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doug and I think the kernel has enough features to support
pledge "stdio rpath wpath cpath getpw proc exec tty" now.
It will be hard to drop many of those features unless cu becomes
privsep for the "upload" commands.

/* $OpenBSD: cu.c,v 1.24 2015/10/16 07:01:53 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			 is_direct = -1;
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_TILDE
} last_state = STATE_NEWLINE;

__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 [-d] [-l line] [-s speed | -speed]\n",
	    __progname);
	fprintf(stderr, "       %s [host]\n", __progname);
	exit(1);
}

int
main(int argc, char **argv)
{
	const char	*errstr;
	char		*tmp, *s, *host;
	int		 opt, i, flags;

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

	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((unsigned char)argv[i][1]))
			continue;

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

	while ((opt = getopt(argc, argv, "dl:s:")) != -1) {
		switch (opt) {
		case 'd':
			is_direct = 1;
			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;
			else {
				s = getenv("REMOTE");
				if (s != NULL && *s == '/')
					try_remote(host, s, NULL);
				else
					try_remote(host, NULL, s);
			}
		}
	}

	if (line_path == NULL)
		line_path = "/dev/cua00";
	if (line_speed == -1)
		line_speed = 9600;
	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 < 0)
		err(1, "open(\"%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();
	printf("\r\n[SIG%s]\n", sys_signame[fd]);

	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;
	tio.c_cc[VDSUSP] = _POSIX_VDISABLE;
	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 && *ptr == '~') {
				last_state = STATE_TILDE;
				continue;
			}
			if (*ptr != '\r')
				last_state = STATE_NONE;
			break;
		case STATE_TILDE:
			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);
}

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;
	}
}

/* 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);
}