diff options
Diffstat (limited to 'examples')
| -rw-r--r-- | examples/custom_mutators/custom_mutator_helpers.h | 61 | ||||
| -rw-r--r-- | examples/custom_mutators/example.c | 113 | ||||
| -rw-r--r-- | examples/post_library/post_library.so.c | 84 | ||||
| -rw-r--r-- | examples/post_library/post_library_png.so.c | 71 |
4 files changed, 239 insertions, 90 deletions
diff --git a/examples/custom_mutators/custom_mutator_helpers.h b/examples/custom_mutators/custom_mutator_helpers.h index cd3a15f0..0dc00d96 100644 --- a/examples/custom_mutators/custom_mutator_helpers.h +++ b/examples/custom_mutators/custom_mutator_helpers.h @@ -5,8 +5,18 @@ #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 filles in `&structptr->something_buf, &structptr->something_size`. */ +#define BUF_PARAMS(struct, name) \ + (void **)&struct->name##_buf, &struct->name##_size + typedef struct { } afl_t; @@ -267,5 +277,56 @@ static void surgical_havoc_mutate(u8 *out_buf, s32 begin, s32 end) { } +/* This function makes sure *size is > size_needed after call. + It changes buf and size in-place, if needed. + 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 if size_needed is <1 or *size is negative or malloc Failed. + @return For convenience, this function returns *buf. NULL on error. + */ +static inline void *maybe_grow(void **buf, size_t *size, size_t size_needed) { + + /* Oops. found a bug? */ + if (unlikely(size_needed < 1)) return NULL; + + /* No need to realloc */ + if (likely(*size >= size_needed)) return *buf; + if (unlikely(*size < 0)) return NULL; + /* No inital size was set */ + if (*size == 0) *size = INITIAL_GROWTH_SIZE; + while (*size < size_needed) { + + *size *= 2; + if ((*size) < 0) { + + /* An overflow occurred. Fall back to size_needed */ + *size = size_needed; + + } + + } + + *buf = realloc(*buf, *size); + + return *buf; + +} + +/* Swaps buf1 ptr and buf2 ptr, as well as their sizes */ +static inline void 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 diff --git a/examples/custom_mutators/example.c b/examples/custom_mutators/example.c index 4b0a461b..54fc9d47 100644 --- a/examples/custom_mutators/example.c +++ b/examples/custom_mutators/example.c @@ -15,7 +15,6 @@ #include <stdio.h> #define DATA_SIZE (100) -#define INITIAL_BUF_SIZE (16384) static const char *commands[] = { @@ -28,9 +27,19 @@ static const char *commands[] = { typedef struct my_mutator { afl_t *afl; + // any additional data here! - size_t pre_save_size; - u8 * pre_save_buf; + uint8_t *trim_buf; + size_t trim_buf_size; + int trimmming_steps; + int cur_step; + + // Reused buffers: + BUF_VAR(u8, fuzz); + BUF_VAR(u8, data); + BUF_VAR(u8, havoc); + BUF_VAR(u8, trim_out); + BUF_VAR(u8, pre_save); } my_mutator_t; @@ -59,16 +68,6 @@ 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; } @@ -85,20 +84,25 @@ my_mutator_t *afl_custom_init(afl_t *afl, unsigned int seed) { * @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. + * @return Size of the mutated output. Negative return will abort fuzzing. */ -size_t afl_custom_fuzz(my_mutator_t *data, uint8_t **buf, size_t buf_size, - uint8_t *add_buf, - size_t add_buf_size, // add_buf can be NULL - size_t max_size) { +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) { // Make sure that the packet size does not exceed the maximum size expected by // 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) { + + perror("custom mutator allocation (maybe_grow)"); + return -1; /* afl-fuzz will very likely error out after this. */ - uint8_t *mutated_out = *buf; + } // Randomly select a command string to add as a header to the packet memcpy(mutated_out, commands[rand() % 3], 3); @@ -112,6 +116,7 @@ size_t afl_custom_fuzz(my_mutator_t *data, uint8_t **buf, size_t buf_size, } + *out_buf = mutated_out; return mutated_size; } @@ -137,11 +142,10 @@ size_t afl_custom_pre_save(my_mutator_t *data, uint8_t *buf, size_t buf_size, if (data->pre_save_size < buf_size + 5) { - data->pre_save_buf = realloc(data->pre_save_buf, buf_size + 5); + data->pre_save_buf = maybe_grow(BUF_PARAMS(data, pre_save), buf_size + 5); if (!data->pre_save_buf) { - perror("custom mutator realloc"); - free(data); + perror("custom mutator realloc failed."); return -1; } @@ -164,11 +168,6 @@ size_t afl_custom_pre_save(my_mutator_t *data, uint8_t *buf, size_t buf_size, } -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 * the initial buffer. It should return the amount of iteration steps possible @@ -193,20 +192,20 @@ static int cur_step; int 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; + data->trim_buf = buf; + data->trim_buf_size = buf_size; - return trimmming_steps; + 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 @@ -216,19 +215,18 @@ 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. + * @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; + size_t ret = data->trim_buf_size - 1; - // External mutator should allocate memory for `out_buf` - *out_buf = malloc(*out_buf_size); + *out_buf = maybe_grow(BUF_PARAMS(data, trim_out), ret); // Remove the last byte of the trimming input - memcpy(*out_buf, trim_buf, *out_buf_size); + memcpy(*out_buf, data->trim_buf, ret); } @@ -248,12 +246,12 @@ int 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; } @@ -264,26 +262,33 @@ 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. * @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); + **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; @@ -346,6 +351,10 @@ 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->havoc_buf); + free(data->data_buf); + free(data->fuzz_buf); + free(data->trim_out_buf); free(data); } diff --git a/examples/post_library/post_library.so.c b/examples/post_library/post_library.so.c index 5d2685cd..735aae9b 100644 --- a/examples/post_library/post_library.so.c +++ b/examples/post_library/post_library.so.c @@ -3,6 +3,7 @@ -------------------------------------------------- Originally written by Michal Zalewski + Edited by Dominik Maier, 2020 Copyright 2015 Google Inc. All rights reserved. @@ -41,22 +42,23 @@ AFL will call the afl_postprocess() function for every mutated output buffer. From there, you have three choices: - 1) If you don't want to modify the test case, simply return the original - buffer pointer ('in_buf'). + 1) If you don't want to modify the test case, simply set `*out_buf = in_buf` + and return the original `len`. 2) If you want to skip this test case altogether and have AFL generate a - new one, return NULL. Use this sparingly - it's faster than running - the target program with patently useless inputs, but still wastes CPU - time. + new one, return 0 or set `*out_buf = NULL`. + Use this sparingly - it's faster than running the target program + with patently useless inputs, but still wastes CPU time. 3) If you want to modify the test case, allocate an appropriately-sized buffer, move the data into that buffer, make the necessary changes, and - then return the new pointer. You can update *len if necessary, too. + then return the new pointer as out_buf. Return an appropriate len + afterwards. Note that the buffer will *not* be freed for you. To avoid memory leaks, you need to free it or reuse it on subsequent calls (as shown below). - *** DO NOT MODIFY THE ORIGINAL 'in_buf' BUFFER. *** + *** Feel free to reuse the original 'in_buf' BUFFER and return it. *** Aight. The example below shows a simple postprocessor that tries to make sure that all input files start with "GIF89a". @@ -74,47 +76,83 @@ #define HEADER "GIF89a" -/* The actual postprocessor routine called by afl-fuzz: */ +typedef struct post_state { + + unsigned char *buf; + size_t size; + +} post_state_t; + +void *afl_postprocess_init(void *afl) { + + post_state_t *state = malloc(sizeof(post_state_t)); + if (!state) { -const unsigned char *afl_postprocess(const unsigned char *in_buf, - unsigned int * len) { + perror("malloc"); + return NULL; - static unsigned char *saved_buf; - unsigned char * new_buf; + } + + state->buf = calloc(sizeof(unsigned char), 4096); + if (!state->buf) { return NULL; } + + return state; + +} + +/* The actual postprocessor routine called by afl-fuzz: */ + +size_t afl_postprocess(post_state_t *data, unsigned char *in_buf, + unsigned int len, unsigned char **out_buf) { /* Skip execution altogether for buffers shorter than 6 bytes (just to - show how it's done). We can trust *len to be sane. */ + show how it's done). We can trust