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feat(core, python): implement new code entry pairing

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This commit is contained in:
M1nd3r 2025-01-30 18:52:25 +01:00
parent 1d1f670a18
commit 9b16b9b7a7
3 changed files with 66 additions and 19 deletions
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5
core/src/apps/thp/pairing.py
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@ -198,10 +198,10 @@ async def _handle_code_entry_is_selected_first_time(ctx: PairingContext) -> None
if challenge_message.challenge is None:
raise Exception("Invalid message")
sha_ctx = sha256(ctx.channel_ctx.get_handshake_hash())
sha_ctx = sha256(ThpPairingMethod.CodeEntry.to_bytes(1, "big"))
sha_ctx.update(ctx.channel_ctx.get_handshake_hash())
sha_ctx.update(ctx.code_entry_secret)
sha_ctx.update(challenge_message.challenge)
sha_ctx.update(bytes("PairingMethod_CodeEntry", "utf-8"))
code_code_entry_hash = sha_ctx.digest()
ctx.display_data.code_code_entry = (
int.from_bytes(code_code_entry_hash, "big") % 1000000
@ -327,6 +327,7 @@ async def _handle_nfc_tag(
assert ctx.nfc_secret is not None
assert ctx.handshake_hash_host is not None
assert ctx.nfc_secret_host is not None
assert len(ctx.nfc_secret_host) == 16
sha_ctx = sha256(ThpPairingMethod.NFC.to_bytes(1, "big"))
sha_ctx.update(ctx.channel_ctx.get_handshake_hash())

40
python/src/trezorlib/transport/thp/cpace.py Normal file
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@ -0,0 +1,40 @@
import typing as t
from hashlib import sha512
from . import curve25519
_PREFIX = b"\x08\x43\x50\x61\x63\x65\x32\x35\x35\x06"
_PADDING = b"\x6f\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x20"
class Cpace:
"""
CPace, a balanced composable PAKE: https://datatracker.ietf.org/doc/draft-irtf-cfrg-cpace/
"""
random_bytes: t.Callable[[int], bytes]
def __init__(self, handshake_hash: bytes) -> None:
self.handshake_hash: bytes = handshake_hash
self.shared_secret: bytes
self.host_private_key: bytes
self.host_public_key: bytes
def generate_keys_and_secret(
self, code_code_entry: bytes, trezor_public_key: bytes
) -> None:
"""
Generate ephemeral key pair and a shared secret using Elligator2 with X25519.
"""
sha_ctx = sha512(_PREFIX)
sha_ctx.update(code_code_entry)
sha_ctx.update(_PADDING)
sha_ctx.update(self.handshake_hash)
sha_ctx.update(b"\x00")
pregenerator = sha_ctx.digest()[:32]
generator = curve25519.elligator2(pregenerator)
self.host_private_key = self.random_bytes(32)
self.host_public_key = curve25519.multiply(self.host_private_key, generator)
self.shared_secret = curve25519.multiply(
self.host_private_key, trezor_public_key
)

