Re: [pyasn1-users] SubstrateUnderrunError with roundtrip encode/decode.

[Ilya E. <il...@gl...>]

Hi Paul,

That also looks like a bug in CHOICE decoder whenever indefinite length mode is used. It's hopefully fixed at CVS so please
give it a try:

http://pyasn1.cvs.sourceforge.net/viewvc/pyasn1/pyasn1/?view=tar

Please alert me in case of any issues.

-ilya

On Jan 21, 2013, at 2:48 PM, paul sorenson wrote:

> When I run the attached file everything seems to be decoded ok but the decoder throws a SubstrateUnderrunError apparently encountering a spurious "00" on the end of the substrate.  It only manifested when I added the OriginHost field.
> 
> Not sure if it is a bug in my specification/code or elsewhere.  Any help would be appreciated.
> 
> Stacktrace:
> 
> ...remaining substrate is:
> 00000: 00 00 00
> DBG: decoder left scope CDR.OriginHost, call completed
> DBG: codec ChoiceDecoder yields type OriginHost, value:
> OriginHost:
> domainName=my.domain
> 
> ...remaining substrate is:
> 00000: 00
> DBG: decoder left scope CDR, call completed
> DBG: decoder called at scope CDR with state 0, working with up to 1 octets of substrate:
> 00000: 00
> DBG: tag decoded into TagSet(Tag(tagClass=0, tagFormat=0, tagId=0)), decoding length
> ERROR:root:decode failure.
> Traceback (most recent call last):
>  File "foo.py", line 136, in main
>    asn1 = decoder.decode(ber, asn1Spec = spec)
>  File "/home/pms/src/C-IMS/src/pyasn1/codec/ber/decoder.py", line 752, in __call__
>    stGetValueDecoder, self, substrateFun
>  File "/home/pms/src/C-IMS/src/pyasn1/codec/ber/decoder.py", line 329, in indefLenValueDecoder
>    component, substrate = decodeFun(substrate, asn1Spec)
>  File "/home/pms/src/C-IMS/src/pyasn1/codec/ber/decoder.py", line 610, in __call__
>    'Short octet stream on length decoding'
> SubstrateUnderrunError: Short octet stream on length decoding
> 
> 
> Code:
> 
> import sys
> import logging
> from pyasn1.type import tag, char, univ, namedtype, namedval, constraint
> from pyasn1.codec.ber import encoder, decoder
> from pyasn1 import debug
> 
> 
> RECORD_TYPE = 83
> 
> class iPBinV4Address(univ.OctetString):
>    subtypeSpec = constraint.ValueSizeConstraint(4, 4)
> 
> 
> class iPBinV6Address(univ.OctetString):
>    subtypeSpec = constraint.ValueSizeConstraint(16, 16)
> 
> 
> class IPBinaryAddress(univ.Choice):
>    componentType = namedtype.NamedTypes(
>            namedtype.NamedType('iPBinV4Address',
>                    iPBinV4Address().subtype(
>                            implicitTag = tag.Tag(tag.tagClassContext,
>                            tag.tagFormatSimple, 0))),
>            namedtype.NamedType('iPBinV6Address',
>                    iPBinV6Address().subtype(
>                    implicitTag = tag.Tag(tag.tagClassContext,
>                            tag.tagFormatSimple, 1))))
> 
> 
> class iPTextV4Address(char.IA5String):
>    subtypeSpec = constraint.ValueSizeConstraint(7, 15)
> 
> 
> class iPTextV6Address(char.IA5String):
>    subtypeSpec = constraint.ValueSizeConstraint(15, 45)
> 
> 
> class IPTextRepresentedAddress(univ.Choice):
>    componentType = namedtype.NamedTypes(
>            namedtype.NamedType('iPTextV4Address',
>                    iPTextV4Address().subtype(
>                            implicitTag = tag.Tag(tag.tagClassContext,
>                            tag.tagFormatSimple, 3))),
>            namedtype.NamedType('iPTextV6Address',
>                    iPTextV6Address().subtype(
>                    implicitTag = tag.Tag(tag.tagClassContext,
>                            tag.tagFormatSimple, 4))))
> 
> 
> class IPAddress(univ.Choice):
>    componentType = namedtype.NamedTypes(
>            namedtype.NamedType('iPBinaryddress',
>                    IPBinaryAddress().subtype(
>                            implicitTag = tag.Tag(tag.tagClassContext,
>                            tag.tagFormatSimple, 3))),
>            namedtype.NamedType('iPTextRepresentedAddress',
>                    IPTextRepresentedAddress().subtype(
>                    implicitTag = tag.Tag(tag.tagClassContext,
>                            tag.tagFormatSimple, 4))))
> 
> 
> class OriginHost(univ.Choice):
>    tagSet = univ.Choice.tagSet.tagImplicitly(
>            tag.Tag(tag.tagClassContext,
>                    tag.tagFormatSimple, 4))
> 
>    componentType = namedtype.NamedTypes(
>            namedtype.NamedType('iPAddress', IPAddress().subtype(
>                    implicitTag = tag.Tag(tag.tagClassContext,
>                            tag.tagFormatSimple, 0))),
>            namedtype.NamedType('domainName', char.GraphicString().subtype(
>                    implicitTag = tag.Tag(tag.tagClassContext,
>                            tag.tagFormatSimple, 1))))
> 
> 
> class CDR(univ.Set):
> 
>    tagSet = univ.Sequence.tagSet.tagImplicitly(
>            tag.Tag(tag.tagClassContext,
>                    tag.tagFormatSimple, RECORD_TYPE))
> 
>    componentType = namedtype.NamedTypes(
> 
>        namedtype.NamedType('recordType',
>                univ.Integer().subtype(
>                        implicitTag = tag.Tag(tag.tagClassContext,
>                                tag.tagFormatSimple, 0))),
> 
>        namedtype.NamedType('sipMethod',
>                char.GraphicString().subtype(
>                        implicitTag = tag.Tag(tag.tagClassContext,
>                                tag.tagFormatSimple, 2))),
> 
>        namedtype.NamedType('roleOfNode',
>                univ.Enumerated().subtype(
>                        implicitTag = tag.Tag(tag.tagClassContext,
>                                tag.tagFormatSimple, 3),
>                        namedValues = namedval.NamedValues(
>                                ('originating', 0),
>                                ('terminating', 1),
>                                ('proxy', 2),
>                                ('b2bua', 3)
>                        ),
>                        subtypeSpec = univ.Enumerated.subtypeSpec +
> constraint.SingleValueConstraint(0, 1, 2, 3))),
> 
>        namedtype.NamedType('originHost', OriginHost())
>    )
> 
> 
> def init(cdr):
>    '''
>    Initialise fields of a CDR object.
> 
>    :param cdr: CDR instance.
> 
>    :return: CDR instance with fields initialised.
>    '''
>    cdr.setComponentByName('recordType', RECORD_TYPE)
>    cdr.setComponentByName('sipMethod', 'BYE')
>    cdr.setComponentByName('roleOfNode', 'terminating')
>    originHost = OriginHost()
>    originHost.setComponentByName('domainName', 'my.domain')
>    cdr.setComponentByName('originHost', originHost)
>    return cdr
> 
> 
> def main():
>    debug.setLogger(debug.Debug('all'))
>    cdr = CDR()
>    asn1 = init(cdr)
>    ber = encoder.encode(asn1, defMode = False)
>    spec = CDR()
>    try:
>        asn1 = decoder.decode(ber, asn1Spec = spec)
>    except:
>        logging.exception('decode failure.')
> 
> if __name__ == '__main__':
>    main()
> 
> 
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