#!/usr/bin/env python # 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 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 = 1 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 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_header.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, 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=[]), '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=[ # 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=[ # 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=[ # 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=[ # 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=[ # 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=[ # 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. Args: 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. Args: 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: value: 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) else: 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 else: 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 = '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. """ # 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.modulus = int(modulus_hexstr, 16) self.num_bits = round_to_pow2(int(math.ceil(math.log(self.modulus, 2)))) self.exponent = 65537 def encode_rsa_key(key_path): """Encodes a public RSA key in |AvbRSAPublicKeyHeader| format. This creates a |AvbRSAPublicKeyHeader| as well as the two large numbers (|key_num_bits| bits long) following it. Arguments: key_path: The path to a key file. Returns: A bytearray() with the |AvbRSAPublicKeyHeader|. """ key = RSAPublicKey(key_path) if key.exponent != 65537: raise AvbError('Only RSA keys with exponent 65537 are supported.') ret = bytearray() # Calculate n0inv = -1/n[0] (mod 2^32) b = 2L**32 n0inv = b - modinv(key.modulus, b) # Calculate rr = r^2 (mod N), where r = 2^(# of key bits) r = 2L**key.modulus.bit_length() rrmodn = r * r % key.modulus ret.extend(struct.pack('!II', key.num_bits, n0inv)) ret.extend(encode_long(key.num_bits, key.modulus)) ret.extend(encode_long(key.num_bits, rrmodn)) return ret 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 raw_sign(signing_helper, signing_helper_with_files, algorithm_name, signature_num_bytes, key_path, raw_data_to_sign): """Computes a raw RSA signature using |signing_helper| or openssl. Arguments: signing_helper: Program which signs a hash and returns the signature. signing_helper_with_files: Same as signing_helper but uses files instead. algorithm_name: The algorithm name as per the ALGORITHMS dict. signature_num_bytes: Number of bytes used to store the signature. key_path: Path to the private key file. Must be PEM format. raw_data_to_sign: Data to sign (bytearray or str expected). Returns: A bytearray containing the signature. Raises: Exception: If an error occurs. """ p = None if signing_helper_with_files is not None: signing_file = tempfile.NamedTemporaryFile() signing_file.write(str(raw_data_to_sign)) signing_file.flush() p = subprocess.Popen( [signing_helper_with_files, algorithm_name, key_path, signing_file.name]) retcode = p.wait() if retcode != 0: raise AvbError('Error signing') signing_file.seek(0) signature = bytearray(signing_file.read()) else: if signing_helper is not None: p = subprocess.Popen( [signing_helper, algorithm_name, key_path], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE) else: p = subprocess.Popen( ['openssl', 'rsautl', '-sign', '-inkey', key_path, '-raw'], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE) (pout, perr) = p.communicate(str(raw_data_to_sign)) retcode = p.wait() if retcode != 0: raise AvbError('Error signing: {}'.format(perr)) signature = bytearray(pout) if len(signature) != signature_num_bytes: raise AvbError('Error signing: Invalid length of signature') return signature def verify_vbmeta_signature(vbmeta_header, vbmeta_blob): """Checks that the 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. Returns: True if the signature is valid and corresponds to the embedded public key. Also returns True if the vbmeta blob is not signed. """ (_, alg) = lookup_algorithm_by_type(vbmeta_header.algorithm_type) if 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 = bytearray(alg.padding) padding_and_digest.extend(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 # For now, just use Crypto.PublicKey.RSA to verify the signature. This # is OK since 'avbtool verify_image' is not expected to run on the # Android builders (see bug #36809096). 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 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 with data to fill if TYPE_FILL otherwise None. Raises: ValueError: If data is not well-formed. """ 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: 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 = ' 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. """ assert num_bytes % self.block_size == 0 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. """ assert len(data) % self.block_size == 0 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. """ assert len(fill_data) == 4 assert size % 4 == 0 assert size % self.block_size == 0 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. """ if offset < 0: raise RuntimeError("Seeking with negative offset: %d" % 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. """ 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('\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 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. """ 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 elif 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): """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). Returns: True if the descriptor verifies, False otherwise. """ # 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. value: The key. """ 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 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, 