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Gilles Boccon-Gibod
2023-11-06 13:19:13 -08:00
parent c67ca4a09e
commit 4ae612090b
6 changed files with 347 additions and 36 deletions
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189
bumble/smp.py
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@@ -27,6 +27,7 @@ import logging
import asyncio
import enum
import secrets
from dataclasses import dataclass
from typing import (
TYPE_CHECKING,
Any,
@@ -53,6 +54,7 @@ from .core import (
BT_BR_EDR_TRANSPORT,
BT_CENTRAL_ROLE,
BT_LE_TRANSPORT,
AdvertisingData,
ProtocolError,
name_or_number,
)
@@ -563,6 +565,54 @@ class PairingMethod(enum.IntEnum):
CTKD_OVER_CLASSIC = 4
# -----------------------------------------------------------------------------
class OobContext:
"""Cryptographic context for LE SC OOB pairing."""
ecc_key: crypto.EccKey
r: bytes
def __init__(
self, ecc_key: Optional[crypto.EccKey] = None, r: Optional[bytes] = None
) -> None:
self.ecc_key = crypto.EccKey.generate() if ecc_key is None else ecc_key
self.r = crypto.r() if r is None else r
def share(self) -> OobSharedData:
pkx = bytes(reversed(self.ecc_key.x))
return OobSharedData(c=crypto.f4(pkx, pkx, self.r, bytes(1)), r=self.r)
# -----------------------------------------------------------------------------
class OobLegacyContext:
"""Cryptographic context for LE Legacy OOB pairing."""
tk: bytes
def __init__(self, tk: Optional[bytes] = None) -> None:
self.tk = crypto.r() if tk is None else tk
# -----------------------------------------------------------------------------
@dataclass
class OobSharedData:
"""Shareable data for LE SC OOB pairing."""
c: bytes
r: bytes
def to_ad(self) -> AdvertisingData:
return AdvertisingData(
[
(AdvertisingData.LE_SECURE_CONNECTIONS_CONFIRMATION_VALUE, self.c),
(AdvertisingData.LE_SECURE_CONNECTIONS_RANDOM_VALUE, self.r),
]
)
def __str__(self) -> str:
return f'OOB(C={self.c.hex()}, R={self.r.hex()})'
# -----------------------------------------------------------------------------
class Session:
# I/O Capability to pairing method decision matrix
@@ -640,8 +690,6 @@ class Session:
self.pres: Optional[bytes] = None
self.ea = None
self.eb = None
self.tk = bytes(16)
self.r = bytes(16)
self.stk = None
self.ltk = None
self.ltk_ediv = 0
@@ -659,7 +707,7 @@ class Session:
self.peer_bd_addr: Optional[Address] = None
self.peer_signature_key = None
self.peer_expected_distributions: List[Type[SMP_Command]] = []
self.dh_key = None
self.dh_key = b''
self.confirm_value = None
self.passkey: Optional[int] = None
self.passkey_ready = asyncio.Event()
@@ -712,8 +760,8 @@ class Session:
self.io_capability = pairing_config.delegate.io_capability
self.peer_io_capability = SMP_NO_INPUT_NO_OUTPUT_IO_CAPABILITY
# OOB (not supported yet)
self.oob = False
# OOB
self.oob_data_flag = 0 if pairing_config.oob is None else 1
# Set up addresses
self_address = connection.self_address
@@ -729,9 +777,37 @@ class Session:
self.ia = bytes(peer_address)
self.iat = 1 if peer_address.is_random else 0
# Select the ECC key, TK and r initial value
if pairing_config.oob:
self.peer_oob_data = pairing_config.oob.peer_data
if pairing_config.sc:
if pairing_config.oob.our_context is None:
