Add PCAP file parser for protocol analysis (#1331)

Author: rytilahti

devtools/README.md

@@ -2,6 +2,15 @@
 
 This directory contains tooling useful for developers
 
+## PCAP parser (parse_pcap.py)
+
+This tool parses PCAP file and tries to decrypt the traffic using the given tokens. Requires typer, dpkt, and rich.
+Token option can be used multiple times. All tokens are tested for decryption until decryption succeeds or there are no tokens left to try.
+
+```
+python pcap_parser.py <pcap file> --token <token> [--token <token>]
+```
+
 ## MiOT generator
 
 This tool generates some boilerplate code for adding support for MIoT devices

devtools/parse_pcap.py

@@ -0,0 +1,84 @@
+"""Parse PCAP files for miio traffic."""
+from collections import Counter, defaultdict
+from ipaddress import ip_address
+
+import dpkt
+import typer
+from dpkt.ethernet import ETH_TYPE_IP, Ethernet
+from rich import print
+
+from miio import Message
+
+app = typer.Typer()
+
+
+def read_payloads_from_file(file, tokens: list[str]):
+    """Read the given pcap file and yield src, dst, and result."""
+    pcap = dpkt.pcap.Reader(file)
+
+    stats: defaultdict[str, Counter] = defaultdict(Counter)
+    for _ts, pkt in pcap:
+        eth = Ethernet(pkt)
+        if eth.type != ETH_TYPE_IP:
+            continue
+
+        ip = eth.ip
+
+        if ip.p != 17:
+            continue
+
+        transport = ip.udp
+
+        if transport.dport != 54321 and transport.sport != 54321:
+            continue
+
+        data = transport.data
+
+        src_addr = str(ip_address(ip.src))
+        dst_addr = str(ip_address(ip.dst))
+
+        decrypted = None
+        for token in tokens:
+            try:
+                decrypted = Message.parse(data, token=bytes.fromhex(token))
+
+                break
+            except BaseException:
+                continue
+
+        if decrypted is None:
+            continue
+
+        stats["stats"]["miio_packets"] += 1
+
+        if decrypted.data.length == 0:
+            stats["stats"]["empty_packets"] += 1
+            continue
+
+        stats["dst_addr"][dst_addr] += 1
+        stats["src_addr"][src_addr] += 1
+
+        payload = decrypted.data.value
+
+        if "result" in payload:
+            stats["stats"]["results"] += 1
+        if "method" in payload:
+            method = payload["method"]
+            stats["commands"][method] += 1
+
+        yield src_addr, dst_addr, payload
+
+    print(stats)  # noqa: T001
+
+
+@app.command()
+def read_file(
+    file: typer.FileBinaryRead, token: list[str] = typer.Option(...)  # noqa: B008
+):
+    """Read PCAP file and output decrypted miio communication."""
+    for src_addr, dst_addr, payload in read_payloads_from_file(file, token):
+        print(f"{src_addr:<15} -> {dst_addr:<15} {payload}")  # noqa: T001
+
+
+if __name__ == "__main__":
+    app()