get_pty.c

/*
 * SPDX-License-Identifier: ISC
 *
 * Copyright (c) 2009-2012, 2014-2016
 *	Todd C. Miller <[email protected]>
 *
 * 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 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 <config.h>

#include <sys/stat.h>
#include <sys/ioctl.h>
#ifdef HAVE_SYS_STROPTS_H
#include <sys/stropts.h>
#endif /* HAVE_SYS_STROPTS_H */
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>

#if defined(HAVE_OPENPTY)
# if defined(HAVE_LIBUTIL_H)
#  include <libutil.h>		/* *BSD */
# elif defined(HAVE_UTIL_H)
#  include <util.h>		/* macOS */
# elif defined(HAVE_PTY_H)
#  include <pty.h>		/* Linux */
# else
#  include <termios.h>		/* Solaris */
# endif
#endif

#include <sudo.h>

#if defined(HAVE_OPENPTY)
char *
get_pty(int *leader, int *follower, uid_t ttyuid)
{
    struct group *gr;
    gid_t ttygid = (gid_t)-1;
    char name[PATH_MAX];
    char *ret = NULL;
    debug_decl(get_pty, SUDO_DEBUG_PTY);

    if ((gr = getgrnam("tty")) != NULL)
	ttygid = gr->gr_gid;

    if (openpty(leader, follower, name, NULL, NULL) == 0) {
	if (chown(name, ttyuid, ttygid) == 0)
	    ret = strdup(name);
    }

    debug_return_str(ret);
}

#elif defined(HAVE__GETPTY)
char *
get_pty(int *leader, int *follower, uid_t ttyuid)
{
    char *line;
    char *ret = NULL;
    debug_decl(get_pty, SUDO_DEBUG_PTY);

    /* IRIX-style dynamic ptys (may fork) */
    line = _getpty(leader, O_RDWR, S_IRUSR|S_IWUSR|S_IWGRP, 0);
    if (line != NULL) {
	*follower = open(line, O_RDWR|O_NOCTTY, 0);
	if (*follower != -1) {
	    (void) chown(line, ttyuid, -1);
	    ret = strdup(line);
	} else {
	    close(*leader);
	    *leader = -1;
	}
    }
    debug_return_str(ret);
}
#elif defined(HAVE_GRANTPT)
# ifndef HAVE_POSIX_OPENPT
static int
posix_openpt(int oflag)
{
    int fd;

#  ifdef _AIX
    fd = open(_PATH_DEV "ptc", oflag);
#  else
    fd = open(_PATH_DEV "ptmx", oflag);
#  endif
    return fd;
}
# endif /* HAVE_POSIX_OPENPT */

char *
get_pty(int *leader, int *follower, uid_t ttyuid)
{
    char *line, *ret = NULL;
    debug_decl(get_pty, SUDO_DEBUG_PTY);

    *leader = posix_openpt(O_RDWR|O_NOCTTY);
    if (*leader != -1) {
	(void) grantpt(*leader); /* may fork */
	if (unlockpt(*leader) != 0) {
	    close(*leader);
	    goto done;
	}
	line = ptsname(*leader);
	if (line == NULL) {
	    close(*leader);
	    goto done;
	}
	*follower = open(line, O_RDWR|O_NOCTTY, 0);
	if (*follower == -1) {
	    close(*leader);
	    goto done;
	}
# if defined(I_PUSH) && !defined(_AIX)
	ioctl(*follower, I_PUSH, "ptem");	/* pseudo tty emulation module */
	ioctl(*follower, I_PUSH, "ldterm");	/* line discipline module */
# endif
	(void) chown(line, ttyuid, -1);
	ret = strdup(line);
    }
done:
    debug_return_str(ret);
}

#else /* Old-style BSD ptys */

static char line[] = _PATH_DEV "ptyXX";

char *
get_pty(int *leader, int *follower, uid_t ttyuid)
{
    char *bank, *cp;
    struct group *gr;
    gid_t ttygid = -1;
    char *ret = NULL;
    debug_decl(get_pty, SUDO_DEBUG_PTY);

    if ((gr = getgrnam("tty")) != NULL)
	ttygid = gr->gr_gid;

    for (bank = "pqrs"; *bank != '\0'; bank++) {
	line[sizeof(_PATH_DEV "ptyX") - 2] = *bank;
	for (cp = "0123456789abcdef"; *cp != '\0'; cp++) {
	    line[sizeof(_PATH_DEV "ptyXX") - 2] = *cp;
	    *leader = open(line, O_RDWR|O_NOCTTY, 0);
	    if (*leader == -1) {
		if (errno == ENOENT)
		    goto done; /* out of ptys */
		continue; /* already in use */
	    }
	    line[sizeof(_PATH_DEV "p") - 2] = 't';
	    (void) chown(line, ttyuid, ttygid);
	    (void) chmod(line, S_IRUSR|S_IWUSR|S_IWGRP);
# ifdef HAVE_REVOKE
	    (void) revoke(line);
# endif
	    *follower = open(line, O_RDWR|O_NOCTTY, 0);
	    if (*follower != -1) {
		    ret = strdup(line);
		    goto done;
	    }
	    (void) close(*leader);
	}
    }
done:
    debug_return_str(ret);
}
#endif /* HAVE_OPENPTY */