/
backalyzer.py
executable file
·388 lines (350 loc) · 18.6 KB
/
backalyzer.py
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#! /usr/bin/env python3
import argparse
import logging
from Crypto.Cipher import AES
from rfc8452 import AES_GCM_SIV
from Crypto.Hash import SHA512
import binascii
from datetime import datetime
import bcrypt
from cryptography.hazmat.primitives.keywrap import aes_key_unwrap_with_padding
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.kdf.hkdf import HKDF
from pddbcommon import *
def bytes_to_semverstr(b):
maj = int.from_bytes(b[0:2], 'little')
min = int.from_bytes(b[2:4], 'little')
rev = int.from_bytes(b[4:6], 'little')
extra = int.from_bytes(b[6:8], 'little')
has_commit = int.from_bytes(b[12:16], 'little')
if has_commit != 0:
commit = int.from_bytes(b[8:12], 'little')
return "v{}.{}.{}-{}-g{:x}".format(maj, min, rev, extra, commit)
else:
return "v{}.{}.{}-{}".format(maj, min, rev, extra)
def main():
global MBBB_PAGES
FSCB_PAGES = 16
FSCB_LEN_PAGES = 2
KEY_PAGES = 1
global PAGE_SIZE
global VPAGE_SIZE
MAX_DICTS = 16383
# this is for an older set of CI tests from the pddbg.py script, that are not set up for this implementation
set_ci_tests_flag(False)
parser = argparse.ArgumentParser(description="Debug Backup Images")
parser.add_argument(
"-p", "--pin", help="Unlock PIN", type=str,
)
parser.add_argument(
"--backup-key", help="Backup key as BIP-39 words", type=str, default="abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon art"
)
parser.add_argument(
"--basis", type=str, help="Extra Bases to unlock, as `name:pass`. Each additional basis requires another --basis separator. Note that : is not legal to use in a Basis name.", action="append", nargs="+"
)
parser.add_argument(
"--loglevel", help="set logging level (INFO/DEBUG/WARNING/ERROR)", type=str, default="INFO",
)
parser.add_argument(
"-d", "--dump", help="Print data records in detail", action="store_true"
)
parser.add_argument(
"--hosted", help="Analyze a hosted mode PDDB image.", action="store_true"
)
parser.add_argument(
"-f", "--file", help="Input file (defaults to backup.pddb; note that hosted is in pddb-images/hosted.bin).", type=str, default="backup.pddb"
)
parser.add_argument(
"-c", "--checksum-only", help="Only perform checks for media errors. Does not authenticate the backup; does not require passwords.", action="store_true"
)
args = parser.parse_args()
if args.hosted == False and args.pin == None and args.checksum_only == False:
print("Unlock PIN argument is required, please specified with `-p [pin]`")
exit(0)
numeric_level = getattr(logging, args.loglevel.upper(), None)
if not isinstance(numeric_level, int):
raise ValueError('Invalid log level: %s' % args.loglevel)
logging.basicConfig(level=numeric_level)
basis_credentials = []
if args.basis:
for pair in args.basis:
credpair = pair[0].split(':', 1)
if len(credpair) != 2:
logging.error("Basis credential pair with name {} has a formatting problem, aborting!".format(credpair[0]))
exit(1)
basis_credentials += [credpair]
