verity/build_verity_metadata.py

   1 #! /usr/bin/env python
   2 #
   3 # Copyright (C) 2013 The Android Open Source Project
   4 #
   5 # Licensed under the Apache License, Version 2.0 (the "License");
   6 # you may not use this file except in compliance with the License.
   7 # You may obtain a copy of the License at
   8 #
   9 #      http://www.apache.org/licenses/LICENSE-2.0
  10 #
  11 # Unless required by applicable law or agreed to in writing, software
  12 # distributed under the License is distributed on an "AS IS" BASIS,
  13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14 # See the License for the specific language governing permissions and
  15 # limitations under the License.
  16
  17 import argparse
  18 import os
  19 import sys
  20 import struct
  21 import shlex
  22 import subprocess
  23 import tempfile
  24
  25 VERSION = 0
  26 MAGIC_NUMBER = 0xb001b001
  27 BLOCK_SIZE = 4096
  28 METADATA_SIZE = BLOCK_SIZE * 8
  29
  30 def run(cmd):
  31     p = subprocess.Popen(cmd, stdout=subprocess.PIPE)
  32     output, _ = p.communicate()
  33     print output
  34     if p.returncode:
  35         exit(-1)
  36
  37 def get_verity_metadata_size(data_size):
  38     return METADATA_SIZE
  39
  40 def build_metadata_block(verity_table, signature):
  41     table_len = len(verity_table)
  42     block = struct.pack("II256sI", MAGIC_NUMBER, VERSION, signature, table_len)
  43     block += verity_table
  44     block = block.ljust(METADATA_SIZE, '\x00')
  45     return block
  46
  47 def sign_verity_table(table, signer_path, key_path, signer_args=None):
  48     with tempfile.NamedTemporaryFile(suffix='.table') as table_file:
  49         with tempfile.NamedTemporaryFile(suffix='.sig') as signature_file:
  50             table_file.write(table)
  51             table_file.flush()
  52             if signer_args is None:
  53               cmd = [signer_path, table_file.name, key_path, signature_file.name]
  54             else:
  55               args_list = shlex.split(signer_args)
  56               cmd = [signer_path] + args_list + [table_file.name, key_path, signature_file.name]
  57             print cmd
  58             run(cmd)
  59             return signature_file.read()
  60
  61 def build_verity_table(block_device, data_blocks, root_hash, salt):
  62     table = "1 %s %s %s %s %s %s sha256 %s %s"
  63     table %= (  block_device,
  64                 block_device,
  65                 BLOCK_SIZE,
  66                 BLOCK_SIZE,
  67                 data_blocks,
  68                 data_blocks,
  69                 root_hash,
  70                 salt)
  71     return table
  72
  73 def build_verity_metadata(data_blocks, metadata_image, root_hash, salt,
  74         block_device, signer_path, signing_key, signer_args=None):
  75     # build the verity table
  76     verity_table = build_verity_table(block_device, data_blocks, root_hash, salt)
  77     # build the verity table signature
  78     signature = sign_verity_table(verity_table, signer_path, signing_key, signer_args)
  79     # build the metadata block
  80     metadata_block = build_metadata_block(verity_table, signature)
  81     # write it to the outfile
  82     with open(metadata_image, "wb") as f:
  83         f.write(metadata_block)
  84
  85 if __name__ == "__main__":
  86     parser = argparse.ArgumentParser()
  87     subparsers = parser.add_subparsers()
  88
  89     parser_size = subparsers.add_parser('size')
  90     parser_size.add_argument('partition_size', type=int, action='store', help='partition size')
  91     parser_size.set_defaults(dest='size')
  92
  93     parser_build = subparsers.add_parser('build')
  94     parser_build.add_argument('blocks', type=int, help='data image blocks')
  95     parser_build.add_argument('metadata_image', action='store', help='metadata image')
  96     parser_build.add_argument('root_hash', action='store', help='root hash')
  97     parser_build.add_argument('salt', action='store', help='salt')
  98     parser_build.add_argument('block_device', action='store', help='block device')
  99     parser_build.add_argument('signer_path', action='store', help='verity signer path')
 100     parser_build.add_argument('signing_key', action='store', help='verity signing key')
 101     parser_build.add_argument('--signer_args', action='store', help='verity signer args')
 102     parser_build.set_defaults(dest='build')
 103
 104     args = parser.parse_args()
 105
 106     if args.dest == 'size':
 107         print get_verity_metadata_size(args.partition_size)
 108     else:
 109         build_verity_metadata(args.blocks / 4096, args.metadata_image,
 110                               args.root_hash, args.salt, args.block_device,
 111                               args.signer_path, args.signing_key,
 112                               args.signer_args)