blob: 1211df3fdbdca91f350d8ca046c22645afdd8aa6 [file] [log] [blame]
#!/usr/bin/env python3
# Copyright 2016, The Android Open Source Project
#
# Permission is hereby granted, free of charge, to any person
# obtaining a copy of this software and associated documentation
# files (the "Software"), to deal in the Software without
# restriction, including without limitation the rights to use, copy,
# modify, merge, publish, distribute, sublicense, and/or sell copies
# of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
#
"""Command-line tool for working with Android Verified Boot images."""
import argparse
import binascii
import bisect
import hashlib
import json
import math
import os
import struct
import subprocess
import sys
import tempfile
import time
# Keep in sync with libavb/avb_version.h.
AVB_VERSION_MAJOR = 1
AVB_VERSION_MINOR = 2
AVB_VERSION_SUB = 0
# Keep in sync with libavb/avb_footer.h.
AVB_FOOTER_VERSION_MAJOR = 1
AVB_FOOTER_VERSION_MINOR = 0
AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED = 1
# Configuration for enabling logging of calls to avbtool.
AVB_INVOCATION_LOGFILE = os.environ.get('AVB_INVOCATION_LOGFILE')
class AvbError(Exception):
"""Application-specific errors.
These errors represent issues for which a stack-trace should not be
presented.
Attributes:
message: Error message.
"""
def __init__(self, message):
Exception.__init__(self, message)
class Algorithm(object):
"""Contains details about an algorithm.
See the avb_vbmeta_image.h file for more details about algorithms.
The constant |ALGORITHMS| is a dictionary from human-readable
names (e.g 'SHA256_RSA2048') to instances of this class.
Attributes:
algorithm_type: Integer code corresponding to |AvbAlgorithmType|.
hash_name: Empty or a name from |hashlib.algorithms|.
hash_num_bytes: Number of bytes used to store the hash.
signature_num_bytes: Number of bytes used to store the signature.
public_key_num_bytes: Number of bytes used to store the public key.
padding: Padding used for signature as bytes, if any.
"""
def __init__(self, algorithm_type, hash_name, hash_num_bytes,
signature_num_bytes, public_key_num_bytes, padding):
self.algorithm_type = algorithm_type
self.hash_name = hash_name
self.hash_num_bytes = hash_num_bytes
self.signature_num_bytes = signature_num_bytes
self.public_key_num_bytes = public_key_num_bytes
self.padding = padding
# This must be kept in sync with the avb_crypto.h file.
#
# The PKC1-v1.5 padding is a blob of binary DER of ASN.1 and is
# obtained from section 5.2.2 of RFC 4880.
ALGORITHMS = {
'NONE': Algorithm(
algorithm_type=0, # AVB_ALGORITHM_TYPE_NONE
hash_name='',
hash_num_bytes=0,
signature_num_bytes=0,
public_key_num_bytes=0,
padding=b''),
'SHA256_RSA2048': Algorithm(
algorithm_type=1, # AVB_ALGORITHM_TYPE_SHA256_RSA2048
hash_name='sha256',
hash_num_bytes=32,
signature_num_bytes=256,
public_key_num_bytes=8 + 2*2048//8,
padding=bytes(bytearray([
# PKCS1-v1_5 padding
0x00, 0x01] + [0xff]*202 + [0x00] + [
# ASN.1 header
0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05,
0x00, 0x04, 0x20,
]))),
'SHA256_RSA4096': Algorithm(
algorithm_type=2, # AVB_ALGORITHM_TYPE_SHA256_RSA4096
hash_name='sha256',
hash_num_bytes=32,
signature_num_bytes=512,
public_key_num_bytes=8 + 2*4096//8,
padding=bytes(bytearray([
# PKCS1-v1_5 padding
0x00, 0x01] + [0xff]*458 + [0x00] + [
# ASN.1 header
0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05,
0x00, 0x04, 0x20,
]))),
'SHA256_RSA8192': Algorithm(
algorithm_type=3, # AVB_ALGORITHM_TYPE_SHA256_RSA8192
hash_name='sha256',
hash_num_bytes=32,
signature_num_bytes=1024,
public_key_num_bytes=8 + 2*8192//8,
padding=bytes(bytearray([
# PKCS1-v1_5 padding
0x00, 0x01] + [0xff]*970 + [0x00] + [
# ASN.1 header
0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05,
0x00, 0x04, 0x20,
]))),
'SHA512_RSA2048': Algorithm(
algorithm_type=4, # AVB_ALGORITHM_TYPE_SHA512_RSA2048
hash_name='sha512',
hash_num_bytes=64,
signature_num_bytes=256,
public_key_num_bytes=8 + 2*2048//8,
padding=bytes(bytearray([
# PKCS1-v1_5 padding
0x00, 0x01] + [0xff]*170 + [0x00] + [
# ASN.1 header
0x30, 0x51, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03, 0x05,
0x00, 0x04, 0x40
]))),
'SHA512_RSA4096': Algorithm(
algorithm_type=5, # AVB_ALGORITHM_TYPE_SHA512_RSA4096
hash_name='sha512',
hash_num_bytes=64,
signature_num_bytes=512,
public_key_num_bytes=8 + 2*4096//8,
padding=bytes(bytearray([
# PKCS1-v1_5 padding
0x00, 0x01] + [0xff]*426 + [0x00] + [
# ASN.1 header
0x30, 0x51, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03, 0x05,
0x00, 0x04, 0x40
]))),
'SHA512_RSA8192': Algorithm(
algorithm_type=6, # AVB_ALGORITHM_TYPE_SHA512_RSA8192
hash_name='sha512',
hash_num_bytes=64,
signature_num_bytes=1024,
public_key_num_bytes=8 + 2*8192//8,
padding=bytes(bytearray([
# PKCS1-v1_5 padding
0x00, 0x01] + [0xff]*938 + [0x00] + [
# ASN.1 header
0x30, 0x51, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03, 0x05,
0x00, 0x04, 0x40
]))),
}
def get_release_string():
"""Calculates the release string to use in the VBMeta struct."""
# Keep in sync with libavb/avb_version.c:avb_version_string().
return 'avbtool {}.{}.{}'.format(AVB_VERSION_MAJOR,
AVB_VERSION_MINOR,
AVB_VERSION_SUB)
def round_to_multiple(number, size):
"""Rounds a number up to nearest multiple of another number.
Arguments:
number: The number to round up.
size: The multiple to round up to.
Returns:
If |number| is a multiple of |size|, returns |number|, otherwise
returns |number| + |size|.
"""
remainder = number % size
if remainder == 0:
return number
return number + size - remainder
def round_to_pow2(number):
"""Rounds a number up to the next power of 2.
Arguments:
number: The number to round up.
Returns:
If |number| is already a power of 2 then |number| is
returned. Otherwise the smallest power of 2 greater than |number|
is returned.
"""
return 2**((number - 1).bit_length())
def encode_long(num_bits, value):
"""Encodes a long to a bytearray() using a given amount of bits.
This number is written big-endian, e.g. with the most significant
bit first.
This is the reverse of decode_long().
Arguments:
num_bits: The number of bits to write, e.g. 2048.
value: The value to write.
Returns:
A bytearray() with the encoded long.
"""
ret = bytearray()
for bit_pos in range(num_bits, 0, -8):
octet = (value >> (bit_pos - 8)) & 0xff
ret.extend(struct.pack('!B', octet))
return ret
def decode_long(blob):
"""Decodes a long from a bytearray() using a given amount of bits.
This number is expected to be in big-endian, e.g. with the most
significant bit first.
This is the reverse of encode_long().
Arguments:
blob: A bytearray() with the encoded long.
Returns:
The decoded value.
"""
ret = 0
for b in bytearray(blob):
ret *= 256
ret += b
return ret
def egcd(a, b):
"""Calculate greatest common divisor of two numbers.
This implementation uses a recursive version of the extended
Euclidian algorithm.
Arguments:
a: First number.
b: Second number.
Returns:
A tuple (gcd, x, y) that where |gcd| is the greatest common
divisor of |a| and |b| and |a|*|x| + |b|*|y| = |gcd|.
"""
if a == 0:
return (b, 0, 1)
g, y, x = egcd(b % a, a)
return (g, x - (b // a) * y, y)
def modinv(a, m):
"""Calculate modular multiplicative inverse of |a| modulo |m|.
This calculates the number |x| such that |a| * |x| == 1 (modulo
|m|). This number only exists if |a| and |m| are co-prime - |None|
is returned if this isn't true.
Arguments:
a: The number to calculate a modular inverse of.
m: The modulo to use.
Returns:
The modular multiplicative inverse of |a| and |m| or |None| if
these numbers are not co-prime.
"""
gcd, x, _ = egcd(a, m)
if gcd != 1:
return None # modular inverse does not exist
return x % m
def parse_number(string):
"""Parse a string as a number.
This is just a short-hand for int(string, 0) suitable for use in the
|type| parameter of |ArgumentParser|'s add_argument() function. An
improvement to just using type=int is that this function supports
numbers in other bases, e.g. "0x1234".
Arguments:
string: The string to parse.
Returns:
The parsed integer.
Raises:
ValueError: If the number could not be parsed.
"""
return int(string, 0)
class RSAPublicKey(object):
"""Data structure used for a RSA public key.
Attributes:
exponent: The key exponent.
modulus: The key modulus.
num_bits: The key size.
"""
MODULUS_PREFIX = b'modulus='
def __init__(self, key_path):
"""Loads and parses an RSA key from either a private or public key file.
Arguments:
key_path: The path to a key file.
Raises:
AvbError: If RSA key parameters could not be read from file.
"""
# We used to have something as simple as this:
#
# key = Crypto.PublicKey.RSA.importKey(open(key_path).read())
# self.exponent = key.e
# self.modulus = key.n
# self.num_bits = key.size() + 1
#
# but unfortunately PyCrypto is not available in the builder. So
# instead just parse openssl(1) output to get this
# information. It's ugly but...
args = ['openssl', 'rsa', '-in', key_path, '-modulus', '-noout']
p = subprocess.Popen(args,
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
(pout, perr) = p.communicate()
if p.wait() != 0:
# Could be just a public key is passed, try that.
args.append('-pubin')
p = subprocess.Popen(args,
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
(pout, perr) = p.communicate()
if p.wait() != 0:
raise AvbError('Error getting public key: {}'.format(perr))
if not pout.lower().startswith(self.MODULUS_PREFIX):
raise AvbError('Unexpected modulus output')
modulus_hexstr = pout[len(self.MODULUS_PREFIX):]
# The exponent is assumed to always be 65537 and the number of
# bits can be derived from the modulus by rounding up to the
# nearest power of 2.
self.key_path = key_path
self.modulus = int(modulus_hexstr, 16)
self.num_bits = round_to_pow2(int(math.ceil(math.log(self.modulus, 2))))
self.exponent = 65537
def encode(self):
"""Encodes the public RSA key in |AvbRSAPublicKeyHeader| format.
This creates a |AvbRSAPublicKeyHeader| as well as the two large
numbers (|key_num_bits| bits long) following it.
Returns:
The |AvbRSAPublicKeyHeader| followed by two large numbers as bytes.
Raises:
AvbError: If given RSA key exponent is not 65537.
"""
if self.exponent != 65537:
raise AvbError('Only RSA keys with exponent 65537 are supported.')
ret = bytearray()
# Calculate n0inv = -1/n[0] (mod 2^32)
b = 2 ** 32
n0inv = b - modinv(self.modulus, b)
# Calculate rr = r^2 (mod N), where r = 2^(# of key bits)
r = 2 ** self.modulus.bit_length()
rrmodn = r * r % self.modulus
ret.extend(struct.pack('!II', self.num_bits, n0inv))
ret.extend(encode_long(self.num_bits, self.modulus))
ret.extend(encode_long(self.num_bits, rrmodn))
return bytes(ret)
def sign(self, algorithm_name, data_to_sign, signing_helper=None,
signing_helper_with_files=None):
"""Sign given data using |signing_helper| or openssl.
openssl is used if neither the parameters signing_helper nor
signing_helper_with_files are given.
Arguments:
algorithm_name: The algorithm name as per the ALGORITHMS dict.
data_to_sign: Data to sign as bytes or bytearray.
signing_helper: Program which signs a hash and returns the signature.
signing_helper_with_files: Same as signing_helper but uses files instead.
Returns:
The signature as bytes.
Raises:
AvbError: If an error occurred during signing.
"""
# Checks requested algorithm for validity.
algorithm = ALGORITHMS.get(algorithm_name)
if not algorithm:
raise AvbError('Algorithm with name {} is not supported.'
.format(algorithm_name))
if self.num_bits != (algorithm.signature_num_bytes * 8):
raise AvbError('Key size of key ({} bits) does not match key size '
'({} bits) of given algorithm {}.'
.format(self.num_bits, algorithm.signature_num_bytes * 8,
algorithm_name))
# Hashes the data.
hasher = hashlib.new(algorithm.hash_name)
hasher.update(data_to_sign)
digest = hasher.digest()
# Calculates the signature.
padding_and_hash = algorithm.padding + digest
p = None
if signing_helper_with_files is not None:
with tempfile.NamedTemporaryFile() as signing_file:
signing_file.write(padding_and_hash)
signing_file.flush()
p = subprocess.Popen([signing_helper_with_files, algorithm_name,
self.key_path, signing_file.name])
retcode = p.wait()
if retcode != 0:
raise AvbError('Error signing')
signing_file.seek(0)
signature = signing_file.read()
else:
if signing_helper is not None:
p = subprocess.Popen(
[signing_helper, algorithm_name, self.key_path],
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
else:
p = subprocess.Popen(
['openssl', 'rsautl', '-sign', '-inkey', self.key_path, '-raw'],
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
(pout, perr) = p.communicate(padding_and_hash)
retcode = p.wait()
if retcode != 0:
raise AvbError('Error signing: {}'.format(perr))
signature = pout
if len(signature) != algorithm.signature_num_bytes:
raise AvbError('Error signing: Invalid length of signature')
return signature
def lookup_algorithm_by_type(alg_type):
"""Looks up algorithm by type.
Arguments:
alg_type: The integer representing the type.
Returns:
A tuple with the algorithm name and an |Algorithm| instance.
Raises:
Exception: If the algorithm cannot be found
"""
for alg_name in ALGORITHMS:
alg_data = ALGORITHMS[alg_name]
if alg_data.algorithm_type == alg_type:
return (alg_name, alg_data)
raise AvbError('Unknown algorithm type {}'.format(alg_type))
def lookup_hash_size_by_type(alg_type):
"""Looks up hash size by type.
Arguments:
alg_type: The integer representing the type.
Returns:
The corresponding hash size.
Raises:
AvbError: If the algorithm cannot be found.
"""
for alg_name in ALGORITHMS:
alg_data = ALGORITHMS[alg_name]
if alg_data.algorithm_type == alg_type:
return alg_data.hash_num_bytes
raise AvbError('Unsupported algorithm type {}'.format(alg_type))
def verify_vbmeta_signature(vbmeta_header, vbmeta_blob):
"""Checks that signature in a vbmeta blob was made by the embedded public key.
Arguments:
vbmeta_header: A AvbVBMetaHeader.
vbmeta_blob: The whole vbmeta blob, including the header as bytes or
bytearray.
Returns:
True if the signature is valid and corresponds to the embedded
public key. Also returns True if the vbmeta blob is not signed.
Raises:
AvbError: If there errors calling out to openssl command during
signature verification.
