1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
|
#ifndef CUSTOM_MUTATOR_HELPERS
#define CUSTOM_MUTATOR_HELPERS
#include "config.h"
#include "types.h"
#include <stdlib.h>
#define INITIAL_GROWTH_SIZE (64)
#define RAND_BELOW(limit) (rand() % (limit))
/* Use in a struct: creates a name_buf and a name_size variable. */
#define BUF_VAR(type, name) \
type * name##_buf; \
size_t name##_size;
/* this fills in `&structptr->something_buf, &structptr->something_size`. */
#define BUF_PARAMS(struct, name) \
(void **)&struct->name##_buf, &struct->name##_size
typedef struct {
} afl_t;
static void surgical_havoc_mutate(u8 *out_buf, s32 begin, s32 end) {
static s8 interesting_8[] = {INTERESTING_8};
static s16 interesting_16[] = {INTERESTING_8, INTERESTING_16};
static s32 interesting_32[] = {INTERESTING_8, INTERESTING_16, INTERESTING_32};
switch (RAND_BELOW(12)) {
case 0: {
/* Flip a single bit somewhere. Spooky! */
s32 bit_idx = ((RAND_BELOW(end - begin) + begin) << 3) + RAND_BELOW(8);
out_buf[bit_idx >> 3] ^= 128 >> (bit_idx & 7);
break;
}
case 1: {
/* Set byte to interesting value. */
u8 val = interesting_8[RAND_BELOW(sizeof(interesting_8))];
out_buf[(RAND_BELOW(end - begin) + begin)] = val;
break;
}
case 2: {
/* Set word to interesting value, randomly choosing endian. */
if (end - begin < 2) break;
s32 byte_idx = (RAND_BELOW(end - begin) + begin);
if (byte_idx >= end - 1) break;
switch (RAND_BELOW(2)) {
case 0:
*(u16 *)(out_buf + byte_idx) =
interesting_16[RAND_BELOW(sizeof(interesting_16) >> 1)];
break;
case 1:
*(u16 *)(out_buf + byte_idx) =
SWAP16(interesting_16[RAND_BELOW(sizeof(interesting_16) >> 1)]);
break;
}
break;
}
case 3: {
/* Set dword to interesting value, randomly choosing endian. */
if (end - begin < 4) break;
s32 byte_idx = (RAND_BELOW(end - begin) + begin);
if (byte_idx >= end - 3) break;
switch (RAND_BELOW(2)) {
case 0:
*(u32 *)(out_buf + byte_idx) =
interesting_32[RAND_BELOW(sizeof(interesting_32) >> 2)];
break;
case 1:
*(u32 *)(out_buf + byte_idx) =
SWAP32(interesting_32[RAND_BELOW(sizeof(interesting_32) >> 2)]);
break;
}
break;
}
case 4: {
/* Set qword to interesting value, randomly choosing endian. */
if (end - begin < 8) break;
s32 byte_idx = (RAND_BELOW(end - begin) + begin);
if (byte_idx >= end - 7) break;
switch (RAND_BELOW(2)) {
case 0:
*(u64 *)(out_buf + byte_idx) =
(s64)interesting_32[RAND_BELOW(sizeof(interesting_32) >> 2)];
break;
case 1:
*(u64 *)(out_buf + byte_idx) = SWAP64(
(s64)interesting_32[RAND_BELOW(sizeof(interesting_32) >> 2)]);
break;
}
break;
}
case 5: {
/* Randomly subtract from byte. */
out_buf[(RAND_BELOW(end - begin) + begin)] -= 1 + RAND_BELOW(ARITH_MAX);
break;
}
case 6: {
/* Randomly add to byte. */
out_buf[(RAND_BELOW(end - begin) + begin)] += 1 + RAND_BELOW(ARITH_MAX);
break;
}
case 7: {
/* Randomly subtract from word, random endian. */
if (end - begin < 2) break;
s32 byte_idx = (RAND_BELOW(end - begin) + begin);
if (byte_idx >= end - 1) break;
if (RAND_BELOW(2)) {
*(u16 *)(out_buf + byte_idx) -= 1 + RAND_BELOW(ARITH_MAX);
} else {
u16 num = 1 + RAND_BELOW(ARITH_MAX);
