ASN.1 error with bit string and no option selected

[KenWhitesell]

Sample asn.1 file (greatly reduced from J2735):

DSRC DEFINITIONS AUTOMATIC TAGS::= BEGIN 

Lane ::= SEQUENCE {
   directionalUse  LaneDirection
   }

LaneDirection ::= BIT STRING {
   ingressPath     (0), 
   egressPath      (1)
   }

END

This asn text compiles and works fine: { directionalUse {ingressPath} }

This text { directionalUse {} } generates this error:

Traceback (most recent call last):
  File "/opt/data/tskww/.ve/py38/lib/python3.8/site-packages/pycrate-0.4-py3.8.egg/pycrate_asn1rt/asnobj_construct.py", line 1205, in _from_asn1
    t_ident, t_rest = txt.split(' ', 1)
ValueError: not enough values to unpack (expected 2, got 1)

[p1-bmu]

Could you please provide the complete textual definition you try to compile ? So that I can reproduce exactly your issue.

[KenWhitesell]

I've attached a file which is a terminal session walking through the complete set of steps to recreate the problem identified here. Please let me know if you have any questions or need any further information.

Xterm.log.tskww-HP-2.txt

[p1-bmu]

OK, thanks. This is related to passing ASN.1 BIT STRING values as named offsets. Here, the bug is that an empty set of offsets is not accepted by the runtime. A patch should be done somewhere here: https://github.com/P1sec/pycrate/blob/5e7406d99346c2130b0e01f23c7c39a4756e857b/pycrate_asn1rt/asnobj_str.py#L223 When setting the BIT STRING value from the named offsets, we should also take care to set a correct bit length according to any potential SIZE constraint.

I will work on it when I have some time, maybe next week or so.

[p1-bmu]

This commit should solve the issue: https://github.com/P1sec/pycrate/commit/afc9849c4c895ef8924c7c9dc77d0274bc6e735b

[KenWhitesell]

Fantastic This commit addresses both issues I reported, and now allows me to encode/decode UPER-encoded J2735 TIM MessageFrames. (At least my three test cases.) Thank you!