Fix some minor races in hosts lacking mkostemp.

Gnulib's emulation of mkostemp doesn't have races that Emacs's does.
* configure.ac (mkostemp): Remove check for this function;
gnulib does the check now.
(mkstemp): Remove check for this no-longer-used function.
* lib/mkostemp.c, lib/secure_getenv.c, lib/tempname.c, lib/tempname.h:
* m4/mkostemp.m4, m4/secure_getenv.m4, m4/tempname.m4:
New files, copied from Gnulib.
* lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.
* admin/merge-gnulib (GNULIB_MODULES): Add mkostemp.
* lib-src/movemail.c (main):
* lib-src/update-game-score.c (write_scores):
Use mkostemp (which now works on all platforms, due to changes
in the portability layer) rather than mktemp (which has a race)
or mkstemp (which we no longer bother with).
* src/callproc.c (create_temp_file):
* src/filelock.c (create_lock_file):
Assume mkostemp, since it's now provided by Gnulib.

Fixes: debbugs:15015

ChangeLog

@@ -1,3 +1,15 @@
+2013-08-04  Paul Eggert  <eggert@cs.ucla.edu>
+
+	Fix some minor races in hosts lacking mkostemp (Bug#15015).
+	Gnulib's emulation of mkostemp doesn't have races that Emacs's does.
+	* configure.ac (mkostemp): Remove check for this function;
+	gnulib does the check now.
+	(mkstemp): Remove check for this no-longer-used function.
+	* lib/mkostemp.c, lib/secure_getenv.c, lib/tempname.c, lib/tempname.h:
+	* m4/mkostemp.m4, m4/secure_getenv.m4, m4/tempname.m4:
+	New files, copied from Gnulib.
+	* lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.
+
 2013-07-29  Michael Albinus  <michael.albinus@gmx.de>
 
 	* INSTALL (DETAILED BUILDING AND INSTALLATION): Add

admin/ChangeLog

@@ -1,3 +1,8 @@
+2013-08-04  Paul Eggert  <eggert@cs.ucla.edu>
+
+	Fix some minor races in hosts lacking mkostemp (Bug#15015).
+	* merge-gnulib (GNULIB_MODULES): Add mkostemp.
+
 2013-07-12  Glenn Morris  <rgm@gnu.org>
 
 	* admin.el (manual-style-string): Use non-abbreviated url.

admin/merge-gnulib

@@ -32,7 +32,7 @@ GNULIB_MODULES='
   fcntl fcntl-h fdatasync fdopendir filemode fstatat fsync
   getloadavg getopt-gnu gettime gettimeofday
   intprops largefile lstat
-  manywarnings memrchr mktime
+  manywarnings memrchr mkostemp mktime
   pipe2 pselect pthread_sigmask putenv qacl readlink readlinkat
   sig2str socklen stat-time stdalign stdarg stdbool stdio
   strftime strtoimax strtoumax symlink sys_stat

configure.ac

@@ -3277,7 +3277,7 @@ select getpagesize setlocale \
 getrlimit setrlimit shutdown getaddrinfo \
 strsignal setitimer \
 sendto recvfrom getsockname getpeername getifaddrs freeifaddrs \
-gai_strerror mkostemp mkstemp getline getdelim sync \
+gai_strerror getline getdelim sync \
 difftime posix_memalign \
 getpwent endpwent getgrent endgrent \
 touchlock \

lib-src/ChangeLog

@@ -1,3 +1,12 @@
+2013-08-04  Paul Eggert  <eggert@cs.ucla.edu>
+
+	Fix some minor races in hosts lacking mkostemp (Bug#15015).
+	* movemail.c (main):
+	* update-game-score.c (write_scores):
+	Use mkostemp (which now works on all platforms, due to changes
+	in the portability layer) rather than mktemp (which has a race)
+	or mkstemp (which we no longer bother with).
+
 2013-07-10  Paul Eggert  <eggert@cs.ucla.edu>
 
 	Port to C89.

