/*
american fuzzy lop - LLVM-mode wrapper for clang
------------------------------------------------
Written by Laszlo Szekeres <[email protected]> and
Michal Zalewski <[email protected]>
LLVM integration design comes from Laszlo Szekeres.
Copyright 2015, 2016 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 program is a drop-in replacement for clang, similar in most respects
to ../afl-gcc. It tries to figure out compilation mode, adds a bunch
of flags, and then calls the real compiler.
*/
#define AFL_MAIN
#include "../config.h"
#include "../types.h"
#include "../debug.h"
#include "../alloc-inl.h"
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
static u8* obj_path; /* Path to runtime libraries */
static u8** cc_params; /* Parameters passed to the real CC */
static u32 cc_par_cnt = 1; /* Param count, including argv0 */
/* Try to find the runtime libraries. If that fails, abort. */
static void find_obj(u8* argv0) {
u8 *afl_path = getenv("AFL_PATH");
u8 *slash, *tmp;
if (afl_path) {
tmp = alloc_printf("%s/afl-llvm-rt.o", afl_path);
if (!access(tmp, R_OK)) {
obj_path = afl_path;
ck_free(tmp);
return;
}
ck_free(tmp);
}
slash = strrchr(argv0, '/');
if (slash) {
u8 *dir;
*slash = 0;
dir = ck_strdup(argv0);
*slash = '/';
tmp = alloc_printf("%s/afl-llvm-rt.o", dir);
if (!access(tmp, R_OK)) {
obj_path = dir;
ck_free(tmp);
return;
}
ck_free(tmp);
ck_free(dir);
}
if (!access(AFL_PATH "/afl-llvm-rt.o", R_OK)) {
obj_path = AFL_PATH;
return;
}
FATAL("Unable to find 'afl-llvm-rt.o' or 'afl-llvm-pass.so'. Please set AFL_PATH");
}
/* Copy argv to cc_params, making the necessary edits. */
static void edit_params(u32 argc, char** argv) {
u8 fortify_set = 0, asan_set = 0, x_set = 0, maybe_linking = 1, bit_mode = 0;
u8 *name;
cc_params = ck_alloc((argc + 128) * sizeof(u8*));
name = strrchr(argv[0], '/');
if (!name) name = argv[0]; else name++;
if (!strcmp(name, "afl-clang-fast++")) {
u8* alt_cxx = getenv("AFL_CXX");
cc_params[0] = alt_cxx ? alt_cxx : (u8*)"clang++";
} else {
u8* alt_cc = getenv("AFL_CC");
cc_params[0] = alt_cc ? alt_cc : (u8*)"clang";
}
/* There are two ways to compile afl-clang-fast. In the traditional mode, we
use afl-llvm-pass.so to inject instrumentation. In the experimental
'trace-pc-guard' mode, we use native LLVM instrumentation callbacks
instead. The latter is a very recent addition - see:
http://clang.llvm.org/docs/SanitizerCoverage.html#tracing-pcs-with-guards */
#ifdef USE_TRACE_PC
cc_params[cc_par_cnt++] = "-fsanitize-coverage=trace-pc-guard";
cc_params[cc_par_cnt++] = "-mllvm";
cc_params[cc_par_cnt++] = "-sanitizer-coverage-block-threshold=0";
#else
cc_params[cc_par_cnt++] = "-Xclang";
cc_params[cc_par_cnt++] = "-load";
cc_params[cc_par_cnt++] = "-Xclang";
cc_params[cc_par_cnt++] = alloc_printf("%s/afl-llvm-pass.so", obj_path);
#endif /* ^USE_TRACE_PC */
cc_params[cc_par_cnt++] = "-Qunused-arguments";
/* Detect stray -v calls from ./configure scripts. */
if (argc == 1 && !strcmp(argv[1], "-v")) maybe_linking = 0;
while (--argc) {
u8* cur = *(++argv);
if (!strcmp(cur, "-m32")) bit_mode = 32;
if (!strcmp(cur, "-m64")) bit_mode = 64;
if (!strcmp(cur, "-x")) x_set = 1;
if (!strcmp(cur, "-c") || !strcmp(cur, "-S") || !strcmp(cur, "-E"))
maybe_linking = 0;
if (!strcmp(cur, "-fsanitize=address") ||
!strcmp(cur, "-fsanitize=memory")) asan_set = 1;
if (strstr(cur, "FORTIFY_SOURCE")) fortify_set = 1;
if (!strcmp(cur, "-shared")) maybe_linking = 0;
if (!strcmp(cur, "-Wl,-z,defs") ||
!strcmp(cur, "-Wl,--no-undefined")) continue;
cc_params[cc_par_cnt++] = cur;
}
if (getenv("AFL_HARDEN")) {
cc_params[cc_par_cnt++] = "-fstack-protector-all";
if (!fortify_set)
cc_params[cc_par_cnt++] = "-D_FORTIFY_SOURCE=2";
}
if (!asan_set) {
if (getenv("AFL_USE_ASAN")) {
if (getenv("AFL_USE_MSAN"))
FATAL("ASAN and MSAN are mutually exclusive");
if (getenv("AFL_HARDEN"))
FATAL("ASAN and AFL_HARDEN are mutually exclusive");
cc_params[cc_par_cnt++] = "-U_FORTIFY_SOURCE";
cc_params[cc_par_cnt++] = "-fsanitize=address";
} else if (getenv("AFL_USE_MSAN")) {
if (getenv("AFL_USE_ASAN"))
FATAL("ASAN and MSAN are mutually exclusive");
if (getenv("AFL_HARDEN"))
FATAL("MSAN and AFL_HARDEN are mutually exclusive");
cc_params[cc_par_cnt++] = "-U_FORTIFY_SOURCE";
cc_params[cc_par_cnt++] = "-fsanitize=memory";
