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/**
* cerberus – Minimal login program
*
* Copyright © 2013 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "security.h"
#ifndef TTY_PERM
#define TTY_PERM 0600
#endif
#ifndef FAILURE_SLEEP
#define FAILURE_SLEEP 5
#endif
#define fail(FUNC) ({ perror(#FUNC); sleep(FAILURE_SLEEP); _exit(1); })
/**
* Secure the TTY from spying
*/
void secure_tty(void) /* TODO /dev/vcs[a][0-9]+ */
{
struct termios tty;
struct termios saved_tty;
char* tty_device;
int fd, i;
/* Take owner ship of this TTY */
if (fchown(STDIN_FILENO, 0, 0))
fail(fchown);
/* Restrict others from using this TTY */
if (fchmod(STDIN_FILENO, TTY_PERM))
fail(fchmod);
/* Get TTY name for last part of this functions */
tty_device = ttyname(STDIN_FILENO);
/* Kill other processes on this TTY */
tcgetattr(STDIN_FILENO, &tty);
saved_tty = tty;
tty.c_cflag &= ~HUPCL;
tcsetattr(0, TCSANOW, &tty);
close(STDIN_FILENO);
close(STDOUT_FILENO);
close(STDERR_FILENO);
signal(SIGHUP, SIG_IGN);
vhangup();
signal(SIGHUP, SIG_DFL);
/* Restore terminal and TTY modes */
fd = open(tty_device, O_RDWR | O_NONBLOCK);
if (fd == -1)
fail(open);
fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) & ~O_NONBLOCK);
for (i = 0; i < fd; i++)
close(i);
for (i = 0; i < 3; i++)
if (i != fd)
dup2(fd, i);
if (fd > 2)
close(fd);
tcgetattr(STDIN_FILENO, &saved_tty);
}
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