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.') self.key = data[self.SIZE:(self.SIZE + key_size)] self.value = data[(self.SIZE + key_size + 1):(self.SIZE + key_size + 1 + value_size)] else: self.key = '' self.value = '' def print_desc(self, o): """Print the descriptor. Arguments: o: The object to write the output to. """ if len(self.value) < 256: o.write(' Prop: {} -> {}\n'.format(self.key, repr(str(self.value)))) else: o.write(' Prop: {} -> ({} bytes)\n'.format(self.key, len(self.value))) def encode(self): """Serializes the descriptor. Returns: A bytearray() with the descriptor data. """ num_bytes_following = self.SIZE + len(self.key) + 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(self.key), len(self.value)) padding = struct.pack(str(padding_size) + 'x') ret = desc + self.key + '\0' + self.value + '\0' + padding return bytearray(ret) def verify(self, image_dir, image_ext, expected_chain_partitions_map): """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). 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. partition_name: Partition name. salt: Salt used. root_digest: Root digest. 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 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.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.split('\0', 1)[0] o = 0 self.partition_name = str(data[(self.SIZE + o):(self.SIZE + o + partition_name_len)]) # Validate UTF-8 - decode() raises UnicodeDecodeError if not valid UTF-8. self.partition_name.decode('utf-8') 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(name=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 = bytearray() self.root_digest = bytearray() 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(str(self.salt).encode( 'hex'))) o.write(' Root Digest: {}\n'.format(str( self.root_digest).encode('hex'))) o.write(' Flags: {}\n'.format(self.flags)) def encode(self): """Serializes the descriptor. Returns: A bytearray() with the descriptor data. """ encoded_name = self.partition_name.encode('utf-8') num_bytes_following = (self.SIZE + len(encoded_name) + 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, self.hash_algorithm, len(encoded_name), len(self.salt), len(self.root_digest), self.flags, self.RESERVED*'\0') padding = struct.pack(str(padding_size) + 'x') ret = desc + encoded_name + self.salt + self.root_digest + padding return bytearray(ret) def verify(self, image_dir, image_ext, expected_chain_partitions_map): """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). Returns: True if the descriptor verifies, False otherwise. """ image_filename = os.path.join(image_dir, self.partition_name + image_ext) image = ImageHandler(image_filename) # Generate the hashtree and checks that it matches what's in the file. digest_size = len(hashlib.new(name=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 len(self.root_digest) != 0 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) if hash_tree != hash_tree_ondisk: sys.stderr.write('hashtree of {} contains invalid data\n'. format(image_filename)) return False # TODO: 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. print ('{}: Successfully verified {} hashtree of {} for image of {} bytes' .format(self.partition_name, self.hash_algorithm, image_filename, self.image_size)) 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. partition_name: Partition name. salt: Salt used. digest: The hash value of salt and data combined. 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 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.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.split('\0', 1)[0] o = 0 self.partition_name = str(data[(self.SIZE + o):(self.SIZE + o + partition_name_len)]) # Validate UTF-8 - decode() raises UnicodeDecodeError if not valid UTF-8. self.partition_name.decode('utf-8') 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(name=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 = bytearray() self.digest = bytearray() 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(str(self.salt).encode( 'hex'))) o.write(' Digest: {}\n'.format(str(self.digest).encode( 'hex'))) o.write(' Flags: {}\n'.format(self.flags)) def encode(self): """Serializes the descriptor. Returns: A bytearray() with the descriptor data. """ encoded_name = self.partition_name.encode('utf-8') num_bytes_following = ( self.SIZE + len(encoded_name) + 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, self.hash_algorithm, len(encoded_name), len(self.salt), len(self.digest), self.flags, self.RESERVED*'\0') padding = struct.pack(str(padding_size) + 'x') ret = desc + encoded_name + self.salt + self.digest + padding return bytearray(ret) def verify(self, image_dir, image_ext, expected_chain_partitions_map): """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). Returns: True if the descriptor verifies, False otherwise. """ image_filename = os.path.join(image_dir, self.partition_name + image_ext) image = ImageHandler(image_filename) 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 len(self.digest) != 0 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. """ 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 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.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. self.kernel_cmdline = str(data[self.SIZE:(self.SIZE + kernel_cmdline_length)]) # Validate UTF-8 - decode() raises UnicodeDecodeError if not valid UTF-8. self.kernel_cmdline.decode('utf-8') 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(repr( self.kernel_cmdline))) def encode(self): """Serializes the descriptor. Returns: A bytearray() with the descriptor data. """ encoded_str = self.kernel_cmdline.encode('utf-8') num_bytes_following = (self.SIZE + len(encoded_str) - 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(encoded_str)) padding = struct.pack(str(padding_size) + 'x') ret = desc + encoded_str + padding return bytearray(ret) def verify(self, image_dir, image_ext, expected_chain_partitions_map): """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). 