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334 lines
9.2 KiB
334 lines
9.2 KiB
#!/usr/bin/env python3
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import argparse
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import hashlib
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import struct
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import ecdsa
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from ecdsa import BadSignatureError
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SLOTS = 3
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pubkeys_dev = {
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1: "042c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991ae31a9c671a36543f46cea8fce6984608aa316aa0472a7eed08847440218cb2f",
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2: "04edabbd16b41c8371b92ef2f04c1185b4f03b6dcd52ba9b78d9d7c89c8f2211452c88a66eb8ac3c19a1cc3a3fc6d72506f6fce2025f738d8b55f29f22125eb0a4",
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3: "04665f660a5052be7a95546a02179058d93d3e08a779734914594346075bb0afd45113948d72cf3dc8f2b70ee02dc1695d051bb0c6da2a914a69045e3277682d3b",
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}
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privkeys_dev = {
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1: "0x4444444444444444444444444444444444444444444444444444444444444444",
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2: "0x4545454545454545454545454545454545454545454545454545454545454545",
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3: "0xbfc4bca9c9c228a16639d3503d999a733a439210b64cebe757a4fd03ca46a5c8",
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}
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FWHEADER_SIZE = 1024
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SIGNATURES_START = 6 * 4 + 8 + 512
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INDEXES_START = SIGNATURES_START + 3 * 64
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INDEXES_START_OLD = len("TRZR") + struct.calcsize("<I")
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SIG_START = INDEXES_START_OLD + SLOTS + 1 + 52
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def parse_args():
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parser = argparse.ArgumentParser(
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description="Commandline tool for signing Trezor firmware."
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)
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parser.add_argument("-f", "--file", dest="path", help="Firmware file to modify")
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return parser.parse_args()
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def pad_to_size(data, size):
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if len(data) > size:
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raise ValueError("Chunk too big already")
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if len(data) == size:
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return data
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return data + b"\xFF" * (size - len(data))
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# see memory.h for details
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def prepare_hashes(data):
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# process chunks
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start = 0
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end = (64 - 1) * 1024
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hashes = []
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for i in range(16):
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sector = data[start:end]
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if len(sector) > 0:
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chunk = pad_to_size(sector, end - start)
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hashes.append(hashlib.sha256(chunk).digest())
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else:
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hashes.append(b"\x00" * 32)
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start = end
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end += 64 * 1024
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return hashes
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def check_hashes(data):
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expected_hashes = data[0x20 : 0x20 + 16 * 32]
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hashes = b""
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for h in prepare_hashes(data[FWHEADER_SIZE:]):
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hashes += h
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if expected_hashes == hashes:
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print("HASHES OK")
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else:
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print("HASHES NOT OK")
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def update_hashes_in_header(data):
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# Store hashes in the firmware header
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data = bytearray(data)
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o = 0
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for h in prepare_hashes(data[FWHEADER_SIZE:]):
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data[0x20 + o : 0x20 + o + 32] = h
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o += 32
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return bytes(data)
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def get_header(data, zero_signatures=False):
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if not zero_signatures:
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return data[:FWHEADER_SIZE]
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else:
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data = bytearray(data[:FWHEADER_SIZE])
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data[SIGNATURES_START : SIGNATURES_START + 3 * 64 + 3] = b"\x00" * (3 * 64 + 3)
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return bytes(data)
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def check_size(data):
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size = struct.unpack("<L", data[12:16])[0]
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assert size == len(data) - 1024
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def check_signatures(data):
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# Analyses given firmware and prints out
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# status of included signatures
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indexes = [x for x in data[INDEXES_START : INDEXES_START + SLOTS]]
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to_sign = get_header(data, zero_signatures=True)
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fingerprint = hashlib.sha256(to_sign).hexdigest()
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print("Firmware fingerprint:", fingerprint)
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used = []
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for x in range(SLOTS):
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signature = data[SIGNATURES_START + 64 * x : SIGNATURES_START + 64 * x + 64]
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if indexes[x] == 0:
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print(f"Slot #{x + 1}", "is empty")
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else:
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pubkeys = pubkeys_dev
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pk = pubkeys[indexes[x]]
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verify = ecdsa.VerifyingKey.from_string(
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bytes.fromhex(pk)[1:],
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curve=ecdsa.curves.SECP256k1,
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hashfunc=hashlib.sha256,
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)
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try:
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verify.verify(signature, to_sign, hashfunc=hashlib.sha256)
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if indexes[x] in used:
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print(f"Slot #{x + 1} signature: DUPLICATE", signature.hex())
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else:
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used.append(indexes[x])
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print(f"Slot #{x + 1} signature: VALID", signature.hex())
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except Exception:
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print(f"Slot #{x + 1} signature: INVALID", signature.hex())
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def modify(data, slot, index, signature):
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data = bytearray(data)
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# put index to data
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data[INDEXES_START + slot - 1] = index
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# put signature to data
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data[SIGNATURES_START + 64 * (slot - 1) : SIGNATURES_START + 64 * slot] = signature
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return bytes(data)
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def sign(data, slot, secexp):
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key = ecdsa.SigningKey.from_secret_exponent(
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secexp=int(secexp, 16),
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curve=ecdsa.curves.SECP256k1,
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hashfunc=hashlib.sha256,
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)
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to_sign = get_header(data, zero_signatures=True)
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# Locate proper index of current signing key
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pubkey = "04" + key.get_verifying_key().to_string().hex()
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index = None
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pubkeys = pubkeys_dev
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for i, pk in pubkeys.items():
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if pk == pubkey:
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index = i
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break
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if index is None:
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raise Exception("Unable to find private key index. Unknown private key?")
