Implement mTLS authentication between client and server

.gitignore

@@ -0,0 +1 @@
+test/*

client/config.vapi

@@ -0,0 +1,4 @@
+[CCode (cheader_filename = "config.h")]
+namespace Config {
+    public const string CERT_DIR;
+}

client/main.vala

@@ -1,29 +1,41 @@
 using Gtk;
 
 public class Connection {
-	private InetSocketAddress host;
 	public signal void response_received(uint8[] response);
 
-	public Connection() {
+	private TlsClientConnection tls_client;
+
+	public Connection() throws Error {
 		var loopback = new InetAddress.loopback(SocketFamily.IPV6);
-		host = new InetSocketAddress(loopback, 12888);
+		var host = new InetSocketAddress(loopback, 12888);
+
+		var db_type = TlsBackend.get_default().get_file_database_type();
+		const string ca_path = Config.CERT_DIR + "/ca.pem";
+		var db = Object.new(db_type, "anchors", ca_path) as TlsDatabase;
+		var cert =
+			new TlsCertificate.from_file(Config.CERT_DIR + "/client.pem");
+
+		var plain_client = new SocketClient();
+		var plain_connection = plain_client.connect(host);
+		tls_client = TlsClientConnection.new(plain_connection, host);
+
+		tls_client.set_database(db);
+		tls_client.set_certificate(cert);
+		tls_client.handshake();
 	}
 
 	public async void send(uint8[] message) throws Error {
-		var client = new SocketClient();
-		var conn = yield client.connect_async(host);
-		yield conn.output_stream.write_async(message);
-
+		yield tls_client.output_stream.write_async(message);
 		var response = new uint8[1024];
-		var len = yield conn.input_stream.read_async(response);
+		var len = yield tls_client.input_stream.read_async(response);
 		response_received(response[0:len]);
 	}
 }
 
 public class MainWindow : Gtk.ApplicationWindow {
 	private Connection connection;
+	private Gtk.Button send_button;
 	private Gtk.Label response_label;
-	private Gtk.Button connect_button;
 
 	public MainWindow(Gtk.Application app, Connection connection) {
 		Object(application: app);
@@ -35,7 +47,7 @@ public class MainWindow : Gtk.ApplicationWindow {
 		this.connection = connection;
 		connection.response_received.connect((response) => {
 				response_label.label = "Response: " + (string)response;
-		});
+			});
 
 		var box = new Gtk.Box(Gtk.Orientation.VERTICAL, 10);
 		box.margin_start = 10;
@@ -43,9 +55,9 @@ public class MainWindow : Gtk.ApplicationWindow {
 		box.margin_top = 10;
 		box.margin_bottom = 10;
 
-		connect_button = new Gtk.Button.with_label("Foo");
-		connect_button.clicked.connect(on_connect_clicked);
-		box.append(connect_button);
+		send_button = new Gtk.Button.with_label("Send");
+		send_button.clicked.connect(on_send_clicked);
+		box.append(send_button);
 
 		response_label = new Gtk.Label("");
 		response_label.wrap = true;
@@ -56,9 +68,9 @@ public class MainWindow : Gtk.ApplicationWindow {
 		present();
 	}
 
-	private async void on_connect_clicked() {
+	private async void on_send_clicked() {
 		try {
-			yield connection.send("Bar".data);
+			yield connection.send("Foo".data);
 		} catch (Error e) {
 			response_label.label = "Error: " + e.message;
 		}
@@ -71,8 +83,13 @@ public class StudySystemClient : Gtk.Application {
 	}
 
 	protected override void activate() {
-		var connection = new Connection();
-		new MainWindow(this, connection);
+		try {
+			var connection = new Connection();
+			new MainWindow(this, connection);
+		} catch (Error e) {
+			stderr.printf("Failed to initialize connection: %s\n",
+						  e.message);
+		}
 	}
 
 	public static int main(string[] args) {

client/meson.build

@@ -10,9 +10,21 @@ add_project_arguments('-w', language: 'c')
 
 gtk_dep = dependency('gtk4')
 
