python mutator examples added

python_mutators/README

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+These are example and helper files for the AFL_PYTHON_MODULE feature.
+See docs/python_mutators.txt for more information
+
+
+example.py	- this is the template you can use, the functions are there
+		  but they are empty
+
+simple-chunk-replace.py - this is a simple example where chunks are replaced
+
+common.py 	- this can be used for common functions and helpers.
+		  the examples do not use this though. But you can :)

python_mutators/common.py

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+#!/usr/bin/env python
+# encoding: utf-8
+'''
+Module containing functions shared between multiple AFL modules
+
+@author:     Christian Holler (:decoder)
+
+@license:
+
+This Source Code Form is subject to the terms of the Mozilla Public
+License, v. 2.0. If a copy of the MPL was not distributed with this
+file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+@contact:    choller@mozilla.com
+'''
+
+from __future__ import print_function
+import random
+import os
+import re
+
+def randel(l):
+    if not l:
+        return None
+    return l[random.randint(0,len(l)-1)]
+
+def randel_pop(l):
+    if not l:
+        return None
+    return l.pop(random.randint(0,len(l)-1))
+
+def write_exc_example(data, exc):
+    exc_name = re.sub(r'[^a-zA-Z0-9]', '_', repr(exc))
+    
+    if not os.path.exists(exc_name):
+        with open(exc_name, 'w') as f:
+            f.write(data)    

python_mutators/example.py

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+#!/usr/bin/env python
+# encoding: utf-8
+'''
+Example Python Module for AFLFuzz
+
+@author:     Christian Holler (:decoder)
+
+@license:
+
+This Source Code Form is subject to the terms of the Mozilla Public
+License, v. 2.0. If a copy of the MPL was not distributed with this
+file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+@contact:    choller@mozilla.com
+'''
+
+import random
+
+def init(seed):
+    '''
+    Called once when AFLFuzz starts up. Used to seed our RNG.
+    
+    @type seed: int
+    @param seed: A 32-bit random value
+    '''
+    random.seed(seed)
+    return 0
+
+def fuzz(buf, add_buf):
+    '''
+    Called per fuzzing iteration.
+    
+    @type buf: bytearray
+    @param buf: The buffer that should be mutated.
+    
+    @type add_buf: bytearray
+    @param add_buf: A second buffer that can be used as mutation source.
+    
+    @rtype: bytearray
+    @return: A new bytearray containing the mutated data
+    '''
+    ret = bytearray(buf)
+    # Do something interesting with ret
+
+    return ret
+
+# Uncomment and implement the following methods if you want to use a custom
+# trimming algorithm. See also the documentation for a better API description.
+
+# def init_trim(buf):
+#     '''
+#     Called per trimming iteration.
+#     
+#     @type buf: bytearray
+#     @param buf: The buffer that should be trimmed.
+#     
+#     @rtype: int
+#     @return: The maximum number of trimming steps.
+#     '''
+#     global ...
+#     
+#     # Initialize global variables
+#     
+#     # Figure out how many trimming steps are possible.
+#     # If this is not possible for your trimming, you can
+#     # return 1 instead and always return 0 in post_trim
+#     # until you are done (then you return 1).
+#         
+#     return steps
+# 
+# def trim():
+#     '''
+#     Called per trimming iteration.
+# 
+#     @rtype: bytearray
+#     @return: A new bytearray containing the trimmed data.
+#     '''
+#     global ...
+#     
+#     # Implement the actual trimming here
+#     
+#     return bytearray(...)
+# 
+# def post_trim(success):
+#     '''
+#     Called after each trimming operation.
+#     
+#     @type success: bool
+#     @param success: Indicates if the last trim operation was successful.
+#     
+#     @rtype: int
+#     @return: The next trim index (0 to max number of steps) where max
+#              number of steps indicates the trimming is done.
+#     '''
+#     global ...
+# 
+#     if not success:
+#         # Restore last known successful input, determine next index
+#     else:
+#         # Just determine the next index, based on what was successfully
+#         # removed in the last step
+#     
+#     return next_index

python_mutators/simple-chunk-replace.py

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+#!/usr/bin/env python
+# encoding: utf-8
+'''
+Simple Chunk Cross-Over Replacement Module for AFLFuzz
+
+@author:     Christian Holler (:decoder)
+
+@license:
+
+This Source Code Form is subject to the terms of the Mozilla Public
+License, v. 2.0. If a copy of the MPL was not distributed with this
+file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+@contact:    choller@mozilla.com
+'''
+
+import random
+
+def init(seed):
+    '''
+    Called once when AFLFuzz starts up. Used to seed our RNG.
+    
+    @type seed: int
+    @param seed: A 32-bit random value
+    '''
+    # Seed our RNG
+    random.seed(seed)
+    return 0
+
+def fuzz(buf, add_buf):
+    '''
+    Called per fuzzing iteration.
+    
+    @type buf: bytearray
+    @param buf: The buffer that should be mutated.
+    
+    @type add_buf: bytearray
+    @param add_buf: A second buffer that can be used as mutation source.
+    
+    @rtype: bytearray
+    @return: A new bytearray containing the mutated data
+    '''
+    # Make a copy of our input buffer for returning
+    ret = bytearray(buf)
+
+    # Take a random fragment length between 2 and 32 (or less if add_buf is shorter)
+    fragment_len = random.randint(1, min(len(add_buf), 32))
+    
+    # Determine a random source index where to take the data chunk from
+    rand_src_idx = random.randint(0, len(add_buf) - fragment_len)
+    
+    # Determine a random destination index where to put the data chunk
+    rand_dst_idx = random.randint(0, len(buf))
+
+    # Make the chunk replacement
+    ret[rand_dst_idx:rand_dst_idx + fragment_len] = add_buf[rand_src_idx:rand_src_idx + fragment_len]
+
+    # Return data
+    return ret