Wireshark-bugs: [Wireshark-bugs] [Bug 1989] Don't stop dissection at malformed ASN.1 BER CHOICE
http://bugs.wireshark.org/bugzilla/show_bug.cgi?id=1989
------- Comment #5 from wireshark@xxxxxxx 2007-11-19 15:54 GMT -------
Hmmm - seems I was not exact enough in researching and describing the problem,
sorry for that. I looked around and found that the length of the EXPLICIT
tagging of a chosen element must not be zero since the value that follows the
lenght would contain the actual chosen element. This would at least consist of
the Type and the Lenght which makes the lengh of the explicit tagging >= 2.
It looks like it is possible that a CHOICE is encoded as "the same as the
encoding of a value of the chosen type" - in case it can be IMPLICITly encoded
because there is only a single element of this type in the CHOICE. In this case
e.g. an zero length string would be encoded with zero length.
I'm not familiar enough with packet-ber to find the exact point where we could
catch an explicit tagging with zero length and no encapsulated TLV.
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