customizing to_asn1 output

[dbressan2]

Hi

I would like to know the best way to change the look of to_asn1 output for various objects. I tried to modify the code in pycrate_asn1/asnobj.py. Let us take an example

Say I want to print the TIME_UTC output as YYMMDDHHMMSSUTC instead of YYMMDDHHMMSSZ.

Is it enough to modify TIME_UTC code ? Do we need to re-build package afterwards ?

class TIME_UTC(_Time): doc = """ ASN.1 basic type UTCTime object

single value: Python 7-tuple of int (AA, MM, DD, HH, MM, [SS,] Z),
    SS is optional, hence 6th element can be None
    Z corresponds to the UTC decay

%s
""" % ASN1Obj_docstring

TYPE  = TYPE_TIME_UTC
TAG   = 23
_type = TYPE

def _to_asn1(self, val):
    # to be applied to an internal single value `val' to get 
    # an ASN.1 compliant value
    ret = '%.2i%.2i%.2i%.2i%.2i' % val[:5]
    if val[5] is not None:
        ret += '%.2i' % val[5]
    if val[6] == 0:
        ret += 'Z'
    elif val[6] > 0:
        ret += '+%.4i' % val[6]
    else:
        ret += '%.4i' % val[6]
    return ret

Thank you in advance

[p1-bmu]

As soon as you patch a file of the library, the change will be effective as soon as you load it (e.g. in case you use only a local version from your $HOME, or you installed with setup.py install develop): no need for re-packaging. This is one of the advantage of Python.

Regarding the modification of the generic to_asn1() in asnobj.py, or the various _to_asn1() methods, this will change the formatting of the output for sure. On the other side, to_asn1() is made to produce ASN.1-compliant syntax and formatting (its output could be ingested by some other ASN.1 tools), it may not be the case anymore if you change those methods.

[dbressan2]

Thank you for your quick reply

I am trying to modify the code in pycrate_asn1rt/asnobjcontruct.py

The goal is systematically number items within a list.

def _to_asn1(self):
    if not self._val:
        # empty dict
        return '{ }'
    else:
        val = []
        # root and ext part in 1 shot
        # WNG: we are not ordering SET root components in canonical order
        for ident in self._cont:
            if ident in self._val:
                print ("ident = {0}".format(ident))
                _par = self._cont[ident]._parent
                self._cont[ident]._parent = self
                self._cont[ident]._val = self._val[ident]
                print ('  %s %s,\n' % (ident, self._cont[ident]._to_asn1().replace('\n', '\n  ')))
                val.append('  %s %s,\n' % (ident, self._cont[ident]._to_asn1().replace('\n', '\n  ')))
                self._cont[ident]._parent = _par
        if val:
            val[-1] = val[-1][:-2]
        return '{\n' + ''.join(val) + '\n}'

If we take the example of an NR RRC DL-DCCH message

Message = 00 0c 02 48 20 08 44 02 92 48 00 30 00 0a 24 00 18 00 02 12 42 94 0a 10 84 1c 6b 80 80 9c 08 00 00 3d 06 24 30 54 06 e0 40 00 01 e8 31 26 82 a5 05 28 14 21 08 38 d7 01 01 38 10 00 00 7a 0c 48 60 a8 0d c0 80 00 03 d0 62 4d 05 40 00

In blue, the decoding as it is right now after invoking to_asn1 method, in red what I would like to add in a systematic way, without having to delve into each message with get_at() or get_val_at() methods. Is there a simple modification of _to_asn1 that may achieve the item numbering ?

