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liquidraver
b692ca72ed
Audit-driven sweep found additional compiler-optimization-sensitive patterns beyond the login password compare just fixed: P4.F3 (HIGH) — Utils::MACThenDecrypt verified packet MACs with plain memcmp. Runs on EVERY encrypted-then-MAC'd packet in the mesh; a timing oracle here lets attackers forge MACs byte-by-byte across the whole mesh layer. Replaced with constantTimeEqual. P4.F4 (MEDIUM) — Multiple memset(secret, 0, ...) calls on stack-resident crypto buffers (Ed25519 seed, ADC noise pool, AES key derived in extract_via_aes_ctr, HWINFO unique ID) were subject to dead-store elimination under -Os. GCC/Clang routinely elide these when the buffer is never read after; the wipe vanishes and the secret persists on stack until next call overwrites. Replaced with secureZeroize using volatile pointer writes. P4.F5 (LOW) — Identity::validatePrivateKey boot self-test compared shared secrets with plain memcmp. Boot-only, no attacker observation channel, but hygiene matters and the fix is one line. Also added secret-wipe for ss1/ss2 on all return paths. Promoted the local ct_memeq() previously added to RepeaterMesh.cpp into Utils::constantTimeEqual + Utils::secureZeroize (Utils.h/cpp) so the login compare and MAC compare share the same audited helper. Both helpers verified by Thumb-2 disassembly on rak3401_1watt: - constantTimeEqual: loop branches on iterator, accumulator load-modify-stored to stack every iteration, final return uses CLZ+LSR (no conditional branch on result). - secureZeroize: STRB.W to memory in a counted loop, not replaced with memset builtin and not eliminated.