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posix: Sync tempname with gnulib

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The gnulib version contains an important change (9ce573cde), which
fixes some problems with multithreading, entropy loss, and ASLR leak
nfo.  It also fixes an issue where getrandom is not being used
on some new files generation (only for __GT_NOCREATE on first try).

The 044bf893ac removed __path_search, which is now moved to another
gnulib shared files (stdio-common/tmpdir.{c,h}).  Tthis patch
also fixes direxists to use __stat64_time64 instead of __xstat64,
and move the include of pathmax.h for !_LIBC (since it is not used
by glibc).  The license is also changed from GPL 3.0 to 2.1, with
permission from the authors (Bruno Haible and Paul Eggert).

The sync also removed the clock fallback, since clock_gettime
with CLOCK_REALTIME is expected to always succeed.

It syncs with gnulib commit 323834962817af7b115187e8c9a833437f8d20ec.

Checked on x86_64-linux-gnu.

Co-authored-by: Bruno Haible <bruno@clisp.org>
Co-authored-by: Paul Eggert <eggert@cs.ucla.edu>
Reviewed-by: Bruno Haible <bruno@clisp.org>
This commit is contained in:
Adhemerval Zanella 2023-10-10 16:22:39 -03:00
parent 3a83f79024
commit 686d542025
12 changed files with 266 additions and 138 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
SHARED-FILES
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@ -111,6 +111,9 @@ gnulib:
string/strstr.c
string/strtok_r.c
string/strverscmp.c
# Merged from gnulib 2024-04-08 (gnulib commit 3238349628)
stdio-common/tmpdir.c
stdio-common/tmpdir.h
sysdeps/generic/pty-private.h
sysdeps/generic/siglist.h
sysdeps/posix/euidaccess.c
@ -118,7 +121,7 @@ gnulib:
sysdeps/posix/getcwd.c
sysdeps/posix/pwrite.c
sysdeps/posix/spawni.c
# Merged from gnulib 2014-6-23
# Merged from gnulib 2024-04-08 (gnulib commit 3238349628)
sysdeps/posix/tempname.c
# Merged from gnulib 2014-6-27
time/mktime.c

5
include/stdio.h
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@ -156,11 +156,6 @@ extern FILE *__old_tmpfile (void);
# include <bits/types/wint_t.h>
/* Generate a unique file name (and possibly open it). */
extern int __path_search (char *__tmpl, size_t __tmpl_len,
const char *__dir, const char *__pfx,
int __try_tempdir) attribute_hidden;
extern int __gen_tempname (char *__tmpl, int __suffixlen, int __flags,
int __kind) attribute_hidden;
/* The __kind argument to __gen_tempname may be one of: */

1
libio/oldtmpfile.c
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@ -22,6 +22,7 @@
#include <stdio.h>
#include <unistd.h>
#include <iolibio.h>
#include <stdio-common/tmpdir.h>
/* This returns a new stream opened on a temporary file (generated
by tmpnam). The file is opened with mode "w+b" (binary read/write).

1
stdio-common/Makefile
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@ -92,6 +92,7 @@ routines := \
sscanf \
tempnam \
tempname \
tmpdir \
tmpfile \
tmpfile64 \
tmpnam \

1
stdio-common/tempnam.c
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@ -17,6 +17,7 @@
#include <stdio.h>
#include <string.h>
#include "tmpdir.h"
/* Generate a unique temporary filename using up to five characters of
PFX if it is not NULL. The directory to put this file in is

12
stdio-common/tempname.c
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@ -20,18 +20,6 @@
#include <stdio.h>
#include <errno.h>
/* Perform the "SVID path search malarkey" on DIR and PFX. Write a
template suitable for use in __gen_tempname into TMPL, bounded
by TMPL_LEN. */
int
__path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
int try_tmpdir)
{
__set_errno (ENOSYS);
return -1;
}
stub_warning (__path_search)
/* Generate a (hopefully) unique temporary filename
in DIR (if applicable), using template TMPL.
KIND determines what to do with that name. It may be one of:

163
stdio-common/tmpdir.c Normal file
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@ -0,0 +1,163 @@
/* Copyright (C) 1999, 2001-2002, 2006, 2009-2024 Free Software Foundation,
Inc.
This file is part of the GNU C Library.
This file 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 file 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 sysdeps/posix/tempname.c. */
#include <config.h>
/* Specification. */
#include "tmpdir.h"
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#ifndef __set_errno
# define __set_errno(Val) errno = (Val)
#endif
#include <stdio.h>
#ifndef P_tmpdir
# ifdef _P_tmpdir /* native Windows */
# define P_tmpdir _P_tmpdir
# else
# define P_tmpdir "/tmp"
# endif
#endif
#include <sys/stat.h>
#if defined _WIN32 && ! defined __CYGWIN__
# define WIN32_LEAN_AND_MEAN /* avoid including junk */
# include <windows.h>
#endif
#if defined _WIN32 && ! defined __CYGWIN__
/* Don't assume that UNICODE is not defined. */
# undef GetTempPath
# define GetTempPath GetTempPathA
#endif
#if _LIBC
# define struct_stat64 struct __stat64_t64
#else
# include "pathmax.h"
# define struct_stat64 struct stat
# define __libc_secure_getenv secure_getenv
# define __stat64_time64(path, buf) stat (path, buf)
#endif
/* Pathname support.
ISSLASH(C) tests whether C is a directory separator character.
*/
#if defined _WIN32 || defined __CYGWIN__ || defined __EMX__ || defined __DJGPP__
/* Native Windows, Cygwin, OS/2, DOS */
# define ISSLASH(C) ((C) == '/' || (C) == '\\')
#else
/* Unix */
# define ISSLASH(C) ((C) == '/')
#endif
/* Return nonzero if DIR is an existent directory. */
static bool
direxists (const char *dir)
{
struct_stat64 buf;
return __stat64_time64 (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,
bool try_tmpdir)
{
const char *d;
size_t dlen, plen;
bool add_slash;
if (!pfx || !pfx[0])
{
pfx = "file";
plen = 4;
}
else
{
plen = strlen (pfx);
if (plen > 5)
plen = 5;
}
if (try_tmpdir)
{
d = __libc_secure_getenv ("TMPDIR");
if (d != NULL && direxists (d))
dir = d;
else if (dir != NULL && direxists (dir))
/* nothing */ ;
else
dir = NULL;
}
if (dir == NULL)
{
#if defined _WIN32 && ! defined __CYGWIN__
char dirbuf[PATH_MAX];
DWORD retval;
/* Find Windows temporary file directory.
We try this before P_tmpdir because Windows defines P_tmpdir to "\\"
and will therefore try to put all temporary files in the root
directory (unless $TMPDIR is set). */
retval = GetTempPath (PATH_MAX, dirbuf);
if (retval > 0 && retval < PATH_MAX && direxists (dirbuf))
dir = dirbuf;
else
#endif
if (direxists (P_tmpdir))
dir = P_tmpdir;
else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
dir = "/tmp";
else
{
__set_errno (ENOENT);
return -1;
}
}
dlen = strlen (dir);
#ifdef __VMS
add_slash = 0;
#else
add_slash = dlen != 0 && !ISSLASH (dir[dlen - 1]);
#endif
/* check we have room for "${dir}/${pfx}XXXXXX\0" */
if (tmpl_len < dlen + add_slash + plen + 6 + 1)
{
__set_errno (EINVAL);
return -1;
}
memcpy (tmpl, dir, dlen);
sprintf (tmpl + dlen, &"/%.*sXXXXXX"[!add_slash], (int) plen, pfx);
return 0;
}

