xK/src/kike.c

/*
 * kike.c: the experimental IRC daemon
 *
 * Copyright (c) 2014, Přemysl Janouch <p.janouch@gmail.com>
 * All rights reserved.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 */

#define PROGRAM_NAME "kike"
#define PROGRAM_VERSION "alpha"

#include "common.c"

// --- Configuration (application-specific) ------------------------------------

static struct config_item g_config_table[] =
{
	{ "server_name",     NULL,              "Server name"                    },
	{ "bind_host",       NULL,              "Address of the IRC server"      },
	{ "bind_port",       "6667",            "Port of the IRC server"         },
	{ "ssl_cert",        NULL,              "Server SSL certificate (PEM)"   },
	{ "ssl_key",         NULL,              "Server SSL private key (PEM)"   },

	{ "max_connections", NULL,              "Maximum client connections"     },
	{ NULL,              NULL,              NULL                             }
};

// --- Signals -----------------------------------------------------------------

static int g_signal_pipe[2];            ///< A pipe used to signal... signals

/// Program termination has been requested by a signal
static volatile sig_atomic_t g_termination_requested;

static void
sigterm_handler (int signum)
{
	(void) signum;

	g_termination_requested = true;

	int original_errno = errno;
	if (write (g_signal_pipe[1], "t", 1) == -1)
		soft_assert (errno == EAGAIN);
	errno = original_errno;
}

static void
setup_signal_handlers (void)
{
	if (pipe (g_signal_pipe) == -1)
	{
		print_fatal ("pipe: %s", strerror (errno));
		exit (EXIT_FAILURE);
	}

	set_cloexec (g_signal_pipe[0]);
	set_cloexec (g_signal_pipe[1]);

	// So that the pipe cannot overflow; it would make write() block within
	// the signal handler, which is something we really don't want to happen.
	// The same holds true for read().
	set_blocking (g_signal_pipe[0], false);
	set_blocking (g_signal_pipe[1], false);

	signal (SIGPIPE, SIG_IGN);

	struct sigaction sa;
	sa.sa_flags = SA_RESTART;
	sigemptyset (&sa.sa_mask);
	sa.sa_handler = sigterm_handler;
	if (sigaction (SIGINT, &sa, NULL) == -1
	 || sigaction (SIGTERM, &sa, NULL) == -1)
	{
		print_error ("sigaction: %s", strerror (errno));
		exit (EXIT_FAILURE);
	}
}

// --- Application data --------------------------------------------------------

enum
{
	IRC_USER_MODE_INVISIBLE          = (1 << 0),
	IRC_USER_MODE_RX_WALLOPS         = (1 << 1),
	IRC_USER_MODE_RESTRICTED         = (1 << 2),
	IRC_USER_MODE_OPERATOR           = (1 << 3),
	IRC_USER_MODE_RX_SERVER_NOTICES  = (1 << 4)
};

struct connection
{
	struct connection *next;            ///< The next link in a chain
	struct connection *prev;            ///< The previous link in a chain

	struct server_context *ctx;         ///< Server context

	int socket_fd;                      ///< The TCP socket
	struct str read_buffer;             ///< Unprocessed input
	struct str write_buffer;            ///< Output yet to be sent out

	unsigned initialized    : 1;        ///< Has any data been received yet?
	unsigned ssl_rx_want_tx : 1;        ///< SSL_read() wants to write
	unsigned ssl_tx_want_rx : 1;        ///< SSL_write() wants to read

