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This commit is contained in:
Dominik Maier
2020-03-26 19:44:44 +01:00
parent 6832435326
commit 97a1af39f7
7 changed files with 71 additions and 112 deletions
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3
docs/custom_mutators.md
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@ -27,7 +27,7 @@ performed with the custom mutator.
C/C++:
```c
void afl_custom_init(unsigned int seed);
void afl_custom_init(void *afl, unsigned int seed);
size_t afl_custom_fuzz(uint8_t** buf, size_t buf_size, uint8_t* add_buf,
size_t add_buf_size, size_t max_size);
size_t afl_custom_write_to_testcase(uint8_t* buf, size_t buf_size, uint8_t** out_buf);
@ -39,6 +39,7 @@ uint8_t afl_custom_havoc_mutation_probability(void);
uint8_t afl_custom_queue_get(const uint8_t* filename);
void afl_custom_queue_new_entry(const uint8_t* filename_new_queue,
const uint8_t* filename_orig_queue);
void afl_custom_deinit(void *data);
```
Python:

35
examples/custom_mutators/example.c
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@ -15,6 +15,7 @@
#include <stdio.h>
#define DATA_SIZE (100)
#define INITIAL_BUF_SIZE (16384)
static const char *commands[] = {
@ -28,6 +29,8 @@ typedef struct my_mutator {
afl_t *afl;
// any additional data here!
size_t pre_save_size;
u8 * pre_save_buf;
} my_mutator_t;
@ -56,6 +59,16 @@ my_mutator_t *afl_custom_init(afl_t *afl, unsigned int seed) {
data->afl = afl;
data->pre_save_buf = malloc(INITIAL_BUF_SIZE);
if (!data->pre_save_buf) {
free(data);
return NULL;
}
data->pre_save_size = INITIAL_BUF_SIZE;
return data;
}
@ -125,12 +138,23 @@ size_t afl_custom_fuzz(my_mutator_t *data, uint8_t **buf, size_t buf_size,
size_t afl_custom_pre_save(my_mutator_t *data, uint8_t *buf, size_t buf_size,
uint8_t *out_buf, size_t out_buf_size) {
// In case we need more than out_buf_size, we return that amount and get
// called again.
if (out_buf_size < 32000) return 32000;
if (data->pre_save_size < buf_size + 5) {
memcpy(out_buf, buf, buf_size);
out_buf_size = buf_size;
data->pre_save_buf = realloc(data->pre_save_buf, buf_size + 5);
if (!data->pre_save_buf) {
perror("custom mutator realloc");
free(data);
return -1;
}
data->pre_save_size = buf_size + 5;
}
memcpy(out_buf + 5, buf, buf_size);
out_buf_size = buf_size + 5;
out_buf[0] = 'A';
out_buf[1] = 'F';
out_buf[2] = 'L';
@ -322,6 +346,7 @@ void afl_custom_queue_new_entry(my_mutator_t * data,
*/
void afl_custom_deinit(my_mutator_t *data) {
free(data->pre_save_buf);
free(data);
}

19
include/afl-fuzz.h
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@ -30,9 +30,6 @@
#define AFL_MAIN
#define MESSAGES_TO_STDOUT
/* We preallocate a buffer of this size for afl_custom_pre_save */
#define PRE_SAVE_BUF_INIT_SIZE (16384)
#ifndef _GNU_SOURCE
#define _GNU_SOURCE 1
#endif
@ -296,8 +293,8 @@ typedef struct py_mutator {
void * afl_state;
void * py_data;
PyObject *scratch_buf;
size_t scratch_size;
u8 * pre_save_buf;
size_t pre_save_size;
} py_mutator_t;
@ -641,13 +638,13 @@ struct custom_mutator {
* @param[in] data pointer returned in afl_custom_init for this fuzz case
* @param[in] buf Buffer containing the test case to be executed
* @param[in] buf_size Size of the test case
* @param[out] out_buf Pointer to the buffer of storing the test case after
* processing. External library should allocate memory for out_buf. AFL++
* will release the memory after saving the test case.
* @return Size of the output buffer after processing
* @param[out] out_buf Pointer to the buffer storing the test case after
* processing. External library should allocate memory for out_buf.
* It can chose to alter buf in-place, if the space is large enough.
* @return Size of the output buffer.
*/
size_t (*afl_custom_pre_save)(void *data, u8 *buf, size_t buf_size,
u8 *out_buf, size_t out_buf_size);
u8 **out_buf);
/**
* This method is called at the start of each trimming operation and receives
@ -783,7 +780,7 @@ u8 trim_case_custom(afl_state_t *, struct queue_entry *q, u8 *in_buf);
void finalize_py_module(void *);
size_t pre_save_py(void *, u8 *, size_t, u8 *, size_t);
size_t pre_save_py(void *, u8 *, size_t, u8 **);
u32 init_trim_py(void *, u8 *, size_t);
u32 post_trim_py(void *, u8);
void trim_py(void *, u8 **, size_t *);

11
src/afl-fuzz-mutators.c
View File

@ -135,18 +135,9 @@ void load_custom_mutator(afl_state_t *afl, const char *fn) {
/* "afl_custom_pre_save", optional */
afl->mutator->afl_custom_pre_save = dlsym(dh, "afl_custom_pre_save");
if (!afl->mutator->afl_custom_pre_save) {
if (!afl->mutator->afl_custom_pre_save)
WARNF("Symbol 'afl_custom_pre_save' not found.");
} else {
/* if we have a pre_save hook, prealloc some memory. */
afl->mutator->pre_save_buf = ck_alloc(PRE_SAVE_BUF_INIT_SIZE * sizeof(u8));
afl->mutator->pre_save_size = PRE_SAVE_BUF_INIT_SIZE;
}
u8 notrim = 0;
/* "afl_custom_init_trim", optional */
afl->mutator->afl_custom_init_trim = dlsym(dh, "afl_custom_init_trim");

