laforge has submitted this change. ( https://gerrit.osmocom.org/c/pysim/+/37141?usp=email )
Change subject: pySim.ota.OtaDialectSms: Implement command decoding ......................................................................
pySim.ota.OtaDialectSms: Implement command decoding
So far we only implemented command encoding and response decoding. Let's also add command decoding, which is useful for example when decoding protocol traces.
Change-Id: Id666cea8a91a854209f3c19c1f09b512bb493c85 --- M pySim/ota.py M tests/test_ota.py 2 files changed, 79 insertions(+), 7 deletions(-)
Approvals: laforge: Looks good to me, approved osmith: Looks good to me, but someone else must approve Jenkins Builder: Verified
diff --git a/pySim/ota.py b/pySim/ota.py index d77a64e..c3a7512 100644 --- a/pySim/ota.py +++ b/pySim/ota.py @@ -18,7 +18,7 @@ import zlib import abc import struct -from typing import Optional +from typing import Optional, Tuple from construct import Enum, Int8ub, Int16ub, Struct, Bytes, GreedyBytes, BitsInteger, BitStruct from construct import Flag, Padding, Switch, this
@@ -388,6 +388,49 @@
return envelope_data
+ def decode_cmd(self, otak: OtaKeyset, encoded: bytes) -> Tuple[bytes, dict, bytes]: + """Decode an encoded (encrypted, signed) OTA SMS Command-APDU.""" + if True: # TODO: how to decide? + cpl = int.from_bytes(encoded[:2], 'big') + part_head = encoded[2:2+8] + ciph = encoded[2+8:] + envelope_data = otak.crypt.decrypt(ciph) + else: + part_head = encoded[:8] + envelope_data = encoded[8:] + + hdr_dec = self.hdr_construct.parse(part_head) + + # strip counter part from front of envelope_data + part_cnt = envelope_data[:6] + cntr = int.from_bytes(part_cnt[:5], 'big') + pad_cnt = int.from_bytes(part_cnt[5:], 'big') + envelope_data = envelope_data[6:] + + spi = hdr_dec['spi'] + if spi['rc_cc_ds'] == 'cc': + # split cc from front of APDU + cc = envelope_data[:8] + apdu = envelope_data[8:] + # verify CC + temp_data = cpl.to_bytes(2, 'big') + part_head + part_cnt + apdu + otak.auth.check_sig(temp_data, cc) + elif spi['rc_cc_ds'] == 'rc': + # CRC32 + crc32_rx = int.from_bytes(envelope_data[:4], 'big') + # FIXME: crc32_computed = zlip.crc32( + # FIXME: verify RC + raise NotImplementedError + apdu = envelope_data[4:] + elif spi['rc_cc_ds'] == 'no_rc_cc_ds': + apdu = envelope_data + else: + raise ValueError("Invalid rc_cc_ds: %s" % spi['rc_cc_ds']) + + apdu = apdu[:len(apdu)-pad_cnt] + return hdr_dec['tar'], spi, apdu + + def decode_resp(self, otak: OtaKeyset, spi: dict, data: bytes) -> ("OtaDialectSms.SmsResponsePacket", Optional["CompactRemoteResp"]): if isinstance(data, str): data = h2b(data) diff --git a/tests/test_ota.py b/tests/test_ota.py index ce10a7d..c4598a3 100644 --- a/tests/test_ota.py +++ b/tests/test_ota.py @@ -65,14 +65,19 @@
def test_cmd_aes128_ciphered(self): spi = self.spi_base - r = self.dialect.encode_cmd(self.od, self.tar, spi, h2b('00a40004023f00')) + apdu = h2b('00a40004023f00') + r = self.dialect.encode_cmd(self.od, self.tar, spi, apdu) self.assertEqual(b2h(r), '00281506192222b00011e87cceebb2d93083011ce294f93fc4d8de80da1abae8c37ca3e72ec4432e5058') - - + # also test decoder + dec_tar, dec_spi, dec_apdu = self.dialect.decode_cmd(self.od, r) + self.assertEqual(b2h(apdu), b2h(dec_apdu)) + self.assertEqual(b2h(dec_tar), b2h(self.tar)) + self.assertEqual(dec_spi, spi)
class Test_SMS_3DES(unittest.TestCase): tar = h2b('b00000') + apdu = h2b('00a40000023f00') """Test the OtaDialectSms for 3DES algorithms.""" def __init__(self, foo, **kwargs): super().__init__(foo, **kwargs) @@ -134,21 +139,26 @@ spi = self.spi_base spi['ciphering'] = True spi['rc_cc_ds'] = 'no_rc_cc_ds' - r = self.dialect.encode_cmd(self.od, self.tar, spi, h2b('00a40000023f00')) + r = self.dialect.encode_cmd(self.od, self.tar, spi, self.apdu) self.assertEqual(b2h(r), '00180d04193535b00000e3ec80a849b554421276af3883927c20') + # also test decoder + dec_tar, dec_spi, dec_apdu = self.dialect.decode_cmd(self.od, r) + self.assertEqual(b2h(self.apdu), b2h(dec_apdu)) + self.assertEqual(b2h(dec_tar), b2h(self.tar)) + self.assertEqual(dec_spi, spi)
def test_cmd_3des_signed(self): spi = self.spi_base spi['ciphering'] = False spi['rc_cc_ds'] = 'cc' - r = self.dialect.encode_cmd(self.od, self.tar, spi, h2b('00a40000023f00')) + r = self.dialect.encode_cmd(self.od, self.tar, spi, self.apdu) self.assertEqual(b2h(r), '1502193535b00000000000000000072ea17bdb72060e00a40000023f00')
def test_cmd_3des_none(self): spi = self.spi_base spi['ciphering'] = False spi['rc_cc_ds'] = 'no_rc_cc_ds' - r = self.dialect.encode_cmd(self.od, self.tar, spi, h2b('00a40000023f00')) + r = self.dialect.encode_cmd(self.od, self.tar, spi, self.apdu) self.assertEqual(b2h(r), '0d00193535b0000000000000000000a40000023f00')
@@ -273,6 +283,12 @@ #print("tpdu: %s" % b2h(tpdu.to_bytes())) self.assertEqual(b2h(tpdu.to_bytes()), t['request']['encoded_tpdu'])
+ # also test decoder + dec_tar, dec_spi, dec_apdu = self.dialect.decode_cmd(kset, outp) + self.assertEqual(b2h(t['request']['apdu']), b2h(dec_apdu)) + self.assertEqual(b2h(dec_tar), b2h(self.tar)) + self.assertEqual(dec_spi, t['spi']) + def test_decode_resp(self): for t in SmsOtaTestCase.testdatasets: with self.subTest(name=t['name']):
-
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