more custom mutator remodelling

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
 

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;
+  uint8_t *trim_buf;
-  u8 *   pre_save_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,
+size_t afl_custom_fuzz(my_mutator_t *data, uint8_t *buf, size_t buf_size,
-                       uint8_t *add_buf,
+                       u8 **out_buf, uint8_t *add_buf,
-                       size_t   add_buf_size,  // add_buf can be NULL
+                       size_t add_buf_size,  // add_buf can be NULL
-                       size_t   max_size) {
+                       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) {
 
-  uint8_t *mutated_out = *buf;
+    perror("custom mutator allocation (maybe_grow)");
+    return -1;           /* 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);
@@ -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");
+      perror("custom mutator realloc failed.");
-      free(data);
       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;
+  data->cur_step = 0;
-  trim_buf = buf;
+  data->trim_buf = buf;
-  trim_buf_size = buf_size;
+  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
+ *     External library should allocate memory for out_buf.
- *     the memory after saving the test case.
+ *     AFL++ will not release the memory after saving the test case.
- * @param[out] out_buf_size Pointer to the size of the trimmed 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 afl_custom_trim(my_mutator_t *data, uint8_t **out_buf) {
-                     size_t *out_buf_size) {
 
-  *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 = maybe_grow(BUF_PARAMS(data, trim_out), ret);
-  *out_buf = malloc(*out_buf_size);
   // 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;
+    ++data->cur_step;
-    return 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 afl_custom_havoc_mutation(my_mutator_t *data, u8 *buf, size_t buf_size,
-                                 size_t buf_size, size_t max_size) {
+                                 u8 **out_buf, size_t max_size) {
 
   if (buf_size == 0) {
 
-    *buf = realloc(*buf, 1);
+    *out_buf = maybe_grow(BUF_PARAMS(data, havoc), 1);
-    **buf = rand() % 256;
+    **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);
 
 }

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
+   1) If you don't want to modify the test case, simply set `*out_buf = in_buf`
-      buffer pointer ('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
+      new one, return 0 or set `*out_buf = NULL`.
-      the target program with patently useless inputs, but still wastes CPU
+      Use this sparingly - it's faster than running the target program
-      time.
+      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"
 
+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) {
+
+    perror("malloc");
+    return NULL;
+
+  }
+
+  state->buf = calloc(sizeof(unsigned char), 4096);
+  if (!state->buf) { return NULL; }
+
+  return state;
+
+}
+
 /* The actual postprocessor routine called by afl-fuzz: */
 
-const unsigned char *afl_postprocess(const unsigned char *in_buf,
+size_t afl_postprocess(post_state_t *data, unsigned char *in_buf,
-                                     unsigned int *       len) {
+                       unsigned int len, unsigned char **out_buf) {
-
-  static unsigned char *saved_buf;
-  unsigned char *       new_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;
+  if (!*out_buf) {
-  saved_buf = new_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,
+  /* Return the new len. It hasn't changed, so it's just len. */
-     as we're not changing it. */
 
-  return new_buf;
+  return len;
 
 }
 
+/* Gets called afterwards */
+void afl_postprocess_deinit(post_state_t *data) {
+
+  free(data->buf);
+  free(data);
+
+}

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,
+typedef struct post_state {
-                                     unsigned int *       len) {
 
-  static unsigned char *saved_buf;
+  unsigned char *buf;
-  static unsigned int   saved_len;
+  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));
+          new_buf = realloc(data->buf, UP4K(len));
-          if (!new_buf) return in_buf;
+          if (!new_buf) {
-          saved_buf = new_buf;
+
-          saved_len = UP4K(*len);
+            *out_buf = in_buf;
-          memcpy(new_buf, in_buf, *len);
+            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);
+
+}

include/afl-fuzz.h

@@ -293,9 +293,18 @@ typedef struct py_mutator {
   void *    afl_state;
   void *    py_data;
 
+  u8 *   fuzz_buf;
+  size_t fuzz_size;
+
   u8 *   pre_save_buf;
   size_t pre_save_size;
 
+  u8 *   trim_buf;
+  size_t trim_size;
+
+  u8 *   havoc_buf;
+  size_t havoc_size;
+
 } py_mutator_t;
 
