Current File : //lib/python3/dist-packages/pyasn1/codec/ber/decoder.py
#
# This file is part of pyasn1 software.
#
# Copyright (c) 2005-2019, Ilya Etingof <etingof@gmail.com>
# 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']
LOG = debug.registerLoggee(__name__, flags=debug.DEBUG_DECODER)
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)
if LOG:
LOG('explicit tag container carries %d octets of trailing payload '
'(will be lost!): %s' % (len(_), debug.hexdump(_)))
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__)
if LOG:
LOG('assembling constructed serialization')
# 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__)
if LOG:
LOG('assembling constructed serialization')
# 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")
if LOG:
LOG('decoding binary encoded REAL')
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
if LOG:
LOG('decoding infinite REAL')
value = fo & 0x01 and '-inf' or 'inf'
elif fo & 0xc0 == 0: # character encoding
if not head:
raise error.PyAsn1Error("Incomplete floating-point value")
if LOG:
LOG('decoding character encoded REAL')
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)
)
if LOG:
LOG('guessed %r container type (pass `asn1Spec` to guide the '
'decoder)' % asn1Object)
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:
if LOG:
LOG('Unused trailing %d octets encountered: %s' % (
len(trailing), debug.hexdump(trailing)))
return asn1Object, tail
asn1Object = asn1Spec.clone()
asn1Object.clear()
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
if LOG:
LOG('decoding %sdeterministic %s type %r chosen by type ID' % (
not isDeterministic and 'non-' or '', isSetType and 'SET' or '',
asn1Spec))
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 LOG:
LOG('seen component indices %s' % seenIndices)
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 LOG:
LOG('user-specified open types map:')
for k, v in openTypes.items():
LOG('%s -> %r' % (k, v))
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:
if LOG:
LOG('default open types map of component '
'"%s.%s" governed by component "%s.%s"'
':' % (asn1Object.__class__.__name__,
namedType.name,
asn1Object.__class__.__name__,
namedType.openType.name))
for k, v in namedType.openType.items():
LOG('%s -> %r' % (k, v))
try:
openType = namedType.openType[governingValue]
except KeyError:
if LOG:
LOG('failed to resolve open type by governing '
'value %r' % (governingValue,))
continue
if LOG:
LOG('resolved open type %r by governing '
'value %r' % (openType, governingValue))
containerValue = asn1Object.getComponentByPosition(idx)
if containerValue.typeId in (
univ.SetOf.typeId, univ.SequenceOf.typeId):
for pos, containerElement in enumerate(
containerValue):
component, rest = decodeFun(
containerValue[pos].asOctets(),
asn1Spec=openType, **options
)
containerValue[pos] = component
else:
component, rest = decodeFun(
asn1Object.getComponentByPosition(idx).asOctets(),
asn1Spec=openType, **options
)
asn1Object.setComponentByPosition(idx, component)
else:
inconsistency = asn1Object.isInconsistent
if inconsistency:
raise inconsistency
else:
asn1Object = asn1Spec.clone()
asn1Object.clear()
componentType = asn1Spec.componentType
if LOG:
LOG('decoding type %r chosen by given `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,
**dict(options, allowEoo=True)
)
asn1Object = asn1Spec.clone()
asn1Object.clear()
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
if LOG:
LOG('decoding %sdeterministic %s type %r chosen by type ID' % (
not isDeterministic and 'non-' or '', isSetType and 'SET' or '',
asn1Spec))
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 LOG:
LOG('seen component indices %s' % seenIndices)
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 LOG:
LOG('user-specified open types map:')
for k, v in openTypes.items():
LOG('%s -> %r' % (k, v))
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:
if LOG:
LOG('default open types map of component '
'"%s.%s" governed by component "%s.%s"'
':' % (asn1Object.__class__.__name__,
namedType.name,
asn1Object.__class__.__name__,
namedType.openType.name))
for k, v in namedType.openType.items():
LOG('%s -> %r' % (k, v))
try:
openType = namedType.openType[governingValue]
except KeyError:
if LOG:
LOG('failed to resolve open type by governing '
'value %r' % (governingValue,))
continue
if LOG:
LOG('resolved open type %r by governing '
'value %r' % (openType, governingValue))
containerValue = asn1Object.getComponentByPosition(idx)
if containerValue.typeId in (
univ.SetOf.typeId, univ.SequenceOf.typeId):
for pos, containerElement in enumerate(
containerValue):
component, rest = decodeFun(
