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Matches regex NULL byte

The following display filter works for my purposes, but has lots of false positives: tcp matches "\xff....\xfe"

A better way would be to match two null bytes, like: tcp matches "\xff\x00\x00..\xfe"

But then, since the string/input to matches is a null terminated string, the regex searches only for the \xff byte, the following \x00 ends the string :/

Is there any way i didn't thought of to include null bytes in the regex? Tried it with \0 and \000. Maybe some sort of (undocumented) special escape char?

Btw. tcp contains ff:00... doesn't work for me because i need the regex power of matching 2 "dont care" bytes (but dontcare/wildcard for contains would be nice tho too ^^)

matches regex null

asked 06 Apr '15, 14:40

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One Answer:

Ok got it ;-) While it might be really usefull that Wireshark would not use NULL terminated c-strings (for a software that deals mostly with BINARY data and not text...), there is a simple solution:

[^\x01-\xFF] matches a null byte

Instead of tcp matches "\xff\x00\x00..\xfe" which wont work as intended,

use: tcp matches "\xff[^\x01-\xFF]{2}..\xfe"

answered 08 Apr '15, 16:10

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