e303a369dc
When IPA gets a non-raw image, it performs an on-the-fly conversion using qemu-img convert, as well as running qemu-img frequently to get basic information about the image before validating it. Now, we ensure that before any qemu-img calls are made, that we have inspected the image for safety and pass through the detected format. If given a disk_format=raw image and image streaming is enabled (default), we retain the existing behavior of not inspecting it in any way and streaming it bit-perfect to the device. In this case, we never use qemu-based tools on the image at all. If given a disk_format=raw image and image streaming is disabled, this change fixes a bug where the image may have been converted if it was not actually raw in the first place. We now stream these bit-perfect to the device. Adds two config options: - [DEFAULT]/disable_deep_image_inspection, which can be set to "True" in order to disable all security features. Do not do this. - [DEFAULT]/permitted_image_formats, default raw,qcow2, for image types IPA should accept. Both of these configuration options are wired up to be set by the lookup data returned by Ironic at lookup time. This uses a image format inspection module imported from Nova; this inspector will eventually live in oslo.utils, at which point we'll migrate our usage of the inspector to it. Closes-Bug: #2071740 Change-Id: I5254b80717cb5a7f9084e3eff32a00b968f987b7
1045 lines
38 KiB
Python
1045 lines
38 KiB
Python
# Copyright 2020 Red Hat, Inc
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# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""
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This is a python implementation of virtual disk format inspection routines
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gathered from various public specification documents, as well as qemu disk
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driver code. It attempts to store and parse the minimum amount of data
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required, and in a streaming-friendly manner to collect metadata about
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complex-format images.
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This was imported from the Ironic fix. A copy of this inspector
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exists in multiple projects, including Ironic, Nova, and Cinder. Do not
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modify this version without modifying all versions.
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TODO(JayF): Remove this module, replace with oslo_utils version once released
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"""
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import struct
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from oslo_log import log as logging
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from oslo_utils import units
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LOG = logging.getLogger(__name__)
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def chunked_reader(fileobj, chunk_size=512):
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while True:
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chunk = fileobj.read(chunk_size)
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if not chunk:
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break
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yield chunk
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class CaptureRegion(object):
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"""Represents a region of a file we want to capture.
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A region of a file we want to capture requires a byte offset into
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the file and a length. This is expected to be used by a data
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processing loop, calling capture() with the most recently-read
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chunk. This class handles the task of grabbing the desired region
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of data across potentially multiple fractional and unaligned reads.
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:param offset: Byte offset into the file starting the region
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:param length: The length of the region
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"""
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def __init__(self, offset, length):
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self.offset = offset
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self.length = length
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self.data = b''
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@property
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def complete(self):
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"""Returns True when we have captured the desired data."""
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return self.length == len(self.data)
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def capture(self, chunk, current_position):
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"""Process a chunk of data.
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This should be called for each chunk in the read loop, at least
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until complete returns True.
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:param chunk: A chunk of bytes in the file
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:param current_position: The position of the file processed by the
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read loop so far. Note that this will be
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the position in the file *after* the chunk
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being presented.
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"""
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read_start = current_position - len(chunk)
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if (read_start <= self.offset <= current_position
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or self.offset <= read_start <= (self.offset + self.length)):
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if read_start < self.offset:
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lead_gap = self.offset - read_start
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else:
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lead_gap = 0
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self.data += chunk[lead_gap:]
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self.data = self.data[:self.length]
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class ImageFormatError(Exception):
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"""An unrecoverable image format error that aborts the process."""
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pass
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class TraceDisabled(object):
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"""A logger-like thing that swallows tracing when we do not want it."""
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def debug(self, *a, **k):
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pass
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info = debug
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warning = debug
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error = debug
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class FileInspector(object):
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"""A stream-based disk image inspector.
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This base class works on raw images and is subclassed for more
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complex types. It is to be presented with the file to be examined
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one chunk at a time, during read processing and will only store
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as much data as necessary to determine required attributes of
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the file.
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"""
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def __init__(self, tracing=False):
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self._total_count = 0
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# NOTE(danms): The logging in here is extremely verbose for a reason,
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# but should never really be enabled at that level at runtime. To
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# retain all that work and assist in future debug, we have a separate
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# debug flag that can be passed from a manual tool to turn it on.
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if tracing:
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self._log = logging.getLogger(str(self))
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else:
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self._log = TraceDisabled()
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self._capture_regions = {}
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def _capture(self, chunk, only=None):
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for name, region in self._capture_regions.items():
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if only and name not in only:
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continue
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if not region.complete:
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region.capture(chunk, self._total_count)
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def eat_chunk(self, chunk):
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"""Call this to present chunks of the file to the inspector."""
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pre_regions = set(self._capture_regions.keys())
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# Increment our position-in-file counter
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self._total_count += len(chunk)
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# Run through the regions we know of to see if they want this
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# data
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self._capture(chunk)
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# Let the format do some post-read processing of the stream
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self.post_process()
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# Check to see if the post-read processing added new regions
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# which may require the current chunk.
