diff options
Diffstat (limited to 'pyasn1/codec/ber/decoder.py')
| -rw-r--r-- | pyasn1/codec/ber/decoder.py | 433 |
1 files changed, 259 insertions, 174 deletions
diff --git a/pyasn1/codec/ber/decoder.py b/pyasn1/codec/ber/decoder.py index 5759ab8..44c1c9d 100644 --- a/pyasn1/codec/ber/decoder.py +++ b/pyasn1/codec/ber/decoder.py @@ -4,11 +4,16 @@ # Copyright (c) 2005-2019, Ilya Etingof <etingof@gmail.com> # License: http://snmplabs.com/pyasn1/license.html # +import os +import sys +from io import BytesIO, BufferedReader + 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.error import PyAsn1Error from pyasn1.type import base from pyasn1.type import char from pyasn1.type import tag @@ -16,13 +21,71 @@ from pyasn1.type import tagmap from pyasn1.type import univ from pyasn1.type import useful -__all__ = ['decode'] + +__all__ = ['decodeStream'] LOG = debug.registerLoggee(__name__, flags=debug.DEBUG_DECODER) noValue = base.noValue +_BUFFER_SIZE = 1024 +_PY2 = sys.version_info < (3,) + + +def asSeekableStream(substrate): + """Convert object to seekable bytes stream. + + :type substrate: Union[bytes, IOBase, univ.OctetString] + :rtype: IOBase + """ + if isinstance(substrate, bytes): + return BytesIO(substrate) + elif isinstance(substrate, univ.OctetString): + return BytesIO(substrate.asOctets()) + try: + if _PY2 and isinstance(substrate, file): + return BytesIO(substrate.read()) # Not optimal for really large files + elif not substrate.seekable(): + return BufferedReader(substrate, _BUFFER_SIZE) + else: + return substrate + except AttributeError as f: + print(f) + raise TypeError("Cannot convert " + substrate.__class__.__name__ + " to seekable bit stream.") + + +def endOfStream(substrate): + """Check whether we have reached an end of stream. + + :type substrate: IOBase + :rtype: bool + """ + if isinstance(substrate, BytesIO): + cp = substrate.tell() + substrate.seek(0, os.SEEK_END) + result = not(substrate.tell() - cp) + substrate.seek(cp, os.SEEK_SET) + return result + else: + return not substrate.peek(1) + + +def peek(substrate, size=-1): + """Peak the stream + + :param size: + """ + if hasattr(substrate, "peek"): + return substrate.peek(size) + else: + current_position = substrate.tell() + try: + return substrate.read(size) + finally: + substrate.seek(current_position) + + class AbstractDecoder(object): protoComponent = None @@ -30,19 +93,28 @@ class AbstractDecoder(object): tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): - raise error.PyAsn1Error('Decoder not implemented for %s' % (tagSet,)) + """Decode value with fixed byte length. + + If the decoder does not consume a precise byte length, + it is considered an error. + """ + raise error.PyAsn1Error('Decoder not implemented for %s' % (tagSet,)) # TODO: Seems more like an NotImplementedError? 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,)) + """Decode value with undefined length. + + The decoder is allowed to consume as many bytes as necessary. + """ + raise error.PyAsn1Error('Indefinite length mode decoder not implemented for %s' % (tagSet,)) # TODO: Seems more like an NotImplementedError? class AbstractSimpleDecoder(AbstractDecoder): @staticmethod def substrateCollector(asn1Object, substrate, length): - return substrate[:length], substrate[length:] + return substrate.read(length) def _createComponent(self, asn1Spec, tagSet, value, **options): if options.get('native'): @@ -67,16 +139,14 @@ class ExplicitTagDecoder(AbstractSimpleDecoder): self._createComponent(asn1Spec, tagSet, '', **options), substrate, length ) + value = decodeFun(substrate, asn1Spec, tagSet, length, **options) - head, tail = substrate[:length], substrate[length:] - - value, _ = decodeFun(head, asn1Spec, tagSet, length, **options) + # TODO: + # if LOG: + # LOG('explicit tag