{ message c1 : rrcReconfiguration : { rrc-TransactionIdentifier 0, criticalExtensions rrcReconfiguration : { nonCriticalExtension { masterCellGroup CellGroupConfig: { cellGroupId 0, spCellConfig { spCellConfigDedicated { downlinkBWP-ToAddModList { { Item 0 bwp-Id 1, bwp-Dedicated { pdsch-Config setup : { resourceAllocation resourceAllocationType0, rbg-Size config1, mcs-Table qam256, maxNrofCodeWordsScheduledByDCI n1, prb-BundlingType staticBundling : { } } } }, { Item 1 bwp-Id 2, bwp-Dedicated { pdsch-Config setup : { resourceAllocation resourceAllocationType0, rbg-Size config1, mcs-Table qam256, maxNrofCodeWordsScheduledByDCI n1, prb-BundlingType staticBundling : { } } } } }, uplinkConfig { uplinkBWP-ToAddModList { { Item 0 bwp-Id 1, bwp-Dedicated { srs-Config setup : { srs-ResourceSetToAddModList { Item 0 { srs-ResourceSetId 2, srs-ResourceIdList { 2, 3 }, resourceType periodic : { }, usage antennaSwitching, p0 -110 } }, srs-ResourceToAddModList { { Item 0 srs-ResourceId 2, nrofSRS-Ports ports2, transmissionComb n4 : { combOffset-n4 2, cyclicShift-n4 0 }, resourceMapping { startPosition 2, nrofSymbols n1, repetitionFactor n1 }, freqDomainPosition 0, freqDomainShift 0, freqHopping { c-SRS 61, b-SRS 0, b-hop 0 }, groupOrSequenceHopping groupHopping, resourceType periodic : { periodicityAndOffset-p sl40 : 3 }, sequenceId 21 }, { Item 1 srs-ResourceId 3, nrofSRS-Ports ports2, transmissionComb n4 : { combOffset-n4 2, cyclicShift-n4 0 }, resourceMapping { startPosition 2, nrofSymbols n1, repetitionFactor n1 }, freqDomainPosition 0, freqDomainShift 0, freqHopping { c-SRS 61, b-SRS 0, b-hop 0 }, groupOrSequenceHopping groupHopping, resourceType periodic : { periodicityAndOffset-p sl40 : 13 }, sequenceId 21 } } } } }, { Item 1 bwp-Id 2, bwp-Dedicated { srs-Config setup : { srs-ResourceSetToAddModList { Item 0 { srs-ResourceSetId 2, srs-ResourceIdList { 2, 3 }, resourceType periodic : { }, usage antennaSwitching, p0 -110 } }, srs-ResourceToAddModList { { Item 0 srs-ResourceId 2, nrofSRS-Ports ports2, transmissionComb n4 : { combOffset-n4 2, cyclicShift-n4 0 }, resourceMapping { startPosition 2, nrofSymbols n1, repetitionFactor n1 }, freqDomainPosition 0, freqDomainShift 0, freqHopping { c-SRS 61, b-SRS 0, b-hop 0 }, groupOrSequenceHopping groupHopping, resourceType periodic : { periodicityAndOffset-p sl40 : 3 }, sequenceId 21 }, { Item 1 srs-ResourceId 3, nrofSRS-Ports ports2, transmissionComb n4 : { combOffset-n4 2, cyclicShift-n4 0 }, resourceMapping { startPosition 2, nrofSymbols n1, repetitionFactor n1 }, freqDomainPosition 0, freqDomainShift 0, freqHopping { c-SRS 61, b-SRS 0, b-hop 0 }, groupOrSequenceHopping groupHopping, resourceType periodic : { periodicityAndOffset-p sl40 : 13 }, sequenceId 21 } } } } } } }, tag-Id 0, servingCellMO 1 } } } } } } }

Thank you in advance

Best regards

Dominique

From: Benoit Michau @.> Sent: Monday, April 4, 2022 12:04 PM To: P1sec/pycrate @.> Cc: Dominique Bressanelli @.>; Author @.> Subject: Re: [P1sec/pycrate] customizing to_asn1 output (Issue #186)

WARNING: This email originated from outside of Qualcomm. Please be wary of any links or attachments, and do not enable macros.

As soon as you patch a file of the library, the change will be effective as soon as you load it (e.g. in case you use only a local version from your $HOME, or you installed with setup.py install develop): no need for re-packaging. This is one of the advantage of Python.