len to be sane. */ - if (*len < strlen(HEADER)) return NULL; + if (len < strlen(HEADER)) return 0; /* Do nothing for buffers that already start with the expected header. */ - if (!memcmp(in_buf, HEADER, strlen(HEADER))) return in_buf; + if (!memcmp(in_buf, HEADER, strlen(HEADER))) { + + *out_buf = in_buf; + return len; + + } /* Allocate memory for new buffer, reusing previous allocation if possible. */ - new_buf = realloc(saved_buf, *len); + *out_buf = realloc(data->buf, len); /* If we're out of memory, the most graceful thing to do is to return the original buffer and give up on modifying it. Let AFL handle OOM on its own later on. */ - if (!new_buf) return in_buf; - saved_buf = new_buf; + if (!*out_buf) { + + *out_buf = in_buf; + return len; + + } /* Copy the original data to the new location. */ - memcpy(new_buf, in_buf, *len); + memcpy(*out_buf, in_buf, len); /* Insert the new header. */ - memcpy(new_buf, HEADER, strlen(HEADER)); + memcpy(*out_buf, HEADER, strlen(HEADER)); - /* Return modified buffer. No need to update *len in this particular case, - as we're not changing it. */ + /* Return the new len. It hasn't changed, so it's just len. */ - return new_buf; + return len; } +/* Gets called afterwards */ +void afl_postprocess_deinit(post_state_t *data) { + + free(data->buf); + free(data); + +} diff --git a/examples/post_library/post_library_png.so.c b/examples/post_library/post_library_png.so.c index 60ab318f..8597c88c 100644 --- a/examples/post_library/post_library_png.so.c +++ b/examples/post_library/post_library_png.so.c @@ -5,6 +5,7 @@ Originally written by Michal Zalewski Copyright 2015 Google Inc. All rights reserved. + Adapted to the new API, 2020 by Dominik Maier Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. @@ -35,11 +36,32 @@ #define UP4K(_i) ((((_i) >> 12) + 1) << 12) -const unsigned char *afl_postprocess(const unsigned char *in_buf, - unsigned int * len) { +typedef struct post_state { - static unsigned char *saved_buf; - static unsigned int saved_len; + unsigned char *buf; + size_t size; + +} post_state_t; + +void *afl_postprocess_init(void *afl) { + + post_state_t *state = malloc(sizeof(post_state_t)); + if (!state) { + + perror("malloc"); + return NULL; + + } + + state->buf = calloc(sizeof(unsigned char), 4096); + if (!state->buf) { return NULL; } + + return state; + +} + +size_t afl_postprocess(post_state_t *data, const unsigned char *in_buf, + unsigned int len, const unsigned char **out_buf) { unsigned char *new_buf = (unsigned char *)in_buf; unsigned int pos = 8; @@ -47,12 +69,17 @@ const unsigned char *afl_postprocess(const unsigned char *in_buf, /* Don't do anything if there's not enough room for the PNG header (8 bytes). */ - if (*len < 8) return in_buf; + if (len < 8) { + + *out_buf = in_buf; + return len; + + } /* Minimum size of a zero-length PNG chunk is 12 bytes; if we don't have that, we can bail out. */ - while (pos + 12 <= *len) { + while (pos + 12 <= len) { unsigned int chunk_len, real_cksum, file_cksum; @@ -62,7 +89,7 @@ const unsigned char *afl_postprocess(const unsigned char *in_buf, /* Bail out if chunk size is too big or goes past EOF. */ - if (chunk_len > 1024 * 1024 || pos + 12 + chunk_len > *len) break; + if (chunk_len > 1024 * 1024 || pos + 12 + chunk_len > len) break; /* Chunk checksum is calculated for chunk ID (dword) and the actual payload. */ @@ -82,17 +109,23 @@ const unsigned char *afl_postprocess(const unsigned char *in_buf, if (new_buf == in_buf) { - if (*len <= saved_len) { + if (len <= data->size) { - new_buf = saved_buf; + new_buf = data->buf; } else { - new_buf = realloc(saved_buf, UP4K(*len)); - if (!new_buf) return in_buf; - saved_buf = new_buf; - saved_len = UP4K(*len); - memcpy(new_buf, in_buf, *len); + new_buf = realloc(data->buf, UP4K(len)); + if (!new_buf) { + + *out_buf = in_buf; + return len; + + } + + data->buf = new_buf; + data->size = UP4K(len); + memcpy(new_buf, in_buf, len); } @@ -108,7 +141,15 @@ const unsigned char *afl_postprocess(const unsigned char *in_buf, } - return new_buf; + *out_buf = new_buf; + return len; } +/* Gets called afterwards */ +void afl_postprocess_deinit(post_state_t *data) { + + free(data->buf); + free(data); + +} |