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posix: Sync tempname with gnulib [BZ #26648]

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It syncs with gnulib commit b1268f22f443e8e4b9e.  The try_tempname_len
now uses getrandom on each iteration to get entropy and only uses the
clock plus ASLR as source of entropy if getrandom fails.

Checked on x86_64-linux-gnu and i686-linux-gnu.
This commit is contained in:
Adhemerval Zanella 2020-09-29 08:56:07 -03:00
parent 42dda89dcb
commit 4dddd7e9cb
1 changed files with 161 additions and 113 deletions
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274
sysdeps/posix/tempname.c
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@ -16,7 +16,7 @@
<https://www.gnu.org/licenses/>. */
#if !_LIBC
# include <config.h>
# include <libc-config.h>
# include "tempname.h"
#endif
@ -24,9 +24,6 @@
#include <assert.h>
#include <errno.h>
#ifndef __set_errno
# define __set_errno(Val) errno = (Val)
#endif
#include <stdio.h>
#ifndef P_tmpdir
@ -36,12 +33,12 @@
# define TMP_MAX 238328
#endif
#ifndef __GT_FILE
# define __GT_FILE 0
# define __GT_DIR 1
# define __GT_NOCREATE 2
# 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)
#if !_LIBC && (GT_FILE != __GT_FILE || GT_DIR != __GT_DIR \
|| GT_NOCREATE != __GT_NOCREATE)
# error report this to bug-gnulib@gnu.org
#endif
@ -50,11 +47,11 @@
#include <string.h>
#include <fcntl.h>
#include <time.h>
#include <stdalign.h>
#include <stdint.h>
#include <unistd.h>
#include <sys/random.h>
#include <sys/stat.h>
#include <time.h>
#if _LIBC
# define struct_stat64 struct stat64
@ -62,32 +59,38 @@
#else
# define struct_stat64 struct stat
# define __gen_tempname gen_tempname
# define __getpid getpid
# define __mkdir mkdir
# define __open open
# define __secure_getenv secure_getenv
# define __lstat64(file, buf) lstat (file, buf)
# define __stat64(file, buf) stat (file, buf)
# define __getrandom getrandom
# define __clock_gettime64 clock_gettime
# define __timespec64 timespec
#endif
#ifdef _LIBC
# include <random-bits.h>
# define RANDOM_BITS(Var) ((Var) = random_bits ())
# else
# define RANDOM_BITS(Var) \
{ \
struct timespec ts; \
clock_gettime (CLOCK_REALTIME, &ts); \
(Var) = ((uint64_t) tv.tv_nsec << 16) ^ tv.tv_sec; \
}
#endif
/* Use getrandom if it works, falling back on a 64-bit linear
congruential generator that starts with Var's value
mixed in with a clock's low-order bits if available. */
typedef uint_fast64_t random_value;
#define RANDOM_VALUE_MAX UINT_FAST64_MAX
#define BASE_62_DIGITS 10 /* 62**10 < UINT_FAST64_MAX */
#define BASE_62_POWER (62LL * 62 * 62 * 62 * 62 * 62 * 62 * 62 * 62 * 62)
/* 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
static random_value
random_bits (random_value var)
{
random_value r;
/* Without GRND_NONBLOCK it can be blocked for minutes on some systems. */
if (__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. */
struct __timespec64 tv;
__clock_gettime64 (CLOCK_MONOTONIC, &tv);
var ^= tv.tv_nsec;
#endif
return 2862933555777941757 * var + 3037000493;
}
#if _LIBC
/* Return nonzero if DIR is an existent directory. */
@ -106,7 +109,7 @@ direxists (const char *dir)
enough space in TMPL. */
int
__path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
int try_tmpdir)
int try_tmpdir)
{
const char *d;
size_t dlen, plen;
@ -120,35 +123,35 @@ __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
{
plen = strlen (pfx);
if (plen > 5)
plen = 5;
plen = 5;
}
if (try_tmpdir)
{
d = __secure_getenv ("TMPDIR");
if (d != NULL && direxists (d))
dir = d;
dir = d;
else if (dir != NULL && direxists (dir))
/* nothing */ ;
/* nothing */ ;
else
dir = NULL;
dir = NULL;
}
if (dir == NULL)
{
if (direxists (P_tmpdir))
dir = P_tmpdir;
dir = P_tmpdir;
else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
dir = "/tmp";
dir = "/tmp";
else
{
__set_errno (ENOENT);
return -1;
}
{
__set_errno (ENOENT);
return -1;
}
}
dlen = strlen (dir);
while (dlen > 1 && dir[dlen - 1] == '/')
dlen--; /* remove trailing slashes */
dlen--; /* remove trailing slashes */
/* check we have room for "${dir}/${pfx}XXXXXX\0" */
if (tmpl_len < dlen + 1 + plen + 6 + 1)
@ -162,39 +165,91 @@ __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
}
#endif /* _LIBC */
#if _LIBC
static int try_tempname_len (char *, int, void *, int (*) (char *, void *),
size_t);
#endif
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 (__lstat64 (tmpl, &st) == 0 || errno == EOVERFLOW)
__set_errno (EEXIST);
return errno == ENOENT ? 0 : -1;
}
/* 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).