	SSL_CTX *ssl_ctx;                   ///< SSL context
	SSL *ssl;                           ///< SSL connection

	char *nickname;                     ///< IRC nickname (main identifier)
	char *username;                     ///< IRC username
	char *fullname;                     ///< IRC fullname (e-mail)

	char *hostname;                     ///< Hostname shown to the network

	unsigned mode;                      ///< User's mode
	char *away_message;                 ///< Away message
};

static void
connection_init (struct connection *self)
{
	memset (self, 0, sizeof *self);

	self->socket_fd = -1;
	str_init (&self->read_buffer);
	str_init (&self->write_buffer);
}

static void
connection_free (struct connection *self)
{
	if (!soft_assert (self->socket_fd == -1))
		xclose (self->socket_fd);
	if (self->ssl_ctx)
		SSL_CTX_free (self->ssl_ctx);
	if (self->ssl)
		SSL_free (self->ssl);

	str_free (&self->read_buffer);
	str_free (&self->write_buffer);

	free (self->nickname);
	free (self->username);
	free (self->fullname);

	free (self->hostname);
	free (self->away_message);
}

enum
{
	IRC_CHAN_MODE_INVITE_ONLY      = (1 << 0),
	IRC_CHAN_MODE_MODERATED        = (1 << 1),
	IRC_CHAN_MODE_NO_OUTSIDE_MSGS  = (1 << 2),
	IRC_CHAN_MODE_SECRET           = (1 << 3),
	IRC_CHAN_MODE_PRIVATE          = (1 << 4),
	IRC_CHAN_MODE_PROTECTED_TOPIC  = (1 << 5),
	IRC_CHAN_MODE_QUIET            = (1 << 6)
};

struct channel
{
	struct server_context *ctx;         ///< Server context

	char *name;                         ///< Channel name
	unsigned modes;                     ///< Channel modes
	char *key;                          ///< Channel key
	long user_limit;                    ///< User limit or -1

	struct str_vector ban_list;         ///< Ban list
	struct str_vector exception_list;   ///< Exceptions from bans
	struct str_vector invite_list;      ///< Exceptions from +I
};

static void
channel_init (struct channel *self)
{
	memset (self, 0, sizeof *self);

	str_vector_init (&self->ban_list);
	str_vector_init (&self->exception_list);
	str_vector_init (&self->invite_list);
}

static void
channel_free (struct channel *self)
{
	free (self->name);
	free (self->key);

	str_vector_free (&self->ban_list);
	str_vector_free (&self->exception_list);
	str_vector_free (&self->invite_list);
}

struct server_context
{
	struct str_map config;              ///< Server configuration

	int listen_fd;                      ///< Listening socket FD
	struct connection *clients;         ///< Client connections

	struct str_map users;               ///< Maps nicknames to connections
	struct str_map channels;            ///< Maps channel names to data

	struct poller poller;               ///< Manages polled description
	bool polling;                       ///< The event loop is running
};

static void
server_context_init (struct server_context *self)
{
	str_map_init (&self->config);
	self->config.free = free;
	load_config_defaults (&self->config, g_config_table);

	self->listen_fd = -1;
	self->clients = NULL;

	str_map_init (&self->users);
	// TODO: set channel_free() as the free function?
	str_map_init (&self->channels);

	poller_init (&self->poller);
	self->polling = false;
}

static void
server_context_free (struct server_context *self)
{
	str_map_free (&self->config);

	if (self->listen_fd != -1)
		xclose (self->listen_fd);

	// TODO: terminate the connections properly before this is called
	struct connection *link, *tmp;
	for (link = self->clients; link; link = tmp)
	{
		tmp = link->next;
		connection_free (link);
		free (link);
	}

	str_map_free (&self->users);
	str_map_free (&self->channels);
	poller_free (&self->poller);
}

// --- Main program ------------------------------------------------------------

static size_t network_error_domain_tag;
#define NETWORK_ERROR (error_resolve_domain (&network_error_domain_tag))

enum
{
	NETWORK_ERROR_INVALID_CONFIGURATION,
	NETWORK_ERROR_FAILED
};

static bool
irc_autodetect_ssl (struct connection *conn)
{
	// Trivial SSL/TLS autodetection.  The first block of data returned by
	// recv() must be at least three bytes long for this to work reliably,
	// but that should not pose a problem in practice.
	//
	// SSL2:      1xxx xxxx | xxxx xxxx |    <1>
	//               (message length)  (client hello)
	// SSL3/TLS:    <22>    |    <3>    | xxxx xxxx
	//           (handshake)|  (protocol version)
	//
	// Such byte sequences should never occur at the beginning of regular IRC
	// communication, which usually begins with USER/NICK/PASS/SERVICE.

