# # This file is part of pyasn1 software. # # Copyright (c) 2005-2018, Ilya Etingof # License: http://snmplabs.com/pyasn1/license.html # from pyasn1 import debug from pyasn1 import error from pyasn1.codec.ber import eoo from pyasn1.compat.integer import from_bytes from pyasn1.compat.octets import oct2int, octs2ints, ints2octs, null from pyasn1.type import base from pyasn1.type import char from pyasn1.type import tag from pyasn1.type import tagmap from pyasn1.type import univ from pyasn1.type import useful __all__ = ['decode'] noValue = base.noValue class AbstractDecoder(object): protoComponent = None def valueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): raise error.PyAsn1Error('Decoder not implemented for %s' % (tagSet,)) def indefLenValueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): raise error.PyAsn1Error('Indefinite length mode decoder not implemented for %s' % (tagSet,)) class AbstractSimpleDecoder(AbstractDecoder): @staticmethod def substrateCollector(asn1Object, substrate, length): return substrate[:length], substrate[length:] def _createComponent(self, asn1Spec, tagSet, value, **options): if options.get('native'): return value elif asn1Spec is None: return self.protoComponent.clone(value, tagSet=tagSet) elif value is noValue: return asn1Spec else: return asn1Spec.clone(value) class ExplicitTagDecoder(AbstractSimpleDecoder): protoComponent = univ.Any('') def valueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): if substrateFun: return substrateFun( self._createComponent(asn1Spec, tagSet, '', **options), substrate, length ) head, tail = substrate[:length], substrate[length:] value, _ = decodeFun(head, asn1Spec, tagSet, length, **options) return value, tail def indefLenValueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): if substrateFun: return substrateFun( self._createComponent(asn1Spec, tagSet, '', **options), substrate, length ) value, substrate = decodeFun(substrate, asn1Spec, tagSet, length, **options) eooMarker, substrate = decodeFun(substrate, allowEoo=True, **options) if eooMarker is eoo.endOfOctets: return value, substrate else: raise error.PyAsn1Error('Missing end-of-octets terminator') explicitTagDecoder = ExplicitTagDecoder() class IntegerDecoder(AbstractSimpleDecoder): protoComponent = univ.Integer(0) def valueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): if tagSet[0].tagFormat != tag.tagFormatSimple: raise error.PyAsn1Error('Simple tag format expected') head, tail = substrate[:length], substrate[length:] if not head: return self._createComponent(asn1Spec, tagSet, 0, **options), tail value = from_bytes(head, signed=True) return self._createComponent(asn1Spec, tagSet, value, **options), tail class BooleanDecoder(IntegerDecoder): protoComponent = univ.Boolean(0) def _createComponent(self, asn1Spec, tagSet, value, **options): return IntegerDecoder._createComponent(self, asn1Spec, tagSet, value and 1 or 0, **options) class BitStringDecoder(AbstractSimpleDecoder): protoComponent = univ.BitString(()) supportConstructedForm = True def valueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): head, tail = substrate[:length], substrate[length:] if substrateFun: return substrateFun(self._createComponent(asn1Spec, tagSet, noValue, **options), substrate, length) if not head: raise error.PyAsn1Error('Empty BIT STRING substrate') if tagSet[0].tagFormat == tag.tagFormatSimple: # XXX what tag to check? trailingBits = oct2int(head[0]) if trailingBits > 7: raise error.PyAsn1Error( 'Trailing bits overflow %s' % trailingBits ) value = self.protoComponent.fromOctetString(head[1:], internalFormat=True, padding=trailingBits) return self._createComponent(asn1Spec, tagSet, value, **options), tail if not self.supportConstructedForm: raise error.PyAsn1Error('Constructed encoding form prohibited at %s' % self.__class__.__name__) # All inner fragments are of the same type, treat them as octet string substrateFun = self.substrateCollector bitString = self.protoComponent.fromOctetString(null, internalFormat=True) while head: component, head = decodeFun(head, self.protoComponent, substrateFun=substrateFun, **options) trailingBits = oct2int(component[0]) if trailingBits > 7: raise error.PyAsn1Error( 'Trailing bits overflow %s' % trailingBits ) bitString = self.protoComponent.fromOctetString( component[1:], internalFormat=True, prepend=bitString, padding=trailingBits ) return self._createComponent(asn1Spec, tagSet, bitString, **options), tail def indefLenValueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): if substrateFun: return substrateFun(self._createComponent(asn1Spec, tagSet, noValue, **options), substrate, length) # All inner fragments are of the same type, treat them as octet string substrateFun = self.substrateCollector bitString = self.protoComponent.fromOctetString(null, internalFormat=True) while substrate: component, substrate = decodeFun(substrate, self.protoComponent, substrateFun=substrateFun, allowEoo=True, **options) if component is eoo.endOfOctets: break trailingBits = oct2int(component[0]) if trailingBits > 7: raise error.PyAsn1Error( 'Trailing bits overflow %s' % trailingBits ) bitString = self.protoComponent.fromOctetString( component[1:], internalFormat=True, prepend=bitString, padding=trailingBits ) else: raise error.SubstrateUnderrunError('No EOO seen before substrate ends') return self._createComponent(asn1Spec, tagSet, bitString, **options), substrate class OctetStringDecoder(AbstractSimpleDecoder): protoComponent = univ.OctetString('') supportConstructedForm = True def valueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): head, tail = substrate[:length], substrate[length:] if substrateFun: return substrateFun(self._createComponent(asn1Spec, tagSet, noValue, **options), substrate, length) if tagSet[0].tagFormat == tag.tagFormatSimple: # XXX what tag to check? return self._createComponent(asn1Spec, tagSet, head, **options), tail if not self.supportConstructedForm: raise error.PyAsn1Error('Constructed encoding form prohibited at %s' % self.__class__.__name__) # All inner fragments are of the same type, treat them as octet string substrateFun = self.substrateCollector header = null while head: component, head = decodeFun(head, self.protoComponent, substrateFun=substrateFun, **options) header += component return self._createComponent(asn1Spec, tagSet, header, **options), tail def indefLenValueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): if substrateFun and substrateFun is not self.substrateCollector: asn1Object = self._createComponent(asn1Spec, tagSet, noValue, **options) return substrateFun(asn1Object, substrate, length) # All inner fragments are of the same type, treat them as octet string substrateFun = self.substrateCollector header = null while substrate: component, substrate = decodeFun(substrate, self.protoComponent, substrateFun=substrateFun, allowEoo=True, **options) if component is eoo.endOfOctets: break header += component else: raise error.SubstrateUnderrunError( 'No EOO seen before substrate ends' ) return self._createComponent(asn1Spec, tagSet, header, **options), substrate class NullDecoder(AbstractSimpleDecoder): protoComponent = univ.Null('') def valueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): if tagSet[0].tagFormat != tag.tagFormatSimple: raise error.PyAsn1Error('Simple tag format expected') head, tail = substrate[:length], substrate[length:] component = self._createComponent(asn1Spec, tagSet, '', **options) if head: raise error.PyAsn1Error('Unexpected %d-octet substrate for Null' % length) return component, tail class ObjectIdentifierDecoder(AbstractSimpleDecoder): protoComponent = univ.ObjectIdentifier(()) def valueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): if tagSet[0].tagFormat != tag.tagFormatSimple: raise error.PyAsn1Error('Simple tag format expected') head, tail = substrate[:length], substrate[length:] if not head: raise error.PyAsn1Error('Empty substrate') head = octs2ints(head) oid = () index = 0 substrateLen = len(head) while index < substrateLen: subId = head[index] index += 1 if subId < 128: oid += (subId,) elif subId > 128: # Construct subid from a number of octets nextSubId = subId subId = 0 while nextSubId >= 128: subId = (subId << 7) + (nextSubId & 0x7F) if index >= substrateLen: raise error.SubstrateUnderrunError( 'Short substrate for sub-OID past %s' % (oid,) ) nextSubId = head[index] index += 1 oid += ((subId << 7) + nextSubId,) elif subId == 128: # ASN.1 spec forbids leading zeros (0x80) in OID # encoding, tolerating it opens a vulnerability. See # https://www.esat.kuleuven.be/cosic/publications/article-1432.pdf # page 7 raise error.PyAsn1Error('Invalid octet 0x80 in OID encoding') # Decode two leading arcs if 0 <= oid[0] <= 39: oid = (0,) + oid elif 40 <= oid[0] <= 79: oid = (1, oid[0] - 40) + oid[1:] elif oid[0] >= 80: oid = (2, oid[0] - 80) + oid[1:] else: raise error.PyAsn1Error('Malformed first OID octet: %s' % head[0]) return self._createComponent(asn1Spec, tagSet, oid, **options), tail class RealDecoder(AbstractSimpleDecoder): protoComponent = univ.Real() def valueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): if tagSet[0].tagFormat != tag.tagFormatSimple: raise error.PyAsn1Error('Simple tag format expected') head, tail = substrate[:length], substrate[length:] if not head: return self._createComponent(asn1Spec, tagSet, 0.0, **options), tail fo = oct2int(head[0]) head = head[1:] if fo & 0x80: # binary encoding if not head: raise error.PyAsn1Error("Incomplete floating-point value") n = (fo & 0x03) + 1 if n == 4: n = oct2int(head[0]) head = head[1:] eo, head = head[:n], head[n:] if not eo or not head: raise error.PyAsn1Error('Real exponent screwed') e = oct2int(eo[0]) & 0x80 and -1 or 0 while eo: # exponent e <<= 8 e |= oct2int(eo[0]) eo = eo[1:] b = fo >> 4 & 0x03 # base bits if b > 2: raise error.PyAsn1Error('Illegal Real base') if b == 1: # encbase = 8 e *= 3 elif b == 2: # encbase = 16 e *= 4 p = 0 while head: # value p <<= 8 p |= oct2int(head[0]) head = head[1:] if fo & 0x40: # sign bit p = -p sf = fo >> 2 & 0x03 # scale bits p *= 2 ** sf value = (p, 2, e) elif fo & 0x40: # infinite value value = fo & 0x01 and '-inf' or 'inf' elif fo & 0xc0 == 0: # character encoding if not head: raise error.PyAsn1Error("Incomplete floating-point value") try: if fo & 0x3 == 0x1: # NR1 value = (int(head), 10, 0) elif fo & 0x3 == 0x2: # NR2 value = float(head) elif fo & 0x3 == 0x3: # NR3 value = float(head) else: raise error.SubstrateUnderrunError( 'Unknown NR (tag %s)' % fo ) except ValueError: raise error.SubstrateUnderrunError( 'Bad character Real syntax' ) else: raise error.SubstrateUnderrunError( 'Unknown encoding (tag %s)' % fo ) return self._createComponent(asn1Spec, tagSet, value, **options), tail class AbstractConstructedDecoder(AbstractDecoder): protoComponent = None class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): protoRecordComponent = None protoSequenceComponent = None def _getComponentTagMap(self, asn1Object, idx): raise NotImplementedError() def _getComponentPositionByType(self, asn1Object, tagSet, idx): raise NotImplementedError() def _decodeComponents(self, substrate, tagSet=None, decodeFun=None, **options): components = [] componentTypes = set() while substrate: component, substrate = decodeFun(substrate, **options) if component is eoo.endOfOctets: break components.append(component) componentTypes.add(component.tagSet) # Now we have to guess is it SEQUENCE/SET or SEQUENCE OF/SET OF # The heuristics is: # * 1+ components of different types -> likely SEQUENCE/SET # * otherwise -> likely SEQUENCE OF/SET OF if len(componentTypes) > 1: protoComponent = self.protoRecordComponent else: protoComponent = self.protoSequenceComponent asn1Object = protoComponent.clone( # construct tagSet from base tag from prototype ASN.1 object # and additional tags recovered from the substrate tagSet=tag.TagSet(protoComponent.tagSet.baseTag, *tagSet.superTags) ) for idx, component in enumerate(components): asn1Object.setComponentByPosition( idx, component, verifyConstraints=False, matchTags=False, matchConstraints=False ) return asn1Object, substrate def valueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): if tagSet[0].tagFormat != tag.tagFormatConstructed: raise error.PyAsn1Error('Constructed tag format expected') head, tail = substrate[:length], substrate[length:] if substrateFun is not None: if asn1Spec is not None: asn1Object = asn1Spec.clone() elif self.protoComponent is not None: asn1Object = self.protoComponent.clone(tagSet=tagSet) else: asn1Object = self.protoRecordComponent, self.protoSequenceComponent return substrateFun(asn1Object, substrate, length) if asn1Spec is None: asn1Object, trailing = self._decodeComponents( head, tagSet=tagSet, decodeFun=decodeFun, **options ) if trailing: raise error.PyAsn1Error('Unused trailing %d octets encountered' % len(trailing)) return asn1Object, tail asn1Object = asn1Spec.clone() if asn1Spec.typeId in (univ.Sequence.typeId, univ.Set.typeId): namedTypes = asn1Spec.componentType isSetType = asn1Spec.typeId == univ.Set.typeId isDeterministic = not isSetType and not namedTypes.hasOptionalOrDefault seenIndices = set() idx = 0 while head: if not namedTypes: componentType = None elif isSetType: componentType = namedTypes.tagMapUnique else: try: if isDeterministic: componentType = namedTypes[idx].asn1Object elif namedTypes[idx].isOptional or namedTypes[idx].isDefaulted: componentType = namedTypes.getTagMapNearPosition(idx) else: componentType = namedTypes[idx].asn1Object except IndexError: raise error.PyAsn1Error( 'Excessive components decoded at %r' % (asn1Spec,) ) component, head = decodeFun(head, componentType, **options) if not isDeterministic and namedTypes: if isSetType: idx = namedTypes.getPositionByType(component.effectiveTagSet) elif namedTypes[idx].isOptional or namedTypes[idx].isDefaulted: idx = namedTypes.getPositionNearType(component.effectiveTagSet, idx) asn1Object.setComponentByPosition( idx, component, verifyConstraints=False, matchTags=False, matchConstraints=False ) seenIndices.add(idx) idx += 1 if namedTypes: if not namedTypes.requiredComponents.issubset(seenIndices): raise error.PyAsn1Error('ASN.1 object %s has uninitialized components' % asn1Object.__class__.__name__) if namedTypes.hasOpenTypes: openTypes = options.get('openTypes', {}) if openTypes or options.get('decodeOpenTypes', False): for idx, namedType in enumerate(namedTypes.namedTypes): if not namedType.openType: continue if namedType.isOptional and not asn1Object.getComponentByPosition(idx).isValue: continue governingValue = asn1Object.getComponentByName( namedType.openType.name ) try: openType = openTypes[governingValue] except KeyError: try: openType = namedType.openType[governingValue] except KeyError: continue component, rest = decodeFun( asn1Object.getComponentByPosition(idx).asOctets(), asn1Spec=openType ) asn1Object.setComponentByPosition(idx, component) else: asn1Object.verifySizeSpec() else: asn1Object = asn1Spec.clone() componentType = asn1Spec.componentType idx = 0 while head: component, head = decodeFun(head, componentType, **options) asn1Object.setComponentByPosition( idx, component, verifyConstraints=False, matchTags=False, matchConstraints=False ) idx += 1 return asn1Object, tail def indefLenValueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): if tagSet[0].tagFormat != tag.tagFormatConstructed: raise error.PyAsn1Error('Constructed tag format expected') if substrateFun is not None: if asn1Spec is not None: asn1Object = asn1Spec.clone() elif self.protoComponent is not None: asn1Object = self.protoComponent.clone(tagSet=tagSet) else: asn1Object = self.protoRecordComponent, self.protoSequenceComponent return substrateFun(asn1Object, substrate, length) if asn1Spec is None: return self._decodeComponents( substrate, tagSet=tagSet, decodeFun=decodeFun, allowEoo=True, **options ) asn1Object = asn1Spec.clone() if asn1Spec.typeId in (univ.Sequence.typeId, univ.Set.typeId): namedTypes = asn1Object.componentType isSetType = asn1Object.typeId == univ.Set.typeId isDeterministic = not isSetType and not namedTypes.hasOptionalOrDefault seenIndices = set() idx = 0 while substrate: if len(namedTypes) <= idx: asn1Spec = None elif isSetType: asn1Spec = namedTypes.tagMapUnique else: try: if isDeterministic: asn1Spec = namedTypes[idx].asn1Object elif namedTypes[idx].isOptional or namedTypes[idx].isDefaulted: asn1Spec = namedTypes.getTagMapNearPosition(idx) else: asn1Spec = namedTypes[idx].asn1Object except IndexError: raise error.PyAsn1Error( 'Excessive components decoded at %r' % (asn1Object,) ) component, substrate = decodeFun(substrate, asn1Spec, allowEoo=True, **options) if component is eoo.endOfOctets: break if not isDeterministic and namedTypes: if isSetType: idx = namedTypes.getPositionByType(component.effectiveTagSet) elif namedTypes[idx].isOptional or namedTypes[idx].isDefaulted: idx = namedTypes.getPositionNearType(component.effectiveTagSet, idx) asn1Object.setComponentByPosition( idx, component, verifyConstraints=False, matchTags=False, matchConstraints=False ) seenIndices.add(idx) idx += 1 else: raise error.SubstrateUnderrunError( 'No EOO seen before substrate ends' ) if namedTypes: if not namedTypes.requiredComponents.issubset(seenIndices): raise error.PyAsn1Error('ASN.1 object %s has uninitialized components' % asn1Object.__class__.