-- Prosody IM

-- This file is included with Prosody IM. It has modifications,

-- which are hereby placed in the public domain.

-- todo: quick (default) header generation

-- todo: nxdomain, error handling

-- todo: cache results of encodeName

-- reference: https://www.rfc-editor.org/rfc/rfc1035.html

-- reference: https://www.rfc-editor.org/rfc/rfc1876.html (LOC)

local socket = require "socket";

local have_timer, timer = pcall(require, "prosody.util.timer");

local new_ip = require "prosody.util.ip".new_ip;

local have_util_net, util_net = pcall(require, "prosody.util.net");

local log = require "prosody.util.logger".init("dns");

local _, windows = pcall(require, "prosody.util.windows");

local is_windows = (_ and windows) or os.getenv("WINDIR");

local coroutine, io, math, string, table =

      coroutine, io, math, string, table;

local ipairs, next, pairs, print, setmetatable, tostring, assert, error, select, type =

      ipairs, next, pairs, print, setmetatable, tostring, assert, error, select, type;

local ztact = { -- public domain 20080404 lua@ztact.com

	get = function(parent, ...)

		local len = select('#', ...);

		for i=1,len do

			parent = parent[select(i, ...)];

			if parent == nil then break; end

		end

		return parent;

	end;

	set = function(parent, ...)

		local len = select('#', ...);

		local key, value = select(len-1, ...);

		local cutpoint, cutkey;

		for i=1,len-2 do

			local key = select (i, ...)

			local child = parent[key]

			if value == nil then

				if child == nil then

					return;

				elseif next(child, next(child)) then

					cutpoint = nil; cutkey = nil;

				elseif cutpoint == nil then

					cutpoint = parent; cutkey = key;

				end

			elseif child == nil then

				child = {};

				parent[key] = child;

			end

			parent = child

		end

		if value == nil and cutpoint then

			cutpoint[cutkey] = nil;

		else

			parent[key] = value;

			return value;

		end

	end;

};

local get, set = ztact.get, ztact.set;

local default_timeout = 5;

local default_jitter = 1;

local default_retry_jitter = 2;

-------------------------------------------------- module dns

local _ENV = nil;

-- luacheck: std none

local dns = {};

-- dns type & class codes ------------------------------ dns type & class codes

local append = table.insert

local function highbyte(i)    -- - - - - - - - - - - - - - - - - - -  highbyte

	return (i-(i%0x100))/0x100;

end

local function augment (t, prefix)  -- - - - - - - - - - - - - - - - -  augment

	local a = {};

	for i,s in pairs(t) do

		a[i] = s;

		a[s] = s;

		a[string.lower(s)] = s;

	end

	setmetatable(a, {

		__index = function (_, i)

			if type(i) == "number" then

				return ("%s%d"):format(prefix, i);

			elseif type(i) == "string" then

				return i:upper();

			end

		end;

	})

	return a;

end

local function encode (t)    -- - - - - - - - - - - - - - - - - - - - -  encode

	local code = {};

	for i,s in pairs(t) do

		local word = string.char(highbyte(i), i%0x100);

		code[i] = word;

		code[s] = word;

		code[string.lower(s)] = word;

	end

	return code;

