fix: reject/clamp LDF signal bit_width > 64 to prevent UB in decode() - #25
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fix: reject/clamp LDF signal bit_width > 64 to prevent UB in decode()#25SoundMatt wants to merge 1 commit into
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lin::ldf::DB::decode() shifts a uint64_t by up to bit_width - 1 bits (`1ULL << i`) with no upper bound on the LDF-declared bit_width. LDF signals with bit_width > 64 (unconstrained int, no range check in parse_signals()) trigger a shift-by->=64, which is undefined behavior and aborts under UBSan. Reaching the actual UB requires decode()'s data argument to exceed 8 bytes, which is a normal, unbounded std::vector<uint8_t>& — a malformed or crafted .ldf file can therefore crash any process that parses it and later decodes an oversized frame against it. Fixes: - parse_signals() now rejects (skips) any signal whose parsed bit_width falls outside [1, 64], consistent with how the parser already skips other malformed signal lines rather than storing bad data. - decode() additionally clamps its own loop bound to [0, 64] as defense in depth, since DB's storage members are public and a Signal can be constructed directly by a caller that bypasses the text parser entirely. Closes #18 Signed-off-by: Matt <47545907+SoundMatt@users.noreply.github.com>
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Summary
lin::ldf::DB::decode()has an unclamped bit-shift for LDF signals withbit_width > 64— undefined behavior (aborts under UBSan), reachable via amalformed/crafted
.ldffile plus adecode()call against a >8-bytebuffer.
parse_signals()now rejects (skips) any signal whose declaredbit_widthis outside[1, 64].decode()additionally clamps its own loop bound to[0, 64]as defensein depth, since
DB's storage is public and aSignalcan beconstructed directly without going through the text parser.
Closes #18
Test plan
ctest— 174/174 pass (3 new regression tests: parser-level rejectionof
bit_width128 and 0, plus adecode()-level defense-in-depthtest that directly constructs a
DB/Signalwithbit_width = 200bypassing the parser, and confirms no UB/crash and a correctly
clamped result)
relay conform --strict/relay interop --protocol LIN— both PASS