# insert your mnemonic here. This is the "zero-key" mnemonic.
mnemonic = args.backup_key
# Like before with automatic language detection
key = bip39_to_bits(mnemonic)
logging.debug("Using backup key: 0x{}".format(key.hex()))
with open(args.file, "rb") as backup_file:
global VERSION
SYSTEM_BASIS = ".System"
VERSION = 0x201.to_bytes(4, 'little') # update this manually here if the PDDB version gets bumped :P
AAD = b"PDDB backup v0.1.0"
backup = backup_file.read()
if args.hosted == False:
PT_HEADER_LEN = 4 + 16 * 4 + 4 + 8 + 64 + 4 + 4 # ignore the pt header
NONCE_LEN = 12
CT_LEN = PT_HEADER_LEN + 1024 + 64
TAG_LEN = 16
COMMIT_NONCE_LEN = 32
COMMIT_LEN = 32
CHECKSUM_LEN = 32
PADDING = 4 # structure is padded to 8-byte boundary
offset = PT_HEADER_LEN
nonce = backup[offset:offset+NONCE_LEN]
offset += NONCE_LEN
ct = backup[offset:offset+CT_LEN]
offset += CT_LEN
mac = backup[offset:offset+TAG_LEN]
offset += TAG_LEN
commit_nonce = backup[offset:offset+COMMIT_NONCE_LEN]
offset += COMMIT_NONCE_LEN
commit = backup[offset:offset+COMMIT_LEN]
offset += COMMIT_LEN
offset += PADDING
check_region = backup[:offset]
checksum = backup[offset:offset+CHECKSUM_LEN]
# Implement backup integrity checking without passwords. The metadata about the
# backup is "unchecked" because it's not coming from an encrypted region. Full restore
# routines use the checked version, but the purpose of this flow is to provide
# users with a way to confirm the integrity of backup files without having to
# disclose sensitive information.
i = 0
unchecked_backup_version = int.from_bytes(backup[i:i+4], 'little')
i += 96
unchecked_checksum_region_len = int.from_bytes(backup[i:i+4], 'little') * 4096
i += 4
unchecked_total_checksums = int.from_bytes(backup[i:i+4], 'little')
i += 4
unchecked_header_total_size = int.from_bytes(backup[i:i+4], 'little')
if args.checksum_only and (unchecked_backup_version == 0x10001):
checksum_errors = False
logging.info("Doing hash verification of pt+ct metadata based on unchecked plaintext parameters")
hasher = SHA512.new(truncate="256")
# this is where the backup upcode is located. It should be 1
# check_region = bytearray(check_region)
# check_region[144:148] = [1, 0, 0, 0] # should be at 0x90 offset
hasher.update(check_region)
computed_checksum = hasher.digest()
if computed_checksum != checksum:
logging.error("Header failed hash integrity check!")
logging.error("Calculated: {}".format(computed_checksum.hex()))
logging.error("Expected: {}".format(checksum.hex()))
exit(1)
else:
logging.info("Header passed integrity check.")
if unchecked_total_checksums != 0:
raw_checksums = backup[unchecked_header_total_size-(unchecked_total_checksums * 16):unchecked_header_total_size]
checksums = [raw_checksums[i:i+16] for i in range(0, len(raw_checksums), 16)]
check_block_num = 0
while check_block_num < unchecked_total_checksums:
hasher = SHA512.new(truncate="256")
hasher.update(
backup[
unchecked_header_total_size + check_block_num * unchecked_checksum_region_len:
unchecked_header_total_size + (check_block_num + 1) * unchecked_checksum_region_len
])
sum = hasher.digest()
if sum[:16] != checksums[check_block_num]:
logging.error("Bad checksum on block {} at offset 0x{:x}".format(check_block_num, check_block_num * checksum_region_len))
logging.error(" Calculated: {}".format(sum[:16].hex()))
logging.error(" Expected: {}".format(checksums[check_block_num].hex()))
checksum_errors = True
check_block_num += 1
if checksum_errors:
logging.error("Media errors were detected! Backup may be unusable.")
