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/*
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Copyright 2015 Google LLC All rights reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at:
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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/*
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american fuzzy lop - LLVM-mode wrapper for clang
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------------------------------------------------
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Written by Laszlo Szekeres <lszekeres@google.com> and
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Michal Zalewski <lcamtuf@google.com>
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LLVM integration design comes from Laszlo Szekeres.
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This program is a drop-in replacement for clang, similar in most respects
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to ../afl-gcc. It tries to figure out compilation mode, adds a bunch
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of flags, and then calls the real compiler.
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*/
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#define AFL_MAIN
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#include "../config.h"
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#include "../types.h"
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#include "../debug.h"
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#include "../alloc-inl.h"
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#include <stdio.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <string.h>
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static u8* obj_path; /* Path to runtime libraries */
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static u8** cc_params; /* Parameters passed to the real CC */
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static u32 cc_par_cnt = 1; /* Param count, including argv0 */
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/* Try to find the runtime libraries. If that fails, abort. */
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static void find_obj(u8* argv0) {
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u8 *afl_path = getenv("AFL_PATH");
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u8 *slash, *tmp;
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if (afl_path) {
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tmp = alloc_printf("%s/afl-llvm-rt.o", afl_path);
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if (!access(tmp, R_OK)) {
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obj_path = afl_path;
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ck_free(tmp);
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return;
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}
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ck_free(tmp);
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}
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slash = strrchr(argv0, '/');
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if (slash) {
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u8 *dir;
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*slash = 0;
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dir = ck_strdup(argv0);
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*slash = '/';
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tmp = alloc_printf("%s/afl-llvm-rt.o", dir);
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if (!access(tmp, R_OK)) {
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obj_path = dir;
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ck_free(tmp);
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return;
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}
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ck_free(tmp);
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ck_free(dir);
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}
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if (!access(AFL_PATH "/afl-llvm-rt.o", R_OK)) {
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obj_path = AFL_PATH;
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return;
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}
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FATAL("Unable to find 'afl-llvm-rt.o' or 'afl-llvm-pass.so'. Please set AFL_PATH");
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}
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/* Copy argv to cc_params, making the necessary edits. */
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static void edit_params(u32 argc, char** argv) {
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u8 fortify_set = 0, asan_set = 0, x_set = 0, bit_mode = 0;
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u8 *name;
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cc_params = ck_alloc((argc + 128) * sizeof(u8*));
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name = strrchr(argv[0], '/');
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if (!name) name = argv[0]; else name++;
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if (!strcmp(name, "afl-clang-fast++")) {
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u8* alt_cxx = getenv("AFL_CXX");
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cc_params[0] = alt_cxx ? alt_cxx : (u8*)"clang++";
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} else {
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u8* alt_cc = getenv("AFL_CC");
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cc_params[0] = alt_cc ? alt_cc : (u8*)"clang";
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}
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/* There are two ways to compile afl-clang-fast. In the traditional mode, we
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use afl-llvm-pass.so to inject instrumentation. In the experimental
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'trace-pc-guard' mode, we use native LLVM instrumentation callbacks
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instead. The latter is a very recent addition - see:
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http://clang.llvm.org/docs/SanitizerCoverage.html#tracing-pcs-with-guards */
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#ifdef USE_TRACE_PC
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cc_params[cc_par_cnt++] = "-fsanitize-coverage=trace-pc-guard";
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#ifndef __ANDROID__
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cc_params[cc_par_cnt++] = "-mllvm";