"""
(_, alg) = lookup_algorithm_by_type(vbmeta_header.algorithm_type)
if not alg.hash_name:
return True
header_blob = vbmeta_blob[0:256]
auth_offset = 256
aux_offset = auth_offset + vbmeta_header.authentication_data_block_size
aux_size = vbmeta_header.auxiliary_data_block_size
aux_blob = vbmeta_blob[aux_offset:aux_offset + aux_size]
pubkey_offset = aux_offset + vbmeta_header.public_key_offset
pubkey_size = vbmeta_header.public_key_size
pubkey_blob = vbmeta_blob[pubkey_offset:pubkey_offset + pubkey_size]
digest_offset = auth_offset + vbmeta_header.hash_offset
digest_size = vbmeta_header.hash_size
digest_blob = vbmeta_blob[digest_offset:digest_offset + digest_size]
sig_offset = auth_offset + vbmeta_header.signature_offset
sig_size = vbmeta_header.signature_size
sig_blob = vbmeta_blob[sig_offset:sig_offset + sig_size]
# Now that we've got the stored digest, public key, and signature
# all we need to do is to verify. This is the exactly the same
# steps as performed in the avb_vbmeta_image_verify() function in
# libavb/avb_vbmeta_image.c.
ha = hashlib.new(alg.hash_name)
ha.update(header_blob)
ha.update(aux_blob)
computed_digest = ha.digest()
if computed_digest != digest_blob:
return False
padding_and_digest = alg.padding + computed_digest
(num_bits,) = struct.unpack('!I', pubkey_blob[0:4])
modulus_blob = pubkey_blob[8:8 + num_bits//8]
modulus = decode_long(modulus_blob)
exponent = 65537
# We used to have this:
#
# import Crypto.PublicKey.RSA
# key = Crypto.PublicKey.RSA.construct((modulus, long(exponent)))
# if not key.verify(decode_long(padding_and_digest),
# (decode_long(sig_blob), None)):
# return False
# return True
#
# but since 'avbtool verify_image' is used on the builders we don't want
# to rely on Crypto.PublicKey.RSA. Instead just use openssl(1) to verify.
asn1_str = ('asn1=SEQUENCE:pubkeyinfo\n'
'\n'
'[pubkeyinfo]\n'
'algorithm=SEQUENCE:rsa_alg\n'
'pubkey=BITWRAP,SEQUENCE:rsapubkey\n'
'\n'
'[rsa_alg]\n'
'algorithm=OID:rsaEncryption\n'
'parameter=NULL\n'
'\n'
'[rsapubkey]\n'
'n=INTEGER:{}\n'
'e=INTEGER:{}\n').format(hex(modulus).rstrip('L'),
hex(exponent).rstrip('L'))
with tempfile.NamedTemporaryFile() as asn1_tmpfile:
asn1_tmpfile.write(asn1_str.encode('ascii'))
asn1_tmpfile.flush()
with tempfile.NamedTemporaryFile() as der_tmpfile:
p = subprocess.Popen(
['openssl', 'asn1parse', '-genconf', asn1_tmpfile.name, '-out',
der_tmpfile.name, '-noout'])
retcode = p.wait()
if retcode != 0:
raise AvbError('Error generating DER file')
p = subprocess.Popen(
['openssl', 'rsautl', '-verify', '-pubin', '-inkey', der_tmpfile.name,
'-keyform', 'DER', '-raw'],
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
(pout, perr) = p.communicate(sig_blob)
retcode = p.wait()
if retcode != 0:
raise AvbError('Error verifying data: {}'.format(perr))
if pout != padding_and_digest:
sys.stderr.write('Signature not correct\n')
return False
return True
class ImageChunk(object):
"""Data structure used for representing chunks in Android sparse files.
Attributes:
chunk_type: One of TYPE_RAW, TYPE_FILL, or TYPE_DONT_CARE.
chunk_offset: Offset in the sparse file where this chunk begins.
output_offset: Offset in de-sparsified file where output begins.
output_size: Number of bytes in output.
input_offset: Offset in sparse file for data if TYPE_RAW otherwise None.
fill_data: Blob with data to fill if TYPE_FILL otherwise None.
"""
FORMAT = '<2H2I'
TYPE_RAW = 0xcac1
TYPE_FILL = 0xcac2
TYPE_DONT_CARE = 0xcac3
TYPE_CRC32 = 0xcac4
def __init__(self, chunk_type, chunk_offset, output_offset, output_size,
input_offset, fill_data):
"""Initializes an ImageChunk object.
Arguments:
chunk_type: One of TYPE_RAW, TYPE_FILL, or TYPE_DONT_CARE.
chunk_offset: Offset in the sparse file where this chunk begins.
output_offset: Offset in de-sparsified file.
output_size: Number of bytes in output.
input_offset: Offset in sparse file if TYPE_RAW otherwise None.
fill_data: Blob as bytes with data to fill if TYPE_FILL otherwise None.
Raises:
ValueError: If given chunk parameters are invalid.
"""
self.chunk_type = chunk_type
self.chunk_offset = chunk_offset
self.output_offset = output_offset
self.output_size = output_size
self.input_offset = input_offset
self.fill_data = fill_data
# Check invariants.
if self.chunk_type == self.TYPE_RAW:
if self.fill_data is not None:
raise ValueError('RAW chunk cannot have fill_data set.')
if not self.input_offset:
raise ValueError('RAW chunk must have input_offset set.')
elif self.chunk_type == self.TYPE_FILL:
if self.fill_data is None:
raise ValueError('FILL chunk must have fill_data set.')
if self.input_offset:
raise ValueError('FILL chunk cannot have input_offset set.')
elif self.chunk_type == self.TYPE_DONT_CARE:
if self.fill_data is not None:
raise ValueError('DONT_CARE chunk cannot have fill_data set.')
if self.input_offset:
raise ValueError('DONT_CARE chunk cannot have input_offset set.')
else:
raise ValueError('Invalid chunk type')
class ImageHandler(object):
"""Abstraction for image I/O with support for Android sparse images.
This class provides an interface for working with image files that
may be using the Android Sparse Image format. When an instance is
constructed, we test whether it's an Android sparse file. If so,
operations will be on the sparse file by interpreting the sparse
format, otherwise they will be directly on the file. Either way the
operations do the same.
For reading, this interface mimics a file object - it has seek(),
tell(), and read() methods. For writing, only truncation
(truncate()) and appending is supported (append_raw() and
append_dont_care()). Additionally, data can only be written in units
of the block size.
Attributes:
filename: Name of file.
is_sparse: Whether the file being operated on is sparse.
block_size: The block size, typically 4096.
image_size: The size of the unsparsified file.
"""
# See system/core/libsparse/sparse_format.h for details.
MAGIC = 0xed26ff3a
HEADER_FORMAT = '<I4H4I'
# These are formats and offset of just the |total_chunks| and
# |total_blocks| fields.
NUM_CHUNKS_AND_BLOCKS_FORMAT = '<II'
NUM_CHUNKS_AND_BLOCKS_OFFSET = 16
def __init__(self, image_filename, read_only=False):
"""Initializes an image handler.
Arguments:
image_filename: The name of the file to operate on.
read_only: True if file is only opened for read-only operations.
Raises:
ValueError: If data in the file is invalid.
"""
self.filename = image_filename
self._num_total_blocks = 0
self._num_total_chunks = 0
self._file_pos = 0
self._read_only = read_only
self._read_header()
def _read_header(self):
"""Initializes internal data structures used for reading file.
This may be called multiple times and is typically called after
modifying the file (e.g. appending, truncation).
Raises:
ValueError: If data in the file is invalid.
"""
self.is_sparse = False
self.block_size = 4096
self._file_pos = 0
if self._read_only:
self._image = open(self.filename, 'rb')
else:
self._image = open(self.filename, 'r+b')
self._image.seek(0, os.SEEK_END)
self.image_size = self._image.tell()
self._image.seek(0, os.SEEK_SET)
header_bin = self._image.read(struct.calcsize(self.HEADER_FORMAT))
(magic, major_version, minor_version, file_hdr_sz, chunk_hdr_sz,
block_size, self._num_total_blocks, self._num_total_chunks,
_) = struct.unpack(self.HEADER_FORMAT, header_bin)
if magic != self.MAGIC:
# Not a sparse image, our job here is done.
return
if not (major_version == 1 and minor_version == 0):
raise ValueError('Encountered sparse image format version {}.{} but '
'only 1.0 is supported'.format(major_version,
minor_version))
if file_hdr_sz != struct.calcsize(self.HEADER_FORMAT):
raise ValueError('Unexpected file_hdr_sz value {}.'.
format(file_hdr_sz))
if chunk_hdr_sz != struct.calcsize(ImageChunk.FORMAT):
raise ValueError('Unexpected chunk_hdr_sz value {}.'.
format(chunk_hdr_sz))
self.block_size = block_size
# Build an list of chunks by parsing the file.
self._chunks = []
# Find the smallest offset where only "Don't care" chunks
# follow. This will be the size of the content in the sparse
# image.
offset = 0
output_offset = 0
for _ in range(1, self._num_total_chunks + 1):
chunk_offset = self._image.tell()
header_bin = self._image.read(struct.calcsize(ImageChunk.FORMAT))
(chunk_type, _, chunk_sz, total_sz) = struct.unpack(ImageChunk.FORMAT,
header_bin)
data_sz = total_sz - struct.calcsize(ImageChunk.FORMAT)
if chunk_type == ImageChunk.TYPE_RAW:
if data_sz != (chunk_sz * self.block_size):
raise ValueError('Raw chunk input size ({}) does not match output '
'size ({})'.
format(data_sz, chunk_sz*self.block_size))
self._chunks.append(ImageChunk(ImageChunk.TYPE_RAW,
chunk_offset,
output_offset,
chunk_sz*self.block_size,
self._image.tell(),
None))
self._image.seek(data_sz, os.SEEK_CUR)
elif chunk_type == ImageChunk.TYPE_FILL:
if data_sz != 4:
raise ValueError('Fill chunk should have 4 bytes of fill, but this '
'has {}'.format(data_sz))
fill_data = self._image.read(4)
self._chunks.append(ImageChunk(ImageChunk.TYPE_FILL,
chunk_offset,
output_offset,
chunk_sz*self.block_size,
None,
fill_data))
elif chunk_type == ImageChunk.TYPE_DONT_CARE:
if data_sz != 0:
raise ValueError('Don\'t care chunk input size is non-zero ({})'.
format(data_sz))
self._chunks.append(ImageChunk(ImageChunk.TYPE_DONT_CARE,
chunk_offset,
output_offset,
chunk_sz*self.block_size,
None,
None))
elif chunk_type == ImageChunk.TYPE_CRC32:
if data_sz != 4:
raise ValueError('CRC32 chunk should have 4 bytes of CRC, but '
'this has {}'.format(data_sz))
self._image.read(4)
else:
raise ValueError('Unknown chunk type {}'.format(chunk_type))
offset += chunk_sz
output_offset += chunk_sz*self.block_size
# Record where sparse data end.
self._sparse_end = self._image.tell()
# Now that we've traversed all chunks, sanity check.
if self._num_total_blocks != offset:
raise ValueError('The header said we should have {} output blocks, '
'but we saw {}'.format(self._num_total_blocks, offset))
junk_len = len(self._image.read())
if junk_len > 0:
raise ValueError('There were {} bytes of extra data at the end of the '
'file.'.format(junk_len))
# Assign |image_size|.
self.image_size = output_offset
# This is used when bisecting in read() to find the initial slice.
self._chunk_output_offsets = [i.output_offset for i in self._chunks]
self.is_sparse = True
def _update_chunks_and_blocks(self):
"""Helper function to update the image header.
The the |total_chunks| and |total_blocks| fields in the header
will be set to value of the |_num_total_blocks| and
|_num_total_chunks| attributes.
"""
self._image.seek(self.NUM_CHUNKS_AND_BLOCKS_OFFSET, os.SEEK_SET)
self._image.write(struct.pack(self.NUM_CHUNKS_AND_BLOCKS_FORMAT,
self._num_total_blocks,
self._num_total_chunks))
def append_dont_care(self, num_bytes):
"""Appends a DONT_CARE chunk to the sparse file.
The given number of bytes must be a multiple of the block size.
Arguments:
num_bytes: Size in number of bytes of the DONT_CARE chunk.
Raises
OSError: If ImageHandler was initialized in read-only mode.
"""
assert num_bytes % self.block_size == 0
if self._read_only:
raise OSError('ImageHandler is in read-only mode.')
if not self.is_sparse:
self._image.seek(0, os.SEEK_END)
# This is more efficient that writing NUL bytes since it'll add
# a hole on file systems that support sparse files (native
# sparse, not Android sparse).
self._image.truncate(self._image.tell() + num_bytes)
self._read_header()
return
self._num_total_chunks += 1
self._num_total_blocks += num_bytes // self.block_size
self._update_chunks_and_blocks()
self._image.seek(self._sparse_end, os.SEEK_SET)
self._image.write(struct.pack(ImageChunk.FORMAT,
ImageChunk.TYPE_DONT_CARE,
0, # Reserved
num_bytes // self.block_size,
struct.calcsize(ImageChunk.FORMAT)))
self._read_header()
def append_raw(self, data):
"""Appends a RAW chunk to the sparse file.
The length of the given data must be a multiple of the block size.
Arguments:
data: Data to append as bytes.
Raises
OSError: If ImageHandler was initialized in read-only mode.
"""
assert len(data) % self.block_size == 0
if self._read_only:
raise OSError('ImageHandler is in read-only mode.')
if not self.is_sparse:
self._image.seek(0, os.SEEK_END)
self._image.write(data)
self._read_header()
return
self._num_total_chunks += 1
self._num_total_blocks += len(data) // self.block_size
self._update_chunks_and_blocks()
self._image.seek(self._sparse_end, os.SEEK_SET)
self._image.write(struct.pack(ImageChunk.FORMAT,
ImageChunk.TYPE_RAW,
0, # Reserved
len(data) // self.block_size,
len(data) +
struct.calcsize(ImageChunk.FORMAT)))
self._image.write(data)
self._read_header()
def append_fill(self, fill_data, size):
"""Appends a fill chunk to the sparse file.
The total length of the fill data must be a multiple of the block size.
Arguments:
fill_data: Fill data to append - must be four bytes.
size: Number of chunk - must be a multiple of four and the block size.
Raises
OSError: If ImageHandler was initialized in read-only mode.
"""
assert len(fill_data) == 4
assert size % 4 == 0
assert size % self.block_size == 0
if self._read_only:
raise OSError('ImageHandler is in read-only mode.')
if not self.is_sparse:
self._image.seek(0, os.SEEK_END)
self._image.write(fill_data * (size//4))
self._read_header()
return
self._num_total_chunks += 1
self._num_total_blocks += size // self.block_size
self._update_chunks_and_blocks()
self._image.seek(self._sparse_end, os.SEEK_SET)
self._image.write(struct.pack(ImageChunk.FORMAT,
ImageChunk.TYPE_FILL,
0, # Reserved
size // self.block_size,
4 + struct.calcsize(ImageChunk.FORMAT)))
self._image.write(fill_data)
self._read_header()
def seek(self, offset):
"""Sets the cursor position for reading from unsparsified file.
Arguments:
offset: Offset to seek to from the beginning of the file.
Raises:
RuntimeError: If the given offset is negative.
"""
if offset < 0:
raise RuntimeError('Seeking with negative offset: {}'.format(offset))
self._file_pos = offset
def read(self, size):
"""Reads data from the unsparsified file.
This method may return fewer than |size| bytes of data if the end
of the file was encountered.
The file cursor for reading is advanced by the number of bytes
read.
Arguments:
size: Number of bytes to read.
Returns:
The data as bytes.
