login/openpty.c

   1 /* Copyright (C) 1998-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Zack Weinberg <zack@rabi.phys.columbia.edu>, 1998.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <fcntl.h>
  21 #include <limits.h>
  22 #include <pty.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <termios.h>
  26 #include <unistd.h>
  27 #include <sys/types.h>
  28
  29
  30 /* Return the result of ptsname_r in the buffer pointed to by PTS,
  31    which should be of length BUF_LEN.  If it is too long to fit in
  32    this buffer, a sufficiently long buffer is allocated using malloc,
  33    and returned in PTS.  0 is returned upon success, -1 otherwise.  */
  34 static int
  35 pts_name (int fd, char **pts, size_t buf_len)
  36 {
  37   int rv;
  38   char *buf = *pts;
  39
  40   for (;;)
  41     {
  42       char *new_buf;
  43
  44       if (buf_len)
  45         {
  46           rv = ptsname_r (fd, buf, buf_len);
  47
  48           if (rv != 0 || memchr (buf, '\0', buf_len))
  49             /* We either got an error, or we succeeded and the
  50                returned name fit in the buffer.  */
  51             break;
  52
  53           /* Try again with a longer buffer.  */
  54           buf_len += buf_len;   /* Double it */
  55         }
  56       else
  57         /* No initial buffer; start out by mallocing one.  */
  58         buf_len = 128;          /* First time guess.  */
  59
  60       if (buf != *pts)
  61         /* We've already malloced another buffer at least once.  */
  62         new_buf = realloc (buf, buf_len);
  63       else
  64         new_buf = malloc (buf_len);
  65       if (! new_buf)
  66         {
  67           rv = -1;
  68           __set_errno (ENOMEM);
  69           break;
  70         }
  71       buf = new_buf;
  72     }
  73
  74   if (rv == 0)
  75     *pts = buf;         /* Return buffer to the user.  */
  76   else if (buf != *pts)
  77     free (buf);         /* Free what we malloced when returning an error.  */
  78
  79   return rv;
  80 }
  81
  82 /* Create pseudo tty master slave pair and set terminal attributes
  83    according to TERMP and WINP.  Return handles for both ends in
  84    AMASTER and ASLAVE, and return the name of the slave end in NAME.  */
  85 int
  86 openpty (int *amaster, int *aslave, char *name,
  87          const struct termios *termp, const struct winsize *winp)
  88 {
  89 #ifdef PATH_MAX
  90   char _buf[PATH_MAX];
  91 #else
  92   char _buf[512];
  93 #endif
  94   char *buf = _buf;
  95   int master, slave;
  96
  97   master = getpt ();
  98   if (master == -1)
  99     return -1;
 100
 101   if (grantpt (master))
 102     goto fail;
 103
 104   if (unlockpt (master))
 105     goto fail;
 106
 107   if (pts_name (master, &buf, sizeof (_buf)))
 108     goto fail;
 109
 110   slave = open (buf, O_RDWR | O_NOCTTY);
 111   if (slave == -1)
 112     {
 113       if (buf != _buf)
 114         free (buf);
 115
 116       goto fail;
 117     }
 118
 119   /* XXX Should we ignore errors here?  */
 120   if (termp)
 121     tcsetattr (slave, TCSAFLUSH, termp);
 122 #ifdef TIOCSWINSZ
 123   if (winp)
 124     ioctl (slave, TIOCSWINSZ, winp);
 125 #endif
 126
 127   *amaster = master;
 128   *aslave = slave;
 129   if (name != NULL)
 130     strcpy (name, buf);
 131
 132   if (buf != _buf)
 133     free (buf);
 134   return 0;
 135
 136  fail:
 137   close (master);
 138   return -1;
 139 }
 140 libutil_hidden_def (openpty)