RELAY(1) General Commands Manual RELAY(1)

relay — IRC relay bot

relay host port nick chan

relay is one half of an IRC relay pair. It connects to host:port over TLS as nick and joins chan.

relay outputs messages from chan to standard output and sends messages to chan from standard input. Two relay processes can be connected with mkfifo(1).

mkfifo a b
relay a.example.com 6697 relay '#example' <>a >b
relay b.example.com 6697 relay '#example' <>b >a

mkfifo(1)

April 28, 2019 OpenBSD 7.3

relay.c in git 

/* Copyright (C) 2019  June McEnroe <june@causal.agency>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Additional permission under GNU GPL version 3 section 7:
 *
 * If you modify this Program, or any covered work, by linking or
 * combining it with LibreSSL (or a modified version of that library),
 * containing parts covered by the terms of the OpenSSL License and the
 * original SSLeay license, the licensors of this Program grant you
 * additional permission to convey the resulting work. Corresponding
 * Source for a non-source form of such a combination shall include the
 * source code for the parts of LibreSSL used as well as that of the
 * covered work.
 */

#include <err.h>
#include <netdb.h>
#include <netinet/in.h>
#include <poll.h>
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sysexits.h>
#include <tls.h>
#include <unistd.h>

#ifdef __FreeBSD__
#include <sys/capsicum.h>
#endif

static void clientWrite(struct tls *client, const char *ptr, size_t len) {
	while (len) {
		ssize_t ret = tls_write(client, ptr, len);
		if (ret == TLS_WANT_POLLIN || ret == TLS_WANT_POLLOUT) continue;
		if (ret < 0) errx(EX_IOERR, "tls_write: %s", tls_error(client));
		ptr += ret;
		len -= ret;
	}
}

static void clientFormat(struct tls *client, const char *format, ...) {
	char buf[1024];
	va_list ap;
	va_start(ap, format);
	int len = vsnprintf(buf, sizeof(buf), format, ap);
	va_end(ap);
	if ((size_t)len > sizeof(buf) - 1) errx(EX_DATAERR, "message too large");
	clientWrite(client, buf, len);
}

static void clientHandle(struct tls *client, const char *chan, char *line) {
	char *prefix = NULL;
	if (line[0] == ':') {
		prefix = strsep(&line, " ") + 1;
		if (!line) errx(EX_PROTOCOL, "unexpected eol");
	}

	char *command = strsep(&line, " ");
	if (!strcmp(command, "001") || !strcmp(command, "INVITE")) {
		clientFormat(client, "JOIN :%s\r\n", chan);
	} else if (!strcmp(command, "PING")) {
		clientFormat(client, "PONG %s\r\n", line);
	}
	if (strcmp(command, "PRIVMSG") && strcmp(command, "NOTICE")) return;

	if (!prefix) errx(EX_PROTOCOL, "message without prefix");
	char *nick = strsep(&prefix, "!");

	if (!line) errx(EX_PROTOCOL, "message without destination");
	char *dest = strsep(&line, " ");
	if (strcmp(dest, chan)) return;

	if (!line || line[0] != ':') errx(EX_PROTOCOL, "message without message");
	line = &line[1];

	if (!strncmp(line, "\1ACTION ", 8)) {
		line = &line[8];
		size_t len = strcspn(line, "\1");
		printf("* %c\u200C%s %.*s\n", nick[0], &nick[1], (int)len, line);
	} else if (command[0] == 'N') {
		printf("-%c\u200C%s- %s\n", nick[0], &nick[1], line);
	} else {
		printf("<%c\u200C%s> %s\n", nick[0], &nick[1], line);
	}
}

#ifdef __FreeBSD__
static void limit(int fd, const cap_rights_t *rights) {
	int error = cap_rights_limit(fd, rights);
	if (error) err(EX_OSERR, "cap_rights_limit");
}
#endif

int main(int argc, char *argv[]) {
	int error;

	if (argc < 5) return EX_USAGE;
	const char *host = argv[1];
	const char *port = argv[2];
	const char *nick = argv[3];
	const char *chan = argv[4];

	setlinebuf(stdout);
	signal(SIGPIPE, SIG_IGN);

	struct tls_config *config = tls_config_new();
	if (!config) errx(EX_SOFTWARE, "tls_config_new");

	error = tls_config_set_ciphers(config, "compat");
	if (error) {
		errx(EX_SOFTWARE, "tls_config_set_ciphers: %s", tls_config_error(config));
	}

	struct tls *client = tls_client();
	if (!client) errx(EX_SOFTWARE, "tls_client");

	error = tls_configure(client, config);
	if (error) errx(EX_SOFTWARE, "tls_configure: %s", tls_error(client));
	tls_config_free(config);

	struct addrinfo *head;
	struct addrinfo hints = {
		.ai_family = AF_UNSPEC,
		.ai_socktype = SOCK_STREAM,
		.ai_protocol = IPPROTO_TCP,
	};
	error = getaddrinfo(host, port, &hints, &head);
	if (error) errx(EX_NOHOST, "getaddrinfo: %s", gai_strerror(error));

	int sock = -1;
	for (struct addrinfo *ai = head; ai; ai = ai->ai_next) {
		sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
		if (sock < 0) err(EX_OSERR, "socket");

		error = connect(sock, ai->ai_addr, ai->ai_addrlen);
		if (!error) break;

		close(sock);
		sock = -1;
	}
	if (sock < 0) err(EX_UNAVAILABLE, "connect");
	freeaddrinfo(head);

	error = tls_connect_socket(client, sock, host);
	if (error) errx(EX_PROTOCOL, "tls_connect: %s", tls_error(client));

#ifdef __FreeBSD__
	error = cap_enter();
	if (error) err(EX_OSERR, "cap_enter");

	cap_rights_t rights;
	cap_rights_init(&rights, CAP_WRITE);
	limit(STDOUT_FILENO, &rights);
	limit(STDERR_FILENO, &rights);

	cap_rights_init(&rights, CAP_EVENT, CAP_READ);
	limit(STDIN_FILENO, &rights);

	cap_rights_set(&rights, CAP_WRITE);
	limit(sock, &rights);
#endif

	clientFormat(client, "NICK :%s\r\nUSER %s 0 * :%s\r\n", nick, nick, nick);

	char *input = NULL;
	size_t cap = 0;

	char buf[4096];
	size_t len = 0;

	struct pollfd fds[2] = {
		{ .events = POLLIN, .fd = STDIN_FILENO },
		{ .events = POLLIN, .fd = sock },
	};
	while (0 < poll(fds, 2, -1)) {
		if (fds[0].revents) {
			ssize_t len = getline(&input, &cap, stdin);
			if (len < 0) err(EX_IOERR, "getline");
			input[len - 1] = '\0';
			clientFormat(client, "NOTICE %s :%s\r\n", chan, input);
		}
		if (!fds[1].revents) continue;

		ssize_t read = tls_read(client, &buf[len], sizeof(buf) - len);
		if (read == TLS_WANT_POLLIN || read == TLS_WANT_POLLOUT) continue;
		if (read < 0) errx(EX_IOERR, "tls_read: %s", tls_error(client));
		if (!read) return EX_UNAVAILABLE;
		len += read;

		char *crlf;
		char *line = buf;
		for (;;) {
			crlf = memmem(line, &buf[len] - line, "\r\n", 2);
			if (!crlf) break;
			crlf[0] = '\0';
			clientHandle(client, chan, line);
			line = &crlf[2];
		}
		len -= line - buf;
		memmove(buf, line, len);
	}
	err(EX_IOERR, "poll");
}