"""
if not self.is_sparse:
self._image.seek(self._file_pos)
data = self._image.read(size)
self._file_pos += len(data)
return data
# Iterate over all chunks.
chunk_idx = bisect.bisect_right(self._chunk_output_offsets,
self._file_pos) - 1
data = bytearray()
to_go = size
while to_go > 0:
chunk = self._chunks[chunk_idx]
chunk_pos_offset = self._file_pos - chunk.output_offset
chunk_pos_to_go = min(chunk.output_size - chunk_pos_offset, to_go)
if chunk.chunk_type == ImageChunk.TYPE_RAW:
self._image.seek(chunk.input_offset + chunk_pos_offset)
data.extend(self._image.read(chunk_pos_to_go))
elif chunk.chunk_type == ImageChunk.TYPE_FILL:
all_data = chunk.fill_data*(chunk_pos_to_go // len(chunk.fill_data) + 2)
offset_mod = chunk_pos_offset % len(chunk.fill_data)
data.extend(all_data[offset_mod:(offset_mod + chunk_pos_to_go)])
else:
assert chunk.chunk_type == ImageChunk.TYPE_DONT_CARE
data.extend(b'\0' * chunk_pos_to_go)
to_go -= chunk_pos_to_go
self._file_pos += chunk_pos_to_go
chunk_idx += 1
# Generate partial read in case of EOF.
if chunk_idx >= len(self._chunks):
break
return bytes(data)
def tell(self):
"""Returns the file cursor position for reading from unsparsified file.
Returns:
The file cursor position for reading.
"""
return self._file_pos
def truncate(self, size):
"""Truncates the unsparsified file.
Arguments:
size: Desired size of unsparsified file.
Raises:
ValueError: If desired size isn't a multiple of the block size.
OSError: If ImageHandler was initialized in read-only mode.
"""
if self._read_only:
raise OSError('ImageHandler is in read-only mode.')
if not self.is_sparse:
self._image.truncate(size)
self._read_header()
return
if size % self.block_size != 0:
raise ValueError('Cannot truncate to a size which is not a multiple '
'of the block size')
if size == self.image_size:
# Trivial where there's nothing to do.
return
if size < self.image_size:
chunk_idx = bisect.bisect_right(self._chunk_output_offsets, size) - 1
chunk = self._chunks[chunk_idx]
if chunk.output_offset != size:
# Truncation in the middle of a trunk - need to keep the chunk
# and modify it.
chunk_idx_for_update = chunk_idx + 1
num_to_keep = size - chunk.output_offset
assert num_to_keep % self.block_size == 0
if chunk.chunk_type == ImageChunk.TYPE_RAW:
truncate_at = (chunk.chunk_offset +
struct.calcsize(ImageChunk.FORMAT) + num_to_keep)
data_sz = num_to_keep
elif chunk.chunk_type == ImageChunk.TYPE_FILL:
truncate_at = (chunk.chunk_offset +
struct.calcsize(ImageChunk.FORMAT) + 4)
data_sz = 4
else:
assert chunk.chunk_type == ImageChunk.TYPE_DONT_CARE
truncate_at = chunk.chunk_offset + struct.calcsize(ImageChunk.FORMAT)
data_sz = 0
chunk_sz = num_to_keep // self.block_size
total_sz = data_sz + struct.calcsize(ImageChunk.FORMAT)
self._image.seek(chunk.chunk_offset)
self._image.write(struct.pack(ImageChunk.FORMAT,
chunk.chunk_type,
0, # Reserved
chunk_sz,
total_sz))
chunk.output_size = num_to_keep
else:
# Truncation at trunk boundary.
truncate_at = chunk.chunk_offset
chunk_idx_for_update = chunk_idx
self._num_total_chunks = chunk_idx_for_update
self._num_total_blocks = 0
for i in range(0, chunk_idx_for_update):
self._num_total_blocks += self._chunks[i].output_size // self.block_size
self._update_chunks_and_blocks()
self._image.truncate(truncate_at)
# We've modified the file so re-read all data.
self._read_header()
else:
# Truncating to grow - just add a DONT_CARE section.
self.append_dont_care(size - self.image_size)
class AvbDescriptor(object):
"""Class for AVB descriptor.
See the |AvbDescriptor| C struct for more information.
Attributes:
tag: The tag identifying what kind of descriptor this is.
data: The data in the descriptor.
"""
SIZE = 16
FORMAT_STRING = ('!QQ') # tag, num_bytes_following (descriptor header)
def __init__(self, data):
"""Initializes a new property descriptor.
Arguments:
data: If not None, must be a bytearray().
Raises:
LookupError: If the given descriptor is malformed.
"""
assert struct.calcsize(self.FORMAT_STRING) == self.SIZE
if data:
(self.tag, num_bytes_following) = (
struct.unpack(self.FORMAT_STRING, data[0:self.SIZE]))
self.data = data[self.SIZE:self.SIZE + num_bytes_following]
else:
self.tag = None
self.data = None
def print_desc(self, o):
"""Print the descriptor.
Arguments:
o: The object to write the output to.
"""
o.write(' Unknown descriptor:\n')
o.write(' Tag: {}\n'.format(self.tag))
if len(self.data) < 256:
o.write(' Data: {} ({} bytes)\n'.format(
repr(str(self.data)), len(self.data)))
else:
o.write(' Data: {} bytes\n'.format(len(self.data)))
def encode(self):
"""Serializes the descriptor.
Returns:
A bytearray() with the descriptor data.
"""
num_bytes_following = len(self.data)
nbf_with_padding = round_to_multiple(num_bytes_following, 8)
padding_size = nbf_with_padding - num_bytes_following
desc = struct.pack(self.FORMAT_STRING, self.tag, nbf_with_padding)
padding = struct.pack(str(padding_size) + 'x')
ret = desc + self.data + padding
return bytearray(ret)
def verify(self, image_dir, image_ext, expected_chain_partitions_map,
image_containing_descriptor, accept_zeroed_hashtree):
"""Verifies contents of the descriptor - used in verify_image sub-command.
Arguments:
image_dir: The directory of the file being verified.
image_ext: The extension of the file being verified (e.g. '.img').
expected_chain_partitions_map: A map from partition name to the
tuple (rollback_index_location, key_blob).
image_containing_descriptor: The image the descriptor is in.
accept_zeroed_hashtree: If True, don't fail if hashtree or FEC data is
zeroed out.
Returns:
True if the descriptor verifies, False otherwise.
"""
# Deletes unused parameters to prevent pylint warning unused-argument.
del image_dir, image_ext, expected_chain_partitions_map
del image_containing_descriptor, accept_zeroed_hashtree
# Nothing to do.
return True
class AvbPropertyDescriptor(AvbDescriptor):
"""A class for property descriptors.
See the |AvbPropertyDescriptor| C struct for more information.
Attributes:
key: The key as string.
value: The value as bytes.
"""
TAG = 0
SIZE = 32
FORMAT_STRING = ('!QQ' # tag, num_bytes_following (descriptor header)
'Q' # key size (bytes)
'Q') # value size (bytes)
def __init__(self, data=None):
"""Initializes a new property descriptor.
Arguments:
data: If not None, must be as bytes of size |SIZE|.
Raises:
LookupError: If the given descriptor is malformed.
"""
super(AvbPropertyDescriptor, self).__init__(None)
assert struct.calcsize(self.FORMAT_STRING) == self.SIZE
if data:
(tag, num_bytes_following, key_size,
value_size) = struct.unpack(self.FORMAT_STRING, data[0:self.SIZE])
expected_size = round_to_multiple(
self.SIZE - 16 + key_size + 1 + value_size + 1, 8)
if tag != self.TAG or num_bytes_following != expected_size:
raise LookupError('Given data does not look like a property '
'descriptor.')
try:
self.key = data[self.SIZE:(self.SIZE + key_size)].decode('utf-8')
except UnicodeDecodeError as e:
raise LookupError('Key cannot be decoded as UTF-8: {}.'.format(e))
self.value = data[(self.SIZE + key_size + 1):(self.SIZE + key_size + 1 +
value_size)]
else:
self.key = ''
self.value = b''
def print_desc(self, o):
"""Print the descriptor.
Arguments:
o: The object to write the output to.
"""
# Go forward with python 3, bytes are represented with the 'b' prefix,
# e.g. b'foobar'. Thus, we trim off the 'b' to keep the print output
# the same between python 2 and python 3.
printable_value = repr(self.value)
if printable_value.startswith('b\''):
printable_value = printable_value[1:]
if len(self.value) < 256:
o.write(' Prop: {} -> {}\n'.format(self.key, printable_value))
else:
o.write(' Prop: {} -> ({} bytes)\n'.format(self.key, len(self.value)))
def encode(self):
"""Serializes the descriptor.
Returns:
The descriptor data as bytes.
"""
key_encoded = self.key.encode('utf-8')
num_bytes_following = (
self.SIZE + len(key_encoded) + len(self.value) + 2 - 16)
nbf_with_padding = round_to_multiple(num_bytes_following, 8)
padding_size = nbf_with_padding - num_bytes_following
desc = struct.pack(self.FORMAT_STRING, self.TAG, nbf_with_padding,
len(key_encoded), len(self.value))
ret = (desc + key_encoded + b'\0' + self.value + b'\0' +
padding_size * b'\0')
return ret
def verify(self, image_dir, image_ext, expected_chain_partitions_map,
image_containing_descriptor, accept_zeroed_hashtree):
"""Verifies contents of the descriptor - used in verify_image sub-command.
Arguments:
image_dir: The directory of the file being verified.
image_ext: The extension of the file being verified (e.g. '.img').
expected_chain_partitions_map: A map from partition name to the
tuple (rollback_index_location, key_blob).
image_containing_descriptor: The image the descriptor is in.
accept_zeroed_hashtree: If True, don't fail if hashtree or FEC data is
zeroed out.
Returns:
True if the descriptor verifies, False otherwise.
"""
# Nothing to do.
return True
class AvbHashtreeDescriptor(AvbDescriptor):
"""A class for hashtree descriptors.
See the |AvbHashtreeDescriptor| C struct for more information.
Attributes:
dm_verity_version: dm-verity version used.
image_size: Size of the image, after rounding up to |block_size|.
tree_offset: Offset of the hash tree in the file.
tree_size: Size of the tree.
data_block_size: Data block size.
hash_block_size: Hash block size.
fec_num_roots: Number of roots used for FEC (0 if FEC is not used).
fec_offset: Offset of FEC data (0 if FEC is not used).
fec_size: Size of FEC data (0 if FEC is not used).
hash_algorithm: Hash algorithm used as string.
partition_name: Partition name as string.
salt: Salt used as bytes.
root_digest: Root digest as bytes.
flags: Descriptor flags (see avb_hashtree_descriptor.h).
"""
TAG = 1
RESERVED = 60
SIZE = 120 + RESERVED
FORMAT_STRING = ('!QQ' # tag, num_bytes_following (descriptor header)
'L' # dm-verity version used
'Q' # image size (bytes)
'Q' # tree offset (bytes)
'Q' # tree size (bytes)
'L' # data block size (bytes)
'L' # hash block size (bytes)
'L' # FEC number of roots
'Q' # FEC offset (bytes)
'Q' # FEC size (bytes)
'32s' # hash algorithm used
'L' # partition name (bytes)
'L' # salt length (bytes)
'L' # root digest length (bytes)
'L' + # flags
str(RESERVED) + 's') # reserved
def __init__(self, data=None):
"""Initializes a new hashtree descriptor.
Arguments:
data: If not None, must be bytes of size |SIZE|.
Raises:
LookupError: If the given descriptor is malformed.
"""
super(AvbHashtreeDescriptor, self).__init__(None)
assert struct.calcsize(self.FORMAT_STRING) == self.SIZE
if data:
(tag, num_bytes_following, self.dm_verity_version, self.image_size,
self.tree_offset, self.tree_size, self.data_block_size,
self.hash_block_size, self.fec_num_roots, self.fec_offset, self.fec_size,
self.hash_algorithm, partition_name_len, salt_len,
root_digest_len, self.flags, _) = struct.unpack(self.FORMAT_STRING,
data[0:self.SIZE])
expected_size = round_to_multiple(
self.SIZE - 16 + partition_name_len + salt_len + root_digest_len, 8)
if tag != self.TAG or num_bytes_following != expected_size:
raise LookupError('Given data does not look like a hashtree '
'descriptor.')
# Nuke NUL-bytes at the end.
self.hash_algorithm = self.hash_algorithm.rstrip(b'\0').decode('ascii')
o = 0
try:
self.partition_name = data[
(self.SIZE + o):(self.SIZE + o + partition_name_len)
].decode('utf-8')
except UnicodeDecodeError as e:
raise LookupError('Partition name cannot be decoded as UTF-8: {}.'
.format(e))
o += partition_name_len
self.salt = data[(self.SIZE + o):(self.SIZE + o + salt_len)]
o += salt_len
self.root_digest = data[(self.SIZE + o):(self.SIZE + o + root_digest_len)]
if root_digest_len != len(hashlib.new(self.hash_algorithm).digest()):
if root_digest_len != 0:
raise LookupError('root_digest_len doesn\'t match hash algorithm')
else:
self.dm_verity_version = 0
self.image_size = 0
self.tree_offset = 0
self.tree_size = 0
self.data_block_size = 0
self.hash_block_size = 0
self.fec_num_roots = 0
self.fec_offset = 0
self.fec_size = 0
self.hash_algorithm = ''
self.partition_name = ''
self.salt = b''
self.root_digest = b''
self.flags = 0
def print_desc(self, o):
"""Print the descriptor.
Arguments:
o: The object to write the output to.
"""
o.write(' Hashtree descriptor:\n')
o.write(' Version of dm-verity: {}\n'.format(self.dm_verity_version))
o.write(' Image Size: {} bytes\n'.format(self.image_size))
o.write(' Tree Offset: {}\n'.format(self.tree_offset))
o.write(' Tree Size: {} bytes\n'.format(self.tree_size))
o.write(' Data Block Size: {} bytes\n'.format(
self.data_block_size))
o.write(' Hash Block Size: {} bytes\n'.format(
self.hash_block_size))
o.write(' FEC num roots: {}\n'.format(self.fec_num_roots))
o.write(' FEC offset: {}\n'.format(self.fec_offset))
o.write(' FEC size: {} bytes\n'.format(self.fec_size))
o.write(' Hash Algorithm: {}\n'.format(self.hash_algorithm))
o.write(' Partition Name: {}\n'.format(self.partition_name))
o.write(' Salt: {}\n'.format(self.salt.hex()))
o.write(' Root Digest: {}\n'.format(self.root_digest.hex()))
o.write(' Flags: {}\n'.format(self.flags))
def encode(self):
"""Serializes the descriptor.
Returns:
The descriptor data as bytes.
"""
hash_algorithm_encoded = self.hash_algorithm.encode('ascii')
partition_name_encoded = self.partition_name.encode('utf-8')
num_bytes_following = (self.SIZE + len(partition_name_encoded)
+ len(self.salt) + len(self.root_digest) - 16)
nbf_with_padding = round_to_multiple(num_bytes_following, 8)
padding_size = nbf_with_padding - num_bytes_following
desc = struct.pack(self.FORMAT_STRING, self.TAG, nbf_with_padding,
self.dm_verity_version, self.image_size,
self.tree_offset, self.tree_size, self.data_block_size,
self.hash_block_size, self.fec_num_roots,
self.fec_offset, self.fec_size, hash_algorithm_encoded,
len(partition_name_encoded), len(self.salt),
len(self.root_digest), self.flags, self.RESERVED * b'\0')
ret = (desc + partition_name_encoded + self.salt + self.root_digest +
padding_size * b'\0')
return ret
def verify(self, image_dir, image_ext, expected_chain_partitions_map,
image_containing_descriptor, accept_zeroed_hashtree):
"""Verifies contents of the descriptor - used in verify_image sub-command.