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. public_key: Bytes for the public key. """ 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 self.partition_name = str(data[(self.SIZE + o):(self.SIZE + o + partition_name_len)]) # Validate UTF-8 - decode() raises UnicodeDecodeError if not valid UTF-8. self.partition_name.decode('utf-8') 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 = bytearray() 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. hexdig = hashlib.sha1(self.public_key).hexdigest() o.write(' Public key (sha1): {}\n'.format(hexdig)) def encode(self): """Serializes the descriptor. Returns: A bytearray() with the descriptor data. """ encoded_name = self.partition_name.encode('utf-8') num_bytes_following = ( self.SIZE + len(encoded_name) + 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(encoded_name), len(self.public_key), self.RESERVED*'\0') padding = struct.pack(str(padding_size) + 'x') ret = desc + encoded_name + self.public_key + padding return bytearray(ret) def verify(self, image_dir, image_ext, expected_chain_partitions_map): """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). 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.\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: A bytearray() with encoded descriptors. 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): c = DESCRIPTOR_CLASSES[tag] else: c = AvbDescriptor ret.append(c(bytearray(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 = '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 a bytearray 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): """Gets a string representing the binary encoding of the footer. Returns: A bytearray() with a binary representation of the footer. """ 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. Attributes: The attributes correspond to the |AvbVBMetaHeader| struct defined in avb_vbmeta_header.h. """ SIZE = 256 # Keep in sync with |reserved0| and |reserved| field of # |AvbVBMetaImageHeader|. RESERVED0 = 4 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 str(RESERVED0) + 'x' + # padding for reserved bytes '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.release_string) = struct.unpack(self.FORMAT_STRING, data) # Nuke NUL-bytes at the end of the string. if self.magic != 'AVB0': raise AvbError('Given image does not look like a vbmeta image.') else: self.magic = 'AVB0' # 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.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 save(self, output): """Serializes the header (256 bytes) to disk. Arguments: output: The object to write the output to. """ output.write(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.release_string)) def encode(self): """Serializes the header (256) to a bytearray(). Returns: A bytearray() with the encoded header. """ 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.release_string) 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 = '\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 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 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, vbmeta_header, descriptors, _) = 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 = ('\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 = True if int(tokens[2]) != 0 else False b_priority = int(tokens[3]) b_tries_remaining = int(tokens[4]) b_success = True if int(tokens[5]) != 0 else False 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): """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). """ image = ImageHandler(image_filename) o = output (footer, header, descriptors, image_size) = self._parse_image(image) 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)) 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('Release String: \'{}\'\n'.format( header.release_string.rstrip('\0'))) # 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') def verify_image(self, image_filename, key_path, expected_chain_partitions): """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. """ expected_chain_partitions_map = {} if expected_chain_partitions: used_locations = {} 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] pk_blob = open(file_path).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 = encode_rsa_key(key_path) else: print 'Verifying image {} using embedded public key'.format(image_filename) image = ImageHandler(image_filename) (footer, header, descriptors, image_size) = 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) h = AvbVBMetaHeader(vbmeta_blob[0:AvbVBMetaHeader.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 += h.authentication_data_block_size key_offset += h.public_key_offset key_blob_in_vbmeta = vbmeta_blob[key_offset:key_offset + h.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 not desc.verify(image_dir, image_ext, expected_chain_partitions_map): raise AvbError('Error verifying descriptor.') 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|. """ 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(str(ht.root_digest).encode('hex')) # root_digest c += ' {}'.format(str(ht.salt).encode('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, 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. props: Properties to insert (list of strings of the form 'key:value'). props_from_file: Properties to insert (list of strings 'key:'). 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. if print_required_libavb_version: if include_descriptors_from_image: # Use the bump logic in AvbVBMetaHeader to calculate the max required # version of all included descriptors. tmp_header = AvbVBMetaHeader() for image in include_descriptors_from_image: (_, image_header, _, _) = self._parse_image(ImageHandler(image.name)) tmp_header.bump_required_libavb_version_minor( image_header.required_libavb_version_minor) print '1.