1 /*
2 american fuzzy lop - wrapper for GCC and clang
3 ----------------------------------------------
4
5 Written and maintained by Michal Zalewski <lcamtuf@google.com>
6
7 Copyright 2013, 2014, 2015 Google Inc. All rights reserved.
8
9 Licensed under the Apache License, Version 2.0 (the "License");
10 you may not use this file except in compliance with the License.
11 You may obtain a copy of the License at:
12
13 http://www.apache.org/licenses/LICENSE-2.0
14
15 This program is a drop-in replacement for GCC or clang. The most common way
16 of using it is to pass the path to afl-gcc or afl-clang via CC when invoking
17 ./configure.
18
19 (Of course, use CXX and point it to afl-g++ / afl-clang++ for C++ code.)
20
21 The wrapper needs to know the path to afl-as (renamed to 'as'). The default
22 is /usr/local/lib/afl/. A convenient way to specify alternative directories
23 would be to set AFL_PATH.
24
25 If AFL_HARDEN is set, the wrapper will compile the target app with various
26 hardening options that may help detect memory management issues more
27 reliably. You can also specify AFL_USE_ASAN to enable ASAN.
28
29 If you want to call a non-default compiler as a next step of the chain,
30 specify its location via AFL_CC or AFL_CXX.
31
32 */
33
34 #define AFL_MAIN
35
36 #include "config.h"
37 #include "types.h"
38 #include "debug.h"
39 #include "alloc-inl.h"
40
41 #include <stdio.h>
42 #include <unistd.h>
43 #include <stdlib.h>
44 #include <string.h>
45
46 static u8* as_path; /* Path to the AFL 'as' wrapper */
47 static u8** cc_params; /* Parameters passed to the real CC */
48 static u32 cc_par_cnt = 1; /* Param count, including argv0 */
49 static u8 be_quiet, /* Quiet mode */
50 clang_mode; /* Invoked as afl-clang*? */
51
52
53 /* Try to find our "fake" GNU assembler in AFL_PATH or at the location derived
54 from argv[0]. If that fails, abort. */
55
find_as(u8 * argv0)56 static void find_as(u8* argv0) {
57
58 u8 *afl_path = getenv("AFL_PATH");
59 u8 *slash, *tmp;
60
61 if (afl_path) {
62
63 tmp = alloc_printf("%s/as", afl_path);
64
65 if (!access(tmp, X_OK)) {
66 as_path = afl_path;
67 ck_free(tmp);
68 return;
69 }
70
71 ck_free(tmp);
72
73 }
74
75 slash = strrchr(argv0, '/');
76
77 if (slash) {
78
79 u8 *dir;
80
81 *slash = 0;
82 dir = ck_strdup(argv0);
83 *slash = '/';
84
85 tmp = alloc_printf("%s/afl-as", dir);
86
87 if (!access(tmp, X_OK)) {
88 as_path = dir;
89 ck_free(tmp);
90 return;
91 }
92
93 ck_free(tmp);
94 ck_free(dir);
95
96 }
97
98 if (!access(AFL_PATH "/as", X_OK)) {
99 as_path = AFL_PATH;
100 return;
101 }
102
103 FATAL("Unable to find AFL wrapper binary for 'as'. Please set AFL_PATH");
104
105 }
106
107
108 /* Copy argv to cc_params, making the necessary edits. */
109
edit_params(u32 argc,char ** argv)110 static void edit_params(u32 argc, char** argv) {
111
112 u8 fortify_set = 0, asan_set = 0;
113 u8 *name;
114
115 #if defined(__FreeBSD__) && defined(__x86_64__)
116 u8 m32_set = 0;
117 #endif
118