Arguments:
image_dir: The directory of the file being verified.
image_ext: The extension of the file being verified (e.g. '.img').
expected_chain_partitions_map: A map from partition name to the
tuple (rollback_index_location, key_blob).
image_containing_descriptor: The image the descriptor is in.
accept_zeroed_hashtree: If True, don't fail if hashtree or FEC data is
zeroed out.
Returns:
True if the descriptor verifies, False otherwise.
"""
if not self.partition_name:
image_filename = image_containing_descriptor.filename
image = image_containing_descriptor
else:
image_filename = os.path.join(image_dir, self.partition_name + image_ext)
image = ImageHandler(image_filename, read_only=True)
# Generate the hashtree and checks that it matches what's in the file.
digest_size = len(hashlib.new(self.hash_algorithm).digest())
digest_padding = round_to_pow2(digest_size) - digest_size
(hash_level_offsets, tree_size) = calc_hash_level_offsets(
self.image_size, self.data_block_size, digest_size + digest_padding)
root_digest, hash_tree = generate_hash_tree(image, self.image_size,
self.data_block_size,
self.hash_algorithm, self.salt,
digest_padding,
hash_level_offsets,
tree_size)
# The root digest must match unless it is not embedded in the descriptor.
if self.root_digest and root_digest != self.root_digest:
sys.stderr.write('hashtree of {} does not match descriptor\n'.
format(image_filename))
return False
# ... also check that the on-disk hashtree matches
image.seek(self.tree_offset)
hash_tree_ondisk = image.read(self.tree_size)
is_zeroed = (self.tree_size == 0) or (hash_tree_ondisk[0:8] == b'ZeRoHaSH')
if is_zeroed and accept_zeroed_hashtree:
print('{}: skipping verification since hashtree is zeroed and '
'--accept_zeroed_hashtree was given'
.format(self.partition_name))
else:
if hash_tree != hash_tree_ondisk:
sys.stderr.write('hashtree of {} contains invalid data\n'.
format(image_filename))
return False
print('{}: Successfully verified {} hashtree of {} for image of {} bytes'
.format(self.partition_name, self.hash_algorithm, image.filename,
self.image_size))
# TODO(zeuthen): we could also verify that the FEC stored in the image is
# correct but this a) currently requires the 'fec' binary; and b) takes a
# long time; and c) is not strictly needed for verification purposes as
# we've already verified the root hash.
return True
class AvbHashDescriptor(AvbDescriptor):
"""A class for hash descriptors.
See the |AvbHashDescriptor| C struct for more information.
Attributes:
image_size: Image size, in bytes.
hash_algorithm: Hash algorithm used as string.
partition_name: Partition name as string.
salt: Salt used as bytes.
digest: The hash value of salt and data combined as bytes.
flags: The descriptor flags (see avb_hash_descriptor.h).
"""
TAG = 2
RESERVED = 60
SIZE = 72 + RESERVED
FORMAT_STRING = ('!QQ' # tag, num_bytes_following (descriptor header)
'Q' # image size (bytes)
'32s' # hash algorithm used
'L' # partition name (bytes)
'L' # salt length (bytes)
'L' # digest length (bytes)
'L' + # flags
str(RESERVED) + 's') # reserved
def __init__(self, data=None):
"""Initializes a new hash descriptor.
Arguments:
data: If not None, must be bytes of size |SIZE|.
Raises:
LookupError: If the given descriptor is malformed.
"""
super(AvbHashDescriptor, self).__init__(None)
assert struct.calcsize(self.FORMAT_STRING) == self.SIZE
if data:
(tag, num_bytes_following, self.image_size, self.hash_algorithm,
partition_name_len, salt_len,
digest_len, self.flags, _) = struct.unpack(self.FORMAT_STRING,
data[0:self.SIZE])
expected_size = round_to_multiple(
self.SIZE - 16 + partition_name_len + salt_len + digest_len, 8)
if tag != self.TAG or num_bytes_following != expected_size:
raise LookupError('Given data does not look like a hash descriptor.')
# Nuke NUL-bytes at the end.
self.hash_algorithm = self.hash_algorithm.rstrip(b'\0').decode('ascii')
o = 0
try:
self.partition_name = data[
(self.SIZE + o):(self.SIZE + o + partition_name_len)
].decode('utf-8')
except UnicodeDecodeError as e:
raise LookupError('Partition name cannot be decoded as UTF-8: {}.'
.format(e))
o += partition_name_len
self.salt = data[(self.SIZE + o):(self.SIZE + o + salt_len)]
o += salt_len
self.digest = data[(self.SIZE + o):(self.SIZE + o + digest_len)]
if digest_len != len(hashlib.new(self.hash_algorithm).digest()):
if digest_len != 0:
raise LookupError('digest_len doesn\'t match hash algorithm')
else:
self.image_size = 0
self.hash_algorithm = ''
self.partition_name = ''
self.salt = b''
self.digest = b''
self.flags = 0
def print_desc(self, o):
"""Print the descriptor.
Arguments:
o: The object to write the output to.
"""
o.write(' Hash descriptor:\n')
o.write(' Image Size: {} bytes\n'.format(self.image_size))
o.write(' Hash Algorithm: {}\n'.format(self.hash_algorithm))
o.write(' Partition Name: {}\n'.format(self.partition_name))
o.write(' Salt: {}\n'.format(self.salt.hex()))
o.write(' Digest: {}\n'.format(self.digest.hex()))
o.write(' Flags: {}\n'.format(self.flags))
def encode(self):
"""Serializes the descriptor.
Returns:
The descriptor data as bytes.
"""
hash_algorithm_encoded = self.hash_algorithm.encode('ascii')
partition_name_encoded = self.partition_name.encode('utf-8')
num_bytes_following = (self.SIZE + len(partition_name_encoded) +
len(self.salt) + len(self.digest) - 16)
nbf_with_padding = round_to_multiple(num_bytes_following, 8)
padding_size = nbf_with_padding - num_bytes_following
desc = struct.pack(self.FORMAT_STRING, self.TAG, nbf_with_padding,
self.image_size, hash_algorithm_encoded,
len(partition_name_encoded), len(self.salt),
len(self.digest), self.flags, self.RESERVED * b'\0')
ret = (desc + partition_name_encoded + self.salt + self.digest +
padding_size * b'\0')
return ret
def verify(self, image_dir, image_ext, expected_chain_partitions_map,
image_containing_descriptor, accept_zeroed_hashtree):
"""Verifies contents of the descriptor - used in verify_image sub-command.
Arguments:
image_dir: The directory of the file being verified.
image_ext: The extension of the file being verified (e.g. '.img').
expected_chain_partitions_map: A map from partition name to the
tuple (rollback_index_location, key_blob).
image_containing_descriptor: The image the descriptor is in.
accept_zeroed_hashtree: If True, don't fail if hashtree or FEC data is
zeroed out.
Returns:
True if the descriptor verifies, False otherwise.
"""
if not self.partition_name:
image_filename = image_containing_descriptor.filename
image = image_containing_descriptor
else:
image_filename = os.path.join(image_dir, self.partition_name + image_ext)
image = ImageHandler(image_filename, read_only=True)
data = image.read(self.image_size)
ha = hashlib.new(self.hash_algorithm)
ha.update(self.salt)
ha.update(data)
digest = ha.digest()
# The digest must match unless there is no digest in the descriptor.
if self.digest and digest != self.digest:
sys.stderr.write('{} digest of {} does not match digest in descriptor\n'.
format(self.hash_algorithm, image_filename))
return False
print('{}: Successfully verified {} hash of {} for image of {} bytes'
.format(self.partition_name, self.hash_algorithm, image.filename,
self.image_size))
return True
class AvbKernelCmdlineDescriptor(AvbDescriptor):
"""A class for kernel command-line descriptors.
See the |AvbKernelCmdlineDescriptor| C struct for more information.
Attributes:
flags: Flags.
kernel_cmdline: The kernel command-line as string.
"""
TAG = 3
SIZE = 24
FORMAT_STRING = ('!QQ' # tag, num_bytes_following (descriptor header)
'L' # flags
'L') # cmdline length (bytes)
FLAGS_USE_ONLY_IF_HASHTREE_NOT_DISABLED = (1 << 0)
FLAGS_USE_ONLY_IF_HASHTREE_DISABLED = (1 << 1)
def __init__(self, data=None):
"""Initializes a new kernel cmdline descriptor.
Arguments:
data: If not None, must be bytes of size |SIZE|.
Raises:
LookupError: If the given descriptor is malformed.
"""
super(AvbKernelCmdlineDescriptor, self).__init__(None)
assert struct.calcsize(self.FORMAT_STRING) == self.SIZE
if data:
(tag, num_bytes_following, self.flags, kernel_cmdline_length) = (
struct.unpack(self.FORMAT_STRING, data[0:self.SIZE]))
expected_size = round_to_multiple(self.SIZE - 16 + kernel_cmdline_length,
8)
if tag != self.TAG or num_bytes_following != expected_size:
raise LookupError('Given data does not look like a kernel cmdline '
'descriptor.')
# Nuke NUL-bytes at the end.
try:
self.kernel_cmdline = data[
self.SIZE:(self.SIZE + kernel_cmdline_length)].decode('utf-8')
except UnicodeDecodeError as e:
raise LookupError('Kernel command-line cannot be decoded as UTF-8: {}.'
.format(e))
else:
self.flags = 0
self.kernel_cmdline = ''
def print_desc(self, o):
"""Print the descriptor.
Arguments:
o: The object to write the output to.
"""
o.write(' Kernel Cmdline descriptor:\n')
o.write(' Flags: {}\n'.format(self.flags))
o.write(' Kernel Cmdline: \'{}\'\n'.format(self.kernel_cmdline))
def encode(self):
"""Serializes the descriptor.
Returns:
The descriptor data as bytes.
"""
kernel_cmd_encoded = self.kernel_cmdline.encode('utf-8')
num_bytes_following = (self.SIZE + len(kernel_cmd_encoded) - 16)
nbf_with_padding = round_to_multiple(num_bytes_following, 8)
padding_size = nbf_with_padding - num_bytes_following
desc = struct.pack(self.FORMAT_STRING, self.TAG, nbf_with_padding,
self.flags, len(kernel_cmd_encoded))
ret = desc + kernel_cmd_encoded + padding_size * b'\0'
return ret
def verify(self, image_dir, image_ext, expected_chain_partitions_map,
image_containing_descriptor, accept_zeroed_hashtree):
"""Verifies contents of the descriptor - used in verify_image sub-command.
Arguments:
image_dir: The directory of the file being verified.
image_ext: The extension of the file being verified (e.g. '.img').
expected_chain_partitions_map: A map from partition name to the
tuple (rollback_index_location, key_blob).
image_containing_descriptor: The image the descriptor is in.
accept_zeroed_hashtree: If True, don't fail if hashtree or FEC data is
zeroed out.
Returns:
True if the descriptor verifies, False otherwise.
"""
# Nothing to verify.
return True
class AvbChainPartitionDescriptor(AvbDescriptor):
"""A class for chained partition descriptors.
See the |AvbChainPartitionDescriptor| C struct for more information.
Attributes:
rollback_index_location: The rollback index location to use.
partition_name: Partition name as string.
public_key: The public key as bytes.
"""
TAG = 4
RESERVED = 64
SIZE = 28 + RESERVED
FORMAT_STRING = ('!QQ' # tag, num_bytes_following (descriptor header)
'L' # rollback_index_location
'L' # partition_name_size (bytes)
'L' + # public_key_size (bytes)
str(RESERVED) + 's') # reserved
def __init__(self, data=None):
"""Initializes a new chain partition descriptor.
Arguments:
data: If not None, must be a bytearray of size |SIZE|.
Raises:
LookupError: If the given descriptor is malformed.
"""
AvbDescriptor.__init__(self, None)
assert struct.calcsize(self.FORMAT_STRING) == self.SIZE
if data:
(tag, num_bytes_following, self.rollback_index_location,
partition_name_len,
public_key_len, _) = struct.unpack(self.FORMAT_STRING, data[0:self.SIZE])
expected_size = round_to_multiple(
self.SIZE - 16 + partition_name_len + public_key_len, 8)
if tag != self.TAG or num_bytes_following != expected_size:
raise LookupError('Given data does not look like a chain partition '
'descriptor.')
o = 0
try:
self.partition_name = data[
(self.SIZE + o):(self.SIZE + o + partition_name_len)
].decode('utf-8')
except UnicodeDecodeError as e:
raise LookupError('Partition name cannot be decoded as UTF-8: {}.'
.format(e))
o += partition_name_len
self.public_key = data[(self.SIZE + o):(self.SIZE + o + public_key_len)]
else:
self.rollback_index_location = 0
self.partition_name = ''
self.public_key = b''
def print_desc(self, o):
"""Print the descriptor.
Arguments:
o: The object to write the output to.
"""
o.write(' Chain Partition descriptor:\n')
o.write(' Partition Name: {}\n'.format(self.partition_name))
o.write(' Rollback Index Location: {}\n'.format(
self.rollback_index_location))
# Just show the SHA1 of the key, for size reasons.
pubkey_digest = hashlib.sha1(self.public_key).hexdigest()
o.write(' Public key (sha1): {}\n'.format(pubkey_digest))
def encode(self):
"""Serializes the descriptor.
Returns:
The descriptor data as bytes.
"""
partition_name_encoded = self.partition_name.encode('utf-8')
num_bytes_following = (
self.SIZE + len(partition_name_encoded) + len(self.public_key) - 16)
nbf_with_padding = round_to_multiple(num_bytes_following, 8)
padding_size = nbf_with_padding - num_bytes_following
desc = struct.pack(self.FORMAT_STRING, self.TAG, nbf_with_padding,
self.rollback_index_location,
len(partition_name_encoded), len(self.public_key),
self.RESERVED * b'\0')
ret = desc + partition_name_encoded + self.public_key + padding_size * b'\0'
return ret
def verify(self, image_dir, image_ext, expected_chain_partitions_map,
image_containing_descriptor, accept_zeroed_hashtree):
"""Verifies contents of the descriptor - used in verify_image sub-command.
Arguments:
image_dir: The directory of the file being verified.
image_ext: The extension of the file being verified (e.g. '.img').
expected_chain_partitions_map: A map from partition name to the
tuple (rollback_index_location, key_blob).
image_containing_descriptor: The image the descriptor is in.
accept_zeroed_hashtree: If True, don't fail if hashtree or FEC data is
zeroed out.
Returns:
True if the descriptor verifies, False otherwise.
"""
value = expected_chain_partitions_map.get(self.partition_name)
if not value:
sys.stderr.write('No expected chain partition for partition {}. Use '
'--expected_chain_partition to specify expected '
'contents or --follow_chain_partitions.\n'.
format(self.partition_name))
return False
rollback_index_location, pk_blob = value
if self.rollback_index_location != rollback_index_location:
sys.stderr.write('Expected rollback_index_location {} does not '
'match {} in descriptor for partition {}\n'.
format(rollback_index_location,
self.rollback_index_location,
self.partition_name))
return False
if self.public_key != pk_blob:
sys.stderr.write('Expected public key blob does not match public '
'key blob in descriptor for partition {}\n'.
format(self.partition_name))
return False
print('{}: Successfully verified chain partition descriptor matches '
'expected data'.format(self.partition_name))
return True
DESCRIPTOR_CLASSES = [
AvbPropertyDescriptor, AvbHashtreeDescriptor, AvbHashDescriptor,
AvbKernelCmdlineDescriptor, AvbChainPartitionDescriptor
]
def parse_descriptors(data):
"""Parses a blob of data into descriptors.
Arguments:
data: Encoded descriptors as bytes.
Returns:
A list of instances of objects derived from AvbDescriptor. For
unknown descriptors, the class AvbDescriptor is used.
