns.query(domain, { host = server, dtype='NS', retAll = true })
local result = {}
if ( not(status) ) then
return false, "Failed to retrieve list of DNS servers"
end
for _, srv in ipairs(res or {}) do
local status, res = dns.query(PROBE_HOST, { host = srv, dtype='A' })
if ( status ) then
table.insert(result, res)
end
end
local output = "None of the servers allow recursive queries."
if ( 0 < #result ) then
output = ("The following servers allow recursive queries: %s"):format(stdnse.strjoin(", ", result))
return true, { status = Status.FAIL, output = output }
end
return true, { status = Status.PASS, output = output }
end
},
{
desc = "Multiple name servers",
func = function(domain, server)
local status, res = dns.query(domain, { host = server, dtype='NS', retAll = true })
if ( not(status) ) then
return false, "Failed to retrieve list of DNS servers"
end
local status = Status.FAIL
if ( 1 < #res ) then
status = Status.PASS
end
return true, { status = status, output = ("Server has %d name servers"):format(#res) }
end
},
{
desc = "DNS name server IPs are public",
func = function(domain, server)
local status, res = dns.query(domain, { host = server, dtype='NS', retAll = true })
if ( not(status) ) then
return false, "Failed to retrieve list of DNS servers"
end
local result = {}
for _, srv in ipairs(res or {}) do
local status, res = dns.query(srv, { dtype='A', retAll = true })
if ( not(status) ) then
return false, ("Failed to retrieve IP for DNS: %s"):format(srv)
end
for _, ip in ipairs(res) do
if ( ipOps.isPrivate(ip) ) then
table.insert(result, ip)
end
end
end
local output = "All DNS IPs were public"
if ( 0 < #result ) then
output = ("The following private IPs were detected: %s"):format(stdnse.strjoin(", ", result))
status = Status.FAIL
else
status = Status.PASS
end
return true, { status = status, output = output }
end
},
{
desc = "DNS server response",
func = function(domain, server)
local status, res = dns.query(domain, { host = server, dtype='NS', retAll = true })
if ( not(status) ) then
return false, "Failed to retrieve list of DNS servers"
end
local result = {}
for _, srv in ipairs(res or {}) do
local status, res = dns.query(domain, { host = srv, dtype='SOA', retPkt = true })
if ( not(status) ) then
table.insert(result, res)
end
end
local output = "All servers respond to DNS queries"
if ( 0 < #result ) then
output = ("The following servers did not respond to DNS queries: %s"):format(stdnse.strjoin(", ", result))
return true, { status = Status.FAIL, output = output }
end
return true, { status = Status.PASS, output = output }
end
},
{
desc = "Missing nameservers reported by parent",
func = function(domain, server)
local tld = domain:match("%.(.*)$")
local status, res = dns.query(tld, { dtype = "NS", retAll = true })
if ( not(status) ) then
return false, "Failed to retrieve list of TLD DNS servers"
end
local status, parent_res = dns.query(domain, { host = res, dtype = "NS", retAll = true, retPkt = true, noauth = true } )
if ( not(status) ) then
return false, "Failed to retrieve a list of parent DNS servers"
end
if ( not(status) or not(parent_res) or type(parent_res.auth) ~= "table" ) then
return false, "Failed to retrieve a list of parent DNS servers"
end
local parent_dns = {}
for _, auth in ipairs(parent_res.auth) do
parent_dns[auth.domain] = true
end
status, res = dns.query(domain, { host = server, dtype = "NS", retAll = true } )
if ( not(status) ) then
return false, "Failed to retrieve a list of DNS servers"
end
local domain_dns = {}
for _,srv in ipairs(res) do domain_dns[srv] = true end
local result = {}
for srv in pairs(domain_dns) do
if ( not(parent_dns[srv]) ) then
table.insert(result, srv)
end
end
if ( 0 < #result ) then
local output = ("The following servers were found in the zone, but not in the parent: %s"):format(stdnse.strjoin(", ", result))
return true, { status = Status.FAIL, output = output }
end
return true, { status = Status.PASS, output = "All DNS servers match" }
end,
},
{
desc = "Missing nameservers reported by your nameservers",
func = function(domain, server)
local tld = domain:match("%.(.*)$")
local status, res = dns.query(tld, { dtype = "NS", retAll = true })
if ( not(status) ) then
return false, "Failed to retrieve list of TLD DNS servers"
end
local status, parent_res = dns.query(domain, { host = res, dtype = "NS", retAll = true, retPkt = true, noauth = true } )
if ( not(status) ) then
return false, "Failed to retrieve a list of parent DNS servers"
end
if ( not(status) or not(parent_res) or type(parent_res.auth) ~= "table" ) then
return false, "Failed to retrieve a list of parent DNS servers"
end
local parent_dns = {}
for _, auth in ipairs(parent_res.auth) do
parent_dns[auth.domain] = true
end
status, res = dns.query(domain, { host = server, dtype = "NS", retAll = true } )
if ( not(status) ) then
return false, "Failed to retrieve a list of DNS servers"
end
local domain_dns = {}
for _,srv in ipairs(res) do domain_dns[srv] = true end
local result = {}
for srv in pairs(parent_dns) do
if ( not(domain_dns[srv]) ) then
table.insert(result, srv)
end
end
if ( 0 < #result ) then
local output = ("The following servers were found in the parent, but not in the zone: %s"):format(stdnse.strjoin(", ", result))
