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-rw-r--r--lib/tempname.c345
1 files changed, 345 insertions, 0 deletions
diff --git a/lib/tempname.c b/lib/tempname.c
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+++ b/lib/tempname.c
@@ -0,0 +1,345 @@
+/* Copyright (C) 1991-2022 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library 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.
+
+ The GNU C Library 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 the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#if !_LIBC
+# include <libc-config.h>
+# 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
+#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 <stdalign.h>
+#include <stdint.h>
+#include <sys/random.h>
+#include <sys/stat.h>
+#include <time.h>
+
+#if _LIBC
+# define struct_stat64 struct stat64
+# 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(file, buf) lstat (file, buf)
+# define __stat64(file, buf) stat (file, buf)
+# define __getrandom getrandom
+# define __clock_gettime64 clock_gettime
+# define __timespec64 timespec
+#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)
+
+static random_value
+random_bits (random_value var, bool use_getrandom)
+{
+ 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. */
+ 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. */
+static int
+direxists (const char *dir)
+{
+ struct_stat64 buf;
+ return __stat64 (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 */
+
+#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, _GL_UNUSED void *flags)
+{
+ return __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
+}
+
+static int
+try_nocreate (char *tmpl, _GL_UNUSED void *flags)
+{
+ 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 at least X_SUFFIX_LEN "X"s,
+ possibly with a suffix).
+ The name constructed does not exist at the time of the call to
+ 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.
+
+ We use a clever algorithm to get hard-to-predict names. */
+#ifdef _LIBC
+static
+#endif
+int
+gen_tempname_len (char *tmpl, int suffixlen, int flags, int kind,
+ size_t x_suffix_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;
+
+ /* 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.
+ 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
+ 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
+
+ /* 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;
+
+ /* 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
+ = RANDOM_VALUE_MAX - RANDOM_VALUE_MAX % BASE_62_POWER;
+
+ len = strlen (tmpl);
+ 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 - x_suffix_len - suffixlen];
+
+ for (count = 0; count < attempts; ++count)
+ {
+ for (size_t i = 0; i < x_suffix_len; i++)
+ {
+ if (vdigits == 0)
+ {
+ do
+ {
+ v = random_bits (v, use_getrandom);
+ use_getrandom = true;
+ }
+ while (unfair_min <= v);
+
+ vdigits = BASE_62_DIGITS;
+ }
+
+ XXXXXX[i] = letters[v % 62];
+ v /= 62;
+ vdigits--;
+ }
+
+ 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;
+}
+
+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