lib-src/movemail.c

@@ -304,24 +304,13 @@ main (int argc, char **argv)
 
 	  memcpy (tempname, inname, inname_dirlen);
 	  strcpy (tempname + inname_dirlen, "EXXXXXX");
-#ifdef HAVE_MKSTEMP
+	  desc = mkostemp (tempname, 0);
-	  desc = mkstemp (tempname);
-#else
-	  mktemp (tempname);
-	  if (!*tempname)
-	    desc = -1;
-	  else
-	    {
-	      unlink (tempname);
-	      desc = open (tempname, O_WRONLY | O_CREAT | O_EXCL, 0600);
-	    }
-#endif
 	  if (desc < 0)
 	    {
-	      int mkstemp_errno = errno;
+	      int mkostemp_errno = errno;
 	      error ("error while creating what would become the lock file",
 		     0, 0);
-	      errno = mkstemp_errno;
+	      errno = mkostemp_errno;
 	      pfatal_with_name (tempname);
 	    }
 	  close (desc);

lib-src/update-game-score.c

@@ -383,6 +383,7 @@ sort_scores (struct score_entry *scores, int count, int reverse)
 static int
 write_scores (const char *filename, const struct score_entry *scores, int count)
 {
+  int fd;
   FILE *f;
   int i;
   char *tempfile = malloc (strlen (filename) + strlen (".tempXXXXXX") + 1);
@@ -390,12 +391,11 @@ write_scores (const char *filename, const struct score_entry *scores, int count)
     return -1;
   strcpy (tempfile, filename);
   strcat (tempfile, ".tempXXXXXX");
-#ifdef HAVE_MKSTEMP
+  fd = mkostemp (tempfile, 0);
-  if (mkstemp (tempfile) < 0
+  if (fd < 0)
-#else
+    return -1;
-  if (mktemp (tempfile) != tempfile
+  f = fdopen (fd, "w");
-#endif
+  if (! f)
-      || !(f = fopen (tempfile, "w")))
     return -1;
   for (i = 0; i < count; i++)
     if (fprintf (f, "%ld %s %s\n", scores[i].score, scores[i].username,

lib/gnulib.mk

@@ -21,7 +21,7 @@
 # the same distribution terms as the rest of that program.
 #
 # Generated by gnulib-tool.
-# Reproduce by: gnulib-tool --import --dir=. --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=close --avoid=dup --avoid=fchdir --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=sigprocmask --avoid=sys_types --avoid=threadlib --makefile-name=gnulib.mk --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt c-ctype c-strcase careadlinkat close-stream crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dtotimespec dup2 environ execinfo faccessat fcntl fcntl-h fdatasync fdopendir filemode fstatat fsync getloadavg getopt-gnu gettime gettimeofday intprops largefile lstat manywarnings memrchr mktime pipe2 pselect pthread_sigmask putenv qacl readlink readlinkat sig2str socklen stat-time stdalign stdarg stdbool stdio strftime strtoimax strtoumax symlink sys_stat sys_time time timer-time timespec-add timespec-sub unsetenv utimens warnings
+# Reproduce by: gnulib-tool --import --dir=. --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=close --avoid=dup --avoid=fchdir --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=sigprocmask --avoid=sys_types --avoid=threadlib --makefile-name=gnulib.mk --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt c-ctype c-strcase careadlinkat close-stream crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dtotimespec dup2 environ execinfo faccessat fcntl fcntl-h fdatasync fdopendir filemode fstatat fsync getloadavg getopt-gnu gettime gettimeofday intprops largefile lstat manywarnings memrchr mkostemp mktime pipe2 pselect pthread_sigmask putenv qacl readlink readlinkat sig2str socklen stat-time stdalign stdarg stdbool stdio strftime strtoimax strtoumax symlink sys_stat sys_time time timer-time timespec-add timespec-sub unsetenv utimens warnings
 
 
 MOSTLYCLEANFILES += core *.stackdump
@@ -560,6 +560,15 @@ EXTRA_libgnu_a_SOURCES += memrchr.c
 
 ## end   gnulib module memrchr
 
+## begin gnulib module mkostemp
+
+
+EXTRA_DIST += mkostemp.c
+
+EXTRA_libgnu_a_SOURCES += mkostemp.c
+
+## end   gnulib module mkostemp
+
 ## begin gnulib module mktime
 