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new_regions = set(self._capture_regions.keys()) - pre_regions
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if new_regions:
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self._capture(chunk, only=new_regions)
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def post_process(self):
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"""Post-read hook to process what has been read so far.
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This will be called after each chunk is read and potentially captured
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by the defined regions. If any regions are defined by this call,
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those regions will be presented with the current chunk in case it
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is within one of the new regions.
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"""
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pass
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def region(self, name):
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"""Get a CaptureRegion by name."""
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return self._capture_regions[name]
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def new_region(self, name, region):
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"""Add a new CaptureRegion by name."""
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if self.has_region(name):
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# This is a bug, we tried to add the same region twice
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raise ImageFormatError('Inspector re-added region %s' % name)
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self._capture_regions[name] = region
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def has_region(self, name):
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"""Returns True if named region has been defined."""
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return name in self._capture_regions
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@property
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def format_match(self):
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"""Returns True if the file appears to be the expected format."""
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return True
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@property
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def virtual_size(self):
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"""Returns the virtual size of the disk image, or zero if unknown."""
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return self._total_count
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@property
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def actual_size(self):
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"""Returns the total size of the file, usually smaller than virtual_size.
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NOTE: this will only be accurate if the entire file is read and processed.
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""" # noqa
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return self._total_count
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@property
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def complete(self):
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"""Returns True if we have all the information needed."""
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return all(r.complete for r in self._capture_regions.values())
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def __str__(self):
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"""The string name of this file format."""
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return 'raw'
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@property
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def context_info(self):
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"""Return info on amount of data held in memory for auditing.
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This is a dict of region:sizeinbytes items that the inspector
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uses to examine the file.
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"""
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return {name: len(region.data) for name, region in
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self._capture_regions.items()}
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@classmethod
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def from_file(cls, filename):
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"""Read as much of a file as necessary to complete inspection.
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NOTE: Because we only read as much of the file as necessary, the
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actual_size property will not reflect the size of the file, but the
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amount of data we read before we satisfied the inspector.
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Raises ImageFormatError if we cannot parse the file.
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"""
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inspector = cls()
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with open(filename, 'rb') as f:
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for chunk in chunked_reader(f):
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inspector.eat_chunk(chunk)
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if inspector.complete:
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# No need to eat any more data
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break
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if not inspector.complete or not inspector.format_match:
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raise ImageFormatError('File is not in requested format')
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return inspector
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def safety_check(self):
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"""Perform some checks to determine if this file is safe.
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Returns True if safe, False otherwise. It may raise ImageFormatError
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if safety cannot be guaranteed because of parsing or other errors.
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"""
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return True
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# The qcow2 format consists of a big-endian 72-byte header, of which
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# only a small portion has information we care about:
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#
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# Dec Hex Name
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# 0 0x00 Magic 4-bytes 'QFI\xfb'
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# 4 0x04 Version (uint32_t, should always be 2 for modern files)
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# . . .
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# 8 0x08 Backing file offset (uint64_t)
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# 24 0x18 Size in bytes (unint64_t)
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# . . .
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# 72 0x48 Incompatible features bitfield (6 bytes)
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#
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# https://gitlab.com/qemu-project/qemu/-/blob/master/docs/interop/qcow2.txt
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class QcowInspector(FileInspector):
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"""QEMU QCOW2 Format
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This should only require about 32 bytes of the beginning of the file
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to determine the virtual size, and 104 bytes to perform the safety check.
