laforge has uploaded this change for review. (
https://gerrit.osmocom.org/c/pysim/+/35793?usp=email )
Change subject: WIP: Implement Global Platform SCP03
......................................................................
WIP: Implement Global Platform SCP03
Change-Id: Ibc35af5474923aed2e3bcb29c8d713b4127a160d
---
M pySim/global_platform/__init__.py
M pySim/global_platform/scp02.py
M tests/test_globalplatform.py
3 files changed, 323 insertions(+), 25 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/pysim refs/changes/93/35793/1
diff --git a/pySim/global_platform/__init__.py
b/pySim/global_platform/__init__.py
index 48e3fe0..7d3ecbb 100644
--- a/pySim/global_platform/__init__.py
+++ b/pySim/global_platform/__init__.py
@@ -20,9 +20,10 @@
from typing import Optional, List, Dict, Tuple
from construct import Optional as COptional
from construct import *
+from copy import deepcopy
from bidict import bidict
from Cryptodome.Random import get_random_bytes
-from pySim.global_platform.scp02 import SCP02
+from pySim.global_platform.scp02 import SCP02, SCP03
from pySim.construct import *
from pySim.utils import *
from pySim.filesystem import *
@@ -650,16 +651,37 @@
host_challenge = h2b(opts.host_challenge) if opts.host_challenge
else get_random_bytes(8)
kset = GpCardKeyset(opts.key_ver, h2b(opts.key_enc),
h2b(opts.key_mac), h2b(opts.key_dek))
scp02 = SCP02(card_keys=kset)
- init_update_apdu =
scp02.gen_init_update_apdu(host_challenge=host_challenge)
+ self._establish_scp(scp02, host_challenge, opts.security_level)
+
+ est_scp03_parser = deepcopy(est_scp02_parser)
+ est_scp03_parser.add_argument('--s8-mode', action='store_true',
help='S8 mode (legacy mode)')
+
+ @cmd2.with_argparser(est_scp03_parser)
+ def do_establish_scp03(self, opts):
+ """Establish a secure channel using the GlobalPlatform SCP03
protocol. It can be released
+ again by using `release_scp`."""
+ if self._cmd.lchan.scc.scp:
+ self._cmd.poutput("Cannot establish SCP03 as this lchan
already has a SCP instance!")
+ return
+ s_mode = 8 if opts.s8_mode else 16
+ host_challenge = h2b(opts.host_challenge) if opts.host_challenge
else get_random_bytes(s_mode)
+ kset = GpCardKeyset(opts.key_ver, h2b(opts.key_enc),
h2b(opts.key_mac), h2b(opts.key_dek))
+ scp03 = SCP03(card_keys=kset, s_mode = s_mode)
+ self._establish_scp(scp03, host_challenge, opts.security_level)
+
+ def _establish_scp(self, scp, host_challenge, security_level):
+ # perform the common functionality shared by SCP02 and SCP03
establishment
+ init_update_apdu =
scp.gen_init_update_apdu(host_challenge=host_challenge)
init_update_resp, sw =
self._cmd.lchan.scc.send_apdu_checksw(b2h(init_update_apdu))
- scp02.parse_init_update_resp(h2b(init_update_resp))
- ext_auth_apdu = scp02.gen_ext_auth_apdu(opts.security_level)
+ scp.parse_init_update_resp(h2b(init_update_resp))
+ ext_auth_apdu = scp.gen_ext_auth_apdu(security_level)
ext_auth_resp, sw =
self._cmd.lchan.scc.send_apdu_checksw(b2h(ext_auth_apdu))
- self._cmd.poutput("Successfully established a SCP02 secure
channel")
+ self._cmd.poutput("Successfully established a %s secure channel" %
str(scp))
# store a reference to the SCP instance
- self._cmd.lchan.scc.scp = scp02
+ self._cmd.lchan.scc.scp = scp
self._cmd.update_prompt()
+
def do_release_scp(self, opts):
"""Release a previously establiehed secure channel."""
if not self._cmd.lchan.scc.scp:
diff --git a/pySim/global_platform/scp02.py b/pySim/global_platform/scp02.py
index 3f34407..cc3f0ed 100644
--- a/pySim/global_platform/scp02.py
+++ b/pySim/global_platform/scp02.py
@@ -17,13 +17,16 @@
import abc
import logging
+from typing import Optional
from Cryptodome.Cipher import DES3, DES
from Cryptodome.Util.strxor import strxor
-from construct import *
+from construct import Struct, Bytes, Int8ub, Int16ub, Const
+from construct import Optional as COptional
from pySim.utils import b2h
from pySim.secure_channel import SecureChannel
logger = logging.getLogger(__name__)
+logger.setLevel(logging.DEBUG)
def scp02_key_derivation(constant: bytes, counter: int, base_key: bytes) ->
bytes:
assert(len(constant) == 2)
@@ -34,11 +37,21 @@
cipher = DES3.new(base_key, DES.MODE_CBC, b'\x00' * 8)
return cipher.encrypt(derivation_data)
+# FIXME: BspAlgoCryptAES128
def pad80(s: bytes, BS=8) -> bytes:
""" Pad bytestring s: add '\x80' and '\0'* so the result to be multiple of
BS."""
l = BS-1 - len(s) % BS
return s + b'\x80' + b'\0'*l
+# FIXME: BspAlgoCryptAES128
+def unpad80(padded: bytes) -> bytes:
+ """Remove the customary 80 00 00 ... padding used for AES."""
+ # first remove any trailing zero bytes
+ stripped = padded.rstrip(b'\0')
+ # then remove the final 80
+ assert stripped[-1] == 0x80
+ return stripped[:-1]
+
class Scp02SessionKeys:
"""A single set of GlobalPlatform session keys."""
DERIV_CONST_CMAC = b'\x01\x01'
@@ -102,6 +115,27 @@
self.mac_on_unmodified = False
self.security_level = 0x00
+ @property
+ def do_cmac(self) -> bool:
+ """Should we perform C-MAC?"""
+ return self.security_level & 0x01
+
+ @property
+ def do_rmac(self) -> bool:
+ """Should we perform R-MAC?"""
+ return self.security_level & 0x10
+
+ @property
+ def do_cenc(self) -> bool:
+ """Should we perform C-ENC?"""
+ return self.security_level & 0x02
+
+ @property
+ def do_renc(self) -> bool:
+ """Should we perform R-ENC?"""
+ return self.security_level & 0x20
+
+
def __str__(self) -> str:
return "%s[%02x]" % (self.__class__.__name__, self.security_level)
@@ -111,10 +145,10 @@
ret = ret | CLA_SM
return ret + self.lchan_nr
- def wrap_cmd_apdu(self, apdu: bytes) -> bytes:
+ def wrap_cmd_apdu(self, apdu: bytes, *args, **kwargs) -> bytes:
# only protect those APDUs that actually are global platform commands
if apdu[0] & 0x80:
- return self._wrap_cmd_apdu(apdu)
+ return self._wrap_cmd_apdu(apdu, *args, **kwargs)
else:
return apdu
@@ -150,21 +184,6 @@
if self.card_cryptogram != resp['card_cryptogram']:
raise ValueError("card cryptogram doesn't match")
- @property
- def do_cmac(self) -> bool:
- """Should we perform C-MAC?"""
- return self.security_level & 0x01
-
- @property
- def do_rmac(self) -> bool:
- """Should we perform R-MAC?"""
- return self.security_level & 0x10
-
- @property
- def do_cenc(self) -> bool:
- """Should we perform C-ENC?"""
- return self.security_level & 0x02
-
def gen_ext_auth_apdu(self, security_level: int =0x01) -> bytes:
"""Generate EXTERNAL AUTHENTICATE APDU."""
self.security_level = security_level
@@ -211,3 +230,224 @@
def unwrap_rsp_apdu(self, sw: bytes, apdu: bytes) -> bytes:
# TODO: Implement R-MAC / R-ENC
return apdu
+
+
+
+from Cryptodome.Cipher import AES
+from Cryptodome.Hash import CMAC
+
+def scp03_key_derivation(constant: bytes, context: bytes, base_key: bytes, l:
Optional[int] = None) -> bytes:
+ """SCP03 Key Derivation Function as specified in Annex D 4.1.5."""
+ # Data derivation shall use KDF in counter mode as specified in NIST SP
800-108 ([NIST 800-108]). The PRF
+ # used in the KDF shall be CMAC as specified in [NIST 800-38B], used with
full 16-byte output length.
+ def prf(key: bytes, data:bytes):
+ return CMAC.new(key, data, AES).digest()
+
+ if l == None:
+ l = len(base_key) * 8
+
+ logger.warn("scp03_kdf(constant=%s, context=%s, base_key=%s, l=%u",
b2h(constant), b2h(context), b2h(base_key), l)
+
+ output_len = l // 8
+
+ # SCP03 Section 4.1.5 defines a different parameter order than NIST SP
800-108, so we cannot use the
+ # existing Cryptodome.Protocol.KDF.SP800_108_Counter function :(
+ # A 12-byte “label” consisting of 11 bytes with value '00' followed by a
1-byte derivation constant
+ assert len(constant) == 1
+ label = b'\x00' *11 + constant
+ i = 1
+ dk = b''
+ while len(dk) < output_len:
+ # 12B label, 1B separation, 2B L, 1B i, Context
+ info = label + b'\x00' + l.to_bytes(2, 'big') + bytes([i]) + context
+ logger.warn('info=%s', b2h(info))
+ dk += prf(base_key, info)
+ i += 1
+ if i > 0xffff:
+ raise ValueError("Overflow in SP800 108 counter")
+
+ print("DK: %s" % b2h(dk))
+ return dk[:output_len]
+
+
+class Scp03SessionKeys:
+ # GPC 2.3 Amendment D v1.2 Section 4.1.5 Table 4-1
+ DERIV_CONST_AUTH_CGRAM_CARD = b'\x00'
+ DERIV_CONST_AUTH_CGRAM_HOST = b'\x01'
+ DERIV_CONST_CARD_CHLG_GEN = b'\x02'
+ DERIV_CONST_KDERIV_S_ENC = b'\x04'
+ DERIV_CONST_KDERIV_S_MAC = b'\x06'
+ DERIV_CONST_KDERIV_S_RMAC = b'\x07'
+ blocksize = 16
+
+ def __init__(self, card_keys: 'GpCardKeyset', host_challenge: bytes,
card_challenge: bytes):
+ # GPC 2.3 Amendment D v1.2 Section 6.2.1
+ context = host_challenge + card_challenge
+ self.s_enc = scp03_key_derivation(self.DERIV_CONST_KDERIV_S_ENC,
context, card_keys.enc)
+ self.s_mac = scp03_key_derivation(self.DERIV_CONST_KDERIV_S_MAC,
context, card_keys.mac)
+ self.s_rmac = scp03_key_derivation(self.DERIV_CONST_KDERIV_S_RMAC,
context, card_keys.mac)
+
+
+ # The first MAC chaining value is set to 16 bytes '00'
+ self.mac_chaining_value = b'\x00' * 16
+ # The encryption counter’s start value shall be set to 1 (we set it
immediately before generating ICV)
+ self.block_nr = 0
+
+ def calc_cmac(self, apdu: bytes):
+ """Compute C-MAC for given to-be-transmitted APDU."""
+ cmac_input = self.mac_chaining_value + apdu
+ cmac_val = CMAC.new(self.s_mac, cmac_input, ciphermod=AES).digest()
+ self.mac_chaining_value = cmac_val
+ return cmac_val
+
+ def calc_rmac(self, rdata_and_sw: bytes):
+ """Compute R-MAC for given received R-APDU data section."""
+ rmac_input = self.mac_chaining_value + rdata_and_sw
+ return CMAC.new(self.s_rmac, rmac_input, ciphermod=AES).digest()
+
+ def _get_icv(self, is_response: bool = False):
+ """Obtain the ICV value computed as described in 6.2.6."""
+ if not is_response:
+ self.block_nr += 1
+ # The binary value of this number SHALL be left padded with zeroes to
form a full block.
+ data = self.block_nr.to_bytes(self.blocksize, "big")
+ if is_response:
+ # Section 6.2.7: additional intermediate step: Before encryption,
the most significant byte of
+ # this block shall be set to '80'.
+ data = b'\x80' + data[1:]
+ iv = bytes([0] * self.blocksize)
+ # This block SHALL be encrypted with S-ENC to produce the ICV for
command encryption.
+ cipher = AES.new(self.s_enc, AES.MODE_CBC, iv)
+ icv = cipher.encrypt(data)
+ logger.debug("_get_icv(data=%s, is_resp=%s) -> icv=%s", b2h(data),
is_response, b2h(icv))
+ return icv
+
+ def _encrypt(self, data: bytes, is_response: bool = False) -> bytes:
+ cipher = AES.new(self.s_enc, AES.MODE_CBC, self._get_icv(is_response))
+ return cipher.encrypt(data)
+
+ def _decrypt(self, data: bytes, is_response: bool = True) -> bytes:
+ cipher = AES.new(self.s_enc, AES.MODE_CBC, self._get_icv(is_response))
+ return cipher.decrypt(data)
+
+
+class SCP03(SCP):
+ """Secure Channel Protocol (SCP) 03 as specified in GlobalPlatform v2.3
Amendment D."""
+
+ # Section 7.1.1.6 / Table 7-3
+ constr_iur = Struct('key_div_data'/Bytes(10), 'key_ver'/Int8ub,
Const(b'\x03'), 'i_param'/Int8ub,
+ 'card_challenge'/Bytes(lambda ctx: ctx._.s_mode),
+ 'card_cryptogram'/Bytes(lambda ctx: ctx._.s_mode),
+ 'sequence_counter'/COptional(Bytes(3)))
+
+ def __init__(self, *args, **kwargs):
+ self.s_mode = kwargs.pop('s_mode', 8)
+ super().__init__(*args, **kwargs)
+
+ def _compute_cryptograms(self):
+ logger.debug("host_challenge(%s), card_challenge(%s)",
b2h(self.host_challenge), b2h(self.card_challenge))
+ # Card + Host Authentication Cryptogram: Section 6.2.2.2 + 6.2.2.3
+ context = self.host_challenge + self.card_challenge
+ self.card_cryptogram =
scp03_key_derivation(self.sk.DERIV_CONST_AUTH_CGRAM_CARD, context,
self.sk.s_mac, l=self.s_mode*8)
+ self.host_cryptogram =
scp03_key_derivation(self.sk.DERIV_CONST_AUTH_CGRAM_HOST, context,
self.sk.s_mac, l=self.s_mode*8)
+ logger.debug("host_cryptogram(%s), card_cryptogram(%s)",
b2h(self.host_cryptogram), b2h(self.card_cryptogram))
+
+ def gen_init_update_apdu(self, host_challenge: Optional[bytes] = None) ->
bytes:
+ """Generate INITIALIZE UPDATE APDU."""
+ if host_challenge == None:
+ host_challenge = b'\x00' * self.s_mode
+ if len(host_challenge) != self.s_mode:
+ raise ValueError('Host Challenge must be %u bytes long' %
self.s_mode)
+ self.host_challenge = host_challenge
+ return bytes([self._cla(), INS_INIT_UPDATE, self.card_keys.kvn, 0,
len(host_challenge)]) + host_challenge
+
+ def parse_init_update_resp(self, resp_bin: bytes):
+ """Parse response to INITIALIZE UPDATE."""
+ if len(resp_bin) not in [10+3+8+8, 10+3+16+16, 10+3+8+8+3,
10+3+16+16+3]:
+ raise ValueError('Invalid length of Initialize Update Response')
+ resp = self.constr_iur.parse(resp_bin, s_mode=self.s_mode)
+ self.card_challenge = resp['card_challenge']
+ self.i_param = resp['i_param']
+ # derive session keys and compute cryptograms
+ self.sk = Scp03SessionKeys(self.card_keys, self.host_challenge,
self.card_challenge)
+ logger.debug(self.sk)
+ self._compute_cryptograms()
+ # verify computed cryptogram matches received cryptogram
+ if self.card_cryptogram != resp['card_cryptogram']:
+ raise ValueError("card cryptogram doesn't match")
+
+ def gen_ext_auth_apdu(self, security_level: int = 0x01) -> bytes:
+ """Generate EXTERNAL AUTHENTICATE APDU."""
+ self.security_level = security_level
+ header = bytes([self._cla(), INS_EXT_AUTH, self.security_level, 0,
self.s_mode])
+ # bypass encryption for EXTERNAL AUTHENTICATE
+ return self.wrap_cmd_apdu(header + self.host_cryptogram,
skip_cenc=True)
+
+ def _wrap_cmd_apdu(self, apdu: bytes, skip_cenc: bool = False) -> bytes:
+ """Wrap Command APDU for SCP02: calculate MAC and encrypt."""
+ cla = apdu[0]
+ ins = apdu[1]
+ p1 = apdu[2]
+ p2 = apdu[3]
+ lc = apdu[4]
+ assert lc == len(apdu) - 5
+ cmd_data = apdu[5:]
+
+ if self.do_cenc and not skip_cenc:
+ assert self.do_cmac
+ if lc == 0:
+ # No encryption shall be applied to a command where there is
no command data field. In this
+ # case, the encryption counter shall still be incremented
+ self.sk.block_nr += 1
+ else:
+ # data shall be padded as defined in [GPCS] section B.2.3
+ padded_data = pad80(cmd_data, 16)
+ lc = len(padded_data)
+ if lc >= 256:
+ raise ValueError('Modified Lc (%u) would exceed maximum
when appending padding' % (lc, self.s_mode))
+ # perform AES-CBC with ICV + S_ENC
+ cmd_data = self.sk._encrypt(padded_data)
+
+ if self.do_cmac:
+ # The length of the command message (Lc) shall be incremented by 8
(in S8 mode) or 16 (in S16
+ # mode) to indicate the inclusion of the C-MAC in the data field
of the command message.
+ mlc = lc + self.s_mode
+ if mlc >= 256:
+ raise ValueError('Modified Lc (%u) would exceed maximum when
appending %u bytes of mac' % (mlc, self.s_mode))
+ # The class byte shall be modified for the generation or
verification of the C-MAC: The logical
+ # channel number shall be set to zero, bit 4 shall be set to 0 and
bit 3 shall be set to 1 to indicate
+ # GlobalPlatform proprietary secure messaging.
+ mcla = (cla & 0xF0) | CLA_SM
+ mapdu = bytes([mcla, ins, p1, p2, mlc]) + cmd_data
+ cmac = self.sk.calc_cmac(mapdu)
+ mapdu += cmac[:self.s_mode]
+
+ return mapdu
+
+ def unwrap_rsp_apdu(self, sw: bytes, apdu: bytes) -> bytes:
+ # No R-MAC shall be generated and no protection shall be applied to a
response that includes an error
+ # status word: in this case only the status word shall be returned in
the response. All status words
+ # except '9000' and warning status words (i.e. '62xx' and '63xx')
shall be interpreted as error status
+ # words.
+ print("unwrap_rsp_apdu(sw=%s, apdu=%s)" % (sw, apdu))
+ if not self.do_rmac:
+ assert not self.do_renc
+ return apdu
+
+ if sw != b'\x90\x00' and sw[0] not in [0x62, 0x63]:
+ return apdu
+ response_data = apdu[:-self.s_mode]
+ rmac = apdu[-self.s_mode:]
+ rmac_exp = self.sk.calc_rmac(response_data + sw)[:self.s_mode]
+ if rmac != rmac_exp:
+ raise ValueError("R-MAC value not matching: received: %s,
computed: %s" % (rmac, rmac_exp))
+
+ if self.do_renc:
+ # decrypt response data
+ decrypted = self.sk._decrypt(response_data)
+ print("decrypted: %s" % b2h(decrypted))
+ # remove padding
+ response_data = unpad80(decrypted)
+ print("response_data: %s" % b2h(response_data))
+
+ return response_data
diff --git a/tests/test_globalplatform.py b/tests/test_globalplatform.py
index 2c5e4d4..ade3224 100644
--- a/tests/test_globalplatform.py
+++ b/tests/test_globalplatform.py
@@ -19,7 +19,7 @@
import logging
from pySim.global_platform import *
-from pySim.global_platform.scp02 import SCP02
+from pySim.global_platform.scp02 import *
from pySim.utils import b2h, h2b
KIC = h2b('100102030405060708090a0b0c0d0e0f') # enc
@@ -64,5 +64,32 @@
wrapped = self.scp02.wrap_cmd_apdu(h2b('80f28002024f00'))
self.assertEqual(b2h(wrapped).upper(),
'84F280020A4F00B21AAFA3EB2D1672')
+class SCP03_Test_KDF(unittest.TestCase):
+ host_challenge = h2b('73EAE173050D0459')
+ # 00000000000000000000 300370 EE29D4C614C2DE31 CD5153A4F5758F91 00000F
+ card_challenge = h2b('EE29D4C614C2DE31')
+
+ def test_kdf_enc(self):
+ k_enc = h2b('000102030405060708090a0b0c0d0e0f')
+ s_enc =
scp03_key_derivation(Scp03SessionKeys.DERIV_CONST_KDERIV_S_ENC,
self.host_challenge + self.card_challenge, k_enc)
+ self.assertEqual(b2h(s_enc),
'D948BCF4878524EBC76EA403DC5A2116'.lower())
+
+ def test_kdf_mac(self):
+ k_mac = h2b('101112131415161718191A1B1C1D1E1F')
+ s_mac =
scp03_key_derivation(Scp03SessionKeys.DERIV_CONST_KDERIV_S_MAC,
self.host_challenge + self.card_challenge, k_mac)
+ self.assertEqual(b2h(s_mac),
'C27EB5E7827A833CA00BD3F436F7B4E5'.lower())
+
+ def test_kdf_rmac(self):
+ k_mac = h2b('101112131415161718191A1B1C1D1E1F')
+ s_rmac =
scp03_key_derivation(Scp03SessionKeys.DERIV_CONST_KDERIV_S_RMAC,
self.host_challenge + self.card_challenge, k_mac)
+ self.assertEqual(b2h(s_rmac),
'B4797059FD825F2BC824F6EC92052948'.lower())
+
+ def test_cardchallenge(self):
+ k_enc = h2b('000102030405060708090a0b0c0d0e0f')
+ aid = h2b('a0000005591010ffffffff8900000100')
+ counter = h2b('00000f')
+ ch_comp =
scp03_key_derivation(Scp03SessionKeys.DERIV_CONST_AUTH_CGRAM_CARD, counter +
aid, k_enc, 8*8)
+ self.assertEqual(b2h(ch_comp), b2h(self.card_challenge))
+
if __name__ == "__main__":
unittest.main()
--
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Gerrit-Project: pysim
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Gerrit-Change-Id: Ibc35af5474923aed2e3bcb29c8d713b4127a160d
Gerrit-Change-Number: 35793
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Gerrit-Owner: laforge <[email protected]>
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