613 lines
26 KiB
Python
613 lines
26 KiB
Python
# Generator of fuzzed qcow2 images
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#
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# Copyright (C) 2014 Maria Kustova <maria.k@catit.be>
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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#
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import random
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import struct
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import fuzz
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from math import ceil
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from os import urandom
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from itertools import chain
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MAX_IMAGE_SIZE = 10 * (1 << 20)
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# Standard sizes
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UINT32_S = 4
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UINT64_S = 8
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class Field(object):
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"""Atomic image element (field).
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The class represents an image field as quadruple of a data format
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of value necessary for its packing to binary form, an offset from
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the beginning of the image, a value and a name.
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The field can be iterated as a list [format, offset, value, name].
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"""
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__slots__ = ('fmt', 'offset', 'value', 'name')
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def __init__(self, fmt, offset, val, name):
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self.fmt = fmt
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self.offset = offset
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self.value = val
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self.name = name
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def __iter__(self):
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return iter([self.fmt, self.offset, self.value, self.name])
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def __repr__(self):
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return "Field(fmt='%s', offset=%d, value=%s, name=%s)" % \
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(self.fmt, self.offset, str(self.value), self.name)
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class FieldsList(object):
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"""List of fields.
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The class allows access to a field in the list by its name.
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"""
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def __init__(self, meta_data=None):
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if meta_data is None:
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self.data = []
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else:
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self.data = [Field(*f)
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for f in meta_data]
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def __getitem__(self, name):
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return [x for x in self.data if x.name == name]
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def __iter__(self):
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return iter(self.data)
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def __len__(self):
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return len(self.data)
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class Image(object):
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""" Qcow2 image object.
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This class allows to create qcow2 images with random valid structures and
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values, fuzz them via external qcow2.fuzz module and write the result to
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a file.
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"""
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def __init__(self, backing_file_name=None):
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"""Create a random valid qcow2 image with the correct header and stored
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backing file name.
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"""
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cluster_bits, self.image_size = self._size_params()
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self.cluster_size = 1 << cluster_bits
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self.header = FieldsList()
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self.backing_file_name = FieldsList()
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self.backing_file_format = FieldsList()
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self.feature_name_table = FieldsList()
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self.end_of_extension_area = FieldsList()
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self.l2_tables = FieldsList()
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self.l1_table = FieldsList()
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self.refcount_table = FieldsList()
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self.refcount_blocks = FieldsList()
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self.ext_offset = 0
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self.create_header(cluster_bits, backing_file_name)
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self.set_backing_file_name(backing_file_name)
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self.data_clusters = self._alloc_data(self.image_size,
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self.cluster_size)
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# Percentage of fields will be fuzzed
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self.bias = random.uniform(0.2, 0.5)
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def __iter__(self):
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return chain(self.header, self.backing_file_format,
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self.feature_name_table, self.end_of_extension_area,
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self.backing_file_name, self.l1_table, self.l2_tables,
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self.refcount_table, self.refcount_blocks)
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def create_header(self, cluster_bits, backing_file_name=None):
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"""Generate a random valid header."""