*(u16 *)(out_buf + byte_idx) =
SWAP16(SWAP16(*(u16 *)(out_buf + byte_idx)) - num);
}
break;
}
case 8: {
/* Randomly add to word, random endian. */
if (end - begin < 2) break;
s32 byte_idx = (RAND_BELOW(end - begin) + begin);
if (byte_idx >= end - 1) break;
if (RAND_BELOW(2)) {
*(u16 *)(out_buf + byte_idx) += 1 + RAND_BELOW(ARITH_MAX);
} else {
u16 num = 1 + RAND_BELOW(ARITH_MAX);
*(u16 *)(out_buf + byte_idx) =
SWAP16(SWAP16(*(u16 *)(out_buf + byte_idx)) + num);
}
break;
}
case 9: {
/* Randomly subtract from dword, random endian. */
if (end - begin < 4) break;
s32 byte_idx = (RAND_BELOW(end - begin) + begin);
if (byte_idx >= end - 3) break;
if (RAND_BELOW(2)) {
*(u32 *)(out_buf + byte_idx) -= 1 + RAND_BELOW(ARITH_MAX);
} else {
u32 num = 1 + RAND_BELOW(ARITH_MAX);
*(u32 *)(out_buf + byte_idx) =
SWAP32(SWAP32(*(u32 *)(out_buf + byte_idx)) - num);
}
break;
}
case 10: {
/* Randomly add to dword, random endian. */
if (end - begin < 4) break;
s32 byte_idx = (RAND_BELOW(end - begin) + begin);
if (byte_idx >= end - 3) break;
if (RAND_BELOW(2)) {
*(u32 *)(out_buf + byte_idx) += 1 + RAND_BELOW(ARITH_MAX);
} else {
u32 num = 1 + RAND_BELOW(ARITH_MAX);
*(u32 *)(out_buf + byte_idx) =
SWAP32(SWAP32(*(u32 *)(out_buf + byte_idx)) + num);
}
break;
}
case 11: {
/* Just set a random byte to a random value. Because,
why not. We use XOR with 1-255 to eliminate the
possibility of a no-op. */
out_buf[(RAND_BELOW(end - begin) + begin)] ^= 1 + RAND_BELOW(255);
break;
}
}
}
/* This function calculates the next power of 2 greater or equal its argument.
@return The rounded up power of 2 (if no overflow) or 0 on overflow.
*/
static inline size_t next_pow2(size_t in) {
if (in == 0 || in > (size_t)-1)
return 0; /* avoid undefined behaviour under-/overflow */
size_t out = in - 1;
out |= out >> 1;
out |= out >> 2;
out |= out >> 4;
out |= out >> 8;
out |= out >> 16;
return out + 1;
}
/* This function makes sure *size is > size_needed after call.
It will realloc *buf otherwise.
*size will grow exponentially as per:
https://blog.mozilla.org/nnethercote/2014/11/04/please-grow-your-buffers-exponentially/
Will return NULL and free *buf if size_needed is <1 or realloc failed.
@return For convenience, this function returns *buf.
*/
static inline void *maybe_grow(void **buf, size_t *size, size_t size_needed) {
/* No need to realloc */
if (likely(size_needed && *size >= size_needed)) return *buf;
/* No initial size was set */
if (size_needed < INITIAL_GROWTH_SIZE) size_needed = INITIAL_GROWTH_SIZE;
/* grow exponentially */
size_t next_size = next_pow2(size_needed);
/* handle overflow */
if (!next_size) { next_size = size_needed; }
/* alloc */
*buf = realloc(*buf, next_size);
*size = *buf ? next_size : 0;
return *buf;
}
/* Swaps buf1 ptr and buf2 ptr, as well as their sizes */
static inline void afl_swap_bufs(void **buf1, size_t *size1, void **buf2,
size_t *size2) {
void * scratch_buf = *buf1;
size_t scratch_size = *size1;
*buf1 = *buf2;
*size1 = *size2;
*buf2 = scratch_buf;
*size2 = scratch_size;
}
#undef INITIAL_GROWTH_SIZE
#endif
|