 
@@ -657,6 +666,17 @@ EXTRA_DIST += root-uid.h
 
 ## end   gnulib module root-uid
 
+## begin gnulib module secure_getenv
+
+if gl_GNULIB_ENABLED_secure_getenv
+
+endif
+EXTRA_DIST += secure_getenv.c
+
+EXTRA_libgnu_a_SOURCES += secure_getenv.c
+
+## end   gnulib module secure_getenv
+
 ## begin gnulib module sig2str
 
 
@@ -1480,6 +1500,16 @@ EXTRA_DIST += sys_time.in.h
 
 ## end   gnulib module sys_time
 
+## begin gnulib module tempname
+
+if gl_GNULIB_ENABLED_tempname
+libgnu_a_SOURCES += tempname.c
+
+endif
+EXTRA_DIST += tempname.h
+
+## end   gnulib module tempname
+
 ## begin gnulib module time
 
 BUILT_SOURCES += time.h

lib/mkostemp.c

@@ -0,0 +1,46 @@
+/* Copyright (C) 1998-1999, 2001, 2005-2007, 2009-2013 Free Software
+   Foundation, Inc.
+   This file is derived from the one in the GNU C Library.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#if !_LIBC
+# include <config.h>
+#endif
+
+#include <stdlib.h>
+
+#if !_LIBC
+# include "tempname.h"
+# define __gen_tempname gen_tempname
+# ifndef __GTFILE
+#  define __GT_FILE GT_FILE
+# endif
+#endif
+
+#include <stdio.h>
+
+#ifndef __GT_FILE
+# define __GT_FILE 0
+#endif
+
+/* Generate a unique temporary file name from XTEMPLATE.
+   The last six characters of XTEMPLATE must be "XXXXXX";
+   they are replaced with a string that makes the file name unique.
+   Then open the file and return a fd. */
+int
+mkostemp (char *xtemplate, int flags)
+{
+  return __gen_tempname (xtemplate, 0, flags, __GT_FILE);
+}

lib/secure_getenv.c

@@ -0,0 +1,41 @@
+/* Look up an environment variable more securely.
+
+   Copyright 2013 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published
+   by the Free Software Foundation; either version 3 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
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+#include <stdlib.h>
+
+#if !HAVE___SECURE_GETENV
+# if HAVE_ISSETUGID
+#  include <unistd.h>
+# else
+#  undef issetugid
+#  define issetugid() 1
+# endif
+#endif
+
+char *
+secure_getenv (char const *name)
+{
+#if HAVE___SECURE_GETENV
+  return __secure_getenv (name);
+#else
+  if (issetugid ())
+    return 0;
+  return getenv (name);
+#endif
+}

lib/tempname.c

@@ -0,0 +1,306 @@
+/* tempname.c - generate the name of a temporary file.
+
+   Copyright (C) 1991-2003, 2005-2007, 2009-2013 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://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 __gen_tempname gen_tempname
+# define __getpid getpid
+# define __gettimeofday gettimeofday
+# define __mkdir mkdir
+# define __open open
+# define __lxstat64(version, file, buf) lstat (file, buf)
+# define __secure_getenv secure_getenv
+#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";
+
+/* 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 len;
+  char *XXXXXX;
+  static uint64_t value;
+  uint64_t random_time_bits;
+  unsigned int count;
+  int fd = -1;
+  int save_errno = errno;
+  struct_stat64 st;
+
+  /* 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];
+
+      switch (kind)
+        {
+        case __GT_FILE:
+          fd = __open (tmpl,
+                       (flags & ~O_ACCMODE)
+                       | O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
+          break;
+
+        case __GT_DIR:
+          fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
+          break;
+
+        case __GT_NOCREATE:
+          /* This case is backward from the other three.  __gen_tempname
+             succeeds if __xstat fails because the name does not exist.
+             Note the continue to bypass the common logic at the bottom
+             of the loop.  */
+          if (__lxstat64 (_STAT_VER, tmpl, &st) < 0)
+            {
+              if (errno == ENOENT)
+                {
+                  __set_errno (save_errno);
+                  return 0;
+                }
+              else
+                /* Give up now. */
+                return -1;
+            }
+          continue;
+
+        default:
+          assert (! "invalid KIND in __gen_tempname");
+          abort ();
+        }
+
+      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;
+}

