lib/ptsname_r.c

/* Determine name of the slave side of a pseudo-terminal.
   Copyright (C) 1998, 2002, 2010-2026 Free Software Foundation, Inc.

   This file is free software: you can redistribute it and/or modify
   it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.

   This file 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 Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */
#include <stdlib.h>

#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>

#ifndef _PATH_TTY
# define _PATH_TTY "/dev/tty"
#endif
#ifndef _PATH_DEV
# define _PATH_DEV "/dev/"
#endif

/* Get the major, minor macros.  */
#if MAJOR_IN_MKDEV
# include <sys/mkdev.h>
#endif
#if MAJOR_IN_SYSMACROS
# include <sys/sysmacros.h>
#endif

#ifdef __sun
/* Get ioctl() and 'struct strioctl'.  */
# include <stropts.h>
/* Get ISPTM.  */
# include <sys/stream.h>
# include <sys/ptms.h>
# include <stdio.h>
#endif

#if defined _AIX
/* Get ioctl(), ISPTM.  */
# include <sys/ioctl.h>
# include <stdio.h>
#endif

#if defined __DragonFly__
/* Get fdevname_r().  */
# include <stdlib.h>
#endif

/* Store at most BUFLEN characters of the pathname of the slave pseudo
   terminal associated with the master FD is open on in BUF.
   Return 0 on success, otherwise an error number.  */
int
ptsname_r (int fd, char *buf, size_t buflen)
#undef ptsname_r
{
#if HAVE_ESSENTIALLY_WORKING_PTSNAME_R
# if defined __NetBSD__ || defined __sun
  if (buf == NULL)
    return EINVAL;
  char tmpbuf[32];
  if (buflen >= sizeof (tmpbuf))
    /* ERANGE should not happen in this case.  */
    return ptsname_r (fd, buf, buflen);
  else
    {
      int ret = ptsname_r (fd, tmpbuf, sizeof (tmpbuf));
      if (ret != 0)
        return ret;
      else
        {
          size_t len = strlen (tmpbuf);
          if (len >= buflen)
            return ERANGE;
          memcpy (buf, tmpbuf, len + 1);
          return 0;
        }
    }
# else
  int ret = ptsname_r (fd, buf, buflen);
  if (ret == 0)
    return 0;
  else
    return errno;
# endif
#elif defined __DragonFly__
  if (buf == NULL)
    {
      errno = EINVAL;
      return errno;
    }
  int saved_errno = errno;
  char tmpbuf[5 + 4 + 10 + 1];
  /* The result of fdevname_r is typically of the form ptm/N.  */
  int ret = fdevname_r (fd, tmpbuf + 5, sizeof (tmpbuf) - 5);
  if (ret < 0 || strncmp (tmpbuf + 5, "ptm/", 4) != 0)
    {
      errno = ENOTTY;
      return errno;
    }
  /* Turn it into /dev/pts/N.  */
  memcpy (tmpbuf, "/dev/pts/", 5 + 4);
  int n = strlen (tmpbuf);
  if (n >= buflen)
    {
      errno = ERANGE;
      return errno;
    }
  memcpy (buf, tmpbuf, n + 1);
  /* Don't do a final stat(), since the file name /dev/pts/N does not actually
     exist.  */
  errno = saved_errno;
  return 0;
#else
  if (buf == NULL)
    {
      errno = EINVAL;
      return errno;
    }

  int saved_errno = errno;
  struct stat st;

# if defined __sun /* Solaris */
  if (fstat (fd, &st) < 0)
    return errno;
  if (!S_ISCHR (st.st_mode))
    {
      errno = ENOTTY;
      return errno;
    }
  {
    /* Master ptys can be recognized through a STREAMS ioctl.  See
       "STREAMS-based Pseudo-Terminal Subsystem"
       <https://docs.oracle.com/cd/E18752_01/html/816-4855/termsub15-44781.html>
       and "STREAMS ioctl commands"
       <https://docs.oracle.com/cd/E18752_01/html/816-5177/streamio-7i.html>
     */
    struct strioctl ioctl_arg;
    ioctl_arg.ic_cmd = ISPTM;
    ioctl_arg.ic_timout = 0;
    ioctl_arg.ic_len = 0;
    ioctl_arg.ic_dp = NULL;

    if (ioctl (fd, I_STR, &ioctl_arg) < 0)
      {
        errno = ENOTTY;
        return errno;
      }
  }
  {
    char tmpbuf[9 + 10 + 1];
    int n = sprintf (tmpbuf, "/dev/pts/%u", minor (st.st_rdev));
    if (n >= buflen)
      {
        errno = ERANGE;
        return errno;
      }
    memcpy (buf, tmpbuf, n + 1);
  }
# elif defined _AIX /* AIX */
  /* This implementation returns /dev/pts/N, like ptsname() does.
     Whereas the generic implementation below returns /dev/ttypN.
     Both are correct, but let's be consistent with ptsname().  */
  if (fstat (fd, &st) < 0)
    return errno;
  if (!S_ISCHR (st.st_mode))
    {
      errno = ENOTTY;
      return errno;
    }
  {
    int dev;
    int ret = ioctl (fd, ISPTM, &dev);
    if (ret < 0)
      {
        errno = ENOTTY;
        return errno;
      }
    char tmpbuf[9 + 10 + 1];
    int n = sprintf (tmpbuf, "/dev/pts/%u", minor (dev));
    if (n >= buflen)
      {
        errno = ERANGE;
        return errno;
      }
    memcpy (buf, tmpbuf, n + 1);
  }
# else
  if (!isatty (fd))
    {
#  if ISATTY_FAILS_WITHOUT_SETTING_ERRNO && defined F_GETFL /* Solaris */
      /* Set errno.  */
      if (fcntl (fd, F_GETFL) != -1)
        errno = ENOTTY;
#  else
      /* We rely on isatty to set errno properly (i.e. EBADF or ENOTTY).  */
#  endif
      return errno;
    }

  if (buflen < strlen (_PATH_TTY) + 3)
    {
      errno = ERANGE;
      return errno;
    }

  int err = ttyname_r (fd, buf, buflen);
  if (err != 0)
    {
      errno = err;
      return errno;
    }

  if (strncmp(buf, "/dev/pts/", strlen("/dev/pts/")) != 0)
    buf[sizeof (_PATH_DEV) - 1] = 't';
# endif

  if (stat (buf, &st) < 0 && errno != EOVERFLOW)
    return errno;

  errno = saved_errno;
  return 0;
#endif
}