sysdeps/unix/grantpt.c

   1 /* Copyright (C) 1998 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 Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    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    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <errno.h>
  21 #include <stdlib.h>
  22 #include <unistd.h>
  23 #include <sys/resource.h>
  24 #include <sys/stat.h>
  25 #include <sys/types.h>
  26 #include <sys/wait.h>
  27
  28 #include <assert.h>
  29
  30 #include "pty-internal.h"
  31
  32 /* Given a fd on a master pseudoterminal, chown the file associated
  33    with the slave to the calling process, and set its group and
  34    mode appropriately.  Note that this is an unprivileged operation. */
  35
  36 /* This "generic Unix" implementation works because we provide the program
  37    /usr/libexec/pt_chown, and it only depends on ptsname() working. */
  38 static const char helper[] = LIBEXECDIR "/pt_chown";
  39 static const char *const argv[] = { "pt_chown", NULL };
  40
  41 int
  42 grantpt (fd)
  43      int fd;
  44 {
  45   struct stat st;
  46   int w, pid;
  47   char namebuf[PTYNAMELEN];
  48
  49   /* Some systems do it for us.  */
  50   if (__ptsname_r (fd, namebuf, PTYNAMELEN) != 0)
  51     return -1;
  52   if (__xstat (_STAT_VER, namebuf, &st) != 0)
  53     return -1;
  54
  55   if (st.st_uid == getuid ())
  56     return 0;
  57
  58   /* We have to do it in user space.  */
  59
  60   pid = fork ();
  61   if (pid == -1)
  62     return -1;
  63   else if (pid == 0)
  64     {
  65       /* Disable core dumps in the child.  */
  66       struct rlimit off = { 0, 0 };
  67       setrlimit (RLIMIT_CORE, &off);
  68
  69       /* The helper does its thing on fd PTY_FD.  */
  70       if (fd != PTY_FD)
  71         if (dup2 (fd, PTY_FD) == -1)
  72           _exit (FAIL_EBADF);
  73
  74       execve (helper, (char *const *) argv, 0);
  75       _exit (FAIL_EXEC);
  76     }
  77   else
  78     {
  79       if (waitpid (pid, &w, 0) == -1)
  80         return -1;
  81       if (!WIFEXITED (w))
  82         {
  83           __set_errno (ENOEXEC);
  84           return -1;
  85         }
  86       else
  87         switch (WEXITSTATUS(w))
  88           {
  89           case 0:
  90             break;
  91           case FAIL_EBADF:
  92             __set_errno (EBADF);
  93             return -1;
  94           case FAIL_EINVAL:
  95             __set_errno (EINVAL);
  96             return -1;
  97           case FAIL_EACCES:
  98             __set_errno (EACCES);
  99             return -1;
 100           case FAIL_EXEC:
 101             __set_errno (ENOEXEC);
 102             return -1;
 103
 104           default:
 105             assert(! "getpt: internal error: invalid exit code from pt_chown");
 106           }
 107     }
 108
 109   /* Success.  */
 110   return 0;
 111 }