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signature = key.sign_deterministic(to_sign, hashfunc=hashlib.sha256)
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return modify(data, slot, index, signature)
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def prepare_old(data):
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# Takes raw OR signed firmware and clean out metadata structure
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# This produces 'clean' data for signing
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meta = b"TRZR" # magic
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if data[:4] == b"TRZR":
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meta += data[4 : 4 + struct.calcsize("<I")]
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else:
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meta += struct.pack("<I", len(data)) # length of the code
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meta += b"\x00" * SLOTS # signature index #1-#3
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meta += b"\x01" # flags
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meta += b"\x00" * 52 # reserved
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meta += b"\x00" * 64 * SLOTS # signature #1-#3
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if data[:4] == b"TRZR":
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# Replace existing header
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out = meta + data[len(meta) :]
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else:
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# create data from meta + code
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out = meta + data
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return out
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def check_signatures_old(data):
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# Analyses given firmware and prints out
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# status of included signatures
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try:
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indexes = [ord(x) for x in data[INDEXES_START_OLD : INDEXES_START_OLD + SLOTS]]
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except TypeError:
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indexes = [x for x in data[INDEXES_START_OLD : INDEXES_START_OLD + SLOTS]]
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to_sign = prepare_old(data)[256:] # without meta
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fingerprint = hashlib.sha256(to_sign).hexdigest()
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print("Firmware fingerprint:", fingerprint)
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used = []
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for x in range(SLOTS):
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signature = data[SIG_START + 64 * x : SIG_START + 64 * x + 64]
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if indexes[x] == 0:
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print("Slot #%d" % (x + 1), "is empty")
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else:
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pubkeys = pubkeys_dev
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pk = pubkeys[indexes[x]]
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verify = ecdsa.VerifyingKey.from_string(
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bytes.fromhex(pk)[1:],
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curve=ecdsa.curves.SECP256k1,
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hashfunc=hashlib.sha256,
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)
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try:
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verify.verify(signature, to_sign, hashfunc=hashlib.sha256)
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if indexes[x] in used:
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print("Slot #%d signature: DUPLICATE" % (x + 1), signature.hex())
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else:
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used.append(indexes[x])
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print("Slot #%d signature: VALID" % (x + 1), signature.hex())
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except BadSignatureError:
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print("Slot #%d signature: INVALID" % (x + 1), signature.hex())
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def modify_old(data, slot, index, signature):
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# Replace signature in data
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# Put index to data
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data = (
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data[: INDEXES_START_OLD + slot - 1]
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+ bytes([index])
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+ data[INDEXES_START_OLD + slot :]
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)
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# Put signature to data
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data = (
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data[: SIG_START + 64 * (slot - 1)] + signature + data[SIG_START + 64 * slot :]
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)
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return data
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def sign_old(data, slot, secexp):
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key = ecdsa.SigningKey.from_secret_exponent(
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secexp=int(secexp, 16),
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curve=ecdsa.curves.SECP256k1,
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hashfunc=hashlib.sha256,
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)
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to_sign = prepare_old(data)[256:] # without meta
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# Locate proper index of current signing key
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pubkey = "04" + key.get_verifying_key().to_string().hex()
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index = None
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pubkeys = pubkeys_dev
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for i, pk in pubkeys.items():
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if pk == pubkey:
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index = i
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break
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if index is None:
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raise Exception("Unable to find private key index. Unknown private key?")
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signature = key.sign_deterministic(to_sign, hashfunc=hashlib.sha256)
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return modify_old(data, slot, index, signature)
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def main(args):
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if not args.path:
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raise Exception("-f/--file is required")
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data = open(args.path, "rb").read()
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assert len(data) % 4 == 0
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if data[:4] != b"TRZF":
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raise Exception("Firmware header expected")
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data = update_hashes_in_header(data)
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print(f"Firmware size {len(data)} bytes")
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check_size(data)
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check_signatures(data)
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check_hashes(data)
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data = sign(data, 1, privkeys_dev[1])
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data = sign(data, 2, privkeys_dev[2])
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data = sign(data, 3, privkeys_dev[3])
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check_signatures(data)
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check_hashes(data)
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fp = open(args.path, "wb")
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fp.write(data)
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fp.close()
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data = prepare_old(data)
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check_signatures_old(data)
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data = sign_old(data, 1, privkeys_dev[1])
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data = sign_old(data, 2, privkeys_dev[2])
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data = sign_old(data, 3, privkeys_dev[3])
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check_signatures_old(data)
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fp = open(args.path, "wb")
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fp.write(data)
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fp.close()
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if __name__ == "__main__":
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args = parse_args()
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main(args)
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