cu.c

/* $OpenBSD: cu.c,v 1.28 2019/06/28 13:35:00 deraadt Exp $ */

/*
 * Copyright (c) 2012 Nicholas Marriott <nicm@openbsd.org>
 *
 * Permission to use, copy, modify, and 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 MIND, 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.
 */

#include <sys/ioctl.h>

#include <ctype.h>
#include <err.h>
#include <event.h>
#include <fcntl.h>
#include <getopt.h>
#include <paths.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>
#include <limits.h>

#include "cu.h"

extern char		*__progname;

FILE			*record_file;
struct termios		 saved_tio;
struct bufferevent	*input_ev;
struct bufferevent	*output_ev;
int			 escape_char = '~';
int			 is_direct = -1;
int			 restricted = 0;
const char		*line_path = NULL;
int			 line_speed = -1;
int			 line_fd;
struct termios		 line_tio;
struct bufferevent	*line_ev;
struct event		 sigterm_ev;
struct event		 sighup_ev;
enum {
	STATE_NONE,
	STATE_NEWLINE,
	STATE_ESCAPE
} last_state = STATE_NEWLINE;

# define __dead __attribute__((__noreturn__))

__dead void	usage(void);
void		signal_event(int, short, void *);
void		stream_read(struct bufferevent *, void *);
void		stream_error(struct bufferevent *, short, void *);
void		line_read(struct bufferevent *, void *);
void		line_error(struct bufferevent *, short, void *);
void		try_remote(const char *, const char *, const char *);

__dead void
usage(void)
{
	fprintf(stderr, "usage: %s [-dr] [-E escape_char] [-l line] "
	    "[-s speed | -speed]\n", __progname);
	fprintf(stderr, "       %s [host]\n", __progname);
	exit(1);
}

int
main(int argc, char **argv)
{
	const char	*errstr;
#ifdef __OpenBSD__
	char		*tmp, *s, *host;
#else
	char		*tmp, *host;
#endif
	int		 opt, i, flags;

#ifdef __OpenBSD__
	if (pledge("stdio rpath wpath cpath getpw proc exec tty",
	    NULL) == -1)
		err(1, "pledge");
#endif

	if (isatty(STDIN_FILENO) && tcgetattr(STDIN_FILENO, &saved_tio) != 0)
		err(1, "tcgetattr");

	/*
	 * Convert obsolescent -### speed to modern -s### syntax which getopt()
	 * can handle.
	 */
	for (i = 1; i < argc; i++) {
		if (strcmp("--", argv[i]) == 0)
			break;
		if (argv[i][0] != '-' || !isdigit((u_char)argv[i][1]))
			continue;

		if (asprintf(&argv[i], "-s%s", &argv[i][1]) == -1)
			errx(1, "speed asprintf");
	}

	while ((opt = getopt(argc, argv, "drE:l:s:")) != -1) {
		switch (opt) {
		case 'd':
			is_direct = 1;
			break;
#ifdef __OpenBSD__
		case 'r':
			if (pledge("stdio rpath wpath tty", NULL) == -1)
				err(1, "pledge");
			restricted = 1;
			break;
#endif
		case 'E':
			if (optarg[0] == '^' && optarg[2] == '\0' &&
			    (u_char)optarg[1] >= 64 && (u_char)optarg[1] < 128)
				escape_char = (u_char)optarg[1] & 31;
			else if (strlen(optarg) == 1)
				escape_char = (u_char)optarg[0];
			else
				errx(1, "invalid escape character: %s", optarg);
			break;
		case 'l':
			line_path = optarg;
			break;
		case 's':
			line_speed = strtonum(optarg, 0, INT_MAX, &errstr);
			if (errstr != NULL)
				errx(1, "speed is %s: %s", errstr, optarg);
			break;
		default:
			usage();
		}
	}
	argc -= optind;
	argv += optind;
	if (argc != 0 && argc != 1)
		usage();

	if (line_path != NULL || line_speed != -1 || is_direct != -1) {
		if (argc != 0)
			usage();
	} else {
		if (argc == 1)
			host = argv[0];
		else
			host = getenv("HOST");
		if (host != NULL && *host != '\0') {
			if (*host == '/')
				line_path = host;
#ifdef __OpenBSD__
			else {
				s = getenv("REMOTE");
				if (s != NULL && *s == '/')
					try_remote(host, s, NULL);
				else
					try_remote(host, NULL, s);
			}
#endif
		}
	}

	if (line_path == NULL)
		line_path = "/dev/ttyUSB0";
	if (line_speed == -1)
		line_speed = 115200;
	if (is_direct == -1)
		is_direct = 0;