 #endif
@@ -544,7 +553,11 @@ typedef struct afl_state {
   struct extra_data *a_extras;          /* Automatically selected extras    */
   u32                a_extras_cnt;      /* Total number of tokens available */
 
-  u8 *(*post_handler)(u8 *buf, u32 *len);
+  /* afl_postprocess API */
+  void *(*post_init)(struct afl_state *afl);
+  size_t (*post_handler)(void *data, u8 *buf, u32 len, u8 **out_buf);
+  void *(*post_deinit)(void *data);
+  void *post_data;
 
   /* CmpLog */
 
@@ -643,10 +656,10 @@ struct custom_mutator {
    * @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 on error will abort exeuction.
    */
-  size_t (*afl_custom_fuzz)(void *data, u8 **buf, size_t buf_size, u8 *add_buf,
+  size_t (*afl_custom_fuzz)(void *data, u8 *buf, size_t buf_size, u8 **out_buf,
-                            size_t add_buf_size, size_t max_size);
+                            u8 *add_buf, size_t add_buf_size, size_t max_size);
 
   /**
    * A post-processing function to use right before AFL writes the test case to
@@ -704,9 +717,9 @@ struct custom_mutator {
    * @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
+   * @return the size of the trimmed test case
    */
-  void (*afl_custom_trim)(void *data, u8 **out_buf, size_t *out_buf_size);
+  size_t (*afl_custom_trim)(void *data, u8 **out_buf);
 
   /**
    * This method is called after each trim operation to inform you if your
@@ -728,16 +741,18 @@ struct custom_mutator {
    *
    * (Optional)
    *
-   * @param data pointer returned in afl_custom_init for this fuzz case
+   * @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 new buffer. It's legal to reuse *buf if it's <
+   * buf_size.
    * @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 (out_size).
    */
-  size_t (*afl_custom_havoc_mutation)(void *data, u8 **buf, size_t buf_size,
+  size_t (*afl_custom_havoc_mutation)(void *data, u8 *buf, size_t buf_size,
-                                      size_t max_size);
+                                      u8 **out_buf, size_t max_size);
 
   /**
    * Return the probability (in percentage) that afl_custom_havoc_mutation
@@ -803,8 +818,8 @@ void finalize_py_module(void *);
 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 *);
+size_t trim_py(void *, u8 **);
-size_t havoc_mutation_py(void *, u8 **, size_t, size_t);
+size_t havoc_mutation_py(void *, u8 *, size_t, u8 **, size_t);
 u8     havoc_mutation_probability_py(void *);
 u8     queue_get_py(void *, const u8 *);
 void   queue_new_entry_py(void *, const u8 *, const u8 *);

src/afl-fuzz-cmplog.c

@@ -527,8 +527,13 @@ u8 common_fuzz_cmplog_stuff(afl_state_t *afl, u8 *out_buf, u32 len) {
 
   if (afl->post_handler) {
 
-    out_buf = afl->post_handler(out_buf, &len);
+    u8 *post_buf = NULL;
-    if (!out_buf || !len) return 0;
+
+    size_t post_len =
+        afl->post_handler(afl->post_data, out_buf, len, &post_buf);
+    if (!post_buf || !post_len) return 0;
+    out_buf = post_buf;
+    len = post_len;
 
   }
 

src/afl-fuzz-globals.c

@@ -349,6 +349,8 @@ void read_afl_environment(afl_state_t *afl, char **envp) {
 
 void afl_state_deinit(afl_state_t *afl) {
 
+  if (afl->post_deinit) afl->post_deinit(afl->post_data);
+
   free(afl->out_buf);
   free(afl->out_scratch_buf);
   free(afl->eff_buf);

src/afl-fuzz-init.c

@@ -270,7 +270,9 @@ void setup_post(afl_state_t *afl) {
 
   void *dh;
   u8 *  fn = afl->afl_env.afl_post_library;
+  u8    tbuf[6];
   u32   tlen = 6;
+  strncpy(tbuf, "hello", tlen);
 
   if (!fn) return;
 