container carries %d octets of trailing payload ' + # '(will be lost!): %s' % (len(_), debug.hexdump(_))) - if LOG: - LOG('explicit tag container carries %d octets of trailing payload ' - '(will be lost!): %s' % (len(_), debug.hexdump(_))) - - return value, tail + return value def indefLenValueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, @@ -88,12 +158,12 @@ class ExplicitTagDecoder(AbstractSimpleDecoder): substrate, length ) - value, substrate = decodeFun(substrate, asn1Spec, tagSet, length, **options) + value = decodeFun(substrate, asn1Spec, tagSet, length, **options) - eooMarker, substrate = decodeFun(substrate, allowEoo=True, **options) + eooMarker = decodeFun(substrate, allowEoo=True, **options) if eooMarker is eoo.endOfOctets: - return value, substrate + return value else: raise error.PyAsn1Error('Missing end-of-octets terminator') @@ -112,14 +182,13 @@ class IntegerDecoder(AbstractSimpleDecoder): if tagSet[0].tagFormat != tag.tagFormatSimple: raise error.PyAsn1Error('Simple tag format expected') - head, tail = substrate[:length], substrate[length:] + the_bytes = substrate.read(length) + if len(the_bytes) == 0: + return self._createComponent(asn1Spec, tagSet, 0, **options) - if not head: - return self._createComponent(asn1Spec, tagSet, 0, **options), tail - - value = from_bytes(head, signed=True) + value = from_bytes(the_bytes, signed=True) - return self._createComponent(asn1Spec, tagSet, value, **options), tail + return self._createComponent(asn1Spec, tagSet, value, **options) class BooleanDecoder(IntegerDecoder): @@ -138,27 +207,26 @@ class BitStringDecoder(AbstractSimpleDecoder): 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: + if endOfStream(substrate) or not length: raise error.PyAsn1Error('Empty BIT STRING substrate') if tagSet[0].tagFormat == tag.tagFormatSimple: # XXX what tag to check? - trailingBits = oct2int(head[0]) + trailingBits = ord(substrate.read(1)) if trailingBits > 7: raise error.PyAsn1Error( 'Trailing bits overflow %s' % trailingBits ) value = self.protoComponent.fromOctetString( - head[1:], internalFormat=True, padding=trailingBits) + substrate.read(length - 1), internalFormat=True, padding=trailingBits) - return self._createComponent(asn1Spec, tagSet, value, **options), tail + return self._createComponent(asn1Spec, tagSet, value, **options) if not self.supportConstructedForm: raise error.PyAsn1Error('Constructed encoding form prohibited ' @@ -172,8 +240,10 @@ class BitStringDecoder(AbstractSimpleDecoder): bitString = self.protoComponent.fromOctetString(null, internalFormat=True) - while head: - component, head = decodeFun(head, self.protoComponent, + current_position = substrate.tell() + + while substrate.tell() - current_position < length: + component = decodeFun(substrate, self.protoComponent, substrateFun=substrateFun, **options) trailingBits = oct2int(component[0]) @@ -187,7 +257,7 @@ class BitStringDecoder(AbstractSimpleDecoder): prepend=bitString, padding=trailingBits ) - return self._createComponent(asn1Spec, tagSet, bitString, **options), tail + return self._createComponent(asn1Spec, tagSet, bitString, **options) def indefLenValueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, @@ -202,12 +272,14 @@ class BitStringDecoder(AbstractSimpleDecoder): bitString = self.protoComponent.fromOctetString(null, internalFormat=True) - while substrate: - component, substrate = decodeFun(substrate, self.protoComponent, - substrateFun=substrateFun, - allowEoo=True, **options) + while True: + component = decodeFun(substrate, self.protoComponent, + substrateFun=substrateFun, + allowEoo=True, **options) if component is eoo.endOfOctets: break + if component is None: + raise error.SubstrateUnderrunError('No EOO seen before substrate ends') trailingBits = oct2int(component[0]) if