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- #
- # This file is part of pyasn1 software.
- #
- # Copyright (c) 2005-2018, Ilya Etingof <etingof@gmail.com>
- # License: http://snmplabs.com/pyasn1/license.html
- #
- from pyasn1 import error
- from pyasn1.codec.ber import decoder
- from pyasn1.compat.octets import oct2int
- from pyasn1.type import univ
-
- __all__ = ['decode']
-
-
- class BooleanDecoder(decoder.AbstractSimpleDecoder):
- protoComponent = univ.Boolean(0)
-
- def valueDecoder(self, substrate, asn1Spec,
- tagSet=None, length=None, state=None,
- decodeFun=None, substrateFun=None,
- **options):
- head, tail = substrate[:length], substrate[length:]
- if not head or length != 1:
- raise error.PyAsn1Error('Not single-octet Boolean payload')
- byte = oct2int(head[0])
- # CER/DER specifies encoding of TRUE as 0xFF and FALSE as 0x0, while
- # BER allows any non-zero value as TRUE; cf. sections 8.2.2. and 11.1
- # in https://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf
- if byte == 0xff:
- value = 1
- elif byte == 0x00:
- value = 0
- else:
- raise error.PyAsn1Error('Unexpected Boolean payload: %s' % byte)
- return self._createComponent(asn1Spec, tagSet, value, **options), tail
-
- # TODO: prohibit non-canonical encoding
- BitStringDecoder = decoder.BitStringDecoder
- OctetStringDecoder = decoder.OctetStringDecoder
- RealDecoder = decoder.RealDecoder
-
- tagMap = decoder.tagMap.copy()
- tagMap.update(
- {univ.Boolean.tagSet: BooleanDecoder(),
- univ.BitString.tagSet: BitStringDecoder(),
- univ.OctetString.tagSet: OctetStringDecoder(),
- univ.Real.tagSet: RealDecoder()}
- )
-
- typeMap = decoder.typeMap.copy()
-
- # Put in non-ambiguous types for faster codec lookup
- for typeDecoder in tagMap.values():
- if typeDecoder.protoComponent is not None:
- typeId = typeDecoder.protoComponent.__class__.typeId
- if typeId is not None and typeId not in typeMap:
- typeMap[typeId] = typeDecoder
-
-
- class Decoder(decoder.Decoder):
- pass
-
-
- #: Turns CER octet stream into an ASN.1 object.
- #:
- #: Takes CER octet-stream and decode it into an ASN.1 object
- #: (e.g. :py:class:`~pyasn1.type.base.PyAsn1Item` derivative) which
- #: may be a scalar or an arbitrary nested structure.
- #:
- #: Parameters
- #: ----------
- #: substrate: :py:class:`bytes` (Python 3) or :py:class:`str` (Python 2)
- #: CER octet-stream
- #:
- #: Keyword Args
- #: ------------
- #: asn1Spec: any pyasn1 type object e.g. :py:class:`~pyasn1.type.base.PyAsn1Item` derivative
- #: A pyasn1 type object to act as a template guiding the decoder. Depending on the ASN.1 structure
- #: being decoded, *asn1Spec* may or may not be required. Most common reason for
- #: it to require is that ASN.1 structure is encoded in *IMPLICIT* tagging mode.
- #:
- #: Returns
- #: -------
- #: : :py:class:`tuple`
- #: A tuple of pyasn1 object recovered from CER substrate (:py:class:`~pyasn1.type.base.PyAsn1Item` derivative)
- #: and the unprocessed trailing portion of the *substrate* (may be empty)
- #:
- #: Raises
- #: ------
- #: :py:class:`~pyasn1.error.PyAsn1Error`
- #: On decoding errors
- #:
- #: Examples
- #: --------
- #: Decode CER serialisation without ASN.1 schema
- #:
- #: .. code-block:: pycon
- #:
- #: >>> s, _ = decode(b'0\x80\x02\x01\x01\x02\x01\x02\x02\x01\x03\x00\x00')
- #: >>> str(s)
- #: SequenceOf:
- #: 1 2 3
- #:
- #: Decode CER serialisation with ASN.1 schema
- #:
- #: .. code-block:: pycon
- #:
- #: >>> seq = SequenceOf(componentType=Integer())
- #: >>> s, _ = decode(b'0\x80\x02\x01\x01\x02\x01\x02\x02\x01\x03\x00\x00', asn1Spec=seq)
- #: >>> str(s)
- #: SequenceOf:
- #: 1 2 3
- #:
- decode = Decoder(tagMap, decoder.typeMap)
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