From 4b1c7633954697eda687fb122a73166446fa1f83 Mon Sep 17 00:00:00 2001
From: Supreeth Herle <herlesupreeth@gmail.com>
Date: Sun, 22 Dec 2019 09:00:59 +0100
Subject: [PATCH] pySim-read.py: fix reading and parsing of EF.MSISDN

This change implements parsing of EF.MSISDN (and thus EF.ADN)
as per 3GPP TS 31.102, sections 4.2.26 and 4.4.2.3.

Example (commercial SIM card from 401/02):

  EF.MSISDN: ffffffffffffffffffffffffffff07917787028982f7ffffffffffff
  Decoded (NPI=1 ToN=1): +77782098287

Note that sysmoUSIM-SJS1 in the test setup has malformed
EF.MSISDN, so that's why the test output is changed.

Change-Id: Ie914ae83d787e3f1a90f9f305bffd45053b8c863
---
 pySim-read.py                    |  8 ++++---
 pySim/utils.py                   | 41 ++++++++++++++++++++++++++++++++
 pysim-testdata/sysmoISIM-SJA2.ok |  2 +-
 pysim-testdata/sysmoUSIM-SJS1.ok |  2 +-
 4 files changed, 48 insertions(+), 5 deletions(-)

diff --git a/pySim-read.py b/pySim-read.py
index d753c8bf..ce5f8a59 100755
--- a/pySim-read.py
+++ b/pySim-read.py
@@ -37,7 +37,7 @@
 	import simplejson as json
 
 from pySim.commands import SimCardCommands
-from pySim.utils import h2b, swap_nibbles, rpad, dec_imsi, dec_iccid, format_xplmn_w_act, dec_spn
+from pySim.utils import h2b, swap_nibbles, rpad, dec_imsi, dec_iccid, dec_msisdn, format_xplmn_w_act, dec_spn
 
 
 def parse_options():
@@ -186,8 +186,10 @@ def parse_options():
 	#	print(scc.record_size(['3f00', '7f10', '6f40']))
 		(res, sw) = scc.read_record(['3f00', '7f10', '6f40'], 1)
 		if sw == '9000':
-			if res[1] != 'f':
-				print("MSISDN: %s" % (res,))
+			res_dec = dec_msisdn(res)
+			if res_dec is not None:
+				# (npi, ton, msisdn) = res_dec
+				print("MSISDN (NPI=%d ToN=%d): %s" % res_dec)
 			else:
 				print("MSISDN: Not available")
 		else:
diff --git a/pySim/utils.py b/pySim/utils.py
index af4a491f..12f66b94 100644
--- a/pySim/utils.py
+++ b/pySim/utils.py
@@ -258,3 +258,44 @@ def derive_mnc(digit1, digit2, digit3=0x0f):
 		mnc += digit2
 
 	return mnc
+
+def dec_msisdn(ef_msisdn):
+	"""
+	Decode MSISDN from EF.MSISDN or EF.ADN (same structure).
+	See 3GPP TS 31.102, section 4.2.26 and 4.4.2.3.
+	"""
+
+	# Convert from str to (kind of) 'bytes'
+	ef_msisdn = h2b(ef_msisdn)
+
+	# Make sure mandatory fields are present
+	if len(ef_msisdn) < 14:
+		raise ValueError("EF.MSISDN is too short")
+
+	# Skip optional Alpha Identifier
+	xlen = len(ef_msisdn) - 14
+	msisdn_lhv = ef_msisdn[xlen:]
+
+	# Parse the length (in bytes) of the BCD encoded number
+	bcd_len = ord(msisdn_lhv[0])
+	# BCD length = length of dial num (max. 10 bytes) + 1 byte ToN and NPI
+	if bcd_len == 0xff:
+		return None
+	elif bcd_len > 11 or bcd_len < 1:
+		raise ValueError("Length of MSISDN (%d bytes) is out of range" % bcd_len)
+
+	# Parse ToN / NPI
+	ton = (ord(msisdn_lhv[1]) >> 4) & 0x07
+	npi = ord(msisdn_lhv[1]) & 0x0f
+	bcd_len -= 1
+
+	# No MSISDN?
+	if not bcd_len:
+		return (npi, ton, None)
+
+	msisdn = swap_nibbles(b2h(msisdn_lhv[2:][:bcd_len])).rstrip('f')
+	# International number 10.5.118/3GPP TS 24.008
+	if (ton & 0x01) == 0x01:
+		msisdn = '+' + msisdn
+
+	return (npi, ton, msisdn)
diff --git a/pysim-testdata/sysmoISIM-SJA2.ok b/pysim-testdata/sysmoISIM-SJA2.ok
index a64aa8b6..bfef8822 100644
--- a/pysim-testdata/sysmoISIM-SJA2.ok
+++ b/pysim-testdata/sysmoISIM-SJA2.ok
@@ -50,7 +50,7 @@ HPLMNAcT:
 	ffffff0000 # unused
 
 ACC: 0001
-MSISDN: Not available
+MSISDN (NPI=1 ToN=1): +1234
 AD: 00000002
 Done !
 
diff --git a/pysim-testdata/sysmoUSIM-SJS1.ok b/pysim-testdata/sysmoUSIM-SJS1.ok
index 8def4e3a..6d85f38f 100644
--- a/pysim-testdata/sysmoUSIM-SJS1.ok
+++ b/pysim-testdata/sysmoUSIM-SJS1.ok
@@ -50,7 +50,7 @@ HPLMNAcT:
 	ffffff0000 # unused
 
 ACC: 0008
-MSISDN: Not available
+MSISDN: Can't read file -- Length of MSISDN (136 bytes) is out of range
 AD: 00000002
 Done !