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spec/util_xmppstream_spec.lua @ 13801:a5d5fefb8b68 13.0

mod_tls: Enable Prosody's certificate checking for incoming s2s connections (fixes #1916) (thanks Damian, Zash) Various options in Prosody allow control over the behaviour of the certificate verification process For example, some deployments choose to allow falling back to traditional "dialback" authentication (XEP-0220), while others verify via DANE, hard-coded fingerprints, or other custom plugins. Implementing this flexibility requires us to override OpenSSL's default certificate verification, to allow Prosody to verify the certificate itself, apply custom policies and make decisions based on the outcome. To enable our custom logic, we have to suppress OpenSSL's default behaviour of aborting the connection with a TLS alert message. With LuaSec, this can be achieved by using the verifyext "lsec_continue" flag. We also need to use the lsec_ignore_purpose flag, because XMPP s2s uses server certificates as "client" certificates (for mutual TLS verification in outgoing s2s connections). Commit 99d2100d2918 moved these settings out of the defaults and into mod_s2s, because we only really need these changes for s2s, and they should be opt-in, rather than automatically applied to all TLS services we offer. That commit was incomplete, because it only added the flags for incoming direct TLS connections. StartTLS connections are handled by mod_tls, which was not applying the lsec_* flags. It previously worked because they were already in the defaults. This resulted in incoming s2s connections with "invalid" certificates being aborted early by OpenSSL, even if settings such as `s2s_secure_auth = false` or DANE were present in the config. Outgoing s2s connections inherit verify "none" from the defaults, which means OpenSSL will receive the cert but will not terminate the connection when it is deemed invalid. This means we don't need lsec_continue there, and we also don't need lsec_ignore_purpose (because the remote peer is a "server"). Wondering why we can't just use verify "none" for incoming s2s? It's because in that mode, OpenSSL won't request a certificate from the peer for incoming connections. Setting verify "peer" is how you ask OpenSSL to request a certificate from the client, but also what triggers its built-in verification.
author Matthew Wild <mwild1@gmail.com>
date Tue, 01 Apr 2025 17:26:56 +0100
parent 9021:548ba4090012
line wrap: on
line source


local xmppstream = require "util.xmppstream";

describe("util.xmppstream", function()
	local function test(xml, expect_success, ex)
		local stanzas = {};
		local session = { notopen = true };
		local callbacks = {
			stream_ns = "streamns";
			stream_tag = "stream";
			default_ns = "stanzans";
			streamopened = function (_session)
				assert.are.equal(session, _session);
				assert.are.equal(session.notopen, true);
				_session.notopen = nil;
				return true;
			end;
			handlestanza = function (_session, stanza)
				assert.are.equal(session, _session);
				assert.are.equal(_session.notopen, nil);
				table.insert(stanzas, stanza);
			end;
			streamclosed = function (_session)
				assert.are.equal(session, _session);
				assert.are.equal(_session.notopen, nil);
				_session.notopen = nil;
			end;
		}
		if type(ex) == "table" then
			for k, v in pairs(ex) do
				if k ~= "_size_limit" then
					callbacks[k] = v;
				end
			end
		end
		local stream = xmppstream.new(session, callbacks, ex and ex._size_limit or nil);
		local ok, err = pcall(function ()
			assert(stream:feed(xml));
		end);

		if ok and type(expect_success) == "function" then
			expect_success(stanzas);
		end
		assert.are.equal(not not ok, not not expect_success, "Expected "..(expect_success and ("success ("..tostring(err)..")") or "failure"));
	end

	local function test_stanza(stanza, expect_success, ex)
		return test([[<stream:stream xmlns:stream="streamns" xmlns="stanzans">]]..stanza, expect_success, ex);
	end

	describe("#new()", function()
		it("should work", function()
			test([[<stream:stream xmlns:stream="streamns"/>]], true);
			test([[<stream xmlns="streamns"/>]], true);

			-- Incorrect stream tag name should be rejected
			test([[<stream1 xmlns="streamns"/>]], false);
			-- Incorrect stream namespace should be rejected
			test([[<stream xmlns="streamns1"/>]], false);
			-- Invalid XML should be rejected
			test("<>", false);

			test_stanza("<message/>", function (stanzas)
				assert.are.equal(#stanzas, 1);
				assert.are.equal(stanzas[1].name, "message");
			end);
			test_stanza("< message>>>>/>\n", false);

			test_stanza([[<x xmlns:a="b">
				<y xmlns:a="c">
					<a:z/>
				</y>
				<a:z/>
			</x>]], function (stanzas)
				assert.are.equal(#stanzas, 1);
				local s = stanzas[1];
				assert.are.equal(s.name, "x");
				assert.are.equal(#s.tags, 2);

				assert.are.equal(s.tags[1].name, "y");
				assert.are.equal(s.tags[1].attr.xmlns, nil);

				assert.are.equal(s.tags[1].tags[1].name, "z");
				assert.are.equal(s.tags[1].tags[1].attr.xmlns, "c");

				assert.are.equal(s.tags[2].name, "z");
				assert.are.equal(s.tags[2].attr.xmlns, "b");

				assert.are.equal(s.namespaces, nil);
			end);
		end);
	end);

	it("should allow an XML declaration", function ()
		test([[<?xml version="1.0" encoding="UTF-8"?><stream xmlns="streamns"/>]], true);
		test([[<?xml version="1.0" encoding="UTF-8" standalone="yes" ?><stream xmlns="streamns"/>]], true);
		test([[<?xml version="1.0" encoding="utf-8" ?><stream xmlns="streamns"/>]], true);
	end);

	it("should not accept XML versions other than 1.0", function ()
		test([[<?xml version="1.1" encoding="utf-8" ?><stream xmlns="streamns"/>]], false);
	end);

	it("should not allow a misplaced XML declaration", function ()
		test([[<stream xmlns="streamns"><?xml version="1.0" encoding="UTF-8"?></stream>]], false);
	end);

	describe("should forbid restricted XML:", function ()
		it("comments", function ()
			test_stanza("<!-- hello world -->", false);
		end);
		it("DOCTYPE", function ()
			test([[<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE stream SYSTEM "mydtd.dtd">]], false);
		end);
		it("incorrect encoding specification", function ()
			-- This is actually caught by the underlying XML parser
			test([[<?xml version="1.0" encoding="UTF-16"?><stream xmlns="streamns"/>]], false);
		end);
		it("non-UTF8 encodings: ISO-8859-1", function ()
			test([[<?xml version="1.0" encoding="ISO-8859-1"?><stream xmlns="streamns"/>]], false);
		end);
		it("non-UTF8 encodings: UTF-16", function ()
			-- <?xml version="1.0" encoding="UTF-16"?><stream xmlns="streamns"/>
			-- encoded into UTF-16
			local hx = ([[fffe3c003f0078006d006c002000760065007200730069006f006e003d00
			220031002e0030002200200065006e0063006f00640069006e0067003d00
			22005500540046002d003100360022003f003e003c007300740072006500
			61006d00200078006d006c006e0073003d00220073007400720065006100
			6d006e00730022002f003e00]]):gsub("%x%x", function (c) return string.char(tonumber(c, 16)); end);
			test(hx, false);
		end);
		it("processing instructions", function ()
			test([[<stream xmlns="streamns"><?xml-stylesheet type="text/xsl" href="style.xsl"?></stream>]], false);
		end);
	end);
end);