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Mini Shell
# BER decoder
from pyasn1.type import tag, univ, char, useful, tagmap
from pyasn1.codec.ber import eoo
from pyasn1.compat.octets import oct2int, isOctetsType
from pyasn1 import debug, error
class AbstractDecoder:
protoComponent = None
def valueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
raise error.PyAsn1Error('Decoder not implemented for %s' % (tagSet,))
def indefLenValueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
raise error.PyAsn1Error('Indefinite length mode decoder not implemented for %s' % (tagSet,))
class AbstractSimpleDecoder(AbstractDecoder):
tagFormats = (tag.tagFormatSimple,)
def _createComponent(self, asn1Spec, tagSet, value=None):
if tagSet[0][1] not in self.tagFormats:
raise error.PyAsn1Error('Invalid tag format %s for %s' % (tagSet[0], self.protoComponent.prettyPrintType()))
if asn1Spec is None:
return self.protoComponent.clone(value, tagSet)
elif value is None:
return asn1Spec
else:
return asn1Spec.clone(value)
class AbstractConstructedDecoder(AbstractDecoder):
tagFormats = (tag.tagFormatConstructed,)
def _createComponent(self, asn1Spec, tagSet, value=None):
if tagSet[0][1] not in self.tagFormats:
raise error.PyAsn1Error('Invalid tag format %s for %s' % (tagSet[0], self.protoComponent.prettyPrintType()))
if asn1Spec is None:
return self.protoComponent.clone(tagSet)
else:
return asn1Spec.clone()
class ExplicitTagDecoder(AbstractSimpleDecoder):
protoComponent = univ.Any('')
tagFormats = (tag.tagFormatConstructed,)
def valueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
if substrateFun:
return substrateFun(
self._createComponent(asn1Spec, tagSet, ''),
substrate, length
)
head, tail = substrate[:length], substrate[length:]
value, _ = decodeFun(head, asn1Spec, tagSet, length)
return value, tail
def indefLenValueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
if substrateFun:
return substrateFun(
self._createComponent(asn1Spec, tagSet, ''),
substrate, length
)
value, substrate = decodeFun(substrate, asn1Spec, tagSet, length)
terminator, substrate = decodeFun(substrate, allowEoo=True)
if eoo.endOfOctets.isSameTypeWith(terminator) and \
terminator == eoo.endOfOctets:
return value, substrate
else:
raise error.PyAsn1Error('Missing end-of-octets terminator')
explicitTagDecoder = ExplicitTagDecoder()
class IntegerDecoder(AbstractSimpleDecoder):
protoComponent = univ.Integer(0)
precomputedValues = {
'\x00': 0,
'\x01': 1,
'\x02': 2,
'\x03': 3,
'\x04': 4,
'\x05': 5,
'\x06': 6,
'\x07': 7,
'\x08': 8,
'\x09': 9,
'\xff': -1,
'\xfe': -2,
'\xfd': -3,
'\xfc': -4,
'\xfb': -5
}
def valueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet, length,
state, decodeFun, substrateFun):
head, tail = substrate[:length], substrate[length:]
if not head:
return self._createComponent(asn1Spec, tagSet, 0), tail
if head in self.precomputedValues:
value = self.precomputedValues[head]
else:
firstOctet = oct2int(head[0])
if firstOctet & 0x80:
value = -1
else:
value = 0
for octet in head:
value = value << 8 | oct2int(octet)
return self._createComponent(asn1Spec, tagSet, value), tail
class BooleanDecoder(IntegerDecoder):
protoComponent = univ.Boolean(0)
def _createComponent(self, asn1Spec, tagSet, value=None):
return IntegerDecoder._createComponent(self, asn1Spec, tagSet, value and 1 or 0)
class BitStringDecoder(AbstractSimpleDecoder):
protoComponent = univ.BitString(())
tagFormats = (tag.tagFormatSimple, tag.tagFormatConstructed)
def valueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet, length,
state, decodeFun, substrateFun):
head, tail = substrate[:length], substrate[length:]
if tagSet[0][1] == tag.tagFormatSimple: # XXX what tag to check?