54
src/afl-fuzz-python.c
View File

@ -307,14 +307,8 @@ void load_custom_mutator_py(afl_state_t *afl, char *module_name) {
is quite different from the custom mutator. */
afl->mutator->afl_custom_fuzz = fuzz_py;
if (py_functions[PY_FUNC_PRE_SAVE]) {
if (py_functions[PY_FUNC_PRE_SAVE])
afl->mutator->afl_custom_pre_save = pre_save_py;
/* if we have a pre_save hook, prealloc some memory. */
afl->mutator->pre_save_buf = ck_alloc(PRE_SAVE_BUF_INIT_SIZE * sizeof(u8));
afl->mutator->pre_save_size = PRE_SAVE_BUF_INIT_SIZE;
}
if (py_functions[PY_FUNC_INIT_TRIM])
afl->mutator->afl_custom_init_trim = init_trim_py;
@ -344,39 +338,18 @@ void load_custom_mutator_py(afl_state_t *afl, char *module_name) {
}
size_t pre_save_py(void *py_mutator, u8 *buf, size_t buf_size, u8 *out_buf,
size_t out_buf_size) {
size_t pre_save_py(void *py_mutator, u8 *buf, size_t buf_size, u8 **out_buf) {
size_t py_out_buf_size;
PyObject *py_args, *py_value;
if (((py_mutator_t *)py_mutator)->scratch_buf) {
/* We are being recalled from an earlier run
where we didn't have enough mem. */
if (((py_mutator_t *)py_mutator)->scratch_size < out_buf_size) {
FATAL("out_buf is still too small after resizing in custom mutator.");
}
py_value = ((py_mutator_t *)py_mutator)->scratch_buf;
py_out_buf_size = ((py_mutator_t *)py_mutator)->scratch_size;
((py_mutator_t *)py_mutator)->scratch_buf = NULL;
py_out_buf_size = 0;
memcpy(out_buf, PyByteArray_AsString(py_value), py_out_buf_size);
Py_DECREF(py_value);
return py_out_buf_size;
}
PyObject * py_args, *py_value;
py_mutator_t *py = (py_mutator_t *)py_mutator;
py_args = PyTuple_New(1);
py_value = PyByteArray_FromStringAndSize(buf, buf_size);
if (!py_value) {
Py_DECREF(py_args);
FATAL("Failed to convert arguments");
FATAL("Failed to convert arguments in custom pre_save");
}
@ -390,25 +363,26 @@ size_t pre_save_py(void *py_mutator, u8 *buf, size_t buf_size, u8 *out_buf,
if (py_value != NULL) {
py_out_buf_size = PyByteArray_Size(py_value);
if (py_out_buf_size > out_buf_size) {
if (py_out_buf_size > py->pre_save_size) {
/* Not enough space!
We will get called again right after resizing the buf.
Keep the references to our data for now. */
((py_mutator_t *)py_mutator)->scratch_buf = py_value;
((py_mutator_t *)py_mutator)->scratch_size = py_out_buf_size;
return py_out_buf_size;
Let's resize our buf */
py->pre_save_buf = ck_realloc(py->pre_save_buf, py_out_buf_size);
py->pre_save_size = py_out_buf_size;
}
memcpy(out_buf, PyByteArray_AsString(py_value), py_out_buf_size);
memcpy(py->pre_save_buf, PyByteArray_AsString(py_value), py_out_buf_size);
Py_DECREF(py_value);
*out_buf = py->pre_save_buf;
return py_out_buf_size;
} else {
PyErr_Print();
FATAL("Call failed");
FATAL("Python custom mutator: pre_save call failed.");
}

43
src/afl-fuzz-run.c
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@ -214,47 +214,18 @@ void write_to_testcase(afl_state_t *afl, void *mem, u32 len) {
lseek(fd, 0, SEEK_SET);
if (afl->mutator && afl->mutator->afl_custom_pre_save) {
if (unlikely(afl->mutator && afl->mutator->afl_custom_pre_save)) {
if (unlikely(afl->mutator->pre_save_size < len)) {
u8 *new_buf = NULL;
afl->mutator->pre_save_buf =
ck_realloc(afl->mutator->pre_save_buf, len * sizeof(u8));
afl->mutator->pre_save_size = len;
size_t new_size = afl->mutator->afl_custom_pre_save(afl->mutator->data, mem,
len, &new_buf);
}
u8 buf_written = 0;
while (!buf_written) {
buf_written = 1;
size_t new_size = afl->mutator->afl_custom_pre_save(
afl->mutator->data, mem, len, afl->mutator->pre_save_buf,
afl->mutator->pre_save_size);
if (unlikely(new_size) == 0) {
/* custom_pre_save wants us to use the old buf */
ck_write(fd, mem, len, afl->fsrv.out_file);
} else if (unlikely(new_size) > afl->mutator->pre_save_size) {
/* The custom func needs more space.
Realloc and call again. */
afl->mutator->pre_save_buf =
ck_realloc(afl->mutator->pre_save_buf, new_size * sizeof(u8));
afl->mutator->pre_save_size = new_size;
buf_written = 0;
continue;
} else {
if (unlikely(new_size <= 0 || !new_buf))
FATAL("Custom_pre_save failed (ret: %ld)", new_size);
/* everything as planned. use the new data. */
ck_write(fd, afl->mutator->pre_save_buf, new_size, afl->fsrv.out_file);
}
}
ck_write(fd, new_buf, new_size, afl->fsrv.out_file);
} else {