freebsd-dev/lib/libc/stdlib/grantpt.c

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/*
* Copyright (c) 2002 The FreeBSD Project, Inc.
* All rights reserved.
*
* This software includes code contributed to the FreeBSD Project
* by Ryan Younce of North Carolina State University.
*
* 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 FreeBSD Project 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 FREEBSD PROJECT 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 FREEBSD PROJECT OR ITS 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/cdefs.h>
#ifndef lint
__FBSDID("$FreeBSD$");
#endif /* not lint */
#include "namespace.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/resource.h>
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#include <sys/sysctl.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <paths.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>
#include "un-namespace.h"
#define PTM_PREFIX "pty" /* pseudo tty master naming convention */
#define PTS_PREFIX "tty" /* pseudo tty slave naming convention */
#define NEWPTS_PREFIX "pts"
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#define PTMX "ptmx"
/*
* The following are range values for pseudo TTY devices. Pseudo TTYs have a
* name of /dev/[pt]ty[p-sP-S][0-9a-v], yielding 256 combinations per major.
*/
#define PT_MAX 256
#define PT_DEV1 "pqrsPQRS"
#define PT_DEV2 "0123456789abcdefghijklmnopqrstuv"
/*
* grantpt(3) support utility.
*/
#define _PATH_PTCHOWN "/usr/libexec/pt_chown"
/*
* ISPTM(x) returns 0 for struct stat x if x is not a pty master.
* The bounds checking may be unnecessary but it does eliminate doubt.
*/
#define ISPTM(x) (S_ISCHR((x).st_mode) && \
minor((x).st_rdev) >= 0 && \
minor((x).st_rdev) < PT_MAX)
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static int
is_pts(int fd)
{
int nb;
return (_ioctl(fd, TIOCGPTN, &nb) == 0);
}
int
__use_pts(void)
{
int use_pts;
size_t len;
int error;
len = sizeof(use_pts);
error = sysctlbyname("kern.pts.enable", &use_pts, &len, NULL, 0);
if (error) {
struct stat sb;
if (stat("/dev/ptmx", &sb) != 0)
return (0);
use_pts = 1;
}
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return (use_pts);
}
/*
* grantpt(): grant ownership of a slave pseudo-terminal device to the
* current user.
*/
int
grantpt(int fildes)
{
int retval, serrno, status;
pid_t pid, spid;
gid_t gid;
char *slave;
sigset_t oblock, nblock;
struct group *grp;
retval = -1;
serrno = errno;
if ((slave = ptsname(fildes)) != NULL) {
/*
* Block SIGCHLD.
*/
(void)sigemptyset(&nblock);
(void)sigaddset(&nblock, SIGCHLD);
(void)_sigprocmask(SIG_BLOCK, &nblock, &oblock);
switch (pid = fork()) {
case -1:
break;
case 0: /* child */
/*
* pt_chown expects the master pseudo TTY to be its
* standard input.
*/
(void)_dup2(fildes, STDIN_FILENO);
(void)_sigprocmask(SIG_SETMASK, &oblock, NULL);
execl(_PATH_PTCHOWN, _PATH_PTCHOWN, (char *)NULL);
_exit(EX_UNAVAILABLE);
/* NOTREACHED */
default: /* parent */
/*
* Just wait for the process. Error checking is
* done below.
*/
while ((spid = _waitpid(pid, &status, 0)) == -1 &&
(errno == EINTR))
;
if (spid != -1 && WIFEXITED(status) &&
WEXITSTATUS(status) == EX_OK)
retval = 0;
else
errno = EACCES;
break;
}
/*
* Restore process's signal mask.
*/
(void)_sigprocmask(SIG_SETMASK, &oblock, NULL);
if (retval) {
/*
* pt_chown failed. Try to manually change the
* permissions for the slave.
*/
gid = (grp = getgrnam("tty")) ? grp->gr_gid : -1;
if (chown(slave, getuid(), gid) == -1 ||
chmod(slave, S_IRUSR | S_IWUSR | S_IWGRP) == -1)
errno = EACCES;
else
retval = 0;
}
}
if (!retval)
errno = serrno;
return (retval);
}
/*
* posix_openpt(): open the first available master pseudo-terminal device
* and return descriptor.
*/
int
posix_openpt(int oflag)
{
char *mc1, *mc2, master[] = _PATH_DEV PTM_PREFIX "XY";
const char *pc1, *pc2;
int fildes, bflag, serrno;
fildes = -1;
bflag = 0;
serrno = errno;
/*
* Check flag validity. POSIX doesn't require it,
* but we still do so.
*/
if (oflag & ~(O_RDWR | O_NOCTTY))
errno = EINVAL;
else {
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if (__use_pts()) {
fildes = _open(_PATH_DEV PTMX, oflag);
return (fildes);
}
mc1 = master + strlen(_PATH_DEV PTM_PREFIX);
mc2 = mc1 + 1;
/* Cycle through all possible master PTY devices. */
for (pc1 = PT_DEV1; !bflag && (*mc1 = *pc1); ++pc1)
for (pc2 = PT_DEV2; (*mc2 = *pc2) != '\0'; ++pc2) {
/*
* Break out if we successfully open a PTY,
* or if open() fails due to limits.
*/
if ((fildes = _open(master, oflag)) != -1 ||
(errno == EMFILE || errno == ENFILE)) {
++bflag;
break;
}
}
if (fildes != -1)
errno = serrno;
else if (!bflag)
errno = EAGAIN;
}
return (fildes);
}
/*
* ptsname(): return the pathname of the slave pseudo-terminal device
* associated with the specified master.
*/
char *
ptsname(int fildes)
{
static char slave[] = _PATH_DEV PTS_PREFIX "XY";
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static char new_slave[] = _PATH_DEV NEWPTS_PREFIX "4294967295";
char *retval;
struct stat sbuf;
retval = NULL;
if (_fstat(fildes, &sbuf) == 0) {
if (!ISPTM(sbuf))
errno = EINVAL;
else {
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if (!is_pts(fildes)) {
(void)snprintf(slave, sizeof(slave),
_PATH_DEV PTS_PREFIX "%s",
devname(sbuf.st_rdev, S_IFCHR) +
strlen(PTM_PREFIX));
retval = slave;
} else {
(void)snprintf(new_slave, sizeof(new_slave),
_PATH_DEV NEWPTS_PREFIX "%s",
devname(sbuf.st_rdev, S_IFCHR) +
strlen(PTM_PREFIX));
retval = new_slave;
}
}
}
return (retval);
}
/*
* unlockpt(): unlock a pseudo-terminal device pair.
*/
int
unlockpt(int fildes)
{
int retval;
struct stat sbuf;
/*
* Unlocking a master/slave pseudo-terminal pair has no meaning in a
* non-streams PTY environment. However, we do ensure fildes is a
* valid master pseudo-terminal device.
*/
if ((retval = _fstat(fildes, &sbuf)) == 0 && !ISPTM(sbuf)) {
errno = EINVAL;
retval = -1;
}
return (retval);
}