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// SPDX-License-Identifier: GPL-2.0
/*
* Generates files or directories with hash collisions on a XFS filesystem
* Copyright (C) 2014 Hannes Frederic Sowa
*/
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
static enum {
ILLEGAL,
DIRECTORY,
FILENAME,
} touch_mode = ILLEGAL;
static bool one_hash = false;
static uint32_t rol32(uint32_t word, unsigned int shift)
{
return (word << shift) | (word >> (32 - shift));
}
static uint32_t xfs_da_hashname(const uint8_t *name, int namelen)
{
uint32_t hash;
for (hash = 0; namelen >= 4; namelen -= 4, name += 4)
hash = (name[0] << 21) ^ (name[1] << 14) ^ (name[2] << 7) ^
(name[3] << 0) ^ rol32(hash, 7 * 4);
if (namelen) {
fprintf(stderr,
"internal error: "
"misbalanced input buffer to xfs_da_hashname - "
"overlapping %d bytes\n", namelen);
exit(1);
}
return hash;
}
static uint8_t gen_rand(void)
{
uint8_t r;
while (!(r = rand()));
return r;
}
static uint8_t buffer[252+1] = {0};
static void gen_name(void)
{
int idx;
uint32_t hash, last;
again:
for (idx = 0; idx < 252-4; idx+=4) {
buffer[idx + 0] = gen_rand();
buffer[idx + 1] = gen_rand();
buffer[idx + 2] = gen_rand();
buffer[idx + 3] = gen_rand();
}
hash = rol32(xfs_da_hashname(buffer, 248), 7 * 4);
last = hash ^ ~0U;
if (last == 0)
goto again;
buffer[idx + 3] = last & 0x7fU;
buffer[idx + 2] = (last >> 7) & 0x7fU;
buffer[idx + 1] = (last >> 14) & 0x7fU;
buffer[idx + 0] = ((last >> 21) & 0xffU);
if (memchr(buffer, '.', sizeof(buffer)) ||
memchr(buffer, '/', sizeof(buffer)))
goto again;
if (one_hash) {
/* very poor - can be improved later */
static bool done = false;
static uint32_t filter;
if (!done) {
filter = xfs_da_hashname(buffer, 252);
done = true;
return;
}
if (filter != xfs_da_hashname(buffer, 252))
goto again;
}
}
static int touch(const char *buffer)
{
if (touch_mode == DIRECTORY) {
if (mkdir(buffer, S_IRWXU)) {
/* ignore if directory is already present */
if (errno == EEXIST)
return 0;
perror("mkdir with random directory name");
return 1;
}
} else if (touch_mode == FILENAME) {
int fd = creat(buffer, S_IRWXU);
if (fd == -1) {
/* ignore duplicate files */
if (errno == EEXIST)
return 0;
perror("creat with random directory name");
return 1;
}
if (close(fd)) {
perror("close is leaking a file descriptor");
return 1;
}
return 0;
}
return 0;
}
static void do_seed(void)
{
struct timeval tv;
if (gettimeofday(&tv, NULL)) {
perror("gettimeofday");
exit(1);
}
srand(tv.tv_sec ^ tv.tv_usec ^ getpid());
}
static void usage_and_exit(const char *pname)
{
fprintf(stderr, "usage: %s [-d] [-f] [-n num] [-s] directory\n"
"\t-f\tcreate files (the default)\n"
"\t-d\tcreate directories\n"
"\t-n num\tcreate num directories or files (default 200000)\n"
"\t-s\tonly generate one hash\n"
"\tdirectory\tthe directory to chdir() to\n",
pname);
exit(1);
}
int main(int argc, char **argv)
{
const char allopts[] = "hsdfn:";
int c, orig_cycles, errors = 0, cycles = 200000;
while ((c = getopt(argc, argv, allopts)) != -1) {
switch (c) {
case 'd':
if (touch_mode != ILLEGAL)
usage_and_exit(argv[0]);
touch_mode = DIRECTORY;
break;
case 'f':
if (touch_mode != ILLEGAL)
usage_and_exit(argv[0]);
touch_mode = FILENAME;
break;
case 'n':
errno = 0;
if (sscanf(optarg, "%d", &cycles) != 1 ||
errno == ERANGE) {
fputs("could not parse number of iterations", stderr);
exit(1);
}
break;
case 's':
one_hash = true;
break;
default:
usage_and_exit(argv[0]);
break;
}
}
if (argc <= optind || touch_mode == ILLEGAL)
usage_and_exit(argv[0]);
if (chdir(argv[optind])) {
perror("chdir");
exit(1);
}
orig_cycles = cycles;
do_seed();
while (cycles--) {
gen_name();
errors += touch((char *)buffer);
}
if (errors)
fprintf(stderr, "creating %d %s caused %d errors\n",
orig_cycles, touch_mode == FILENAME ? "files" : "directories",
errors);
return 0;
}
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