{}'.format(tmp_header.required_libavb_version_minor) else: # Descriptors aside, all vbmeta features are supported in 1.0. print '1.0' 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, 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, 0) # 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('\0' * padding_needed) def _generate_vbmeta_blob(self, algorithm_name, key_path, public_key_metadata_path, descriptors, chain_partitions, rollback_index, flags, 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. props: Properties to insert (List of strings of the form 'key:value'). props_from_file: Properties to insert (List of strings 'key:'). 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: A bytearray() with the VBMeta blob. 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 = {} 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] 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(rollback_index_location): raise AvbError('Rollback Index Location {} is already in use.'.format( rollback_index_location)) used_locations[rollback_index_location] = True desc = AvbChainPartitionDescriptor() desc.partition_name = partition_name desc.rollback_index_location = rollback_index_location if desc.rollback_index_location < 1: raise AvbError('Rollback index location must be 1 or larger.') desc.public_key = open(file_path, 'rb').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)) desc = AvbPropertyDescriptor() desc.key = prop[0:idx] desc.value = prop[(idx + 1):] 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] desc.value = prop[(idx + 1):] file_path = prop[(idx + 1):] desc.value = open(file_path, 'rb').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: for image in include_descriptors_from_image: image_handler = ImageHandler(image.name) (_, 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: encoded_descriptors.extend(desc.encode()) # Load public key metadata blob, if requested. pkmd_blob = [] if public_key_metadata_path: with open(public_key_metadata_path) as f: pkmd_blob = f.read() key = None encoded_key = bytearray() if alg.public_key_num_bytes > 0: if not key_path: raise AvbError('Key is required for algorithm {}'.format( algorithm_name)) encoded_key = encode_rsa_key(key_path) 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, unicode)): h.release_string = release_string # Append to release string, if requested. Also insert a space before. if isinstance(append_to_release_string, (str, unicode)): 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 # 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('\0' * padding_bytes) # Calculate the hash. binary_hash = bytearray() binary_signature = bytearray() if algorithm_name != 'NONE': ha = hashlib.new(alg.hash_name) ha.update(header_data_blob) ha.update(aux_data_blob) binary_hash.extend(ha.digest()) # Calculate the signature. padding_and_hash = str(bytearray(alg.padding)) + binary_hash binary_signature.extend(raw_sign(signing_helper, signing_helper_with_files, algorithm_name, alg.signature_num_bytes, key_path, padding_and_hash)) # 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('\0' * padding_bytes) return header_data_blob + auth_data_blob + 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. """ output.write(encode_rsa_key(key_path)) 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. """ 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 + '\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 = ('\0'*(image.block_size - AvbFooter.SIZE) + footer_blob) image.append_raw(footer_blob_with_padding) except: # Truncate back to original size, then re-raise image.truncate(original_image_size) raise 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, 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. props: Properties to insert (List of strings of the form 'key:value'). props_from_file: Properties to insert (List of strings 'key:'). 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. """ required_libavb_version_minor = 0 if use_persistent_digest or do_not_use_ab: required_libavb_version_minor = 1 # 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(name=hash_algorithm).digest()) if salt: salt = salt.decode('hex') else: if salt is None: # If salt is not explicitly specified, choose a hash # that's the same size as the hash size. hash_size = digest_size salt = open('/dev/urandom').read(hash_size) else: salt = '' hasher = hashlib.new(name=hash_algorithm, string=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, 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 + '\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 = ('\0'*(image.block_size - AvbFooter.SIZE) + footer_blob) image.append_raw(footer_blob_with_padding) except: # Truncate back to original size, then re-raise image.truncate(original_image_size) raise 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, 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): """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. 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. props: Properties to insert (List of strings of the form 'key:value'). props_from_file: Properties to insert (List of strings 'key:'). 