Ashin Walpola
75d6d3b85c
Signed packets. A GeoNetworking Basic Header NextHeader of 2 means a TS 103 097 (IEEE 1609.2) envelope follows, with the Common Header inside it. gn_unwrap_its rejected all of these, and most real traffic is signed: the 2026-08-17 capture holds 157 signed frames from 15 source MACs against 2 unsecured stations. It now opens a COER-encoded signedData, or a bare unsecuredData, and parses the inner packet as before. The inner packet comes first inside tbsData, so the certificate and signature are never parsed, and the signature is not verified - the firmware has no trust store. Such messages reach the phone with the new V2X_RX flags bit1, signed but not verified. The app reads only bit0 and is unaffected until it learns the flag. Encrypted payloads, nested signing and the legacy v1.2.1 envelope are still rejected. All 157 recorded signed frames have the layout this reads, in all three COER length forms, and asn1tools decodes every envelope to the same inner packet. Payload bounds. Every frame recorded through the ESP32-C5's promiscuous RX, about 15 000 of them, ends in 8 bytes that are not part of the 802.11 frame and not a valid FCS. obu-firmware reads frames through the same API and took the rest of the frame as the message, so it forwarded those 8 bytes to the phone after every message. UPER decoders stop where the message ends, so nothing visibly broke, but the bytes cost serial bandwidth and 8 bytes of the DENM's headroom, and they stayed attached wherever raw payloads were stored or passed on. The payload is now exactly what the Common Header's payload-length field declares, which is also what separates a signed message from its signature. A frame longer than main.c's 800-byte capture buffer is now reported as truncated instead of being forwarded cut off, and counted as an oversize drop through the new serial_link_note_oversize_drop, as it was when the cut-off frame failed serial_link's size check. Host tests in obu-firmware/test/host build the firmware sources unmodified with MSYS2 gcc; `make` runs all three. - test_chain: frames from the firmware's TX code checked byte by byte against EN 302 636-4-1 and parsed back, including hand-built signed frames, the payload-length rule, the RX trailer, and every truncation length against a no-access guard page. 1731 checks, 0 failures. - test_replay and check_replay.py: all 15 145 recorded frames through gn_unwrap_its, cut to 800 bytes as on the board, and re-derived independently in Python with the envelope decoded by asn1tools. They agree on every record; 15 131 accepted, 157 of them signed. 11 043 of the 11 106 distinct messages re-encode byte-identically. The other 63 fail the same way with the old 8 bytes put back, so the boundary is not the cause: 5 are our own CAMs from before the 2026-08-20 yawRateConfidence fix, and the rest, from other stations, are a follow-up in TODO.md. - fuzz_gn_unwrap: random edits of every recorded frame, each run against the guard page. 50 000 000 iterations, no crash. obu-firmware/test/pcap_gn_tally.py tallies GeoNetworking header fields per station over captures; it is how the other stations' lifetimes were measured. TODO.md collects what is still open, including the on-air check for this change: it builds on IDF 6.1 but has not been flashed.
59 lines
2.0 KiB
Makefile
59 lines
2.0 KiB
Makefile
# Host-side tests for obu-firmware. See README.md: needs gcc and make on PATH (MSYS2 UCRT64), and
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# asn1tools under `py -3.11` for the replay check.
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#
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# make build and run everything: chain, replay, fuzz
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# make chain | replay | fuzz one of them
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# make fuzz FUZZ_ITER=50000000 FUZZ_SEED=7 a longer or different fuzz run
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# make clean remove build/
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#
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# The firmware sources are compiled straight from ../../main, never copied.
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CC = gcc
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PYTHON = python
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PYTHON_ASN1 = py -3.11
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FW = ../../main
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BUILD = build
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EXE = $(if $(filter Windows_NT,$(OS)),.exe,)
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RECORDINGS = $(wildcard ../../../its-g5-receiver-firmware/recordings/*.pcap)
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FUZZ_ITER = 2000000
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FUZZ_SEED = 1
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# -Werror: these sources must stay warning-free on the host compiler too.
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# UBSan in trap mode needs no runtime library, so it works on MinGW; a trap shows up as a crash.
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CFLAGS = -std=c11 -O2 -g -Wall -Wextra -Wpedantic -Werror -I$(FW) \
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-fsanitize=undefined -fsanitize-undefined-trap-on-error
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FW_SRCS = $(FW)/geonet.c $(FW)/dot11p.c $(FW)/gn_unwrap.c
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DEPS = test_util.c test_util.h $(FW_SRCS) $(wildcard $(FW)/*.h)
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.PHONY: all check chain replay fuzz clean
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all: check
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check: chain replay fuzz
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$(BUILD):
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mkdir -p $@
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$(BUILD)/%$(EXE): %.c $(DEPS) | $(BUILD)
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$(CC) $(CFLAGS) -o $@ $< test_util.c $(FW_SRCS)
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# The pcap goes through pcap_gn_tally.py as a second, independent parser of the same frames.
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chain: $(BUILD)/test_chain$(EXE)
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$(BUILD)/test_chain$(EXE) $(BUILD)/test_chain.pcap
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$(PYTHON) ../pcap_gn_tally.py $(BUILD)/test_chain.pcap
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replay: $(BUILD)/test_replay$(EXE)
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ifeq ($(RECORDINGS),)
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@echo "replay: no recordings in ../../../its-g5-receiver-firmware/recordings, skipped"
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else
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$(BUILD)/test_replay$(EXE) $(BUILD)/replay.tsv $(RECORDINGS)
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$(PYTHON_ASN1) check_replay.py $(BUILD)/replay.tsv $(RECORDINGS)
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endif
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fuzz: $(BUILD)/fuzz_gn_unwrap$(EXE)
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$(BUILD)/fuzz_gn_unwrap$(EXE) $(FUZZ_ITER) $(FUZZ_SEED) $(RECORDINGS)
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clean:
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rm -rf $(BUILD)
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