strstr_fuzz.c

gistfile1.txt

#include <assert.h>
#include <dlfcn.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

static char *strstr_simple(const char *haystack, const char *needle) {
  /*
   * This function return a pointer to the beginning of the located substring,
   * or NULL if the substring is not found. If needle is the empty string, the
   * return value is always haystack itself.
   */
  int i, j;

  if (needle == NULL || haystack == NULL) {
    return NULL;
  }
  if (needle[0] == 0) {
    return (char *)haystack;
  }
  for (i = 0; haystack[i] != 0; i++) {
    for (j = 0; haystack[i + j] != 0 && needle[j] != 0; j++) {
      if (needle[j] != haystack[i + j]) {
        break;
      }
    }
    if (needle[j] == 0) {
      return (char *)haystack + i;
    }
  }
  return NULL;
}

static char *(*strstr_ptr)(const char *haystack, const char *needle);

__attribute__((constructor)) static void init(void) {
  void *libc = dlopen("libc.so.6", RTLD_NOW);
  strstr_ptr = dlsym(libc, "strstr");
}

int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len) {
  char *s = malloc(len + 2);
  assert(s);
  memcpy(s, buf, len);
  s[len] = 0;
  s[len + 1] = 0;
  s[len / 2] = 0;
  assert(strstr_simple(s, &s[len / 2 + 1]) == strstr_ptr(s, &s[len / 2 + 1]));
  free(s);
  return 0;
}