119 cc_params = ck_alloc((argc + 128) * sizeof(u8*));
120
121 name = strrchr(argv[0], '/');
122 if (!name) name = argv[0]; else name++;
123
124 if (!strncmp(name, "afl-clang", 9)) {
125
126 clang_mode = 1;
127
128 setenv(CLANG_ENV_VAR, "1", 1);
129
130 if (!strcmp(name, "afl-clang++")) {
131 u8* alt_cxx = getenv("AFL_CXX");
132 cc_params[0] = alt_cxx ? alt_cxx : (u8*)"clang++";
133 } else {
134 u8* alt_cc = getenv("AFL_CC");
135 cc_params[0] = alt_cc ? alt_cc : (u8*)"clang";
136 }
137
138 } else {
139
140 /* With GCJ and Eclipse installed, you can actually compile Java! The
141 instrumentation will work (amazingly). Alas, unhandled exceptions do
142 not call abort(), so afl-fuzz would need to be modified to equate
143 non-zero exit codes with crash conditions when working with Java
144 binaries. Meh. */
145
146 #ifdef __APPLE__
147
148 if (!strcmp(name, "afl-g++")) cc_params[0] = getenv("AFL_CXX");
149 else if (!strcmp(name, "afl-gcj")) cc_params[0] = getenv("AFL_GCJ");
150 else cc_params[0] = getenv("AFL_CC");
151
152 if (!cc_params[0]) {
153
154 SAYF("\n" cLRD "[-] " cRST
155 "On Apple systems, 'gcc' is usually just a wrapper for clang. Please use the\n"
156 " 'afl-clang' utility instead of 'afl-gcc'. If you really have GCC installed,\n"
157 " set AFL_CC or AFL_CXX to specify the correct path to that compiler.\n");
158
159 FATAL("AFL_CC or AFL_CXX required on MacOS X");
160
161 }
162
163 #else
164
165 if (!strcmp(name, "afl-g++")) {
166 u8* alt_cxx = getenv("AFL_CXX");
167 cc_params[0] = alt_cxx ? alt_cxx : (u8*)"g++";
168 } else if (!strcmp(name, "afl-gcj")) {
169 u8* alt_cc = getenv("AFL_GCJ");
170 cc_params[0] = alt_cc ? alt_cc : (u8*)"gcj";
171 } else {
172 u8* alt_cc = getenv("AFL_CC");
173 cc_params[0] = alt_cc ? alt_cc : (u8*)"gcc";
174 }
175
176 #endif /* __APPLE__ */
177
178 }
179
180 while (--argc) {
181 u8* cur = *(++argv);
182
183 if (!strncmp(cur, "-B", 2)) {
184
185 if (!be_quiet) WARNF("-B is already set, overriding");
186
187 if (!cur[2] && argc > 1) { argc--; argv++; }
188 continue;
189
190 }
191
192 if (!strcmp(cur, "-integrated-as")) continue;
193
194 if (!strcmp(cur, "-pipe")) continue;
195
196 #if defined(__FreeBSD__) && defined(__x86_64__)
197 if (!strcmp(cur, "-m32")) m32_set = 1;
198 #endif
199
200 if (!strcmp(cur, "-fsanitize=address") ||
201 !strcmp(cur, "-fsanitize=memory")) asan_set = 1;
202
203 if (strstr(cur, "FORTIFY_SOURCE")) fortify_set = 1;
204
205 cc_params[cc_par_cnt++] = cur;
206
207 }
208
209 cc_params[cc_par_cnt++] = "-B";
210 cc_params[cc_par_cnt++] = as_path;
211
212 if (clang_mode)
213 cc_params[cc_par_cnt++] = "-no-integrated-as";
214
215 if (getenv("AFL_HARDEN")) {
216
217 cc_params[cc_par_cnt++] = "-fstack-protector-all";
218
219 if (!fortify_set)
220 cc_params[cc_par_cnt++] = "-D_FORTIFY_SOURCE=2";
221
222 }
223
224 if (asan_set) {
225
226 /* Pass this on to afl-as to adjust map density. */
227
228 setenv("AFL_USE_ASAN", "1", 1);
229
230 } else if (getenv("AFL_USE_ASAN")) {
231