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"""
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BF_OFFSET = 0x08
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BF_OFFSET_LEN = 8
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I_FEATURES = 0x48
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I_FEATURES_LEN = 8
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I_FEATURES_DATAFILE_BIT = 3
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I_FEATURES_MAX_BIT = 4
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def __init__(self, *a, **k):
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super(QcowInspector, self).__init__(*a, **k)
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self.new_region('header', CaptureRegion(0, 512))
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def _qcow_header_data(self):
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magic, version, bf_offset, bf_sz, cluster_bits, size = (
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struct.unpack('>4sIQIIQ', self.region('header').data[:32]))
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return magic, size
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@property
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def has_header(self):
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return self.region('header').complete
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@property
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def virtual_size(self):
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if not self.region('header').complete:
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return 0
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if not self.format_match:
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return 0
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magic, size = self._qcow_header_data()
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return size
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@property
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def format_match(self):
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if not self.region('header').complete:
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return False
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magic, size = self._qcow_header_data()
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return magic == b'QFI\xFB'
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@property
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def has_backing_file(self):
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if not self.region('header').complete:
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return None
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if not self.format_match:
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return False
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bf_offset_bytes = self.region('header').data[
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self.BF_OFFSET:self.BF_OFFSET + self.BF_OFFSET_LEN]
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# nonzero means "has a backing file"
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bf_offset, = struct.unpack('>Q', bf_offset_bytes)
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return bf_offset != 0
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@property
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def has_unknown_features(self):
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if not self.region('header').complete:
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return None
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if not self.format_match:
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return False
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i_features = self.region('header').data[
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self.I_FEATURES:self.I_FEATURES + self.I_FEATURES_LEN]
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# This is the maximum byte number we should expect any bits to be set
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max_byte = self.I_FEATURES_MAX_BIT // 8
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# The flag bytes are in big-endian ordering, so if we process
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# them in index-order, they're reversed
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for i, byte_num in enumerate(reversed(range(self.I_FEATURES_LEN))):
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if byte_num == max_byte:
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# If we're in the max-allowed byte, allow any bits less than
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# the maximum-known feature flag bit to be set
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allow_mask = ((1 << self.I_FEATURES_MAX_BIT) - 1)
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elif byte_num > max_byte:
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# If we're above the byte with the maximum known feature flag
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# bit, then we expect all zeroes
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allow_mask = 0x0
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else:
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# Any earlier-than-the-maximum byte can have any of the flag
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# bits set
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allow_mask = 0xFF
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if i_features[i] & ~allow_mask:
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LOG.warning('Found unknown feature bit in byte %i: %s/%s',
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byte_num, bin(i_features[byte_num] & ~allow_mask),
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bin(allow_mask))
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return True
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return False
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@property
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def has_data_file(self):
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if not self.region('header').complete:
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return None
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if not self.format_match:
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return False
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i_features = self.region('header').data[
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self.I_FEATURES:self.I_FEATURES + self.I_FEATURES_LEN]
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# First byte of bitfield, which is i_features[7]
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byte = self.I_FEATURES_LEN - 1 - self.I_FEATURES_DATAFILE_BIT // 8
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# Third bit of bitfield, which is 0x04
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bit = 1 << (self.I_FEATURES_DATAFILE_BIT - 1 % 8)
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return bool(i_features[byte] & bit)
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def __str__(self):
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return 'qcow2'
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def safety_check(self):
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return (not self.has_backing_file
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and not self.has_data_file
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and not self.has_unknown_features)
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class QEDInspector(FileInspector):
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def __init__(self, tracing=False):
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super().__init__(tracing)
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self.new_region('header', CaptureRegion(0, 512))
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@property
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def format_match(self):
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if not self.region('header').complete:
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return False
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return self.region('header').data.startswith(b'QED\x00')
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def safety_check(self):
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# QED format is not supported by anyone, but we want to detect it
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# and mark it as just always unsafe.
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return False
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# The VHD (or VPC as QEMU calls it) format consists of a big-endian
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# 512-byte "footer" at the beginning of the file with various
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# information, most of which does not matter to us:
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#
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# Dec Hex Name
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# 0 0x00 Magic string (8-bytes, always 'conectix')
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# 40 0x28 Disk size (uint64_t)
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#
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# https://github.com/qemu/qemu/blob/master/block/vpc.c
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class VHDInspector(FileInspector):
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"""Connectix/MS VPC VHD Format
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This should only require about 512 bytes of the beginning of the file
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to determine the virtual size.
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"""
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def __init__(self, *a, **k):
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super(VHDInspector, self).__init__(*a, **k)
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self.new_region('header', CaptureRegion(0, 512))
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@property
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def format_match(self):
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return self.region('header').data.startswith(b'conectix')
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@property
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def virtual_size(self):
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if not self.region('header').complete:
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return 0
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if not self.format_match:
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return 0
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return struct.unpack('>Q', self.region('header').data[40:48])[0]
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def __str__(self):
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return 'vhd'
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# The VHDX format consists of a complex dynamic little-endian
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# structure with multiple regions of metadata and data, linked by
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# offsets with in the file (and within regions), identified by MSFT
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# GUID strings. The header is a 320KiB structure, only a few pieces of
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# which we actually need to capture and interpret:
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#
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# Dec Hex Name
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# 0 0x00000 Identity (Technically 9-bytes, padded to 64KiB, the first
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# 8 bytes of which are 'vhdxfile')
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# 196608 0x30000 The Region table (64KiB of a 32-byte header, followed
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# by up to 2047 36-byte region table entry structures)
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#
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# The region table header includes two items we need to read and parse,
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# which are:
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#
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# 196608 0x30000 4-byte signature ('regi')
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# 196616 0x30008 Entry count (uint32-t)
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#
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# The region table entries follow the region table header immediately
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# and are identified by a 16-byte GUID, and provide an offset of the
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# start of that region. We care about the "metadata region", identified
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# by the METAREGION class variable. The region table entry is (offsets
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# from the beginning of the entry, since it could be in multiple places):
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#
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# 0 0x00000 16-byte MSFT GUID
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# 16 0x00010 Offset of the actual metadata region (uint64_t)
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#
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# When we find the METAREGION table entry, we need to grab that offset
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# and start examining the region structure at that point. That
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# consists of a metadata table of structures, which point to places in
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# the data in an unstructured space that follows. The header is
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# (offsets relative to the region start):
|
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#
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# 0 0x00000 8-byte signature ('metadata')
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# . . .