28
stdio-common/tmpdir.h Normal file
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@ -0,0 +1,28 @@
/* Determine a temporary directory.
Copyright (C) 2001-2002, 2009-2024 Free Software Foundation, Inc.
This file 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 file 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/>. */
#include <stdbool.h>
#include <stddef.h>
/* 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. */
extern int __path_search (char *tmpl, size_t tmpl_len, const char *dir,
const char *pfx, bool try_tmpdir)
attribute_hidden;

1
stdio-common/tmpfile.c
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@ -19,6 +19,7 @@
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include "tmpdir.h"
#include <iolibio.h>
#define __fdopen _IO_fdopen

1
stdio-common/tmpnam.c
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@ -17,6 +17,7 @@
#include <stdio.h>
#include <string.h>
#include "tmpdir.h"
static char tmpnam_buffer[L_tmpnam];

1
stdio-common/tmpnam_r.c
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@ -16,6 +16,7 @@
<https://www.gnu.org/licenses/>. */
#include <stdio.h>
#include "tmpdir.h"
/* Generate a unique filename in P_tmpdir. If S is NULL return NULL.
This makes this function thread safe. */

183
sysdeps/posix/tempname.c
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@ -20,16 +20,9 @@
# include "tempname.h"
#endif
#include <sys/types.h>
#include <assert.h>
#include <stdbool.h>
#include <errno.h>
#include <stdio.h>
#ifndef P_tmpdir
# define P_tmpdir "/tmp"
#endif
#ifndef TMP_MAX
# define TMP_MAX 238328
#endif
@ -43,12 +36,10 @@
# error report this to bug-gnulib@gnu.org
#endif
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <stdalign.h>
#include <stdint.h>
#include <sys/random.h>
#include <sys/stat.h>
@ -56,14 +47,12 @@
#if _LIBC
# define struct_stat64 struct __stat64_t64
# define __secure_getenv __libc_secure_getenv
#else
# define struct_stat64 struct stat
# define __gen_tempname gen_tempname
# define __mkdir mkdir
# define __open open
# define __lstat64_time64(file, buf) lstat (file, buf)
# define __stat64(file, buf) stat (file, buf)
# define __getrandom getrandom
# define __clock_gettime64 clock_gettime
# define __timespec64 timespec
@ -77,95 +66,61 @@ typedef uint_fast64_t random_value;
#define BASE_62_DIGITS 10 /* 62**10 < UINT_FAST64_MAX */
#define BASE_62_POWER (62LL * 62 * 62 * 62 * 62 * 62 * 62 * 62 * 62 * 62)
/* Return the result of mixing the entropy from R and S.
Assume that R and S are not particularly random,
and that the result should look randomish to an untrained eye. */
static random_value
random_bits (random_value var, bool use_getrandom)
mix_random_values (random_value r, random_value s)
{
/* As this code is used only when high-quality randomness is neither
available nor necessary, there is no need for fancier polynomials
such as those in the Linux kernel's 'random' driver. */
return (2862933555777941757 * r + 3037000493) ^ s;
}
/* Set *R to a random value.
Return true if *R is set to high-quality value taken from getrandom.
Otherwise return false, falling back to a low-quality *R that might
depend on S.
This function returns false only when getrandom fails.
On GNU systems this should happen only early in the boot process,
when the fallback should be good enough for programs using tempname
because any attacker likely has root privileges already. */
static bool
random_bits (random_value *r, random_value s)
{
random_value r;
/* Without GRND_NONBLOCK it can be blocked for minutes on some systems. */
if (use_getrandom && __getrandom (&r, sizeof r, GRND_NONBLOCK) == sizeof r)
return r;
#if _LIBC || (defined CLOCK_MONOTONIC && HAVE_CLOCK_GETTIME)
/* Add entropy if getrandom did not work. */
