From e5046823f8fa3677341b541a25af2fcb99a5b1e0 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Wed, 25 Mar 2026 20:29:20 -0700 Subject: lib/crypto: chacha: Zeroize permuted_state before it leaves scope Since the ChaCha permutation is invertible, the local variable 'permuted_state' is sufficient to compute the original 'state', and thus the key, even after the permutation has been done. While the kernel is quite inconsistent about zeroizing secrets on the stack (and some prominent userspace crypto libraries don't bother at all since it's not guaranteed to work anyway), the kernel does try to do it as a best practice, especially in cases involving the RNG. Thus, explicitly zeroize 'permuted_state' before it goes out of scope. Fixes: c08d0e647305 ("crypto: chacha20 - Add a generic ChaCha20 stream cipher implementation") Cc: stable@vger.kernel.org Acked-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20260326032920.39408-1-ebiggers@kernel.org Signed-off-by: Eric Biggers --- lib/crypto/chacha-block-generic.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/lib/crypto/chacha-block-generic.c b/lib/crypto/chacha-block-generic.c index 77f68de71066..4a6d627580cb 100644 --- a/lib/crypto/chacha-block-generic.c +++ b/lib/crypto/chacha-block-generic.c @@ -87,6 +87,8 @@ void chacha_block_generic(struct chacha_state *state, &out[i * sizeof(u32)]); state->x[12]++; + + chacha_zeroize_state(&permuted_state); } EXPORT_SYMBOL(chacha_block_generic); @@ -110,5 +112,7 @@ void hchacha_block_generic(const struct chacha_state *state, memcpy(&out[0], &permuted_state.x[0], 16); memcpy(&out[4], &permuted_state.x[12], 16); + + chacha_zeroize_state(&permuted_state); } EXPORT_SYMBOL(hchacha_block_generic); -- cgit v1.2.3