__name__) if namedTypes.hasOpenTypes: openTypes = options.get('openTypes', None) if openTypes or options.get('decodeOpenTypes', False): for idx, namedType in enumerate(namedTypes.namedTypes): if not namedType.openType: continue if namedType.isOptional and not asn1Object.getComponentByPosition(idx).isValue: continue governingValue = asn1Object.getComponentByName( namedType.openType.name ) try: openType = openTypes[governingValue] except KeyError: try: openType = namedType.openType[governingValue] except KeyError: continue component, rest = decodeFun( asn1Object.getComponentByPosition(idx).asOctets(), asn1Spec=openType, allowEoo=True ) if component is not eoo.endOfOctets: asn1Object.setComponentByPosition(idx, component) else: asn1Object.verifySizeSpec() else: asn1Object = asn1Spec.clone() componentType = asn1Spec.componentType idx = 0 while substrate: component, substrate = decodeFun(substrate, componentType, allowEoo=True, **options) if component is eoo.endOfOctets: break asn1Object.setComponentByPosition( idx, component, verifyConstraints=False, matchTags=False, matchConstraints=False ) idx += 1 else: raise error.SubstrateUnderrunError( 'No EOO seen before substrate ends' ) return asn1Object, substrate class SequenceOrSequenceOfDecoder(UniversalConstructedTypeDecoder): protoRecordComponent = univ.Sequence() protoSequenceComponent = univ.SequenceOf() class SequenceDecoder(SequenceOrSequenceOfDecoder): protoComponent = univ.Sequence() class SequenceOfDecoder(SequenceOrSequenceOfDecoder): protoComponent = univ.SequenceOf() class SetOrSetOfDecoder(UniversalConstructedTypeDecoder): protoRecordComponent = univ.Set() protoSequenceComponent = univ.SetOf() class SetDecoder(SetOrSetOfDecoder): protoComponent = univ.Set() class SetOfDecoder(SetOrSetOfDecoder): protoComponent = univ.SetOf() class ChoiceDecoder(AbstractConstructedDecoder): protoComponent = univ.Choice() def valueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): head, tail = substrate[:length], substrate[length:] if asn1Spec is None: asn1Object = self.protoComponent.clone(tagSet=tagSet) else: asn1Object = asn1Spec.clone() if substrateFun: return substrateFun(asn1Object, substrate, length) if asn1Object.tagSet == tagSet: # explicitly tagged Choice component, head = decodeFun( head, asn1Object.componentTagMap, **options ) else: component, head = decodeFun( head, asn1Object.componentTagMap, tagSet, length, state, **options ) effectiveTagSet = component.effectiveTagSet asn1Object.setComponentByType( effectiveTagSet, component, verifyConstraints=False, matchTags=False, matchConstraints=False, innerFlag=False ) return asn1Object, tail def indefLenValueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): if asn1Spec is None: asn1Object = self.protoComponent.clone(tagSet=tagSet) else: asn1Object = asn1Spec.clone() if substrateFun: return substrateFun(asn1Object, substrate, length) if asn1Object.tagSet == tagSet: # explicitly tagged Choice component, substrate = decodeFun( substrate, asn1Object.componentType.tagMapUnique, **options ) # eat up EOO marker eooMarker, substrate = decodeFun( substrate, allowEoo=True, **options ) if eooMarker is not eoo.endOfOctets: raise error.PyAsn1Error('No EOO seen before substrate ends') else: component, substrate = decodeFun( substrate, asn1Object.componentType.tagMapUnique, tagSet, length, state, **options ) effectiveTagSet = component.effectiveTagSet asn1Object.setComponentByType( effectiveTagSet, component, verifyConstraints=False, matchTags=False, matchConstraints=False, innerFlag=False ) return asn1Object, substrate class AnyDecoder(AbstractSimpleDecoder): protoComponent = univ.Any() def valueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): if asn1Spec is None or asn1Spec is not None and tagSet != asn1Spec.tagSet: fullSubstrate = options['fullSubstrate'] # untagged Any container, recover inner header substrate length += len(fullSubstrate) - len(substrate) substrate = fullSubstrate if substrateFun: return substrateFun(self._createComponent(asn1Spec, tagSet, noValue, **options), substrate, length) head, tail = substrate[:length], substrate[length:] return self._createComponent(asn1Spec, tagSet, head, **options), tail def indefLenValueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): if asn1Spec is not None and tagSet == asn1Spec.tagSet: # tagged Any type -- consume header substrate header = null else: fullSubstrate = options['fullSubstrate'] # untagged Any, recover header substrate header = fullSubstrate[:-len(substrate)] # Any components do not inherit initial tag asn1Spec = self.protoComponent if substrateFun and substrateFun is not self.substrateCollector: asn1Object = self._createComponent(asn1Spec, tagSet, noValue, **options) return substrateFun(asn1Object, header + substrate, length + len(header)) # All inner fragments are of the same type, treat them as octet string substrateFun = self.substrateCollector while substrate: component, substrate = decodeFun(substrate, asn1Spec, substrateFun=substrateFun, allowEoo=True, **options) if component is eoo.endOfOctets: break header += component else: raise error.SubstrateUnderrunError( 'No EOO seen before substrate ends' ) if substrateFun: return header, substrate else: return self._createComponent(asn1Spec, tagSet, header, **options), substrate # character string types class UTF8StringDecoder(OctetStringDecoder): protoComponent = char.UTF8String() class NumericStringDecoder(OctetStringDecoder): protoComponent = char.NumericString() class PrintableStringDecoder(OctetStringDecoder): protoComponent = char.PrintableString() class TeletexStringDecoder(OctetStringDecoder): protoComponent = char.TeletexString() class VideotexStringDecoder(OctetStringDecoder): protoComponent = char.VideotexString() class IA5StringDecoder(OctetStringDecoder): protoComponent = char.IA5String() class GraphicStringDecoder(OctetStringDecoder): protoComponent = char.GraphicString() class VisibleStringDecoder(OctetStringDecoder): protoComponent = char.VisibleString() class GeneralStringDecoder(OctetStringDecoder): protoComponent = char.GeneralString() class UniversalStringDecoder(OctetStringDecoder): protoComponent = char.UniversalString() class BMPStringDecoder(OctetStringDecoder): protoComponent = char.BMPString() # "useful" types class ObjectDescriptorDecoder(OctetStringDecoder): protoComponent = useful.ObjectDescriptor() class GeneralizedTimeDecoder(OctetStringDecoder): protoComponent = useful.GeneralizedTime() class UTCTimeDecoder(OctetStringDecoder): protoComponent = useful.UTCTime() tagMap = { univ.Integer.tagSet: IntegerDecoder(), univ.Boolean.tagSet: BooleanDecoder(), univ.BitString.tagSet: BitStringDecoder(), univ.OctetString.tagSet: OctetStringDecoder(), univ.Null.tagSet: NullDecoder(), univ.ObjectIdentifier.tagSet: ObjectIdentifierDecoder(), univ.Enumerated.tagSet: IntegerDecoder(), univ.Real.tagSet: RealDecoder(), univ.Sequence.tagSet: SequenceOrSequenceOfDecoder(), # conflicts with SequenceOf univ.Set.tagSet: SetOrSetOfDecoder(), # conflicts with SetOf univ.Choice.tagSet: ChoiceDecoder(), # conflicts with Any # character string types char.UTF8String.tagSet: UTF8StringDecoder(), char.NumericString.tagSet: NumericStringDecoder(), char.PrintableString.tagSet: PrintableStringDecoder(), char.TeletexString.tagSet: TeletexStringDecoder(), char.VideotexString.tagSet: VideotexStringDecoder(), char.IA5String.tagSet: IA5StringDecoder(), char.GraphicString.tagSet: GraphicStringDecoder(), char.VisibleString.tagSet: VisibleStringDecoder(), char.GeneralString.tagSet: GeneralStringDecoder(), char.UniversalString.tagSet: UniversalStringDecoder(), char.BMPString.tagSet: BMPStringDecoder(), # useful types useful.ObjectDescriptor.tagSet: ObjectDescriptorDecoder(), useful.GeneralizedTime.tagSet: GeneralizedTimeDecoder(), useful.UTCTime.tagSet: UTCTimeDecoder() } # Type-to-codec map for ambiguous ASN.1 types typeMap = { univ.Set.typeId: SetDecoder(), univ.SetOf.typeId: SetOfDecoder(), univ.Sequence.typeId: SequenceDecoder(), univ.SequenceOf.typeId: SequenceOfDecoder(), univ.Choice.typeId: ChoiceDecoder(), univ.Any.typeId: AnyDecoder() } # 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 (stDecodeTag, stDecodeLength, stGetValueDecoder, stGetValueDecoderByAsn1Spec, stGetValueDecoderByTag, stTryAsExplicitTag, stDecodeValue, stDumpRawValue, stErrorCondition, stStop) = [x for x in range(10)] class Decoder(object): defaultErrorState = stErrorCondition # defaultErrorState = stDumpRawValue defaultRawDecoder = AnyDecoder() supportIndefLength = True # noinspection PyDefaultArgument def __init__(self, tagMap, typeMap={}): self.__tagMap = tagMap self.__typeMap = typeMap # Tag & TagSet objects caches self.__tagCache = {} self.__tagSetCache = {} self.__eooSentinel = ints2octs((0, 0)) def __call__(self, substrate, asn1Spec=None, tagSet=None, length=None, state=stDecodeTag, decodeFun=None, substrateFun=None, **options): if debug.logger & debug.flagDecoder: logger = debug.logger else: logger = None if logger: logger('decoder called at scope %s with state %d, working with up to %d octets of substrate: %s' % (debug.scope, state, len(substrate), debug.hexdump(substrate))) allowEoo = options.pop('allowEoo', False) # Look for end-of-octets sentinel if allowEoo and self.supportIndefLength: if substrate[:2] == self.__eooSentinel: if logger: logger('end-of-octets sentinel found') return eoo.endOfOctets, substrate[2:] value = noValue tagMap = self.__tagMap typeMap = self.__typeMap tagCache = self.__tagCache tagSetCache = self.__tagSetCache fullSubstrate = substrate while state is not stStop: if state is stDecodeTag: if not substrate: raise error.SubstrateUnderrunError( 'Short octet stream on tag decoding' ) # Decode tag isShortTag = True firstOctet = substrate[0] substrate = substrate[1:] try: lastTag = tagCache[firstOctet] except KeyError: integerTag = oct2int(firstOctet) tagClass = integerTag & 0xC0 tagFormat = integerTag & 0x20 tagId = integerTag & 0x1F if tagId == 0x1F: isShortTag = False lengthOctetIdx = 0 tagId = 0 try: while True: integerTag = oct2int(substrate[lengthOctetIdx]) lengthOctetIdx += 1 tagId <<= 7 tagId |= (integerTag & 0x7F) if not integerTag & 0x80: break substrate = substrate[lengthOctetIdx:] except IndexError: raise error.SubstrateUnderrunError( 'Short octet stream on long tag decoding' ) lastTag = tag.Tag( tagClass=tagClass, tagFormat=tagFormat, tagId=tagId ) if isShortTag: # cache short tags tagCache[firstOctet] = lastTag if tagSet is None: if isShortTag: try: tagSet = tagSetCache[firstOctet] except KeyError: # base tag not recovered tagSet = tag.TagSet((), lastTag) tagSetCache[firstOctet] = tagSet else: tagSet = tag.TagSet((), lastTag) else: tagSet = lastTag + tagSet state = stDecodeLength if logger: logger('tag decoded into %s, decoding length' % tagSet) if state is stDecodeLength: # Decode length if not substrate: raise error.SubstrateUnderrunError( 'Short octet stream on length decoding' ) firstOctet = oct2int(substrate[0]) if firstOctet < 128: size = 1 length = firstOctet elif firstOctet > 128: size = firstOctet & 0x7F # encoded in size bytes encodedLength = octs2ints(substrate[1:size + 1]) # missing check on maximum size, which shouldn't be a # problem, we can handle more than is possible if len(encodedLength) != size: raise error.SubstrateUnderrunError( '%s<%s at %s' % (size, len(encodedLength), tagSet) ) length = 0 for lengthOctet in encodedLength: length <<= 8 length |= lengthOctet size += 1 else: size = 1 length = -1 substrate = substrate[size:] if length == -1: if not self.supportIndefLength: raise error.PyAsn1Error('Indefinite length encoding not supported by this codec') else: if len(substrate) < length: raise error.SubstrateUnderrunError('%d-octet short' % (length - len(substrate))) state = stGetValueDecoder if logger: logger('value length decoded into %d, payload substrate is: %s' % (length, debug.hexdump(length == -1 and substrate or substrate[:length]))) if state is stGetValueDecoder: if asn1Spec is None: state = stGetValueDecoderByTag else: state = stGetValueDecoderByAsn1Spec # # There're two ways of creating subtypes in ASN.1 what influences # decoder operation. These methods are: # 1) Either base types used in or no IMPLICIT tagging has been # applied on subtyping. # 2) Subtype syntax drops base type information (by means of # IMPLICIT tagging. # The first case allows for complete tag recovery from substrate # while the second one requires original ASN.1 type spec for # decoding. # # In either case a set of tags (tagSet) is coming from substrate # in an incremental, tag-by-tag fashion (this is the case of # EXPLICIT tag which is most basic). Outermost tag comes first # from the wire. # if state is stGetValueDecoderByTag: try: concreteDecoder = tagMap[tagSet] except KeyError: concreteDecoder = None if concreteDecoder: state = stDecodeValue else: try: concreteDecoder = tagMap[tagSet[:1]] except KeyError: concreteDecoder = None if concreteDecoder: state = stDecodeValue else: state = stTryAsExplicitTag if logger: logger('codec %s chosen by a built-in type, decoding %s' % (concreteDecoder and concreteDecoder.__class__.