trailingBits > 7: @@ -220,10 +292,7 @@ class BitStringDecoder(AbstractSimpleDecoder): prepend=bitString, padding=trailingBits ) - else: - raise error.SubstrateUnderrunError('No EOO seen before substrate ends') - - return self._createComponent(asn1Spec, tagSet, bitString, **options), substrate + return self._createComponent(asn1Spec, tagSet, bitString, **options) class OctetStringDecoder(AbstractSimpleDecoder): @@ -234,14 +303,12 @@ class OctetStringDecoder(AbstractSimpleDecoder): 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 + return self._createComponent(asn1Spec, tagSet, substrate.read(length), **options) if not self.supportConstructedForm: raise error.PyAsn1Error('Constructed encoding form prohibited at %s' % self.__class__.__name__) @@ -254,13 +321,15 @@ class OctetStringDecoder(AbstractSimpleDecoder): header = null - while head: - component, head = decodeFun(head, self.protoComponent, + original_position = substrate.tell() + # head = popSubstream(substrate, length) + while substrate.tell() - original_position < length: + component = decodeFun(substrate, self.protoComponent, substrateFun=substrateFun, **options) header += component - return self._createComponent(asn1Spec, tagSet, header, **options), tail + return self._createComponent(asn1Spec, tagSet, header, **options) def indefLenValueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, @@ -275,22 +344,21 @@ class OctetStringDecoder(AbstractSimpleDecoder): header = null - while substrate: - component, substrate = decodeFun(substrate, + while True: + component = decodeFun(substrate, self.protoComponent, substrateFun=substrateFun, allowEoo=True, **options) if component is eoo.endOfOctets: break + if not component: + raise error.SubstrateUnderrunError( + 'No EOO seen before substrate ends' + ) header += component - else: - raise error.SubstrateUnderrunError( - 'No EOO seen before substrate ends' - ) - - return self._createComponent(asn1Spec, tagSet, header, **options), substrate + return self._createComponent(asn1Spec, tagSet, header, **options) class NullDecoder(AbstractSimpleDecoder): @@ -304,14 +372,14 @@ class NullDecoder(AbstractSimpleDecoder): if tagSet[0].tagFormat != tag.tagFormatSimple: raise error.PyAsn1Error('Simple tag format expected') - head, tail = substrate[:length], substrate[length:] + head = substrate.read(length) component = self._createComponent(asn1Spec, tagSet, '', **options) if head: raise error.PyAsn1Error('Unexpected %d-octet substrate for Null' % length) - return component, tail + return component class ObjectIdentifierDecoder(AbstractSimpleDecoder): @@ -324,7 +392,7 @@ class ObjectIdentifierDecoder(AbstractSimpleDecoder): if tagSet[0].tagFormat != tag.tagFormatSimple: raise error.PyAsn1Error('Simple tag format expected') - head, tail = substrate[:length], substrate[length:] + head = substrate.read(length) if not head: raise error.PyAsn1Error('Empty substrate') @@ -368,7 +436,7 @@ class ObjectIdentifierDecoder(AbstractSimpleDecoder): else: raise error.PyAsn1Error('Malformed first OID octet: %s' % head[0]) - return self._createComponent(asn1Spec, tagSet, oid, **options), tail + return self._createComponent(asn1Spec, tagSet, oid, **options) class RealDecoder(AbstractSimpleDecoder): @@ -381,10 +449,10 @@ class RealDecoder(AbstractSimpleDecoder): if tagSet[0].tagFormat != tag.tagFormatSimple: raise error.PyAsn1Error('Simple tag format expected') - head, tail = substrate[:length], substrate[length:] + head = substrate.read(length) if not head: - return self._createComponent(asn1Spec, tagSet, 0.0, **options), tail + return self._createComponent(asn1Spec, tagSet, 0.0, **options) fo = oct2int(head[0]) head = head[1:] @@ -475,7 +543,7 @@ class RealDecoder(AbstractSimpleDecoder): 'Unknown encoding (tag %s)' % fo ) - return