Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/pyasn1/codec/der/decoder.py: 95%

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.codec.cer import decoder 

8from pyasn1.type import univ 

9 

10__all__ = ['decode'] 

11 

12 

13class BitStringDecoder(decoder.BitStringDecoder): 

14 supportConstructedForm = False 

15 

16 

17class OctetStringDecoder(decoder.OctetStringDecoder): 

18 supportConstructedForm = False 

19 

20# TODO: prohibit non-canonical encoding 

21RealDecoder = decoder.RealDecoder 

22 

23tagMap = decoder.tagMap.copy() 

24tagMap.update( 

25 {univ.BitString.tagSet: BitStringDecoder(), 

26 univ.OctetString.tagSet: OctetStringDecoder(), 

27 univ.Real.tagSet: RealDecoder()} 

28) 

29 

30typeMap = decoder.typeMap.copy() 

31 

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

33for typeDecoder in tagMap.values(): 

34 if typeDecoder.protoComponent is not None: 

35 typeId = typeDecoder.protoComponent.__class__.typeId 

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

37 typeMap[typeId] = typeDecoder 

38 

39 

40class Decoder(decoder.Decoder): 

41 supportIndefLength = False 

42 

43 

44#: Turns DER octet stream into an ASN.1 object. 

45#: 

46#: Takes DER octet-stream and decode it into an ASN.1 object 

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

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

49#: 

50#: Parameters 

51#: ---------- 

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

53#: DER octet-stream 

54#: 

55#: Keyword Args 

56#: ------------ 

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

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

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

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

61#: 

62#: Returns 

63#: ------- 

64#: : :py:class:`tuple` 

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

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

67#: 

68#: Raises 

69#: ------ 

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

71#: On decoding errors 

72#: 

73#: Examples 

74#: -------- 

75#: Decode DER serialisation without ASN.1 schema 

76#: 

77#: .. code-block:: pycon 

78#: 

79#: >>> s, _ = decode(b'0\t\x02\x01\x01\x02\x01\x02\x02\x01\x03') 

80#: >>> str(s) 

81#: SequenceOf: 

82#: 1 2 3 

83#: 

84#: Decode DER serialisation with ASN.1 schema 

85#: 

86#: .. code-block:: pycon 

87#: 

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

89#: >>> s, _ = decode(b'0\t\x02\x01\x01\x02\x01\x02\x02\x01\x03', asn1Spec=seq) 

90#: >>> str(s) 

91#: SequenceOf: 

92#: 1 2 3 

93#: 

94decode = Decoder(tagMap, typeMap)