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260 lines
7.4 KiB
260 lines
7.4 KiB
#!/usr/bin/env python3
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from __future__ import print_function
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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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SLOTS = 3
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pubkeys = {
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1: "04d571b7f148c5e4232c3814f777d8faeaf1a84216c78d569b71041ffc768a5b2d810fc3bb134dd026b57e65005275aedef43e155f48fc11a32ec790a93312bd58",
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2: "0463279c0c0866e50c05c799d32bd6bab0188b6de06536d1109d2ed9ce76cb335c490e55aee10cc901215132e853097d5432eda06b792073bd7740c94ce4516cb1",
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3: "0443aedbb6f7e71c563f8ed2ef64ec9981482519e7ef4f4aa98b27854e8c49126d4956d300ab45fdc34cd26bc8710de0a31dbdf6de7435fd0b492be70ac75fde58",
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4: "04877c39fd7c62237e038235e9c075dab261630f78eeb8edb92487159fffedfdf6046c6f8b881fa407c4a4ce6c28de0b19c1f4e29f1fcbc5a58ffd1432a3e0938a",
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5: "047384c51ae81add0a523adbb186c91b906ffb64c2c765802bf26dbd13bdf12c319e80c2213a136c8ee03d7874fd22b70d68e7dee469decfbbb510ee9a460cda45",
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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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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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parser.add_argument(
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"-s",
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"--sign",
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dest="sign",
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action="store_true",
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help="Add signature to firmware slot",
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)
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parser.add_argument(
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"-p", "--pem", dest="pem", action="store_true", help="Use PEM instead of SECEXP"
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)
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parser.add_argument(
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"-g",
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"--generate",
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dest="generate",
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action="store_true",
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help="Generate new ECDSA keypair",
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)
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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("Slot #%d" % (x + 1), "is empty")
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else:
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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 Exception:
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print("Slot #%d signature: INVALID" % (x + 1), 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, is_pem):
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# Ask for index and private key and signs the firmware
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slot = int(input("Enter signature slot (1-%d): " % SLOTS))
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if slot < 1 or slot > SLOTS:
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raise Exception("Invalid slot")
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if is_pem:
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print("Paste ECDSA private key in PEM format and press Enter:")
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print("(blank private key removes the signature on given index)")
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pem_key = ""
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while True:
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key = input()
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pem_key += key + "\n"
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if key == "":
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break
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if pem_key.strip() == "":
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# Blank key,let's remove existing signature from slot
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return modify(data, slot, 0, b"\x00" * 64)
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key = ecdsa.SigningKey.from_pem(pem_key)
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else:
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print("Paste SECEXP (in hex) and press Enter:")
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print("(blank private key removes the signature on given index)")
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secexp = input()
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if secexp.strip() == "":
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# Blank key,let's remove existing signature from slot
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return modify(data, slot, 0, b"\x00" * 64)
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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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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 main(args):
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if args.generate:
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key = ecdsa.SigningKey.generate(
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curve=ecdsa.curves.SECP256k1, hashfunc=hashlib.sha256
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)
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print("PRIVATE KEY (SECEXP):")
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print(key.to_string().hex())
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print()
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print("PRIVATE KEY (PEM):")
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print(key.to_pem())
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print("PUBLIC KEY:")
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print("04" + key.get_verifying_key().to_string().hex())
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return
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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("Firmware size %d bytes" % len(data))
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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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if args.sign:
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data = sign(data, args.pem)
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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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if __name__ == "__main__":
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args = parse_args()
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main(args)
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