exit(1)
else:
logging.info("No media errors detected, {} blocks passed checksum tests".format(unchecked_total_checksums))
if args.checksum_only:
exit(0)
else:
if args.checksum_only:
logging.error("Can't perform checksum verification on backups that do not include checksums")
exit(1)
else:
logging.info("Backup has no checksum block, skipping media integrity checks")
elif args.checksum_only:
logging.error("Can't perform checksum verification on backups with a version older than 1.1")
exit(1)
h_enc = SHA512.new(truncate="256")
h_enc.update(key)
h_enc.update(bytes([0x43, 0x6f, 0x6, 0xd6, 0xd, 0x69, 0x74, 0x01, 0x01]))
h_enc.update(commit_nonce)
k_enc = h_enc.digest()
h_com = SHA512.new(truncate="256")
h_com.update(key)
h_com.update(bytes([0x43, 0x6f, 0x6, 0xd6, 0xd, 0x69, 0x74, 0x01, 0x02]))
h_com.update(commit_nonce)
k_com_derived = h_com.digest()
logging.debug('kcom_stored: ' + binascii.hexlify(commit).decode('utf-8'))
logging.debug('kcom_derived: ' + binascii.hexlify(k_com_derived).decode('utf-8'))
if k_com_derived != commit:
logging.error("Key commitment is incorrect")
exit(1)
cipher = AES_GCM_SIV(k_enc, nonce)
try:
pt_data = cipher.decrypt(ct + mac, AAD)
except:
logging.error("Ciphertext did not pass AES-GCM-SIV validation")
exit(1)
i = 0
backup_version = int.from_bytes(pt_data[i:i+4], 'little')
logging.info("Backup version: 0x{:08x}".format(backup_version))
i += 4
logging.info("Xous version: {}".format(bytes_to_semverstr(pt_data[i:i+16])))
i += 16
logging.info("SOC version: {}".format(bytes_to_semverstr(pt_data[i:i+16])))
i += 16
logging.info("EC version: {}".format(bytes_to_semverstr(pt_data[i:i+16])))
i += 16
logging.info("WF200 version: {}".format(bytes_to_semverstr(pt_data[i:i+16])))
i += 16
i += 4 # padding because align=8
ts = int.from_bytes(pt_data[i:i+8], 'little') / 1000
logging.info("Timestamp: {} / {}".format(ts, datetime.utcfromtimestamp(ts).strftime('%Y-%m-%d %H:%M:%S')))
i += 8
logging.info("Language code: {}".format(int.from_bytes(pt_data[i:i+4], 'little')))
i += 4
logging.info("Keyboard layout code: {}".format(int.from_bytes(pt_data[i:i+4], 'little')))
i += 4
logging.info("DNA: 0x{:x}".format(int.from_bytes(pt_data[i:i+8], 'little')))
dna = pt_data[i:i+8]
dna_int = int.from_bytes(dna, 'little')
i += 8
checksum_region_len = int.from_bytes(pt_data[i:i+4], 'little') * 4096
logging.info("Checksum region length: 0x{:x}".format(checksum_region_len))
i += 4
total_checksums = int.from_bytes(pt_data[i:i+4], 'little')
logging.info("Number of checksums, including the header checksum itself: {}".format(total_checksums))
i += 4
header_total_size = int.from_bytes(pt_data[i:i+4], 'little')
logging.info("Header total length in bytes: {}".format(header_total_size))
i += 4
i += 36 # reserved
op = int.from_bytes(pt_data[i:i+4], 'little')
logging.info("Stored Backup Opcode: {}".format(op))
i += 8 # padding because align=8
if backup_version == 0x10001:
checksum_errors = False
logging.info("Doing hash verification of pt+ct metadata")
hasher = SHA512.new(truncate="256")
# this is where the backup upcode is located. It should be 1
# check_region = bytearray(check_region)
# check_region[144:148] = [1, 0, 0, 0] # should be at 0x90 offset
hasher.update(check_region)
computed_checksum = hasher.digest()
if computed_checksum != checksum:
logging.error("Header failed hash integrity check!")
logging.error("Calculated: {}".format(computed_checksum.hex()))
logging.error("Expected: {}".format(checksum.hex()))
exit(1)
else:
logging.info("Header passed integrity check.")
if total_checksums != 0:
raw_checksums = backup[header_total_size-(total_checksums * 16):header_total_size]
checksums = [raw_checksums[i:i+16] for i in range(0, len(raw_checksums), 16)]
check_block_num = 0
while check_block_num < total_checksums:
hasher = SHA512.new(truncate="256")
hasher.update(
backup[
header_total_size + check_block_num * checksum_region_len:
header_total_size + (check_block_num + 1) * checksum_region_len
])
sum = hasher.digest()
if sum[:16] != checksums[check_block_num]:
logging.error("Bad checksum on block {} at offset 0x{:x}".format(check_block_num, check_block_num * checksum_region_len))
logging.error(" Calculated: {}".format(sum[:16].hex()))
logging.error(" Expected: {}".format(checksums[check_block_num].hex()))
checksum_errors = True
check_block_num += 1
if checksum_errors:
logging.error("Media errors were detected! Backup may be unusable.")