@@ -281,10 +283,20 @@ void setup_post(afl_state_t *afl) {
 
   afl->post_handler = dlsym(dh, "afl_postprocess");
   if (!afl->post_handler) FATAL("Symbol 'afl_postprocess' not found.");
+  afl->post_init = dlsym(dh, "afl_postprocess_init");
+  if (!afl->post_init) FATAL("Symbol 'afl_postprocess_init' not found.");
+  afl->post_deinit = dlsym(dh, "afl_postprocess_deinit");
+  if (!afl->post_deinit) FATAL("Symbol 'afl_postprocess_deinit' not found.");
 
   /* Do a quick test. It's better to segfault now than later =) */
 
-  afl->post_handler("hello", &tlen);
+  u8 *post_buf = NULL;
+  afl->post_data = afl->post_init(afl);
+  if (!afl->post_data) FATAL("Could not initialize post handler.");
+
+  size_t post_len = afl->post_handler(afl->post_data, tbuf, tlen, &post_buf);
+  if (!post_len || !post_buf)
+    SAYF("Empty return in test post handler for buf=\"hello\\0\".");
 
   OKF("Postprocessor installed successfully.");
 

src/afl-fuzz-mutators.c

@@ -7,6 +7,7 @@
    Now maintained by  Marc Heuse <mh@mh-sec.de>,
                         Heiko Eißfeldt <heiko.eissfeldt@hexco.de> and
                         Andrea Fioraldi <andreafioraldi@gmail.com>
+                        Dominik Maier <mail@dmnk.co>
 
    Copyright 2016, 2017 Google Inc. All rights reserved.
    Copyright 2019-2020 AFLplusplus Project. All rights reserved.
@@ -192,7 +193,8 @@ void load_custom_mutator(afl_state_t *afl, const char *fn) {
 
   /* Initialize the custom mutator */
   if (afl->mutator->afl_custom_init)
-    afl->mutator->data = afl->mutator->afl_custom_init(afl, rand_below(afl, 0xFFFFFFFF));
+    afl->mutator->data =
+        afl->mutator->afl_custom_init(afl, rand_below(afl, 0xFFFFFFFF));
 
 }
 
@@ -218,17 +220,18 @@ u8 trim_case_custom(afl_state_t *afl, struct queue_entry *q, u8 *in_buf) {
 
   while (afl->stage_cur < afl->stage_max) {
 
+    u8 *retbuf = NULL;
+
     sprintf(afl->stage_name_buf, "ptrim %s",
             u_stringify_int(val_buf, trim_exec));
 
     u32 cksum;
 
-    u8 *   retbuf = NULL;
+    size_t retlen = afl->mutator->afl_custom_trim(afl->mutator->data, &retbuf);
-    size_t retlen = 0;
 
-    afl->mutator->afl_custom_trim(afl->mutator->data, &retbuf, &retlen);
+    if (unlikely(retlen < 0 || !retbuf))
-
+      FATAL("custom_trim failed (ret %zd)", retlen);
-    if (retlen > orig_len)
+    else if (unlikely(retlen > orig_len))
       FATAL(
           "Trimmed data returned by custom mutator is larger than original "
           "data");
@@ -238,12 +241,7 @@ u8 trim_case_custom(afl_state_t *afl, struct queue_entry *q, u8 *in_buf) {
     fault = run_target(afl, afl->fsrv.exec_tmout);
     ++afl->trim_execs;
 
-    if (afl->stop_soon || fault == FAULT_ERROR) {
+    if (afl->stop_soon || fault == FAULT_ERROR) { goto abort_trimming; }
-
-      ck_free(retbuf);
-      goto abort_trimming;
-
-    }
 
     cksum = hash32(afl->fsrv.trace_bits, MAP_SIZE, HASH_CONST);
 
@@ -281,8 +279,6 @@ u8 trim_case_custom(afl_state_t *afl, struct queue_entry *q, u8 *in_buf) {
 
     }
 
-    ck_free(retbuf);
-
     /* Since this can be slow, update the screen every now and then. */
 
     if (!(trim_exec++ % afl->stats_update_freq)) show_stats(afl);

src/afl-fuzz-one.c

@@ -1612,15 +1612,20 @@ custom_mutator_stage:
     ck_read(fd, new_buf, target->len, target->fname);
     close(fd);
 
