1 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
2 // See https://llvm.org/LICENSE.txt for license information.
3 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
4
5 // This is a fuzz target for running out-of-process fuzzing for a
6 // binary specified via environment variable LIBFUZZER_OOP_TARGET.
7 // libFuzzer is not designed for out-of-process fuzzing and so this
8 // ad-hoc rig lacks many of the in-process libFuzzer features, and is slow,
9 // but it does provide the basic functionality, which is to run the target
10 // many times in parallel, feeding in the mutants, and expanding the corpus.
11 // Use this only for very slow targets (slower than ~ 10 exec/s)
12 // that you can't convert to conventional libFuzzer fuzz targets.
13 //
14 // The target binary (which could be a shell script, or anything),
15 // consumes one file as an input and produces the file with coverage counters
16 // as the output (output path is passed via SANCOV_OUT).
17 // One way to produce a valid binary target is to build it with
18 // -fsanitize-coverage=inline-8bit-counters and link it with SanCovDump.cpp,
19 // found in the same directory.
20 //
21 // Example usage:
22 /*
23 clang -fsanitize=fuzzer OutOfProcessFuzzTarget.cpp -o oop-fuzz &&
24 clang -c -fsanitize-coverage=inline-8bit-counters SimpleTest.cpp &&
25 clang -c ../../lib/fuzzer/standalone/StandaloneFuzzTargetMain.c &&
26 clang -c SanCovDump.cpp &&
27 clang++ SanCovDump.o SimpleTest.o StandaloneFuzzTargetMain.o -o oop-target &&
28 rm -rf CORPUS && mkdir CORPUS && echo > CORPUS/seed &&
29 LIBFUZZER_OOP_TARGET="./oop-target > /dev/null 2>&1 " ./oop-fuzz CORPUS -jobs=42
30
31 */
32 #include <fcntl.h>
33 #include <stdint.h>
34 #include <stdio.h>
35 #include <sys/stat.h>
36 #include <sys/types.h>
37 #include <unistd.h>
38
39 #include <string>
40
41 // An arbitrary large number.
42 // If your target is so large that it has more than this number of coverage
43 // edges, you may want to increase this number to match your binary,
44 // otherwise part of the coverage will be lost.
45 // For small targets there is no reason to reduce this number.
46 static const size_t kCountersSize = 1 << 20;
47
48 __attribute__((section(
49 "__libfuzzer_extra_counters"))) static uint8_t Counters[kCountersSize];
50
51 static std::string *Run, *IN, *COV;
52
TearDown()53 void TearDown() {
54 unlink(COV->c_str());
55 unlink(IN->c_str());
56 }
57
Initialize()58 bool Initialize() {
59 IN = new std::string("lf-oop-in-" + std::to_string(getpid()));
60 COV = new std::string("lf-oop-cov-" + std::to_string(getpid()));
61 const char *TargetEnv = getenv("LIBFUZZER_OOP_TARGET");
62 if (!TargetEnv) {
63 fprintf(stderr, "Please define LIBFUZZER_OOP_TARGET\n");
64 exit(1);
65 }
66 Run = new std::string("SANCOV_OUT=" + *COV + " " + TargetEnv + " " + *IN);
67 fprintf(stderr, "libFuzzer: OOP command: %s\n", Run->c_str());
68 atexit(TearDown);
69 return true;
70 }
71
LLVMFuzzerTestOneInput(const uint8_t * data,size_t size)72 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
73 static bool Inited = Initialize();
74 if (size == 0)
75 return 0;
76 if (FILE *f = fopen(IN->c_str(), "w")) {
77 fwrite(data, 1, size, f);
78 fclose(f);
79 }
80 system(Run->c_str());
81 if (FILE *f = fopen(COV->c_str(), "r")) {
82 fread(Counters, 1, kCountersSize, f);
83 fclose(f);
84 }
85 return 0;
86 }
87