protocol-reverse-engineering

To reverse engineer a custom binary protocol from a pcap, you analyze captured traffic to infer message framing, identify fixed headers and variable payloads, and document field boundaries. This process transforms unknown network traffic into a structured protocol specification.

Identifying TLV structures and message boundaries in captured network traffic involves detecting protocol signatures and analyzing length/sequence fields. This maps binary message structures by matching header patterns to infer the layout of variable payloads.

You can decrypt TLS sessions in Wireshark to analyze proprietary application protocols by using TLS key logging. This allows you to extract metadata and inspect the unencrypted payload for undocumented binary formats.

Protocol reverse engineering works for both TCP and UDP services by analyzing packet captures from these streams. It supports inferring message framing and field semantics across different transport layers to build a complete protocol model.

To generate a protocol specification template from a pcap file, you dissect the captured traffic to map field boundaries and infer payload structures. This produces documented output with testable parser pseudocode suitable for implementing dissectors.

When reverse engineering encrypted traffic without TLS keys, the limitation is that payload field semantics cannot be directly inferred. You must rely on entropy analysis and metadata extraction, which prevents generating a complete protocol specification.