-    // TODO: clean up this mess.
+    u8 *mutated_buf = NULL;
+
     size_t mutated_size = afl->mutator->afl_custom_fuzz(
-        afl->mutator->data, &out_buf, len, new_buf, target->len, max_seed_size);
+        afl->mutator->data, out_buf, len, &mutated_buf, new_buf, target->len,
+        max_seed_size);
+
+    if (unlikely(mutated_size < 0))
+      FATAL("custom_fuzz returned %zd", mutated_size);
 
     if (mutated_size > len) afl->out_size = mutated_size;
 
     if (mutated_size > 0) {
 
-      if (common_fuzz_stuff(afl, out_buf, (u32)mutated_size)) {
+      if (common_fuzz_stuff(afl, mutated_buf, (u32)mutated_size)) {
 
         goto abandon_entry;
 
@@ -1726,8 +1731,22 @@ havoc_stage:
 
       if (stacked_custom && rand_below(afl, 100) < stacked_custom_prob) {
 
-        temp_len = afl->mutator->afl_custom_havoc_mutation(
+        u8 *   custom_havoc_buf = NULL;
-            afl->mutator->data, &out_buf, temp_len, MAX_FILE);
+        size_t new_len = afl->mutator->afl_custom_havoc_mutation(
+            afl->mutator->data, out_buf, temp_len, &custom_havoc_buf, MAX_FILE);
+        if (unlikely(new_len < 0))
+          FATAL("Error in custom_havoc (return %zd)", new_len);
+        if (likely(new_len > 0 && custom_havoc_buf)) {
+
+          temp_len = new_len;
+          if (out_buf != custom_havoc_buf) {
+
+            ck_maybe_grow(BUF_PARAMS(out), temp_len);
+            memcpy(out_buf, custom_havoc_buf, temp_len);
+
+          }
+
+        }
 
       }
 

src/afl-fuzz-python.c

@@ -35,15 +35,22 @@ static void *unsupported(afl_state_t *afl, unsigned int seed) {
 
 }
 
-size_t fuzz_py(void *py_mutator, u8 **buf, size_t buf_size, u8 *add_buf,
+/* sorry for this makro...
-               size_t add_buf_size, size_t max_size) {
+it just filles in `&py_mutator->something_buf, &py_mutator->something_size`. */
+#define BUF_PARAMS(name)                              \
+  (void **)&((py_mutator_t *)py_mutator)->name##_buf, \
+      &((py_mutator_t *)py_mutator)->name##_size
+
+size_t fuzz_py(void *py_mutator, u8 *buf, size_t buf_size, u8 **out_buf,
+               u8 *add_buf, size_t add_buf_size, size_t max_size) {
 
   size_t    mutated_size;
   PyObject *py_args, *py_value;
   py_args = PyTuple_New(3);
+  py_mutator_t *py = (py_mutator_t *)py_mutator;
 
   /* buf */
-  py_value = PyByteArray_FromStringAndSize(*buf, buf_size);
+  py_value = PyByteArray_FromStringAndSize(buf, buf_size);
   if (!py_value) {
 
     Py_DECREF(py_args);
@@ -79,17 +86,17 @@ size_t fuzz_py(void *py_mutator, u8 **buf, size_t buf_size, u8 *add_buf,
 
   PyTuple_SetItem(py_args, 2, py_value);
 
-  py_value = PyObject_CallObject(
+  py_value = PyObject_CallObject(py->py_functions[PY_FUNC_FUZZ], py_args);
-      ((py_mutator_t *)py_mutator)->py_functions[PY_FUNC_FUZZ], py_args);
 
   Py_DECREF(py_args);
 
   if (py_value != NULL) {
 
     mutated_size = PyByteArray_Size(py_value);
-    if (buf_size < mutated_size) *buf = ck_realloc(*buf, mutated_size);
 
-    memcpy(*buf, PyByteArray_AsString(py_value), mutated_size);
+    *out_buf = ck_maybe_grow(BUF_PARAMS(fuzz), mutated_size);
+
+    memcpy(*out_buf, PyByteArray_AsString(py_value), mutated_size);
     Py_DECREF(py_value);
     return mutated_size;
 
