SLH-DSA fixes#10698
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Zeroization: - Add missing ForceZero on the PRF outputs and WOTS+ chain state that hold secret key material. - Route the WOTS sign leaf through a temp so secret chain values never touch the public signature buffer. - Add SLHDSA_SHAKE_X4_STATE_W so buffer and wipe sizes stay in sync. Leak / alloc-failure fixes: - Fix chain_idx_x4 returning on SAVE_VECTOR_REGISTERS2 failure without freeing state/fixed (memory leak, and the secret was left unzeroized); break to the cleanup path instead. - Guard all function-scope wipes with WC_VAR_OK to avoid a NULL deref when an allocation fails under WOLFSSL_SMALL_STACK.
JacobBarthelmeh
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Jun 17, 2026
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Pull request overview
This PR hardens the SLH-DSA implementation by tightening secret handling (zeroization and avoiding secret material landing in public output buffers) and by fixing error-path cleanup for AVX2/x4 SHAKE helpers when allocations or vector-register save operations fail.
Changes:
- Add missing
ForceZero()wipes for secret PRF outputs and WOTS+ chain state, withWC_VAR_OK()guards where allocation can fail underWOLFSSL_SMALL_STACK. - Fix
SAVE_VECTOR_REGISTERS2()failure handling in x4 chain iteration helpers to go through cleanup (avoid leaks / skipped wipes). - Introduce
SLHDSA_SHAKE_X4_STATE_Was a single constant for x4 SHAKE state sizing and use a temp buffer in WOTS signing so intermediate secret values don’t touch the signature buffer.
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Fenrir Automated Review — PR #10698
Scan targets checked: wolfcrypt-bugs, wolfcrypt-src
No new issues found in the changed files. ✅
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Zeroization:
ForceZeroon the PRF outputs and WOTS+ chain state that hold secret key material.SLHDSA_SHAKE_X4_STATE_Wso buffer and wipe sizes stay in sync.Leak / alloc-failure fixes:
chain_idx_x4returning onSAVE_VECTOR_REGISTERS2failure without freeing state/fixed (memory leak, and the secret was left unzeroized); break to the cleanup path instead.WC_VAR_OKto avoid aNULLderef when an allocation fails underWOLFSSL_SMALL_STACK.