File

util/dns.lua @ 12480:7e9ebdc75ce4

net: isolate LuaSec-specifics For this, various accessor functions are now provided directly on the sockets, which reach down into the LuaSec implementation to obtain the information. While this may seem of little gain at first, it hides the implementation detail of the LuaSec+LuaSocket combination that the actual socket and the TLS layer are separate objects. The net gain here is that an alternative implementation does not have to emulate that specific implementation detail and "only" has to expose LuaSec-compatible data structures on the new functions.
author Jonas Schäfer <jonas@wielicki.name>
date Wed, 27 Apr 2022 17:44:14 +0200
parent 12355:a0ff5c438e9d
child 12975:d10957394a3c
line wrap: on
line source

-- libunbound based net.adns replacement for Prosody IM
-- Copyright (C) 2012-2015 Kim Alvefur
-- Copyright (C) 2012 Waqas Hussain
--
-- This file is MIT licensed.

local setmetatable = setmetatable;
local table = table;
local t_concat = table.concat;
local t_insert = table.insert;
local s_byte = string.byte;
local s_format = string.format;
local s_sub = string.sub;

local iana_data = require "util.dnsregistry";
local tohex = require "util.hex".encode;
local inet_ntop = require "util.net".ntop;

-- Simplified versions of Waqas DNS parsers
-- Only the per RR parsers are needed and only feed a single RR

local parsers = {};

-- No support for pointers, but libunbound appears to take care of that.
local function readDnsName(packet, pos)
	if s_byte(packet, pos) == 0 then return ".", pos+1; end
	local pack_len, r, len = #packet, {};
	pos = pos or 1;
	repeat
		len = s_byte(packet, pos) or 0;
		t_insert(r, s_sub(packet, pos + 1, pos + len));
		pos = pos + len + 1;
	until len == 0 or pos >= pack_len;
	return t_concat(r, "."), pos;
end

-- These are just simple names.
parsers.CNAME = readDnsName;
parsers.NS = readDnsName
parsers.PTR = readDnsName;

local soa_mt = {
	__tostring = function(rr)
		return s_format("%s %s %d %d %d %d %d", rr.mname, rr.rname, rr.serial, rr.refresh, rr.retry, rr.expire, rr.minimum);
	end;
};
function parsers.SOA(packet)
	local mname, rname, offset;

	mname, offset = readDnsName(packet, 1);
	rname, offset = readDnsName(packet, offset);

	-- Extract all the bytes of these fields in one call
	local
		s1, s2, s3, s4, -- serial
		r1, r2, r3, r4, -- refresh
		t1, t2, t3, t4, -- retry
		e1, e2, e3, e4, -- expire
		m1, m2, m3, m4  -- minimum
			= s_byte(packet, offset, offset + 19);

	return setmetatable({
		mname = mname;
		rname = rname;
		serial  = s1*0x1000000 + s2*0x10000 + s3*0x100 + s4;
		refresh = r1*0x1000000 + r2*0x10000 + r3*0x100 + r4;
		retry   = t1*0x1000000 + t2*0x10000 + t3*0x100 + t4;
		expire  = e1*0x1000000 + e2*0x10000 + e3*0x100 + e4;
		minimum = m1*0x1000000 + m2*0x10000 + m3*0x100 + m4;
	}, soa_mt);
end

parsers.A = inet_ntop;
parsers.AAAA = inet_ntop;

local mx_mt = {
	__tostring = function(rr)
		return s_format("%d %s", rr.pref, rr.mx)
	end
};
function parsers.MX(packet)
	local name = readDnsName(packet, 3);
	local b1,b2 = s_byte(packet, 1, 2);
	return setmetatable({
		pref = b1*256+b2;
		mx = name;
	}, mx_mt);
end

local srv_mt = {
	__tostring = function(rr)
		return s_format("%d %d %d %s", rr.priority, rr.weight, rr.port, rr.target);
	end
};
function parsers.SRV(packet)
	local name = readDnsName(packet, 7);
	local b1, b2, b3, b4, b5, b6 = s_byte(packet, 1, 6);
	return setmetatable({
		priority = b1*256+b2;
		weight   = b3*256+b4;
		port     = b5*256+b6;
		target   = name;
	}, srv_mt);
end

local txt_mt = { __tostring = t_concat };
function parsers.TXT(packet)
	local pack_len = #packet;
	local r, pos, len = {}, 1;
	repeat
		len = s_byte(packet, pos) or 0;
		t_insert(r, s_sub(packet, pos + 1, pos + len));
		pos = pos + len + 1;
	until pos >= pack_len;
	return setmetatable(r, txt_mt);
end

parsers.SPF = parsers.TXT;

