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.

1 files changed, 90 insertions, 0 deletions

diff --git a/net/tls_luasec.lua b/net/tls_luasec.lua
new file mode 100644
index 00000000..680b455e
--- /dev/null
+++ b/net/tls_luasec.lua
@@ -0,0 +1,90 @@
+-- Prosody IM
+-- Copyright (C) 2021 Prosody folks
+--
+-- This project is MIT/X11 licensed. Please see the
+-- COPYING file in the source package for more information.
+--
+
+--[[
+This file provides a shim abstraction over LuaSec, consolidating some code
+which was previously spread between net.server backends, portmanager and
+certmanager.
+
+The goal is to provide a more or less well-defined API on top of LuaSec which
+abstracts away some of the things which are not needed and simplifies usage of
+commonly used things (such as SNI contexts). Eventually, network backends
+which do not rely on LuaSocket+LuaSec should be able to provide *this* API
+instead of having to mimic LuaSec.
+]]
+local softreq = require"util.dependencies".softreq;
+local ssl = softreq"ssl";
+local ssl_newcontext = ssl.newcontext;
+local ssl_context = ssl.context or softreq"ssl.context";
+local io_open = io.open;
+
+local context_api = {};
+local context_mt = {__index = context_api};
+
+function context_api:set_sni_host(host, cert, key)
+	local ctx, err = self._builder:clone():apply({
+		certificate = cert,
+		key = key,
+	}):build();
+	if not ctx then
+		return false, err
+	end
+
+	self._sni_contexts[host] = ctx._inner
+
+	return true, nil
+end
+
+function context_api:remove_sni_host(host)
+	self._sni_contexts[host] = nil
+end
+
+function context_api:wrap(sock)
+	local ok, conn, err = pcall(ssl.wrap, sock, self._inner);
+	if not ok then
+		return nil, err
+	end
+	return conn, nil
+end
+
+local function new_context(cfg, builder)
+	-- LuaSec expects dhparam to be a callback that takes two arguments.
+	-- We ignore those because it is mostly used for having a separate
+	-- set of params for EXPORT ciphers, which we don't have by default.
+	if type(cfg.dhparam) == "string" then
+		local f, err = io_open(cfg.dhparam);
+		if not f then return nil, "Could not open DH parameters: "..err end
+		local dhparam = f:read("*a");
+		f:close();
+		cfg.dhparam = function() return dhparam; end
+	end
+
+	local inner, err = ssl_newcontext(cfg);
+	if not inner then
+		return nil, err
+	end
+
+	-- COMPAT Older LuaSec ignores the cipher list from the config, so we have to take care
+	-- of it ourselves (W/A for #x)
+	if inner and cfg.ciphers then
+		local success;
+		success, err = ssl_context.setcipher(inner, cfg.ciphers);
+		if not success then
+			return nil, err
+		end
+	end
+
+	return setmetatable({
+		_inner = inner,
+		_builder = builder,
+		_sni_contexts = {},
+	}, context_mt), nil
+end
+
+return {
+	new_context = new_context,
+};