"""
o = 0
ret = []
while o < len(data):
tag, nb_following = struct.unpack('!2Q', data[o:o + 16])
if tag < len(DESCRIPTOR_CLASSES):
clazz = DESCRIPTOR_CLASSES[tag]
else:
clazz = AvbDescriptor
ret.append(clazz(data[o:o + 16 + nb_following]))
o += 16 + nb_following
return ret
class AvbFooter(object):
"""A class for parsing and writing footers.
Footers are stored at the end of partitions and point to where the
AvbVBMeta blob is located. They also contain the original size of
the image before AVB information was added.
Attributes:
magic: Magic for identifying the footer, see |MAGIC|.
version_major: The major version of avbtool that wrote the footer.
version_minor: The minor version of avbtool that wrote the footer.
original_image_size: Original image size.
vbmeta_offset: Offset of where the AvbVBMeta blob is stored.
vbmeta_size: Size of the AvbVBMeta blob.
"""
MAGIC = b'AVBf'
SIZE = 64
RESERVED = 28
FOOTER_VERSION_MAJOR = AVB_FOOTER_VERSION_MAJOR
FOOTER_VERSION_MINOR = AVB_FOOTER_VERSION_MINOR
FORMAT_STRING = ('!4s2L' # magic, 2 x version.
'Q' # Original image size.
'Q' # Offset of VBMeta blob.
'Q' + # Size of VBMeta blob.
str(RESERVED) + 'x') # padding for reserved bytes
def __init__(self, data=None):
"""Initializes a new footer object.
Arguments:
data: If not None, must be bytes of size 4096.
Raises:
LookupError: If the given footer is malformed.
struct.error: If the given data has no footer.
"""
assert struct.calcsize(self.FORMAT_STRING) == self.SIZE
if data:
(self.magic, self.version_major, self.version_minor,
self.original_image_size, self.vbmeta_offset,
self.vbmeta_size) = struct.unpack(self.FORMAT_STRING, data)
if self.magic != self.MAGIC:
raise LookupError('Given data does not look like a AVB footer.')
else:
self.magic = self.MAGIC
self.version_major = self.FOOTER_VERSION_MAJOR
self.version_minor = self.FOOTER_VERSION_MINOR
self.original_image_size = 0
self.vbmeta_offset = 0
self.vbmeta_size = 0
def encode(self):
"""Serializes the footer.
Returns:
The footer as bytes.
"""
return struct.pack(self.FORMAT_STRING, self.magic, self.version_major,
self.version_minor, self.original_image_size,
self.vbmeta_offset, self.vbmeta_size)
class AvbVBMetaHeader(object):
"""A class for parsing and writing AVB vbmeta images.
The attributes correspond to the |AvbVBMetaImageHeader| struct defined in
avb_vbmeta_image.h.
Attributes:
magic: Four bytes equal to "AVB0" (AVB_MAGIC).
required_libavb_version_major: The major version of libavb required for this
header.
required_libavb_version_minor: The minor version of libavb required for this
header.
authentication_data_block_size: The size of the signature block.
auxiliary_data_block_size: The size of the auxiliary data block.
algorithm_type: The verification algorithm used, see |AvbAlgorithmType|
enum.
hash_offset: Offset into the "Authentication data" block of hash data.
hash_size: Length of the hash data.
signature_offset: Offset into the "Authentication data" block of signature
data.
signature_size: Length of the signature data.
public_key_offset: Offset into the "Auxiliary data" block of public key
data.
public_key_size: Length of the public key data.
public_key_metadata_offset: Offset into the "Auxiliary data" block of public
key metadata.
public_key_metadata_size: Length of the public key metadata. Must be set to
zero if there is no public key metadata.
descriptors_offset: Offset into the "Auxiliary data" block of descriptor
data.
descriptors_size: Length of descriptor data.
rollback_index: The rollback index which can be used to prevent rollback to
older versions.
flags: Flags from the AvbVBMetaImageFlags enumeration. This must be set to
zero if the vbmeta image is not a top-level image.
rollback_index_location: The location of the rollback index defined in this
header. Only valid for the main vbmeta. For chained partitions, the
rollback index location must be specified in the
AvbChainPartitionDescriptor and this value must be set to 0.
release_string: The release string from avbtool, e.g. "avbtool 1.0.0" or
"avbtool 1.0.0 xyz_board Git-234abde89". Is guaranteed to be NUL
terminated. Applications must not make assumptions about how this
string is formatted.
"""
MAGIC = b'AVB0'
SIZE = 256
# Keep in sync with |reserved| field of |AvbVBMetaImageHeader|.
RESERVED = 80
# Keep in sync with |AvbVBMetaImageHeader|.
FORMAT_STRING = ('!4s2L' # magic, 2 x version
'2Q' # 2 x block size
'L' # algorithm type
'2Q' # offset, size (hash)
'2Q' # offset, size (signature)
'2Q' # offset, size (public key)
'2Q' # offset, size (public key metadata)
'2Q' # offset, size (descriptors)
'Q' # rollback_index
'L' # flags
'L' # rollback_index_location
'47sx' + # NUL-terminated release string
str(RESERVED) + 'x') # padding for reserved bytes
def __init__(self, data=None):
"""Initializes a new header object.
Arguments:
data: If not None, must be a bytearray of size 8192.
Raises:
Exception: If the given data is malformed.
"""
assert struct.calcsize(self.FORMAT_STRING) == self.SIZE
if data:
(self.magic, self.required_libavb_version_major,
self.required_libavb_version_minor,
self.authentication_data_block_size, self.auxiliary_data_block_size,
self.algorithm_type, self.hash_offset, self.hash_size,
self.signature_offset, self.signature_size, self.public_key_offset,
self.public_key_size, self.public_key_metadata_offset,
self.public_key_metadata_size, self.descriptors_offset,
self.descriptors_size,
self.rollback_index,
self.flags,
self.rollback_index_location,
release_string) = struct.unpack(self.FORMAT_STRING, data)
# Nuke NUL-bytes at the end of the string.
if self.magic != self.MAGIC:
raise AvbError('Given image does not look like a vbmeta image.')
self.release_string = release_string.rstrip(b'\0').decode('utf-8')
else:
self.magic = self.MAGIC
# Start by just requiring version 1.0. Code that adds features
# in a future version can use bump_required_libavb_version_minor() to
# bump the minor.
self.required_libavb_version_major = AVB_VERSION_MAJOR
self.required_libavb_version_minor = 0
self.authentication_data_block_size = 0
self.auxiliary_data_block_size = 0
self.algorithm_type = 0
self.hash_offset = 0
self.hash_size = 0
self.signature_offset = 0
self.signature_size = 0
self.public_key_offset = 0
self.public_key_size = 0
self.public_key_metadata_offset = 0
self.public_key_metadata_size = 0
self.descriptors_offset = 0
self.descriptors_size = 0
self.rollback_index = 0
self.flags = 0
self.rollback_index_location = 0
self.release_string = get_release_string()
def bump_required_libavb_version_minor(self, minor):
"""Function to bump required_libavb_version_minor.
Call this when writing data that requires a specific libavb
version to parse it.
Arguments:
minor: The minor version of libavb that has support for the feature.
"""
self.required_libavb_version_minor = (
max(self.required_libavb_version_minor, minor))
def encode(self):
"""Serializes the header.
Returns:
The header as bytes.
"""
release_string_encoded = self.release_string.encode('utf-8')
return struct.pack(self.FORMAT_STRING, self.magic,
self.required_libavb_version_major,
self.required_libavb_version_minor,
self.authentication_data_block_size,
self.auxiliary_data_block_size, self.algorithm_type,
self.hash_offset, self.hash_size, self.signature_offset,
self.signature_size, self.public_key_offset,
self.public_key_size, self.public_key_metadata_offset,
self.public_key_metadata_size, self.descriptors_offset,
self.descriptors_size, self.rollback_index, self.flags,
self.rollback_index_location, release_string_encoded)
class Avb(object):
"""Business logic for avbtool command-line tool."""
# Keep in sync with avb_ab_flow.h.
AB_FORMAT_NO_CRC = '!4sBB2xBBBxBBBx12x'
AB_MAGIC = b'\0AB0'
AB_MAJOR_VERSION = 1
AB_MINOR_VERSION = 0
AB_MISC_METADATA_OFFSET = 2048
# Constants for maximum metadata size. These are used to give
# meaningful errors if the value passed in via --partition_size is
# too small and when --calc_max_image_size is used. We use
# conservative figures.
MAX_VBMETA_SIZE = 64 * 1024
MAX_FOOTER_SIZE = 4096
def generate_test_image(self, output, image_size, start_byte):
"""Generates a test image for testing avbtool with known content.
The content has following pattern: 0x00 0x01 0x02 .. 0xff 0x00 0x01 ..).
Arguments:
output: Write test image to this file.
image_size: The size of the requested file in bytes.
start_byte: The integer value of the start byte to use for pattern
generation.
"""
pattern = bytearray([x & 0xFF for x in range(start_byte, start_byte + 256)])
buf = bytearray()
c = int(math.ceil(image_size / 256.0))
for _ in range(0, c):
buf.extend(pattern)
output.write(buf[0:image_size])
def extract_vbmeta_image(self, output, image_filename, padding_size):
"""Implements the 'extract_vbmeta_image' command.
Arguments:
output: Write vbmeta struct to this file.
image_filename: File to extract vbmeta data from (with a footer).
padding_size: If not 0, pads output so size is a multiple of the number.
Raises:
AvbError: If there's no footer in the image.
"""
image = ImageHandler(image_filename, read_only=True)
(footer, _, _, _) = self._parse_image(image)
if not footer:
raise AvbError('Given image does not have a footer.')
image.seek(footer.vbmeta_offset)
vbmeta_blob = image.read(footer.vbmeta_size)
output.write(vbmeta_blob)
if padding_size > 0:
padded_size = round_to_multiple(len(vbmeta_blob), padding_size)
padding_needed = padded_size - len(vbmeta_blob)
output.write(b'\0' * padding_needed)
def erase_footer(self, image_filename, keep_hashtree):
"""Implements the 'erase_footer' command.
Arguments:
image_filename: File to erase a footer from.
keep_hashtree: If True, keep the hashtree and FEC around.
Raises:
AvbError: If there's no footer in the image.
"""
image = ImageHandler(image_filename)
(footer, _, descriptors, _) = self._parse_image(image)
if not footer:
raise AvbError('Given image does not have a footer.')
new_image_size = None
if not keep_hashtree:
new_image_size = footer.original_image_size
else:
# If requested to keep the hashtree, search for a hashtree
# descriptor to figure out the location and size of the hashtree
# and FEC.
for desc in descriptors:
if isinstance(desc, AvbHashtreeDescriptor):
# The hashtree is always just following the main data so the
# new size is easily derived.
new_image_size = desc.tree_offset + desc.tree_size
# If the image has FEC codes, also keep those.
if desc.fec_offset > 0:
fec_end = desc.fec_offset + desc.fec_size
new_image_size = max(new_image_size, fec_end)
break
if not new_image_size:
raise AvbError('Requested to keep hashtree but no hashtree '
'descriptor was found.')
# And cut...
image.truncate(new_image_size)
def zero_hashtree(self, image_filename):
"""Implements the 'zero_hashtree' command.
Arguments:
image_filename: File to zero hashtree and FEC data from.
Raises:
AvbError: If there's no footer in the image.
"""
image = ImageHandler(image_filename)
(footer, _, descriptors, _) = self._parse_image(image)
if not footer:
raise AvbError('Given image does not have a footer.')
# Search for a hashtree descriptor to figure out the location and
# size of the hashtree and FEC.
ht_desc = None
for desc in descriptors:
if isinstance(desc, AvbHashtreeDescriptor):
ht_desc = desc
break
if not ht_desc:
raise AvbError('No hashtree descriptor was found.')
zero_ht_start_offset = ht_desc.tree_offset
zero_ht_num_bytes = ht_desc.tree_size
zero_fec_start_offset = None
zero_fec_num_bytes = 0
if ht_desc.fec_offset > 0:
if ht_desc.fec_offset != ht_desc.tree_offset + ht_desc.tree_size:
raise AvbError('Hash-tree and FEC data must be adjacent.')
zero_fec_start_offset = ht_desc.fec_offset
zero_fec_num_bytes = ht_desc.fec_size
zero_end_offset = (zero_ht_start_offset + zero_ht_num_bytes
+ zero_fec_num_bytes)
image.seek(zero_end_offset)
data = image.read(image.image_size - zero_end_offset)
# Write zeroes all over hashtree and FEC, except for the first eight bytes
# where a magic marker - ZeroHaSH - is placed. Place these markers in the
# beginning of both hashtree and FEC. (That way, in the future we can add
# options to 'avbtool zero_hashtree' so as to zero out only either/or.)
#
# Applications can use these markers to detect that the hashtree and/or
# FEC needs to be recomputed.
image.truncate(zero_ht_start_offset)
data_zeroed_firstblock = b'ZeRoHaSH' + b'\0' * (image.block_size - 8)
image.append_raw(data_zeroed_firstblock)
image.append_fill(b'\0\0\0\0', zero_ht_num_bytes - image.block_size)
if zero_fec_start_offset:
image.append_raw(data_zeroed_firstblock)
image.append_fill(b'\0\0\0\0', zero_fec_num_bytes - image.block_size)
image.append_raw(data)
def resize_image(self, image_filename, partition_size):
"""Implements the 'resize_image' command.
Arguments:
image_filename: File with footer to resize.
partition_size: The new size of the image.
Raises:
AvbError: If there's no footer in the image.
"""
image = ImageHandler(image_filename)
if partition_size % image.block_size != 0:
raise AvbError('Partition size of {} is not a multiple of the image '
'block size {}.'.format(partition_size,
image.block_size))
(footer, _, _, _) = self._parse_image(image)
if not footer:
raise AvbError('Given image does not have a footer.')
# The vbmeta blob is always at the end of the data so resizing an
# image amounts to just moving the footer around.
vbmeta_end_offset = footer.vbmeta_offset + footer.vbmeta_size
if vbmeta_end_offset % image.block_size != 0:
vbmeta_end_offset += image.block_size - (vbmeta_end_offset
% image.block_size)
if partition_size < vbmeta_end_offset + 1 * image.block_size:
raise AvbError('Requested size of {} is too small for an image '
'of size {}.'
.format(partition_size,
vbmeta_end_offset + 1 * image.block_size))
# Cut at the end of the vbmeta blob and insert a DONT_CARE chunk
# with enough bytes such that the final Footer block is at the end
# of partition_size.
image.truncate(vbmeta_end_offset)
image.append_dont_care(partition_size - vbmeta_end_offset -
1 * image.block_size)
# Just reuse the same footer - only difference is that we're
# writing it in a different place.
footer_blob = footer.encode()
footer_blob_with_padding = (b'\0' * (image.block_size - AvbFooter.SIZE) +
footer_blob)
image.append_raw(footer_blob_with_padding)
def set_ab_metadata(self, misc_image, slot_data):
"""Implements the 'set_ab_metadata' command.
The |slot_data| argument must be of the form 'A_priority:A_tries_remaining:
A_successful_boot:B_priority:B_tries_remaining:B_successful_boot'.
Arguments:
misc_image: The misc image to write to.
slot_data: Slot data as a string
Raises:
AvbError: If slot data is malformed.