__name__ or "", state is stDecodeValue and 'value' or 'as explicit tag')) debug.scope.push(concreteDecoder is None and '?' or concreteDecoder.protoComponent.__class__.__name__) if state is stGetValueDecoderByAsn1Spec: if asn1Spec.__class__ is tagmap.TagMap: try: chosenSpec = asn1Spec[tagSet] except KeyError: chosenSpec = None if logger: logger('candidate ASN.1 spec is a map of:') for firstOctet, v in asn1Spec.presentTypes.items(): logger(' %s -> %s' % (firstOctet, v.__class__.__name__)) if asn1Spec.skipTypes: logger('but neither of: ') for firstOctet, v in asn1Spec.skipTypes.items(): logger(' %s -> %s' % (firstOctet, v.__class__.__name__)) logger('new candidate ASN.1 spec is %s, chosen by %s' % (chosenSpec is None and '' or chosenSpec.prettyPrintType(), tagSet)) elif tagSet == asn1Spec.tagSet or tagSet in asn1Spec.tagMap: chosenSpec = asn1Spec if logger: logger('candidate ASN.1 spec is %s' % asn1Spec.__class__.__name__) else: chosenSpec = None if chosenSpec is not None: try: # ambiguous type or just faster codec lookup concreteDecoder = typeMap[chosenSpec.typeId] if logger: logger('value decoder chosen for an ambiguous type by type ID %s' % (chosenSpec.typeId,)) except KeyError: # use base type for codec lookup to recover untagged types baseTagSet = tag.TagSet(chosenSpec.tagSet.baseTag, chosenSpec.tagSet.baseTag) try: # base type or tagged subtype concreteDecoder = tagMap[baseTagSet] if logger: logger('value decoder chosen by base %s' % (baseTagSet,)) except KeyError: concreteDecoder = None if concreteDecoder: asn1Spec = chosenSpec state = stDecodeValue else: state = stTryAsExplicitTag else: concreteDecoder = None state = stTryAsExplicitTag if logger: logger('codec %s chosen by ASN.1 spec, decoding %s' % (state is stDecodeValue and concreteDecoder.__class__.__name__ or "", state is stDecodeValue and 'value' or 'as explicit tag')) debug.scope.push(chosenSpec is None and '?' or chosenSpec.__class__.__name__) if state is stDecodeValue: if not options.get('recursiveFlag', True) and not substrateFun: # deprecate this substrateFun = lambda a, b, c: (a, b[:c]) options.update(fullSubstrate=fullSubstrate) if length == -1: # indef length value, substrate = concreteDecoder.indefLenValueDecoder( substrate, asn1Spec, tagSet, length, stGetValueDecoder, self, substrateFun, **options ) else: value, substrate = concreteDecoder.valueDecoder( substrate, asn1Spec, tagSet, length, stGetValueDecoder, self, substrateFun, **options ) if logger: logger('codec %s yields type %s, value:\n%s\n...remaining substrate is: %s' % (concreteDecoder.__class__.__name__, value.__class__.__name__, isinstance(value, base.Asn1Item) and value.prettyPrint() or value, substrate and debug.hexdump(substrate) or '')) state = stStop break if state is stTryAsExplicitTag: if tagSet and tagSet[0].tagFormat == tag.tagFormatConstructed and tagSet[0].tagClass != tag.tagClassUniversal: # Assume explicit tagging concreteDecoder = explicitTagDecoder state = stDecodeValue else: concreteDecoder = None state = self.defaultErrorState if logger: logger('codec %s chosen, decoding %s' % (concreteDecoder and concreteDecoder.__class__.__name__ or "", state is stDecodeValue and 'value' or 'as failure')) if state is stDumpRawValue: concreteDecoder = self.defaultRawDecoder if logger: logger('codec %s chosen, decoding value' % concreteDecoder.__class__.__name__) state = stDecodeValue if state is stErrorCondition: raise error.PyAsn1Error( '%s not in asn1Spec: %r' % (tagSet, asn1Spec) ) if logger: debug.scope.pop() logger('decoder left scope %s, call completed' % debug.scope) return value, substrate #: Turns BER octet stream into an ASN.1 object. #: #: Takes BER 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) #: BER 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 BER 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 BER serialisation without ASN.1 schema #: #: .. code-block:: pycon #: #: >>> s, _ = decode(b'0\t\x02\x01\x01\x02\x01\x02\x02\x01\x03') #: >>> str(s) #: SequenceOf: #: 1 2 3 #: #: Decode BER serialisation with ASN.1 schema #: #: .. code-block:: pycon #: #: >>> seq = SequenceOf(componentType=Integer()) #: >>> s, _ = decode(b'0\t\x02\x01\x01\x02\x01\x02\x02\x01\x03', asn1Spec=seq) #: >>> str(s) #: SequenceOf: #: 1 2 3 #: decode = Decoder(tagMap, typeMap) # XXX # non-recursive decoding; return position rather than substrate