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# 16 0x00010 2-byte entry count (up to 2047 entries max)
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#
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# This header is followed by the specified number of metadata entry
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# structures, identified by GUID:
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#
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# 0 0x00000 16-byte MSFT GUID
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# 16 0x00010 4-byte offset (uint32_t, relative to the beginning of
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# the metadata region)
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#
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# We need to find the "Virtual Disk Size" metadata item, identified by
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# the GUID in the VIRTUAL_DISK_SIZE class variable, grab the offset,
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# add it to the offset of the metadata region, and examine that 8-byte
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# chunk of data that follows.
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#
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# The "Virtual Disk Size" is a naked uint64_t which contains the size
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# of the virtual disk, and is our ultimate target here.
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#
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# https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-vhdx/83e061f8-f6e2-4de1-91bd-5d518a43d477
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class VHDXInspector(FileInspector):
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"""MS VHDX Format
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This requires some complex parsing of the stream. The first 256KiB
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of the image is stored to get the header and region information,
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and then we capture the first metadata region to read those
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records, find the location of the virtual size data and parse
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it. This needs to store the metadata table entries up until the
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VDS record, which may consist of up to 2047 32-byte entries at
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max. Finally, it must store a chunk of data at the offset of the
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actual VDS uint64.
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"""
|
|
METAREGION = '8B7CA206-4790-4B9A-B8FE-575F050F886E'
|
|
VIRTUAL_DISK_SIZE = '2FA54224-CD1B-4876-B211-5DBED83BF4B8'
|
|
VHDX_METADATA_TABLE_MAX_SIZE = 32 * 2048 # From qemu
|
|
|
|
def __init__(self, *a, **k):
|
|
super(VHDXInspector, self).__init__(*a, **k)
|
|
self.new_region('ident', CaptureRegion(0, 32))
|
|
self.new_region('header', CaptureRegion(192 * 1024, 64 * 1024))
|
|
|
|
def post_process(self):
|
|
# After reading a chunk, we may have the following conditions:
|
|
#
|
|
# 1. We may have just completed the header region, and if so,
|
|
# we need to immediately read and calculate the location of
|
|
# the metadata region, as it may be starting in the same
|
|
# read we just did.
|
|
# 2. We may have just completed the metadata region, and if so,
|
|
# we need to immediately calculate the location of the
|
|
# "virtual disk size" record, as it may be starting in the
|
|
# same read we just did.
|
|
if self.region('header').complete and not self.has_region('metadata'):
|
|
region = self._find_meta_region()
|
|
if region:
|
|
self.new_region('metadata', region)
|
|
elif self.has_region('metadata') and not self.has_region('vds'):
|
|
region = self._find_meta_entry(self.VIRTUAL_DISK_SIZE)
|
|
if region:
|
|
self.new_region('vds', region)
|
|
|
|
@property
|
|
def format_match(self):
|
|
return self.region('ident').data.startswith(b'vhdxfile')
|
|
|
|
@staticmethod
|
|
def _guid(buf):
|
|
"""Format a MSFT GUID from the 16-byte input buffer."""
|
|
guid_format = '<IHHBBBBBBBB'
|
|
return '%08X-%04X-%04X-%02X%02X-%02X%02X%02X%02X%02X%02X' % (
|
|
struct.unpack(guid_format, buf))
|
|
|
|
def _find_meta_region(self):
|
|
# The region table entries start after a 16-byte table header
|
|
region_entry_first = 16
|
|
|
|
# Parse the region table header to find the number of regions
|
|
regi, cksum, count, reserved = struct.unpack(
|
|
'<IIII', self.region('header').data[:16])
|
|
if regi != 0x69676572:
|
|
raise ImageFormatError('Region signature not found at %x' % (
|
|
self.region('header').offset))
|
|
|
|
if count >= 2048:
|
|
raise ImageFormatError('Region count is %i (limit 2047)' % count)
|
|
|
|
# Process the regions until we find the metadata one; grab the
|
|
# offset and return
|
|
self._log.debug('Region entry first is %x', region_entry_first)
|
|
self._log.debug('Region entries %i', count)
|
|
meta_offset = 0
|
|
for i in range(0, count):
|
|
entry_start = region_entry_first + (i * 32)
|
|
entry_end = entry_start + 32
|
|
entry = self.region('header').data[entry_start:entry_end]
|
|
self._log.debug('Entry offset is %x', entry_start)
|
|
|
|
# GUID is the first 16 bytes
|
|
guid = self._guid(entry[:16])
|
|
if guid == self.METAREGION:
|
|
# This entry is the metadata region entry
|
|
meta_offset, meta_len, meta_req = struct.unpack(
|
|
'<QII', entry[16:])
|
|
self._log.debug('Meta entry %i specifies offset: %x',
|
|
i, meta_offset)
