diff options
Diffstat (limited to 'examples/custom_mutators/example.c')
| -rw-r--r-- | examples/custom_mutators/example.c | 167 |
1 files changed, 115 insertions, 52 deletions
diff --git a/examples/custom_mutators/example.c b/examples/custom_mutators/example.c index 560a5919..c8200b26 100644 --- a/examples/custom_mutators/example.c +++ b/examples/custom_mutators/example.c @@ -12,6 +12,7 @@ #include <stdint.h> #include <stdlib.h> #include <string.h> +#include <stdio.h> #define DATA_SIZE (100) @@ -23,32 +24,47 @@ static const char *commands[] = { }; - typedef struct my_mutator { afl_t *afl; + // any additional data here! + size_t trim_size_current; + int trimmming_steps; + int cur_step; + + // Reused buffers: + BUF_VAR(u8, fuzz); + BUF_VAR(u8, data); + BUF_VAR(u8, havoc); + BUF_VAR(u8, trim); + BUF_VAR(u8, pre_save); } my_mutator_t; /** * Initialize this custom mutator * - * @param[in] afl a pointer to the internal state object. Can be ignored for now. - * @param[in] seed A seed for this mutator - the same seed should always mutate in the same way. + * @param[in] afl a pointer to the internal state object. Can be ignored for + * now. + * @param[in] seed A seed for this mutator - the same seed should always mutate + * in the same way. * @return Pointer to the data object this custom mutator instance should use. * There may be multiple instances of this mutator in one afl-fuzz run! - * Returns NULL on error. + * Return NULL on error. */ my_mutator_t *afl_custom_init(afl_t *afl, unsigned int seed) { - srand(seed); // needed also by surgical_havoc_mutate() + srand(seed); // needed also by surgical_havoc_mutate() my_mutator_t *data = calloc(1, sizeof(my_mutator_t)); if (!data) { + perror("afl_custom_init alloc"); return NULL; + } + data->afl = afl; return data; @@ -63,14 +79,16 @@ my_mutator_t *afl_custom_init(afl_t *afl, unsigned int seed) { * @param[in] data pointer returned in afl_custom_init for this fuzz case * @param[in] buf Pointer to input data to be mutated * @param[in] buf_size Size of input data + * @param[out] out_buf the buffer we will work on. we can reuse *buf. NULL on + * error. * @param[in] add_buf Buffer containing the additional test case * @param[in] add_buf_size Size of the additional test case * @param[in] max_size Maximum size of the mutated output. The mutation must not * produce data larger than max_size. * @return Size of the mutated output. */ -size_t afl_custom_fuzz(my_mutator_t *data, uint8_t **buf, size_t buf_size, - uint8_t *add_buf, +size_t afl_custom_fuzz(my_mutator_t *data, uint8_t *buf, size_t buf_size, + u8 **out_buf, uint8_t *add_buf, size_t add_buf_size, // add_buf can be NULL size_t max_size) { @@ -78,9 +96,15 @@ size_t afl_custom_fuzz(my_mutator_t *data, uint8_t **buf, size_t buf_size, // the fuzzer size_t mutated_size = DATA_SIZE <= max_size ? DATA_SIZE : max_size; - if (mutated_size > buf_size) *buf = realloc(*buf, mutated_size); + // maybe_grow is optimized to be quick for reused buffers. + u8 *mutated_out = maybe_grow(BUF_PARAMS(data, fuzz), mutated_size); + if (!mutated_out) { - uint8_t *mutated_out = *buf; + *out_buf = NULL; + perror("custom mutator allocation (maybe_grow)"); + return 0; /* afl-fuzz will very likely error out after this. */ + + } // Randomly select a command string to add as a header to the packet memcpy(mutated_out, commands[rand() % 3], 3); @@ -94,6 +118,7 @@ size_t afl_custom_fuzz(my_mutator_t *data, uint8_t **buf, size_t buf_size, } + *out_buf = mutated_out; return mutated_size; } @@ -109,28 +134,35 @@ size_t afl_custom_fuzz(my_mutator_t *data, uint8_t **buf, size_t buf_size, * @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 containing 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 + * processing. External library should allocate memory for out_buf. + * The buf pointer may be reused (up to the given buf_size); + * @return Size of the output buffer after processing or the needed amount. + * A return of 0 indicates an error. */ -size_t afl_custom_pre_save(my_mutator_t *data, uint8_t *buf, size_t buf_size, uint8_t **out_buf) { +size_t afl_custom_pre_save(my_mutator_t *data, uint8_t *buf, size_t buf_size, + uint8_t **out_buf) { + + uint8_t *pre_save_buf = maybe_grow(BUF_PARAMS(data, pre_save), buf_size + 5); + if (!pre_save_buf) { - size_t out_buf_size; + perror("custom mutator realloc failed."); + *out_buf = NULL; + return 0; - out_buf_size = buf_size; + } - // External mutator should allocate memory for `out_buf` - *out_buf = malloc(out_buf_size); - memcpy(*out_buf, buf, out_buf_size); + memcpy(pre_save_buf + 5, buf, buf_size); + pre_save_buf[0] = 'A'; + pre_save_buf[1] = 'F'; + pre_save_buf[2] = 'L'; + pre_save_buf[3] = '+'; + pre_save_buf[4] = '+'; - return out_buf_size; + *out_buf = pre_save_buf; -} + return buf_size + 5; -static uint8_t *trim_buf; -static size_t trim_buf_size; -static int trimmming_steps; -static int cur_step; +} /** * This method is called at the start of each trimming operation and receives @@ -151,25 +183,36 @@ static int cur_step; * @param data pointer returned in afl_custom_init for this fuzz case * @param buf Buffer containing the test case * @param buf_size Size of the test case - * @return The