containerValue[pos].asOctets(),
asn1Spec=openType, **dict(options, allowEoo=True)
)
containerValue[pos] = component
else:
component, rest = decodeFun(
asn1Object.getComponentByPosition(idx).asOctets(),
asn1Spec=openType, **dict(options, allowEoo=True)
)
if component is not eoo.endOfOctets:
asn1Object.setComponentByPosition(idx, component)
else:
inconsistency = asn1Object.isInconsistent
if inconsistency:
raise inconsistency
else:
asn1Object = asn1Spec.clone()
asn1Object.clear()
componentType = asn1Spec.componentType
if LOG:
LOG('decoding type %r chosen by given `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:
if LOG:
LOG('decoding %s as explicitly tagged CHOICE' % (tagSet,))
component, head = decodeFun(
head, asn1Object.componentTagMap, **options
)
else:
if LOG:
LOG('decoding %s as untagged CHOICE' % (tagSet,))
component, head = decodeFun(
head, asn1Object.componentTagMap,
tagSet, length, state, **options
)
effectiveTagSet = component.effectiveTagSet
if LOG:
LOG('decoded component %s, effective tag set %s' % (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:
if LOG:
LOG('decoding %s as explicitly tagged CHOICE' % (tagSet,))
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:
if LOG:
LOG('decoding %s as untagged CHOICE' % (tagSet,))
component, substrate = decodeFun(
substrate, asn1Object.componentType.tagMapUnique,
tagSet, length, state, **options
)
effectiveTagSet = component.effectiveTagSet
if LOG:
LOG('decoded component %s, effective tag set %s' % (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:
isUntagged = True
elif asn1Spec.__class__ is tagmap.TagMap:
isUntagged = tagSet not in asn1Spec.tagMap
else:
isUntagged = tagSet != asn1Spec.tagSet
if isUntagged:
fullSubstrate = options['fullSubstrate']
# untagged Any container, recover inner header substrate
length += len(fullSubstrate) - len(substrate)
substrate = fullSubstrate
if LOG:
LOG('decoding as untagged ANY, substrate %s' % debug.hexdump(substrate))
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 None:
isTagged = False
elif asn1Spec.__class__ is tagmap.TagMap:
isTagged = tagSet in asn1Spec.tagMap
else:
isTagged = tagSet == asn1Spec.tagSet
if isTagged:
# tagged Any type -- consume header substrate
header = null
if LOG:
LOG('decoding as tagged ANY')
else:
fullSubstrate = options['fullSubstrate']
# untagged Any, recover header substrate
header = fullSubstrate[:-len(substrate)]
if LOG:
LOG('decoding as untagged ANY, header substrate %s' % debug.hexdump(header))
# 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))
if LOG:
LOG('assembling constructed serialization')
# 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 LOG:
LOG('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 LOG:
LOG('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 LOG:
LOG('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 LOG:
LOG('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 LOG:
LOG('codec %s chosen by a built-in type, decoding %s' % (concreteDecoder and concreteDecoder.__class__.__name__ or "<none>", 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 LOG:
LOG('candidate ASN.1 spec is a map of:')
for firstOctet, v in asn1Spec.presentTypes.items():
LOG(' %s -> %s' % (firstOctet, v.__class__.__name__))
if asn1Spec.skipTypes:
LOG('but neither of: ')
for firstOctet, v in asn1Spec.skipTypes.items():
LOG(' %s -> %s' % (firstOctet, v.__class__.__name__))
LOG('new candidate ASN.1 spec is %s, chosen by %s' % (chosenSpec is None and '<none>' or chosenSpec.prettyPrintType(), tagSet))
elif tagSet == asn1Spec.tagSet or tagSet in asn1Spec.tagMap:
chosenSpec = asn1Spec
if LOG:
LOG('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 LOG:
LOG('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 LOG:
LOG('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 LOG:
LOG('codec %s chosen by ASN.1 spec, decoding %s' % (state is stDecodeValue and concreteDecoder.__class__.__name__ or "<none>", 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 LOG:
LOG('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 '<none>'))
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 LOG:
LOG('codec %s chosen, decoding %s' % (concreteDecoder and concreteDecoder.__class__.__name__ or "<none>", state is stDecodeValue and 'value' or 'as failure'))
if state is stDumpRawValue:
concreteDecoder = self.defaultRawDecoder
if LOG:
LOG('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 LOG:
debug.scope.pop()
LOG('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
#: ------
#: ~pyasn1.error.PyAsn1Error, ~pyasn1.error.SubstrateUnderrunError
#: 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
Mini Shell