File

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.

local function parse(arg, config)
	local short_params = config and config.short_params or {};
	local value_params = config and config.value_params or {};
	local array_params = config and config.array_params or {};
	local kv_params = config and config.kv_params or {};
	local strict = config and config.strict;
	local stop_on_positional = not config or config.stop_on_positional ~= false;

	local parsed_opts = {};

	if #arg == 0 then
		return parsed_opts;
	end
	while true do
		local raw_param = arg[1];
		if not raw_param then
			break;
		end

		local prefix = raw_param:match("^%-%-?");
		if not prefix and stop_on_positional then
			break;
		elseif prefix == "--" and raw_param == "--" then
			table.remove(arg, 1);
			break;
		end

		if prefix then
			local param = table.remove(arg, 1):sub(#prefix+1);
			if #param == 1 and short_params then
				param = short_params[param];
			end

			if not param then
				return nil, "param-not-found", raw_param;
			end

			local uparam = param:match("^[^=]*"):gsub("%-", "_");

			local param_k, param_v;
			if value_params[uparam] or array_params[uparam] then
				param_k = uparam;
				param_v = param:match("^=(.*)$", #uparam+1);
				if not param_v then
					param_v = table.remove(arg, 1);
					if not param_v then
						return nil, "missing-value", raw_param;
					end
				end
			else
				param_k, param_v = param:match("^([^=]+)=(.+)$");
				if not param_k then
					if param:match("^no%-") then
						param_k, param_v = param:sub(4), false;
					else
						param_k, param_v = param, true;
					end
				end
				param_k = param_k:gsub("%-", "_");
				if strict and not kv_params[param_k] then
					return nil, "param-not-found", raw_param;
				end
			end
			if array_params[uparam] then
				if parsed_opts[param_k] then
					table.insert(parsed_opts[param_k], param_v);
				else
					parsed_opts[param_k] = { param_v };
				end
			else
				parsed_opts[param_k] = param_v;
			end
		elseif not stop_on_positional then
			table.insert(parsed_opts, table.remove(arg, 1));
		end
	end

	if stop_on_positional then
		for i = 1, #arg do
			parsed_opts[i] = arg[i];
		end
	end

	return parsed_opts;
end

return {
	parse = parse;
}