if not head:
raise error.PyAsn1Error('Empty substrate')
trailingBits = oct2int(head[0])
if trailingBits > 7:
raise error.PyAsn1Error(
'Trailing bits overflow %s' % trailingBits
)
head = head[1:]
lsb = p = 0; l = len(head)-1; b = []
while p <= l:
if p == l:
lsb = trailingBits
j = 7
o = oct2int(head[p])
while j >= lsb:
b.append((o>>j)&0x01)
j = j - 1
p = p + 1
return self._createComponent(asn1Spec, tagSet, b), tail
r = self._createComponent(asn1Spec, tagSet, ())
if substrateFun:
return substrateFun(r, substrate, length)
while head:
component, head = decodeFun(head, self.protoComponent)
r = r + component
return r, tail
def indefLenValueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
r = self._createComponent(asn1Spec, tagSet, '')
if substrateFun:
return substrateFun(r, substrate, length)
while substrate:
component, substrate = decodeFun(substrate, self.protoComponent,
allowEoo=True)
if eoo.endOfOctets.isSameTypeWith(component) and \
component == eoo.endOfOctets:
break
r = r + component
else:
raise error.SubstrateUnderrunError(
'No EOO seen before substrate ends'
)
return r, substrate
class OctetStringDecoder(AbstractSimpleDecoder):
protoComponent = univ.OctetString('')
tagFormats = (tag.tagFormatSimple, tag.tagFormatConstructed)
def valueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet, length,
state, decodeFun, substrateFun):
head, tail = substrate[:length], substrate[length:]
if tagSet[0][1] == tag.tagFormatSimple: # XXX what tag to check?
return self._createComponent(asn1Spec, tagSet, head), tail
r = self._createComponent(asn1Spec, tagSet, '')
if substrateFun:
return substrateFun(r, substrate, length)
while head:
component, head = decodeFun(head, self.protoComponent)
r = r + component
return r, tail
def indefLenValueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
r = self._createComponent(asn1Spec, tagSet, '')
if substrateFun:
return substrateFun(r, substrate, length)
while substrate:
component, substrate = decodeFun(substrate, self.protoComponent,
allowEoo=True)
if eoo.endOfOctets.isSameTypeWith(component) and \
component == eoo.endOfOctets:
break
r = r + component
else:
raise error.SubstrateUnderrunError(
'No EOO seen before substrate ends'
)
return r, substrate
class NullDecoder(AbstractSimpleDecoder):
protoComponent = univ.Null('')
def valueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
head, tail = substrate[:length], substrate[length:]
r = self._createComponent(asn1Spec, tagSet)
if head:
raise error.PyAsn1Error('Unexpected %d-octet substrate for Null' % length)
return r, tail
class ObjectIdentifierDecoder(AbstractSimpleDecoder):
protoComponent = univ.ObjectIdentifier(())
def valueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet, length,
state, decodeFun, substrateFun):
head, tail = substrate[:length], substrate[length:]
if not head:
raise error.PyAsn1Error('Empty substrate')
oid = ()
index = 0
substrateLen = len(head)
while index < substrateLen:
subId = oct2int(head[index])
index += 1
if subId < 128:
oid = 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 = oct2int(head[index])
index += 1
oid = oid + ((subId << 7) + nextSubId,)
elif subId == 128:
# ASN.1 spec forbids leading zeros (0x80) in OID
# encoding, tolerating it opens a vulnerability. See
# http://www.cosic.esat.kuleuven.be/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), tail
class RealDecoder(AbstractSimpleDecoder):
protoComponent = univ.Real()
def valueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
head, tail = substrate[:length], substrate[length:]
if not head:
return self._createComponent(asn1Spec, tagSet, 0.0), 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), tail