|
|
# NOTE(danms): The meta_len in the region descriptor is the
|
|
# entire size of the metadata table and data. This can be
|
|
# very large, so we should only capture the size required
|
|
# for the maximum length of the table, which is one 32-byte
|
|
# table header, plus up to 2047 32-byte entries.
|
|
meta_len = 2048 * 32
|
|
return CaptureRegion(meta_offset, meta_len)
|
|
|
|
self._log.warning('Did not find metadata region')
|
|
return None
|
|
|
|
def _find_meta_entry(self, desired_guid):
|
|
meta_buffer = self.region('metadata').data
|
|
if len(meta_buffer) < 32:
|
|
# Not enough data yet for full header
|
|
return None
|
|
|
|
# Make sure we found the metadata region by checking the signature
|
|
sig, reserved, count = struct.unpack('<8sHH', meta_buffer[:12])
|
|
if sig != b'metadata':
|
|
raise ImageFormatError(
|
|
'Invalid signature for metadata region: %r' % sig)
|
|
|
|
entries_size = 32 + (count * 32)
|
|
if len(meta_buffer) < entries_size:
|
|
# Not enough data yet for all metadata entries. This is not
|
|
# strictly necessary as we could process whatever we have until
|
|
# we find the V-D-S one, but there are only 2047 32-byte
|
|
# entries max (~64k).
|
|
return None
|
|
|
|
if count >= 2048:
|
|
raise ImageFormatError(
|
|
'Metadata item count is %i (limit 2047)' % count)
|
|
|
|
for i in range(0, count):
|
|
entry_offset = 32 + (i * 32)
|
|
guid = self._guid(meta_buffer[entry_offset:entry_offset + 16])
|
|
if guid == desired_guid:
|
|
# Found the item we are looking for by id.
|
|
# Stop our region from capturing
|
|
item_offset, item_length, _reserved = struct.unpack(
|
|
'<III',
|
|
meta_buffer[entry_offset + 16:entry_offset + 28])
|
|
item_length = min(item_length,
|
|
self.VHDX_METADATA_TABLE_MAX_SIZE)
|
|
self.region('metadata').length = len(meta_buffer)
|
|
self._log.debug('Found entry at offset %x', item_offset)
|
|
# Metadata item offset is from the beginning of the metadata
|
|
# region, not the file.
|
|
return CaptureRegion(
|
|
self.region('metadata').offset + item_offset,
|
|
item_length)
|
|
|
|
self._log.warning('Did not find guid %s', desired_guid)
|
|
return None
|
|
|
|
@property
|
|
def virtual_size(self):
|
|
# Until we have found the offset and have enough metadata buffered
|
|
# to read it, return "unknown"
|
|
if not self.has_region('vds') or not self.region('vds').complete:
|
|
return 0
|
|
|
|
size, = struct.unpack('<Q', self.region('vds').data)
|
|
return size
|
|
|
|
def __str__(self):
|
|
return 'vhdx'
|
|
|
|
|
|
# The VMDK format comes in a large number of variations, but the
|
|
# single-file 'monolithicSparse' version 4 one is mostly what we care
|
|
# about. It contains a 512-byte little-endian header, followed by a
|
|
# variable-length "descriptor" region of text. The header looks like:
|
|
#
|
|
# Dec Hex Name
|
|
# 0 0x00 4-byte magic string 'KDMV'
|
|
# 4 0x04 Version (uint32_t)
|
|
# 8 0x08 Flags (uint32_t, unused by us)
|
|
# 16 0x10 Number of 512 byte sectors in the disk (uint64_t)
|
|
# 24 0x18 Granularity (uint64_t, unused by us)
|
|
# 32 0x20 Descriptor offset in 512-byte sectors (uint64_t)
|
|
# 40 0x28 Descriptor size in 512-byte sectors (uint64_t)
|
|
#
|
|
# After we have the header, we need to find the descriptor region,
|
|
# which starts at the sector identified in the "descriptor offset"
|
|
# field, and is "descriptor size" 512-byte sectors long. Once we have
|
|
# that region, we need to parse it as text, looking for the
|
|
# createType=XXX line that specifies the mechanism by which the data
|
|
# extents are stored in this file. We only support the
|
|
# "monolithicSparse" format, so we just need to confirm that this file
|
|
# contains that specifier.
|
|
#
|
|
# https://www.vmware.com/app/vmdk/?src=vmdk
|
|
class VMDKInspector(FileInspector):
|
|
"""vmware VMDK format (monolithicSparse and streamOptimized variants only)
|
|
|
|
This needs to store the 512 byte header and the descriptor region
|
|
which should be just after that. The descriptor region is some
|
|
variable number of 512 byte sectors, but is just text defining the
|
|
layout of the disk.