lib/tempname.h

@@ -0,0 +1,50 @@
+/* Create a temporary file or directory.
+
+   Copyright (C) 2006, 2009-2013 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* header written by Eric Blake */
+
+#ifndef GL_TEMPNAME_H
+# define GL_TEMPNAME_H
+
+# include <stdio.h>
+
+# ifdef __GT_FILE
+#  define GT_FILE     __GT_FILE
+#  define GT_DIR      __GT_DIR
+#  define GT_NOCREATE __GT_NOCREATE
+# else
+#  define GT_FILE     0
+#  define GT_DIR      1
+#  define GT_NOCREATE 2
+# endif
+
+/* 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 a large 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. */
+extern int gen_tempname (char *tmpl, int suffixlen, int flags, int kind);
+
+#endif /* GL_TEMPNAME_H */

m4/gnulib-comp.m4

@@ -89,6 +89,7 @@ AC_DEFUN([gl_EARLY],
   # Code from module lstat:
   # Code from module manywarnings:
   # Code from module memrchr:
+  # Code from module mkostemp:
   # Code from module mktime:
   # Code from module multiarch:
   # Code from module nocrash:
@@ -102,6 +103,7 @@ AC_DEFUN([gl_EARLY],
   # Code from module readlink:
   # Code from module readlinkat:
   # Code from module root-uid:
+  # Code from module secure_getenv:
   # Code from module sig2str:
   # Code from module signal-h:
   # Code from module snippet/_Noreturn:
@@ -134,6 +136,7 @@ AC_DEFUN([gl_EARLY],
   # Code from module sys_select:
   # Code from module sys_stat:
   # Code from module sys_time:
+  # Code from module tempname:
   # Code from module time:
   # Code from module time_r:
   # Code from module timer-time:
@@ -274,6 +277,13 @@ AC_DEFUN([gl_INIT],
     gl_PREREQ_MEMRCHR
   fi
   gl_STRING_MODULE_INDICATOR([memrchr])
+  gl_FUNC_MKOSTEMP
+  if test $HAVE_MKOSTEMP = 0; then
+    AC_LIBOBJ([mkostemp])
+    gl_PREREQ_MKOSTEMP
+  fi
+  gl_MODULE_INDICATOR([mkostemp])
+  gl_STDLIB_MODULE_INDICATOR([mkostemp])
   gl_FUNC_MKTIME
   if test $REPLACE_MKTIME = 1; then
     AC_LIBOBJ([mktime])
@@ -381,9 +391,11 @@ AC_DEFUN([gl_INIT],
   gl_gnulib_enabled_03e0aaad4cb89ca757653bd367a6ccb7=false
   gl_gnulib_enabled_pathmax=false
   gl_gnulib_enabled_6099e9737f757db36c47fa9d9f02e88c=false
+  gl_gnulib_enabled_secure_getenv=false
   gl_gnulib_enabled_stat=false
   gl_gnulib_enabled_strtoll=false
   gl_gnulib_enabled_strtoull=false
+  gl_gnulib_enabled_tempname=false
   gl_gnulib_enabled_682e609604ccaac6be382e4ee3a4eaec=false
   func_gl_gnulib_m4code_260941c0e5dc67ec9e87d1fb321c300b ()
   {
@@ -485,6 +497,18 @@ AC_DEFUN([gl_INIT],
       gl_gnulib_enabled_6099e9737f757db36c47fa9d9f02e88c=true
     fi
   }
+  func_gl_gnulib_m4code_secure_getenv ()
+  {
+    if ! $gl_gnulib_enabled_secure_getenv; then
+      gl_FUNC_SECURE_GETENV
+      if test $HAVE_SECURE_GETENV = 0; then
+        AC_LIBOBJ([secure_getenv])
+        gl_PREREQ_SECURE_GETENV
+      fi
+      gl_STDLIB_MODULE_INDICATOR([secure_getenv])
+      gl_gnulib_enabled_secure_getenv=true
+    fi
+  }
   func_gl_gnulib_m4code_stat ()
   {
     if ! $gl_gnulib_enabled_stat; then
@@ -527,6 +551,14 @@ AC_DEFUN([gl_INIT],
       gl_gnulib_enabled_strtoull=true
     fi
   }
+  func_gl_gnulib_m4code_tempname ()
+  {
+    if ! $gl_gnulib_enabled_tempname; then
+      gl_FUNC_GEN_TEMPNAME
+      gl_gnulib_enabled_tempname=true
