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qemu-e2k/tests/image-fuzzer/qcow2/layout.py
Maria Kustova 1e8fd8d44d layout: Add generators for refcount table and blocks 
Refcount structures are placed in clusters randomly selected from all
unallocated host clusters.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Maria Kustova <maria.k@catit.be>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 7e2f38608db6fba2da53997390b19400d445c45d.1408450493.git.maria.k@catit.be
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-09-22 11:39:37 +01:00

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