232 if (getenv("AFL_USE_MSAN"))
233 FATAL("ASAN and MSAN are mutually exclusive");
234
235 if (getenv("AFL_HARDEN"))
236 FATAL("ASAN and AFL_HARDEN are mutually exclusive");
237
238 cc_params[cc_par_cnt++] = "-U_FORTIFY_SOURCE";
239 cc_params[cc_par_cnt++] = "-fsanitize=address";
240
241 } else if (getenv("AFL_USE_MSAN")) {
242
243 if (getenv("AFL_USE_ASAN"))
244 FATAL("ASAN and MSAN are mutually exclusive");
245
246 if (getenv("AFL_HARDEN"))
247 FATAL("MSAN and AFL_HARDEN are mutually exclusive");
248
249 cc_params[cc_par_cnt++] = "-U_FORTIFY_SOURCE";
250 cc_params[cc_par_cnt++] = "-fsanitize=memory";
251
252
253 }
254
255 if (!getenv("AFL_DONT_OPTIMIZE")) {
256
257 #if defined(__FreeBSD__) && defined(__x86_64__)
258
259 /* On 64-bit FreeBSD systems, clang -g -m32 is broken, but -m32 itself
260 works OK. This has nothing to do with us, but let's avoid triggering
261 that bug. */
262
263 if (!clang_mode || !m32_set)
264 cc_params[cc_par_cnt++] = "-g";
265
266 #else
267
268 cc_params[cc_par_cnt++] = "-g";
269
270 #endif
271
272 cc_params[cc_par_cnt++] = "-O3";
273 cc_params[cc_par_cnt++] = "-funroll-loops";
274
275 /* Two indicators that you're building for fuzzing; one of them is
276 AFL-specific, the other is shared with libfuzzer. */
277
278 cc_params[cc_par_cnt++] = "-D__AFL_COMPILER=1";
279 cc_params[cc_par_cnt++] = "-DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION=1";
280
281 }
282
283 if (getenv("AFL_NO_BUILTIN")) {
284
285 cc_params[cc_par_cnt++] = "-fno-builtin-strcmp";
286 cc_params[cc_par_cnt++] = "-fno-builtin-strncmp";
287 cc_params[cc_par_cnt++] = "-fno-builtin-strcasecmp";
288 cc_params[cc_par_cnt++] = "-fno-builtin-strncasecmp";
289 cc_params[cc_par_cnt++] = "-fno-builtin-memcmp";
290 cc_params[cc_par_cnt++] = "-fno-builtin-strstr";
291 cc_params[cc_par_cnt++] = "-fno-builtin-strcasestr";
292
293 }
294
295 cc_params[cc_par_cnt] = NULL;
296
297 }
298
299
300 /* Main entry point */
301
main(int argc,char ** argv)302 int main(int argc, char** argv) {
303
304 if (isatty(2) && !getenv("AFL_QUIET")) {
305
306 SAYF(cCYA "afl-cc " cBRI VERSION cRST " by <lcamtuf@google.com>\n");
307
308 } else be_quiet = 1;
309
310 if (argc < 2) {
311
312 SAYF("\n"
313 "This is a helper application for afl-fuzz. It serves as a drop-in replacement\n"
314 "for gcc or clang, letting you recompile third-party code with the required\n"
315 "runtime instrumentation. A common use pattern would be one of the following:\n\n"
316
317 " CC=%s/afl-gcc ./configure\n"
318 " CXX=%s/afl-g++ ./configure\n\n"
319
320 "You can specify custom next-stage toolchain via AFL_CC, AFL_CXX, and AFL_AS.\n"
321 "Setting AFL_HARDEN enables hardening optimizations in the compiled code.\n\n",
322 BIN_PATH, BIN_PATH);
323
324 exit(1);
325
326 }
327
328 find_as(argv[0]);
329
330 edit_params(argc, argv);
331
332 execvp(cc_params[0], (char**)cc_params);
333
334 FATAL("Oops, failed to execute '%s' - check your PATH", cc_params[0]);
335
336 return 0;
337
338 }
339