def _decode_len(substrate):
'''
Returns length of object and size of length string.
'''
first_byte = ord(substrate[0])
if first_byte == 128:
logger.error("Unexpected length of object, expecting definite length form")
return 0,0
if first_byte < 128:
return first_byte, 1
else:
size = first_byte & 0x7F
length_str = substrate[1:size+1]
length = bytes_to_int(length_str)
return length, size
def _parse_one_serial(substrate):
'''
Parses one integer at the beggining of sequence and date immediately after it.
Returns parsed serial number, date of revocation (UTC format, in string) and string starting at
the position of the next sequence with revoked certificate id.
'''
if substrate[0] == chr(0x30):
# ok, we are starting at sequence beginning
object_len, size_of_len_str = _decode_len(substrate[1:])
if (object_len == 0):
logger.error("Error parsing sequence object length")
content_offset = 1+size_of_len_str
# position of next sequence object start (other revoked certificate id)
next_start = content_offset + object_len
if substrate[content_offset] == chr(0x02):
# ok - integer id first - certificate serial number
int_len, size_of_len_str = _decode_len(substrate[content_offset+1:])
if (int_len == 0):
logger.error("Error parsing integer object length")
# position of start of serial number
absolute_start_of_int = content_offset + size_of_len_str + 1
# psoition of end of serial number
absolute_end_of_int = absolute_start_of_int + int_len
sn_bytes = substrate[absolute_start_of_int:absolute_end_of_int]
sn = bytes_to_int(sn_bytes)
# continue with date immediately after the integer (spec says, that revocationTime is mandatory)
date_start = absolute_end_of_int
date = _get_date(substrate[date_start:])
return sn, date, substrate[next_start:]
else:
logger.error("Integer header expected (byte 0x2)")
return -1,'', ''
else:
logger.error("Unexpected char: %x" % ord(substrate[0]))
# return empty string to stop the parsing process
return -1, '', ''