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. Raises: AvbError: If an argument is incorrect. """ required_libavb_version_minor = 0 if use_persistent_root_digest or do_not_use_ab: required_libavb_version_minor = 1 # 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(name=hash_algorithm).digest()) digest_padding = round_to_pow2(digest_size) - digest_size # First, 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. (_, max_tree_size) = calc_hash_level_offsets( partition_size, block_size, digest_size + digest_padding) max_fec_size = 0 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 # 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_hashtree_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: # Ensure image is multiple of block_size. rounded_image_size = round_to_multiple(image.image_size, block_size) if rounded_image_size > image.image_size: image.append_raw('\0' * (rounded_image_size - image.image_size)) # 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)) if salt: salt = salt.decode('hex') else: if salt is None: # If salt is not explicitly specified, choose a hash # that's the same size as the hash size. hash_size = digest_size salt = open('/dev/urandom').read(hash_size) else: salt = '' # Hashes are stored upside down so we need to calculate hash # offsets in advance. (hash_level_offsets, tree_size) = calc_hash_level_offsets( image.image_size, block_size, digest_size + digest_padding) # 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) # Generate the tree and add padding as needed. tree_offset = image.image_size root_digest, hash_tree = generate_hash_tree(image, image.image_size, block_size, hash_algorithm, salt, digest_padding, hash_level_offsets, tree_size) # Generate HashtreeDescriptor with details about the tree we # just generated. ht_desc = AvbHashtreeDescriptor() ht_desc.dm_verity_version = 1 ht_desc.image_size = image.image_size ht_desc.tree_offset = tree_offset ht_desc.tree_size = tree_size ht_desc.data_block_size = block_size ht_desc.hash_block_size = block_size ht_desc.hash_algorithm = hash_algorithm ht_desc.partition_name = partition_name ht_desc.salt = salt if do_not_use_ab: ht_desc.flags |= 1 # AVB_HASHTREE_DESCRIPTOR_FLAGS_DO_NOT_USE_AB if not use_persistent_root_digest: ht_desc.root_digest = root_digest # Write the hash tree padding_needed = (round_to_multiple(len(hash_tree), image.block_size) - len(hash_tree)) hash_tree_with_padding = hash_tree + '\0'*padding_needed image.append_raw(hash_tree_with_padding) len_hashtree_and_fec = len(hash_tree_with_padding) # Generate FEC codes, if requested. if generate_fec: fec_data = generate_fec_data(image_filename, fec_num_roots) padding_needed = (round_to_multiple(len(fec_data), image.block_size) - len(fec_data)) fec_data_with_padding = fec_data + '\0'*padding_needed fec_offset = image.image_size image.append_raw(fec_data_with_padding) len_hashtree_and_fec += len(fec_data_with_padding) # Update the hashtree descriptor. ht_desc.fec_num_roots = fec_num_roots ht_desc.fec_offset = fec_offset ht_desc.fec_size = len(fec_data) ht_desc_to_setup = None if setup_as_rootfs_from_kernel: ht_desc_to_setup = ht_desc # Generate the VBMeta footer and add padding as needed. vbmeta_offset = tree_offset + len_hashtree_and_fec vbmeta_blob = self._generate_vbmeta_blob( algorithm_name, key_path, public_key_metadata_path, [ht_desc], chain_partitions, rollback_index, flags, 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) padding_needed = (round_to_multiple(len(vbmeta_blob), image.block_size) - len(vbmeta_blob)) vbmeta_blob_with_padding = vbmeta_blob + '\0'*padding_needed # 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: image.append_raw(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 - image.image_size - 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 = ('\0'*(image.block_size - AvbFooter.SIZE) + footer_blob) image.append_raw(footer_blob_with_padding) except: # Truncate back to original size, then re-raise. image.truncate(original_image_size) raise def make_atx_certificate(self, output, authority_key_path, subject_key_path, subject_key_version, subject, is_intermediate_authority, signing_helper, signing_helper_with_files): """Implements the 'make_atx_certificate' command. Android Things certificates are required for Android Things public key metadata. They chain the vbmeta signing key for a particular product back to a fused, permanent root key. These certificates are fixed-length and fixed- format with the explicit goal of not parsing ASN.1 in bootloader code. Arguments: output: Certificate will be written to this file on success. authority_key_path: A PEM file path with the authority private key. If None, then a certificate will be created without a signature. The signature can be created out-of-band and appended. subject_key_path: Path to a PEM or DER subject public key. subject_key_version: A 64-bit version value. If this is None, the number of seconds since the epoch is used. subject: A subject identifier. For Product Signing Key certificates this should be the same Product ID found in the permanent attributes. is_intermediate_authority: True if the certificate is for an intermediate authority. signing_helper: Program which signs a hash and returns the signature. signing_helper_with_files: Same as signing_helper but uses files instead. """ signed_data = bytearray() signed_data.extend(struct.pack(' block_size: num_blocks = (size + block_size - 1) / block_size level_size = round_to_multiple(num_blocks * digest_size, block_size) level_sizes.append(level_size) tree_size += level_size num_levels += 1 size = level_size for n in range(0, num_levels): offset = 0 for m in range(n + 1, num_levels): offset += level_sizes[m] level_offsets.append(offset) return level_offsets, tree_size # See system/extras/libfec/include/fec/io.h for these definitions. FEC_FOOTER_FORMAT = ' block_size: level_output = '' remaining = hash_src_size while remaining > 0: hasher = hashlib.new(name=hash_alg_name, string=salt) # Only read from the file for the first level - for subsequent # levels, access the array we're building. if level_num == 0: image.seek(hash_src_offset + hash_src_size - remaining) data = image.read(min(remaining, block_size)) else: offset = hash_level_offsets[level_num - 1] + hash_src_size - remaining data = hash_ret[offset:offset + block_size] hasher.update(data) remaining -= len(data) if len(data) < block_size: hasher.update('\0' * (block_size - len(data))) level_output += hasher.digest() if digest_padding > 0: level_output += '\0' * digest_padding padding_needed = (round_to_multiple( len(level_output), block_size) - len(level_output)) level_output += '\0' * padding_needed # Copy level-output