lib/grantpt.c

   1 /* Acquire ownership of the slave side of a pseudo-terminal.
   2    Copyright (C) 1998-2002, 2009-2024 Free Software Foundation, Inc.
   3    Contributed by Zack Weinberg <zack@rabi.phys.columbia.edu>, 1998.
   4
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9
  10    This file 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
  13    GNU Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 #include <stdlib.h>
  21
  22 #include <assert.h>
  23 #include <errno.h>
  24 #include <string.h>
  25 #include <sys/wait.h>
  26 #include <unistd.h>
  27
  28 #if HAVE_SETRLIMIT
  29 # include <sys/types.h>
  30 # include <sys/time.h>
  31 # include <sys/resource.h>
  32 #endif
  33
  34 #include "configmake.h"
  35 #include "pty-private.h"
  36
  37 #ifndef _LIBC
  38 # define __set_errno(e) errno = (e)
  39 # define __dup2 dup2
  40 # define __fork fork
  41 # define __setrlimit setrlimit
  42 # define __waitpid waitpid
  43 #endif
  44
  45 int
  46 grantpt (int fd)
  47 {
  48 #if defined __OpenBSD__ || defined _WIN32
  49   /* On OpenBSD, master and slave of a pseudo-terminal are allocated together,
  50      through an ioctl on /dev/ptm.  On Windows there are no ptys.
  51      Therefore in either case there is no need for grantpt().  */
  52   return 0;
  53 #else
  54   /* This function is most often called from a process without 'root'
  55      credentials.  Use the helper program.  */
  56   int retval = -1;
  57   pid_t pid = __fork ();
  58   if (pid == -1)
  59     goto cleanup;
  60   else if (pid == 0)
  61     {
  62       /* This is executed in the child process.  */
  63
  64 # if HAVE_SETRLIMIT && defined RLIMIT_CORE
  65       /* Disable core dumps.  */
  66       struct rlimit rl = { 0, 0 };
  67       __setrlimit (RLIMIT_CORE, &rl);
  68 # endif
  69
  70       /* We pass the master pseudo terminal as file descriptor PTY_FILENO.  */
  71       if (fd != PTY_FILENO)
  72         if (__dup2 (fd, PTY_FILENO) < 0)
  73           _exit (FAIL_EBADF);
  74
  75 # ifdef CLOSE_ALL_FDS
  76       CLOSE_ALL_FDS ();
  77 # endif
  78
  79       execle (_PATH_PT_CHOWN, strrchr (_PATH_PT_CHOWN, '/') + 1, NULL, NULL);
  80       _exit (FAIL_EXEC);
  81     }
  82   else
  83     {
  84       int w;
  85
  86       if (__waitpid (pid, &w, 0) == -1)
  87         goto cleanup;
  88       if (!WIFEXITED (w))
  89         __set_errno (ENOEXEC);
  90       else
  91         switch (WEXITSTATUS (w))
  92           {
  93           case 0:
  94             retval = 0;
  95             break;
  96           case FAIL_EBADF:
  97             __set_errno (EBADF);
  98             break;
  99           case FAIL_EINVAL:
 100             __set_errno (EINVAL);
 101             break;
 102           case FAIL_EACCES:
 103             __set_errno (EACCES);
 104             break;
 105           case FAIL_EXEC:
 106             __set_errno (ENOEXEC);
 107             break;
 108           case FAIL_ENOMEM:
 109             __set_errno (ENOMEM);
 110             break;
 111
 112           default:
 113             assert(! "getpt: internal error: invalid exit code from pt_chown");
 114           }
 115     }
 116
 117  cleanup:
 118   return retval;
 119 #endif
 120 }