IABSD.fr/src/lib/libutil/pty.c

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• Author : nicm
  Date : 2017-04-20 17:48:30
  Hash : c2a62bf3
  Message : Add getptmfd(), fdopenpty(), fdforkpty() functions. These allow programs to separate the open(/dev/ptm) from the ioctl(PTMGET) for privilege separation or pledge(). Based on a diff from reyk@. ok deraadt millert

• lib/libutil/pty.c

• /*	$OpenBSD: pty.c,v 1.21 2017/04/20 17:48:30 nicm Exp $	*/
  
  /*-
   * Copyright (c) 1990, 1993
   *	The Regents of the University of California.  All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. Neither the name of the University nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   */
  
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <sys/ioctl.h>
  #include <fcntl.h>
  #include <termios.h>
  #include <errno.h>
  #include <unistd.h>
  #include <stdio.h>
  #include <string.h>
  #include <grp.h>
  #include <sys/tty.h>
  
  #include "util.h"
  
  int
  getptmfd(void)
  {
  	return (open(PATH_PTMDEV, O_RDWR|O_CLOEXEC));
  }
  
  int
  openpty(int *amaster, int *aslave, char *name, struct termios *termp,
      struct winsize *winp)
  {
  	int ptmfd;
  
  	if ((ptmfd = getptmfd()) == -1)
  		return (-1);
  	if (fdopenpty(ptmfd, amaster, aslave, name, termp, winp) == -1) {
  		close(ptmfd);
  		return (-1);
  	}
  	close(ptmfd);
  	return (0);
  }
  
  int
  fdopenpty(int ptmfd, int *amaster, int *aslave, char *name,
      struct termios *termp, struct winsize *winp)
  {
  	int master, slave;
  	struct ptmget ptm;
  
  	/*
  	 * Use /dev/ptm and the PTMGET ioctl to get a properly set up and
  	 * owned pty/tty pair.
  	 */
  	if (ioctl(ptmfd, PTMGET, &ptm) == -1)
  		return (-1);
  
  	master = ptm.cfd;
  	slave = ptm.sfd;
  	if (name) {
  		/*
  		 * Manual page says "at least 16 characters".
  		 */
  		strlcpy(name, ptm.sn, 16);
  	}
  	*amaster = master;
  	*aslave = slave;
  	if (termp)
  		(void) tcsetattr(slave, TCSAFLUSH, termp);
  	if (winp)
  		(void) ioctl(slave, TIOCSWINSZ, winp);
  	return (0);
  }
  
  pid_t
  forkpty(int *amaster, char *name, struct termios *termp, struct winsize *winp)
  {
  	int ptmfd;
  	pid_t pid;
  
  	if ((ptmfd = getptmfd()) == -1)
  		return (-1);
  	if ((pid = fdforkpty(ptmfd, amaster, name, termp, winp)) == -1) {
  		close(ptmfd);
  		return (-1);
  	}
  	close(ptmfd);
  	return (pid);
  }
  
  pid_t
  fdforkpty(int ptmfd, int *amaster, char *name, struct termios *termp,
      struct winsize *winp)
  {
  	int master, slave;
  	pid_t pid;
  
  	if (fdopenpty(ptmfd, &master, &slave, name, termp, winp) == -1)
  		return (-1);
  	switch (pid = fork()) {
  	case -1:
  		(void) close(master);
  		(void) close(slave);
  		return (-1);
  	case 0:
  		/*
  		 * child
  		 */
  		(void) close(master);
  		login_tty(slave);
  		return (0);
  	}
  	/*
  	 * parent
  	 */
  	*amaster = master;
  	(void) close(slave);
  	return (pid);
  }