commands: get file/record length from FCP (USIM)

Some of the methods SimCardCommands() have ways to determaine length
information from the card response. Regular sims use a format where
the length field is on a fixed position. USIMs use FCP templates
(format control parameters), which is a TLV encodecs string. So lets
distingish if we deal with an USIM (We can easily do this by looking
at the select control parameters) and extract the length info from
the FCP.

- If we deal with USIMs, use the FCP to determine length
  information

Change-Id: I068cf8a532e1c79a2d208e9d275c155ddb72713c
Related: SYS#4245

1 files changed, 56 insertions, 6 deletions

diff --git a/pySim/commands.py b/pySim/commands.py
index eba915c..9e16b0e 100644
--- a/pySim/commands.py
+++ b/pySim/commands.py
@@ -23,7 +23,7 @@
 #
 
 from pySim.utils import rpad, b2h
-
+from pytlv.TLV import *
 
 class SimCardCommands(object):
 	def __init__(self, transport):
@@ -31,6 +31,56 @@ class SimCardCommands(object):
 		self._cla_byte = "a0"
 		self.sel_ctrl = "0000"
 
+	# Get file size from FCP
+	def __get_len_from_tlv(self, fcp):
+		# see also: ETSI TS 102 221, chapter 11.1.1.3.1 Response for MF,
+		# DF or ADF
+		tlvparser = TLV(['82', '83', '84', 'A5', '8a', '8b', '8c', '80', 'ab', 'c6', '81', '88'])
+
+		# pytlv is case sensitive!
+		fcp = fcp.lower()
+
+		if fcp[0:2] != '62':
+			raise ValueError('Tag of the FCP template does not match, expected 62 but got %s'%fcp[0:2])
+
+		# Unfortunately the spec is not very clear if the FCP length is
+		# coded as one or two byte vale, so we have to try it out by
+		# checking if the length of the remaining TLV string matches
+		# what we get in the length field.
+		# See also ETSI TS 102 221, chapter 11.1.1.3.0 Base coding.
+		exp_tlv_len = int(fcp[2:4], 16)
+		if len(fcp[4:])/2 == exp_tlv_len:
+			skip = 4
+		else:
+			exp_tlv_len = int(fcp[2:6], 16)
+			if len(fcp[4:])/2 == exp_tlv_len:
+				skip = 6
+
+		# Skip FCP tag and length
+		tlv = fcp[skip:]
+		tlv_parsed = tlvparser.parse(tlv)
+
+		return int(tlv_parsed['80'], 16)
+
+        # Tell the length of a record by the card response
+        # USIMs respond with an FCP template, which is different
+        # from what SIMs responds. See also:
+        # USIM: ETSI TS 102 221, chapter 11.1.1.3 Response Data
+        # SIM: GSM 11.11, chapter 9.2.1 SELECT
+	def __record_len(self, r):
+                if self.sel_ctrl == "0004":
+                        return self.__get_len_from_tlv(r[-1])
+                else:
+                        return int(r[-1][28:30], 16)
+
+        # Tell the length of a binary file. See also comment
+        # above.
+	def __len(self, r):
+                if self.sel_ctrl == "0004":
+                        return self.__get_len_from_tlv(r[-1])
+                else:
+                        return int(r[-1][4:8], 16)
+
 	def get_atr(self):
 		return self._tp.get_atr()
 
@@ -60,7 +110,7 @@ class SimCardCommands(object):
 			ef = [ef]
 		r = self.select_file(ef)
 		if length is None:
-			length = int(r[-1][4:8], 16) - offset
+			length = self.__len(r) - offset
 		pdu = self.cla_byte + 'b0%04x%02x' % (offset, (min(256, length) & 0xff))
 		return self._tp.send_apdu(pdu)
 
@@ -75,7 +125,7 @@ class SimCardCommands(object):
 		if not hasattr(type(ef), '__iter__'):
 			ef = [ef]
 		r = self.select_file(ef)
-		rec_length = int(r[-1][28:30], 16)
+		rec_length = self.__record_len(r)
 		pdu = self.cla_byte + 'b2%02x04%02x' % (rec_no, rec_length)
 		return self._tp.send_apdu(pdu)
 
@@ -84,7 +134,7 @@ class SimCardCommands(object):
 			ef = [ef]
 		r = self.select_file(ef)
 		if not force_len:
-			rec_length = int(r[-1][28:30], 16)
+			rec_length = self.__record_len(r)
 			if (len(data)/2 != rec_length):
 				raise ValueError('Invalid data length (expected %d, got %d)' % (rec_length, len(data)/2))
 		else:
@@ -94,11 +144,11 @@ class SimCardCommands(object):
 
 	def record_size(self, ef):
 		r = self.select_file(ef)
-		return int(r[-1][28:30], 16)
+		return self.__record_len(r)
 
 	def record_count(self, ef):
 		r = self.select_file(ef)
-		return int(r[-1][4:8], 16) // int(r[-1][28:30], 16)
+		return self.__len(r) // self.__record_len(r)
 
 	def run_gsm(self, rand):
 		if len(rand) != 32: