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apps.fido_u2f: first impl of msg_authenticate

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This commit is contained in:
Jan Pochyla 2017-05-30 19:08:18 +02:00
parent 479ff127fc
commit 36fc87bd46
1 changed files with 171 additions and 11 deletions
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166
src/apps/fido_u2f/__init__.py
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@ -64,6 +64,11 @@ _U2F_REGISTER_ID = const(0x05) # version 2 registration identifier
_U2F_ATT_PRIV_KEY = b"q&\xac+\xf6D\xdca\x86\xad\x83\xef\x1f\xcd\xf1*W\xb5\xcf\xa2\x00\x0b\x8a\xd0'\xe9V\xe8T\xc5\n\x8b"
_U2F_ATT_CERT = b"0\x82\x01\x180\x81\xc0\x02\t\x00\xb1\xd9\x8fBdr\xd3,0\n\x06\x08*\x86H\xce=\x04\x03\x020\x151\x130\x11\x06\x03U\x04\x03\x0c\nTrezor U2F0\x1e\x17\r160429133153Z\x17\r260427133153Z0\x151\x130\x11\x06\x03U\x04\x03\x0c\nTrezor U2F0Y0\x13\x06\x07*\x86H\xce=\x02\x01\x06\x08*\x86H\xce=\x03\x01\x07\x03B\x00\x04\xd9\x18\xbd\xfa\x8aT\xac\x92\xe9\r\xa9\x1f\xcaz\xa2dT\xc0\xd1s61M\xde\x83\xa5K\x86\xb5\xdfN\xf0Re\x9a\x1do\xfc\xb7F\x7f\x1a\xcd\xdb\x8a3\x08\x0b^\xed\x91\x89\x13\xf4C\xa5&\x1b\xc7{h`o\xc10\n\x06\x08*\x86H\xce=\x04\x03\x02\x03G\x000D\x02 $\x1e\x81\xff\xd2\xe5\xe6\x156\x94\xc3U.\x8f\xeb\xd7\x1e\x895\x92\x1c\xb4\x83ACq\x1cv\xea\xee\xf3\x95\x02 _\x80\xeb\x10\xf2\\\xcc9\x8b<\xa8\xa9\xad\xa4\x02\x7f\x93\x13 w\xb7\xab\xcewFZ'\xf5=3\xa1\x1d"
# authentication control byte
_AUTH_ENFORCE = const(0x03) # enforce user presence and sign
_AUTH_CHECK_ONLY = const(0x07) # check only
_AUTH_FLAG_TUP = const(0x01) # test of user presence set
# common raw message format (ISO7816-4:2005 mapping)
_APDU_CLA = const(0) # uint8_t cla; // Class - reserved
_APDU_INS = const(1) # uint8_t ins; // U2F instruction
@ -141,6 +146,37 @@ def resp_cmd_register(khlen: int, certlen: int, siglen: int) -> dict:
}
# index of keyHandleLen in req_cmd_authenticate struct
_REQ_CMD_AUTHENTICATE_KHLEN = const(64)
def req_cmd_authenticate(khlen: int) -> dict:
# uint8_t chal[32]; // Challenge
# uint8_t appId[32]; // Application id
# uint8_t keyHandleLen; // Length of key handle
# uint8_t keyHandle[khlen]; // Key handle
return {
'chal': (0 | uctypes.ARRAY, 32 | uctypes.UINT8),
'appId': (32 | uctypes.ARRAY, 32 | uctypes.UINT8),
'keyHandleLen': 64 | uctypes.UINT8,
'keyHandle': (65 | uctypes.ARRAY, khlen | uctypes.UINT8),
}
def resp_cmd_authenticate(siglen: int) -> dict:
status_ofs = 5 + siglen
# uint8_t flags; // U2F_AUTH_FLAG_ values
# uint32_t ctr; // Counter field (big-endian)
# uint8_t sig[siglen]; // Signature
# uint16_t status;
return {
'flags': 0 | uctypes.UINT8,
'ctr': 1 | uctypes.UINT32,
'sig': (5 | uctypes.ARRAY, siglen | uctypes.UINT8),
'status': status_ofs | uctypes.UINT16,
}
def overlay_struct(buf, desc):
desc_size = uctypes.sizeof(desc, uctypes.BIG_ENDIAN)
if desc_size > len(buf):
@ -164,19 +200,23 @@ class Cmd:
def to_msg(self):
cla = self.data[_APDU_CLA]
ins = self.data[_APDU_INS]
p1 = self.data[_APDU_P1]
p2 = self.data[_APDU_P2]
lc = (self.data[_APDU_LC1] << 16) + \
(self.data[_APDU_LC2] << 8) + \
(self.data[_APDU_LC3])
data = self.data[_APDU_DATA:_APDU_DATA + lc]
return Msg(self.cid, cla, ins, lc, data)
return Msg(self.cid, cla, ins, p1, p2, lc, data)
class Msg:
def __init__(self, cid: int, cla: int, ins: int, lc: int, data: bytes):
def __init__(self, cid: int, cla: int, ins: int, p1: int, p2: int, lc: int, data: bytes):