if (__getrandom (r, sizeof *r, GRND_NONBLOCK) == sizeof *r)
return true;
/* If getrandom did not work, use ersatz entropy based on low-order
clock bits. On GNU systems getrandom should fail only
early in booting, when ersatz should be good enough.
Do not use ASLR-based entropy, as that would leak ASLR info into
the resulting file name which is typically public.
Of course we are in a state of sin here. */
random_value v = s;
#if _LIBC || (defined CLOCK_REALTIME && HAVE_CLOCK_GETTIME)
struct __timespec64 tv;
__clock_gettime64 (CLOCK_MONOTONIC, &tv);
var ^= tv.tv_nsec;
__clock_gettime64 (CLOCK_REALTIME, &tv);
v = mix_random_values (v, tv.tv_sec);
v = mix_random_values (v, tv.tv_nsec);
#endif
return 2862933555777941757 * var + 3037000493;
}
#if _LIBC
/* Return nonzero if DIR is an existent directory. */
static int
direxists (const char *dir)
{
struct_stat64 buf;
return __stat64_time64 (dir, &buf) == 0 && S_ISDIR (buf.st_mode);
/* In glibc, clock_gettime with CLOCK_REALTIME is expected to always
succeed. */
#if !_LIBC
*r = mix_random_values (v, clock ());
#endif
return false;
}
/* 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 */
#if _LIBC
static int try_tempname_len (char *, int, void *, int (*) (char *, void *),
size_t);
@ -213,7 +168,7 @@ static const char letters[] =
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. */
*/
#ifdef _LIBC
static
#endif
@ -242,7 +197,7 @@ try_tempname_len (char *tmpl, int suffixlen, void *args,
char *XXXXXX;
unsigned int count;
int fd = -1;
int save_errno = errno;
int saved_errno = errno;
/* A lower bound on the number of temporary files to attempt to
generate. The maximum total number of temporary file names that
@ -261,25 +216,17 @@ try_tempname_len (char *tmpl, int suffixlen, void *args,
unsigned int attempts = ATTEMPTS_MIN;
#endif
/* A random variable. The initial value is used only the for fallback path
on 'random_bits' on 'getrandom' failure. Its initial value tries to use
some entropy from the ASLR and ignore possible bits from the stack
alignment. */
random_value v = ((uintptr_t) &v) / alignof (max_align_t);
/* A random variable. */
random_value v = 0;
/* How many random base-62 digits can currently be extracted from V. */
/* A value derived from the random variable, and how many random
base-62 digits can currently be extracted from VDIGBUF. */
random_value vdigbuf;
int vdigits = 0;
/* Whether to consume entropy when acquiring random bits. On the
first try it's worth the entropy cost with __GT_NOCREATE, which
is inherently insecure and can use the entropy to make it a bit
less secure. On the (rare) second and later attempts it might
help against DoS attacks. */
bool use_getrandom = tryfunc == try_nocreate;
/* Least unfair value for V. If V is less than this, V can generate
BASE_62_DIGITS digits fairly. Otherwise it might be biased. */
random_value const unfair_min
/* Least biased value for V. If V is less than this, V can generate
BASE_62_DIGITS unbiased digits. Otherwise the digits are biased. */
random_value const biased_min
= RANDOM_VALUE_MAX - RANDOM_VALUE_MAX % BASE_62_POWER;
len = strlen (tmpl);
@ -299,25 +246,23 @@ try_tempname_len (char *tmpl, int suffixlen, void *args,
{
if (vdigits == 0)
{
do
{
v = random_bits (v, use_getrandom);
use_getrandom = true;
}
while (unfair_min <= v);
/* Worry about bias only if the bits are high quality. */
while (random_bits (&v, v) && biased_min <= v)
continue;
vdigbuf = v;
vdigits = BASE_62_DIGITS;
}
XXXXXX[i] = letters[v % 62];
v /= 62;
XXXXXX[i] = letters[vdigbuf % 62];
vdigbuf /= 62;
vdigits--;
}
fd = tryfunc (tmpl, args);
if (fd >= 0)
{
__set_errno (save_errno);
__set_errno (saved_errno);
return fd;
}
else if (errno != EEXIST)