}
}
#ifdef USE_TRACE_PC
if (getenv("AFL_INST_RATIO"))
FATAL("AFL_INST_RATIO not available at compile time with 'trace-pc'.");
#endif /* USE_TRACE_PC */
if (!getenv("AFL_DONT_OPTIMIZE")) {
cc_params[cc_par_cnt++] = "-g";
cc_params[cc_par_cnt++] = "-O3";
cc_params[cc_par_cnt++] = "-funroll-loops";
}
if (getenv("AFL_NO_BUILTIN")) {
cc_params[cc_par_cnt++] = "-fno-builtin-strcmp";
cc_params[cc_par_cnt++] = "-fno-builtin-strncmp";
cc_params[cc_par_cnt++] = "-fno-builtin-strcasecmp";
cc_params[cc_par_cnt++] = "-fno-builtin-strncasecmp";
cc_params[cc_par_cnt++] = "-fno-builtin-memcmp";
}
cc_params[cc_par_cnt++] = "-D__AFL_HAVE_MANUAL_CONTROL=1";
cc_params[cc_par_cnt++] = "-D__AFL_COMPILER=1";
cc_params[cc_par_cnt++] = "-DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION=1";
/* When the user tries to use persistent or deferred forkserver modes by
appending a single line to the program, we want to reliably inject a
signature into the binary (to be picked up by afl-fuzz) and we want
to call a function from the runtime .o file. This is unnecessarily
painful for three reasons:
1) We need to convince the compiler not to optimize out the signature.
This is done with __attribute__((used)).
2) We need to convince the linker, when called with -Wl,--gc-sections,
not to do the same. This is done by forcing an assignment to a
'volatile' pointer.
3) We need to declare __afl_persistent_loop() in the global namespace,
but doing this within a method in a class is hard - :: and extern "C"
are forbidden and __attribute__((alias(...))) doesn't work. Hence the
__asm__ aliasing trick.
*/
cc_params[cc_par_cnt++] = "-D__AFL_LOOP(_A)="
"({ static volatile char *_B __attribute__((used)); "
" _B = (char*)\"" PERSIST_SIG "\"; "
#ifdef __APPLE__
"__attribute__((visibility(\"default\"))) "
"int _L(unsigned int) __asm__(\"___afl_persistent_loop\"); "
#else
"__attribute__((visibility(\"default\"))) "
"int _L(unsigned int) __asm__(\"__afl_persistent_loop\"); "
#endif /* ^__APPLE__ */
"_L(_A); })";
cc_params[cc_par_cnt++] = "-D__AFL_INIT()="
"do { static volatile char *_A __attribute__((used)); "
" _A = (char*)\"" DEFER_SIG "\"; "
#ifdef __APPLE__
"__attribute__((visibility(\"default\"))) "
"void _I(void) __asm__(\"___afl_manual_init\"); "
#else
"__attribute__((visibility(\"default\"))) "
"void _I(void) __asm__(\"__afl_manual_init\"); "
#endif /* ^__APPLE__ */
"_I(); } while (0)";
if (maybe_linking) {
if (x_set) {
cc_params[cc_par_cnt++] = "-x";
cc_params[cc_par_cnt++] = "none";
}
switch (bit_mode) {
case 0:
cc_params[cc_par_cnt++] = alloc_printf("%s/afl-llvm-rt.o", obj_path);
break;
case 32:
cc_params[cc_par_cnt++] = alloc_printf("%s/afl-llvm-rt-32.o", obj_path);
if (access(cc_params[cc_par_cnt - 1], R_OK))
FATAL("-m32 is not supported by your compiler");
break;
case 64:
cc_params[cc_par_cnt++] = alloc_printf("%s/afl-llvm-rt-64.o", obj_path);
if (access(cc_params[cc_par_cnt - 1], R_OK))
FATAL("-m64 is not supported by your compiler");
break;
}
}
cc_params[cc_par_cnt] = NULL;
}
/* Main entry point */
int main(int argc, char** argv) {
if (isatty(2) && !getenv("AFL_QUIET")) {
#ifdef USE_TRACE_PC
SAYF(cCYA "afl-clang-fast [tpcg] " cBRI VERSION cRST " by <[email protected]>\n");
#else
SAYF(cCYA "afl-clang-fast " cBRI VERSION cRST " by <[email protected]>\n");
#endif /* ^USE_TRACE_PC */
}
if (argc < 2) {
SAYF("\n"
"This is a helper application for afl-fuzz. It serves as a drop-in replacement\n"
"for clang, letting you recompile third-party code with the required runtime\n"
"instrumentation. A common use pattern would be one of the following:\n\n"
" CC=%s/afl-clang-fast ./configure\n"
" CXX=%s/afl-clang-fast++ ./configure\n\n"
"In contrast to the traditional afl-clang tool, this version is implemented as\n"
"an LLVM pass and tends to offer improved performance with slow programs.\n\n"
"You can specify custom next-stage toolchain via AFL_CC and AFL_CXX. Setting\n"
"AFL_HARDEN enables hardening optimizations in the compiled code.\n\n",
BIN_PATH, BIN_PATH);
exit(1);
}
find_obj(argv[0]);
edit_params(argc, argv);
execvp(cc_params[0], (char**)cc_params);
FATAL("Oops, failed to execute '%s' - check your PATH", cc_params[0]);
return 0;
}
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