	if (strchr(line_path, '/') == NULL) {
		if (asprintf(&tmp, "%s%s", _PATH_DEV, line_path) == -1)
			err(1, "asprintf");
		line_path = tmp;
	}

	flags = O_RDWR;
	if (is_direct)
		flags |= O_NONBLOCK;
	line_fd = open(line_path, flags);
	if (line_fd == -1)
		err(1, "open(\"%s\")", line_path);
#ifdef __OpenBSD__
	if (restricted && pledge("stdio tty", NULL) == -1)
		err(1, "pledge");
#endif
	if (!isatty(line_fd))
		err(1, "%s", line_path);
	if (ioctl(line_fd, TIOCEXCL) != 0)
		err(1, "ioctl(TIOCEXCL)");
	if (tcgetattr(line_fd, &line_tio) != 0)
		err(1, "tcgetattr");
	if (set_line(line_speed) != 0)
		err(1, "tcsetattr");

	event_init();

	signal_set(&sigterm_ev, SIGTERM, signal_event, NULL);
	signal_add(&sigterm_ev, NULL);
	signal_set(&sighup_ev, SIGHUP, signal_event, NULL);
	signal_add(&sighup_ev, NULL);
	if (signal(SIGINT, SIG_IGN) == SIG_ERR)
		err(1, "signal");
	if (signal(SIGQUIT, SIG_IGN) == SIG_ERR)
		err(1, "signal");

	set_termios(); /* after this use cu_err and friends */

	/* stdin and stdout get separate events */
	input_ev = bufferevent_new(STDIN_FILENO, stream_read, NULL,
	    stream_error, NULL);
	bufferevent_enable(input_ev, EV_READ);
	output_ev = bufferevent_new(STDOUT_FILENO, NULL, NULL, stream_error,
	    NULL);
	bufferevent_enable(output_ev, EV_WRITE);

	set_blocking(line_fd, 0);
	line_ev = bufferevent_new(line_fd, line_read, NULL, line_error,
	    NULL);
	bufferevent_enable(line_ev, EV_READ|EV_WRITE);

	printf("Connected to %s (speed %d)\r\n", line_path, line_speed);
	event_dispatch();

	restore_termios();
	printf("\r\n[EOT]\n");

	exit(0);
}

void
signal_event(int fd, short events, void *data)
{
	restore_termios();
#ifdef __OpenBSD__
	printf("\r\n[SIG%s]\n", sys_signame[fd]);
#else
	printf("\r\n[SIG%s]\n", strsignal(fd));
#endif

	exit(0);
}

void
set_blocking(int fd, int state)
{
	int mode;

	state = state ? 0 : O_NONBLOCK;
	if ((mode = fcntl(fd, F_GETFL)) == -1)
		cu_err(1, "fcntl");
	if ((mode & O_NONBLOCK) != state) {
		mode = (mode & ~O_NONBLOCK) | state;
		if (fcntl(fd, F_SETFL, mode) == -1)
			cu_err(1, "fcntl");
	}
}

void
set_termios(void)
{
	struct termios tio;

	if (!isatty(STDIN_FILENO))
		return;

	memcpy(&tio, &saved_tio, sizeof(tio));
	tio.c_lflag &= ~(ICANON|IEXTEN|ECHO);
	tio.c_iflag &= ~(INPCK|ICRNL);
	tio.c_oflag &= ~OPOST;
	tio.c_cc[VMIN] = 1;
	tio.c_cc[VTIME] = 0;
	tio.c_cc[VDISCARD] = _POSIX_VDISABLE;
#ifdef __OpenBSD__
	tio.c_cc[VDSUSP] = _POSIX_VDISABLE;
#endif
	tio.c_cc[VINTR] = _POSIX_VDISABLE;
	tio.c_cc[VLNEXT] = _POSIX_VDISABLE;
	tio.c_cc[VQUIT] = _POSIX_VDISABLE;
	tio.c_cc[VSUSP] = _POSIX_VDISABLE;
	if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &tio) != 0)
		cu_err(1, "tcsetattr");
}

void
restore_termios(void)
{
	if (isatty(STDIN_FILENO))
		tcsetattr(STDIN_FILENO, TCSAFLUSH, &saved_tio);
}

int
set_line(int speed)
{
	struct termios	 tio;

	memcpy(&tio, &line_tio, sizeof(tio));
	tio.c_iflag &= ~(ISTRIP|ICRNL);
	tio.c_oflag &= ~OPOST;
	tio.c_lflag &= ~(ICANON|ISIG|IEXTEN|ECHO);
	tio.c_cflag &= ~(CSIZE|PARENB);
	tio.c_cflag |= CREAD|CS8|CLOCAL;
	tio.c_cc[VMIN] = 1;
	tio.c_cc[VTIME] = 0;
	cfsetspeed(&tio, speed);
	if (tcsetattr(line_fd, TCSAFLUSH, &tio) != 0)
		return (-1);
	return (0);
}