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meta_header = [
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['>4s', 0, "QFI\xfb", 'magic'],
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['>I', 4, random.randint(2, 3), 'version'],
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['>Q', 8, 0, 'backing_file_offset'],
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['>I', 16, 0, 'backing_file_size'],
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['>I', 20, cluster_bits, 'cluster_bits'],
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['>Q', 24, self.image_size, 'size'],
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['>I', 32, 0, 'crypt_method'],
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['>I', 36, 0, 'l1_size'],
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['>Q', 40, 0, 'l1_table_offset'],
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['>Q', 48, 0, 'refcount_table_offset'],
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['>I', 56, 0, 'refcount_table_clusters'],
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['>I', 60, 0, 'nb_snapshots'],
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['>Q', 64, 0, 'snapshots_offset'],
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['>Q', 72, 0, 'incompatible_features'],
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['>Q', 80, 0, 'compatible_features'],
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['>Q', 88, 0, 'autoclear_features'],
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# Only refcount_order = 4 is supported by current (07.2014)
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# implementation of QEMU
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['>I', 96, 4, 'refcount_order'],
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['>I', 100, 0, 'header_length']
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]
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self.header = FieldsList(meta_header)
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if self.header['version'][0].value == 2:
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self.header['header_length'][0].value = 72
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else:
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self.header['incompatible_features'][0].value = \
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random.getrandbits(2)
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self.header['compatible_features'][0].value = random.getrandbits(1)
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self.header['header_length'][0].value = 104
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# Extensions start at the header last field offset and the field size
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self.ext_offset = struct.calcsize(
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self.header['header_length'][0].fmt) + \
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self.header['header_length'][0].offset
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end_of_extension_area_len = 2 * UINT32_S
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free_space = self.cluster_size - self.ext_offset - \
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end_of_extension_area_len
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# If the backing file name specified and there is enough space for it
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# in the first cluster, then it's placed in the very end of the first
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# cluster.
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if (backing_file_name is not None) and \
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(free_space >= len(backing_file_name)):
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self.header['backing_file_size'][0].value = len(backing_file_name)
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self.header['backing_file_offset'][0].value = \
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self.cluster_size - len(backing_file_name)
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def set_backing_file_name(self, backing_file_name=None):
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"""Add the name of the backing file at the offset specified
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in the header.
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"""
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if (backing_file_name is not None) and \
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(not self.header['backing_file_offset'][0].value == 0):
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data_len = len(backing_file_name)
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data_fmt = '>' + str(data_len) + 's'
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self.backing_file_name = FieldsList([
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[data_fmt, self.header['backing_file_offset'][0].value,
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backing_file_name, 'bf_name']
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])
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def set_backing_file_format(self, backing_file_fmt=None):
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"""Generate the header extension for the backing file format."""
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if backing_file_fmt is not None:
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# Calculation of the free space available in the first cluster
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end_of_extension_area_len = 2 * UINT32_S
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high_border = (self.header['backing_file_offset'][0].value or
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(self.cluster_size - 1)) - \
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end_of_extension_area_len
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free_space = high_border - self.ext_offset
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ext_size = 2 * UINT32_S + ((len(backing_file_fmt) + 7) & ~7)
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if free_space >= ext_size:
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ext_data_len = len(backing_file_fmt)
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ext_data_fmt = '>' + str(ext_data_len) + 's'
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ext_padding_len = 7 - (ext_data_len - 1) % 8
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self.backing_file_format = FieldsList([
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['>I', self.ext_offset, 0xE2792ACA, 'ext_magic'],
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['>I', self.ext_offset + UINT32_S, ext_data_len,
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'ext_length'],
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[ext_data_fmt, self.ext_offset + UINT32_S * 2,
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backing_file_fmt, 'bf_format']
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])
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self.ext_offset = \
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struct.calcsize(
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self.backing_file_format['bf_format'][0].fmt) + \
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ext_padding_len + \
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self.backing_file_format['bf_format'][0].offset
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def create_feature_name_table(self):
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"""Generate a random header extension for names of features used in
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the image.
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"""
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def gen_feat_ids():
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"""Return random feature type and feature bit."""