exit(1)
else:
logging.info("No media errors detected, {} blocks passed checksum tests".format(total_checksums))
if args.checksum_only:
exit(0)
else:
if args.checksum_only:
logging.error("Can't perform checksum verification on backups that do not include checksums")
exit(1)
else:
logging.info("Backup has no checksum block, skipping media integrity checks")
elif args.checksum_only:
logging.error("Can't perform checksum verification on backups with a version older than 1.1")
exit(1)
keyrom = pt_data[i:i+1024]
keys = extract_keys(keyrom, backup[4096:], args.pin, basis_credentials=basis_credentials)
pddb = backup[4096:]
else:
dna_int = 0
keyrom = [0] * 1024
keys = extract_keys(keyrom, backup, args.pin, basis_credentials=basis_credentials)
pddb = backup
pddb_len = len(pddb)
pddb_size_pages = pddb_len // PAGE_SIZE
# data_aad = SYSTEM_BASIS + PDDB_VERSION + dna
# now that we have the credentials, extract the baseline image
mbbb_offset = pddb_size_pages * Pte.PTE_LEN + PAGE_SIZE * KEY_PAGES
if mbbb_offset & (PAGE_SIZE - 1) != 0:
mbbb_offset = (mbbb_offset + PAGE_SIZE) & 0xFFFF_F000 # round up to nearest page
logging.info("MBBB: 0x{:x}".format(mbbb_offset))
img_index = 0
img_index += pddb_size_pages * Pte.PTE_LEN
if img_index & (PAGE_SIZE - 1) != 0:
img_index = (img_index + PAGE_SIZE) & 0xFFFF_F000
rawkeys = pddb[img_index : img_index + PAGE_SIZE * KEY_PAGES]
logging.debug("Keys: 0x{:x}".format(img_index))
img_index += PAGE_SIZE * KEY_PAGES
mbbb = pddb[img_index : img_index + PAGE_SIZE * MBBB_PAGES]
logging.debug("MBBB check: 0x{:x}".format(img_index))
img_index += PAGE_SIZE * MBBB_PAGES
fscb = decode_fscb(pddb[img_index: img_index + PAGE_SIZE * FSCB_PAGES], keys, FSCB_LEN_PAGES=FSCB_LEN_PAGES, dna=dna_int)
logging.debug("FSCB: 0x{:x}".format(img_index))
img_index += PAGE_SIZE * FSCB_PAGES
logging.debug("Data: 0x{:x}".format(img_index))
data = pddb[img_index:]
tables = decode_pagetable(pddb, pddb_size_pages, keys, pddb[mbbb_offset:mbbb_offset + MBBB_PAGES * PAGE_SIZE], dna=dna_int, data=data)
# iterate through found Bases and print their contents
for name, key in keys.items():
if name in tables:
logging.info("Basis '{}', key_pt: {}, key_data: {}".format(name, key[0].hex(), key[1].hex()))
v2p_table = tables[name][0]
p2v_table = tables[name][1]
basis_data = bytearray()
pp_start = v2p_table[VPAGE_SIZE]
pp_data = data[pp_start:pp_start + PAGE_SIZE]
try:
if ':' in name:
basis_name = name.split(':')[0]
else:
basis_name = name
pt_data = keycommit_decrypt(key[1], basis_aad(basis_name, dna=dna_int), pp_data)
basis_data.extend(bytearray(pt_data))
logging.debug("decrypted vpage @ {:x} ppage @ {:x}".format(VPAGE_SIZE, v2p_table[VPAGE_SIZE]))
basis = Basis(basis_data)
logging.info(basis.as_str())
basis_dicts = {}
dicts_found = 0
dict_index = 0
while dict_index < MAX_DICTS and dicts_found < basis.num_dicts:
bdict = BasisDicts(dict_index, v2p_table, data, key[1], basis_name, dna=dna_int)
if bdict.valid:
basis_dicts[bdict.name] = bdict
dicts_found += 1
dict_index += 1
if dicts_found != basis.num_dicts:
logging.error("Expected {} dictionaries, only found {}; searched {}".format(basis.num_dicts, dicts_found, dict_index))
if args.dump:
for bdict in basis_dicts.values():
logging.info(bdict.as_str())
except ValueError:
logging.error("couldn't decrypt basis root vpage @ {:x} ppage @ {:x}".format(VPAGE_SIZE, v2p_table[VPAGE_SIZE]))
if __name__ == "__main__":
main()
exit(0)