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0001-Fix-IMSIs-which-are-shorter-than-15-characters.patch

ben.foxmoore, 09/13/2018 12:52 PM

View differences:

pySim/utils.py
49 49
def lpad(s, l, c='f'):
50 50
	return c * (l - len(s)) + s
51 51

  
52
def half_round_up(n):
53
	return (n + 1)//2
54

  
55
# IMSI encoded format:
56
# For IMSI 0123456789ABCDE:
57
#
58
# |     byte 1      | 2 upper | 2 lower  | 3 upper | 3 lower | ... | 9 upper | 9 lower |
59
# | length in bytes |    0    | odd/even |    2    |    1    | ... |    E    |    D    |
60
#
61
# If the IMSI is less than 15 characters, it should be padded with 'f' from the end.
62
#
63
# The length is the total number of bytes used to encoded the IMSI. This includes the odd/even
64
# parity bit. E.g. an IMSI of length 14 is 8 bytes long, not 7, as it uses bytes 2 to 9 to
65
# encode itself.
66
#
67
# Because of this, an odd length IMSI fits exactly into len(imsi) + 1 // 2 bytes, whereas an
68
# even length IMSI only uses half of the last byte.
69

  
52 70
def enc_imsi(imsi):
53 71
	"""Converts a string imsi into the value of the EF"""
54
	l = (len(imsi) + 1) // 2	# Required bytes
72
	l = half_round_up(len(imsi) + 1)	# Required bytes - include space for odd/even indicator
55 73
	oe = len(imsi) & 1			# Odd (1) / Even (0)
56
	ei = '%02x' % l + swap_nibbles(lpad('%01x%s' % ((oe<<3)|1, imsi), 16))
74
	ei = '%02x' % l + swap_nibbles('%01x%s' % ((oe<<3)|1, rpad(imsi, 15)))
57 75
	return ei
58 76

  
59 77
def dec_imsi(ef):
......
61 79
	if len(ef) < 4:
62 80
		return None
63 81
	l = int(ef[0:2], 16) * 2		# Length of the IMSI string
64
	swapped = swap_nibbles(ef[2:])
82
	l = l - 1						# Encoded length byte includes oe nibble
83
	swapped = swap_nibbles(ef[2:]).rstrip('f')
65 84
	oe = (int(swapped[0])>>3) & 1	# Odd (1) / Even (0)
66
	if oe:
85
	if not oe:
86
		# if even, only half of last byte was used
67 87
		l = l-1
68
	if l+1 > len(swapped):
88
	if l != len(swapped) - 1:
69 89
		return None
70
	imsi = swapped[1:l+2]
90
	imsi = swapped[1:]
71 91
	return imsi
72 92

  
73 93
def dec_iccid(ef):
74
- 
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