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return (random.randint(0, 2), random.randint(0, 63))
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end_of_extension_area_len = 2 * UINT32_S
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high_border = (self.header['backing_file_offset'][0].value or
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(self.cluster_size - 1)) - \
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end_of_extension_area_len
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free_space = high_border - self.ext_offset
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# Sum of sizes of 'magic' and 'length' header extension fields
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ext_header_len = 2 * UINT32_S
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fnt_entry_size = 6 * UINT64_S
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num_fnt_entries = min(10, (free_space - ext_header_len) /
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fnt_entry_size)
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if not num_fnt_entries == 0:
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feature_tables = []
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feature_ids = []
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inner_offset = self.ext_offset + ext_header_len
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feat_name = 'some cool feature'
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while len(feature_tables) < num_fnt_entries * 3:
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feat_type, feat_bit = gen_feat_ids()
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# Remove duplicates
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while (feat_type, feat_bit) in feature_ids:
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feat_type, feat_bit = gen_feat_ids()
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feature_ids.append((feat_type, feat_bit))
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feat_fmt = '>' + str(len(feat_name)) + 's'
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feature_tables += [['B', inner_offset,
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feat_type, 'feature_type'],
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['B', inner_offset + 1, feat_bit,
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'feature_bit_number'],
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[feat_fmt, inner_offset + 2,
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feat_name, 'feature_name']
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]
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inner_offset += fnt_entry_size
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# No padding for the extension is necessary, because
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# the extension length is multiple of 8
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self.feature_name_table = FieldsList([
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['>I', self.ext_offset, 0x6803f857, 'ext_magic'],
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# One feature table contains 3 fields and takes 48 bytes
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['>I', self.ext_offset + UINT32_S,
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len(feature_tables) / 3 * 48, 'ext_length']
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] + feature_tables)
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self.ext_offset = inner_offset
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def set_end_of_extension_area(self):
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"""Generate a mandatory header extension marking end of header
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extensions.
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"""
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self.end_of_extension_area = FieldsList([
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['>I', self.ext_offset, 0, 'ext_magic'],
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['>I', self.ext_offset + UINT32_S, 0, 'ext_length']
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])
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def create_l_structures(self):
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"""Generate random valid L1 and L2 tables."""
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def create_l2_entry(host, guest, l2_cluster):
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"""Generate one L2 entry."""
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offset = l2_cluster * self.cluster_size
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l2_size = self.cluster_size / UINT64_S
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entry_offset = offset + UINT64_S * (guest % l2_size)
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cluster_descriptor = host * self.cluster_size
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if not self.header['version'][0].value == 2:
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cluster_descriptor += random.randint(0, 1)
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# While snapshots are not supported, bit #63 = 1
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# Compressed clusters are not supported => bit #62 = 0
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entry_val = (1 << 63) + cluster_descriptor
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return ['>Q', entry_offset, entry_val, 'l2_entry']
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def create_l1_entry(l2_cluster, l1_offset, guest):
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"""Generate one L1 entry."""
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l2_size = self.cluster_size / UINT64_S
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entry_offset = l1_offset + UINT64_S * (guest / l2_size)
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# While snapshots are not supported bit #63 = 1
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entry_val = (1 << 63) + l2_cluster * self.cluster_size
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return ['>Q', entry_offset, entry_val, 'l1_entry']
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if len(self.data_clusters) == 0:
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# All metadata for an empty guest image needs 4 clusters:
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# header, rfc table, rfc block, L1 table.
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# Header takes cluster #0, other clusters ##1-3 can be used
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l1_offset = random.randint(1, 3) * self.cluster_size
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l1 = [['>Q', l1_offset, 0, 'l1_entry']]
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l2 = []
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else:
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meta_data = self._get_metadata()
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guest_clusters = random.sample(range(self.image_size /
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self.cluster_size),
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len(self.data_clusters))
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# Number of entries in a L1/L2 table
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l_size = self.cluster_size / UINT64_S
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# Number of clusters necessary for L1 table
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l1_size = int(ceil((max(guest_clusters) + 1) / float(l_size**2)))
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l1_start = self._get_adjacent_clusters(self.data_clusters |
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meta_data, l1_size)
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meta_data |= set(range(l1_start, l1_start + l1_size))
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l1_offset = l1_start * self.cluster_size
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# Indices of L2 tables
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l2_ids = []
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# Host clusters allocated for L2 tables
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l2_clusters = []
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# L1 entries
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l1 = []
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# L2 entries
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l2 = []
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for host, guest in zip(self.data_clusters, guest_clusters):
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l2_id = guest / l_size
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if l2_id not in l2_ids:
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l2_ids.append(l2_id)
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l2_clusters.append(self._get_adjacent_clusters(
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self.data_clusters | meta_data | set(l2_clusters),
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1))
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l1.append(create_l1_entry(l2_clusters[-1], l1_offset,
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guest))
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l2.append(create_l2_entry(host, guest,
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l2_clusters[l2_ids.index(l2_id)]))
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self.l2_tables = FieldsList(l2)
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self.l1_table = FieldsList(l1)
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self.header['l1_size'][0].value = int(ceil(UINT64_S * self.image_size /
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float(self.cluster_size**2)))
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self.header['l1_table_offset'][0].value = l1_offset
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def create_refcount_structures(self):
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"""Generate random refcount blocks and refcount table."""
