net/tools/testserver/asn1.py

   1 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 # Use of this source code is governed by a BSD-style license that can be
   3 # found in the LICENSE file.
   4
   5 # This file implements very minimal ASN.1, DER serialization.
   6
   7 import types
   8
   9
  10 def ToDER(obj):
  11   '''ToDER converts the given object into DER encoding'''
  12   if type(obj) == types.NoneType:
  13     # None turns into NULL
  14     return TagAndLength(5, 0)
  15   if type(obj) == types.StringType:
  16     # Strings are PRINTABLESTRING
  17     return TagAndLength(19, len(obj)) + obj
  18   if type(obj) == types.BooleanType:
  19     val = "\x00"
  20     if obj:
  21       val = "\xff"
  22     return TagAndLength(1, 1) + val
  23   if type(obj) == types.IntType or type(obj) == types.LongType:
  24     big_endian = []
  25     val = obj
  26     while val != 0:
  27       big_endian.append(val & 0xff)
  28       val >>= 8
  29
  30     if len(big_endian) == 0 or big_endian[-1] >= 128:
  31       big_endian.append(0)
  32
  33     big_endian.reverse()
  34     return TagAndLength(2, len(big_endian)) + ToBytes(big_endian)
  35
  36   return obj.ToDER()
  37
  38
  39 def ToBytes(array_of_bytes):
  40   '''ToBytes converts the array of byte values into a binary string'''
  41   return ''.join([chr(x) for x in array_of_bytes])
  42
  43
  44 def TagAndLength(tag, length):
  45   der = [tag]
  46   if length < 128:
  47     der.append(length)
  48   elif length < 256:
  49     der.append(0x81)
  50     der.append(length)
  51   elif length < 65535:
  52     der.append(0x82)
  53     der.append(length >> 8)
  54     der.append(length & 0xff)
  55   else:
  56     assert False
  57
  58   return ToBytes(der)
  59
  60
  61 class Raw(object):
  62   '''Raw contains raw DER encoded bytes that are used verbatim'''
  63   def __init__(self, der):
  64     self.der = der
  65
  66   def ToDER(self):
  67     return self.der
  68
  69
  70 class Explicit(object):
  71   '''Explicit prepends an explicit tag'''
  72   def __init__(self, tag, child):
  73     self.tag = tag
  74     self.child = child
  75
  76   def ToDER(self):
  77     der = ToDER(self.child)
  78     tag = self.tag
  79     tag |= 0x80 # content specific
  80     tag |= 0x20 # complex
  81     return TagAndLength(tag, len(der)) + der
  82
  83
  84 class ENUMERATED(object):
  85   def __init__(self, value):
  86     self.value = value
  87
  88   def ToDER(self):
  89     return TagAndLength(10, 1) + chr(self.value)
  90
  91
  92 class SEQUENCE(object):
  93   def __init__(self, children):
  94     self.children = children
  95
  96   def ToDER(self):
  97     der = ''.join([ToDER(x) for x in self.children])
  98     return TagAndLength(0x30, len(der)) + der
  99
 100
 101 class SET(object):
 102   def __init__(self, children):
 103     self.children = children
 104
 105   def ToDER(self):
 106     der = ''.join([ToDER(x) for x in self.children])
 107     return TagAndLength(0x31, len(der)) + der
 108
 109
 110 class OCTETSTRING(object):
 111   def __init__(self, val):
 112     self.val = val
 113
 114   def ToDER(self):
 115     return TagAndLength(4, len(self.val)) + self.val
 116
 117
 118 class OID(object):
 119   def __init__(self, parts):
 120     self.parts = parts
 121
 122   def ToDER(self):
 123     if len(self.parts) < 2 or self.parts[0] > 6 or self.parts[1] >= 40:
 124       assert False
 125
 126     der = [self.parts[0]*40 + self.parts[1]]
 127     for x in self.parts[2:]:
 128       if x == 0:
 129         der.append(0)
 130       else:
 131         octets = []
 132         while x != 0:
 133           v = x & 0x7f
 134           if len(octets) > 0:
 135             v |= 0x80
 136           octets.append(v)
 137           x >>= 7
 138         octets.reverse()
 139         der = der + octets
 140
 141     return TagAndLength(6, len(der)) + ToBytes(der)
 142
 143
 144 class UTCTime(object):
 145   def __init__(self, time_str):
 146     self.time_str = time_str
 147
 148   def ToDER(self):
 149     return TagAndLength(23, len(self.time_str)) + self.time_str
 150
 151
 152 class GeneralizedTime(object):
 153   def __init__(self, time_str):
 154     self.time_str = time_str
 155
 156   def ToDER(self):
 157     return TagAndLength(24, len(self.time_str)) + self.time_str
 158
 159
 160 class BitString(object):
 161   def __init__(self, bits):
 162     self.bits = bits
 163
 164   def ToDER(self):
 165     return TagAndLength(3, 1 + len(self.bits)) + "\x00" + self.bits