Regarding the modification of the generic to_asn1() in asnobj.py, or the various _to_asn1() methods, this will change the formatting of the output for sure. On the other side, to_asn1() is made to produce ASN.1-compliant syntax and formatting (its output could be ingested by some other ASN.1 tools), it may not be the case anymore if you change those methods.

— Reply to this email directly, view it on GitHubhttps://github.com/P1sec/pycrate/issues/186#issuecomment-1087357281, or unsubscribehttps://github.com/notifications/unsubscribe-auth/AHUUMPNFIK6X7AOUH6ZS2BTVDK5ANANCNFSM5SO6BQ7Q. You are receiving this because you authored the thread.Message ID: @.**@.>>

[p1-bmu]

I don't really understand what / how you want to number items. I see no colour in your provided description, sorry.

[dbressan2]

Hi

What I wish to add is highlighted below with the mark “<=== to be added”

{ message c1 : rrcReconfiguration : { rrc-TransactionIdentifier 0, criticalExtensions rrcReconfiguration : { nonCriticalExtension { masterCellGroup CellGroupConfig: { cellGroupId 0, spCellConfig { spCellConfigDedicated { downlinkBWP-ToAddModList { { Item 0 <=== to be added bwp-Id 1, bwp-Dedicated { pdsch-Config setup : { resourceAllocation resourceAllocationType0, rbg-Size config1, mcs-Table qam256, maxNrofCodeWordsScheduledByDCI n1, prb-BundlingType staticBundling : { } } } }, { Item 1 <=== to be added bwp-Id 2, bwp-Dedicated { pdsch-Config setup : { resourceAllocation resourceAllocationType0, rbg-Size config1, mcs-Table qam256, maxNrofCodeWordsScheduledByDCI n1, prb-BundlingType staticBundling : { } } } } }, uplinkConfig { uplinkBWP-ToAddModList { { Item 0 <=== to be added bwp-Id 1, bwp-Dedicated { srs-Config setup : { srs-ResourceSetToAddModList { Item 0 <=== to be added { srs-ResourceSetId 2, srs-ResourceIdList { 2, 3 }, resourceType periodic : { }, usage antennaSwitching, p0 -110 } }, srs-ResourceToAddModList { { Item 0 <=== to be added srs-ResourceId 2, nrofSRS-Ports ports2, transmissionComb n4 : { combOffset-n4 2, cyclicShift-n4 0 }, resourceMapping { startPosition 2, nrofSymbols n1, repetitionFactor n1 }, freqDomainPosition 0, freqDomainShift 0, freqHopping { c-SRS 61, b-SRS 0, b-hop 0 }, groupOrSequenceHopping groupHopping, resourceType periodic : { periodicityAndOffset-p sl40 : 3 }, sequenceId 21 }, { Item 1 <=== to be added srs-ResourceId 3, nrofSRS-Ports ports2, transmissionComb n4 : { combOffset-n4 2, cyclicShift-n4 0 }, resourceMapping { startPosition 2, nrofSymbols n1, repetitionFactor n1 }, freqDomainPosition 0, freqDomainShift 0, freqHopping { c-SRS 61, b-SRS 0, b-hop 0 }, groupOrSequenceHopping groupHopping, resourceType periodic : { periodicityAndOffset-p sl40 : 13 }, sequenceId 21 } } } } }, { Item 1 <=== to be added bwp-Id 2, bwp-Dedicated { srs-Config setup : { srs-ResourceSetToAddModList { Item 0 <=== to be added { srs-ResourceSetId 2, srs-ResourceIdList { 2, 3 }, resourceType periodic : { }, usage antennaSwitching, p0 -110 } }, srs-ResourceToAddModList { { Item 0 <=== to be added srs-ResourceId 2, nrofSRS-Ports ports2, transmissionComb n4 : { combOffset-n4 2, cyclicShift-n4 0 }, resourceMapping { startPosition 2, nrofSymbols n1, repetitionFactor n1 }, freqDomainPosition 0, freqDomainShift 0, freqHopping { c-SRS 61, b-SRS 0, b-hop 0 }, groupOrSequenceHopping groupHopping, resourceType periodic : { periodicityAndOffset-p sl40 : 3 }, sequenceId 21 }, { Item 1 <=== to be added srs-ResourceId 3, nrofSRS-Ports ports2, transmissionComb n4 : { combOffset-n4 2, cyclicShift-n4 0 }, resourceMapping { startPosition 2, nrofSymbols n1, repetitionFactor n1 }, freqDomainPosition 0, freqDomainShift 0, freqHopping { c-SRS 61, b-SRS 0, b-hop 0 }, groupOrSequenceHopping groupHopping, resourceType periodic : { periodicityAndOffset-p sl40 : 13 }, sequenceId 21 } } } } } } }, tag-Id 0, servingCellMO 1 } } } } } } }