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def allocate_rfc_blocks(data, size):
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"""Return indices of clusters allocated for refcount blocks."""
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cluster_ids = set()
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diff = block_ids = set([x / size for x in data])
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while len(diff) != 0:
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# Allocate all yet not allocated clusters
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new = self._get_available_clusters(data | cluster_ids,
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len(diff))
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# Indices of new refcount blocks necessary to cover clusters
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# in 'new'
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diff = set([x / size for x in new]) - block_ids
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cluster_ids |= new
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block_ids |= diff
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return cluster_ids, block_ids
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def allocate_rfc_table(data, init_blocks, block_size):
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"""Return indices of clusters allocated for the refcount table
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and updated indices of clusters allocated for blocks and indices
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of blocks.
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"""
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blocks = set(init_blocks)
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clusters = set()
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# Number of entries in one cluster of the refcount table
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size = self.cluster_size / UINT64_S
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# Number of clusters necessary for the refcount table based on
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# the current number of refcount blocks
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table_size = int(ceil((max(blocks) + 1) / float(size)))
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# Index of the first cluster of the refcount table
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table_start = self._get_adjacent_clusters(data, table_size + 1)
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# Clusters allocated for the current length of the refcount table
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table_clusters = set(range(table_start, table_start + table_size))
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# Clusters allocated for the refcount table including
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# last optional one for potential l1 growth
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table_clusters_allocated = set(range(table_start, table_start +
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table_size + 1))
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# New refcount blocks necessary for clusters occupied by the
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# refcount table
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diff = set([c / block_size for c in table_clusters]) - blocks
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blocks |= diff
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while len(diff) != 0:
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# Allocate clusters for new refcount blocks
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new = self._get_available_clusters((data | clusters) |
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table_clusters_allocated,
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len(diff))
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# Indices of new refcount blocks necessary to cover
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# clusters in 'new'
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diff = set([x / block_size for x in new]) - blocks
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clusters |= new
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blocks |= diff
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# Check if the refcount table needs one more cluster
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if int(ceil((max(blocks) + 1) / float(size))) > table_size:
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new_block_id = (table_start + table_size) / block_size
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# Check if the additional table cluster needs
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# one more refcount block
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if new_block_id not in blocks:
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diff.add(new_block_id)
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table_clusters.add(table_start + table_size)
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table_size += 1
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return table_clusters, blocks, clusters
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def create_table_entry(table_offset, block_cluster, block_size,
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cluster):
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"""Generate a refcount table entry."""
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offset = table_offset + UINT64_S * (cluster / block_size)
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return ['>Q', offset, block_cluster * self.cluster_size,
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'refcount_table_entry']
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def create_block_entry(block_cluster, block_size, cluster):
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"""Generate a list of entries for the current block."""
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entry_size = self.cluster_size / block_size
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offset = block_cluster * self.cluster_size
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entry_offset = offset + entry_size * (cluster % block_size)
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# While snapshots are not supported all refcounts are set to 1
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return ['>H', entry_offset, 1, 'refcount_block_entry']
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# Size of a block entry in bits
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refcount_bits = 1 << self.header['refcount_order'][0].value
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# Number of refcount entries per refcount block
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# Convert self.cluster_size from bytes to bits to have the same
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# base for the numerator and denominator
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block_size = self.cluster_size * 8 / refcount_bits
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meta_data = self._get_metadata()
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if len(self.data_clusters) == 0:
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# All metadata for an empty guest image needs 4 clusters:
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# header, rfc table, rfc block, L1 table.
