1#
2# Copyright (C) 2013 The Android Open Source Project
3#
4# Licensed under the Apache License, Version 2.0 (the "License");
5# you may not use this file except in compliance with the License.
6# You may obtain a copy of the License at
7#
8#      http://www.apache.org/licenses/LICENSE-2.0
9#
10# Unless required by applicable law or agreed to in writing, software
11# distributed under the License is distributed on an "AS IS" BASIS,
12# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13# See the License for the specific language governing permissions and
14# limitations under the License.
15#
16
17"""Utilities for update payload processing."""
18
19from __future__ import absolute_import
20from __future__ import print_function
21
22import base64
23
24from update_payload import update_metadata_pb2
25from update_payload.error import PayloadError
26
27
28#
29# Constants.
30#
31SIG_ASN1_HEADER = (
32    b'\x30\x31\x30\x0d\x06\x09\x60\x86'
33    b'\x48\x01\x65\x03\x04\x02\x01\x05'
34    b'\x00\x04\x20'
35)
36
37BRILLO_MAJOR_PAYLOAD_VERSION = 2
38
39SOURCE_MINOR_PAYLOAD_VERSION = 2
40OPSRCHASH_MINOR_PAYLOAD_VERSION = 3
41BROTLI_BSDIFF_MINOR_PAYLOAD_VERSION = 4
42PUFFDIFF_MINOR_PAYLOAD_VERSION = 5
43
44KERNEL = 'kernel'
45ROOTFS = 'root'
46# Tuple of (name in system, name in protobuf).
47CROS_PARTITIONS = ((KERNEL, KERNEL), (ROOTFS, 'rootfs'))
48
49
50#
51# Payload operation types.
52#
53class OpType(object):
54  """Container for operation type constants."""
55  _CLASS = update_metadata_pb2.InstallOperation
56  REPLACE = _CLASS.REPLACE
57  REPLACE_BZ = _CLASS.REPLACE_BZ
58  SOURCE_COPY = _CLASS.SOURCE_COPY
59  SOURCE_BSDIFF = _CLASS.SOURCE_BSDIFF
60  ZERO = _CLASS.ZERO
61  DISCARD = _CLASS.DISCARD
62  REPLACE_XZ = _CLASS.REPLACE_XZ
63  PUFFDIFF = _CLASS.PUFFDIFF
64  BROTLI_BSDIFF = _CLASS.BROTLI_BSDIFF
65  ALL = (REPLACE, REPLACE_BZ, SOURCE_COPY, SOURCE_BSDIFF, ZERO,
66         DISCARD, REPLACE_XZ, PUFFDIFF, BROTLI_BSDIFF)
67  NAMES = {
68      REPLACE: 'REPLACE',
69      REPLACE_BZ: 'REPLACE_BZ',
70      SOURCE_COPY: 'SOURCE_COPY',
71      SOURCE_BSDIFF: 'SOURCE_BSDIFF',
72      ZERO: 'ZERO',
73      DISCARD: 'DISCARD',
74      REPLACE_XZ: 'REPLACE_XZ',
75      PUFFDIFF: 'PUFFDIFF',
76      BROTLI_BSDIFF: 'BROTLI_BSDIFF',
77  }
78
79  def __init__(self):
80    pass
81
82
83#
84# Checked and hashed reading of data.
85#
86def IntPackingFmtStr(size, is_unsigned):
87  """Returns an integer format string for use by the struct module.
88
89  Args:
90    size: the integer size in bytes (2, 4 or 8)
91    is_unsigned: whether it is signed or not
92
93  Returns:
94    A format string for packing/unpacking integer values; assumes network byte
95    order (big-endian).
96
97  Raises:
98    PayloadError if something is wrong with the arguments.
99  """
100  # Determine the base conversion format.
101  if size == 2:
102    fmt = 'h'
103  elif size == 4:
104    fmt = 'i'
105  elif size == 8:
106    fmt = 'q'
107  else:
108    raise PayloadError('unsupport numeric field size (%s)' % size)
109
110  # Signed or unsigned?
111  if is_unsigned:
112    fmt = fmt.upper()
113
114  # Make it network byte order (big-endian).
115  fmt = '!' + fmt
116
117  return fmt
118
119
120def Read(file_obj, length, offset=None, hasher=None):
121  """Reads binary data from a file.
122
123  Args:
124    file_obj: an open file object
125    length: the length of the data to read
126    offset: an offset to seek to prior to reading; this is an absolute offset
127            from either the beginning (non-negative) or end (negative) of the
128            file.  (optional)
129    hasher: a hashing object to pass the read data through (optional)
130
131  Returns:
132    A string containing the read data.
133
134  Raises:
135    PayloadError if a read error occurred or not enough data was read.
136  """
137  if offset is not None:
138    if offset >= 0:
139      file_obj.seek(offset)
140    else:
141      file_obj.seek(offset, 2)
142
143  try:
144    data = file_obj.read(length)
145  except IOError as e:
146    raise PayloadError('error reading from file (%s): %s' % (file_obj.name, e))
147
148  if len(data) != length:
149    raise PayloadError(
150        'reading from file (%s) too short (%d instead of %d bytes)' %
151        (file_obj.name, len(data), length))
152
153  if hasher:
154    hasher.update(data)
155
156  return data
157
158
159#
160# Formatting functions.
161#
162def FormatExtent(ex, block_size=0):
163  end_block = ex.start_block + ex.num_blocks
164  if block_size:
165    return '%d->%d * %d' % (ex.start_block, end_block, block_size)
166  return '%d->%d' % (ex.start_block, end_block)
167
168
169def FormatSha256(digest):
170  """Returns a canonical string representation of a SHA256 digest."""
171  return base64.b64encode(digest).decode('utf-8')
172
173
174#
175# Useful iterators.
176#
177def _ObjNameIter(items, base_name, reverse=False, name_format_func=None):
178  """A generic (item, name) tuple iterators.
179
180  Args:
181    items: the sequence of objects to iterate on
182    base_name: the base name for all objects
183    reverse: whether iteration should be in reverse order
184    name_format_func: a function to apply to the name string
185
186  Yields:
187    An iterator whose i-th invocation returns (items[i], name), where name ==
188    base_name + '[i]' (with a formatting function optionally applied to it).
189  """
190  idx, inc = (len(items), -1) if reverse else (1, 1)
191  if reverse:
192    items = reversed(items)
193  for item in items:
194    item_name = '%s[%d]' % (base_name, idx)
195    if name_format_func:
196      item_name = name_format_func(item, item_name)
197    yield (item, item_name)
198    idx += inc
199
200
201def _OperationNameFormatter(op, op_name):
202  return '%s(%s)' % (op_name, OpType.NAMES.get(op.type, '?'))
203
204
205def OperationIter(operations, base_name, reverse=False):
206  """An (item, name) iterator for update operations."""
207  return _ObjNameIter(operations, base_name, reverse=reverse,
208                      name_format_func=_OperationNameFormatter)
209
210
211def ExtentIter(extents, base_name, reverse=False):
212  """An (item, name) iterator for operation extents."""
213  return _ObjNameIter(extents, base_name, reverse=reverse)
214
215
216def SignatureIter(sigs, base_name, reverse=False):
217  """An (item, name) iterator for signatures."""
218  return _ObjNameIter(sigs, base_name, reverse=reverse)
219