+conf = configuration_data()
+conf.set_quoted(
+  'CONFIG_CERT_DIR',
+  join_paths(meson.project_source_root(), '..', 'test'))
+configure_file(
+  output: 'config.h',
+  configuration: conf
+)
+
 exe = executable(
   'study-system-client',
-  'main.vala',
+  [
+    'main.vala',
+    'config.vapi'
+  ],
   dependencies: [gtk_dep],
   c_args: ['-w']
 )

scripts/make-test-certs.sh

@@ -0,0 +1,76 @@
+#!/bin/sh
+set -eu
+
+mkdir -p test
+
+# Create CA config
+cat > test/ca.cnf << EOF
+[req]
+distinguished_name = req_distinguished_name
+x509_extensions = v3_ca
+
+[req_distinguished_name]
+commonName = Study System CA
+
+[v3_ca]
+basicConstraints = critical,CA:TRUE
+keyUsage = critical,keyCertSign,cRLSign
+EOF
+
+# Create CA key and certificate
+openssl genrsa -out test/ca.key 4096
+openssl req -new -x509 -key test/ca.key -outform PEM -out test/ca.pem \
+		-config test/ca.cnf
+
+# Create server key and CSR
+cat > test/server.cnf << EOF
+[req]
+distinguished_name = req_distinguished_name
+req_extensions = v3_req
+
+[req_distinguished_name]
+commonName = localhost
+
+[v3_req]
+basicConstraints = CA:FALSE
+keyUsage = nonRepudiation,digitalSignature,keyEncipherment
+subjectAltName = @alt_names
+
+[alt_names]
+IP.1 = ::1
+DNS.1 = localhost
+EOF
+openssl genrsa -out test/server.key 4096
+openssl req -new -key test/server.key -out test/server.csr \
+		-config test/server.cnf
+
+# Sign server certificate
+openssl x509 -req -in test/server.csr -CA test/ca.pem -CAkey test/ca.key \
+		-CAcreateserial -out test/server_cert.pem \
+		-extensions v3_req -extfile test/server.cnf
+
+# Create client key and CSR
+cat > test/client.cnf << EOF
+[req]
+distinguished_name = req_distinguished_name
+req_extensions = v3_req
+
+[req_distinguished_name]
+commonName = Study System Client
+
+[v3_req]
+basicConstraints = critical,CA:FALSE
+keyUsage = critical,digitalSignature,keyEncipherment
+EOF
+openssl genrsa -out test/client.key 4096
+openssl req -new -key test/client.key -out test/client.csr \
+		-config test/client.cnf
+
+# Sign client certificate
+openssl x509 -req -in test/client.csr -CA test/ca.pem -CAkey test/ca.key \
+		-CAcreateserial -outform PEM -out test/client_cert.pem \
+		-extensions v3_req -extfile test/client.cnf
+
+# Create combined files
+cat test/server_cert.pem test/server.key > test/server.pem
+cat test/client_cert.pem test/client.key > test/client.pem

server/src/proto_sup.erl

@@ -4,15 +4,15 @@
 -module(proto_sup).
 -behaviour(supervisor).
 
--export([start_link/1]).
+-export([start_link/2]).
 -export([init/1]).
 
-start_link(Port) ->
-	supervisor:start_link({local, ?MODULE}, ?MODULE, [Port]).
+start_link(Port, CertDir) ->
+	supervisor:start_link({local, ?MODULE}, ?MODULE, [Port, CertDir]).
 