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cc_params[cc_par_cnt++] = "-sanitizer-coverage-block-threshold=0";
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#endif
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#else
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cc_params[cc_par_cnt++] = "-Xclang";
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cc_params[cc_par_cnt++] = "-load";
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cc_params[cc_par_cnt++] = "-Xclang";
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cc_params[cc_par_cnt++] = alloc_printf("%s/afl-llvm-pass.so", obj_path);
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#endif /* ^USE_TRACE_PC */
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cc_params[cc_par_cnt++] = "-Qunused-arguments";
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while (--argc) {
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u8* cur = *(++argv);
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if (!strcmp(cur, "-m32")) bit_mode = 32;
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if (!strcmp(cur, "armv7a-linux-androideabi")) bit_mode = 32;
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if (!strcmp(cur, "-m64")) bit_mode = 64;
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if (!strcmp(cur, "-x")) x_set = 1;
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if (!strcmp(cur, "-fsanitize=address") ||
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!strcmp(cur, "-fsanitize=memory")) asan_set = 1;
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if (strstr(cur, "FORTIFY_SOURCE")) fortify_set = 1;
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if (!strcmp(cur, "-Wl,-z,defs") ||
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!strcmp(cur, "-Wl,--no-undefined")) continue;
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cc_params[cc_par_cnt++] = cur;
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}
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if (getenv("AFL_HARDEN")) {
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cc_params[cc_par_cnt++] = "-fstack-protector-all";
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if (!fortify_set)
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cc_params[cc_par_cnt++] = "-D_FORTIFY_SOURCE=2";
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}
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if (!asan_set) {
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if (getenv("AFL_USE_ASAN")) {
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if (getenv("AFL_USE_MSAN"))
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FATAL("ASAN and MSAN are mutually exclusive");
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if (getenv("AFL_HARDEN"))
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FATAL("ASAN and AFL_HARDEN are mutually exclusive");
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cc_params[cc_par_cnt++] = "-U_FORTIFY_SOURCE";
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cc_params[cc_par_cnt++] = "-fsanitize=address";
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} else if (getenv("AFL_USE_MSAN")) {
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if (getenv("AFL_USE_ASAN"))
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FATAL("ASAN and MSAN are mutually exclusive");
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if (getenv("AFL_HARDEN"))
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FATAL("MSAN and AFL_HARDEN are mutually exclusive");
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cc_params[cc_par_cnt++] = "-U_FORTIFY_SOURCE";
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cc_params[cc_par_cnt++] = "-fsanitize=memory";
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}
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}
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#ifdef USE_TRACE_PC
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if (getenv("AFL_INST_RATIO"))
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FATAL("AFL_INST_RATIO not available at compile time with 'trace-pc'.");
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#endif /* USE_TRACE_PC */
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if (!getenv("AFL_DONT_OPTIMIZE")) {
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cc_params[cc_par_cnt++] = "-g";
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cc_params[cc_par_cnt++] = "-O3";
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cc_params[cc_par_cnt++] = "-funroll-loops";
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}
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if (getenv("AFL_NO_BUILTIN")) {
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cc_params[cc_par_cnt++] = "-fno-builtin-strcmp";
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cc_params[cc_par_cnt++] = "-fno-builtin-strncmp";
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cc_params[cc_par_cnt++] = "-fno-builtin-strcasecmp";
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cc_params[cc_par_cnt++] = "-fno-builtin-strncasecmp";
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cc_params[cc_par_cnt++] = "-fno-builtin-memcmp";
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}
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cc_params[cc_par_cnt++] = "-D__AFL_HAVE_MANUAL_CONTROL=1";
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cc_params[cc_par_cnt++] = "-D__AFL_COMPILER=1";
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cc_params[cc_par_cnt++] = "-DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION=1";
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/* When the user tries to use persistent or deferred forkserver modes by
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appending a single line to the program, we want to reliably inject a
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signature into the binary (to be picked up by afl-fuzz) and we want
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to call a function from the runtime .o file. This is unnecessarily
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painful for three reasons:
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1) We need to convince the compiler not to optimize out the signature.
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This is done with __attribute__((used)).
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2) We need to convince the linker, when called with -Wl,--gc-sections,
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not to do the same. This is done by forcing an assignment to a
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'volatile' pointer.