class SequenceDecoder(AbstractConstructedDecoder):
protoComponent = univ.Sequence()
def _getComponentTagMap(self, r, idx):
try:
return r.getComponentTagMapNearPosition(idx)
except error.PyAsn1Error:
return
def _getComponentPositionByType(self, r, t, idx):
return r.getComponentPositionNearType(t, idx)
def valueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
head, tail = substrate[:length], substrate[length:]
r = self._createComponent(asn1Spec, tagSet)
idx = 0
if substrateFun:
return substrateFun(r, substrate, length)
while head:
asn1Spec = self._getComponentTagMap(r, idx)
component, head = decodeFun(head, asn1Spec)
idx = self._getComponentPositionByType(
r, component.getEffectiveTagSet(), idx
)
r.setComponentByPosition(idx, component, asn1Spec is None)
idx = idx + 1
r.setDefaultComponents()
r.verifySizeSpec()
return r, tail
def indefLenValueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
r = self._createComponent(asn1Spec, tagSet)
if substrateFun:
return substrateFun(r, substrate, length)
idx = 0
while substrate:
asn1Spec = self._getComponentTagMap(r, idx)
component, substrate = decodeFun(substrate, asn1Spec, allowEoo=True)
if eoo.endOfOctets.isSameTypeWith(component) and \
component == eoo.endOfOctets:
break
idx = self._getComponentPositionByType(
r, component.getEffectiveTagSet(), idx
)
r.setComponentByPosition(idx, component, asn1Spec is None)
idx = idx + 1
else:
raise error.SubstrateUnderrunError(
'No EOO seen before substrate ends'
)
r.setDefaultComponents()
r.verifySizeSpec()
return r, substrate
class SequenceOfDecoder(AbstractConstructedDecoder):
protoComponent = univ.SequenceOf()
def valueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
head, tail = substrate[:length], substrate[length:]
r = self._createComponent(asn1Spec, tagSet)
if substrateFun:
return substrateFun(r, substrate, length)
asn1Spec = r.getComponentType()
idx = 0
while head:
component, head = decodeFun(head, asn1Spec)
r.setComponentByPosition(idx, component, asn1Spec is None)
idx = idx + 1
r.verifySizeSpec()
return r, tail
def indefLenValueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
r = self._createComponent(asn1Spec, tagSet)
if substrateFun:
return substrateFun(r, substrate, length)
asn1Spec = r.getComponentType()
idx = 0
while substrate:
component, substrate = decodeFun(substrate, asn1Spec, allowEoo=True)
if eoo.endOfOctets.isSameTypeWith(component) and \
component == eoo.endOfOctets:
break
r.setComponentByPosition(idx, component, asn1Spec is None)
idx = idx + 1
else:
raise error.SubstrateUnderrunError(
'No EOO seen before substrate ends'
)
r.verifySizeSpec()
return r, substrate
class SetDecoder(SequenceDecoder):
protoComponent = univ.Set()
def _getComponentTagMap(self, r, idx):
return r.getComponentTagMap()
def _getComponentPositionByType(self, r, t, idx):
nextIdx = r.getComponentPositionByType(t)
if nextIdx is None:
return idx
else:
return nextIdx
class SetOfDecoder(SequenceOfDecoder):
protoComponent = univ.SetOf()
class ChoiceDecoder(AbstractConstructedDecoder):
protoComponent = univ.Choice()
tagFormats = (tag.tagFormatSimple, tag.tagFormatConstructed)
def valueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
head, tail = substrate[:length], substrate[length:]
r = self._createComponent(asn1Spec, tagSet)
if substrateFun:
return substrateFun(r, substrate, length)
if r.getTagSet() == tagSet: # explicitly tagged Choice
component, head = decodeFun(
head, r.getComponentTagMap()
)
else:
component, head = decodeFun(
head, r.getComponentTagMap(), tagSet, length, state
)
if isinstance(component, univ.Choice):
