Add minimum payload_len check for TRACE packet parsing#15
Open
Add minimum payload_len check for TRACE packet parsing#15
Conversation
weebl2000
force-pushed
the
fix/trace-min-payload-len
branch
from
5f2fc48 to
07b3d23
Compare
prefs is 5 char length :nerd:
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.
weebl2000
force-pushed
the
fix/trace-min-payload-len
branch
from
07b3d23 to
d13b147
Compare
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
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
Mirror of meshcore-dev#1663