-init([Port]) ->
+init([Port, CertDir]) ->
 	SupFlags = #{stragegy => one_for_all,
 				 intensity => 1,
 				 period => 5},
-	ChildSpecs = [tcp_server:child_spec(Port)],
+	ChildSpecs = [tcp_server:child_spec(Port, CertDir)],
 	{ok, {SupFlags, ChildSpecs}}.

server/src/study_system_server.app.src

@@ -3,8 +3,8 @@
   {vsn, "0.1.0"},
   {registered, []},
   {mod, {study_system_server_app, []}},
-  {applications, [kernel, stdlib]},
-  {env, []},
+  {applications, [kernel, stdlib, ssl]},
+  {env, [{cert_dir, "../test"}]},
   {modules, []},
   {licenses, ["AGPL-3.0-only"]},
   {links, []}]}.

server/src/study_system_server_app.erl

@@ -8,7 +8,8 @@
 
 start(_StartType, _StartArgs) ->
 	Port = application:get_env(study_system_server, port, 12888),
-	proto_sup:start_link(Port).
+	{ok, CertDir} = application:get_env(study_system_server, cert_dir),
+	proto_sup:start_link(Port, CertDir).
 
 stop(_State) ->
 	ok.

server/src/tcp_server.erl

@@ -4,25 +4,31 @@
 -module(tcp_server).
 -behaviour(gen_server).
 
--export([start_link/1, child_spec/1]).
+-export([start_link/2, child_spec/2]).
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
 		 terminate/2, code_change/3]).
 
 -record(state, {socket, acceptor}).
 
-start_link(Port) ->
-	gen_server:start_link({local, ?MODULE}, ?MODULE, [Port], []).
+start_link(Port, CertDir) ->
+	gen_server:start_link({local, ?MODULE}, ?MODULE, [Port, CertDir], []).
 
-child_spec(Port) ->
+child_spec(Port, CertDir) ->
 	#{id => ?MODULE,
-	  start => {?MODULE, start_link, [Port]},
+	  start => {?MODULE, start_link, [Port, CertDir]},
 	  restart => permanent,
 	  shutdown => 5000,
 	  type => worker,
 	  modules => [?MODULE]}.
 
-init([Port]) ->
-	{ok, Socket} = gen_tcp:listen(Port, [binary, inet6, {active, true}]),
+init([Port, CertDir]) ->
+	io:format("cert dir: ~p~n", [CertDir]),
+	SslOpts = [{certfile, filename:join([CertDir, "server.pem"])},
+			   {cacertfile, filename:join([CertDir, "ca.pem"])},
+			   {verify, verify_peer},
+			   {fail_if_no_peer_cert, true}],
+	{ok, Socket} =
+		ssl:listen(Port, [binary, inet6, {active, true} | SslOpts]),
 	Pid = spawn_link(fun() -> acceptor_loop(Socket) end),
 	{ok, #state{socket = Socket, acceptor = Pid}}.
 
@@ -45,21 +51,27 @@ code_change(_OldVsn, State, _Extra) ->
 	{ok, State}.
 
 acceptor_loop(Socket) ->
-	case gen_tcp:accept(Socket) of
-		{ok, ClientSocket} ->
-			gen_tcp:controlling_process(
-			  ClientSocket,
-			  spawn(fun() -> handle_connection(ClientSocket) end)),
-			acceptor_loop(Socket);
+	case ssl:transport_accept(Socket) of
+		{ok, TlsSocket} ->
+			case ssl:handshake(TlsSocket) of
+				{ok, ClientSocket} ->
+					Pid = spawn(
+							fun() -> handle_connection(ClientSocket) end),
+					ok = ssl:controlling_process(ClientSocket, Pid),
+					ssl:setopts(ClientSocket, [{active, true}]),
+					acceptor_loop(Socket);
+				{error, _Reason} ->
+					acceptor_loop(Socket)
+			end;
 		{error, closed} ->
 			ok
 	end.
 
 handle_connection(Socket) ->
 	receive
-		{tcp, Socket, Data} ->
-			gen_tcp:send(Socket, Data),
+		{ssl, Socket, Data} ->
+			ssl:send(Socket, Data),
 			handle_connection(Socket);
-		{tcp_closed, Socket} ->
+		{ssl_closed, Socket} ->
 			ok
 	end.