effectiveTagSet = component.getEffectiveTagSet()
else:
effectiveTagSet = component.getTagSet()
r.setComponentByType(effectiveTagSet, component, 0, asn1Spec is None)
return r, tail
def indefLenValueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
r = self._createComponent(asn1Spec, tagSet)
if substrateFun:
return substrateFun(r, substrate, length)
if r.getTagSet() == tagSet: # explicitly tagged Choice
component, substrate = decodeFun(substrate, r.getComponentTagMap())
# eat up EOO marker
eooMarker, substrate = decodeFun(substrate, allowEoo=True)
if not eoo.endOfOctets.isSameTypeWith(eooMarker) or \
eooMarker != eoo.endOfOctets:
raise error.PyAsn1Error('No EOO seen before substrate ends')
else:
component, substrate= decodeFun(
substrate, r.getComponentTagMap(), tagSet, length, state
)
if isinstance(component, univ.Choice):
effectiveTagSet = component.getEffectiveTagSet()
else:
effectiveTagSet = component.getTagSet()
r.setComponentByType(effectiveTagSet, component, 0, asn1Spec is None)
return r, substrate
class AnyDecoder(AbstractSimpleDecoder):
protoComponent = univ.Any()
tagFormats = (tag.tagFormatSimple, tag.tagFormatConstructed)
def valueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
if asn1Spec is None or \
asn1Spec is not None and tagSet != asn1Spec.getTagSet():
# untagged Any container, recover inner header substrate
length = length + len(fullSubstrate) - len(substrate)
substrate = fullSubstrate
if substrateFun:
return substrateFun(self._createComponent(asn1Spec, tagSet),
substrate, length)
head, tail = substrate[:length], substrate[length:]
return self._createComponent(asn1Spec, tagSet, value=head), tail
def indefLenValueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet,
length, state, decodeFun, substrateFun):
if asn1Spec is not None and tagSet == asn1Spec.getTagSet():
# tagged Any type -- consume header substrate
header = ''
else:
# untagged Any, recover header substrate
header = fullSubstrate[:-len(substrate)]
r = self._createComponent(asn1Spec, tagSet, header)
# Any components do not inherit initial tag
asn1Spec = self.protoComponent
if substrateFun:
return substrateFun(r, substrate, length)
while substrate:
component, substrate = decodeFun(substrate, asn1Spec, allowEoo=True)
if eoo.endOfOctets.isSameTypeWith(component) and \
component == eoo.endOfOctets:
break
r = r + component
else:
raise error.SubstrateUnderrunError(
'No EOO seen before substrate ends'
)
return r, 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: SequenceDecoder(), # conflicts with SequenceOf
univ.Set.tagSet: SetDecoder(), # 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()
}
( stDecodeTag, stDecodeLength, stGetValueDecoder, stGetValueDecoderByAsn1Spec,
stGetValueDecoderByTag, stTryAsExplicitTag, stDecodeValue,
stDumpRawValue, stErrorCondition, stStop ) = [x for x in range(10)]
class Decoder:
defaultErrorState = stErrorCondition
# defaultErrorState = stDumpRawValue
defaultRawDecoder = AnyDecoder()
supportIndefLength = True
def __init__(self, tagMap, typeMap={}):
self.__tagMap = tagMap
self.__typeMap = typeMap
# Tag & TagSet objects caches
self.__tagCache = {}
self.__tagSetCache = {}
def __call__(self, substrate, asn1Spec=None, tagSet=None,
length=None, state=stDecodeTag, recursiveFlag=1,
substrateFun=None, allowEoo=False):
if debug.logger & debug.flagDecoder:
debug.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)))
fullSubstrate = substrate
while state != stStop:
if state == stDecodeTag:
if not substrate:
raise error.SubstrateUnderrunError(
'Short octet stream on tag decoding'
)
if not isOctetsType(substrate) and \
not isinstance(substrate, univ.OctetString):
