File

net/resolvers/basic.lua @ 13107:9c4dc1e6d2c9

mod_http: Add way to retrieve internal URL instead of external This could be of help when configuring reverse proxies, as it is the internal URL the proxy must point at. Argument treated as an enum "internal" "external"(default) to allow for future extensibility.
author Kim Alvefur <zash@zash.se>
date Wed, 24 May 2023 14:43:45 +0200
parent 12974:ba409c67353b
line wrap: on
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local adns = require "prosody.net.adns";
local inet_pton = require "prosody.util.net".pton;
local inet_ntop = require "prosody.util.net".ntop;
local idna_to_ascii = require "prosody.util.encodings".idna.to_ascii;
local promise = require "prosody.util.promise";
local t_move = require "prosody.util.table".move;

local methods = {};
local resolver_mt = { __index = methods };

-- FIXME RFC 6724

local function do_dns_lookup(self, dns_resolver, record_type, name, allow_insecure)
	return promise.new(function (resolve, reject)
		local ipv = (record_type == "A" and "4") or (record_type == "AAAA" and "6") or nil;
		if ipv and self.extra["use_ipv"..ipv] == false then
			return reject(("IPv%s disabled - %s lookup skipped"):format(ipv, record_type));
		elseif record_type == "TLSA" and self.extra.use_dane ~= true then
			return reject("DANE disabled - TLSA lookup skipped");
		end
		dns_resolver:lookup(function (answer, err)
			if not answer then
				return reject(err);
			elseif answer.bogus then
				return reject(("Validation error in %s lookup"):format(record_type));
			elseif not (answer.secure or allow_insecure) then
				return reject(("Insecure response in %s lookup"):format(record_type));
			elseif answer.status and #answer == 0 then
				return reject(("%s in %s lookup"):format(answer.status, record_type));
			end

			local targets = { secure = answer.secure };
			for _, record in ipairs(answer) do
				if ipv then
					table.insert(targets, { self.conn_type..ipv, record[record_type:lower()], self.port, self.extra });
				else
					table.insert(targets, record[record_type:lower()]);
				end
			end
			return resolve(targets);
		end, name, record_type, "IN");
	end);
end

local function merge_targets(ipv4_targets, ipv6_targets)
	local result = { secure = ipv4_targets.secure and ipv6_targets.secure };
	local common_length = math.min(#ipv4_targets, #ipv6_targets);
	for i = 1, common_length do
		table.insert(result, ipv6_targets[i]);
		table.insert(result, ipv4_targets[i]);
	end
	if common_length < #ipv4_targets then
		t_move(ipv4_targets, common_length+1, #ipv4_targets, common_length+1, result);
	elseif common_length < #ipv6_targets then
		t_move(ipv6_targets, common_length+1, #ipv6_targets, common_length+1, result);
	end
	return result;
end

-- Find the next target to connect to, and
-- pass it to cb()
function methods:next(cb)
	if self.targets then
		if #self.targets == 0 then
			cb(nil);
			return;
		end
		local next_target = table.remove(self.targets, 1);
		cb(next_target[1], next_target[2], next_target[3], next_target[4], not not self.targets[1]);
		return;
	end

	if not self.hostname then
		self.last_error = "hostname failed IDNA";
		cb(nil);
		return;
	end

	-- Resolve DNS to target list
	local dns_resolver = adns.resolver();

	local dns_lookups = {
		ipv4 = do_dns_lookup(self, dns_resolver, "A", self.hostname, true);
		ipv6 = do_dns_lookup(self, dns_resolver, "AAAA", self.hostname, true);
		tlsa = do_dns_lookup(self, dns_resolver, "TLSA", ("_%d._%s.%s"):format(self.port, self.conn_type, self.hostname));
	};

	promise.all_settled(dns_lookups):next(function (dns_results)
		-- Combine targets, assign to self.targets, self:next(cb)
		local have_ipv4 = dns_results.ipv4.status == "fulfilled";
		local have_ipv6 = dns_results.ipv6.status == "fulfilled";

		if have_ipv4 and have_ipv6 then
			self.targets = merge_targets(dns_results.ipv4.value, dns_results.ipv6.value);
		elseif have_ipv4 then
			self.targets = dns_results.ipv4.value;
		elseif have_ipv6 then
			self.targets = dns_results.ipv6.value;
		else
			self.targets = {};
		end

		if self.extra and self.extra.use_dane then
			if self.targets.secure and dns_results.tlsa.status == "fulfilled" then
				self.extra.tlsa = dns_results.tlsa.value;
				self.extra.dane_hostname = self.hostname;
			else
				self.extra.tlsa = nil;
				self.extra.dane_hostname = nil;
			end
		elseif self.extra and self.extra.srv_secure then
			self.extra.secure_hostname = self.hostname;
		end

		self:next(cb);
	end):catch(function (err)
		self.last_error = err;
		self.targets = {};
	end);
end

local function new(hostname, port, conn_type, extra)
	local ascii_host = idna_to_ascii(hostname);
	local targets = nil;
	conn_type = conn_type or "tcp";

	local is_ip = inet_pton(hostname);
	if not is_ip and hostname:sub(1,1) == '[' then
		is_ip = inet_pton(hostname:sub(2,-2));
	end
	if is_ip then
		hostname = inet_ntop(is_ip);
		if #is_ip == 16 then
			targets = { { conn_type.."6", hostname, port, extra } };
		elseif #is_ip == 4 then
			targets = { { conn_type.."4", hostname, port, extra } };
		end
	end

	return setmetatable({
		hostname = ascii_host;
		port = port;
		conn_type = conn_type;
		extra = extra or {};
		targets = targets;
	}, resolver_mt);
end

return {
	new = new;
};