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# Header takes cluster #0, other clusters ##1-3 can be used
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block_clusters = set([random.choice(list(set(range(1, 4)) -
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meta_data))])
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block_ids = set([0])
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table_clusters = set([random.choice(list(set(range(1, 4)) -
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meta_data -
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block_clusters))])
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else:
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block_clusters, block_ids = \
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allocate_rfc_blocks(self.data_clusters |
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meta_data, block_size)
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table_clusters, block_ids, new_clusters = \
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allocate_rfc_table(self.data_clusters |
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meta_data |
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block_clusters,
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block_ids,
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block_size)
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block_clusters |= new_clusters
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meta_data |= block_clusters | table_clusters
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table_offset = min(table_clusters) * self.cluster_size
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block_id = None
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# Clusters allocated for refcount blocks
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block_clusters = list(block_clusters)
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# Indices of refcount blocks
|
|
block_ids = list(block_ids)
|
|
# Refcount table entries
|
|
rfc_table = []
|
|
# Refcount entries
|
|
rfc_blocks = []
|
|
|
|
for cluster in sorted(self.data_clusters | meta_data):
|
|
if cluster / block_size != block_id:
|
|
block_id = cluster / block_size
|
|
block_cluster = block_clusters[block_ids.index(block_id)]
|
|
rfc_table.append(create_table_entry(table_offset,
|
|
block_cluster,
|
|
block_size, cluster))
|
|
rfc_blocks.append(create_block_entry(block_cluster, block_size,
|
|
cluster))
|
|
self.refcount_table = FieldsList(rfc_table)
|
|
self.refcount_blocks = FieldsList(rfc_blocks)
|
|
|
|
self.header['refcount_table_offset'][0].value = table_offset
|
|
self.header['refcount_table_clusters'][0].value = len(table_clusters)
|
|
|
|
def fuzz(self, fields_to_fuzz=None):
|
|
"""Fuzz an image by corrupting values of a random subset of its fields.
|
|
|
|
Without parameters the method fuzzes an entire image.
|
|
|
|
If 'fields_to_fuzz' is specified then only fields in this list will be
|
|
fuzzed. 'fields_to_fuzz' can contain both individual fields and more
|
|
general image elements as a header or tables.
|
|
|
|
In the first case the field will be fuzzed always.
|
|
In the second a random subset of fields will be selected and fuzzed.
|
|
"""
|
|
def coin():
|
|
"""Return boolean value proportional to a portion of fields to be
|
|
fuzzed.
|
|
"""
|
|
return random.random() < self.bias
|
|
|
|
if fields_to_fuzz is None:
|
|
for field in self:
|
|
if coin():
|
|
field.value = getattr(fuzz, field.name)(field.value)
|
|
else:
|
|
for item in fields_to_fuzz:
|
|
if len(item) == 1:
|
|
for field in getattr(self, item[0]):
|
|
if coin():
|
|
field.value = getattr(fuzz,
|
|
field.name)(field.value)
|
|
else:
|
|
# If fields with the requested name were not generated
|
|
# getattr(self, item[0])[item[1]] returns an empty list
|
|
for field in getattr(self, item[0])[item[1]]:
|
|
field.value = getattr(fuzz, field.name)(field.value)
|
|
|
|
def write(self, filename):
|
|
"""Write an entire image to the file."""