end

dns.types = {

	[1] = "A", -- a host address,[RFC1035],,

	[2] = "NS", -- an authoritative name server,[RFC1035],,

	[3] = "MD", -- a mail destination (OBSOLETE - use MX),[RFC1035],,

	[4] = "MF", -- a mail forwarder (OBSOLETE - use MX),[RFC1035],,

	[5] = "CNAME", -- the canonical name for an alias,[RFC1035],,

	[6] = "SOA", -- marks the start of a zone of authority,[RFC1035],,

	[7] = "MB", -- a mailbox domain name (EXPERIMENTAL),[RFC1035],,

	[8] = "MG", -- a mail group member (EXPERIMENTAL),[RFC1035],,

	[9] = "MR", -- a mail rename domain name (EXPERIMENTAL),[RFC1035],,

	[10] = "NULL", -- a null RR (EXPERIMENTAL),[RFC1035],,

	[11] = "WKS", -- a well known service description,[RFC1035],,

	[12] = "PTR", -- a domain name pointer,[RFC1035],,

	[13] = "HINFO", -- host information,[RFC1035],,

	[14] = "MINFO", -- mailbox or mail list information,[RFC1035],,

	[15] = "MX", -- mail exchange,[RFC1035],,

	[16] = "TXT", -- text strings,[RFC1035],,

	[17] = "RP", -- for Responsible Person,[RFC1183],,

	[18] = "AFSDB", -- for AFS Data Base location,[RFC1183][RFC5864],,

	[19] = "X25", -- for X.25 PSDN address,[RFC1183],,

	[20] = "ISDN", -- for ISDN address,[RFC1183],,

	[21] = "RT", -- for Route Through,[RFC1183],,

	[22] = "NSAP", -- "for NSAP address, NSAP style A record",[RFC1706],,

	[23] = "NSAP-PTR", -- "for domain name pointer, NSAP style",[RFC1348][RFC1637][RFC1706],,

	[24] = "SIG", -- for security signature,[RFC4034][RFC3755][RFC2535][RFC2536][RFC2537][RFC2931][RFC3110][RFC3008],,

	[25] = "KEY", -- for security key,[RFC4034][RFC3755][RFC2535][RFC2536][RFC2537][RFC2539][RFC3008][RFC3110],,

	[26] = "PX", -- X.400 mail mapping information,[RFC2163],,

	[27] = "GPOS", -- Geographical Position,[RFC1712],,

	[28] = "AAAA", -- IP6 Address,[RFC3596],,

	[29] = "LOC", -- Location Information,[RFC1876],,

	[30] = "NXT", -- Next Domain (OBSOLETE),[RFC3755][RFC2535],,

	[31] = "EID", -- Endpoint Identifier,[Michael_Patton][http://ana-3.lcs.mit.edu/~jnc/nimrod/dns.txt],,1995-06

	[32] = "NIMLOC", -- Nimrod Locator,[1][Michael_Patton][http://ana-3.lcs.mit.edu/~jnc/nimrod/dns.txt],,1995-06

	[33] = "SRV", -- Server Selection,[1][RFC2782],,

	[34] = "ATMA", -- ATM Address,"[ ATM Forum Technical Committee, ""ATM Name System, V2.0"", Doc ID: AF-DANS-0152.000, July 2000. Available from and held in escrow by IANA.]",,

	[35] = "NAPTR", -- Naming Authority Pointer,[RFC2915][RFC2168][RFC3403],,

	[36] = "KX", -- Key Exchanger,[RFC2230],,

	[37] = "CERT", -- CERT,[RFC4398],,

	[38] = "A6", -- A6 (OBSOLETE - use AAAA),[RFC3226][RFC2874][RFC6563],,

	[39] = "DNAME", -- DNAME,[RFC6672],,

	[40] = "SINK", -- SINK,[Donald_E_Eastlake][http://tools.ietf.org/html/draft-eastlake-kitchen-sink],,1997-11

	[41] = "OPT", -- OPT,[RFC6891][RFC3225],,

	[42] = "APL", -- APL,[RFC3123],,

	[43] = "DS", -- Delegation Signer,[RFC4034][RFC3658],,

	[44] = "SSHFP", -- SSH Key Fingerprint,[RFC4255],,

	[45] = "IPSECKEY", -- IPSECKEY,[RFC4025],,

	[46] = "RRSIG", -- RRSIG,[RFC4034][RFC3755],,

	[47] = "NSEC", -- NSEC,[RFC4034][RFC3755],,

	[48] = "DNSKEY", -- DNSKEY,[RFC4034][RFC3755],,

	[49] = "DHCID", -- DHCID,[RFC4701],,

	[50] = "NSEC3", -- NSEC3,[RFC5155],,

	[51] = "NSEC3PARAM", -- NSEC3PARAM,[RFC5155],,

	[52] = "TLSA", -- TLSA,[RFC6698],,

	[53] = "SMIMEA", -- S/MIME cert association,[RFC8162],SMIMEA/smimea-completed-template,2015-12-01

	-- [54] = "Unassigned", -- ,,,

	[55] = "HIP", -- Host Identity Protocol,[RFC8005],,

	[56] = "NINFO", -- NINFO,[Jim_Reid],NINFO/ninfo-completed-template,2008-01-21

	[57] = "RKEY", -- RKEY,[Jim_Reid],RKEY/rkey-completed-template,2008-01-21

	[58] = "TALINK", -- Trust Anchor LINK,[Wouter_Wijngaards],TALINK/talink-completed-template,2010-02-17

