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#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