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glibc  2.9
Functions
grantpt.c File Reference
#include <assert.h>
#include <errno.h>
#include <grp.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include "pty-private.h"
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Functions

static int pts_name (int fd, char **pts, size_t buf_len)
int grantpt (int fd)

Function Documentation

int grantpt ( int  fd)

Definition at line 100 of file grantpt.c.

{
  int retval = -1;
#ifdef PATH_MAX
  char _buf[PATH_MAX];
#else
  char _buf[512];
#endif
  char *buf = _buf;
  struct stat64 st;
  char *grtmpbuf;
  struct group grbuf;
  size_t grbuflen = __sysconf (_SC_GETGR_R_SIZE_MAX);
  struct group *p;
  uid_t uid;
  gid_t gid;
  pid_t pid;

  if (pts_name (fd, &buf, sizeof (_buf)))
    return -1;

  if (__xstat64 (_STAT_VER, buf, &st) < 0)
    goto cleanup;

  /* Make sure that we own the device.  */
  uid = __getuid ();
  if (st.st_uid != uid)
    {
      if (__chown (buf, uid, st.st_gid) < 0)
       goto helper;
    }

  /* Get the group ID of the special `tty' group.  */
  if (grbuflen == (size_t) -1L)
    /* `sysconf' does not support _SC_GETGR_R_SIZE_MAX.
       Try a moderate value.  */
    grbuflen = 1024;
  grtmpbuf = (char *) __alloca (grbuflen);
  __getgrnam_r (TTY_GROUP, &grbuf, grtmpbuf, grbuflen, &p);
  gid = p ? p->gr_gid : __getgid ();

  /* Make sure the group of the device is that special group.  */
  if (st.st_gid != gid)
    {
      if (__chown (buf, uid, gid) < 0)
       goto helper;
    }

  /* Make sure the permission mode is set to readable and writable by
     the owner, and writable by the group.  */
  if ((st.st_mode & ACCESSPERMS) != (S_IRUSR|S_IWUSR|S_IWGRP))
    {
      if (__chmod (buf, S_IRUSR|S_IWUSR|S_IWGRP) < 0)
       goto helper;
    }

  retval = 0;
  goto cleanup;

  /* We have to use the helper program.  */
 helper:

  pid = __fork ();
  if (pid == -1)
    goto cleanup;
  else if (pid == 0)
    {
      /* Disable core dumps.  */
      struct rlimit rl = { 0, 0 };
      __setrlimit (RLIMIT_CORE, &rl);

      /* We pass the master pseudo terminal as file descriptor PTY_FILENO.  */
      if (fd != PTY_FILENO)
       if (__dup2 (fd, PTY_FILENO) < 0)
         _exit (FAIL_EBADF);

      execle (_PATH_PT_CHOWN, basename (_PATH_PT_CHOWN), NULL, NULL);
      _exit (FAIL_EXEC);
    }
  else
    {
      int w;

      if (__waitpid (pid, &w, 0) == -1)
       goto cleanup;
      if (!WIFEXITED (w))
       __set_errno (ENOEXEC);
      else
       switch (WEXITSTATUS(w))
         {
         case 0:
           retval = 0;
           break;
         case FAIL_EBADF:
           __set_errno (EBADF);
           break;
         case FAIL_EINVAL:
           __set_errno (EINVAL);
           break;
         case FAIL_EACCES:
           __set_errno (EACCES);
           break;
         case FAIL_EXEC:
           __set_errno (ENOEXEC);
           break;

         default:
           assert(! "getpt: internal error: invalid exit code from pt_chown");
         }
    }

 cleanup:
  if (buf != _buf)
    free (buf);

  return retval;
}

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static int pts_name ( int  fd,
char **  pts,
size_t  buf_len 
) [static]

Definition at line 40 of file grantpt.c.

{
  int rv;
  char *buf = *pts;

  for (;;)
    {
      char *new_buf;

      if (buf_len)
       {
         rv = __ptsname_r (fd, buf, buf_len);
         if (rv != 0)
           {
             if (rv == ENOTTY)
              /* ptsname_r returns with ENOTTY to indicate
                 a descriptor not referring to a pty master.
                 For this condition, grantpt must return EINVAL.  */
              rv = EINVAL;
             errno = rv;    /* Not necessarily set by __ptsname_r.  */
             break;
           }

         if (memchr (buf, '\0', buf_len))
           /* We succeeded and the returned name fit in the buffer.  */
           break;

         /* Try again with a longer buffer.  */
         buf_len += buf_len;       /* Double it */
       }
      else
       /* No initial buffer; start out by mallocing one.  */
       buf_len = 128;              /* First time guess.  */

      if (buf != *pts)
       /* We've already malloced another buffer at least once.  */
       new_buf = (char *) realloc (buf, buf_len);
      else
       new_buf = (char *) malloc (buf_len);
      if (! new_buf)
       {
         rv = -1;
         __set_errno (ENOMEM);
         break;
       }
      buf = new_buf;
    }

  if (rv == 0)
    *pts = buf;             /* Return buffer to the user.  */
  else if (buf != *pts)
    free (buf);             /* Free what we malloced when returning an error.  */

  return rv;
}

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