self._createComponent(asn1Spec, tagSet, value, **options), tail + return self._createComponent(asn1Spec, tagSet, value, **options) class AbstractConstructedDecoder(AbstractDecoder): @@ -496,10 +564,13 @@ class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): components = [] componentTypes = set() - while substrate: - component, substrate = decodeFun(substrate, **options) + while True: + component = decodeFun(substrate, **options) if component is eoo.endOfOctets: break + if component is None: + # TODO: Not an error in this case? + break components.append(component) componentTypes.add(component.tagSet) @@ -531,7 +602,7 @@ class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): matchTags=False, matchConstraints=False ) - return asn1Object, substrate + return asn1Object def valueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, @@ -540,7 +611,7 @@ class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): if tagSet[0].tagFormat != tag.tagFormatConstructed: raise error.PyAsn1Error('Constructed tag format expected') - head, tail = substrate[:length], substrate[length:] + original_position = substrate.tell() if substrateFun is not None: if asn1Spec is not None: @@ -555,16 +626,17 @@ class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): return substrateFun(asn1Object, substrate, length) if asn1Spec is None: - asn1Object, trailing = self._decodeComponents( - head, tagSet=tagSet, decodeFun=decodeFun, **options + asn1Object = self._decodeComponents( + substrate, tagSet=tagSet, decodeFun=decodeFun, **options ) - if trailing: + if substrate.tell() < original_position + length: if LOG: + trailing = substrate.read() LOG('Unused trailing %d octets encountered: %s' % ( len(trailing), debug.hexdump(trailing))) - return asn1Object, tail + return asn1Object asn1Object = asn1Spec.clone() asn1Object.clear() @@ -583,7 +655,7 @@ class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): seenIndices = set() idx = 0 - while head: + while substrate.tell() - original_position < length: if not namedTypes: componentType = None @@ -606,7 +678,7 @@ class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): 'Excessive components decoded at %r' % (asn1Spec,) ) - component, head = decodeFun(head, componentType, **options) + component = decodeFun(substrate, componentType, **options) if not isDeterministic and namedTypes: if isSetType: @@ -679,16 +751,16 @@ class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): for pos, containerElement in enumerate( containerValue): - component, rest = decodeFun( - containerValue[pos].asOctets(), + component = decodeFun( + asSeekableStream(containerValue[pos].asOctets()), asn1Spec=openType, **options ) containerValue[pos] = component else: - component, rest = decodeFun( - asn1Object.getComponentByPosition(idx).asOctets(), + component = decodeFun( + asSeekableStream(asn1Object.getComponentByPosition(idx).asOctets()), asn1Spec=openType, **options ) @@ -710,8 +782,8 @@ class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): idx = 0 - while head: - component, head = decodeFun(head, componentType, **options) + while substrate.tell() - original_position < length: + component = decodeFun(substrate, componentType, **options) asn1Object.setComponentByPosition( idx, component, verifyConstraints=False, @@ -720,7 +792,7 @@ class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): idx += 1 - return asn1Object, tail + return asn1Object def indefLenValueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, @@ -764,7 +836,7 @@ class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): seenIndices = set() idx = 0 - while substrate: + while True: #not endOfStream(substrate): if len(namedTypes) <= idx: asn1Spec = None @@ -787,9 +859,13 @@ class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): 