amount of possible iteration steps to trim the input + * @return The amount of possible iteration steps to trim the input. + * negative on error. */ -int afl_custom_init_trim(my_mutator_t *data, uint8_t *buf, size_t buf_size) { +int32_t afl_custom_init_trim(my_mutator_t *data, uint8_t *buf, + size_t buf_size) { // We simply trim once - trimmming_steps = 1; + data->trimmming_steps = 1; - cur_step = 0; - trim_buf = buf; - trim_buf_size = buf_size; + data->cur_step = 0; - return trimmming_steps; + if (!maybe_grow(BUF_PARAMS(data, trim), buf_size)) { + + perror("init_trim grow"); + return -1; + + } + + memcpy(data->trim_buf, buf, buf_size); + + data->trim_size_current = buf_size; + + return data->trimmming_steps; } /** * This method is called for each trimming operation. It doesn't have any * arguments because we already have the initial buffer from init_trim and we - * can memorize the current state in global variables. This can also save + * can memorize the current state in *data. This can also save * reparsing steps for each iteration. It should return the trimmed input * buffer, where the returned data must not exceed the initial input data in * length. Returning anything that is larger than the original data (passed @@ -179,18 +222,18 @@ int afl_custom_init_trim(my_mutator_t *data, uint8_t *buf, size_t buf_size) { * * @param[in] data pointer returned in afl_custom_init for this fuzz case * @param[out] out_buf Pointer to the buffer containing the trimmed test case. - * External library should allocate memory for out_buf. AFL++ will release - * the memory after saving the test case. - * @param[out] out_buf_size Pointer to the size of the trimmed test case + * External library should allocate memory for out_buf. + * AFL++ will not release the memory after saving the test case. + * Keep a ref in *data. + * *out_buf = NULL is treated as error. + * @return Pointer to the size of the trimmed test case */ -void afl_custom_trim(my_mutator_t *data, uint8_t **out_buf, size_t *out_buf_size) { +size_t afl_custom_trim(my_mutator_t *data, uint8_t **out_buf) { - *out_buf_size = trim_buf_size - 1; + *out_buf = data->trim_buf; - // External mutator should allocate memory for `out_buf` - *out_buf = malloc(*out_buf_size); // Remove the last byte of the trimming input - memcpy(*out_buf, trim_buf, *out_buf_size); + return data->trim_size_current - 1; } @@ -204,18 +247,18 @@ void afl_custom_trim(my_mutator_t *data, uint8_t **out_buf, size_t *out_buf_size * @param[in] data pointer returned in afl_custom_init for this fuzz case * @param success Indicates if the last trim operation was successful. * @return The next trim iteration index (from 0 to the maximum amount of - * steps returned in init_trim) + * steps returned in init_trim). negative ret on failure. */ -int afl_custom_post_trim(my_mutator_t *data, int success) { +int32_t afl_custom_post_trim(my_mutator_t *data, int success) { if (success) { - ++cur_step; - return cur_step; + ++data->cur_step; + return data->cur_step; } - return trimmming_steps; + return data->trimmming_steps; } @@ -226,26 +269,40 @@ int afl_custom_post_trim(my_mutator_t *data, int success) { * (Optional) * * @param[in] data pointer returned in afl_custom_init for this fuzz case - * @param[inout] buf Pointer to the input data to be mutated and the mutated + * @param[in] buf Pointer to the input data to be mutated and the mutated * output * @param[in] buf_size Size of input data + * @param[out] out_buf The output buffer. buf can be reused, if the content + * fits. *out_buf = NULL is treated as error. * @param[in] max_size Maximum size of the mutated output. The mutation must * not produce data larger than max_size. * @return Size of the mutated output. */ -size_t afl_custom_havoc_mutation(my_mutator_t *data, uint8_t **buf, size_t buf_size, - size_t max_size) { +size_t afl_custom_havoc_mutation(my_mutator_t *data, u8 *buf, size_t buf_size, + u8 **out_buf, size_t max_size) { if (buf_size == 0) { - *buf = realloc(*buf, 1); - **buf = rand() % 256; + *out_buf = maybe_grow(BUF_PARAMS(data, havoc), 1); + if (!*out_buf) { + + perror("custom havoc: maybe_grow"); + return 0; + + } + + **out_buf = rand() % 256; buf_size = 1; + } else { + + // We reuse buf here. It's legal and faster. + *out_buf = buf; + } size_t victim = rand() % buf_size; - (*buf)[victim] += rand() % 10; + (*out_buf)[victim] += rand() % 10; return buf_size; @@ -292,7 +349,8 @@ uint8_t afl_custom_queue_get(my_mutator_t *data, const uint8_t *filename) { * @param filename_new_queue File name of the new queue entry * @param filename_orig_queue File name of the original queue entry */ -void afl_custom_queue_new_entry(my_mutator_t *data, const uint8_t *filename_new_queue, +void afl_custom_queue_new_entry(my_mutator_t * data, + const uint8_t *filename_new_queue, const uint8_t *filename_orig_queue) { /* Additional analysis on the original or new test case */ @@ -306,6 +364,11 @@ void afl_custom_queue_new_entry(my_mutator_t *data, const uint8_t *filename_new_ */ void afl_custom_deinit(my_mutator_t *data) { + free(data->pre_save_buf); + free(data->havoc_buf); + free(data->data_buf); + free(data->fuzz_buf); + free(data->trim_buf); free(data); } |