|
|
"""
|
|
|
|
# The beginning and max size of the descriptor is also hardcoded in Qemu
|
|
# at 0x200 and 1MB - 1
|
|
DESC_OFFSET = 0x200
|
|
DESC_MAX_SIZE = (1 << 20) - 1
|
|
GD_AT_END = 0xffffffffffffffff
|
|
|
|
def __init__(self, *a, **k):
|
|
super(VMDKInspector, self).__init__(*a, **k)
|
|
self.new_region('header', CaptureRegion(0, 512))
|
|
|
|
def post_process(self):
|
|
# If we have just completed the header region, we need to calculate
|
|
# the location and length of the descriptor, which should immediately
|
|
# follow and may have been partially-read in this read.
|
|
if not self.region('header').complete:
|
|
return
|
|
|
|
(sig, ver, _flags, _sectors, _grain, desc_sec, desc_num,
|
|
_numGTEsperGT, _rgdOffset, gdOffset) = struct.unpack(
|
|
'<4sIIQQQQIQQ', self.region('header').data[:64])
|
|
|
|
if sig != b'KDMV':
|
|
raise ImageFormatError('Signature KDMV not found: %r' % sig)
|
|
|
|
if ver not in (1, 2, 3):
|
|
raise ImageFormatError('Unsupported format version %i' % ver)
|
|
|
|
if gdOffset == self.GD_AT_END:
|
|
# This means we have a footer, which takes precedence over the
|
|
# header, which we cannot support since we stream.
|
|
raise ImageFormatError('Unsupported VMDK footer')
|
|
|
|
# Since we parse both desc_sec and desc_num (the location of the
|
|
# VMDK's descriptor, expressed in 512 bytes sectors) we enforce a
|
|
# check on the bounds to create a reasonable CaptureRegion. This
|
|
# is similar to how it's done in qemu.
|
|
desc_offset = desc_sec * 512
|
|
desc_size = min(desc_num * 512, self.DESC_MAX_SIZE)
|
|
if desc_offset != self.DESC_OFFSET:
|
|
raise ImageFormatError("Wrong descriptor location")
|
|
|
|
if not self.has_region('descriptor'):
|
|
self.new_region('descriptor', CaptureRegion(
|
|
desc_offset, desc_size))
|
|
|
|
@property
|
|
def format_match(self):
|
|
return self.region('header').data.startswith(b'KDMV')
|
|
|
|
@property
|
|
def virtual_size(self):
|
|
if not self.has_region('descriptor'):
|
|
# Not enough data yet
|
|
return 0
|
|
|
|
descriptor_rgn = self.region('descriptor')
|
|
if not descriptor_rgn.complete:
|
|
# Not enough data yet
|
|
return 0
|
|
|
|
descriptor = descriptor_rgn.data
|
|
type_idx = descriptor.index(b'createType="') + len(b'createType="')
|
|
type_end = descriptor.find(b'"', type_idx)
|
|
# Make sure we don't grab and log a huge chunk of data in a
|
|
# maliciously-formatted descriptor region
|
|
if type_end - type_idx < 64:
|
|
vmdktype = descriptor[type_idx:type_end]
|
|
else:
|
|
vmdktype = b'formatnotfound'
|
|
if vmdktype not in (b'monolithicSparse', b'streamOptimized'):
|
|
LOG.warning('Unsupported VMDK format %s', vmdktype)
|
|
return 0
|
|
|
|
# If we have the descriptor, we definitely have the header
|
|
_sig, _ver, _flags, sectors, _grain, _desc_sec, _desc_num = (
|
|
struct.unpack('<IIIQQQQ', self.region('header').data[:44]))
|
|
|
|
return sectors * 512
|
|
|
|
def safety_check(self):
|
|
if (not self.has_region('descriptor')
|
|
or not self.region('descriptor').complete):
|
|
return False
|
|
|
|
try:
|
|
# Descriptor is padded to 512 bytes
|
|
desc_data = self.region('descriptor').data.rstrip(b'\x00')
|
|
# Descriptor is actually case-insensitive ASCII text
|
|
desc_text = desc_data.decode('ascii').lower()
|
|
except UnicodeDecodeError:
|
|
LOG.error('VMDK descriptor failed to decode as ASCII')
|
|
raise ImageFormatError('Invalid VMDK descriptor data')
|
|
|
|
extent_access = ('rw', 'rdonly', 'noaccess')
|
|
header_fields = []
|
|
extents = []
|
|
ddb = []
