Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/pyasn1/codec/cer/decoder.py: 66%

1# 

2# This file is part of pyasn1 software. 

3# 

4# Copyright (c) 2005-2019, Ilya Etingof <etingof@gmail.com> 

5# License: http://snmplabs.com/pyasn1/license.html 

6# 

7from pyasn1 import error 

8from pyasn1.codec.ber import decoder 

9from pyasn1.compat.octets import oct2int 

10from pyasn1.type import univ 

11 

12__all__ = ['decode'] 

13 

14 

15class BooleanDecoder(decoder.AbstractSimpleDecoder): 

16 protoComponent = univ.Boolean(0) 

17 

18 def valueDecoder(self, substrate, asn1Spec, 

19 tagSet=None, length=None, state=None, 

20 decodeFun=None, substrateFun=None, 

21 **options): 

22 head, tail = substrate[:length], substrate[length:] 

23 if not head or length != 1: 

24 raise error.PyAsn1Error('Not single-octet Boolean payload') 

25 byte = oct2int(head[0]) 

26 # CER/DER specifies encoding of TRUE as 0xFF and FALSE as 0x0, while 

27 # BER allows any non-zero value as TRUE; cf. sections 8.2.2. and 11.1  

28 # in https://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf 

29 if byte == 0xff: 

30 value = 1 

31 elif byte == 0x00: 

32 value = 0 

33 else: 

34 raise error.PyAsn1Error('Unexpected Boolean payload: %s' % byte) 

35 return self._createComponent(asn1Spec, tagSet, value, **options), tail 

36 

37# TODO: prohibit non-canonical encoding 

38BitStringDecoder = decoder.BitStringDecoder 

39OctetStringDecoder = decoder.OctetStringDecoder 

40RealDecoder = decoder.RealDecoder 

41 

42tagMap = decoder.tagMap.copy() 

43tagMap.update( 

44 {univ.Boolean.tagSet: BooleanDecoder(), 

45 univ.BitString.tagSet: BitStringDecoder(), 

46 univ.OctetString.tagSet: OctetStringDecoder(), 

47 univ.Real.tagSet: RealDecoder()} 

48) 

49 

50typeMap = decoder.typeMap.copy() 

51 

52# Put in non-ambiguous types for faster codec lookup 

53for typeDecoder in tagMap.values(): 

54 if typeDecoder.protoComponent is not None: 

55 typeId = typeDecoder.protoComponent.__class__.typeId 

56 if typeId is not None and typeId not in typeMap: 

57 typeMap[typeId] = typeDecoder 

58 

59 

60class Decoder(decoder.Decoder): 

61 pass 

62 

63 

64#: Turns CER octet stream into an ASN.1 object. 

65#: 

66#: Takes CER octet-stream and decode it into an ASN.1 object 

67#: (e.g. :py:class:`~pyasn1.type.base.PyAsn1Item` derivative) which 

68#: may be a scalar or an arbitrary nested structure. 

69#: 

70#: Parameters 

71#: ---------- 

72#: substrate: :py:class:`bytes` (Python 3) or :py:class:`str` (Python 2) 

73#: CER octet-stream 

74#: 

75#: Keyword Args 

76#: ------------ 

77#: asn1Spec: any pyasn1 type object e.g. :py:class:`~pyasn1.type.base.PyAsn1Item` derivative 

78#: A pyasn1 type object to act as a template guiding the decoder. Depending on the ASN.1 structure 

79#: being decoded, *asn1Spec* may or may not be required. Most common reason for 

80#: it to require is that ASN.1 structure is encoded in *IMPLICIT* tagging mode. 

81#: 

82#: Returns 

83#: ------- 

84#: : :py:class:`tuple` 

85#: A tuple of pyasn1 object recovered from CER substrate (:py:class:`~pyasn1.type.base.PyAsn1Item` derivative) 

86#: and the unprocessed trailing portion of the *substrate* (may be empty) 

87#: 

88#: Raises 

89#: ------ 

90#: ~pyasn1.error.PyAsn1Error, ~pyasn1.error.SubstrateUnderrunError 

91#: On decoding errors 

92#: 

93#: Examples 

94#: -------- 

95#: Decode CER serialisation without ASN.1 schema 

96#: 

97#: .. code-block:: pycon 

98#: 

99#: >>> s, _ = decode(b'0\x80\x02\x01\x01\x02\x01\x02\x02\x01\x03\x00\x00') 

100#: >>> str(s) 

101#: SequenceOf: 

102#: 1 2 3 

103#: 

104#: Decode CER serialisation with ASN.1 schema 

105#: 

106#: .. code-block:: pycon 

107#: 

108#: >>> seq = SequenceOf(componentType=Integer()) 

109#: >>> s, _ = decode(b'0\x80\x02\x01\x01\x02\x01\x02\x02\x01\x03\x00\x00', asn1Spec=seq) 

110#: >>> str(s) 

111#: SequenceOf: 

112#: 1 2 3 

113#: 

114decode = Decoder(tagMap, decoder.typeMap)