persistent_demo.c

/*
   american fuzzy lop++ - persistent mode example
   --------------------------------------------

   Originally written by Michal Zalewski

   Copyright 2015 Google Inc. All rights reserved.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at:

     http://www.apache.org/licenses/LICENSE-2.0

   This file demonstrates the high-performance "persistent mode" that may be
   suitable for fuzzing certain fast and well-behaved libraries, provided that
   they are stateless or that their internal state can be easily reset
   across runs.

   To make this work, the library and this shim need to be compiled in LLVM
   mode using afl-clang-fast (other compiler wrappers will *not* work).

 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
#include <limits.h>

/* Main entry point. */

/* To ensure checks are not optimized out it is recommended to disable
   code optimization for the fuzzer harness main() */
#pragma clang optimize off
#pragma GCC            optimize("O0")

int main(int argc, char **argv) {

  ssize_t len;                               /* how much input did we read? */
  char buf[100]; /* Example-only buffer, you'd replace it with other global or
                    local variables appropriate for your use case. */

  /* The number passed to __AFL_LOOP() controls the maximum number of
     iterations before the loop exits and the program is allowed to
     terminate normally. This limits the impact of accidental memory leaks
     and similar hiccups. */

  __AFL_INIT();
  while (__AFL_LOOP(UINT_MAX)) {

    /*** PLACEHOLDER CODE ***/

    /* STEP 1: Fully re-initialize all critical variables. In our example, this
               involves zeroing buf[], our input buffer. */

    memset(buf, 0, 100);

    /* STEP 2: Read input data. When reading from stdin, no special preparation
               is required. When reading from a named file, you need to close
               the old descriptor and reopen the file first!

               Beware of reading from buffered FILE* objects such as stdin. Use
               raw file descriptors or call fopen() / fdopen() in every pass. */

    len = read(0, buf, 100);

    /* STEP 3: This is where we'd call the tested library on the read data.
               We just have some trivial inline code that faults on 'foo!'. */

    /* do we have enough data? */
    if (len < 8) continue;

    if (buf[0] == 'f') {

      printf("one\n");
      if (buf[1] == 'o') {

        printf("two\n");
        if (buf[2] == 'o') {

          printf("three\n");
          if (buf[3] == '!') {

            printf("four\n");
            if (buf[4] == '!') {

              printf("five\n");
              if (buf[5] == '!') {

                printf("six\n");
                abort();

              }

            }

          }

        }

      }

    }

    /*** END PLACEHOLDER CODE ***/

  }

  /* Once the loop is exited, terminate normally - AFL will restart the process
     when this happens, with a clean slate when it comes to allocated memory,
     leftover file descriptors, etc. */

  return 0;

}