raise error.PyAsn1Error('Bad octet stream type')
# Decode tag
firstOctet = substrate[0]
substrate = substrate[1:]
if firstOctet in self.__tagCache:
lastTag = self.__tagCache[firstOctet]
else:
t = oct2int(firstOctet)
# Look for end-of-octets sentinel
if t == 0:
if substrate and oct2int(substrate[0]) == 0:
if allowEoo and self.supportIndefLength:
debug.logger and debug.logger & debug.flagDecoder and debug.logger('end-of-octets sentinel found')
value, substrate = eoo.endOfOctets, substrate[1:]
state = stStop
continue
else:
raise error.PyAsn1Error('Unexpected end-of-contents sentinel')
else:
raise error.PyAsn1Error('Zero tag encountered')
tagClass = t&0xC0
tagFormat = t&0x20
tagId = t&0x1F
if tagId == 0x1F:
tagId = 0
while 1:
if not substrate:
raise error.SubstrateUnderrunError(
'Short octet stream on long tag decoding'
)
t = oct2int(substrate[0])
tagId = tagId << 7 | (t&0x7F)
substrate = substrate[1:]
if not t&0x80:
break
lastTag = tag.Tag(
tagClass=tagClass, tagFormat=tagFormat, tagId=tagId
)
if tagId < 31:
# cache short tags
self.__tagCache[firstOctet] = lastTag
if tagSet is None:
if firstOctet in self.__tagSetCache:
tagSet = self.__tagSetCache[firstOctet]
else:
# base tag not recovered
tagSet = tag.TagSet((), lastTag)
if firstOctet in self.__tagCache:
self.__tagSetCache[firstOctet] = tagSet
else:
tagSet = lastTag + tagSet
state = stDecodeLength
debug.logger and debug.logger & debug.flagDecoder and debug.logger('tag decoded into %s, decoding length' % tagSet)
if state == 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 = -1
elif firstOctet < 128:
length, size = firstOctet, 1
else:
size = firstOctet & 0x7F
# encoded in size bytes
length = 0
lengthString = substrate[1:size+1]
# missing check on maximum size, which shouldn't be a
# problem, we can handle more than is possible
if len(lengthString) != size:
raise error.SubstrateUnderrunError(
'%s<%s at %s' %
(size, len(lengthString), tagSet)
)
for char in lengthString:
length = (length << 8) | oct2int(char)
size = size + 1
substrate = substrate[size:]
if length != -1 and len(substrate) < length:
raise error.SubstrateUnderrunError(
'%d-octet short' % (length - len(substrate))
)
if length == -1 and not self.supportIndefLength:
error.PyAsn1Error('Indefinite length encoding not supported by this codec')
state = stGetValueDecoder
debug.logger and debug.logger & debug.flagDecoder and debug.logger('value length decoded into %d, payload substrate is: %s' % (length, debug.hexdump(length == -1 and substrate or substrate[:length])))
if state == 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 == stGetValueDecoderByTag:
if tagSet in self.__tagMap:
concreteDecoder = self.__tagMap[tagSet]
else:
concreteDecoder = None
if concreteDecoder:
state = stDecodeValue
else:
_k = tagSet[:1]
if _k in self.__tagMap:
concreteDecoder = self.__tagMap[_k]
else:
concreteDecoder = None
if concreteDecoder:
state = stDecodeValue
else:
state = stTryAsExplicitTag
if debug.logger and debug.logger & debug.flagDecoder:
debug.logger('codec %s chosen by a built-in type, decoding %s' % (concreteDecoder and concreteDecoder.__class__.__name__ or "<none>", state == stDecodeValue and 'value' or 'as explicit tag'))
debug.scope.push(concreteDecoder is None and '?' or concreteDecoder.protoComponent.__class__.__name__)
if state == stGetValueDecoderByAsn1Spec:
if isinstance(asn1Spec, (dict, tagmap.TagMap)):
if tagSet in asn1Spec:
__chosenSpec = asn1Spec[tagSet]
else:
__chosenSpec = None
if debug.logger and debug.logger & debug.flagDecoder:
debug.logger('candidate ASN.1 spec is a map of:')
for t, v in asn1Spec.getPosMap().items():