into resulting tree. offset = hash_level_offsets[level_num] hash_ret[offset:offset + len(level_output)] = level_output # Continue on to the next level. hash_src_size = len(level_output) level_num += 1 hasher = hashlib.new(name=hash_alg_name, string=salt) hasher.update(level_output) return hasher.digest(), hash_ret class AvbTool(object): """Object for avbtool command-line tool.""" def __init__(self): """Initializer method.""" self.avb = Avb() def _add_common_args(self, sub_parser): """Adds arguments used by several sub-commands. Arguments: sub_parser: The parser to add arguments to. """ sub_parser.add_argument('--algorithm', help='Algorithm to use (default: NONE)', metavar='ALGORITHM', default='NONE') sub_parser.add_argument('--key', help='Path to RSA private key file', metavar='KEY', required=False) sub_parser.add_argument('--signing_helper', help='Path to helper used for signing', metavar='APP', default=None, required=False) sub_parser.add_argument('--signing_helper_with_files', help='Path to helper used for signing using files', metavar='APP', default=None, required=False) sub_parser.add_argument('--public_key_metadata', help='Path to public key metadata file', metavar='KEY_METADATA', required=False) sub_parser.add_argument('--rollback_index', help='Rollback Index', type=parse_number, default=0) # This is used internally for unit tests. Do not include in --help output. sub_parser.add_argument('--internal_release_string', help=argparse.SUPPRESS) sub_parser.add_argument('--append_to_release_string', help='Text to append to release string', metavar='STR') sub_parser.add_argument('--prop', help='Add property', metavar='KEY:VALUE', action='append') sub_parser.add_argument('--prop_from_file', help='Add property from file', metavar='KEY:PATH', action='append') sub_parser.add_argument('--kernel_cmdline', help='Add kernel cmdline', metavar='CMDLINE', action='append') # TODO(zeuthen): the --setup_rootfs_from_kernel option used to be called # --generate_dm_verity_cmdline_from_hashtree. Remove support for the latter # at some future point. sub_parser.add_argument('--setup_rootfs_from_kernel', '--generate_dm_verity_cmdline_from_hashtree', metavar='IMAGE', help='Adds kernel cmdline to set up IMAGE', type=argparse.FileType('rb')) sub_parser.add_argument('--include_descriptors_from_image', help='Include descriptors from image', metavar='IMAGE', action='append', type=argparse.FileType('rb')) sub_parser.add_argument('--print_required_libavb_version', help=('Don\'t store the footer - ' 'instead calculate the required libavb ' 'version for the given options.'), action='store_true') # These are only allowed from top-level vbmeta and boot-in-lieu-of-vbmeta. sub_parser.add_argument('--chain_partition', help='Allow signed integrity-data for partition', metavar='PART_NAME:ROLLBACK_SLOT:KEY_PATH', action='append') sub_parser.add_argument('--flags', help='VBMeta flags', type=parse_number, default=0) sub_parser.add_argument('--set_hashtree_disabled_flag', help='Set the HASHTREE_DISABLED flag', action='store_true') def _add_common_footer_args(self, sub_parser): """Adds arguments used by add_*_footer sub-commands. Arguments: sub_parser: The parser to add arguments to. """ sub_parser.add_argument('--use_persistent_digest', help='Use a persistent digest on device instead of ' 'storing the digest in the descriptor. This ' 'cannot be used with A/B so must be combined ' 'with --do_not_use_ab when an A/B suffix is ' 'expected at runtime.', action='store_true') sub_parser.add_argument('--do_not_use_ab', help='The partition does not use A/B even when an ' 'A/B suffix is present. This must not be used ' 'for vbmeta or chained partitions.', action='store_true') def _fixup_common_args(self, args): """Common fixups needed by subcommands. Arguments: args: Arguments to modify. Returns: The modified arguments. """ if args.set_hashtree_disabled_flag: args.flags |= AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED return args def run(self, argv): """Command-line processor. Arguments: argv: Pass sys.argv from main. """ parser = argparse.ArgumentParser() subparsers = parser.add_subparsers(title='subcommands') sub_parser = subparsers.add_parser('version', help='Prints version of avbtool.') sub_parser.set_defaults(func=self.version) sub_parser = subparsers.add_parser('extract_public_key', help='Extract public key.') sub_parser.add_argument('--key', help='Path to RSA private key file', required=True) sub_parser.add_argument('--output', help='Output file name', type=argparse.FileType('wb'), required=True) sub_parser.set_defaults(func=self.extract_public_key) sub_parser = subparsers.add_parser('make_vbmeta_image', help='Makes a vbmeta image.') sub_parser.add_argument('--output', help='Output file name', type=argparse.FileType('wb')) sub_parser.add_argument('--padding_size', metavar='NUMBER', help='If non-zero, pads output with NUL bytes so ' 'its size is a multiple of NUMBER (default: 0)', type=parse_number, default=0) self._add_common_args(sub_parser) sub_parser.set_defaults(func=self.make_vbmeta_image) sub_parser = subparsers.add_parser('add_hash_footer', help='Add hashes and footer to image.') sub_parser.add_argument('--image', help='Image to add hashes to', type=argparse.FileType('rab+')) sub_parser.add_argument('--partition_size', help='Partition size', type=parse_number) sub_parser.add_argument('--partition_name', help='Partition name', default=None) sub_parser.add_argument('--hash_algorithm', help='Hash algorithm to use (default: sha256)', default='sha256') sub_parser.add_argument('--salt', help='Salt in hex (default: /dev/urandom)') sub_parser.add_argument('--calc_max_image_size', help=('Don\'t store the footer - ' 'instead calculate the maximum image size ' 'leaving enough room for metadata with ' 'the given partition size.'), action='store_true') sub_parser.add_argument('--output_vbmeta_image', help='Also write vbmeta struct to