	char buf[3];
start:
	switch (recv (conn->socket_fd, buf, sizeof buf, MSG_PEEK))
	{
	case 3:
		if ((buf[0] & 0x80) && buf[2] == 1)
			return true;
	case 2:
		if (buf[0] == 22 && buf[1] == 3)
			return true;
		break;
	case 1:
		if (buf[0] == 22)
			return true;
		break;
	case 0:
		break;
	default:
		if (errno == EINTR)
			goto start;
	}
	return false;
}

static int
irc_ssl_verify_callback (int verify_ok, X509_STORE_CTX *ctx)
{
	(void) verify_ok;
	(void) ctx;

	// We only want to provide additional privileges based on the client's
	// certificate, so let's not terminate the connection because of a failure.
	return 1;
}

static bool
irc_initialize_ssl (struct connection *conn)
{
	struct server_context *ctx = conn->ctx;

	conn->ssl_ctx = SSL_CTX_new (SSLv23_server_method ());
	if (!conn->ssl_ctx)
		goto error_ssl_1;
	SSL_CTX_set_verify (conn->ssl_ctx,
		SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE, irc_ssl_verify_callback);
	// XXX: maybe we should call SSL_CTX_set_options() for some workarounds

	conn->ssl = SSL_new (conn->ssl_ctx);
	if (!conn->ssl)
		goto error_ssl_2;

	const char *ssl_cert = str_map_find (&ctx->config, "ssl_cert");
	if (ssl_cert
	 && !SSL_CTX_use_certificate_chain_file (conn->ssl_ctx, ssl_cert))
	{
		// XXX: perhaps we should read the file ourselves for better messages
		print_error ("%s: %s", "setting the SSL client certificate failed",
			ERR_error_string (ERR_get_error (), NULL));
	}

	const char *ssl_key = str_map_find (&ctx->config, "ssl_key");
	if (ssl_key
	 && !SSL_use_PrivateKey_file (conn->ssl, ssl_key, SSL_FILETYPE_PEM))
	{
		// XXX: perhaps we should read the file ourselves for better messages
		print_error ("%s: %s", "setting the SSL private key failed",
			ERR_error_string (ERR_get_error (), NULL));
	}

	// TODO: SSL_check_private_key(conn->ssl)?  It is has probably already been
	//   checked by SSL_use_PrivateKey_file() above.

	SSL_set_accept_state (conn->ssl);
	if (!SSL_set_fd (conn->ssl, conn->socket_fd))
		goto error_ssl_3;
	// Gah, spare me your awkward semantics, I just want to push data!
	// XXX: do we want SSL_MODE_AUTO_RETRY as well?  I guess not.
	SSL_set_mode (conn->ssl,
		SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER | SSL_MODE_ENABLE_PARTIAL_WRITE);
	return true;

error_ssl_3:
	SSL_free (conn->ssl);
	conn->ssl = NULL;
error_ssl_2:
	SSL_CTX_free (conn->ssl_ctx);
	conn->ssl_ctx = NULL;
error_ssl_1:
	// XXX: these error strings are really nasty; also there could be
	//   multiple errors on the OpenSSL stack.
	print_error ("%s: %s", "could not initialize SSL",
		ERR_error_string (ERR_get_error (), NULL));
	return false;
}

static void
connection_abort (struct connection *conn, const char *reason)
{
	// TODO: send a QUIT message with `reason' || "Client exited"
	(void) reason;

