You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
121 lines
3.2 KiB
121 lines
3.2 KiB
1 month ago
|
/*
|
||
|
|
Copyright 2015 Google LLC 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
|
||
|
|
|
||
|
|
Unless required by applicable law or agreed to in writing, software
|
||
|
|
distributed under the License is distributed on an "AS IS" BASIS,
|
||
|
|
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
||
|
|
See the License for the specific language governing permissions and
|
||
|
|
limitations under the License.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/*
|
||
|
|
american fuzzy lop - postprocessor for PNG
|
||
|
|
------------------------------------------
|
||
|
|
|
||
|
|
Written and maintained by Michal Zalewski <lcamtuf@google.com>
|
||
|
|
|
||
|
|
See post_library.so.c for a general discussion of how to implement
|
||
|
|
postprocessors. This specific postprocessor attempts to fix up PNG
|
||
|
|
checksums, providing a slightly more complicated example than found
|
||
|
|
in post_library.so.c.
|
||
|
|
|
||
|
|
Compile with:
|
||
|
|
|
||
|
|
gcc -shared -Wall -O3 post_library_png.so.c -o post_library_png.so -lz
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include <stdio.h>
|
||
|
|
#include <stdlib.h>
|
||
|
|
#include <stdint.h>
|
||
|
|
#include <string.h>
|
||
|
|
#include <zlib.h>
|
||
|
|
|
||
|
|
#include <arpa/inet.h>
|
||
|
|
|
||
|
|
/* A macro to round an integer up to 4 kB. */
|
||
|
|
|
||
|
|
#define UP4K(_i) ((((_i) >> 12) + 1) << 12)
|
||
|
|
|
||
|
|
const unsigned char* afl_postprocess(const unsigned char* in_buf,
|
||
|
|
unsigned int* len) {
|
||
|
|
|
||
|
|
static unsigned char* saved_buf;
|
||
|
|
static unsigned int saved_len;
|
||
|
|
|
||
|
|
unsigned char* new_buf = (unsigned char*)in_buf;
|
||
|
|
unsigned int pos = 8;
|
||
|
|
|
||
|
|
/* Don't do anything if there's not enough room for the PNG header
|
||
|
|
(8 bytes). */
|
||
|
|
|
||
|
|
if (*len < 8) return in_buf;
|
||
|
|
|
||
|
|
/* Minimum size of a zero-length PNG chunk is 12 bytes; if we
|
||
|
|
don't have that, we can bail out. */
|
||
|
|
|
||
|
|
while (pos + 12 <= *len) {
|
||
|
|
|
||
|
|
unsigned int chunk_len, real_cksum, file_cksum;
|
||
|
|
|
||
|
|
/* Chunk length is the first big-endian dword in the chunk. */
|
||
|
|
|
||
|
|
chunk_len = ntohl(*(uint32_t*)(in_buf + pos));
|
||
|
|
|
||
|
|
/* Bail out if chunk size is too big or goes past EOF. */
|
||
|
|
|
||
|
|
if (chunk_len > 1024 * 1024 || pos + 12 + chunk_len > *len) break;
|
||
|
|
|
||
|
|
/* Chunk checksum is calculated for chunk ID (dword) and the actual
|
||
|
|
payload. */
|
||
|
|
|
||
|
|
real_cksum = htonl(crc32(0, in_buf + pos + 4, chunk_len + 4));
|
||
|
|
|
||
|
|
/* The in-file checksum is the last dword past the chunk data. */
|
||
|
|
|
||
|
|
file_cksum = *(uint32_t*)(in_buf + pos + 8 + chunk_len);
|
||
|
|
|
||
|
|
/* If the checksums do not match, we need to fix the file. */
|
||
|
|
|
||
|
|
if (real_cksum != file_cksum) {
|
||
|
|
|
||
|
|
/* First modification? Make a copy of the input buffer. Round size
|
||
|
|
up to 4 kB to minimize the number of reallocs needed. */
|
||
|
|
|
||
|
|
if (new_buf == in_buf) {
|
||
|
|
|
||
|
|
if (*len <= saved_len) {
|
||
|
|
|
||
|
|
new_buf = saved_buf;
|
||
|
|
|
||
|
|
} else {
|
||
|
|
|
||
|
|
new_buf = realloc(saved_buf, UP4K(*len));
|
||
|
|
if (!new_buf) return in_buf;
|
||
|
|
saved_buf = new_buf;
|
||
|
|
saved_len = UP4K(*len);
|
||
|
|
memcpy(new_buf, in_buf, *len);
|
||
|
|
|
||
|
|
}
|
||
|
|
|
||
|
|
}
|
||
|
|
|
||
|
|
*(uint32_t*)(new_buf + pos + 8 + chunk_len) = real_cksum;
|
||
|
|
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Skip the entire chunk and move to the next one. */
|
||
|
|
|
||
|
|
pos += 12 + chunk_len;
|
||
|
|
|
||
|
|
}
|
||
|
|
|
||
|
|
return new_buf;
|
||
|
|
|
||
|
|
}
|