import struct, hashlib, binascii, sys
img = open('files/backup-srv-03.img','rb').read()
state = open('files/rec/var/lib/collector/.state/last.chk','rb').read()
mid = open('files/rec/etc/machine-id','rb').read().rstrip(b'\r\n')
fs_uuid = 'e45cf08f-1459-4019-800f-45846f787d90'
H = lambda b: hashlib.sha256(b).digest()
magic, mloc, nonce, ino, tag = struct.unpack('<4s4s8sI4s', state)
print(len(state), magic, ino, tag == H(state[:20])[:4])
mask = H(mid + b':resume-v2')[:4]
lba_t = struct.unpack('<I', bytes(a^b for a,b in zip(mloc,mask)))[0]
t = img[lba_t*512:]
assert t[:4]==b'RSV2', t[:8]
cnt, es = t[4], t[5]
out = {}
for i in range(cnt):
    e = t[6+i*es:6+(i+1)*es]
    pos, lba, crc = struct.unpack('<BIH', e)
    assert binascii.crc_hqx(e[:5],0xffff)==crc, i
    ctx = f'{fs_uuid}:{ino}:{lba_t}:{nonce.hex()}:cache-sync/3.4:{pos}'.encode()
    out[pos] = img[lba*512] ^ H(ctx)[0]
print(bytes(out[i] for i in range(cnt)))