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      1 #! /usr/bin/env python
      2 
      3 import os
      4 import sys
      5 import struct
      6 import tempfile
      7 import commands
      8 
      9 VERSION = 0
     10 MAGIC_NUMBER = 0xb001b001
     11 BLOCK_SIZE = 4096
     12 METADATA_SIZE = BLOCK_SIZE * 8
     13 
     14 def run(cmd):
     15     status, output = commands.getstatusoutput(cmd)
     16     print output
     17     if status:
     18         exit(-1)
     19 
     20 def get_verity_metadata_size(data_size):
     21     return METADATA_SIZE
     22 
     23 def build_metadata_block(verity_table, signature):
     24     table_len = len(verity_table)
     25     block = struct.pack("II256sI", MAGIC_NUMBER, VERSION, signature, table_len)
     26     block += verity_table
     27     block = block.ljust(METADATA_SIZE, '\x00')
     28     return block
     29 
     30 def sign_verity_table(table, signer_path, key_path):
     31     with tempfile.NamedTemporaryFile(suffix='.table') as table_file:
     32         with tempfile.NamedTemporaryFile(suffix='.sig') as signature_file:
     33             table_file.write(table)
     34             table_file.flush()
     35             cmd = " ".join((signer_path, table_file.name, key_path, signature_file.name))
     36             print cmd
     37             run(cmd)
     38             return signature_file.read()
     39 
     40 def build_verity_table(block_device, data_blocks, root_hash, salt):
     41     table = "1 %s %s %s %s %s %s sha256 %s %s"
     42     table %= (  block_device,
     43                 block_device,
     44                 BLOCK_SIZE,
     45                 BLOCK_SIZE,
     46                 data_blocks,
     47                 data_blocks,
     48                 root_hash,
     49                 salt)
     50     return table
     51 
     52 def build_verity_metadata(data_blocks, metadata_image, root_hash,
     53                             salt, block_device, signer_path, signing_key):
     54     # build the verity table
     55     verity_table = build_verity_table(block_device, data_blocks, root_hash, salt)
     56     # build the verity table signature
     57     signature = sign_verity_table(verity_table, signer_path, signing_key)
     58     # build the metadata block
     59     metadata_block = build_metadata_block(verity_table, signature)
     60     # write it to the outfile
     61     with open(metadata_image, "wb") as f:
     62         f.write(metadata_block)
     63 
     64 if __name__ == "__main__":
     65     if len(sys.argv) == 3 and sys.argv[1] == "-s":
     66         print get_verity_metadata_size(int(sys.argv[2]))
     67     elif len(sys.argv) == 8:
     68         data_image_blocks = int(sys.argv[1]) / 4096
     69         metadata_image = sys.argv[2]
     70         root_hash = sys.argv[3]
     71         salt = sys.argv[4]
     72         block_device = sys.argv[5]
     73         signer_path = sys.argv[6]
     74         signing_key = sys.argv[7]
     75         build_verity_metadata(data_image_blocks, metadata_image, root_hash,
     76                                 salt, block_device, signer_path, signing_key)
     77     else:
     78         exit(-1)
     79