"""
tokens = slot_data.split(':')
if len(tokens) != 6:
raise AvbError('Malformed slot data "{}".'.format(slot_data))
a_priority = int(tokens[0])
a_tries_remaining = int(tokens[1])
a_success = int(tokens[2]) != 0
b_priority = int(tokens[3])
b_tries_remaining = int(tokens[4])
b_success = int(tokens[5]) != 0
ab_data_no_crc = struct.pack(self.AB_FORMAT_NO_CRC,
self.AB_MAGIC,
self.AB_MAJOR_VERSION, self.AB_MINOR_VERSION,
a_priority, a_tries_remaining, a_success,
b_priority, b_tries_remaining, b_success)
# Force CRC to be unsigned, see https://bugs.python.org/issue4903 for why.
crc_value = binascii.crc32(ab_data_no_crc) & 0xffffffff
ab_data = ab_data_no_crc + struct.pack('!I', crc_value)
misc_image.seek(self.AB_MISC_METADATA_OFFSET)
misc_image.write(ab_data)
def info_image(self, image_filename, output, atx):
"""Implements the 'info_image' command.
Arguments:
image_filename: Image file to get information from (file object).
output: Output file to write human-readable information to (file object).
atx: If True, show information about Android Things eXtension (ATX).
"""
image = ImageHandler(image_filename, read_only=True)
o = output
(footer, header, descriptors, image_size) = self._parse_image(image)
# To show the SHA1 of the public key.
vbmeta_blob = self._load_vbmeta_blob(image)
key_offset = (header.SIZE +
header.authentication_data_block_size +
header.public_key_offset)
key_blob = vbmeta_blob[key_offset:key_offset + header.public_key_size]
if footer:
o.write('Footer version: {}.{}\n'.format(footer.version_major,
footer.version_minor))
o.write('Image size: {} bytes\n'.format(image_size))
o.write('Original image size: {} bytes\n'.format(
footer.original_image_size))
o.write('VBMeta offset: {}\n'.format(footer.vbmeta_offset))
o.write('VBMeta size: {} bytes\n'.format(footer.vbmeta_size))
o.write('--\n')
(alg_name, _) = lookup_algorithm_by_type(header.algorithm_type)
o.write('Minimum libavb version: {}.{}{}\n'.format(
header.required_libavb_version_major,
header.required_libavb_version_minor,
' (Sparse)' if image.is_sparse else ''))
o.write('Header Block: {} bytes\n'.format(AvbVBMetaHeader.SIZE))
o.write('Authentication Block: {} bytes\n'.format(
header.authentication_data_block_size))
o.write('Auxiliary Block: {} bytes\n'.format(
header.auxiliary_data_block_size))
if key_blob:
hexdig = hashlib.sha1(key_blob).hexdigest()
o.write('Public key (sha1): {}\n'.format(hexdig))
o.write('Algorithm: {}\n'.format(alg_name))
o.write('Rollback Index: {}\n'.format(header.rollback_index))
o.write('Flags: {}\n'.format(header.flags))
o.write('Rollback Index Location: {}\n'.format(
header.rollback_index_location))
o.write('Release String: \'{}\'\n'.format(header.release_string))
# Print descriptors.
num_printed = 0
o.write('Descriptors:\n')
for desc in descriptors:
desc.print_desc(o)
num_printed += 1
if num_printed == 0:
o.write(' (none)\n')
if atx and header.public_key_metadata_size:
o.write('Android Things eXtension (ATX):\n')
key_metadata_offset = (header.SIZE +
header.authentication_data_block_size +
header.public_key_metadata_offset)
key_metadata_blob = vbmeta_blob[key_metadata_offset: key_metadata_offset
+ header.public_key_metadata_size]
version, pik, psk = struct.unpack('<I1620s1620s', key_metadata_blob)
o.write(' Metadata version: {}\n'.format(version))
def print_atx_certificate(cert):
version, public_key, subject, usage, key_version, _signature = \
struct.unpack('<I1032s32s32sQ512s', cert)
o.write(' Version: {}\n'.format(version))
o.write(' Public key (sha1): {}\n'.format(
hashlib.sha1(public_key).hexdigest()))
o.write(' Subject: {}\n'.format(subject.hex()))
o.write(' Usage: {}\n'.format(usage.hex()))
o.write(' Key version: {}\n'.format(key_version))
o.write(' Product Intermediate Key:\n')
print_atx_certificate(pik)
o.write(' Product Signing Key:\n')
print_atx_certificate(psk)
def verify_image(self, image_filename, key_path, expected_chain_partitions,
follow_chain_partitions, accept_zeroed_hashtree):
"""Implements the 'verify_image' command.
Arguments:
image_filename: Image file to get information from (file object).
key_path: None or check that embedded public key matches key at given
path.
expected_chain_partitions: List of chain partitions to check or None.
follow_chain_partitions:
If True, will follows chain partitions even when not specified with
the --expected_chain_partition option
accept_zeroed_hashtree: If True, don't fail if hashtree or FEC data is
zeroed out.
Raises:
AvbError: If verification of the image fails.
"""
expected_chain_partitions_map = {}
if expected_chain_partitions:
for cp in expected_chain_partitions:
cp_tokens = cp.split(':')
if len(cp_tokens) != 3:
raise AvbError('Malformed chained partition "{}".'.format(cp))
partition_name = cp_tokens[0]
rollback_index_location = int(cp_tokens[1])
file_path = cp_tokens[2]
with open(file_path, 'rb') as f:
pk_blob = f.read()
expected_chain_partitions_map[partition_name] = (
rollback_index_location, pk_blob)
image_dir = os.path.dirname(image_filename)
image_ext = os.path.splitext(image_filename)[1]
key_blob = None
if key_path:
print('Verifying image {} using key at {}'.format(image_filename,
key_path))
key_blob = RSAPublicKey(key_path).encode()
else:
print('Verifying image {} using embedded public key'.format(
image_filename))
image = ImageHandler(image_filename, read_only=True)
(footer, header, descriptors, _) = self._parse_image(image)
offset = 0
if footer:
offset = footer.vbmeta_offset
image.seek(offset)
vbmeta_blob = image.read(header.SIZE
+ header.authentication_data_block_size
+ header.auxiliary_data_block_size)
alg_name, _ = lookup_algorithm_by_type(header.algorithm_type)
if not verify_vbmeta_signature(header, vbmeta_blob):
raise AvbError('Signature check failed for {} vbmeta struct {}'
.format(alg_name, image_filename))
if key_blob:
# The embedded public key is in the auxiliary block at an offset.
key_offset = AvbVBMetaHeader.SIZE
key_offset += header.authentication_data_block_size
key_offset += header.public_key_offset
key_blob_in_vbmeta = vbmeta_blob[key_offset:key_offset
+ header.public_key_size]
if key_blob != key_blob_in_vbmeta:
raise AvbError('Embedded public key does not match given key.')
if footer:
print('vbmeta: Successfully verified footer and {} vbmeta struct in {}'
.format(alg_name, image.filename))
else:
print('vbmeta: Successfully verified {} vbmeta struct in {}'
.format(alg_name, image.filename))
for desc in descriptors:
if (isinstance(desc, AvbChainPartitionDescriptor)
and follow_chain_partitions
and expected_chain_partitions_map.get(desc.partition_name) is None):
# In this case we're processing a chain descriptor but don't have a
# --expect_chain_partition ... however --follow_chain_partitions was
# specified so we shouldn't error out in desc.verify().
print('{}: Chained but ROLLBACK_SLOT (which is {}) '
'and KEY (which has sha1 {}) not specified'
.format(desc.partition_name, desc.rollback_index_location,
hashlib.sha1(desc.public_key).hexdigest()))
elif not desc.verify(image_dir, image_ext, expected_chain_partitions_map,
image, accept_zeroed_hashtree):
raise AvbError('Error verifying descriptor.')
# Honor --follow_chain_partitions - add '--' to make the output more
# readable.
if (isinstance(desc, AvbChainPartitionDescriptor)
and follow_chain_partitions):
print('--')
chained_image_filename = os.path.join(image_dir,
desc.partition_name + image_ext)
self.verify_image(chained_image_filename, key_path, None, False,
accept_zeroed_hashtree)
def print_partition_digests(self, image_filename, output, as_json):
"""Implements the 'print_partition_digests' command.
Arguments:
image_filename: Image file to get information from (file object).
output: Output file to write human-readable information to (file object).
as_json: If True, print information as JSON
Raises:
AvbError: If getting the partition digests from the image fails.
"""
image_dir = os.path.dirname(image_filename)
image_ext = os.path.splitext(image_filename)[1]
json_partitions = None
if as_json:
json_partitions = []
self._print_partition_digests(
image_filename, output, json_partitions, image_dir, image_ext)
if as_json:
output.write(json.dumps({'partitions': json_partitions}, indent=2))
def _print_partition_digests(self, image_filename, output, json_partitions,
image_dir, image_ext):
"""Helper for printing partitions.
Arguments:
image_filename: Image file to get information from (file object).
output: Output file to write human-readable information to (file object).
json_partitions: If not None, don't print to output, instead add partition
information to this list.
image_dir: The directory to use when looking for chained partition files.
image_ext: The extension to use for chained partition files.
Raises:
AvbError: If getting the partition digests from the image fails.
"""
image = ImageHandler(image_filename, read_only=True)
(_, _, descriptors, _) = self._parse_image(image)
for desc in descriptors:
if isinstance(desc, AvbHashDescriptor):
digest = desc.digest.hex()
if json_partitions is not None:
json_partitions.append({'name': desc.partition_name,
'digest': digest})
else:
output.write('{}: {}\n'.format(desc.partition_name, digest))
elif isinstance(desc, AvbHashtreeDescriptor):
digest = desc.root_digest.hex()
if json_partitions is not None:
json_partitions.append({'name': desc.partition_name,
'digest': digest})
else:
output.write('{}: {}\n'.format(desc.partition_name, digest))
elif isinstance(desc, AvbChainPartitionDescriptor):
chained_image_filename = os.path.join(image_dir,
desc.partition_name + image_ext)
self._print_partition_digests(
chained_image_filename, output, json_partitions, image_dir,
image_ext)
def calculate_vbmeta_digest(self, image_filename, hash_algorithm, output):
"""Implements the 'calculate_vbmeta_digest' command.
Arguments:
image_filename: Image file to get information from (file object).
hash_algorithm: Hash algorithm used.
output: Output file to write human-readable information to (file object).
"""
image_dir = os.path.dirname(image_filename)
image_ext = os.path.splitext(image_filename)[1]
image = ImageHandler(image_filename, read_only=True)
(footer, header, descriptors, _) = self._parse_image(image)
offset = 0
if footer:
offset = footer.vbmeta_offset
size = (header.SIZE + header.authentication_data_block_size +
header.auxiliary_data_block_size)
image.seek(offset)
vbmeta_blob = image.read(size)
hasher = hashlib.new(hash_algorithm)
hasher.update(vbmeta_blob)
for desc in descriptors:
if isinstance(desc, AvbChainPartitionDescriptor):
ch_image_filename = os.path.join(image_dir,
desc.partition_name + image_ext)
ch_image = ImageHandler(ch_image_filename, read_only=True)
(ch_footer, ch_header, _, _) = self._parse_image(ch_image)
ch_offset = 0
ch_size = (ch_header.SIZE + ch_header.authentication_data_block_size +
ch_header.auxiliary_data_block_size)
if ch_footer:
ch_offset = ch_footer.vbmeta_offset
ch_image.seek(ch_offset)
ch_vbmeta_blob = ch_image.read(ch_size)
hasher.update(ch_vbmeta_blob)
digest = hasher.digest()
output.write('{}\n'.format(digest.hex()))
def calculate_kernel_cmdline(self, image_filename, hashtree_disabled, output):
"""Implements the 'calculate_kernel_cmdline' command.
Arguments:
image_filename: Image file to get information from (file object).
hashtree_disabled: If True, returns the cmdline for hashtree disabled.
output: Output file to write human-readable information to (file object).
"""
image = ImageHandler(image_filename, read_only=True)
_, _, descriptors, _ = self._parse_image(image)
image_dir = os.path.dirname(image_filename)
image_ext = os.path.splitext(image_filename)[1]
cmdline_descriptors = []
for desc in descriptors:
if isinstance(desc, AvbChainPartitionDescriptor):
ch_image_filename = os.path.join(image_dir,
desc.partition_name + image_ext)
ch_image = ImageHandler(ch_image_filename, read_only=True)
_, _, ch_descriptors, _ = self._parse_image(ch_image)
for ch_desc in ch_descriptors:
if isinstance(ch_desc, AvbKernelCmdlineDescriptor):
cmdline_descriptors.append(ch_desc)
elif isinstance(desc, AvbKernelCmdlineDescriptor):
cmdline_descriptors.append(desc)
kernel_cmdline_snippets = []
for desc in cmdline_descriptors:
use_cmdline = True
if ((desc.flags &
AvbKernelCmdlineDescriptor.FLAGS_USE_ONLY_IF_HASHTREE_NOT_DISABLED)
!= 0):
if hashtree_disabled:
use_cmdline = False
if (desc.flags &
AvbKernelCmdlineDescriptor.FLAGS_USE_ONLY_IF_HASHTREE_DISABLED) != 0:
if not hashtree_disabled:
use_cmdline = False
if use_cmdline:
kernel_cmdline_snippets.append(desc.kernel_cmdline)
output.write(' '.join(kernel_cmdline_snippets))
def _parse_image(self, image):
"""Gets information about an image.
The image can either be a vbmeta or an image with a footer.
Arguments:
image: An ImageHandler (vbmeta or footer) with a hashtree descriptor.
Returns:
A tuple where the first argument is a AvbFooter (None if there
is no footer on the image), the second argument is a
AvbVBMetaHeader, the third argument is a list of
AvbDescriptor-derived instances, and the fourth argument is the
size of |image|.
Raises:
AvbError: In case the image cannot be parsed.
"""
assert isinstance(image, ImageHandler)
footer = None
image.seek(image.image_size - AvbFooter.SIZE)
try:
footer = AvbFooter(image.read(AvbFooter.SIZE))
except (LookupError, struct.error):
# Nope, just seek back to the start.
image.seek(0)
vbmeta_offset = 0
if footer:
vbmeta_offset = footer.vbmeta_offset
image.seek(vbmeta_offset)
h = AvbVBMetaHeader(image.read(AvbVBMetaHeader.SIZE))
auth_block_offset = vbmeta_offset + AvbVBMetaHeader.SIZE
aux_block_offset = auth_block_offset + h.authentication_data_block_size
desc_start_offset = aux_block_offset + h.descriptors_offset
image.seek(desc_start_offset)
descriptors = parse_descriptors(image.read(h.descriptors_size))
return footer, h, descriptors, image.image_size
def _load_vbmeta_blob(self, image):
"""Gets the vbmeta struct and associated sections.
The image can either be a vbmeta.img or an image with a footer.
Arguments:
image: An ImageHandler (vbmeta or footer).
Returns:
A blob with the vbmeta struct and other sections.
"""
assert isinstance(image, ImageHandler)
footer = None
image.seek(image.image_size - AvbFooter.SIZE)
try:
footer = AvbFooter(image.read(AvbFooter.SIZE))
except (LookupError, struct.error):
# Nope, just seek back to the start.
image.seek(0)
vbmeta_offset = 0
if footer:
vbmeta_offset = footer.vbmeta_offset
image.seek(vbmeta_offset)
h = AvbVBMetaHeader(image.read(AvbVBMetaHeader.SIZE))
image.seek(vbmeta_offset)
data_size = AvbVBMetaHeader.SIZE
data_size += h.authentication_data_block_size
data_size += h.auxiliary_data_block_size
return image.read(data_size)
def _get_cmdline_descriptors_for_hashtree_descriptor(self, ht):
"""Generate kernel cmdline descriptors for dm-verity.
Arguments:
ht: A AvbHashtreeDescriptor
Returns:
A list with two AvbKernelCmdlineDescriptor with dm-verity kernel cmdline
instructions. There is one for when hashtree is not disabled and one for
when it is.