file', type=argparse.FileType('wb')) sub_parser.add_argument('--do_not_append_vbmeta_image', help=('Do not append vbmeta struct or footer ' 'to the image'), action='store_true') self._add_common_args(sub_parser) self._add_common_footer_args(sub_parser) sub_parser.set_defaults(func=self.add_hash_footer) sub_parser = subparsers.add_parser('append_vbmeta_image', help='Append vbmeta image to image.') sub_parser.add_argument('--image', help='Image to append vbmeta blob to', type=argparse.FileType('rab+')) sub_parser.add_argument('--partition_size', help='Partition size', type=parse_number, required=True) sub_parser.add_argument('--vbmeta_image', help='Image with vbmeta blob to append', type=argparse.FileType('rb')) sub_parser.set_defaults(func=self.append_vbmeta_image) sub_parser = subparsers.add_parser('add_hashtree_footer', help='Add hashtree and footer to image.') sub_parser.add_argument('--image', help='Image to add hashtree to', type=argparse.FileType('rab+')) sub_parser.add_argument('--partition_size', help='Partition size', type=parse_number) sub_parser.add_argument('--partition_name', help='Partition name', default=None) sub_parser.add_argument('--hash_algorithm', help='Hash algorithm to use (default: sha1)', default='sha1') sub_parser.add_argument('--salt', help='Salt in hex (default: /dev/urandom)') sub_parser.add_argument('--block_size', help='Block size (default: 4096)', type=parse_number, default=4096) # TODO(zeuthen): The --generate_fec option was removed when we # moved to generating FEC by default. To avoid breaking existing # users needing to transition we simply just print a warning below # in add_hashtree_footer(). Remove this option and the warning at # some point in the future. sub_parser.add_argument('--generate_fec', help=argparse.SUPPRESS, action='store_true') sub_parser.add_argument('--do_not_generate_fec', help='Do not generate forward-error-correction codes', action='store_true') sub_parser.add_argument('--fec_num_roots', help='Number of roots for FEC (default: 2)', type=parse_number, default=2) sub_parser.add_argument('--calc_max_image_size', help=('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.'), action='store_true') sub_parser.add_argument('--output_vbmeta_image', help='Also write vbmeta struct to file', type=argparse.FileType('wb')) sub_parser.add_argument('--do_not_append_vbmeta_image', help=('Do not append vbmeta struct or footer ' 'to the image'), action='store_true') # This is different from --setup_rootfs_from_kernel insofar that # it doesn't take an IMAGE, the generated cmdline will be for the # hashtree we're adding. sub_parser.add_argument('--setup_as_rootfs_from_kernel', action='store_true', help='Adds kernel cmdline for setting up rootfs') self._add_common_args(sub_parser) self._add_common_footer_args(sub_parser) sub_parser.set_defaults(func=self.add_hashtree_footer) sub_parser = subparsers.add_parser('erase_footer', help='Erase footer from an image.') sub_parser.add_argument('--image', help='Image with a footer', type=argparse.FileType('rwb+'), required=True) sub_parser.add_argument('--keep_hashtree', help='Keep the hashtree and FEC in the image', action='store_true') sub_parser.set_defaults(func=self.erase_footer) sub_parser = subparsers.add_parser('resize_image', help='Resize image with a footer.') sub_parser.add_argument('--image', help='Image with a footer', type=argparse.FileType('rwb+'), required=True) sub_parser.add_argument('--partition_size', help='New partition size', type=parse_number) sub_parser.set_defaults(func=self.resize_image) sub_parser = subparsers.add_parser( 'info_image', help='Show information about vbmeta or footer.') sub_parser.add_argument('--image', help='Image to show information about', type=argparse.FileType('rb'), required=True) sub_parser.add_argument('--output', help='Write info to file', type=argparse.FileType('wt'), default=sys.stdout) sub_parser.set_defaults(func=self.info_image) sub_parser = subparsers.add_parser( 'verify_image', help='Verify an image.') sub_parser.add_argument('--image', help='Image to verify', type=argparse.FileType('rb'), required=True) sub_parser.add_argument('--key', help='Check embedded public key matches KEY', metavar='KEY', required=False) sub_parser.add_argument('--expected_chain_partition', help='Expected chain partition', metavar='PART_NAME:ROLLBACK_SLOT:KEY_PATH', action='append') sub_parser.set_defaults(func=self.verify_image) sub_parser = subparsers.add_parser('set_ab_metadata', help='Set A/B metadata.') sub_parser.add_argument('--misc_image', help=('The misc image to modify. If the image does ' 'not exist, it will be created.'), type=argparse.FileType('r+b'), required=True) sub_parser.add_argument('--slot_data', help=('Slot data of the form "priority", ' '"tries_remaining", "sucessful_boot" for ' 'slot A followed by the same for slot B, ' 'separated by colons. The default value ' 'is 15:7:0:14:7:0.'), default='15:7:0:14:7:0') sub_parser.set_defaults(func=self.set_ab_metadata) sub_parser = subparsers.add_parser( 'make_atx_certificate', help='Create an Android Things eXtension (ATX) certificate.') sub_parser.add_argument('--output', help='Write certificate to file', type=argparse.FileType('wb'), default=sys.stdout) sub_parser.add_argument('--subject', help=('Path to subject file'), type=argparse.FileType('rb'), required=True) sub_parser.add_argument('--subject_key', help=('Path to subject RSA public key file'), type=argparse.FileType('rb'), required=True) sub_parser.add_argument('--subject_key_version', help=('Version of the subject key'), type=parse_number, required=False) sub_parser.add_argument('--subject_is_intermediate_authority', help=('Generate an intermediate authority ' 'certificate'), action='store_true') sub_parser.add_argument('--authority_key', help='Path to authority RSA private key file', required=False) sub_parser.add_argument('--signing_helper', help='Path to helper used for