+      func_gl_gnulib_m4code_secure_getenv
+    fi
+  }
   func_gl_gnulib_m4code_682e609604ccaac6be382e4ee3a4eaec ()
   {
     if ! $gl_gnulib_enabled_682e609604ccaac6be382e4ee3a4eaec; then
@@ -569,6 +601,9 @@ AC_DEFUN([gl_INIT],
   if test $REPLACE_LSTAT = 1; then
     func_gl_gnulib_m4code_stat
   fi
+  if test $HAVE_MKOSTEMP = 0; then
+    func_gl_gnulib_m4code_tempname
+  fi
   if test $HAVE_READLINK = 0 || test $REPLACE_READLINK = 1; then
     func_gl_gnulib_m4code_stat
   fi
@@ -598,9 +633,11 @@ AC_DEFUN([gl_INIT],
   AM_CONDITIONAL([gl_GNULIB_ENABLED_03e0aaad4cb89ca757653bd367a6ccb7], [$gl_gnulib_enabled_03e0aaad4cb89ca757653bd367a6ccb7])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_pathmax], [$gl_gnulib_enabled_pathmax])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_6099e9737f757db36c47fa9d9f02e88c], [$gl_gnulib_enabled_6099e9737f757db36c47fa9d9f02e88c])
+  AM_CONDITIONAL([gl_GNULIB_ENABLED_secure_getenv], [$gl_gnulib_enabled_secure_getenv])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_stat], [$gl_gnulib_enabled_stat])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_strtoll], [$gl_gnulib_enabled_strtoll])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_strtoull], [$gl_gnulib_enabled_strtoull])
+  AM_CONDITIONAL([gl_GNULIB_ENABLED_tempname], [$gl_gnulib_enabled_tempname])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_682e609604ccaac6be382e4ee3a4eaec], [$gl_gnulib_enabled_682e609604ccaac6be382e4ee3a4eaec])
   # End of code from modules
   m4_ifval(gl_LIBSOURCES_LIST, [
@@ -806,6 +843,7 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/md5.c
   lib/md5.h
   lib/memrchr.c
+  lib/mkostemp.c
   lib/mktime-internal.h
   lib/mktime.c
   lib/openat-priv.h
@@ -821,6 +859,7 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/readlink.c
   lib/readlinkat.c
   lib/root-uid.h
+  lib/secure_getenv.c
   lib/sha1.c
   lib/sha1.h
   lib/sha256.c
@@ -853,6 +892,8 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/sys_select.in.h
   lib/sys_stat.in.h
   lib/sys_time.in.h
+  lib/tempname.c
+  lib/tempname.h
   lib/time.in.h
   lib/time_r.c
   lib/timespec-add.c
@@ -908,6 +949,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/manywarnings.m4
   m4/md5.m4
   m4/memrchr.m4
+  m4/mkostemp.m4
   m4/mktime.m4
   m4/multiarch.m4
   m4/nocrash.m4
@@ -919,6 +961,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/putenv.m4
   m4/readlink.m4
   m4/readlinkat.m4
+  m4/secure_getenv.m4
   m4/setenv.m4
   m4/sha1.m4
   m4/sha256.m4
@@ -948,6 +991,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/sys_socket_h.m4
   m4/sys_stat_h.m4
   m4/sys_time_h.m4
+  m4/tempname.m4
   m4/time_h.m4
   m4/time_r.m4
   m4/timer_time.m4

m4/mkostemp.m4

@@ -0,0 +1,23 @@
+# mkostemp.m4 serial 2
+dnl Copyright (C) 2009-2013 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_MKOSTEMP],
+[
+  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
+
+  dnl Persuade glibc <stdlib.h> to declare mkostemp().
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+
+  AC_CHECK_FUNCS_ONCE([mkostemp])
+  if test $ac_cv_func_mkostemp != yes; then
+    HAVE_MKOSTEMP=0
+  fi
+])
+
+# Prerequisites of lib/mkostemp.c.
+AC_DEFUN([gl_PREREQ_MKOSTEMP],
+[
+])