	// TODO: do further cleanup if the client has successfully registered

	struct server_context *ctx = conn->ctx;
	ssize_t i = poller_find_by_fd (&ctx->poller, conn->socket_fd);
	if (i != -1)
		poller_remove_at_index (&ctx->poller, i);

	xclose (conn->socket_fd);
	conn->socket_fd = -1;
	connection_free (conn);
	LIST_UNLINK (ctx->clients, conn);
	free (conn);
}

static void
irc_process_message (const struct irc_message *msg,
	const char *raw, void *user_data)
{
	struct connection *conn = user_data;
	// TODO
}

static bool
irc_try_read (struct connection *conn)
{
	// TODO
	return false;
}

static bool
irc_try_read_ssl (struct connection *conn)
{
	if (conn->ssl_tx_want_rx)
		return true;

	struct str *buf = &conn->read_buffer;
	conn->ssl_rx_want_tx = false;
	while (true)
	{
		str_ensure_space (buf, 512);
		int n_read = SSL_read (conn->ssl, buf->str + buf->len,
			buf->alloc - buf->len - 1 /* null byte */);

		const char *error_info = NULL;
		switch (xssl_get_error (conn->ssl, n_read, &error_info))
		{
		case SSL_ERROR_NONE:
			buf->str[buf->len += n_read] = '\0';
			// TODO: discard characters above the 512 character limit
			irc_process_buffer (buf, irc_process_message, conn);
			continue;
		case SSL_ERROR_ZERO_RETURN:
			connection_abort (conn, NULL);
			return false;
		case SSL_ERROR_WANT_READ:
			return true;
		case SSL_ERROR_WANT_WRITE:
			conn->ssl_rx_want_tx = true;
			return false;
		case XSSL_ERROR_TRY_AGAIN:
			continue;
		default:
			print_debug ("%s: %s: %s", __func__, "SSL_read", error_info);
			connection_abort (conn, error_info);
			return false;
		}
	}
}

static bool
irc_try_write (struct connection *conn)
{
	// TODO
	return false;
}

static bool
irc_try_write_ssl (struct connection *conn)
{
	if (conn->ssl_rx_want_tx)
		return true;

	struct str *buf = &conn->write_buffer;
	conn->ssl_tx_want_rx = false;
	while (buf->len)
	{
		int n_written = SSL_write (conn->ssl, buf->str, buf->len);

		const char *error_info = NULL;
		switch (xssl_get_error (conn->ssl, n_written, &error_info))
		{
		case SSL_ERROR_NONE:
			str_remove_slice (buf, 0, n_written);
			continue;
		case SSL_ERROR_ZERO_RETURN:
			connection_abort (conn, NULL);
			return false;
		case SSL_ERROR_WANT_WRITE:
			return true;
		case SSL_ERROR_WANT_READ:
			conn->ssl_tx_want_rx = true;
			return false;
		case XSSL_ERROR_TRY_AGAIN:
			continue;
		default:
			print_debug ("%s: %s: %s", __func__, "SSL_write", error_info);
			connection_abort (conn, error_info);
			return false;
		}
	}
	return true;
}

static void
on_irc_client_ready (const struct pollfd *pfd, void *user_data)
{
	// XXX: check/load `ssl_cert' and `ssl_key' earlier?
	struct connection *conn = user_data;
	if (!conn->initialized)
	{
		hard_assert (pfd->events == POLLIN);
		// XXX: what with the error from irc_initialize_ssl()?
		if (irc_autodetect_ssl (conn) && !irc_initialize_ssl (conn))
		{
			connection_abort (conn, NULL);
			return;
		}
		conn->initialized = true;
	}

	// FIXME: aborting a connection inside try_read() will fuck things up
	int new_events = 0;
	if (conn->ssl)
	{
		// Reads may want to write, writes may want to read, poll() may
		// return unexpected things in `revents'... let's try both
		irc_try_read_ssl (conn) && irc_try_write_ssl (conn);

		new_events |= POLLIN;
		if (conn->write_buffer.len || conn->ssl_rx_want_tx)
			new_events |= POLLOUT;

		// While we're waiting for an opposite event, we ignore the original
		if (conn->ssl_rx_want_tx)  new_events &= ~POLLIN;
		if (conn->ssl_tx_want_rx)  new_events &= ~POLLOUT;
	}
	else
	{
		irc_try_read (conn) && irc_try_write (conn);

		new_events |= POLLIN;
		if (conn->write_buffer.len)
			new_events |= POLLOUT;
	}

	hard_assert (new_events != 0);
	if (pfd->events != new_events)
		poller_set (&conn->ctx->poller, conn->socket_fd, new_events,
			(poller_dispatcher_func) on_irc_client_ready, conn);
}

static void
on_irc_connection_available (const struct pollfd *pfd, void *user_data)
{
	(void) pfd;
	struct server_context *ctx = user_data;