Thank you very much for your help

Best regards

Dominique

From: Benoit Michau @.> Sent: Monday, April 11, 2022 9:54 AM To: P1sec/pycrate @.> Cc: Dominique Bressanelli @.>; Author @.> Subject: Re: [P1sec/pycrate] customizing to_asn1 output (Issue #186)

WARNING: This email originated from outside of Qualcomm. Please be wary of any links or attachments, and do not enable macros.

I don't really understand what / how you want to number items. I see no colour in your provided description, sorry.

— Reply to this email directly, view it on GitHubhttps://github.com/P1sec/pycrate/issues/186#issuecomment-1094669380, or unsubscribehttps://github.com/notifications/unsubscribe-auth/AHUUMPKSQUWGMWTRFLFGYBLVEPLB5ANCNFSM5SO6BQ7Q. You are receiving this because you authored the thread.Message ID: @.**@.>>

[p1-bmu]

You can modify the _to_asn1() method of the _CONSTRUCT_OF class here: https://github.com/P1sec/pycrate/blob/1a6d4d6ab8b61e0ef4ea9314ac07facfdd10f785/pycrate_asn1rt/asnobj_construct.py#L2686 To have a pattern like this instead:

            for i, v in enumerate(self._val):
                self._cont._val = v
                val.append('  -- _item_ %i --\n  %s,\n' % (i, self._cont._to_asn1().replace('\n', '\n  ')))

I guess such generated ASN.1 syntax won't be re-encodable with pycrate, as its runtime does not strip ASN.1 comments out.

[dbressan2]

Thank you so much, this is exactly what I was looking for.

Yes, I understand the limitation about the ASN.1 syntax not being re-encodable. However this is not blocking to me

Best regards

Dominique

From: Benoit Michau @.> Sent: Tuesday, April 26, 2022 3:05 PM To: P1sec/pycrate @.> Cc: Dominique Bressanelli @.>; Author @.> Subject: Re: [P1sec/pycrate] customizing to_asn1 output (Issue #186)

WARNING: This email originated from outside of Qualcomm. Please be wary of any links or attachments, and do not enable macros.

You can modify the _to_asn1() method of the _CONSTRUCT_OF class here: https://github.com/P1sec/pycrate/blob/1a6d4d6ab8b61e0ef4ea9314ac07facfdd10f785/pycrate_asn1rt/asnobj_construct.py#L2686 To have a pattern like this instead:

        for i, v in enumerate(self._val):

            self._cont._val = v

            val.append('  -- _item_ %i --\n  %s,\n' % (i, self._cont._to_asn1().replace('\n', '\n  ')))

I guess such generated ASN.1 syntax won't be re-encodable with pycrate, as its runtime does not strip ASN.1 comments out.

— Reply to this email directly, view it on GitHubhttps://github.com/P1sec/pycrate/issues/186#issuecomment-1109772794, or unsubscribehttps://github.com/notifications/unsubscribe-auth/AHUUMPK2ORIFZB4IJZKQIX3VG7SZHANCNFSM5SO6BQ7Q. You are receiving this because you authored the thread.Message ID: @.**@.>>