m4/secure_getenv.m4

@@ -0,0 +1,25 @@
+# Look up an environment variable more securely.
+dnl Copyright 2013 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_SECURE_GETENV],
+[
+  dnl Persuade glibc <stdlib.h> to declare secure_getenv().
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+
+  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
+  AC_CHECK_FUNCS_ONCE([secure_getenv])
+  if test $ac_cv_func_secure_getenv = no; then
+    HAVE_SECURE_GETENV=0
+  fi
+])
+
+# Prerequisites of lib/secure_getenv.c.
+AC_DEFUN([gl_PREREQ_SECURE_GETENV], [
+  AC_CHECK_FUNCS([__secure_getenv])
+  if test $ac_cv_func___secure_getenv = no; then
+    AC_CHECK_FUNCS([issetugid])
+  fi
+])

m4/tempname.m4

@@ -0,0 +1,19 @@
+#serial 5
+
+# Copyright (C) 2006-2007, 2009-2013 Free Software Foundation, Inc.
+# This file is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+# glibc provides __gen_tempname as a wrapper for mk[ds]temp.  Expose
+# it as a public API, and provide it on systems that are lacking.
+AC_DEFUN([gl_FUNC_GEN_TEMPNAME],
+[
+  gl_PREREQ_TEMPNAME
+])
+
+# Prerequisites of lib/tempname.c.
+AC_DEFUN([gl_PREREQ_TEMPNAME],
+[
+  :
+])

src/ChangeLog

@@ -1,3 +1,10 @@
+2013-08-04  Paul Eggert  <eggert@cs.ucla.edu>
+
+	Fix some minor races in hosts lacking mkostemp (Bug#15015).
+	* callproc.c (create_temp_file):
+	* filelock.c (create_lock_file):
+	Assume mkostemp, since it's now provided by Gnulib.
+
 2013-08-04  Eli Zaretskii  <eliz@gnu.org>
 
 	* w32.c (mkostemp): New function.

src/callproc.c

@@ -1009,23 +1009,11 @@ create_temp_file (ptrdiff_t nargs, Lisp_Object *args)
     tempfile = SSDATA (filename_string);
 
     {
-      int fd;
+      int fd = mkostemp (tempfile, O_CLOEXEC);
-
-#ifdef HAVE_MKOSTEMP
-      fd = mkostemp (tempfile, O_CLOEXEC);
-#elif defined HAVE_MKSTEMP
-      fd = mkstemp (tempfile);
-#else
-      errno = EEXIST;
-      mktemp (tempfile);
-      fd = *tempfile ? 0 : -1;
-#endif
       if (fd < 0)
 	report_file_error ("Failed to open temporary file using pattern",
 			   pattern);
-#if defined HAVE_MKOSTEMP || defined HAVE_MKSTEMP
       emacs_close (fd);
-#endif
     }
 
     record_unwind_protect (delete_temp_file, filename_string);

src/filelock.c

@@ -411,28 +411,14 @@ create_lock_file (char *lfname, char *lock_info_str, bool force)
       memcpy (nonce, lfname, lfdirlen);
       strcpy (nonce + lfdirlen, nonce_base);
 
-#if HAVE_MKOSTEMP
-      /* Prefer mkostemp to mkstemp, as it avoids a window where FD is
-	 temporarily open without close-on-exec.  */
       fd = mkostemp (nonce, O_BINARY | O_CLOEXEC);
-#elif HAVE_MKSTEMP
-      /* Prefer mkstemp to mktemp, as it avoids a race between
-	 mktemp and emacs_open.  */
-      fd = mkstemp (nonce);
-#else
-      mktemp (nonce);
-      fd = emacs_open (nonce, O_WRONLY | O_CREAT | O_EXCL | O_BINARY,
-		       S_IRUSR | S_IWUSR);
-#endif
-
       if (fd < 0)
 	err = errno;
       else
 	{
 	  ptrdiff_t lock_info_len;
-#if ! (HAVE_MKOSTEMP && O_CLOEXEC)
+	  if (! O_CLOEXEC)
 	    fcntl (fd, F_SETFD, FD_CLOEXEC);
-#endif
 	  lock_info_len = strlen (lock_info_str);
 	  err = 0;
 	  /* Use 'write', not 'emacs_write', as garbage collection