	[59] = "CDS", -- Child DS,[RFC7344],CDS/cds-completed-template,2011-06-06

	[60] = "CDNSKEY", -- DNSKEY(s) the Child wants reflected in DS,[RFC7344],,2014-06-16

	[61] = "OPENPGPKEY", -- OpenPGP Key,[RFC7929],OPENPGPKEY/openpgpkey-completed-template,2014-08-12

	[62] = "CSYNC", -- Child-To-Parent Synchronization,[RFC7477],,2015-01-27

	-- [63 .. 98] = "Unassigned", -- ,,,

	[99] = "SPF", -- ,[RFC7208],,

	[100] = "UINFO", -- ,[IANA-Reserved],,

	[101] = "UID", -- ,[IANA-Reserved],,

	[102] = "GID", -- ,[IANA-Reserved],,

	[103] = "UNSPEC", -- ,[IANA-Reserved],,

	[104] = "NID", -- ,[RFC6742],ILNP/nid-completed-template,

	[105] = "L32", -- ,[RFC6742],ILNP/l32-completed-template,

	[106] = "L64", -- ,[RFC6742],ILNP/l64-completed-template,

	[107] = "LP", -- ,[RFC6742],ILNP/lp-completed-template,

	[108] = "EUI48", -- an EUI-48 address,[RFC7043],EUI48/eui48-completed-template,2013-03-27

	[109] = "EUI64", -- an EUI-64 address,[RFC7043],EUI64/eui64-completed-template,2013-03-27

	-- [110 .. 248] = "Unassigned", -- ,,,

	[249] = "TKEY", -- Transaction Key,[RFC2930],,

	[250] = "TSIG", -- Transaction Signature,[RFC2845],,

	[251] = "IXFR", -- incremental transfer,[RFC1995],,

	[252] = "AXFR", -- transfer of an entire zone,[RFC1035][RFC5936],,

	[253] = "MAILB", -- "mailbox-related RRs (MB, MG or MR)",[RFC1035],,

	[254] = "MAILA", -- mail agent RRs (OBSOLETE - see MX),[RFC1035],,

	[255] = "*", -- A request for all records the server/cache has available,[RFC1035][RFC6895],,

	[256] = "URI", -- URI,[RFC7553],URI/uri-completed-template,2011-02-22

	[257] = "CAA", -- Certification Authority Restriction,[RFC6844],CAA/caa-completed-template,2011-04-07

	[258] = "AVC", -- Application Visibility and Control,[Wolfgang_Riedel],AVC/avc-completed-template,2016-02-26

	[259] = "DOA", -- Digital Object Architecture,[draft-durand-doa-over-dns],DOA/doa-completed-template,2017-08-30

	-- [260 .. 32767] = "Unassigned", -- ,,,

	[32768] = "TA", -- DNSSEC Trust Authorities,"[Sam_Weiler][http://cameo.library.cmu.edu/][ Deploying DNSSEC Without a Signed Root.  Technical Report 1999-19, Information Networking Institute, Carnegie Mellon University, April 2004.]",,2005-12-13

	[32769] = "DLV", -- DNSSEC Lookaside Validation,[RFC4431],,

	-- [32770 .. 65279] = "Unassigned", -- ,,,

	-- [65280 .. 65534] = "Private use", -- ,,,

	-- [65535] = "Reserved", -- ,,,

}

dns.classes = { 'IN', 'CS', 'CH', 'HS', [255] = '*' };

dns.type      = augment (dns.types, "TYPE");

dns.class     = augment (dns.classes, "CLASS");

dns.typecode  = encode  (dns.types);

dns.classcode = encode  (dns.classes);

local function standardize(qname, qtype, qclass)    -- - - - - - - standardize

	if string.byte(qname, -1) ~= 0x2E then qname = qname..'.';  end

	qname = string.lower(qname);

	return qname, dns.type[qtype or 'A'], dns.class[qclass or 'IN'];

end

local function prune(rrs, time, soft)    -- - - - - - - - - - - - - - -  prune

	time = time or socket.gettime();

	for i,rr in ipairs(rrs) do

		if rr.tod then

			if rr.tod < time then

				rrs[rr[rr.type:lower()]] = nil;

				table.remove(rrs, i);

				return prune(rrs, time, soft); -- Re-iterate

			end

		elseif soft == 'soft' then    -- What is this?  I forget!

