Add minimum payload_len check for TRACE packet parsing#1663
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The TRACE handler reads 9 bytes (trace_tag, auth_code, flags) from the payload before any length validation. A short TRACE packet causes reads of stale buffer data and an underflow in the remaining-length calculation (uint8_t len = payload_len - 9 wraps to ~247). Add payload_len >= 9 to the existing guard condition so undersized TRACE packets are silently dropped.
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Severity: Medium
Summary
The TRACE packet handler reads 9 bytes from the payload —
trace_tag(4),auth_code(4), andflags(1) — before any length validation. The Dispatcher layer does not enforce a minimumpayload_lenfor any packet type, so a TRACE packet withpayload_len = 0reaches this code and reads stale data from the payload buffer.Additionally,
uint8_t len = pkt->payload_len - i(wherei = 9) underflows whenpayload_len < 9, wrapping to ~247. This can cause the subsequentoffset >= lencheck to pass or fail incorrectly, leading to unintended trace forwarding or hash matching against garbage data.Who can exploit this: any node on the mesh — TRACE packets are unauthenticated and direct-routed.
What it takes: a single crafted short TRACE packet.
What users might see
Incorrect trace routing, spurious trace forwarding, or (less likely) nodes processing traces they shouldn't. No crash — reads stay within the 184-byte payload buffer.
Fix
Add
pkt->payload_len >= 9to the existing guard condition so undersized TRACE packets are silently dropped before any field parsing.Test plan
Heltec_v3_companion_radio_bleBuild firmware: Build from this branch