self.cid = cid
self.cla = cla
self.ins = ins
self.p1 = p1
self.p2 = p2
self.lc = lc
self.data = data
@ -420,8 +460,128 @@ def msg_register_sign(challenge: bytes, app_id: bytes) -> bytes:
return buf
_authenticate_state = 0
async def msg_authenticate(req: Msg) -> Cmd:
pass
global _authenticate_state
from apps.common import storage
if not storage.is_initialized():
return msg_error(req, _SW_CONDITIONS_NOT_SATISFIED)
# we need at least keyHandleLen
if len(req.data) <= _REQ_CMD_AUTHENTICATE_KHLEN:
log.warning(__name__, '_SW_WRONG_LENGTH req.data')
return msg_error(req, _SW_WRONG_LENGTH)
# check keyHandleLen
khlen = req.data[_REQ_CMD_AUTHENTICATE_KHLEN]
if khlen != 64:
log.warning(__name__, '_SW_WRONG_LENGTH khlen')
return msg_error(req, _SW_WRONG_LENGTH)
auth = overlay_struct(req.data, req_cmd_authenticate(khlen))
# check the keyHandle and generate the signing key
node = msg_authenticate_genkey(auth.appId, auth.keyHandle)
if node is None:
return msg_error(req, _SW_WRONG_DATA)
# if _AUTH_CHECK_ONLY is requested, return, because keyhandle has been checked already
if req.p1 == _AUTH_CHECK_ONLY:
log.warning(__name__, '_SW_CONDITIONS_NOT_SATISFIED')
return msg_error(req, _SW_CONDITIONS_NOT_SATISFIED)
# from now on, only _AUTH_ENFORCE is supported
if req.p1 != _AUTH_ENFORCE:
log.warning(__name__, '_SW_WRONG_DATA')
return msg_error(req, _SW_WRONG_DATA)
# TODO: check equality with last request
# TODO: wait for a button press
if _authenticate_state == 0:
_authenticate_state = utime.ticks_ms()
if utime.ticks_ms() - _authenticate_state < 500:
return msg_error(req, _SW_CONDITIONS_NOT_SATISFIED)
_authenticate_state = 0
buf = msg_authenticate_sign(auth.chal, auth.appId, auth.keyHandle)
return Cmd(req.cid, _CMD_MSG, buf)
def msg_authenticate_genkey(app_id: bytes, keyhandle: bytes):
from apps.common import seed
# unpack the keypath from the first half of keyhandle
keybuf = keyhandle[:32]
keypath = ustruct.unpack('>8L', keybuf)
# check high bit for hardened keys
for i in keypath:
if not i & 0x80000000:
log.warning(__name__, 'invalid key path')
return None
# derive the signing key
nodepath = [_U2F_KEY_PATH] + list(keypath)
node = seed.get_root_without_passphrase('nist256p1')
node.derive_path(nodepath)
# second half of keyhandle is a hmac of app_id and keypath
keybase = hmac.Hmac(node.private_key(), app_id, hashlib.sha256)
keybase.update(keybuf)
keybase = keybase.digest()
# verify the hmac
if keybase != keyhandle[32:]:
log.warning(__name__, 'invalid key handle')
return None
return node
# TODO: persistent counter
_authenticate_ctr = 0
def msg_authenticate_sign(challenge: bytes, app_id: bytes, privkey: bytes) -> bytes:
global _authenticate_ctr
flags = _AUTH_FLAG_TUP
# get next counter
ctr = _authenticate_ctr
ctrbuf = ustruct.pack('>L', ctr)
_authenticate_ctr += 1
# hash input data together with counter
dig = hashlib.sha256()
dig.update(app_id) # uint8_t appId[32];
dig.update(flags) # uint8_t flags;
dig.update(ctrbuf) # uint8_t ctr[4];
dig.update(challenge) # uint8_t chal[32];
dig = dig.digest()
# sign the digest and convert to der
sig = nist256p1.sign(privkey, dig, False)
sig = der.encode_seq((sig[1:33], sig[33:]))
# pack to a response
buf, resp = make_struct(resp_cmd_authenticate(len(sig)))
resp.flags = flags
resp.ctr = ctr
utils.memcpy(resp.sig, 0, sig, 0, len(sig))
resp.status = _SW_NO_ERROR
return buf
def msg_version(req: Msg) -> Cmd: