laforge has uploaded this change for review. ( https://gerrit.osmocom.org/c/pysim/+/36009?usp=email )

Change subject: utils: Add function to verify Luhn check digits and to sanitize ICCIDs ......................................................................

utils: Add function to verify Luhn check digits and to sanitize ICCIDs

Change-Id: I7812420cf97984dd834fca6a38c5e5ae113243cb --- M pySim/utils.py M tests/test_utils.py 2 files changed, 56 insertions(+), 1 deletion(-)

git pull ssh://gerrit.osmocom.org:29418/pysim refs/changes/09/36009/1

diff --git a/pySim/utils.py b/pySim/utils.py index 86874ba..afa476b 100644 --- a/pySim/utils.py +++ b/pySim/utils.py @@ -9,7 +9,7 @@ import datetime import argparse from io import BytesIO -from typing import Optional, List, Dict, Any, Tuple, NewType +from typing import Optional, List, Dict, Any, Tuple, NewType, Union

# Copyright (C) 2009-2010 Sylvain Munaut tnt@246tNt.com # Copyright (C) 2021 Harald Welte laforge@osmocom.org @@ -446,6 +446,30 @@ def enc_iccid(iccid: str) -> Hexstr: return swap_nibbles(rpad(iccid, 20))

+def sanitize_iccid(iccid: Union[int, str]) -> str: + iccid = str(iccid) + if len(iccid) < 18: + raise ValueError('ICCID input value must be at least 18 digits') + if len(iccid) > 20: + raise ValueError('ICCID input value must be at most 20 digits') + if len(iccid) == 18: + # 18 digits means we must add a luhn check digit to reach 19 digits + iccid += str(calculate_luhn(iccid)) + if len(iccid) == 20: + # 20 digits means we're actually exceeding E.118 by one digit, and + # the luhn check digit must already be included + verify_luhn(iccid) + if len(iccid) == 19: + # 19 digits means that it's either an in-spec 19-digits ICCID with + # its luhn check digit already present, or it's an out-of-spec 20-digit + # ICCID without that check digit... + try: + verify_luhn(iccid) + except ValueError: + # 19th digit was not luhn check digit; we must add it + iccid += str(calculate_luhn(iccid)) + return iccid +

def enc_plmn(mcc: Hexstr, mnc: Hexstr) -> Hexstr: """Converts integer MCC/MNC into 3 bytes for EF""" @@ -606,6 +630,11 @@ for d in num[::-2]]) % 10 return 0 if check_digit == 10 else check_digit

+def verify_luhn(digits: str): + """Verify the Luhn check digit; raises ValueError if it is incorrect.""" + cd = calculate_luhn(digits[:-1]) + if str(cd) != digits[-1]: + raise ValueError('Luhn check digit mismatch: should be %s but is %s' % (str(cd), digits[-1]))

def mcc_from_imsi(imsi: str) -> Optional[str]: """ diff --git a/tests/test_utils.py b/tests/test_utils.py index 7609f80..75c8566 100755 --- a/tests/test_utils.py +++ b/tests/test_utils.py @@ -236,5 +236,22 @@ self.assertEqual(utils.dgi_parse_len(b'\xfe\x0b'), (254, b'\x0b')) self.assertEqual(utils.dgi_parse_len(b'\xff\x00\xff\x0b'), (255, b'\x0b'))

+class TestLuhn(unittest.TestCase): + def test_verify(self): + utils.verify_luhn('8988211000000530082') + + def test_encode(self): + self.assertEqual(utils.calculate_luhn('898821100000053008'), 2) + + def test_sanitize_iccid(self): + # 19 digits with correct luhn; we expect no change + self.assertEqual(utils.sanitize_iccid('8988211000000530082'), '8988211000000530082') + # 20 digits with correct luhn; we expect no change + self.assertEqual(utils.sanitize_iccid('89882110000005300811'), '89882110000005300811') + # 19 digits without correct luhn; we expect chck digit to be added + self.assertEqual(utils.sanitize_iccid('8988211000000530081'), '89882110000005300811') + # 18 digits; we expect luhn check digit to be added + self.assertEqual(utils.sanitize_iccid('898821100000053008'), '8988211000000530082') + if __name__ == "__main__": unittest.main()