void
stream_read(struct bufferevent *bufev, void *data)
{
	char	*new_data, *ptr;
	size_t	 new_size;
	int	 state_change;

	new_data = EVBUFFER_DATA(input_ev->input);
	new_size = EVBUFFER_LENGTH(input_ev->input);
	if (new_size == 0)
		return;

	state_change = isatty(STDIN_FILENO);
	for (ptr = new_data; ptr < new_data + new_size; ptr++) {
		switch (last_state) {
		case STATE_NONE:
			if (state_change && *ptr == '\r')
				last_state = STATE_NEWLINE;
			break;
		case STATE_NEWLINE:
			if (state_change && (u_char)*ptr == escape_char) {
				last_state = STATE_ESCAPE;
				continue;
			}
			if (*ptr != '\r')
				last_state = STATE_NONE;
			break;
		case STATE_ESCAPE:
			do_command(*ptr);
			last_state = STATE_NEWLINE;
			continue;
		}

		bufferevent_write(line_ev, ptr, 1);
	}

	evbuffer_drain(input_ev->input, new_size);
}

void
stream_error(struct bufferevent *bufev, short what, void *data)
{
	event_loopexit(NULL);
}

void
line_read(struct bufferevent *bufev, void *data)
{
	char	*new_data;
	size_t	 new_size;

	new_data = EVBUFFER_DATA(line_ev->input);
	new_size = EVBUFFER_LENGTH(line_ev->input);
	if (new_size == 0)
		return;

	if (record_file != NULL)
		fwrite(new_data, 1, new_size, record_file);
	bufferevent_write(output_ev, new_data, new_size);

	evbuffer_drain(line_ev->input, new_size);
}

void
line_error(struct bufferevent *bufev, short what, void *data)
{
	event_loopexit(NULL);
}

#ifdef __OpenBSD__
void
try_remote(const char *host, const char *path, const char *entry)
{
	const char	*paths[] = { "/etc/remote", NULL, NULL };
	char		*cp, *s;
	long		 l;
	int		 error;

	if (path != NULL) {
		paths[0] = path;
		paths[1] = "/etc/remote";
	}

	if (entry != NULL && cgetset(entry) != 0)
		cu_errx(1, "cgetset failed");
	error = cgetent(&cp, (char **)paths, (char *)host);
	if (error < 0) {
		switch (error) {
		case -1:
			cu_errx(1, "unknown host %s", host);
		case -2:
			cu_errx(1, "can't open remote file");
		case -3:
			cu_errx(1, "loop in remote file");
		default:
			cu_errx(1, "unknown error in remote file");
		}
	}

	if (is_direct == -1 && cgetcap(cp, "dc", ':') != NULL)
		is_direct = 1;

	if (line_path == NULL && cgetstr(cp, "dv", &s) >= 0)
		line_path = s;

	if (line_speed == -1 && cgetnum(cp, "br", &l) >= 0) {
		if (l < 0 || l > INT_MAX)
			cu_errx(1, "speed out of range");
		line_speed = l;
	}
}
#endif

/* Expands tildes in the file name. Based on code from ssh/misc.c. */
char *
tilde_expand(const char *filename1)
{
	const char	*filename, *path, *sep;
	char		 user[128], *out;
	struct passwd	*pw;
	u_int		 len, slash;
	int		 rv;

	if (*filename1 != '~')
		goto no_change;
	filename = filename1 + 1;

	path = strchr(filename, '/');
	if (path != NULL && path > filename) {		/* ~user/path */
		slash = path - filename;
		if (slash > sizeof(user) - 1)
			goto no_change;
		memcpy(user, filename, slash);
		user[slash] = '\0';
		if ((pw = getpwnam(user)) == NULL)
			goto no_change;
	} else if ((pw = getpwuid(getuid())) == NULL)	/* ~/path */
		goto no_change;

	/* Make sure directory has a trailing '/' */
	len = strlen(pw->pw_dir);
	if (len == 0 || pw->pw_dir[len - 1] != '/')
		sep = "/";
	else
		sep = "";

	/* Skip leading '/' from specified path */
	if (path != NULL)
		filename = path + 1;

	if ((rv = asprintf(&out, "%s%s%s", pw->pw_dir, sep, filename)) == -1)
		cu_err(1, "asprintf");
	if (rv >= PATH_MAX) {
		free(out);
		goto no_change;
	}

	return (out);

no_change:
	out = strdup(filename1);
	if (out == NULL)
		cu_err(1, "strdup");
	return (out);
}