|
|
|
|
# NOTE(danms): Cautiously parse the VMDK descriptor. Each line must
|
|
# be something we understand, otherwise we refuse it.
|
|
for line in [x.strip() for x in desc_text.split('\n')]:
|
|
if line.startswith('#') or not line:
|
|
# Blank or comment lines are ignored
|
|
continue
|
|
elif line.startswith('ddb'):
|
|
# DDB lines are allowed (but not used by us)
|
|
ddb.append(line)
|
|
elif '=' in line and ' ' not in line.split('=')[0]:
|
|
# Header fields are a single word followed by an '=' and some
|
|
# value
|
|
header_fields.append(line)
|
|
elif line.split(' ')[0] in extent_access:
|
|
# Extent lines start with one of the three access modes
|
|
extents.append(line)
|
|
else:
|
|
# Anything else results in a rejection
|
|
LOG.error('Unsupported line %r in VMDK descriptor', line)
|
|
raise ImageFormatError('Invalid VMDK descriptor data')
|
|
|
|
# Check all the extent lines for concerning content
|
|
for extent_line in extents:
|
|
if '/' in extent_line:
|
|
LOG.error('Extent line %r contains unsafe characters',
|
|
extent_line)
|
|
return False
|
|
|
|
if not extents:
|
|
LOG.error('VMDK file specified no extents')
|
|
return False
|
|
|
|
return True
|
|
|
|
def __str__(self):
|
|
return 'vmdk'
|
|
|
|
|
|
# The VirtualBox VDI format consists of a 512-byte little-endian
|
|
# header, some of which we care about:
|
|
#
|
|
# Dec Hex Name
|
|
# 64 0x40 4-byte Magic (0xbeda107f)
|
|
# . . .
|
|
# 368 0x170 Size in bytes (uint64_t)
|
|
#
|
|
# https://github.com/qemu/qemu/blob/master/block/vdi.c
|
|
class VDIInspector(FileInspector):
|
|
"""VirtualBox VDI format
|
|
|
|
This only needs to store the first 512 bytes of the image.
|
|
"""
|
|
|
|
def __init__(self, *a, **k):
|
|
super(VDIInspector, self).__init__(*a, **k)
|
|
self.new_region('header', CaptureRegion(0, 512))
|
|
|
|
@property
|
|
def format_match(self):
|
|
if not self.region('header').complete:
|
|
return False
|
|
|
|
signature, = struct.unpack('<I', self.region('header').data[0x40:0x44])
|
|
return signature == 0xbeda107f
|
|
|
|
@property
|
|
def virtual_size(self):
|
|
if not self.region('header').complete:
|
|
return 0
|
|
if not self.format_match:
|
|
return 0
|
|
|
|
size, = struct.unpack('<Q', self.region('header').data[0x170:0x178])
|
|
return size
|
|
|
|
def __str__(self):
|
|
return 'vdi'
|
|
|
|
|
|
class ISOInspector(FileInspector):
|
|
"""ISO 9660 and UDF format
|
|
|
|
we need to check the first 32KB + descriptor size
|
|
to look for the ISO 9660 or UDF signature.
|
|
|
|
http://wiki.osdev.org/ISO_9660
|
|
http://wiki.osdev.org/UDF
|
|
mkisofs --help | grep udf
|
|
|
|
The Universal Disc Format or UDF is the filesystem used on DVDs and
|
|
Blu-Ray discs.UDF is an extension of ISO 9660 and shares the same
|
|
header structure and initial layout.
|
|
|
|
Like the CDFS(ISO 9660) file system,
|
|
the UDF file system uses a 2048 byte sector size,
|
|
and it designates that the first 16 sectors can be used by the OS
|
|
to store proprietary data or boot logic.
|
|
|
|
That means we need to check the first 32KB + descriptor size
|
|
to look for the ISO 9660 or UDF signature.
|
|
both formats have an extent based layout, so we can't determine
|
|
ahead of time where the descriptor will be located.
|
|
|
|
fortunately, the ISO 9660 and UDF formats have a Primary Volume Descriptor
|
|
located at the beginning of the image, which contains the volume size.
|
|
|
|
"""
|
|
|
|
def __init__(self, *a, **k):
|
|
super(ISOInspector, self).__init__(*a, **k)
|
|
self.new_region('system_area', CaptureRegion(0, 32 * units.Ki))
|
|
self.new_region('header', CaptureRegion(32 * units.Ki, 2 * units.Ki))
|
|
|
|
@property
|
|
def format_match(self):
|
|
if not self.complete:
|
|
return False
|
|
signature = self.region('header').data[1:6]
|
|
assert len(signature) == 5
|
|
return signature in (b'CD001', b'NSR02', b'NSR03')
|
|
|
|
@property
|
|
def virtual_size(self):
|
|
if not self.complete:
|
|
return 0
|
|
if not self.format_match:
|
|
return 0
|
|
|
|
# the header size is 2KB or 1 sector
|
|
# the first header field is the descriptor type which is 1 byte
|
|
# the second field is the standard identifier which is 5 bytes
|
|
# the third field is the version which is 1 byte
|
|
# the rest of the header contains type specific data is 2041 bytes
|
|
# see http://wiki.osdev.org/ISO_9660#The_Primary_Volume_Descriptor
|
|
|
|
# we need to check that the descriptor type is 1
|
|
# to ensure that this is a primary volume descriptor
|
|
descriptor_type = self.region('header').data[0]
|
|
if descriptor_type != 1:
|
|
return 0
|
|
# The size in bytes of a logical block is stored at offset 128
|
|
# and is 2 bytes long encoded in both little and big endian
|
|
# int16_LSB-MSB so the field is 4 bytes long
|
|
logical_block_size_data = self.region('header').data[128:132]