return true, { status = Status.FAIL, output = output }
end
return true, { status = Status.PASS, output = "All DNS servers match" }
end,
},
},
["SOA"] =
{
{
desc = "SOA REFRESH",
func = function(domain, server)
local status, res = dns.query(domain, { host = server, dtype='SOA', retPkt=true })
if ( not(status) or not(isValidSOA(res)) ) then
return false, "Failed to retrieve SOA record"
end
local refresh = tonumber(res.answers[1].SOA.refresh)
if ( not(refresh) ) then
return false, "Failed to retrieve SOA REFRESH"
end
if ( refresh < 1200 or refresh > 43200 ) then
return true, { status = Status.FAIL, output = ("SOA REFRESH was NOT within recommended range (%ss)"):format(refresh) }
else
return true, { status = Status.PASS, output = ("SOA REFRESH was within recommended range (%ss)"):format(refresh) }
end
end
},
{
desc = "SOA RETRY",
func = function(domain, server)
local status, res = dns.query(domain, { host = server, dtype='SOA', retPkt=true })
if ( not(status) or not(isValidSOA(res)) ) then
return false, "Failed to retrieve SOA record"
end
local retry = tonumber(res.answers[1].SOA.retry)
if ( not(retry) ) then
return false, "Failed to retrieve SOA RETRY"
end
if ( retry < 180 ) then
return true, { status = Status.FAIL, output = ("SOA RETRY was NOT within recommended range (%ss)"):format(retry) }
else
return true, { status = Status.PASS, output = ("SOA RETRY was within recommended range (%ss)"):format(retry) }
end
end
},
{
desc = "SOA EXPIRE",
func = function(domain, server)
local status, res = dns.query(domain, { host = server, dtype='SOA', retPkt=true })
if ( not(status) or not(isValidSOA(res)) ) then
return false, "Failed to retrieve SOA record"
end
local expire = tonumber(res.answers[1].SOA.expire)
if ( not(expire) ) then
return false, "Failed to retrieve SOA EXPIRE"
end
if ( expire < 1209600 or expire > 2419200 ) then
return true, { status = Status.FAIL, output = ("SOA EXPIRE was NOT within recommended range (%ss)"):format(expire) }
else
return true, { status = Status.PASS, output = ("SOA EXPIRE was within recommended range (%ss)"):format(expire) }
end
end
},
{
desc = "SOA MNAME entry check",
func = function(domain, server)
local status, res = dns.query(domain, { host = server, dtype='SOA', retPkt=true })
if ( not(status) or not(isValidSOA(res)) ) then
return false, "Failed to retrieve SOA record"
end
local mname = res.answers[1].SOA.mname
status, res = dns.query(domain, { host = server, dtype='NS', retAll = true })
if ( not(status) ) then
return false, "Failed to retrieve list of DNS servers"
end
for _, srv in ipairs(res or {}) do
if ( srv == mname ) then
return true, { status = Status.PASS, output = "SOA MNAME record is listed as DNS server" }
end
end
return true, { status = Status.FAIL, output = "SOA MNAME record is NOT listed as DNS server" }
end
},
{
desc = "Zone serial numbers",
func = function(domain, server)
local status, res = dns.query(domain, { host = server, dtype='NS', retAll = true })
if ( not(status) ) then
return false, "Failed to retrieve list of DNS servers"
end
local result = {}
local serial
for _, srv in ipairs(res or {}) do
local status, res = dns.query(domain, { host = srv, dtype='SOA', retPkt = true })
if ( not(status) or not(isValidSOA(res)) ) then
return false, "Failed to retrieve SOA record"
end
local s = res.answers[1].SOA.serial
if ( not(serial) ) then
serial = s
elseif( serial ~= s ) then
return true, { status = Status.FAIL, output = "Different zone serials were detected" }
end
end
return true, { status = Status.PASS, output = "Zone serials match" }
end,
},
},
["MX"] = {
{
desc = "Reverse MX A records",
func = function(domain, server)
local status, res = dns.query(domain, { host = server, dtype='MX', retAll = true })
if ( not(status) ) then
return false, "Failed to retrieve list of mail servers"
end
local result = {}
for _, record in ipairs(res or {}) do
local prio, mx = record:match("^(%d*):([^:]*)")
local ips
status, ips = dns.query(mx, { dtype='A', retAll=true })
if ( not(status) ) then
return false, "Failed to retrieve A records for MX"
end
for _, ip in ipairs(ips) do
local status, res = dns.query(dns.reverse(ip), { dtype='PTR' })
if ( not(status) ) then
table.insert(result, ip)
end
end
end
local output = "All MX records have PTR records"
if ( 0 < #result ) then
output = ("The following IPs do not have PTR records: %s"):format(stdnse.strjoin(", ", result))
return true, { status = Status.FAIL, output = output }
end
return true, { status = Status.PASS, output = output }
end
},
}
}
action = function(host, port)
local server = host.ip
local output = { name = ("DNS check results for domain: %s"):format(arg_domain) }
for group in pairs(dns_checks) do
local group_output = { name = group }
for _, check in ipairs(dns_checks[group]) do
local status, res = check.func(arg_domain, server)
if ( status ) then
local test_res = ("%s - %s"):format(res.status, check.desc)
table.insert(group_output, { name = test_res, res.output })
else
local test_res = ("ERROR - %s"):format(check.desc)
table.insert(group_output, { name = test_res, res })
end
end
table.insert(output, group_output)
end
return stdnse.format_output(true, output)
end
@KyuuKazami