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Christian Kreibich

A Framework for Packet Trace Manipulation. Christian Kreibich. Motivation. Say you need to solve a problem that involves manipulating network traffic: complex filtering (e.g. data analysis) fine-grained editing (e.g. header field bitflips) large-scale editing (e.g. anonymization)

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Christian Kreibich

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  1. A Framework for Packet Trace Manipulation Christian Kreibich christian.kreibich@cl.cam.ac.uk

  2. Motivation • Say you need to solve a problem that involves manipulating network traffic: • complex filtering (e.g. data analysis) • fine-grained editing (e.g. header field bitflips) • large-scale editing (e.g. anonymization) • visualization (e.g. behavioural analysis) • What do you do?

  3. Motivation II • Find a tool that does it • where? does it build? maintained? • If so, lucky you!

  4. Motivation II • Find a tool that does it • where? does it build? maintained? • If so, lucky you! • Mhmm ... write your own. • Okay, pcap. • Now you typically need infrastructure: • data types conn.state tracking protocol header lookup • Lots of duplicated effort • Cut’n’paste is bad

  5. Motivation III • Current practice:

  6. Introducing ... • Netdude — NETwork DUmp Data Editor • Framework for packet inspection and manipulation • Multiple usage paradigms: GUI + command line • Scales to arbitrary trace sizes • Reusable at all levels • Extensible

  7. Architecture

  8. Architecture

  9. Architecture

  10. libpcapnav • Enables random packet access • Jump to arbitrary timestamps and fractional offsets • Thin wrapper around pcap • Based on Vern Paxson‘s tcpslice tool • Uses heuristics to get in sync with packet stream • Slightly more robust algorithm • Harder to fool  Tolerates packets not in temporal order • Nasty accidental test case: trace of NFS-copied trace

  11. Architecture

  12. libnetdude • Packet manipulation back-end • Transparent handling of arbitrarily large traces • High-level data types • Extensible through plugin mechanism • connection tables, flow demuxer, flow reassembly, TCP connection filter, importers/exporters,... • Structured packet content: easy header access, protocol plugins provide the knowledge • Provides per-packet tcpdump output • Observer/observee API to be informed of updates

  13. Area 1 Area 3 Area 2 1 2 3 n-1 n Handling big trace files • Always limit the number of packets in memory • Can‘t just mmap() if you want to insert/delete • Edit at granularity of trace areas — libpcapnav helps • Modified trace areas become layered trace parts

  14. Handling big trace files • Always limit the number of packets in memory • Can‘t just mmap() if you want to insert/delete • Edit at granularity of trace areas — libpcapnav helps • Modified trace areas become layered trace parts

  15. Handling big trace files • Always limit the number of packets in memory • Can‘t just mmap() if you want to insert/delete • Edit at granularity of trace areas — libpcapnav helps • Modified trace areas become layered trace parts

  16. Handling big trace files II • Always limit the number of packets in memory • Can‘t just mmap() if you want to insert/delete • Edit at granularity of trace areas — libpcapnav helps • Modified trace areas become layered trace parts

  17. Handling big trace files II • Always limit the number of packets in memory • Can‘t just mmap() if you want to insert/delete • Edit at granularity of trace areas — libpcapnav helps • Modified trace areas become layered trace parts

  18. Handling big trace files II • Always limit the number of packets in memory • Can‘t just mmap() if you want to insert/delete • Edit at granularity of trace areas — libpcapnav helps • Modified trace areas become layered trace parts

  19. Handling big trace files II • Always limit the number of packets in memory • Can‘t just mmap() if you want to insert/delete • Edit at granularity of trace areas — libpcapnav helps • Modified trace areas become layered trace parts

  20. Handling big trace files III • Always limit the number of packets in memory • Can‘t just mmap() if you want to insert/delete • Edit at granularity of trace areas — libpcapnav helps • Modified trace areas become layered trace parts

  21. Handling big trace files III • Always limit the number of packets in memory • Can‘t just mmap() if you want to insert/delete • Edit at granularity of trace areas — libpcapnav helps • Modified trace areas become layered trace parts

  22. Handling big trace files III • Always limit the number of packets in memory • Can‘t just mmap() if you want to insert/delete • Edit at granularity of trace areas — libpcapnav helps • Modified trace areas become layered trace parts

  23. Handling big trace files III • Always limit the number of packets in memory • Can‘t just mmap() if you want to insert/delete • Edit at granularity of trace areas — libpcapnav helps • Modified trace areas become layered trace parts

  24. Architecture

  25. Netdude GUI • GTK-based front-end to libnetdude (sorry Matthias :-) • Extensible through protocol and feature plugins • Protocol plugins visualize header content • Feature plugins can essentially do anything • Uses libnetdude‘s observer API to update GUI

  26. Demo • Fingers crossed, please.

  27. Experience • Fine-grained header field modifications: • M. Handley, C. Kreibich, V. Paxson: Network Intrusion Detection: Evasion, Traffic Normalization, and End-to-End Protocol Semantics, 9th USENIX Security Symposium, 2001 • Large-scale filtering and reassembly: • A. Moore, J. Hall, C. Kreibich, E. Harris, I. Pratt: Architecture of a Network Monitor, PAM Workshop, 2003 • Fine-grained payload editing: • C. Kreibich, J. Crowcroft: Honeycomb - Creating Intrusion Detection Signatures Using Honeypots, HotNets II, 2003

  28. Future Work Progress Chart Visual interpretation 0 1 Perceived length (normalized)

  29. Future Work Progress Chart Visual interpretation 0 1 Perceived length (normalized)

  30. Future Work Progress Chart Visual interpretation 0 1 Perceived length (normalized)

  31. Future Work • Seriously, lots to do: • Packet resizing  Less coding  Scriptability • Help me out! Progress Graph Visual interpretation 0 1 Perceived length (normalized)

  32. Don’t get me wrong ...  I • Well, mostly :-)

  33. Summary • Framework for packet trace manipulation • Can handle traces of arbitrary size • Multiple usage paradigms: GUI + command line • Reusable at all levels • libpcapnav for navigation • libnetdude for packet mangling • Netdude GUI for visualization • Extensible through protocol and feature plugins

  34. Thanks! • Shoutouts to all contributors! • Debian packagers needed ... • Questions? http://netdude.sf.net

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