|
|
assert len(logical_block_size_data) == 4
|
|
# given the encoding we only need to read half the field so we
|
|
# can use the first 2 bytes which are the little endian part
|
|
# this is normally 2048 or 2KB but we need to check as it can be
|
|
# different according to the ISO 9660 standard.
|
|
logical_block_size, = struct.unpack('<H', logical_block_size_data[:2])
|
|
# The volume space size is the total number of logical blocks
|
|
# and is stored at offset 80 and is 8 bytes long
|
|
# as with the logical block size the field is encoded in both
|
|
# little and big endian as an int32_LSB-MSB
|
|
volume_space_size_data = self.region('header').data[80:88]
|
|
assert len(volume_space_size_data) == 8
|
|
# given the encoding we only need to read half the field so we
|
|
# can use the first 4 bytes which are the little endian part
|
|
volume_space_size, = struct.unpack('<L', volume_space_size_data[:4])
|
|
# the virtual size is the volume space size * logical block size
|
|
return volume_space_size * logical_block_size
|
|
|
|
def __str__(self):
|
|
return 'iso'
|
|
|
|
|
|
class InfoWrapper(object):
|
|
"""A file-like object that wraps another and updates a format inspector.
|
|
|
|
This passes chunks to the format inspector while reading. If the inspector
|
|
fails, it logs the error and stops calling it, but continues proxying data
|
|
from the source to its user.
|
|
"""
|
|
|
|
def __init__(self, source, fmt):
|
|
self._source = source
|
|
self._format = fmt
|
|
self._error = False
|
|
|
|
def __iter__(self):
|
|
return self
|
|
|
|
def _process_chunk(self, chunk):
|
|
if not self._error:
|
|
try:
|
|
self._format.eat_chunk(chunk)
|
|
except Exception as e:
|
|
# Absolutely do not allow the format inspector to break
|
|
# our streaming of the image. If we failed, just stop
|
|
# trying, log and keep going.
|
|
LOG.error('Format inspector failed, aborting: %s', e)
|
|
self._error = True
|
|
|
|
def __next__(self):
|
|
try:
|
|
chunk = next(self._source)
|
|
except StopIteration:
|
|
raise
|
|
self._process_chunk(chunk)
|
|
return chunk
|
|
|
|
def read(self, size):
|
|
chunk = self._source.read(size)
|
|
self._process_chunk(chunk)
|
|
return chunk
|
|
|
|
def close(self):
|
|
if hasattr(self._source, 'close'):
|
|
self._source.close()
|
|
|
|
|
|
ALL_FORMATS = {
|
|
'raw': FileInspector,
|
|
'qcow2': QcowInspector,
|
|
'vhd': VHDInspector,
|
|
'vhdx': VHDXInspector,
|
|
'vmdk': VMDKInspector,
|
|
'vdi': VDIInspector,
|
|
'qed': QEDInspector,
|
|
'iso': ISOInspector,
|
|
}
|
|
|
|
|
|
def get_inspector(format_name):
|
|
"""Returns a FormatInspector class based on the given name.
|
|
|
|
:param format_name: The name of the disk_format (raw, qcow2, etc).
|
|
:returns: A FormatInspector or None if unsupported.
|
|
"""
|
|
|
|
return ALL_FORMATS.get(format_name)
|
|
|
|
|
|
def detect_file_format(filename):
|
|
"""Attempts to detect the format of a file.
|
|
|
|
This runs through a file one time, running all the known inspectors in
|
|
parallel. It stops reading the file once all of them matches or all of
|
|
them are sure they don't match.
|
|
|
|
:param filename: The path to the file to inspect.
|
|
:returns: A FormatInspector instance matching the file.
|
|
:raises: ImageFormatError if multiple formats are detected.
|
|
"""
|
|
inspectors = {k: v() for k, v in ALL_FORMATS.items()}
|
|
detections = []
|
|
with open(filename, 'rb') as f:
|
|
for chunk in chunked_reader(f):
|
|
for format, inspector in list(inspectors.items()):
|
|
try:
|
|
inspector.eat_chunk(chunk)
|
|
except ImageFormatError:
|
|
# No match, so stop considering this format
|
|
inspectors.pop(format)
|
|
continue
|
|
if (inspector.format_match and inspector.complete
|
|
and format != 'raw'):
|
|
# record all match (other than raw)
|
|
detections.append(inspector)
|
|
inspectors.pop(format)
|
|
if all(i.complete for i in inspectors.values()):
|
|
# If all the inspectors are sure they are not a match, avoid
|
|
# reading to the end of the file to settle on 'raw'.
|
|
break
|
|
|
|
if len(detections) > 1:
|
|
all_formats = [str(inspector) for inspector in detections]
|
|
raise ImageFormatError(
|
|
'Multiple formats detected: %s' % ', '.join(all_formats))
|
|
|
|
return inspectors['raw'] if not detections else detections[0]
|