'Excessive components decoded at %r' % (asn1Object,) ) - component, substrate = decodeFun(substrate, asn1Spec, allowEoo=True, **options) + component = decodeFun(substrate, asn1Spec, allowEoo=True, **options) if component is eoo.endOfOctets: break + if component is None: + raise error.SubstrateUnderrunError( + 'No EOO seen before substrate ends' + ) if not isDeterministic and namedTypes: if isSetType: @@ -806,11 +882,6 @@ class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): seenIndices.add(idx) idx += 1 - else: - raise error.SubstrateUnderrunError( - 'No EOO seen before substrate ends' - ) - if LOG: LOG('seen component indices %s' % seenIndices) @@ -864,16 +935,16 @@ class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): for pos, containerElement in enumerate( containerValue): - component, rest = decodeFun( - containerValue[pos].asOctets(), + component = decodeFun( + asSeekableStream(containerValue[pos].asOctets()), asn1Spec=openType, **dict(options, allowEoo=True) ) containerValue[pos] = component else: - component, rest = decodeFun( - asn1Object.getComponentByPosition(idx).asOctets(), + component = decodeFun( + asSeekableStream(asn1Object.getComponentByPosition(idx).asOctets()), asn1Spec=openType, **dict(options, allowEoo=True) ) @@ -896,11 +967,15 @@ class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): idx = 0 - while substrate: - component, substrate = decodeFun(substrate, componentType, allowEoo=True, **options) + while True: + component = decodeFun(substrate, componentType, allowEoo=True, **options) if component is eoo.endOfOctets: break + if component is None: + raise error.SubstrateUnderrunError( + 'No EOO seen before substrate ends' + ) asn1Object.setComponentByPosition( idx, component, @@ -910,12 +985,8 @@ class UniversalConstructedTypeDecoder(AbstractConstructedDecoder): idx += 1 - else: - raise error.SubstrateUnderrunError( - 'No EOO seen before substrate ends' - ) - return asn1Object, substrate + return asn1Object class SequenceOrSequenceOfDecoder(UniversalConstructedTypeDecoder): @@ -952,7 +1023,7 @@ class ChoiceDecoder(AbstractConstructedDecoder): tagSet=None, length=None, state=None, decodeFun=None, substrateFun=None, **options): - head, tail = substrate[:length], substrate[length:] + # head = popSubstream(substrate, length) if asn1Spec is None: asn1Object = self.protoComponent.clone(tagSet=tagSet) @@ -967,16 +1038,16 @@ class ChoiceDecoder(AbstractConstructedDecoder): if LOG: LOG('decoding %s as explicitly tagged CHOICE' % (tagSet,)) - component, head = decodeFun( - head, asn1Object.componentTagMap, **options + component = decodeFun( + substrate, asn1Object.componentTagMap, **options ) else: if LOG: LOG('decoding %s as untagged CHOICE' % (tagSet,)) - component, head = decodeFun( - head, asn1Object.componentTagMap, + component = decodeFun( + substrate, asn1Object.componentTagMap, tagSet, length, state, **options ) @@ -992,7 +1063,7 @@ class ChoiceDecoder(AbstractConstructedDecoder): innerFlag=False ) - return asn1Object, tail + return asn1Object def indefLenValueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, @@ -1010,12 +1081,12 @@ class ChoiceDecoder(AbstractConstructedDecoder): if LOG: LOG('decoding %s as explicitly tagged CHOICE' % (tagSet,)) - component, substrate = decodeFun( + component = decodeFun( substrate, asn1Object.componentType.tagMapUnique, **options ) # eat up EOO marker - eooMarker, substrate = decodeFun( + eooMarker = decodeFun( substrate, allowEoo=True, **options ) @@ -1026,7 +1097,7 @@ class ChoiceDecoder(AbstractConstructedDecoder): if LOG: LOG('decoding %s as untagged CHOICE' % (tagSet,)) - component, substrate = decodeFun( + component = decodeFun( substrate, asn1Object.componentType.tagMapUnique, tagSet, length, state, **options ) @@ -1043,7 +1114,7 @@ class ChoiceDecoder(AbstractConstructedDecoder): innerFlag=False ) - return asn1Object, substrate + return asn1Object class AnyDecoder(AbstractSimpleDecoder): @@ -1063,22 +1134,22 @@ class AnyDecoder(AbstractSimpleDecoder): isUntagged = tagSet != asn1Spec.tagSet if isUntagged: - fullSubstrate = options['fullSubstrate'] + fullPosition = substrate._marked_position + currentPosition = substrate.tell() - # untagged Any container, recover inner header substrate - length += len(fullSubstrate) - len(substrate) - substrate = fullSubstrate + substrate.seek(fullPosition, os.SEEK_SET) + length += (currentPosition - fullPosition) if LOG: - LOG('decoding as untagged ANY, substrate %s' % debug.hexdump(substrate)) + LOG('decoding as untagged ANY, substrate %s' % debug.hexdump(peek(substrate, length))) if substrateFun: return substrateFun(self._createComponent(asn1Spec, tagSet, noValue, **options), substrate, length) - head, tail = substrate[:length], substrate[length:] + head = substrate.read(length) - return self._createComponent(asn1Spec, tagSet, head, **options), tail + return self._createComponent(asn1Spec, tagSet, head, **options) def indefLenValueDecoder(self, substrate, asn1Spec, tagSet=None, length=None, state=None, @@ -1101,10 +1172,12 @@ class AnyDecoder(AbstractSimpleDecoder): LOG('decoding as tagged ANY') else: - fullSubstrate = options['fullSubstrate'] + # TODO: Seems not to be tested + fullPosition = substrate._marked_position + currentPosition = substrate.tell() - # untagged Any, recover header substrate - header = fullSubstrate[:-len(substrate)] + substrate.seek(fullPosition, os.SEEK_SET) + header = substrate.read(currentPosition - fullPosition) if LOG: LOG('decoding as untagged ANY, header substrate %s' % debug.hexdump(header)) @@ -1122,25 +1195,24 @@ class AnyDecoder(AbstractSimpleDecoder): # All inner fragments are of the same type, treat them as octet string substrateFun = self.substrateCollector - while substrate: - component, substrate = decodeFun(substrate, asn1Spec, + while True: + component = decodeFun(substrate, asn1Spec, substrateFun=substrateFun, allowEoo=True, **options) if component is eoo.endOfOctets: break + if not component: + raise error.SubstrateUnderrunError( + 'No EOO seen before substrate ends' + ) header += component - else: - raise error.SubstrateUnderrunError( - 'No EOO seen before substrate ends' - ) - if substrateFun: - return header, substrate + return header # TODO: Weird else: - return self._createComponent(asn1Spec, tagSet, header, **options), substrate + return self._createComponent(asn1Spec, tagSet, header, **options) # character string types @@ -1282,16 +1354,19 @@ class Decoder(object): **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))) + LOG('decoder called at scope %s with state %d, working with up to %s octets of substrate: %s' % (debug.scope, state, length, substrate)) allowEoo = options.pop('allowEoo', False) # Look for end-of-octets sentinel if allowEoo and self.supportIndefLength: - if substrate[:2] == self.__eooSentinel: + eoo_candidate = substrate.read(2) + if eoo_candidate == self.__eooSentinel: if LOG: LOG('end-of-octets sentinel found') - return eoo.endOfOctets, substrate[2:] + return eoo.endOfOctets + else: + substrate.seek(-2, os.SEEK_CUR) value = noValue @@ -1300,26 +1375,25 @@ class Decoder(object): tagCache = self.__tagCache tagSetCache = self.__tagSetCache - fullSubstrate = substrate + substrate._marked_position = substrate.tell() 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:] + + firstByte = substrate.read(1) + if not firstByte: + return None + + firstOctet = ord(firstByte) try: lastTag = tagCache[firstOctet] except KeyError: - integerTag = oct2int(firstOctet) + integerTag = firstOctet tagClass = integerTag & 0xC0 tagFormat = integerTag & 0x20 tagId = integerTag & 0x1F @@ -1329,21 +1403,18 @@ class Decoder(object): 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' - ) + while True: + integerByte = substrate.read(1) + if not integerByte: + raise error.SubstrateUnderrunError( + 'Short octet stream on long tag decoding' + ) + integerTag = ord(integerByte) + lengthOctetIdx += 1 + tagId <<= 7 + tagId |= (integerTag & 0x7F) + if not integerTag & 0x80: + break lastTag = tag.Tag( tagClass=tagClass, tagFormat=tagFormat, tagId=tagId @@ -1375,21 +1446,20 @@ class Decoder(object): if state is stDecodeLength: # Decode length - if not substrate: + try: + firstOctet = ord(substrate.read(1)) + except: 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]) + encodedLength = list(substrate.read(size)) # missing check on maximum size, which shouldn't be a # problem, we can handle more than is possible if len(encodedLength) != size: @@ -1400,27 +1470,19 @@ class Decoder(object): length = 0 for lengthOctet in encodedLength: length <<= 8 - length |= lengthOctet + length |= oct2int(lengthOctet) size += 1 - else: - size = 1 + else: # 128 means indefinite 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))) + if length == -1 and not self.supportIndefLength: + raise error.PyAsn1Error('Indefinite length encoding not supported by this codec') state = stGetValueDecoder if LOG: - LOG('value length decoded into %d, payload substrate is: %s' % (length, debug.hexdump(length == -1 and substrate or substrate[:length]))) + LOG('value length decoded into %d' % length) if state is stGetValueDecoder: if asn1Spec is None: @@ -1539,26 +1601,28 @@ class Decoder(object): if not options.get('recursiveFlag', True) and not substrateFun: # deprecate this substrateFun = lambda a, b, c: (a, b[:c]) - options.update(fullSubstrate=fullSubstrate) + original_position = substrate.tell() if length == -1: # indef length - value, substrate = concreteDecoder.indefLenValueDecoder( + value = concreteDecoder.indefLenValueDecoder( substrate, asn1Spec, tagSet, length, stGetValueDecoder, self, substrateFun, **options ) - else: - value, substrate = concreteDecoder.valueDecoder( + value = concreteDecoder.valueDecoder( substrate, asn1Spec, tagSet, length, stGetValueDecoder, self, substrateFun, **options ) + bytes_read = substrate.tell() - original_position + if bytes_read != length: + raise PyAsn1Error("Read %s bytes instead of expected %s." % (bytes_read, length)) 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>')) + LOG('codec %s yields type %s, value:\n%s\n...' % (concreteDecoder.__class__.__name__, value.__class__.__name__, isinstance(value, base.Asn1Item) and value.prettyPrint() or value)) state = stStop break @@ -1595,7 +1659,22 @@ class Decoder(object): debug.scope.pop() LOG('decoder left scope %s, call completed' % debug.scope) - return value, substrate + return value + + +_decode = Decoder(tagMap, typeMap) + + +def decodeStream(substrate, asn1Spec=None, **kwargs): + """Iterator of objects in a substrate.""" + # TODO: This should become `decode` after API-breaking approved + substrate = asSeekableStream(substrate) + while True: + result = _decode(substrate, asn1Spec, **kwargs) + if result is None: + break + yield result + # TODO: Check about eoo.endOfOctets? #: Turns BER octet stream into an ASN.1 object. @@ -1648,7 +1727,13 @@ class Decoder(object): #: SequenceOf: #: 1 2 3 #: -decode = Decoder(tagMap, typeMap) +def decode(substrate, asn1Spec=None, **kwargs): + # TODO: Temporary solution before merging with upstream + # It preserves the original API + substrate = BytesIO(substrate) + iterator = decodeStream(substrate, asn1Spec=asn1Spec, **kwargs) + return next(iterator), substrate.read() + # XXX # non-recursive decoding; return position rather than substrate |