/* Copyright 2013 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 - wrapper for GCC and clang ---------------------------------------------- Written and maintained by Michal Zalewski This program is a drop-in replacement for GCC or clang. The most common way of using it is to pass the path to afl-gcc or afl-clang via CC when invoking ./configure. (Of course, use CXX and point it to afl-g++ / afl-clang++ for C++ code.) The wrapper needs to know the path to afl-as (renamed to 'as'). The default is /usr/local/lib/afl/. A convenient way to specify alternative directories would be to set AFL_PATH. If AFL_HARDEN is set, the wrapper will compile the target app with various hardening options that may help detect memory management issues more reliably. You can also specify AFL_USE_ASAN to enable ASAN. If you want to call a non-default compiler as a next step of the chain, specify its location via AFL_CC or AFL_CXX. */ #define AFL_MAIN #include "config.h" #include "types.h" #include "debug.h" #include "alloc-inl.h" #include #include #include #include static u8* as_path; /* Path to the AFL 'as' wrapper */ static u8** cc_params; /* Parameters passed to the real CC */ static u32 cc_par_cnt = 1; /* Param count, including argv0 */ static u8 be_quiet, /* Quiet mode */ clang_mode; /* Invoked as afl-clang*? */ /* Try to find our "fake" GNU assembler in AFL_PATH or at the location derived from argv[0]. If that fails, abort. */ static void find_as(u8* argv0) { u8 *afl_path = getenv("AFL_PATH"); u8 *slash, *tmp; if (afl_path) { tmp = alloc_printf("%s/as", afl_path); if (!access(tmp, X_OK)) { as_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-as", dir); if (!access(tmp, X_OK)) { as_path = dir; ck_free(tmp); return; } ck_free(tmp); ck_free(dir); } if (!access(AFL_PATH "/as", X_OK)) { as_path = AFL_PATH; return; } FATAL("Unable to find AFL wrapper binary for 'as'. 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; u8 *name; #if defined(__FreeBSD__) && defined(__x86_64__) u8 m32_set = 0; #endif cc_params = ck_alloc((argc + 128) * sizeof(u8*)); name = strrchr(argv[0], '/'); if (!name) name = argv[0]; else name++; if (!strncmp(name, "afl-clang", 9)) { clang_mode = 1; setenv(CLANG_ENV_VAR, "1", 1); if (!strcmp(name, "afl-clang++")) { 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"; } } else { /* With GCJ and Eclipse installed, you can actually compile Java! The instrumentation will work (amazingly). Alas, unhandled exceptions do not call abort(), so afl-fuzz would need to be modified to equate non-zero exit codes with crash conditions when working with Java binaries. Meh. */ #ifdef __APPLE__ if (!strcmp(name, "afl-g++")) cc_params[0] = getenv("AFL_CXX"); else if (!strcmp(name, "afl-gcj")) cc_params[0] = getenv("AFL_GCJ"); else cc_params[0] = getenv("AFL_CC"); if (!cc_params[0]) { SAYF("\n" cLRD "[-] " cRST "On Apple systems, 'gcc' is usually just a wrapper for clang. Please use the\n" " 'afl-clang' utility instead of 'afl-gcc'. If you really have GCC installed,\n" " set AFL_CC or AFL_CXX to specify the correct path to that compiler.\n"); FATAL("AFL_CC or AFL_CXX required on MacOS X"); } #else if (!strcmp(name, "afl-g++")) { u8* alt_cxx = getenv("AFL_CXX"); cc_params[0] = alt_cxx ? alt_cxx : (u8*)"g++"; } else if (!strcmp(name, "afl-gcj")) { u8* alt_cc = getenv("AFL_GCJ"); cc_params[0] = alt_cc ? alt_cc : (u8*)"gcj"; } else { u8* alt_cc = getenv("AFL_CC"); cc_params[0] = alt_cc ? alt_cc : (u8*)"gcc"; } #endif /* __APPLE__ */ } while (--argc) { u8* cur = *(++argv); if (!strncmp(cur, "-B", 2)) { if (!be_quiet) WARNF("-B is already set, overriding"); if (!cur[2] && argc > 1) { argc--; argv++; } continue; } if (!strcmp(cur, "-integrated-as")) continue; if (!strcmp(cur, "-pipe")) continue; #if defined(__FreeBSD__) && defined(__x86_64__) if (!strcmp(cur, "-m32")) m32_set = 1; #endif if (!strcmp(cur, "-fsanitize=address") || !strcmp(cur, "-fsanitize=memory")) asan_set = 1; if (strstr(cur, "FORTIFY_SOURCE")) fortify_set = 1; cc_params[cc_par_cnt++] = cur; } cc_params[cc_par_cnt++] = "-B"; cc_params[cc_par_cnt++] = as_path; if (clang_mode) cc_params[cc_par_cnt++] = "-no-integrated-as"; 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) { /* Pass this on to afl-as to adjust map density. */ setenv("AFL_USE_ASAN", "1", 1); } else 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"; } if (!getenv("AFL_DONT_OPTIMIZE")) { #if defined(__FreeBSD__) && defined(__x86_64__) /* On 64-bit FreeBSD systems, clang -g -m32 is broken, but -m32 itself works OK. This has nothing to do with us, but let's avoid triggering that bug. */ if (!clang_mode || !m32_set) cc_params[cc_par_cnt++] = "-g"; #else cc_params[cc_par_cnt++] = "-g"; #endif cc_params[cc_par_cnt++] = "-O3"; cc_params[cc_par_cnt++] = "-funroll-loops"; /* Two indicators that you're building for fuzzing; one of them is AFL-specific, the other is shared with libfuzzer. */ cc_params[cc_par_cnt++] = "-D__AFL_COMPILER=1"; cc_params[cc_par_cnt++] = "-DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION=1"; } 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++] = "-fno-builtin-strstr"; cc_params[cc_par_cnt++] = "-fno-builtin-strcasestr"; } cc_params[cc_par_cnt] = NULL; } /* Main entry point */ int main(int argc, char** argv) { if (isatty(2) && !getenv("AFL_QUIET")) { SAYF(cCYA "afl-cc " cBRI VERSION cRST " by \n"); } else be_quiet = 1; if (argc < 2) { SAYF("\n" "This is a helper application for afl-fuzz. It serves as a drop-in replacement\n" "for gcc or clang, letting you recompile third-party code with the required\n" "runtime instrumentation. A common use pattern would be one of the following:\n\n" " CC=%s/afl-gcc ./configure\n" " CXX=%s/afl-g++ ./configure\n\n" "You can specify custom next-stage toolchain via AFL_CC, AFL_CXX, and AFL_AS.\n" "Setting AFL_HARDEN enables hardening optimizations in the compiled code.\n\n", BIN_PATH, BIN_PATH); exit(1); } find_as(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; }