-- Acronyms from RFC 7218
local tlsa_usages = {
	[0] = "PKIX-CA";
	[1] = "PKIX-EE";
	[2] = "DANE-TA";
	[3] = "DANE-EE";
	[255] = "PrivCert";
};
local tlsa_selectors = {
	[0] = "Cert",
	[1] = "SPKI",
	[255] = "PrivSel",
};
local tlsa_match_types = {
	[0] = "Full",
	[1] = "SHA2-256",
	[2] = "SHA2-512",
	[255] = "PrivMatch",
};
local tlsa_mt = {
	__tostring = function(rr)
		return s_format("%s %s %s %s",
			tlsa_usages[rr.use] or rr.use,
			tlsa_selectors[rr.select] or rr.select,
			tlsa_match_types[rr.match] or rr.match,
			tohex(rr.data));
	end;
	__index = {
		getUsage = function(rr) return tlsa_usages[rr.use] end;
		getSelector = function(rr) return tlsa_selectors[rr.select] end;
		getMatchType = function(rr) return tlsa_match_types[rr.match] end;
	}
};
function parsers.TLSA(packet)
	local use, select, match = s_byte(packet, 1,3);
	return setmetatable({
		use = use;
		select = select;
		match = match;
		data = s_sub(packet, 4);
	}, tlsa_mt);
end

local svcb_params = {"alpn"; "no-default-alpn"; "port"; "ipv4hint"; "ech"; "ipv6hint"};
setmetatable(svcb_params, {__index = function(_, n) return "key" .. tostring(n); end});

local svcb_mt = {
	__tostring = function (rr)
		local kv = {};
		for i = 1, #rr.fields do
			t_insert(kv, s_format("%s=%q", svcb_params[rr.fields[i].key], tostring(rr.fields[i].value)));
			-- FIXME the =value part may be omitted when the value is "empty"
		end
		return s_format("%d %s %s", rr.prio, rr.name, t_concat(kv, " "));
	end;
};
local svbc_ip_mt = {__tostring = function(ip) return t_concat(ip, ", "); end}

function parsers.SVCB(packet)
	local prio_h, prio_l = packet:byte(1,2);
	local prio = prio_h*256+prio_l;
	local name, pos = readDnsName(packet, 3);
	local fields = {};
	while #packet > pos do
		local key_h, key_l = packet:byte(pos+0,pos+1);
		local len_h, len_l = packet:byte(pos+2,pos+3);
		local key = key_h*256+key_l;
		local len = len_h*256+len_l;
		local value = packet:sub(pos+4,pos+4-1+len)
		if key == 1 then
			value = setmetatable(parsers.TXT(value), svbc_ip_mt);
		elseif key == 3 then
			local port_h, port_l = value:byte(1,2);
			local port = port_h*256+port_l;
			value = port;
		elseif key == 4 then
			local ip = {};
			for i = 1, #value, 4 do
				t_insert(ip, parsers.A(value:sub(i, i+3)));
			end
			value = setmetatable(ip, svbc_ip_mt);
		elseif key == 6 then
			local ip = {};
			for i = 1, #value, 16 do
				t_insert(ip, parsers.AAAA(value:sub(i, i+15)));
			end
			value = setmetatable(ip, svbc_ip_mt);
		end
		t_insert(fields, { key = key, value = value, len = len });
		pos = pos+len+4;
	end
	return setmetatable({
			prio = prio, name = name, fields = fields,
		}, svcb_mt);
end

parsers.HTTPS = parsers.SVCB;

local params = {
	TLSA = {
		use = tlsa_usages;
		select = tlsa_selectors;
		match = tlsa_match_types;
	};
};

local fallback_mt = {
	__tostring = function(rr)
		return s_format([[\# %d %s]], #rr.raw, tohex(rr.raw));
	end;
};
local function fallback_parser(packet)
	return setmetatable({ raw = packet },fallback_mt);
end
setmetatable(parsers, { __index = function() return fallback_parser end });

return {
	parsers = parsers;
	classes = iana_data.classes;
	types = iana_data.types;
	errors = iana_data.errors;
	params = params;
};