|
|
image_file = open(filename, 'w')
|
|
for field in self:
|
|
image_file.seek(field.offset)
|
|
image_file.write(struct.pack(field.fmt, field.value))
|
|
|
|
for cluster in sorted(self.data_clusters):
|
|
image_file.seek(cluster * self.cluster_size)
|
|
image_file.write(urandom(self.cluster_size))
|
|
|
|
# Align the real image size to the cluster size
|
|
image_file.seek(0, 2)
|
|
size = image_file.tell()
|
|
rounded = (size + self.cluster_size - 1) & ~(self.cluster_size - 1)
|
|
if rounded > size:
|
|
image_file.seek(rounded - 1)
|
|
image_file.write("\0")
|
|
image_file.close()
|
|
|
|
@staticmethod
|
|
def _size_params():
|
|
"""Generate a random image size aligned to a random correct
|
|
cluster size.
|
|
"""
|
|
cluster_bits = random.randrange(9, 21)
|
|
cluster_size = 1 << cluster_bits
|
|
img_size = random.randrange(0, MAX_IMAGE_SIZE + 1, cluster_size)
|
|
return (cluster_bits, img_size)
|
|
|
|
@staticmethod
|
|
def _get_available_clusters(used, number):
|
|
"""Return a set of indices of not allocated clusters.
|
|
|
|
'used' contains indices of currently allocated clusters.
|
|
All clusters that cannot be allocated between 'used' clusters will have
|
|
indices appended to the end of 'used'.
|
|
"""
|
|
append_id = max(used) + 1
|
|
free = set(range(1, append_id)) - used
|
|
if len(free) >= number:
|
|
return set(random.sample(free, number))
|
|
else:
|
|
return free | set(range(append_id, append_id + number - len(free)))
|
|
|
|
@staticmethod
|
|
def _get_adjacent_clusters(used, size):
|
|
"""Return an index of the first cluster in the sequence of free ones.
|
|
|
|
'used' contains indices of currently allocated clusters. 'size' is the
|
|
length of the sequence of free clusters.
|
|
If the sequence of 'size' is not available between 'used' clusters, its
|
|
first index will be append to the end of 'used'.
|
|
"""
|
|
def get_cluster_id(lst, length):
|
|
"""Return the first index of the sequence of the specified length
|
|
or None if the sequence cannot be inserted in the list.
|
|
"""
|
|
if len(lst) != 0:
|
|
pairs = []
|
|
pair = (lst[0], 1)
|
|
for i in range(1, len(lst)):
|
|
if lst[i] == lst[i-1] + 1:
|
|
pair = (lst[i], pair[1] + 1)
|
|
else:
|
|
pairs.append(pair)
|
|
pair = (lst[i], 1)
|
|
pairs.append(pair)
|
|
random.shuffle(pairs)
|
|
for x, s in pairs:
|
|
if s >= length:
|
|
return x - length + 1
|
|
return None
|
|
|
|
append_id = max(used) + 1
|
|
free = list(set(range(1, append_id)) - used)
|
|
idx = get_cluster_id(free, size)
|
|
if idx is None:
|
|
return append_id
|
|
else:
|
|
return idx
|
|
|
|
@staticmethod
|
|
def _alloc_data(img_size, cluster_size):
|
|
"""Return a set of random indices of clusters allocated for guest data.
|
|
"""
|
|
num_of_cls = img_size/cluster_size
|
|
return set(random.sample(range(1, num_of_cls + 1),
|
|
random.randint(0, num_of_cls)))
|
|
|
|
def _get_metadata(self):
|
|
"""Return indices of clusters allocated for image metadata."""
|
|
ids = set()
|
|
for x in self:
|
|
ids.add(x.offset/self.cluster_size)
|
|
return ids
|
|
|
|
|
|
def create_image(test_img_path, backing_file_name=None, backing_file_fmt=None,
|
|
fields_to_fuzz=None):
|
|
"""Create a fuzzed image and write it to the specified file."""
|
|
image = Image(backing_file_name)
|
|
image.set_backing_file_format(backing_file_fmt)
|
|
image.create_feature_name_table()
|
|
image.set_end_of_extension_area()
|
|
image.create_l_structures()
|
|
image.create_refcount_structures()
|
|
image.fuzz(fields_to_fuzz)
|
|
image.write(test_img_path)
|
|
return image.image_size
|