def _encode_octet(obj: univ.OctetString) -> str:
""" Encodes a STRING OCTET type
Args:
obj: A PyASN1 STRING_OCTET type
Returns:
A string containing the encoded binary
"""
dec_constraint = _extract_value_size_constraint(str(obj.getSubtypeSpec()))
oct_str = str(obj)
if dec_constraint == -1:
# No constraint
length = len(str(obj))
len_det = _bit_str_pad(bin(length)[2:], 8, '0')
return len_det + ''.join([_bit_str_pad(bin(ord(oct_str[x]))[2:], 8, '0')
for x in range(len(oct_str))])
if dec_constraint[1] == 0:
return None
elif dec_constraint[0] == dec_constraint[1]:
if len(obj) == dec_constraint[0]:
return ''.join([_bit_str_pad(bin(ord(oct_str[x]))[2:], 8, '0') for x in range(
len(oct_str))])
else:
raise ValueError('[PyASN1PEREncoder][ERROR]: Octet string does not fit the '
'constraints - cannot encode [len != const_len]')
elif len(oct_str) < dec_constraint[0] or len(oct_str) > dec_constraint[1]:
raise ValueError('[PyASN1PEREncoder][ERROR]: Octet string does not fit the '
'constraints - cannot encode ![lb < x < ub]')
else:
offset_bitfield_range = len(str(bin(dec_constraint[1]-dec_constraint[0])[2:]))
len_det = _bit_str_pad(bin(len(oct_str)-dec_constraint[0])[2:], offset_bitfield_range, '0')
return len_det + ''.join([_bit_str_pad(bin(ord(oct_str[x]))[2:], 8, '0')
for x in range(len(oct_str))])
def _decode_octet_string(item: univ.OctetString,
data: str) -> Tuple[int, base.Asn1Item]:
""" Decodes an ASN.1 PER Encoded octet-string object
Args:
item: The enumerated base object that defines the encoded data
data: The PER unaligned encoded binary string
Returns:
A tuple containing the PyASN.1 object populated with the decoded data and the
length of the data processed (used for error checking)
"""
dec_constraint = _extract_value_size_constraint(str(item.getSubtypeSpec()))
if dec_constraint == -1:
# No constraint
length = int(data[:8], 2)
decoded_str = ''
for i in range(0, length):
decoded_str += chr(int(data[(8 + i * 8):(16 + i * 8)], 2))
return 8 * (length + 1), item.clone(decoded_str)
elif dec_constraint[1] == 0:
return 0, item.clone()
elif dec_constraint[0] == dec_constraint[1]:
decoded_str = ''
for i in range(0, dec_constraint[0]):
decoded_str += chr(int(data[(8 + i * 8):(16 + i * 8)], 2))
return 8 * dec_constraint[0], item.clone(decoded_str)
else:
offset_bitfield_range = len(
str(bin(dec_constraint[1] - dec_constraint[0])[2:]))
length = int(data[:offset_bitfield_range], 2) + dec_constraint[0]
decoded_str = ''
for i in range(0, length):
decoded_str += chr(
int(
data[(offset_bitfield_range +
(i * 8)):((offset_bitfield_range + 8) + i * 8)], 2))
return offset_bitfield_range + (8 * length), item.clone(decoded_str)
def _decode_octet_string(item: univ.OctetString, data: str) -> Tuple[int, base.Asn1Item]:
""" Decodes an ASN.1 PER Encoded octet-string object
Args:
item: The enumerated base object that defines the encoded data
data: The PER unaligned encoded binary string
Returns:
A tuple containing the PyASN.1 object populated with the decoded data and the
length of the data processed (used for error checking)
"""
dec_constraint = _extract_value_size_constraint(str(item.getSubtypeSpec()))
if dec_constraint == -1:
# No constraint
length = int(data[:8], 2)
decoded_str = ''
for i in range(0, length):
decoded_str += chr(int(data[(8+i*8):(16+i*8)], 2))
return 8*(length+1), item.clone(decoded_str)
elif dec_constraint[1] == 0:
return 0, item.clone()
elif dec_constraint[0] == dec_constraint[1]:
decoded_str = ''
for i in range(0, dec_constraint[0]):
decoded_str += chr(int(data[(8+i*8):(16+i*8)], 2))
return 8*dec_constraint[0], item.clone(decoded_str)
else:
offset_bitfield_range = len(str(bin(dec_constraint[1]-dec_constraint[0])[2:]))
length = int(data[:offset_bitfield_range], 2) + dec_constraint[0]
decoded_str = ''
for i in range(0, length):
decoded_str += chr(int(data[(offset_bitfield_range+(i*8)):(
(offset_bitfield_range+8)+i*8)], 2))
return offset_bitfield_range+(8*length), item.clone(decoded_str)
