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') # Get the first subid subId = oct2int(head[0]) oid = divmod(subId, 40) index = 1 substrateLen = len(head) while index < substrateLen: subId = oct2int(head[index]) index = index + 1 if subId == 128: # ASN.1 spec forbids leading zeros (0x80) in sub-ID OID # encoding, tolerating it opens a vulnerability. # See http://www.cosic.esat.kuleuven.be/publications/article-1432.pdf page 7 raise error.PyAsn1Error('Invalid leading 0x80 in sub-OID') 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 = index + 1 subId = (subId << 7) + nextSubId oid = oid + (subId,) return self._createComponent(asn1Spec, tagSet, oid), tail
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 = b + ((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) r = r + component return r, tail
def valueDecoder(self, fullSubstrate, substrate, asn1Spec, tagSet, length, state, decodeFun, substrateFun): head, tail = substrate[:length], substrate[length:] if not head: raise error.SubstrateUnderrunError('Short substrate for Real') fo = oct2int(head[0]); head = head[1:] if fo & 0x40: # infinite value value = fo & 0x01 and '-inf' or 'inf' elif fo & 0x80: # binary enoding n = (fo & 0x03) + 1 if n == 4: n = oct2int(head[0]) 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:] p = 0 while head: # value p <<= 8 p |= oct2int(head[0]) head = head[1:] if fo & 0x40: # sign bit p = -p value = (p, 2, e) elif fo & 0xc0 == 0: # character encoding 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' ) elif fo & 0xc0 == 0x40: # special real value pass else: raise error.SubstrateUnderrunError( 'Unknown encoding (tag %s)' % fo ) return self._createComponent(asn1Spec, tagSet, value), tail
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') 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
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') byte = oct2int(head[0]) # CER/DER specifies encoding of TRUE as 0xFF and FALSE as 0x0, while # BER allows any non-zero value as TRUE; cf. sections 8.2.2. and 11.1 # in http://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf if byte == 0xff: value = 1 elif byte == 0x00: value = 0 else: raise error.PyAsn1Error('Boolean CER violation: %s' % byte) return self._createComponent(asn1Spec, tagSet, value), tail
def encodeValue(self, encodeFun, value, defMode, maxChunkSize): if value.isPlusInfinity(): return int2oct(0x40), 0 if value.isMinusInfinity(): return int2oct(0x41), 0 m, b, e = value if not m: return null, 0 if b == 10: return str2octs('\x03%dE%s%d' % (m, e == 0 and '+' or '', e)), 0 elif b == 2: fo = 0x80 # binary enoding if m < 0: fo = fo | 0x40 # sign bit m = -m while int(m) != m: # drop floating point m *= 2 e -= 1 while m & 0x1 == 0: # mantissa normalization m >>= 1 e += 1 eo = null while e not in (0, -1): eo = int2oct(e&0xff) + eo e >>= 8 if e == 0 and eo and oct2int(eo[0]) & 0x80: eo = int2oct(0) + eo n = len(eo) if n > 0xff: raise error.PyAsn1Error('Real exponent overflow') if n == 1: pass elif n == 2: fo |= 1 elif n == 3: fo |= 2 else: fo |= 3 eo = int2oct(n//0xff+1) + eo po = null while m: po = int2oct(m&0xff) + po m >>= 8 substrate = int2oct(fo) + eo + po return substrate, 0 else: raise error.PyAsn1Error('Prohibited Real base %s' % b)
def encodeValue(self, encodeFun, value, defMode, maxChunkSize): if value.isPlusInfinity(): return int2oct(0x40), 0 if value.isMinusInfinity(): return int2oct(0x41), 0 m, b, e = value if not m: return null, 0 if b == 10: return str2octs('\x03%dE%s%d' % (m, e == 0 and '+' or '', e)), 0 elif b == 2: fo = 0x80 # binary enoding if m < 0: fo = fo | 0x40 # sign bit m = -m while int(m) != m: # drop floating point m *= 2 e -= 1 while m & 0x1 == 0: # mantissa normalization m >>= 1 e += 1 eo = null while e not in (0, -1): eo = int2oct(e & 0xff) + eo e >>= 8 if e == 0 and eo and oct2int(eo[0]) & 0x80: eo = int2oct(0) + eo n = len(eo) if n > 0xff: raise error.PyAsn1Error('Real exponent overflow') if n == 1: pass elif n == 2: fo |= 1 elif n == 3: fo |= 2 else: fo |= 3 eo = int2oct(n // 0xff + 1) + eo po = null while m: po = int2oct(m & 0xff) + po m >>= 8 substrate = int2oct(fo) + eo + po return substrate, 0 else: raise error.PyAsn1Error('Prohibited Real base %s' % b)
def __call__(self, substrate, asn1Spec=None, tagSet=None, length=None, state=stDecodeTag, recursiveFlag=1, substrateFun=None): 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: # Decode tag 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') firstOctet = substrate[0] substrate = substrate[1:] if firstOctet in self.__tagCache: lastTag = self.__tagCache[firstOctet] else: t = oct2int(firstOctet) 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 %r, 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)) ) state = stGetValueDecoder debug.logger and debug.logger & debug.flagDecoder and debug.logger('value length decoded into %d, payload substrate is: %s' % (length, debug.hexdump(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(' %r -> %s' % (t, v.__class__.__name__)) if asn1Spec.getNegMap(): debug.logger('but neither of: ') for i in asn1Spec.getNegMap().items(): debug.logger(' %r -> %s' % (t, v.__class__.__name__)) debug.logger('new candidate ASN.1 spec is %s, chosen by %r' % (__chosenSpec is None and '<none>' or __chosenSpec.__class__.__name__, 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 %r' % (baseTagSet,)) else: concreteDecoder = None if concreteDecoder: asn1Spec = __chosenSpec state = stDecodeValue else: state = stTryAsExplicitTag elif tagSet == self.__endOfOctetsTagSet: concreteDecoder = self.__tagMap[tagSet] state = stDecodeValue debug.logger and debug.logger & debug.flagDecoder and debug.logger('end-of-octets found') 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( '%r not in asn1Spec: %r' % (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