/* tempname.c - generate the name of a temporary file.

   Copyright (C) 1991-2003, 2005-2007, 2009-2019 Free Software Foundation, Inc.

   This program 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 program 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/>.  */

/* Extracted from glibc sysdeps/posix/tempname.c.  See also tmpdir.c.  */

#if !_LIBC

# include <config.h>

# include "tempname.h"

#endif

#include <sys/types.h>

#include <assert.h>

#include <errno.h>

#ifndef __set_errno

# define __set_errno(Val) errno = (Val)

#endif

#include <stdio.h>

#ifndef P_tmpdir

# define P_tmpdir "/tmp"

#endif

#ifndef TMP_MAX

# define TMP_MAX 238328

#endif

#ifndef __GT_FILE

# define __GT_FILE      0

# define __GT_DIR       1

# define __GT_NOCREATE  2

#endif

#if !_LIBC && (GT_FILE != __GT_FILE || GT_DIR != __GT_DIR       \

               || GT_NOCREATE != __GT_NOCREATE)

# error report this to bug-gnulib@gnu.org

#endif

#include <stddef.h>

#include <stdlib.h>

#include <string.h>

#include <fcntl.h>

#include <sys/time.h>

#include <stdint.h>

#include <unistd.h>

#include <sys/stat.h>

#if _LIBC

# define struct_stat64 struct stat64

#else

# define struct_stat64 struct stat

# define __try_tempname try_tempname

# define __gen_tempname gen_tempname

# define __getpid getpid

# define __gettimeofday gettimeofday

# define __mkdir mkdir

# define __open open

# define __lxstat64(version, file, buf) lstat (file, buf)

#endif

#ifdef _LIBC

# include <hp-timing.h>

# if HP_TIMING_AVAIL

#  define RANDOM_BITS(Var) \

  if (__builtin_expect (value == UINT64_C (0), 0))                            \

    {                                                                         \

      /* If this is the first time this function is used initialize           \

         the variable we accumulate the value in to some somewhat             \

         random value.  If we'd not do this programs at startup time          \

         might have a reduced set of possible names, at least on slow         \

         machines.  */                                                        \

      struct timeval tv;                                                      \

      __gettimeofday (&tv, NULL);                                             \

      value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;                      \

    }                                                                         \

  HP_TIMING_NOW (Var)

# endif

#endif

/* Use the widest available unsigned type if uint64_t is not

   available.  The algorithm below extracts a number less than 62**6

   (approximately 2**35.725) from uint64_t, so ancient hosts where

   uintmax_t is only 32 bits lose about 3.725 bits of randomness,

   which is better than not having mkstemp at all.  */

#if !defined UINT64_MAX && !defined uint64_t

# define uint64_t uintmax_t

#endif

#if _LIBC

/* Return nonzero if DIR is an existent directory.  */

static int

direxists (const char *dir)

{

  struct_stat64 buf;

  return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);

}

/* Path search algorithm, for tmpnam, tmpfile, etc.  If DIR is

   non-null and exists, uses it; otherwise uses the first of $TMPDIR,

   P_tmpdir, /tmp that exists.  Copies into TMPL a template suitable

   for use with mk[s]temp.  Will fail (-1) if DIR is non-null and

   doesn't exist, none of the searched dirs exists, or there's not

   enough space in TMPL. */

int

__path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,

               int try_tmpdir)

{

  const char *d;

  size_t dlen, plen;

  if (!pfx || !pfx[0])

    {

      pfx = "file";

      plen = 4;

    }

  else

    {

      plen = strlen (pfx);

      if (plen > 5)

        plen = 5;

    }

  if (try_tmpdir)

    {

      d = __secure_getenv ("TMPDIR");

      if (d != NULL && direxists (d))

        dir = d;

      else if (dir != NULL && direxists (dir))

        /* nothing */ ;

      else

        dir = NULL;

    }

  if (dir == NULL)

    {

      if (direxists (P_tmpdir))

        dir = P_tmpdir;

      else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))

        dir = "/tmp";

      else

        {

          __set_errno (ENOENT);

          return -1;

        }

    }

  dlen = strlen (dir);

  while (dlen > 1 && dir[dlen - 1] == '/')

    dlen--;                     /* remove trailing slashes */

  /* check we have room for "${dir}/${pfx}XXXXXX\0" */

  if (tmpl_len < dlen + 1 + plen + 6 + 1)

    {

      __set_errno (EINVAL);

      return -1;

