Add utility to build a delta file with a single insert

For hijacking build a complete delta for a single insert. Need to
externalize the parameters. It could work for multiple files too.
master
Holger Hans Peter Freyther 6 years ago
parent 111d55b2c4
commit bd82bb4fef
  1. 124
      update-ec20/build_diff.py

@ -0,0 +1,124 @@
#!/usr/bin/python3
"""
Build a single insert for RedBend OTA filesystem updates
All rights reversed
"""
from PyCRC import CRC32
import subprocess
import os
import io
import struct
permission_bytes = bytes.fromhex('1A 5F 72 65 64 62 65 6E 64 5F 30 34 30 37 35 35 3A 30 30 30 30 3A 30 30 30 30 00 1A 5F 72 65 64 62 65 6E 64 5F 30 34 31 37 37 37 3A 30 30 30 30 3A 30 30 30 30 00 1A 5F 72 65 64 62 65 6E 64 5F 30 34 32 37 35 35 3A 30 30 30 30 3A 30 30 30 30 00 1A 5F 72 65 64 62 65 6E 64 5F 31 30 30 36 34 34 3A 30 30 30 30 3A 30 30 30 30 00 1A 5F 72 65 64 62 65 6E 64 5F 31 30 30 37 35 35 3A 30 30 30 30 3A 30 30 30 30 00 1A 5F 72 65 64 62 65 6E 64 5F 31 30 30 37 37 37 3A 30 30 30 30 3A 30 30 30 30 00 1A 5F 72 65 64 62 65 6E 64 5F 31 30 34 37 35 35 3A 30 30 30 30 3A 30 30 30 30 00 1A 5F 72 65 64 62 65 6E 64 5F 31 32 30 37 37 37 3A 30 30 30 30 3A 30 30 30 30 00')
general_bytes = bytes.fromhex('50 40 01 00 80 38 01 00 00 00 00')
fs_bytes = bytes.fromhex('80 80 02 00 00 ')
# initialize tables only once
crc32 = CRC32.CRC32()
def compress(fname):
"""I compress a file with LZMA and return the byte array"""
lzma_fname = fname + ".lzma"
print(lzma_fname)
ret = subprocess.call(["lzma", "e", fname, lzma_fname])
assert ret == 0
with open(lzma_fname, "rb") as f:
return f.read()
def build_toc(fname, size, compr_size):
"""I build the table of content for a single file and insert"""
wr = io.BytesIO()
# name + NUL
wr.write(fname.encode('utf8'))
wr.write(b'\0')
# permissions
wr.write(permission_bytes)
# FILE_SIZE + D100 0000 (offset to permission) + COMPR_SIZE
off = len(wr.getvalue())
wr.write(struct.pack('<I', size))
wr.write(b'\xD1\x00\x00\x00')
wr.write(struct.pack('<I', compr_size))
return off, wr.getvalue()
def build_delta(num_insert, toc, offset, data):
"""I build the delta with the header, checksum, length, toc,
offsets and the data"""
hdr = io.BytesIO()
hdr.write(general_bytes)
hdr.write(fs_bytes)
hdr.write(b'\xc8\x00\x02\x00') # ram size
hdr.write(b'\x00\x00\x04\x00') # sector size
hdr.write(struct.pack('<I', offset))
hdr.write(struct.pack('<I', len(toc)))
hdr.write(b'\x22\x00\x02\x00') # min_alloc_ram_use | ext_info_sz
hdr.write(struct.pack('<H', 0)) # num_copy
hdr.write(struct.pack('<H', 0)) # num_diff
hdr.write(struct.pack('<H', num_insert)) # num_inser
hdr.write(struct.pack('<H', 0)) # num_delete
hdr.write(struct.pack('<H', 0)) # num_delete_dirs
hdr.write(struct.pack('<H', 0)) # num_dirs
hdr.write(struct.pack('<H', 0)) # num_del_link
hdr.write(struct.pack('<H', 0)) # num_link
hdr.write(struct.pack('<H', 0)) # num_cri_update
hdr.write(struct.pack('<H', num_insert)) # num_crit_insert
for i in range(0, num_insert):
hdr.write(b'\x33\xC3\xC3\x33') # crc of the target file?
combined = hdr.getvalue() + toc + data
wr = io.BytesIO()
wr.write(struct.pack("<I", len(combined) + 8))
wr.write(combined)
with_csum = io.BytesIO()
with_csum.write(struct.pack("<I", crc32.calculate(wr.getvalue())))
with_csum.write(wr.getvalue())
return with_csum.getvalue()
def build_filenames(name):
"""I build a filenames table including the name"""
wr = io.BytesIO()
wr.write(general_bytes)
wr.write(bytes.fromhex('00 00 03 00 00 01 00 00 00')) # never different
wr.write(struct.pack('<I', len(name) + 1))
wr.write(name.encode('utf8'))
wr.write(b'\x00')
wr.write(struct.pack('<I', 0))
hdr = io.BytesIO()
hdr.write(struct.pack("<I", len(wr.getvalue()) + 8))
hdr.write(wr.getvalue())
with_csum = io.BytesIO()
with_csum.write(struct.pack("<I", crc32.calculate(hdr.getvalue())))
with_csum.write(hdr.getvalue())
return with_csum.getvalue()
def assemble(delta, filenames):
"""I put delta and filenamestable together.. I might add padding
if the rule is understood correctly"""
return delta + filenames
name = "system"
fname = "/bin/hello_world.sh"
fpath = "hello_world.sh"
flen = os.stat(fpath).st_size
fdata = compress(fpath)
(offset,toc) = build_toc(fname, flen, len(fdata))
with open("build_toc.bin", "wb") as f:
f.write(toc)
toc_compr = compress("build_toc.bin")
delta = build_delta(1, toc_compr, offset, fdata)
namet = build_filenames(name)
update = assemble(delta, namet)
print(namet.hex())
with open(name + ".diff", "wb") as f:
f.write(update)
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