rules for mk[s]temp (i.e., end in at least X_SUFFIX_LEN "X"s,
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.
this function. 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.
__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. */
#ifdef _LIBC
static
#endif
int
__gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
gen_tempname_len (char *tmpl, int suffixlen, int flags, int kind,
size_t x_suffix_len)
{
int len;
static int (*const tryfunc[]) (char *, void *) =
{
[__GT_FILE] = try_file,
[__GT_DIR] = try_dir,
[__GT_NOCREATE] = try_nocreate
};
return try_tempname_len (tmpl, suffixlen, &flags, tryfunc[kind],
x_suffix_len);
}
#ifdef _LIBC
static
#endif
int
try_tempname_len (char *tmpl, int suffixlen, void *args,
int (*tryfunc) (char *, void *), size_t x_suffix_len)
{
size_t len;
char *XXXXXX;
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. */
give the system administrator the chance to remove the problems.
This value requires that X_SUFFIX_LEN be at least 3. */
#define ATTEMPTS_MIN (62 * 62 * 62)
/* The number of times to attempt to generate a temporary file. To
@ -205,82 +260,75 @@ __gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
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);
/* How many random base-62 digits can currently be extracted from V. */
int vdigits = 0;
/* 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
= RANDOM_VALUE_MAX - RANDOM_VALUE_MAX % BASE_62_POWER;
len = strlen (tmpl);
if (len < 6 + suffixlen || memcmp (&tmpl[len - 6 - suffixlen], "XXXXXX", 6))
if (len < x_suffix_len + suffixlen
|| strspn (&tmpl[len - x_suffix_len - suffixlen], "X") < x_suffix_len)
{
__set_errno (EINVAL);
return -1;
}
/* This is where the Xs start. */
XXXXXX = &tmpl[len - 6 - suffixlen];
XXXXXX = &tmpl[len - x_suffix_len - suffixlen];
uint64_t pid = (uint64_t) __getpid () << 32;
for (count = 0; count < attempts; ++count)
{
uint64_t v;
/* Get some more or less random data. */
RANDOM_BITS (v);
v ^= pid;
for (size_t i = 0; i < x_suffix_len; i++)
{
if (vdigits == 0)
{
do
v = random_bits (v);
while (unfair_min <= v);
/* 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];
vdigits = BASE_62_DIGITS;
}
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 lstat fails because the name does not exist.
Note the continue to bypass the common logic at the bottom
of the loop. */
if (__lstat64 (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 ();
}
XXXXXX[i] = letters[v % 62];
v /= 62;
vdigits--;
}
fd = tryfunc (tmpl, args);
if (fd >= 0)
{
__set_errno (save_errno);
return fd;
}
{
__set_errno (save_errno);
return fd;
}
else if (errno != EEXIST)
return -1;
return -1;
}
/* We got out of the loop because we ran out of combinations to try. */
__set_errno (EEXIST);
return -1;
}
int
__gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
{
return gen_tempname_len (tmpl, suffixlen, flags, kind, 6);
}
#if !_LIBC
int
try_tempname (char *tmpl, int suffixlen, void *args,
int (*tryfunc) (char *, void *))
{
return try_tempname_len (tmpl, suffixlen, args, tryfunc, 6);
}
#endif