    }

  sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);

  return 0;

}

#endif /* _LIBC */

/* These are the characters used in temporary file names.  */

static const char letters[] =

"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

int

__try_tempname (char *tmpl, int suffixlen, void *args,

                int (*tryfunc) (char *, void *))

{

  int len;

  char *XXXXXX;

  static uint64_t value;

  uint64_t random_time_bits;

  unsigned int count;

  int fd = -1;

  int save_errno = errno;

  /* A lower bound on the number of temporary files to attempt to

     generate.  The maximum total number of temporary file names that

     can exist for a given template is 62**6.  It should never be

     necessary to try all of these combinations.  Instead if a reasonable

     number of names is tried (we define reasonable as 62**3) fail to

     give the system administrator the chance to remove the problems.  */

#define ATTEMPTS_MIN (62 * 62 * 62)

  /* The number of times to attempt to generate a temporary file.  To

     conform to POSIX, this must be no smaller than TMP_MAX.  */

#if ATTEMPTS_MIN < TMP_MAX

  unsigned int attempts = TMP_MAX;

#else

  unsigned int attempts = ATTEMPTS_MIN;

#endif

  len = strlen (tmpl);

  if (len < 6 + suffixlen || memcmp (&tmpl[len - 6 - suffixlen], "XXXXXX", 6))

    {

      __set_errno (EINVAL);

      return -1;

    }

  /* This is where the Xs start.  */

  XXXXXX = &tmpl[len - 6 - suffixlen];

  /* Get some more or less random data.  */

#ifdef RANDOM_BITS

  RANDOM_BITS (random_time_bits);

#else

  {

    struct timeval tv;

    __gettimeofday (&tv, NULL);

    random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;

  }

#endif

  value += random_time_bits ^ __getpid ();

  for (count = 0; count < attempts; value += 7777, ++count)

    {

      uint64_t v = value;

      /* Fill in the random bits.  */

      XXXXXX[0] = letters[v % 62];

      v /= 62;

      XXXXXX[1] = letters[v % 62];

      v /= 62;

      XXXXXX[2] = letters[v % 62];

      v /= 62;

      XXXXXX[3] = letters[v % 62];

      v /= 62;

      XXXXXX[4] = letters[v % 62];

      v /= 62;

      XXXXXX[5] = letters[v % 62];

      fd = tryfunc (tmpl, args);

      if (fd >= 0)

        {

          __set_errno (save_errno);

          return fd;

        }

      else if (errno != EEXIST)

        return -1;

    }

  /* We got out of the loop because we ran out of combinations to try.  */

  __set_errno (EEXIST);

  return -1;

}

static int

try_file (char *tmpl, void *flags)

{

  int *openflags = flags;

  return __open (tmpl,

                 (*openflags & ~O_ACCMODE)

                 | O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);

}

static int

try_dir (char *tmpl, void *flags _GL_UNUSED)

{

  return __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);

}

static int

try_nocreate (char *tmpl, void *flags _GL_UNUSED)

{

  struct_stat64 st;

  if (__lxstat64 (_STAT_VER, tmpl, &st) == 0 || errno == EOVERFLOW)

    __set_errno (EEXIST);

  return errno == ENOENT ? 0 : -1;

}

/* Generate a temporary file name based on TMPL.  TMPL must match the

   rules for mk[s]temp (i.e. end in "XXXXXX", possibly with a suffix).

   The name constructed does not exist at the time of the call to

   __gen_tempname.  TMPL is overwritten with the result.

   KIND may be one of:

   __GT_NOCREATE:       simply verify that the name does not exist

                        at the time of the call.

   __GT_FILE:           create the file using open(O_CREAT|O_EXCL)

                        and return a read-write fd.  The file is mode 0600.

   __GT_DIR:            create a directory, which will be mode 0700.

   We use a clever algorithm to get hard-to-predict names. */

int

__gen_tempname (char *tmpl, int suffixlen, int flags, int kind)

{

  int (*tryfunc) (char *, void *);

  switch (kind)

    {

    case __GT_FILE:

      tryfunc = try_file;

      break;

    case __GT_DIR:

      tryfunc = try_dir;

      break;

    case __GT_NOCREATE:

      tryfunc = try_nocreate;

      break;

    default:

      assert (! "invalid KIND in __gen_tempname");

      abort ();

    }

  return __try_tempname (tmpl, suffixlen, &flags, tryfunc);

}