-- 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;

};