95 lines
2.7 KiB
Python
95 lines
2.7 KiB
Python
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#
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# This file is part of pyasn1 software.
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#
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# Copyright (c) 2005-2019, Ilya Etingof <etingof@gmail.com>
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# License: http://snmplabs.com/pyasn1/license.html
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#
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from pyasn1.codec.cer import decoder
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from pyasn1.type import univ
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__all__ = ['decode']
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class BitStringDecoder(decoder.BitStringDecoder):
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supportConstructedForm = False
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class OctetStringDecoder(decoder.OctetStringDecoder):
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supportConstructedForm = False
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# TODO: prohibit non-canonical encoding
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RealDecoder = decoder.RealDecoder
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tagMap = decoder.tagMap.copy()
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tagMap.update(
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{univ.BitString.tagSet: BitStringDecoder(),
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univ.OctetString.tagSet: OctetStringDecoder(),
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univ.Real.tagSet: RealDecoder()}
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)
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typeMap = decoder.typeMap.copy()
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# Put in non-ambiguous types for faster codec lookup
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for typeDecoder in tagMap.values():
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if typeDecoder.protoComponent is not None:
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typeId = typeDecoder.protoComponent.__class__.typeId
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if typeId is not None and typeId not in typeMap:
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typeMap[typeId] = typeDecoder
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class Decoder(decoder.Decoder):
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supportIndefLength = False
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#: Turns DER octet stream into an ASN.1 object.
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#:
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#: Takes DER octet-stream and decode it into an ASN.1 object
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#: (e.g. :py:class:`~pyasn1.type.base.PyAsn1Item` derivative) which
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#: may be a scalar or an arbitrary nested structure.
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#:
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#: Parameters
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#: ----------
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#: substrate: :py:class:`bytes` (Python 3) or :py:class:`str` (Python 2)
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#: DER octet-stream
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#:
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#: Keyword Args
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#: ------------
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#: asn1Spec: any pyasn1 type object e.g. :py:class:`~pyasn1.type.base.PyAsn1Item` derivative
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#: A pyasn1 type object to act as a template guiding the decoder. Depending on the ASN.1 structure
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#: being decoded, *asn1Spec* may or may not be required. Most common reason for
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#: it to require is that ASN.1 structure is encoded in *IMPLICIT* tagging mode.
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#:
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#: Returns
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#: -------
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#: : :py:class:`tuple`
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#: A tuple of pyasn1 object recovered from DER substrate (:py:class:`~pyasn1.type.base.PyAsn1Item` derivative)
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#: and the unprocessed trailing portion of the *substrate* (may be empty)
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#:
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#: Raises
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#: ------
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#: ~pyasn1.error.PyAsn1Error, ~pyasn1.error.SubstrateUnderrunError
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#: On decoding errors
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#:
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#: Examples
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#: --------
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#: Decode DER serialisation without ASN.1 schema
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#:
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#: .. code-block:: pycon
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#:
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#: >>> s, _ = decode(b'0\t\x02\x01\x01\x02\x01\x02\x02\x01\x03')
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#: >>> str(s)
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#: SequenceOf:
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#: 1 2 3
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#:
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#: Decode DER serialisation with ASN.1 schema
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#:
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#: .. code-block:: pycon
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#:
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#: >>> seq = SequenceOf(componentType=Integer())
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#: >>> s, _ = decode(b'0\t\x02\x01\x01\x02\x01\x02\x02\x01\x03', asn1Spec=seq)
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#: >>> str(s)
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#: SequenceOf:
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#: 1 2 3
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#:
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decode = Decoder(tagMap, typeMap)
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