Tighten TRACE path_len guard to account for SNR append#1658
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weebl2000 wants to merge 1 commit intomeshcore-dev:devfrom
Open
Tighten TRACE path_len guard to account for SNR append#1658weebl2000 wants to merge 1 commit intomeshcore-dev:devfrom
weebl2000 wants to merge 1 commit intomeshcore-dev:devfrom
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The TRACE forwarding path appends an SNR byte to pkt->path via path_len++, but the guard only checked path_len < MAX_PATH_SIZE. When path_len entered as MAX_PATH_SIZE - 1, the write was in-bounds but left path_len equal to MAX_PATH_SIZE, which could cause off-by-one issues in downstream code that uses path_len as an index. Change the guard to path_len + 1 < MAX_PATH_SIZE so there is always room for the append without path_len reaching MAX_PATH_SIZE.
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Severity: Low
Summary
When a node forwards a TRACE packet, it appends its SNR reading to
pkt->pathand incrementspath_len. The existing guard checkspath_len < MAX_PATH_SIZE, which allowspath_lenof 63 through. After the append,path_lenbecomes 64 — equal toMAX_PATH_SIZE. The write itself is in-bounds (the array is 64 bytes, index 63 is valid), butpath_lenis now at the maximum, which could cause an off-by-one in any downstream code that usespath_lenas an array index without re-checking.Not exploitable in the current codebase, but a defensive fix to prevent future bugs as the code evolves.
Fix
Change the guard from
path_len < MAX_PATH_SIZEtopath_len + 1 < MAX_PATH_SIZE, ensuring there is always room for the SNR append withoutpath_lenreachingMAX_PATH_SIZE.Test plan
Heltec_v3_companion_radio_bleBuild firmware: Build from this branch