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3) We need to declare __afl_persistent_loop() in the global namespace,
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but doing this within a method in a class is hard - :: and extern "C"
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are forbidden and __attribute__((alias(...))) doesn't work. Hence the
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__asm__ aliasing trick.
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*/
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cc_params[cc_par_cnt++] = "-D__AFL_LOOP(_A)="
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"({ static volatile char *_B __attribute__((used)); "
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" _B = (char*)\"" PERSIST_SIG "\"; "
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#ifdef __APPLE__
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"__attribute__((visibility(\"default\"))) "
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"int _L(unsigned int) __asm__(\"___afl_persistent_loop\"); "
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#else
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"__attribute__((visibility(\"default\"))) "
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"int _L(unsigned int) __asm__(\"__afl_persistent_loop\"); "
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#endif /* ^__APPLE__ */
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"_L(_A); })";
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cc_params[cc_par_cnt++] = "-D__AFL_INIT()="
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"do { static volatile char *_A __attribute__((used)); "
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" _A = (char*)\"" DEFER_SIG "\"; "
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#ifdef __APPLE__
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"__attribute__((visibility(\"default\"))) "
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"void _I(void) __asm__(\"___afl_manual_init\"); "
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#else
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"__attribute__((visibility(\"default\"))) "
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"void _I(void) __asm__(\"__afl_manual_init\"); "
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#endif /* ^__APPLE__ */
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"_I(); } while (0)";
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if (x_set) {
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cc_params[cc_par_cnt++] = "-x";
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cc_params[cc_par_cnt++] = "none";
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}
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#ifndef __ANDROID__
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switch (bit_mode) {
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case 0:
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cc_params[cc_par_cnt++] = alloc_printf("%s/afl-llvm-rt.o", obj_path);
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break;
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case 32:
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cc_params[cc_par_cnt++] = alloc_printf("%s/afl-llvm-rt-32.o", obj_path);
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if (access(cc_params[cc_par_cnt - 1], R_OK))
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FATAL("-m32 is not supported by your compiler");
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break;
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case 64:
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cc_params[cc_par_cnt++] = alloc_printf("%s/afl-llvm-rt-64.o", obj_path);
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if (access(cc_params[cc_par_cnt - 1], R_OK))
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FATAL("-m64 is not supported by your compiler");
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break;
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}
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#endif
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cc_params[cc_par_cnt] = NULL;
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}
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/* Main entry point */
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int main(int argc, char** argv) {
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if (isatty(2) && !getenv("AFL_QUIET")) {
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#ifdef USE_TRACE_PC
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SAYF(cCYA "afl-clang-fast [tpcg] " cBRI VERSION cRST " by <lszekeres@google.com>\n");
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#else
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SAYF(cCYA "afl-clang-fast " cBRI VERSION cRST " by <lszekeres@google.com>\n");
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#endif /* ^USE_TRACE_PC */
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}
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if (argc < 2) {
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SAYF("\n"
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"This is a helper application for afl-fuzz. It serves as a drop-in replacement\n"
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"for clang, letting you recompile third-party code with the required runtime\n"
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"instrumentation. A common use pattern would be one of the following:\n\n"
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" CC=%s/afl-clang-fast ./configure\n"
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" CXX=%s/afl-clang-fast++ ./configure\n\n"
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"In contrast to the traditional afl-clang tool, this version is implemented as\n"
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"an LLVM pass and tends to offer improved performance with slow programs.\n\n"
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"You can specify custom next-stage toolchain via AFL_CC and AFL_CXX. Setting\n"
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"AFL_HARDEN enables hardening optimizations in the compiled code.\n\n",
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BIN_PATH, BIN_PATH);
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exit(1);
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}
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#ifndef __ANDROID__
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find_obj(argv[0]);
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#endif
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edit_params(argc, argv);
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execvp(cc_params[0], (char**)cc_params);
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FATAL("Oops, failed to execute '%s' - check your PATH", cc_params[0]);
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return 0;
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}
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Loading…
Reference in new issue