signing', metavar='APP', default=None, required=False) sub_parser.add_argument('--signing_helper_with_files', help='Path to helper used for signing using files', metavar='APP', default=None, required=False) sub_parser.set_defaults(func=self.make_atx_certificate) sub_parser = subparsers.add_parser( 'make_atx_permanent_attributes', help='Create Android Things eXtension (ATX) permanent attributes.') sub_parser.add_argument('--output', help='Write attributes to file', type=argparse.FileType('wb'), default=sys.stdout) sub_parser.add_argument('--root_authority_key', help='Path to authority RSA public key file', type=argparse.FileType('rb'), required=True) sub_parser.add_argument('--product_id', help=('Path to Product ID file'), type=argparse.FileType('rb'), required=True) sub_parser.set_defaults(func=self.make_atx_permanent_attributes) sub_parser = subparsers.add_parser( 'make_atx_metadata', help='Create Android Things eXtension (ATX) metadata.') sub_parser.add_argument('--output', help='Write metadata to file', type=argparse.FileType('wb'), default=sys.stdout) sub_parser.add_argument('--intermediate_key_certificate', help='Path to intermediate key certificate file', type=argparse.FileType('rb'), required=True) sub_parser.add_argument('--product_key_certificate', help='Path to product key certificate file', type=argparse.FileType('rb'), required=True) sub_parser.set_defaults(func=self.make_atx_metadata) args = parser.parse_args(argv[1:]) try: args.func(args) except AvbError as e: sys.stderr.write('{}: {}\n'.format(argv[0], e.message)) sys.exit(1) def version(self, _): """Implements the 'version' sub-command.""" print get_release_string() def extract_public_key(self, args): """Implements the 'extract_public_key' sub-command.""" self.avb.extract_public_key(args.key, args.output) def make_vbmeta_image(self, args): """Implements the 'make_vbmeta_image' sub-command.""" args = self._fixup_common_args(args) self.avb.make_vbmeta_image(args.output, args.chain_partition, args.algorithm, args.key, args.public_key_metadata, args.rollback_index, args.flags, args.prop, args.prop_from_file, args.kernel_cmdline, args.setup_rootfs_from_kernel, args.include_descriptors_from_image, args.signing_helper, args.signing_helper_with_files, args.internal_release_string, args.append_to_release_string, args.print_required_libavb_version, args.padding_size) def append_vbmeta_image(self, args): """Implements the 'append_vbmeta_image' sub-command.""" self.avb.append_vbmeta_image(args.image.name, args.vbmeta_image.name, args.partition_size) def add_hash_footer(self, args): """Implements the 'add_hash_footer' sub-command.""" args = self._fixup_common_args(args) self.avb.add_hash_footer(args.image.name if args.image else None, args.partition_size, args.partition_name, args.hash_algorithm, args.salt, args.chain_partition, args.algorithm, args.key, args.public_key_metadata, args.rollback_index, args.flags, args.prop, args.prop_from_file, args.kernel_cmdline, args.setup_rootfs_from_kernel, args.include_descriptors_from_image, args.calc_max_image_size, args.signing_helper, args.signing_helper_with_files, args.internal_release_string, args.append_to_release_string, args.output_vbmeta_image, args.do_not_append_vbmeta_image, args.print_required_libavb_version, args.use_persistent_digest, args.do_not_use_ab) def add_hashtree_footer(self, args): """Implements the 'add_hashtree_footer' sub-command.""" args = self._fixup_common_args(args) # TODO(zeuthen): Remove when removing support for the # '--generate_fec' option above. if args.generate_fec: sys.stderr.write('The --generate_fec option is deprecated since FEC ' 'is now generated by default. Use the option ' '--do_not_generate_fec to not generate FEC.\n') self.avb.add_hashtree_footer(args.image.name if args.image else None, args.partition_size, args.partition_name, not args.do_not_generate_fec, args.fec_num_roots, args.hash_algorithm, args.block_size, args.salt, args.chain_partition, args.algorithm, args.key, args.public_key_metadata, args.rollback_index, args.flags, args.prop, args.prop_from_file, args.kernel_cmdline, args.setup_rootfs_from_kernel, args.setup_as_rootfs_from_kernel, args.include_descriptors_from_image, args.calc_max_image_size, args.signing_helper, args.signing_helper_with_files, args.internal_release_string, args.append_to_release_string, args.output_vbmeta_image, args.do_not_append_vbmeta_image, args.print_required_libavb_version, args.use_persistent_digest, args.do_not_use_ab) def erase_footer(self, args): """Implements the 'erase_footer' sub-command.""" self.avb.erase_footer(args.image.name, args.keep_hashtree) def resize_image(self, args): """Implements the 'resize_image' sub-command.""" self.avb.resize_image(args.image.name, args.partition_size) def set_ab_metadata(self, args): """Implements the 'set_ab_metadata' sub-command.""" self.avb.set_ab_metadata(args.misc_image, args.slot_data) def info_image(self, args): """Implements the 'info_image' sub-command.""" self.avb.info_image(args.image.name, args.output) def verify_image(self, args): """Implements the 'verify_image' sub-command.""" self.avb.verify_image(args.image.name, args.key, args.expected_chain_partition) def make_atx_certificate(self, args): """Implements the 'make_atx_certificate' sub-command.""" self.avb.make_atx_certificate(args.output, args.authority_key, args.subject_key.name, args.subject_key_version, args.subject.read(), args.subject_is_intermediate_authority, args.signing_helper, args.signing_helper_with_files) def make_atx_permanent_attributes(self, args): """Implements the 'make_atx_permanent_attributes' sub-command.""" self.avb.make_atx_permanent_attributes(args.output, args.root_authority_key.name, args.product_id.read()) def make_atx_metadata(self, args): """Implements the 'make_atx_metadata' sub-command.""" self.avb.make_atx_metadata(args.output, args.intermediate_key_certificate.read(), args.product_key_certificate.read()) if __name__ == '__main__': tool = AvbTool() tool.run(sys.argv)