"""
c = 'dm="1 vroot none ro 1,'
c += '0' # start
c += ' {}'.format((ht.image_size // 512)) # size (# sectors)
c += ' verity {}'.format(ht.dm_verity_version) # type and version
c += ' PARTUUID=$(ANDROID_SYSTEM_PARTUUID)' # data_dev
c += ' PARTUUID=$(ANDROID_SYSTEM_PARTUUID)' # hash_dev
c += ' {}'.format(ht.data_block_size) # data_block
c += ' {}'.format(ht.hash_block_size) # hash_block
c += ' {}'.format(ht.image_size // ht.data_block_size) # #blocks
c += ' {}'.format(ht.image_size // ht.data_block_size) # hash_offset
c += ' {}'.format(ht.hash_algorithm) # hash_alg
c += ' {}'.format(ht.root_digest.hex()) # root_digest
c += ' {}'.format(ht.salt.hex()) # salt
if ht.fec_num_roots > 0:
c += ' 10' # number of optional args
c += ' $(ANDROID_VERITY_MODE)'
c += ' ignore_zero_blocks'
c += ' use_fec_from_device PARTUUID=$(ANDROID_SYSTEM_PARTUUID)'
c += ' fec_roots {}'.format(ht.fec_num_roots)
# Note that fec_blocks is the size that FEC covers, *not* the
# size of the FEC data. Since we use FEC for everything up until
# the FEC data, it's the same as the offset.
c += ' fec_blocks {}'.format(ht.fec_offset // ht.data_block_size)
c += ' fec_start {}'.format(ht.fec_offset // ht.data_block_size)
else:
c += ' 2' # number of optional args
c += ' $(ANDROID_VERITY_MODE)'
c += ' ignore_zero_blocks'
c += '" root=/dev/dm-0'
# Now that we have the command-line, generate the descriptor.
desc = AvbKernelCmdlineDescriptor()
desc.kernel_cmdline = c
desc.flags = (
AvbKernelCmdlineDescriptor.FLAGS_USE_ONLY_IF_HASHTREE_NOT_DISABLED)
# The descriptor for when hashtree verification is disabled is a lot
# simpler - we just set the root to the partition.
desc_no_ht = AvbKernelCmdlineDescriptor()
desc_no_ht.kernel_cmdline = 'root=PARTUUID=$(ANDROID_SYSTEM_PARTUUID)'
desc_no_ht.flags = (
AvbKernelCmdlineDescriptor.FLAGS_USE_ONLY_IF_HASHTREE_DISABLED)
return [desc, desc_no_ht]
def _get_cmdline_descriptors_for_dm_verity(self, image):
"""Generate kernel cmdline descriptors for dm-verity.
Arguments:
image: An ImageHandler (vbmeta or footer) with a hashtree descriptor.
Returns:
A list with two AvbKernelCmdlineDescriptor with dm-verity kernel cmdline
instructions. There is one for when hashtree is not disabled and one for
when it is.
Raises:
AvbError: If |image| doesn't have a hashtree descriptor.
"""
(_, _, descriptors, _) = self._parse_image(image)
ht = None
for desc in descriptors:
if isinstance(desc, AvbHashtreeDescriptor):
ht = desc
break
if not ht:
raise AvbError('No hashtree descriptor in given image')
return self._get_cmdline_descriptors_for_hashtree_descriptor(ht)
def make_vbmeta_image(self, output, chain_partitions, algorithm_name,
key_path, public_key_metadata_path, rollback_index,
flags, rollback_index_location,
props, props_from_file, kernel_cmdlines,
setup_rootfs_from_kernel,
include_descriptors_from_image,
signing_helper,
signing_helper_with_files,
release_string,
append_to_release_string,
print_required_libavb_version,
padding_size):
"""Implements the 'make_vbmeta_image' command.
Arguments:
output: File to write the image to.
chain_partitions: List of partitions to chain or None.
algorithm_name: Name of algorithm to use.
key_path: Path to key to use or None.
public_key_metadata_path: Path to public key metadata or None.
rollback_index: The rollback index to use.
flags: Flags value to use in the image.
rollback_index_location: Location of the main vbmeta rollback index.
props: Properties to insert (list of strings of the form 'key:value').
props_from_file: Properties to insert (list of strings 'key:<path>').
kernel_cmdlines: Kernel cmdlines to insert (list of strings).
setup_rootfs_from_kernel: None or file to generate from.
include_descriptors_from_image: List of file objects with descriptors.
signing_helper: Program which signs a hash and return signature.
signing_helper_with_files: Same as signing_helper but uses files instead.
release_string: None or avbtool release string to use instead of default.
append_to_release_string: None or string to append.
print_required_libavb_version: True to only print required libavb version.
padding_size: If not 0, pads output so size is a multiple of the number.
Raises:
AvbError: If a chained partition is malformed.
"""
# If we're asked to calculate minimum required libavb version, we're done.
tmp_header = AvbVBMetaHeader()
if rollback_index_location > 0:
tmp_header.bump_required_libavb_version_minor(2)
if include_descriptors_from_image:
# Use the bump logic in AvbVBMetaHeader to calculate the max required
# version of all included descriptors.
for image in include_descriptors_from_image:
(_, image_header, _, _) = self._parse_image(ImageHandler(
image.name, read_only=True))
tmp_header.bump_required_libavb_version_minor(
image_header.required_libavb_version_minor)
if print_required_libavb_version:
print('1.{}'.format(tmp_header.required_libavb_version_minor))
return
if not output:
raise AvbError('No output file given')
descriptors = []
ht_desc_to_setup = None
vbmeta_blob = self._generate_vbmeta_blob(
algorithm_name, key_path, public_key_metadata_path, descriptors,
chain_partitions, rollback_index, flags, rollback_index_location,
props, props_from_file,
kernel_cmdlines, setup_rootfs_from_kernel, ht_desc_to_setup,
include_descriptors_from_image, signing_helper,
signing_helper_with_files, release_string,
append_to_release_string, tmp_header.required_libavb_version_minor)
# Write entire vbmeta blob (header, authentication, auxiliary).
output.seek(0)
output.write(vbmeta_blob)
if padding_size > 0:
padded_size = round_to_multiple(len(vbmeta_blob), padding_size)
padding_needed = padded_size - len(vbmeta_blob)
output.write(b'\0' * padding_needed)
def _generate_vbmeta_blob(self, algorithm_name, key_path,
public_key_metadata_path, descriptors,
chain_partitions,
rollback_index, flags, rollback_index_location,
props, props_from_file,
kernel_cmdlines,
setup_rootfs_from_kernel,
ht_desc_to_setup,
include_descriptors_from_image, signing_helper,
signing_helper_with_files,
release_string, append_to_release_string,
required_libavb_version_minor):
"""Generates a VBMeta blob.
This blob contains the header (struct AvbVBMetaHeader), the
authentication data block (which contains the hash and signature
for the header and auxiliary block), and the auxiliary block
(which contains descriptors, the public key used, and other data).
The |key| parameter can |None| only if the |algorithm_name| is
'NONE'.
Arguments:
algorithm_name: The algorithm name as per the ALGORITHMS dict.
key_path: The path to the .pem file used to sign the blob.
public_key_metadata_path: Path to public key metadata or None.
descriptors: A list of descriptors to insert or None.
chain_partitions: List of partitions to chain or None.
rollback_index: The rollback index to use.
flags: Flags to use in the image.
rollback_index_location: Location of the main vbmeta rollback index.
props: Properties to insert (List of strings of the form 'key:value').
props_from_file: Properties to insert (List of strings 'key:<path>').
kernel_cmdlines: Kernel cmdlines to insert (list of strings).
setup_rootfs_from_kernel: None or file to generate
dm-verity kernel cmdline from.
ht_desc_to_setup: If not None, an AvbHashtreeDescriptor to
generate dm-verity kernel cmdline descriptors from.
include_descriptors_from_image: List of file objects for which
to insert descriptors from.
signing_helper: Program which signs a hash and return signature.
signing_helper_with_files: Same as signing_helper but uses files instead.
release_string: None or avbtool release string.
append_to_release_string: None or string to append.
required_libavb_version_minor: Use at least this required minor version.
Returns:
The VBMeta blob as bytes.
Raises:
Exception: If the |algorithm_name| is not found, if no key has
been given and the given algorithm requires one, or the key is
of the wrong size.
"""
try:
alg = ALGORITHMS[algorithm_name]
except KeyError:
raise AvbError('Unknown algorithm with name {}'.format(algorithm_name))
if not descriptors:
descriptors = []
h = AvbVBMetaHeader()
h.bump_required_libavb_version_minor(required_libavb_version_minor)
# Insert chained partition descriptors, if any
if chain_partitions:
used_locations = {rollback_index_location: True}
for cp in chain_partitions:
cp_tokens = cp.split(':')
if len(cp_tokens) != 3:
raise AvbError('Malformed chained partition "{}".'.format(cp))
partition_name = cp_tokens[0]
chained_rollback_index_location = int(cp_tokens[1])
file_path = cp_tokens[2]
# Check that the same rollback location isn't being used by
# multiple chained partitions.
if used_locations.get(chained_rollback_index_location):
raise AvbError('Rollback Index Location {} is already in use.'.format(
chained_rollback_index_location))
used_locations[chained_rollback_index_location] = True
desc = AvbChainPartitionDescriptor()
desc.partition_name = partition_name
desc.rollback_index_location = chained_rollback_index_location
if desc.rollback_index_location < 1:
raise AvbError('Rollback index location must be 1 or larger.')
with open(file_path, 'rb') as f:
desc.public_key = f.read()
descriptors.append(desc)
# Descriptors.
encoded_descriptors = bytearray()
for desc in descriptors:
encoded_descriptors.extend(desc.encode())
# Add properties.
if props:
for prop in props:
idx = prop.find(':')
if idx == -1:
raise AvbError('Malformed property "{}".'.format(prop))
# pylint: disable=redefined-variable-type
desc = AvbPropertyDescriptor()
desc.key = prop[0:idx]
desc.value = prop[(idx + 1):].encode('utf-8')
encoded_descriptors.extend(desc.encode())
if props_from_file:
for prop in props_from_file:
idx = prop.find(':')
if idx == -1:
raise AvbError('Malformed property "{}".'.format(prop))
desc = AvbPropertyDescriptor()
desc.key = prop[0:idx]
file_path = prop[(idx + 1):]
with open(file_path, 'rb') as f:
# pylint: disable=attribute-defined-outside-init
desc.value = f.read()
encoded_descriptors.extend(desc.encode())
# Add AvbKernelCmdline descriptor for dm-verity from an image, if requested.
if setup_rootfs_from_kernel:
image_handler = ImageHandler(
setup_rootfs_from_kernel.name)
cmdline_desc = self._get_cmdline_descriptors_for_dm_verity(image_handler)
encoded_descriptors.extend(cmdline_desc[0].encode())
encoded_descriptors.extend(cmdline_desc[1].encode())
# Add AvbKernelCmdline descriptor for dm-verity from desc, if requested.
if ht_desc_to_setup:
cmdline_desc = self._get_cmdline_descriptors_for_hashtree_descriptor(
ht_desc_to_setup)
encoded_descriptors.extend(cmdline_desc[0].encode())
encoded_descriptors.extend(cmdline_desc[1].encode())
# Add kernel command-lines.
if kernel_cmdlines:
for i in kernel_cmdlines:
desc = AvbKernelCmdlineDescriptor()
desc.kernel_cmdline = i
encoded_descriptors.extend(desc.encode())
# Add descriptors from other images.
if include_descriptors_from_image:
descriptors_dict = dict()
for image in include_descriptors_from_image:
image_handler = ImageHandler(image.name, read_only=True)
(_, image_vbmeta_header, image_descriptors, _) = self._parse_image(
image_handler)
# Bump the required libavb version to support all included descriptors.
h.bump_required_libavb_version_minor(
image_vbmeta_header.required_libavb_version_minor)
for desc in image_descriptors:
# The --include_descriptors_from_image option is used in some setups
# with images A and B where both A and B contain a descriptor
# for a partition with the same name. Since it's not meaningful
# to include both descriptors, only include the last seen descriptor.
# See bug 76386656 for details.
if hasattr(desc, 'partition_name'):
key = type(desc).__name__ + '_' + desc.partition_name
descriptors_dict[key] = desc.encode()
else:
encoded_descriptors.extend(desc.encode())
for key in sorted(descriptors_dict):
encoded_descriptors.extend(descriptors_dict[key])
# Load public key metadata blob, if requested.
pkmd_blob = b''
if public_key_metadata_path:
with open(public_key_metadata_path, 'rb') as f:
pkmd_blob = f.read()
key = None
encoded_key = b''
if alg.public_key_num_bytes > 0:
if not key_path:
raise AvbError('Key is required for algorithm {}'.format(
algorithm_name))
encoded_key = RSAPublicKey(key_path).encode()
if len(encoded_key) != alg.public_key_num_bytes:
raise AvbError('Key is wrong size for algorithm {}'.format(
algorithm_name))
# Override release string, if requested.
if isinstance(release_string, str):
h.release_string = release_string
# Append to release string, if requested. Also insert a space before.
if isinstance(append_to_release_string, str):
h.release_string += ' ' + append_to_release_string
# For the Auxiliary data block, descriptors are stored at offset 0,
# followed by the public key, followed by the public key metadata blob.
h.auxiliary_data_block_size = round_to_multiple(
len(encoded_descriptors) + len(encoded_key) + len(pkmd_blob), 64)
h.descriptors_offset = 0
h.descriptors_size = len(encoded_descriptors)
h.public_key_offset = h.descriptors_size
h.public_key_size = len(encoded_key)
h.public_key_metadata_offset = h.public_key_offset + h.public_key_size
h.public_key_metadata_size = len(pkmd_blob)
# For the Authentication data block, the hash is first and then
# the signature.
h.authentication_data_block_size = round_to_multiple(
alg.hash_num_bytes + alg.signature_num_bytes, 64)
h.algorithm_type = alg.algorithm_type
h.hash_offset = 0
h.hash_size = alg.hash_num_bytes
# Signature offset and size - it's stored right after the hash
# (in Authentication data block).
h.signature_offset = alg.hash_num_bytes
h.signature_size = alg.signature_num_bytes
h.rollback_index = rollback_index
h.flags = flags
h.rollback_index_location = rollback_index_location
# Generate Header data block.
header_data_blob = h.encode()
# Generate Auxiliary data block.
aux_data_blob = bytearray()
aux_data_blob.extend(encoded_descriptors)
aux_data_blob.extend(encoded_key)
aux_data_blob.extend(pkmd_blob)
padding_bytes = h.auxiliary_data_block_size - len(aux_data_blob)
aux_data_blob.extend(b'\0' * padding_bytes)
# Calculate the hash.
binary_hash = b''
binary_signature = b''
if algorithm_name != 'NONE':
ha = hashlib.new(alg.hash_name)
ha.update(header_data_blob)
ha.update(aux_data_blob)
binary_hash = ha.digest()
# Calculate the signature.
rsa_key = RSAPublicKey(key_path)
data_to_sign = header_data_blob + bytes(aux_data_blob)
binary_signature = rsa_key.sign(algorithm_name, data_to_sign,
signing_helper, signing_helper_with_files)
# Generate Authentication data block.
auth_data_blob = bytearray()
auth_data_blob.extend(binary_hash)
auth_data_blob.extend(binary_signature)
padding_bytes = h.authentication_data_block_size - len(auth_data_blob)
auth_data_blob.extend(b'\0' * padding_bytes)
return header_data_blob + bytes(auth_data_blob) + bytes(aux_data_blob)
def extract_public_key(self, key_path, output):
"""Implements the 'extract_public_key' command.
