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When system calls indicate an error they return -1, not some arbitrary
value < 0.  errno is only updated in this case.  Change all (most?)
callers of syscalls to follow this better, and let's see if this strictness
helps us in the future.

/* $OpenBSD: command.c,v 1.18 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/types.h>
#include <sys/ioctl.h>
#include <sys/wait.h>

#include <event.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <paths.h>
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <vis.h>

#include "cu.h"

void	pipe_command(void);
void	connect_command(void);
void	send_file(void);
void	send_xmodem(void);
void	set_speed(void);
void	start_record(void);

void
pipe_command(void)
{
	const char	*cmd;
	pid_t		 pid;
	int		 fd;

	cmd = get_input("Local command?");
	if (cmd == NULL || *cmd == '\0')
		return;

	restore_termios();
	set_blocking(line_fd, 1);

	switch (pid = fork()) {
	case -1:
		cu_err(1, "fork");
	case 0:
		fd = open(_PATH_DEVNULL, O_RDWR);
		if (fd == -1 || dup2(fd, STDIN_FILENO) == -1)
			_exit(1);
		close(fd);

		if (signal(SIGINT, SIG_DFL) == SIG_ERR)
			_exit(1);
		if (signal(SIGQUIT, SIG_DFL) == SIG_ERR)
			_exit(1);

		/* attach stdout to line */
		if (dup2(line_fd, STDOUT_FILENO) == -1)
			_exit(1);

		if (closefrom(STDERR_FILENO + 1) != 0)
			_exit(1);

		execl(_PATH_BSHELL, "sh", "-c", cmd, (char *)NULL);
		_exit(1);
	default:
		while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
			/* nothing */;
		break;
	}

	set_blocking(line_fd, 0);
	set_termios();
}

void
connect_command(void)
{
	const char	*cmd;
	pid_t		 pid;

	/*
	 * Fork a program with:
	 *  0 <-> remote tty in
	 *  1 <-> remote tty out
	 *  2 <-> local tty stderr
	 */

	cmd = get_input("Local command?");
	if (cmd == NULL || *cmd == '\0')
		return;

	restore_termios();
	set_blocking(line_fd, 1);

	switch (pid = fork()) {
	case -1:
		cu_err(1, "fork");
	case 0:
		if (signal(SIGINT, SIG_DFL) == SIG_ERR)
			_exit(1);
		if (signal(SIGQUIT, SIG_DFL) == SIG_ERR)
			_exit(1);

		/* attach stdout and stdin to line */
		if (dup2(line_fd, STDOUT_FILENO) == -1)
			_exit(1);
		if (dup2(line_fd, STDIN_FILENO) == -1)
			_exit(1);

		if (closefrom(STDERR_FILENO + 1) != 0)
			_exit(1);

		execl(_PATH_BSHELL, "sh", "-c", cmd, (char *)NULL);
		_exit(1);
	default:
		while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
			/* nothing */;
		break;
	}

	set_blocking(line_fd, 0);
	set_termios();
}

void
send_file(void)
{
	const char	*file;
	FILE		*f;
	char		 buf[BUFSIZ], *expanded;
	size_t		 len;

	file = get_input("Local file?");
	if (file == NULL || *file == '\0')
		return;

	expanded = tilde_expand(file);
	f = fopen(expanded, "r");
	if (f == NULL) {
		cu_warn("%s", file);
		return;
	}

	while (!feof(f) && !ferror(f)) {
		len = fread(buf, 1, sizeof(buf), f);
		if (len != 0)
			bufferevent_write(line_ev, buf, len);
	}

	fclose(f);
	free(expanded);
}

void
send_xmodem(void)
{
	const char	*file;
	char		*expanded;

	file = get_input("Local file?");
	if (file == NULL || *file == '\0')
		return;

	expanded = tilde_expand(file);
	xmodem_send(expanded);
	free(expanded);
}

void
set_speed(void)
{
	const char	*s, *errstr;
	int		 speed;

	s = get_input("New speed?");
	if (s == NULL || *s == '\0')
		return;

	speed = strtonum(s, 0, UINT_MAX, &errstr);
	if (errstr != NULL) {
		cu_warnx("speed is %s: %s", errstr, s);
		return;
	}

	if (set_line(speed) != 0)
		cu_warn("tcsetattr");
}

void
start_record(void)
{
	const char	*file;

	if (record_file != NULL) {
		fclose(record_file);
		record_file = NULL;
	}

	file = get_input("Record file?");
	if (file == NULL || *file == '\0')
		return;

	record_file = fopen(file, "a");
	if (record_file == NULL)
		cu_warnx("%s", file);
}

void
do_command(char c)
{
	char esc[4 + 1];

	if (restricted && strchr("CRX$>", c) != NULL) {
		cu_warnx("~%c command is not allowed in restricted mode", c);
		return;
	}

	switch (c) {
	case '.':
	case '\004': /* ^D */
		event_loopexit(NULL);
		break;
	case '\032': /* ^Z */
		restore_termios();
		kill(getpid(), SIGTSTP);
		set_termios();
		break;
	case 'C':
		connect_command();
		break;
	case 'D':
		ioctl(line_fd, TIOCCDTR, NULL);
		sleep(1);
		ioctl(line_fd, TIOCSDTR, NULL);
		break;
	case 'R':
		start_record();
		break;
	case 'S':
		set_speed();
		break;
	case 'X':
		send_xmodem();
		break;
	case '$':
		pipe_command();
		break;
	case '>':
		send_file();
		break;
	case '#':
		ioctl(line_fd, TIOCSBRK, NULL);
		sleep(1);
		ioctl(line_fd, TIOCCBRK, NULL);
		break;
	default:
		if ((u_char)c == escape_char)
			bufferevent_write(line_ev, &c, 1);
		break;
	case '?':
		vis(esc, escape_char, VIS_WHITE | VIS_NOSLASH, 0);
		printf("\r\n"
		    "%s#      send break\r\n"
		    "%s$      pipe local command to remote host\r\n"
		    "%s>      send file to remote host\r\n"
		    "%sC      connect program to remote host\r\n"
		    "%sD      de-assert DTR line briefly\r\n"
		    "%sR      start recording to file\r\n"
		    "%sS      set speed\r\n"
		    "%sX      send file with XMODEM\r\n"
		    "%s?      get this summary\r\n",
		    esc, esc, esc, esc, esc, esc, esc, esc, esc
		);
		break;
	}
}