			assert(rr.ttl == 0);

			rrs[rr[rr.type:lower()]] = nil;

			table.remove(rrs, i);

		end

	end

end

-- metatables & co. ------------------------------------------ metatables & co.

local resolver = {};

resolver.__index = resolver;

resolver.timeout = default_timeout;

local function default_rr_tostring(rr)

	local rr_val = rr.type and rr[rr.type:lower()];

	if type(rr_val) ~= "string" then

		return "<UNKNOWN RDATA TYPE>";

	end

	return rr_val;

end

local special_tostrings = {

	LOC = resolver.LOC_tostring;

	MX  = function (rr)

		return string.format('%2i %s', rr.pref, rr.mx);

	end;

	SRV = function (rr)

		local s = rr.srv;

		return string.format('%5d %5d %5d %s', s.priority, s.weight, s.port, s.target);

	end;

};

local rr_metatable = {};   -- - - - - - - - - - - - - - - - - - -  rr_metatable

function rr_metatable.__tostring(rr)

	local rr_string = (special_tostrings[rr.type] or default_rr_tostring)(rr);

	return string.format('%2s %-5s %6i %-28s %s', rr.class, rr.type, rr.ttl, rr.name, rr_string);

end

local rrs_metatable = {};    -- - - - - - - - - - - - - - - - - -  rrs_metatable

function rrs_metatable.__tostring(rrs)

	local t = {};

	for _, rr in ipairs(rrs) do

		append(t, tostring(rr)..'\n');

	end

	return table.concat(t);

end

local cache_metatable = {};    -- - - - - - - - - - - - - - - -  cache_metatable

function cache_metatable.__tostring(cache)

	local time = socket.gettime();

	local t = {};

	for class,types in pairs(cache) do

		for type,names in pairs(types) do

			for name,rrs in pairs(names) do

				prune(rrs, time);

				append(t, tostring(rrs));

			end

		end

	end

	return table.concat(t);

end

-- packet layer -------------------------------------------------- packet layer

function dns.random(...)    -- - - - - - - - - - - - - - - - - - -  dns.random

	math.randomseed(math.floor(10000*socket.gettime()) % 0x80000000);

	dns.random = math.random;

	return dns.random(...);

end

local function encodeHeader(o)    -- - - - - - - - - - - - - - -  encodeHeader

	o = o or {};

	o.id = o.id or dns.random(0, 0xffff); -- 16b	(random) id

	o.rd = o.rd or 1;		--  1b  1 recursion desired

	o.tc = o.tc or 0;		--  1b	1 truncated response

	o.aa = o.aa or 0;		--  1b	1 authoritative response

	o.opcode = o.opcode or 0;	--  4b	0 query

				--  1 inverse query

				--	2 server status request

				--	3-15 reserved

	o.qr = o.qr or 0;		--  1b	0 query, 1 response

	o.rcode = o.rcode or 0;	--  4b  0 no error

				--	1 format error

				--	2 server failure

				--	3 name error

				--	4 not implemented

				--	5 refused

				--	6-15 reserved

	o.z = o.z  or 0;		--  3b  0 reserved

	o.ra = o.ra or 0;		--  1b  1 recursion available

	o.qdcount = o.qdcount or 1;	-- 16b	number of question RRs

	o.ancount = o.ancount or 0;	-- 16b	number of answers RRs

	o.nscount = o.nscount or 0;	-- 16b	number of nameservers RRs

	o.arcount = o.arcount or 0;	-- 16b  number of additional RRs

	-- string.char() rounds, so prevent roundup with -0.4999

	local header = string.char(

		highbyte(o.id), o.id %0x100,

		o.rd + 2*o.tc + 4*o.aa + 8*o.opcode + 128*o.qr,

		o.rcode + 16*o.z + 128*o.ra,

		highbyte(o.qdcount),  o.qdcount %0x100,

		highbyte(o.ancount),  o.ancount %0x100,

		highbyte(o.nscount),  o.nscount %0x100,

		highbyte(o.arcount),  o.arcount %0x100

	);

	return header, o.id;

end