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31.102: Fix EF.Routing_Indicator for odd number of digits

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The routing indicator is BCD-encoded but has an arbitrary length of
1, 2, 3 or 4 digits.

In order to support the odd lengths of 1 or 3, we must not pad on the
byte level, but on the nibble level. This requires a slight extension of
the Rpad() Adapter.

Change-Id: I6c26dccdd570de7b7a4cd48338068e230340ec7c
Fixes: OS#6054
This commit is contained in:
Harald Welte
2023-06-09 09:17:05 +02:00
parent 1dce498a67
commit f9a5ba5e0f
2 changed files with 11 additions and 7 deletions
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15
pySim/construct.py
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@@ -66,26 +66,29 @@ class InvertAdapter(Adapter):
class Rpad(Adapter): class Rpad(Adapter):
""" """
Encoder appends padding bytes (b'\\xff') up to target size. Encoder appends padding bytes (b'\\xff') or characters up to target size.
Decoder removes trailing padding bytes. Decoder removes trailing padding bytes/characters.
Parameters: Parameters:
subcon: Subconstruct as defined by construct library subcon: Subconstruct as defined by construct library
pattern: set padding pattern (default: b'\\xff') pattern: set padding pattern (default: b'\\xff')
num_per_byte: number of 'elements' per byte. E.g. for hex nibbles: 2
""" """
def __init__(self, subcon, pattern=b'\xff'): def __init__(self, subcon, pattern=b'\xff', num_per_byte=1):
super().__init__(subcon) super().__init__(subcon)
self.pattern = pattern self.pattern = pattern
self.num_per_byte = num_per_byte
def _decode(self, obj, context, path): def _decode(self, obj, context, path):
return obj.rstrip(self.pattern) return obj.rstrip(self.pattern)
def _encode(self, obj, context, path): def _encode(self, obj, context, path):
if len(obj) > self.sizeof(): target_size = self.sizeof() * self.num_per_byte
if len(obj) > target_size:
raise SizeofError("Input ({}) exceeds target size ({})".format( raise SizeofError("Input ({}) exceeds target size ({})".format(
len(obj), self.sizeof())) len(obj), target_size))
return obj + self.pattern * (self.sizeof() - len(obj)) return obj + self.pattern * (target_size - len(obj))
class MultiplyAdapter(Adapter): class MultiplyAdapter(Adapter):
""" """

3
pySim/ts_31_102.py
View File

@@ -1089,7 +1089,8 @@ class EF_Routing_Indicator(TransparentEF):
# responsibility of home network operator but BCD coding shall be used. If a network # responsibility of home network operator but BCD coding shall be used. If a network
# operator decides to assign less than 4 digits to Routing Indicator, the remaining digits # operator decides to assign less than 4 digits to Routing Indicator, the remaining digits
# shall be coded as "1111" to fill the 4 digits coding of Routing Indicator # shall be coded as "1111" to fill the 4 digits coding of Routing Indicator
self._construct = Struct('routing_indicator'/BcdAdapter(Rpad(Bytes(2))), 'rfu'/HexAdapter(Bytes(2))) self._construct = Struct('routing_indicator'/Rpad(BcdAdapter(Bytes(2)), 'f', 2),
'rfu'/HexAdapter(Bytes(2)))
# TS 31.102 Section 4.4.11.13 # TS 31.102 Section 4.4.11.13
class EF_TN3GPPSNN(TransparentEF): class EF_TN3GPPSNN(TransparentEF):