	// TODO: stop accepting new connections when `max_connections' is reached

	while (true)
	{
		// XXX: `struct sockaddr_storage' is not the most portable thing
		struct sockaddr_storage peer;
		socklen_t peer_len = sizeof peer;

		int fd = accept (ctx->listen_fd, (struct sockaddr *) &peer, &peer_len);
		if (fd == -1)
		{
			if (errno == EAGAIN)
				break;
			if (errno == EINTR)
				continue;
			if (errno == ECONNABORTED)
				continue;

			// TODO: handle resource exhaustion (EMFILE, ENFILE) specially
			//   (stop accepting new connections and wait until we close some).
			print_fatal ("%s: %s", "accept", strerror (errno));

			// FIXME: handle this better, bring the server down cleanly.
			exit (EXIT_FAILURE);
		}

		char host[NI_MAXHOST] = "unknown", port[NI_MAXSERV] = "unknown";
		int err = getnameinfo ((struct sockaddr *) &peer, peer_len,
			host, sizeof host, port, sizeof port, AI_NUMERICSERV);
		if (err)
			print_debug ("%s: %s", "getnameinfo", gai_strerror (err));
		print_debug ("accepted connection from %s:%s", host, port);

		struct connection *conn = xmalloc (sizeof *conn);
		connection_init (conn);
		conn->socket_fd = fd;
		conn->hostname = xstrdup (host);
		LIST_PREPEND (ctx->clients, conn);

		// TODO: set a timeout on the socket, something like 3 minutes, then we
		//   should terminate the connection.
		poller_set (&ctx->poller, conn->socket_fd, POLLIN,
			(poller_dispatcher_func) on_irc_client_ready, conn);
	}
}

static bool
irc_listen (struct server_context *ctx, struct error **e)
{
	const char *bind_host = str_map_find (&ctx->config, "bind_host");
	const char *bind_port = str_map_find (&ctx->config, "bind_port");
	hard_assert (bind_port != NULL);  // We have a default value for this

	struct addrinfo gai_hints, *gai_result, *gai_iter;
	memset (&gai_hints, 0, sizeof gai_hints);

	gai_hints.ai_socktype = SOCK_STREAM;
	gai_hints.ai_flags = AI_PASSIVE;

	int err = getaddrinfo (bind_host, bind_port, &gai_hints, &gai_result);
	if (err)
	{
		error_set (e, NETWORK_ERROR, NETWORK_ERROR_FAILED, "%s: %s: %s",
			"network setup failed", "getaddrinfo", gai_strerror (err));
		return false;
	}

	int sockfd;
	char real_host[NI_MAXHOST], real_port[NI_MAXSERV];

	for (gai_iter = gai_result; gai_iter; gai_iter = gai_iter->ai_next)
	{
		sockfd = socket (gai_iter->ai_family,
			gai_iter->ai_socktype, gai_iter->ai_protocol);
		if (sockfd == -1)
			continue;
		set_cloexec (sockfd);

		int yes = 1;
		soft_assert (setsockopt (sockfd, SOL_SOCKET, SO_KEEPALIVE,
			&yes, sizeof yes) != -1);
		soft_assert (setsockopt (sockfd, SOL_SOCKET, SO_REUSEADDR,
			&yes, sizeof yes) != -1);

		real_host[0] = real_port[0] = '\0';
		err = getnameinfo (gai_iter->ai_addr, gai_iter->ai_addrlen,
			real_host, sizeof real_host, real_port, sizeof real_port,
			NI_NUMERICHOST | NI_NUMERICSERV);
		if (err)
			print_debug ("%s: %s", "getnameinfo", gai_strerror (err));

		if (bind (sockfd, gai_iter->ai_addr, gai_iter->ai_addrlen))
			print_error ("bind() to %s:%s failed: %s",
				real_host, real_port, strerror (errno));
		else if (listen (sockfd, 16 /* arbitrary number */))
			print_error ("listen() at %s:%s failed: %s",
				real_host, real_port, strerror (errno));
		else
			break;

		xclose (sockfd);
	}

	freeaddrinfo (gai_result);

	if (!gai_iter)
	{
		error_set (e, NETWORK_ERROR, NETWORK_ERROR_FAILED,
			"network setup failed");
		return false;
	}

	ctx->listen_fd = sockfd;
	poller_set (&ctx->poller, ctx->listen_fd, POLLIN,
		(poller_dispatcher_func) on_irc_connection_available, ctx);

	print_status ("listening at %s:%s", real_host, real_port);
	return true;
}

static void
on_signal_pipe_readable (const struct pollfd *fd, struct server_context *ctx)
{
	char *dummy;
	(void) read (fd->fd, &dummy, 1);

#if 0
	// TODO
	if (g_termination_requested && !ctx->quitting)
	{
		initiate_quit (ctx);
	}
#endif
}

static void
print_usage (const char *program_name)
{
	fprintf (stderr,
		"Usage: %s [OPTION]...\n"
		"Experimental IRC server.\n"
		"\n"
		"  -d, --debug     run in debug mode (do not daemonize)\n"
		"  -h, --help      display this help and exit\n"
		"  -V, --version   output version information and exit\n"
		"  --write-default-cfg [filename]\n"
		"                  write a default configuration file and exit\n",
		program_name);
}

int
main (int argc, char *argv[])
{
	const char *invocation_name = argv[0];

	struct error *e = NULL;
	static struct option opts[] =
	{
		{ "debug",             no_argument,       NULL, 'd' },
		{ "help",              no_argument,       NULL, 'h' },
		{ "version",           no_argument,       NULL, 'V' },
		{ "write-default-cfg", optional_argument, NULL, 'w' },
		{ NULL,                0,                 NULL,  0  }
	};

	while (1)
	{
		int c, opt_index;

		c = getopt_long (argc, argv, "dhV", opts, &opt_index);
		if (c == -1)
			break;

		switch (c)
		{
		case 'd':
			g_debug_mode = true;
			break;
		case 'h':
			print_usage (invocation_name);
			exit (EXIT_SUCCESS);
		case 'V':
			printf (PROGRAM_NAME " " PROGRAM_VERSION "\n");
			exit (EXIT_SUCCESS);
		case 'w':
		{
			char *filename = write_default_config (optarg, g_config_table, &e);
			if (!filename)
			{
				print_fatal ("%s", e->message);
				error_free (e);
				exit (EXIT_FAILURE);
			}
			print_status ("configuration written to `%s'", filename);
			free (filename);
			exit (EXIT_SUCCESS);
		}
		default:
			print_fatal ("error in options");
			exit (EXIT_FAILURE);
		}
	}

	print_status (PROGRAM_NAME " " PROGRAM_VERSION " starting");
	setup_signal_handlers ();

	SSL_library_init ();
	atexit (EVP_cleanup);
	SSL_load_error_strings ();
	// XXX: ERR_load_BIO_strings()?  Anything else?
	atexit (ERR_free_strings);

	struct server_context ctx;
	server_context_init (&ctx);

	if (!read_config_file (&ctx.config, &e))
	{
		print_fatal ("error loading configuration: %s", e->message);
		error_free (e);
		exit (EXIT_FAILURE);
	}

	poller_set (&ctx.poller, g_signal_pipe[0], POLLIN,
		(poller_dispatcher_func) on_signal_pipe_readable, &ctx);

	if (!irc_listen (&ctx, &e))
	{
		print_error ("%s", e->message);
		error_free (e);
		exit (EXIT_FAILURE);
	}

	// TODO: daemonize

	ctx.polling = true;
	while (ctx.polling)
		poller_run (&ctx.poller);

	server_context_free (&ctx);
	return EXIT_SUCCESS;
}