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Unified Diff: third_party/afl/src/experimental/post_library/post_library_png.so.c

Issue 2075883002: Add American Fuzzy Lop (afl) to third_party/afl/ (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: Fix nits Created 4 years, 6 months ago
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Index: third_party/afl/src/experimental/post_library/post_library_png.so.c
diff --git a/third_party/afl/src/experimental/post_library/post_library_png.so.c b/third_party/afl/src/experimental/post_library/post_library_png.so.c
new file mode 100644
index 0000000000000000000000000000000000000000..080a6938ac814653e4cbd9c7a15de353454c9f20
--- /dev/null
+++ b/third_party/afl/src/experimental/post_library/post_library_png.so.c
@@ -0,0 +1,113 @@
+/*
+ american fuzzy lop - postprocessor for PNG
+ ------------------------------------------
+
+ Written and maintained by Michal Zalewski <lcamtuf@google.com>
+
+ 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
+
+ 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;
+
+}
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