40
tests/device_tests/thp/test_thp.py
View File

@ -1,6 +1,7 @@
import hashlib
import os
import random
import typing as t
from hashlib import sha256
import pytest
import typing_extensions as tx
@ -29,6 +30,7 @@ from trezorlib.messages import (
ThpSelectMethod,
)
from trezorlib.transport.thp import curve25519
from trezorlib.transport.thp.cpace import Cpace
from trezorlib.transport.thp.protocol_v2 import MANAGEMENT_SESSION_ID, _hkdf
if t.TYPE_CHECKING:
@ -164,7 +166,7 @@ def test_pairing_qr_code(client: Client) -> None:
code = pairing_info.code_qr_code
# Compute tag for response
sha_ctx = hashlib.sha256(protocol.handshake_hash)
sha_ctx = sha256(protocol.handshake_hash)
sha_ctx.update(code)
tag = sha_ctx.digest()
@ -173,7 +175,7 @@ def test_pairing_qr_code(client: Client) -> None:
secret_msg = _read_message(ThpQrCodeSecret)
# Check that the `code` was derived from the revealed secret
sha_ctx = hashlib.sha256(ThpPairingMethod.QrCode.to_bytes(1, "big"))
sha_ctx = sha256(ThpPairingMethod.QrCode.to_bytes(1, "big"))
sha_ctx.update(protocol.handshake_hash)
sha_ctx.update(secret_msg.secret)
computed_code = sha_ctx.digest()[:16]
@ -185,7 +187,6 @@ def test_pairing_qr_code(client: Client) -> None:
protocol._has_valid_channel = True
@pytest.mark.skip("Cpace is not implemented yet")
def test_pairing_code_entry(client: Client) -> None:
global protocol
_prepare_protocol(client)
@ -213,7 +214,7 @@ def test_pairing_code_entry(client: Client) -> None:
commitment_msg = _read_message(ThpCodeEntryCommitment)
commitment = commitment_msg.commitment
challenge = b"\x00\x11\x22\x33\x44\x55\x66\x77\x88\x99\xAA\xBB\xCC\xDD\xEE\xFF"
challenge = random.randbytes(16)
_send_message(ThpCodeEntryChallenge(challenge=challenge))
cpace_trezor = _read_message(ThpCodeEntryCpaceTrezor)
@ -228,16 +229,15 @@ def test_pairing_code_entry(client: Client) -> None:
)
code = pairing_info.code_entry_code
# TODO fix missing CPACE
cpace_shared_secret = b"\x01"
sha_ctx = hashlib.sha256(cpace_shared_secret)
cpace = Cpace(handshake_hash=protocol.handshake_hash)
cpace.random_bytes = random.randbytes
cpace.generate_keys_and_secret(code.to_bytes(6, "big"), cpace_trezor_public_key)
sha_ctx = sha256(cpace.shared_secret)
tag = sha_ctx.digest()
cpace_host_public_key = cpace_trezor_public_key
_send_message(
ThpCodeEntryCpaceHostTag(
cpace_host_public_key=cpace_host_public_key,
cpace_host_public_key=cpace.host_public_key,
tag=tag,
)
)
@ -245,10 +245,17 @@ def test_pairing_code_entry(client: Client) -> None:
secret_msg = _read_message(ThpCodeEntrySecret)
# Check `commitment` and `code`
sha_ctx = hashlib.sha256(secret_msg.secret)
sha_ctx = sha256(secret_msg.secret)
computed_commitment = sha_ctx.digest()
assert commitment == computed_commitment
assert code == b"" # TODO implement
sha_ctx = sha256(ThpPairingMethod.CodeEntry.to_bytes(1, "big"))
sha_ctx.update(protocol.handshake_hash)
sha_ctx.update(secret_msg.secret)
sha_ctx.update(challenge)
code_hash = sha_ctx.digest()
computed_code = int.from_bytes(code_hash, "big") % 1000000
assert code == computed_code
_send_message(ThpEndRequest())
_read_message(ThpEndResponse)
@ -286,8 +293,7 @@ def test_pairing_nfc(client: Client) -> None:
_read_message(ButtonRequest)
_send_message(ButtonAck())
nfc_secret_host = b"\x02\x11\x22\x33\x44\x55\x66\x77\x88\x99\xAA\xBB\xCC\xDD\xEE\xFF" # TODO generate randomly
nfc_secret_host = random.randbytes(16)
# Read `nfc_secret` and `handshake_hash` from Trezor using debuglink
pairing_info = client.debug.pairing_info(
thp_channel_id=protocol.channel_id.to_bytes(2, "big"),
@ -300,7 +306,7 @@ def test_pairing_nfc(client: Client) -> None:
assert handshake_hash_trezor[:16] == protocol.handshake_hash[:16]
# Compute tag for response
sha_ctx = hashlib.sha256(ThpPairingMethod.NFC.to_bytes(1, "big"))
sha_ctx = sha256(ThpPairingMethod.NFC.to_bytes(1, "big"))
sha_ctx.update(protocol.handshake_hash)
sha_ctx.update(nfc_secret_trezor)
tag_host = sha_ctx.digest()
@ -310,7 +316,7 @@ def test_pairing_nfc(client: Client) -> None:
tag_trezor_msg = _read_message(ThpNfcTagTrezor)
# Check that the `code` was derived from the revealed secret
sha_ctx = hashlib.sha256(ThpPairingMethod.NFC.to_bytes(1, "big"))
sha_ctx = sha256(ThpPairingMethod.NFC.to_bytes(1, "big"))
sha_ctx.update(protocol.handshake_hash)
sha_ctx.update(nfc_secret_host)
computed_tag = sha_ctx.digest()