@@ -364,14 +371,8 @@ size_t pre_save_py(void *py_mutator, u8 *buf, size_t buf_size, u8 **out_buf) {
 
     py_out_buf_size = PyByteArray_Size(py_value);
 
-    if (py_out_buf_size > py->pre_save_size) {
+    ck_maybe_grow((void **)&py->pre_save_buf, &py->pre_save_size,
-
+                  py_out_buf_size);
-      /* Not enough space!
-      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(py->pre_save_buf, PyByteArray_AsString(py_value), py_out_buf_size);
     Py_DECREF(py_value);
@@ -465,9 +466,10 @@ u32 post_trim_py(void *py_mutator, u8 success) {
 
 }
 
-void trim_py(void *py_mutator, u8 **out_buf, size_t *out_buf_size) {
+size_t trim_py(void *py_mutator, u8 **out_buf) {
 
   PyObject *py_args, *py_value;
+  size_t    ret;
 
   py_args = PyTuple_New(0);
   py_value = PyObject_CallObject(
@@ -476,9 +478,9 @@ void trim_py(void *py_mutator, u8 **out_buf, size_t *out_buf_size) {
 
   if (py_value != NULL) {
 
-    *out_buf_size = PyByteArray_Size(py_value);
+    ret = PyByteArray_Size(py_value);
-    *out_buf = malloc(*out_buf_size);
+    *out_buf = ck_maybe_grow(BUF_PARAMS(trim), ret);
-    memcpy(*out_buf, PyByteArray_AsString(py_value), *out_buf_size);
+    memcpy(*out_buf, PyByteArray_AsString(py_value), ret);
     Py_DECREF(py_value);
 
   } else {
@@ -488,17 +490,19 @@ void trim_py(void *py_mutator, u8 **out_buf, size_t *out_buf_size) {
 
   }
 
+  return ret;
+
 }
 
-size_t havoc_mutation_py(void *py_mutator, u8 **buf, size_t buf_size,
+size_t havoc_mutation_py(void *py_mutator, u8 *buf, size_t buf_size,
-                         size_t max_size) {
+                         u8 **out_buf, size_t max_size) {
 
   size_t    mutated_size;
   PyObject *py_args, *py_value;
   py_args = PyTuple_New(2);
 
   /* buf */
-  py_value = PyByteArray_FromStringAndSize(*buf, buf_size);
+  py_value = PyByteArray_FromStringAndSize(buf, buf_size);
   if (!py_value) {
 
     Py_DECREF(py_args);
@@ -532,9 +536,19 @@ size_t havoc_mutation_py(void *py_mutator, u8 **buf, size_t buf_size,
   if (py_value != NULL) {
 
     mutated_size = PyByteArray_Size(py_value);
-    if (buf_size < mutated_size) *buf = ck_realloc(*buf, mutated_size);
+    if (mutated_size <= buf_size) {
 
-    memcpy(*buf, PyByteArray_AsString(py_value), mutated_size);
+      /* We reuse the input buf here. */
+      *out_buf = buf;
+
+    } else {
+
+      /* A new buf is needed... */
+      *out_buf = ck_maybe_grow(BUF_PARAMS(havoc), mutated_size);
+
+    }
+
+    memcpy(*out_buf, PyByteArray_AsString(py_value), mutated_size);
 
     Py_DECREF(py_value);
     return mutated_size;
@@ -680,5 +694,7 @@ void queue_new_entry_py(void *py_mutator, const u8 *filename_new_queue,
 
 }
 
+#undef BUF_PARAMS
+
 #endif                                                        /* USE_PYTHON */
 

src/afl-fuzz-run.c

@@ -741,8 +741,13 @@ u8 common_fuzz_stuff(afl_state_t *afl, u8 *out_buf, u32 len) {
 
   if (afl->post_handler) {
 
-    out_buf = afl->post_handler(out_buf, &len);
+    u8 *post_buf = NULL;
-    if (!out_buf || !len) return 0;
+
+    size_t post_len =
+        afl->post_handler(afl->post_data, out_buf, len, &post_buf);
+    if (!post_buf || !post_len) return 0;
+    out_buf = post_buf;
+    len = post_len;
 
   }