debug.logger(' %s -> %s' % (t, v.__class__.__name__))
if asn1Spec.getNegMap():
debug.logger('but neither of: ')
for t, v in asn1Spec.getNegMap().items():
debug.logger(' %s -> %s' % (t, v.__class__.__name__))
debug.logger('new candidate ASN.1 spec is %s, chosen by %s' % (__chosenSpec is None and '<none>' or __chosenSpec.prettyPrintType(), tagSet))
else:
__chosenSpec = asn1Spec
debug.logger and debug.logger & debug.flagDecoder and debug.logger('candidate ASN.1 spec is %s' % asn1Spec.__class__.__name__)
if __chosenSpec is not None and (
tagSet == __chosenSpec.getTagSet() or \
tagSet in __chosenSpec.getTagMap()
):
# use base type for codec lookup to recover untagged types
baseTagSet = __chosenSpec.baseTagSet
if __chosenSpec.typeId is not None and \
__chosenSpec.typeId in self.__typeMap:
# ambiguous type
concreteDecoder = self.__typeMap[__chosenSpec.typeId]
debug.logger and debug.logger & debug.flagDecoder and debug.logger('value decoder chosen for an ambiguous type by type ID %s' % (__chosenSpec.typeId,))
elif baseTagSet in self.__tagMap:
# base type or tagged subtype
concreteDecoder = self.__tagMap[baseTagSet]
debug.logger and debug.logger & debug.flagDecoder and debug.logger('value decoder chosen by base %s' % (baseTagSet,))
else:
concreteDecoder = None
if concreteDecoder:
asn1Spec = __chosenSpec
state = stDecodeValue
else:
state = stTryAsExplicitTag
else:
concreteDecoder = None
state = stTryAsExplicitTag
if debug.logger and debug.logger & debug.flagDecoder:
debug.logger('codec %s chosen by ASN.1 spec, decoding %s' % (state == stDecodeValue and concreteDecoder.__class__.__name__ or "<none>", state == stDecodeValue and 'value' or 'as explicit tag'))
debug.scope.push(__chosenSpec is None and '?' or __chosenSpec.__class__.__name__)
if state == stTryAsExplicitTag:
if tagSet and \
tagSet[0][1] == tag.tagFormatConstructed and \
tagSet[0][0] != tag.tagClassUniversal:
# Assume explicit tagging
concreteDecoder = explicitTagDecoder
state = stDecodeValue
else:
concreteDecoder = None
state = self.defaultErrorState
debug.logger and debug.logger & debug.flagDecoder and debug.logger('codec %s chosen, decoding %s' % (concreteDecoder and concreteDecoder.__class__.__name__ or "<none>", state == stDecodeValue and 'value' or 'as failure'))
if state == stDumpRawValue:
concreteDecoder = self.defaultRawDecoder
debug.logger and debug.logger & debug.flagDecoder and debug.logger('codec %s chosen, decoding value' % concreteDecoder.__class__.__name__)
state = stDecodeValue
if state == stDecodeValue:
if recursiveFlag == 0 and not substrateFun: # legacy
substrateFun = lambda a,b,c: (a,b[:c])
if length == -1: # indef length
value, substrate = concreteDecoder.indefLenValueDecoder(
fullSubstrate, substrate, asn1Spec, tagSet, length,
stGetValueDecoder, self, substrateFun
)
else:
value, substrate = concreteDecoder.valueDecoder(
fullSubstrate, substrate, asn1Spec, tagSet, length,
stGetValueDecoder, self, substrateFun
)
state = stStop
debug.logger and debug.logger & debug.flagDecoder and debug.logger('codec %s yields type %s, value:\n%s\n...remaining substrate is: %s' % (concreteDecoder.__class__.__name__, value.__class__.__name__, value.prettyPrint(), substrate and debug.hexdump(substrate) or '<none>'))
if state == stErrorCondition:
raise error.PyAsn1Error(
'%s not in asn1Spec: %s' % (tagSet, asn1Spec)
)
if debug.logger and debug.logger & debug.flagDecoder:
debug.scope.pop()
debug.logger('decoder left scope %s, call completed' % debug.scope)
return value, substrate
decode = Decoder(tagMap, typeMap)
# XXX
# non-recursive decoding; return position rather than substrate
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