Arguments:
key_path: The path to a RSA private key file.
output: The file to write to.
Raises:
AvbError: If the public key could not be extracted.
"""
output.write(RSAPublicKey(key_path).encode())
def append_vbmeta_image(self, image_filename, vbmeta_image_filename,
partition_size):
"""Implementation of the append_vbmeta_image command.
Arguments:
image_filename: File to add the footer to.
vbmeta_image_filename: File to get vbmeta struct from.
partition_size: Size of partition.
Raises:
AvbError: If an argument is incorrect or if appending VBMeta image fialed.
"""
image = ImageHandler(image_filename)
if partition_size % image.block_size != 0:
raise AvbError('Partition size of {} is not a multiple of the image '
'block size {}.'.format(partition_size,
image.block_size))
# If there's already a footer, truncate the image to its original
# size. This way 'avbtool append_vbmeta_image' is idempotent.
if image.image_size >= AvbFooter.SIZE:
image.seek(image.image_size - AvbFooter.SIZE)
try:
footer = AvbFooter(image.read(AvbFooter.SIZE))
# Existing footer found. Just truncate.
original_image_size = footer.original_image_size
image.truncate(footer.original_image_size)
except (LookupError, struct.error):
original_image_size = image.image_size
else:
# Image size is too small to possibly contain a footer.
original_image_size = image.image_size
# If anything goes wrong from here-on, restore the image back to
# its original size.
try:
vbmeta_image_handler = ImageHandler(vbmeta_image_filename)
vbmeta_blob = self._load_vbmeta_blob(vbmeta_image_handler)
# If the image isn't sparse, its size might not be a multiple of
# the block size. This will screw up padding later so just grow it.
if image.image_size % image.block_size != 0:
assert not image.is_sparse
padding_needed = image.block_size - (image.image_size%image.block_size)
image.truncate(image.image_size + padding_needed)
# The append_raw() method requires content with size being a
# multiple of |block_size| so add padding as needed. Also record
# where this is written to since we'll need to put that in the
# footer.
vbmeta_offset = image.image_size
padding_needed = (round_to_multiple(len(vbmeta_blob), image.block_size) -
len(vbmeta_blob))
vbmeta_blob_with_padding = vbmeta_blob + b'\0' * padding_needed
# Append vbmeta blob and footer
image.append_raw(vbmeta_blob_with_padding)
vbmeta_end_offset = vbmeta_offset + len(vbmeta_blob_with_padding)
# Now insert a DONT_CARE chunk with enough bytes such that the
# final Footer block is at the end of partition_size..
image.append_dont_care(partition_size - vbmeta_end_offset -
1 * image.block_size)
# Generate the Footer that tells where the VBMeta footer
# is. Also put enough padding in the front of the footer since
# we'll write out an entire block.
footer = AvbFooter()
footer.original_image_size = original_image_size
footer.vbmeta_offset = vbmeta_offset
footer.vbmeta_size = len(vbmeta_blob)
footer_blob = footer.encode()
footer_blob_with_padding = (b'\0' * (image.block_size - AvbFooter.SIZE) +
footer_blob)
image.append_raw(footer_blob_with_padding)
except Exception as e:
# Truncate back to original size, then re-raise.
image.truncate(original_image_size)
raise AvbError('Appending VBMeta image failed: {}.'.format(e))
def add_hash_footer(self, image_filename, partition_size, partition_name,
hash_algorithm, salt, chain_partitions, algorithm_name,
key_path,
public_key_metadata_path, rollback_index, flags,
rollback_index_location, props,
props_from_file, kernel_cmdlines,
setup_rootfs_from_kernel,
include_descriptors_from_image, calc_max_image_size,
signing_helper, signing_helper_with_files,
release_string, append_to_release_string,
output_vbmeta_image, do_not_append_vbmeta_image,
print_required_libavb_version, use_persistent_digest,
do_not_use_ab):
"""Implementation of the add_hash_footer on unsparse images.
Arguments:
image_filename: File to add the footer to.
partition_size: Size of partition.
partition_name: Name of partition (without A/B suffix).
hash_algorithm: Hash algorithm to use.
salt: Salt to use as a hexadecimal string or None to use /dev/urandom.
chain_partitions: List of partitions to chain.
algorithm_name: Name of algorithm to use.
key_path: Path to key to use or None.
public_key_metadata_path: Path to public key metadata or None.
rollback_index: Rollback index.
flags: Flags value to use in the image.
rollback_index_location: Location of the main vbmeta rollback index.
props: Properties to insert (List of strings of the form 'key:value').
props_from_file: Properties to insert (List of strings 'key:<path>').
kernel_cmdlines: Kernel cmdlines to insert (list of strings).
setup_rootfs_from_kernel: None or file to generate
dm-verity kernel cmdline from.
include_descriptors_from_image: List of file objects for which
to insert descriptors from.
calc_max_image_size: Don't store the footer - instead calculate the
maximum image size leaving enough room for metadata with the
given |partition_size|.
signing_helper: Program which signs a hash and return signature.
signing_helper_with_files: Same as signing_helper but uses files instead.
release_string: None or avbtool release string.
append_to_release_string: None or string to append.
output_vbmeta_image: If not None, also write vbmeta struct to this file.
do_not_append_vbmeta_image: If True, don't append vbmeta struct.
print_required_libavb_version: True to only print required libavb version.
use_persistent_digest: Use a persistent digest on device.
do_not_use_ab: This partition does not use A/B.
Raises:
AvbError: If an argument is incorrect of if adding of hash_footer failed.
"""
required_libavb_version_minor = 0
if use_persistent_digest or do_not_use_ab:
required_libavb_version_minor = 1
if rollback_index_location > 0:
required_libavb_version_minor = 2
# If we're asked to calculate minimum required libavb version, we're done.
if print_required_libavb_version:
print('1.{}'.format(required_libavb_version_minor))
return
# First, calculate the maximum image size such that an image
# this size + metadata (footer + vbmeta struct) fits in
# |partition_size|.
max_metadata_size = self.MAX_VBMETA_SIZE + self.MAX_FOOTER_SIZE
if partition_size < max_metadata_size:
raise AvbError('Parition size of {} is too small. '
'Needs to be at least {}'.format(
partition_size, max_metadata_size))
max_image_size = partition_size - max_metadata_size
# If we're asked to only calculate the maximum image size, we're done.
if calc_max_image_size:
print('{}'.format(max_image_size))
return
image = ImageHandler(image_filename)
if partition_size % image.block_size != 0:
raise AvbError('Partition size of {} is not a multiple of the image '
'block size {}.'.format(partition_size,
image.block_size))
# If there's already a footer, truncate the image to its original
# size. This way 'avbtool add_hash_footer' is idempotent (modulo
# salts).
if image.image_size >= AvbFooter.SIZE:
image.seek(image.image_size - AvbFooter.SIZE)
try:
footer = AvbFooter(image.read(AvbFooter.SIZE))
# Existing footer found. Just truncate.
original_image_size = footer.original_image_size
image.truncate(footer.original_image_size)
except (LookupError, struct.error):
original_image_size = image.image_size
else:
# Image size is too small to possibly contain a footer.
original_image_size = image.image_size
# If anything goes wrong from here-on, restore the image back to
# its original size.
try:
# If image size exceeds the maximum image size, fail.
if image.image_size > max_image_size:
raise AvbError('Image size of {} exceeds maximum image '
'size of {} in order to fit in a partition '
'size of {}.'.format(image.image_size, max_image_size,
partition_size))
digest_size = len(hashlib.new(hash_algorithm).digest())
if salt:
salt = binascii.unhexlify(salt)
elif salt is None and not use_persistent_digest:
# If salt is not explicitly specified, choose a hash that's the same
# size as the hash size. Don't populate a random salt if this
# descriptor is being created to use a persistent digest on device.
hash_size = digest_size
with open('/dev/urandom', 'rb') as f:
salt = f.read(hash_size)
else:
salt = b''
hasher = hashlib.new(hash_algorithm, salt)
# TODO(zeuthen): might want to read this in chunks to avoid
# memory pressure, then again, this is only supposed to be used
# on kernel/initramfs partitions. Possible optimization.
image.seek(0)
hasher.update(image.read(image.image_size))
digest = hasher.digest()
h_desc = AvbHashDescriptor()
h_desc.image_size = image.image_size
h_desc.hash_algorithm = hash_algorithm
h_desc.partition_name = partition_name
h_desc.salt = salt
h_desc.flags = 0
if do_not_use_ab:
h_desc.flags |= 1 # AVB_HASH_DESCRIPTOR_FLAGS_DO_NOT_USE_AB
if not use_persistent_digest:
h_desc.digest = digest
# Generate the VBMeta footer.
ht_desc_to_setup = None
vbmeta_blob = self._generate_vbmeta_blob(
algorithm_name, key_path, public_key_metadata_path, [h_desc],
chain_partitions, rollback_index, flags, rollback_index_location,
props, props_from_file,
kernel_cmdlines, setup_rootfs_from_kernel, ht_desc_to_setup,
include_descriptors_from_image, signing_helper,
signing_helper_with_files, release_string,
append_to_release_string, required_libavb_version_minor)
# Write vbmeta blob, if requested.
if output_vbmeta_image:
output_vbmeta_image.write(vbmeta_blob)
# Append vbmeta blob and footer, unless requested not to.
if not do_not_append_vbmeta_image:
# If the image isn't sparse, its size might not be a multiple of
# the block size. This will screw up padding later so just grow it.
if image.image_size % image.block_size != 0:
assert not image.is_sparse
padding_needed = image.block_size - (
image.image_size % image.block_size)
image.truncate(image.image_size + padding_needed)
# The append_raw() method requires content with size being a
# multiple of |block_size| so add padding as needed. Also record
# where this is written to since we'll need to put that in the
# footer.
vbmeta_offset = image.image_size
padding_needed = (
round_to_multiple(len(vbmeta_blob), image.block_size) -
len(vbmeta_blob))
vbmeta_blob_with_padding = vbmeta_blob + b'\0' * padding_needed
image.append_raw(vbmeta_blob_with_padding)
vbmeta_end_offset = vbmeta_offset + len(vbmeta_blob_with_padding)
# Now insert a DONT_CARE chunk with enough bytes such that the
# final Footer block is at the end of partition_size..
image.append_dont_care(partition_size - vbmeta_end_offset -
1 * image.block_size)
# Generate the Footer that tells where the VBMeta footer
# is. Also put enough padding in the front of the footer since
# we'll write out an entire block.
footer = AvbFooter()
footer.original_image_size = original_image_size
footer.vbmeta_offset = vbmeta_offset
footer.vbmeta_size = len(vbmeta_blob)
footer_blob = footer.encode()
footer_blob_with_padding = (
b'\0' * (image.block_size - AvbFooter.SIZE) + footer_blob)
image.append_raw(footer_blob_with_padding)
except Exception as e:
# Truncate back to original size, then re-raise.
image.truncate(original_image_size)
raise AvbError('Adding hash_footer failed: {}.'.format(e))
def add_hashtree_footer(self, image_filename, partition_size, partition_name,
generate_fec, fec_num_roots, hash_algorithm,
block_size, salt, chain_partitions, algorithm_name,
key_path,
public_key_metadata_path, rollback_index, flags,
rollback_index_location,
props, props_from_file, kernel_cmdlines,
setup_rootfs_from_kernel,
setup_as_rootfs_from_kernel,
include_descriptors_from_image,
calc_max_image_size, signing_helper,
signing_helper_with_files,
release_string, append_to_release_string,
output_vbmeta_image, do_not_append_vbmeta_image,
print_required_libavb_version,
use_persistent_root_digest, do_not_use_ab,
no_hashtree):
"""Implements the 'add_hashtree_footer' command.
See https://gitlab.com/cryptsetup/cryptsetup/wikis/DMVerity for
more information about dm-verity and these hashes.
Arguments:
image_filename: File to add the footer to.
partition_size: Size of partition or 0 to put it right at the end.
partition_name: Name of partition (without A/B suffix).
generate_fec: If True, generate FEC codes.
fec_num_roots: Number of roots for FEC.
hash_algorithm: Hash algorithm to use.
block_size: Block size to use.
salt: Salt to use as a hexadecimal string or None to use /dev/urandom.
chain_partitions: List of partitions to chain.
algorithm_name: Name of algorithm to use.
key_path: Path to key to use or None.
public_key_metadata_path: Path to public key metadata or None.
rollback_index: Rollback index.
flags: Flags value to use in the image.
rollback_index_location: Location of the main vbmeta rollback index.
props: Properties to insert (List of strings of the form 'key:value').
props_from_file: Properties to insert (List of strings 'key:<path>').
kernel_cmdlines: Kernel cmdlines to insert (list of strings).
setup_rootfs_from_kernel: None or file to generate
dm-verity kernel cmdline from.
setup_as_rootfs_from_kernel: If True, generate dm-verity kernel
cmdline to set up rootfs.
include_descriptors_from_image: List of file objects for which
to insert descriptors from.
calc_max_image_size: Don't store the hashtree or footer - instead
calculate the maximum image size leaving enough room for hashtree
and metadata with the given |partition_size|.
signing_helper: Program which signs a hash and return signature.
signing_helper_with_files: Same as signing_helper but uses files instead.
release_string: None or avbtool release string.
append_to_release_string: None or string to append.
output_vbmeta_image: If not None, also write vbmeta struct to this file.
do_not_append_vbmeta_image: If True, don't append vbmeta struct.
print_required_libavb_version: True to only print required libavb version.
use_persistent_root_digest: Use a persistent root digest on device.
do_not_use_ab: The partition does not use A/B.
no_hashtree: Do not append hashtree. Set size in descriptor as zero.
Raises:
AvbError: If an argument is incorrect or adding the hashtree footer
failed.
"""
required_libavb_version_minor = 0
if use_persistent_root_digest or do_not_use_ab:
required_libavb_version_minor = 1
if rollback_index_location > 0:
required_libavb_version_minor = 2
# If we're asked to calculate minimum required libavb version, we're done.
if print_required_libavb_version:
print('1.{}'.format(required_libavb_version_minor))
return
digest_size = len(hashlib.new(hash_algorithm).digest())
digest_padding = round_to_pow2(digest_size) - digest_size
# If |partition_size| is given (e.g. not 0), calculate the maximum image
# size such that an image this size + the hashtree + metadata (footer +
# vbmeta struct) fits in |partition_size|. We use very conservative figures
# for metadata.
if partition_size > 0:
max_tree_size = 0
max_fec_size = 0
if not no_hashtree:
(_, max_tree_size) = calc_hash_level_offsets(
partition_size, block_size, digest_size + digest_padding)
if generate_fec:
max_fec_size = calc_fec_data_size(partition_size, fec_num_roots)
max_metadata_size = (max_fec_size + max_tree_size +
self.MAX_VBMETA_SIZE +
self.MAX_FOOTER_SIZE)
max_image_size = partition_size - max_metadata_size
else:
max_image_size = 0
# If we're asked to only calculate the maximum image size, we're done.
if calc_max_image_size:
print('{}'.format(max_image_size))
return
image = ImageHandler(image_filename)
if partition_size > 0:
if partition_size % image.block_size != 0:
raise AvbError('Partition size of {} is not a multiple of the image '
'block size {}.'.format(partition_size,
image.block_size))
elif image.image_size % image.block_size != 0:
raise AvbError('File size of {} is not a multiple of the image '
'block size {}.'.format(image.image_size,
image.block_size))
# If there's already a footer, truncate the image to its original
# size. This way 'avbtool add_hashtree_footer' is idempotent
# (modulo salts).
if image.image_size >= AvbFooter.SIZE:
image.seek(image.image_size - AvbFooter.SIZE)
try: