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/*
american fuzzy lop++ - afl-proxy skeleton example
---------------------------------------------------
Written by Marc Heuse <mh@mh-sec.de>
Copyright 2019-2024 AFLplusplus Project. 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
HOW-TO
======
You only need to change the while() loop of the main() to send the
data of buf[] with length len to the target and write the coverage
information to __afl_area_ptr[__afl_map_size]
*/
#ifdef __ANDROID__
#include "android-ashmem.h"
#endif
#include "config.h"
#include "types.h"
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>
#include <stdint.h>
#include <errno.h>
#include <sys/mman.h>
#include <sys/shm.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <fcntl.h>
u8 *__afl_area_ptr;
#ifdef __ANDROID__
u32 __afl_map_size = MAP_SIZE;
#else
__thread u32 __afl_map_size = MAP_SIZE;
#endif
/* Error reporting to forkserver controller */
void send_forkserver_error(int error) {
u32 status;
if (!error || error > 0xffff) return;
status = (FS_OPT_ERROR | FS_OPT_SET_ERROR(error));
if (write(FORKSRV_FD + 1, (char *)&status, 4) != 4) return;
}
/* SHM setup. */
static void __afl_map_shm(void) {
char *id_str = getenv(SHM_ENV_VAR);
char *ptr;
/* NOTE TODO BUG FIXME: if you want to supply a variable sized map then
uncomment the following: */
/*
if ((ptr = getenv("AFL_MAP_SIZE")) != NULL) {
u32 val = atoi(ptr);
if (val > 0) __afl_map_size = val;
}
*/
if (__afl_map_size > MAP_SIZE) {
if (__afl_map_size > FS_OPT_MAX_MAPSIZE) {
fprintf(stderr,
"Error: AFL++ tools *require* to set AFL_MAP_SIZE to %u to "
"be able to run this instrumented program!\n",
__afl_map_size);
if (id_str) {
send_forkserver_error(FS_ERROR_MAP_SIZE);
exit(-1);
}
} else {
fprintf(stderr,
"Warning: AFL++ tools will need to set AFL_MAP_SIZE to %u to "
"be able to run this instrumented program!\n",
__afl_map_size);
}
}
if (id_str) {
#ifdef USEMMAP
const char *shm_file_path = id_str;
int shm_fd = -1;
unsigned char *shm_base = NULL;
/* create the shared memory segment as if it was a file */
shm_fd = shm_open(shm_file_path, O_RDWR, 0600);
if (shm_fd == -1) {
fprintf(stderr, "shm_open() failed\n");
send_forkserver_error(FS_ERROR_SHM_OPEN);
exit(1);
}
/* map the shared memory segment to the address space of the process */
shm_base =
mmap(0, __afl_map_size, PROT_READ | PROT_WRITE, MAP_SHARED, shm_fd, 0);
if (shm_base == MAP_FAILED) {
close(shm_fd);
shm_fd = -1;
fprintf(stderr, "mmap() failed\n");
send_forkserver_error(FS_ERROR_MMAP);
exit(2);
}
__afl_area_ptr = shm_base;
#else
u32 shm_id = atoi(id_str);
__afl_area_ptr = shmat(shm_id, 0, 0);
#endif
if (__afl_area_ptr == (void *)-1) {
send_forkserver_error(FS_ERROR_SHMAT);
exit(1);
}
/* Write something into the bitmap so that the parent doesn't give up */
__afl_area_ptr[0] = 1;
}
}
/* Fork server logic. */
static void __afl_start_forkserver(void) {
u8 tmp[4] = {0, 0, 0, 0};
u32 status = 0;
if (__afl_map_size <= FS_OPT_MAX_MAPSIZE)
status |= (FS_OPT_SET_MAPSIZE(__afl_map_size) | FS_OPT_MAPSIZE);
if (status) status |= (FS_OPT_ENABLED);
memcpy(tmp, &status, 4);
/* Phone home and tell the parent that we're OK. */
if (write(FORKSRV_FD + 1, tmp, 4) != 4) return;
}
static u32 __afl_next_testcase(u8 *buf, u32 max_len) {
s32 status, res = 0xffffff;
/* Wait for parent by reading from the pipe. Abort if read fails. */
if (read(FORKSRV_FD, &status, 4) != 4) return 0;
/* we have a testcase - read it */
status = read(0, buf, max_len);
/* report that we are starting the target */
if (write(FORKSRV_FD + 1, &res, 4) != 4) return 0;
return status;
}
static void __afl_end_testcase(void) {
int status = 0xffffff;
if (write(FORKSRV_FD + 1, &status, 4) != 4) exit(1);
}
/* you just need to modify the while() loop in this main() */
int main(int argc, char *argv[]) {
/* This is were the testcase data is written into */
u8 buf[1024]; // this is the maximum size for a test case! set it!
s32 len;
/* here you specify the map size you need that you are reporting to
afl-fuzz. Any value is fine as long as it can be divided by 32. */
__afl_map_size = MAP_SIZE; // default is 65536
/* then we initialize the shared memory map and start the forkserver */
__afl_map_shm();
__afl_start_forkserver();
while ((len = __afl_next_testcase(buf, sizeof(buf))) > 0) {
if (len > 4) { // the minimum data size you need for the target
/* here you have to create the magic that feeds the buf/len to the
target and write the coverage to __afl_area_ptr */
// ... the magic ...
// remove this, this is just to make afl-fuzz not complain when run
if (buf[0] == 0xff)
__afl_area_ptr[1] = 1;
else
__afl_area_ptr[2] = 2;
}
/* report the test case is done and wait for the next */
__afl_end_testcase();
}
return 0;
}
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