raise ValueError(
"oob pairing config requires a context when sc is True"
)
self.r = pairing_config.oob.our_context.r
self.ecc_key = pairing_config.oob.our_context.ecc_key
if pairing_config.oob.legacy_context is None:
self.tk = None
else:
self.tk = pairing_config.oob.legacy_context.tk
else:
if pairing_config.oob.legacy_context is None:
raise ValueError(
"oob pairing config requires a legacy context when sc is False"
)
self.r = bytes(16)
self.ecc_key = manager.ecc_key
self.tk = pairing_config.oob.legacy_context.tk
else:
self.peer_oob_data = None
self.r = bytes(16)
self.ecc_key = manager.ecc_key
self.tk = bytes(16)
@property
def pkx(self) -> Tuple[bytes, bytes]:
return (bytes(reversed(self.manager.ecc_key.x)), self.peer_public_key_x)
return (bytes(reversed(self.ecc_key.x)), self.peer_public_key_x)
@property
def pka(self) -> bytes:
@@ -768,7 +844,10 @@ class Session:
return None
def decide_pairing_method(
self, auth_req: int, initiator_io_capability: int, responder_io_capability: int
self,
auth_req: int,
initiator_io_capability: int,
responder_io_capability: int,
) -> None:
if self.connection.transport == BT_BR_EDR_TRANSPORT:
self.pairing_method = PairingMethod.CTKD_OVER_CLASSIC
@@ -909,7 +988,7 @@ class Session:
command = SMP_Pairing_Request_Command(
io_capability=self.io_capability,
oob_data_flag=0,
oob_data_flag=self.oob_data_flag,
auth_req=self.auth_req,
maximum_encryption_key_size=16,
initiator_key_distribution=self.initiator_key_distribution,
@@ -921,7 +1000,7 @@ class Session:
def send_pairing_response_command(self) -> None:
response = SMP_Pairing_Response_Command(
io_capability=self.io_capability,
oob_data_flag=0,
oob_data_flag=self.oob_data_flag,
auth_req=self.auth_req,
maximum_encryption_key_size=16,
initiator_key_distribution=self.initiator_key_distribution,
@@ -982,8 +1061,8 @@ class Session:
def send_public_key_command(self) -> None:
self.send_command(
SMP_Pairing_Public_Key_Command(
public_key_x=bytes(reversed(self.manager.ecc_key.x)),
public_key_y=bytes(reversed(self.manager.ecc_key.y)),
public_key_x=bytes(reversed(self.ecc_key.x)),
public_key_y=bytes(reversed(self.ecc_key.y)),
)
)
@@ -1030,7 +1109,6 @@ class Session:
self.ltk = crypto.h6(ilk, b'brle')
def distribute_keys(self) -> None:
# Distribute the keys as required
if self.is_initiator:
# CTKD: Derive LTK from LinkKey
@@ -1296,7 +1374,7 @@ class Session:
try:
handler(command)
except Exception as error:
logger.warning(f'{color("!!! Exception in handler:", "red")} {error}')
logger.exception(f'{color("!!! Exception in handler:", "red")} {error}')
response = SMP_Pairing_Failed_Command(
reason=SMP_UNSPECIFIED_REASON_ERROR
)
@@ -1333,15 +1411,28 @@ class Session:
self.sc = self.sc and (command.auth_req & SMP_SC_AUTHREQ != 0)
self.ct2 = self.ct2 and (command.auth_req & SMP_CT2_AUTHREQ != 0)
# Check for OOB
if command.oob_data_flag != 0:
self.send_pairing_failed(SMP_OOB_NOT_AVAILABLE_ERROR)
return
# Infer the pairing method
if (self.sc and (self.oob_data_flag != 0 or command.oob_data_flag != 0)) or (
not self.sc and (self.oob_data_flag != 0 and command.oob_data_flag != 0)
):
# Use OOB
self.pairing_method = PairingMethod.OOB
if not self.sc and self.tk is None:
# For legacy OOB, TK is required.
logger.warning("legacy OOB without TK")
self.send_pairing_failed(SMP_OOB_NOT_AVAILABLE_ERROR)
return
if command.oob_data_flag == 0:
# The peer doesn't have OOB data, use r=0
self.r = bytes(16)
else:
# Decide which pairing method to use from the IO capability
self.decide_pairing_method(
command.auth_req,
command.io_capability,
self.io_capability,
)
# Decide which pairing method to use
self.decide_pairing_method(
command.auth_req, command.io_capability, self.io_capability
)
logger.debug(f'pairing method: {self.pairing_method.name}')
# Key distribution
@@ -1390,15 +1481,26 @@ class Session:
self.bonding = self.bonding and (command.auth_req & SMP_BONDING_AUTHREQ != 0)
self.sc = self.sc and (command.auth_req & SMP_SC_AUTHREQ != 0)
# Check for OOB
if self.sc and command.oob_data_flag:
self.send_pairing_failed(SMP_OOB_NOT_AVAILABLE_ERROR)
return
# Infer the pairing method
if (self.sc and (self.oob_data_flag != 0 or command.oob_data_flag != 0)) or (
not self.sc and (self.oob_data_flag != 0 and command.oob_data_flag != 0)
):
# Use OOB
self.pairing_method = PairingMethod.OOB
if not self.sc and self.tk is None:
# For legacy OOB, TK is required.
logger.warning("legacy OOB without TK")
self.send_pairing_failed(SMP_OOB_NOT_AVAILABLE_ERROR)
return
if command.oob_data_flag == 0:
# The peer doesn't have OOB data, use r=0
self.r = bytes(16)
else:
# Decide which pairing method to use from the IO capability
self.decide_pairing_method(
command.auth_req, self.io_capability, command.io_capability
)
# Decide which pairing method to use
self.decide_pairing_method(
command.auth_req, self.io_capability, command.io_capability
)
logger.debug(f'pairing method: {self.pairing_method.name}')
# Key distribution
@@ -1549,12 +1651,13 @@ class Session:
if self.passkey_step < 20:
self.send_pairing_confirm_command()
return
else:
elif self.pairing_method != PairingMethod.OOB:
return
else:
if self.pairing_method in (
PairingMethod.JUST_WORKS,
PairingMethod.NUMERIC_COMPARISON,
PairingMethod.OOB,
):
self.send_pairing_random_command()
elif self.pairing_method == PairingMethod.PASSKEY:
@@ -1591,6 +1694,7 @@ class Session:
if self.pairing_method in (
PairingMethod.JUST_WORKS,
PairingMethod.NUMERIC_COMPARISON,
PairingMethod.OOB,
):
ra = bytes(16)
rb = ra
@@ -1599,7 +1703,6 @@ class Session:
ra = self.passkey.to_bytes(16, byteorder='little')
rb = ra
else:
# OOB not implemented yet
return
assert self.preq and self.pres
@@ -1653,7 +1756,7 @@ class Session:
# Compute the DH key
self.dh_key = bytes(
reversed(
self.manager.ecc_key.dh(
self.ecc_key.dh(
bytes(reversed(command.public_key_x)),
bytes(reversed(command.public_key_y)),
)
@@ -1661,8 +1764,27 @@ class Session:
)
logger.debug(f'DH key: {self.dh_key.hex()}')
if self.pairing_method == PairingMethod.OOB:
# Check against shared OOB data
if self.peer_oob_data:
confirm_verifier = crypto.f4(
self.peer_public_key_x,
self.peer_public_key_x,
self.peer_oob_data.r,
bytes(1),
)
if not self.check_expected_value(
self.peer_oob_data.c,
confirm_verifier,
SMP_CONFIRM_VALUE_FAILED_ERROR,
):
return
if self.is_initiator:
self.send_pairing_confirm_command()
if self.pairing_method == PairingMethod.OOB:
self.send_pairing_random_command()
else:
self.send_pairing_confirm_command()
else:
if self.pairing_method == PairingMethod.PASSKEY:
self.display_or_input_passkey()
@@ -1673,6 +1795,7 @@ class Session:
if self.pairing_method in (
PairingMethod.JUST_WORKS,
PairingMethod.NUMERIC_COMPARISON,
PairingMethod.OOB,
):
# We can now send the confirmation value
self.send_pairing_confirm_command()