From: Eric Biggers <ebiggers@kernel.org>
To: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
"Jason A . Donenfeld" <Jason@zx2c4.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
Theodore Ts'o <tytso@mit.edu>,
stable@vger.kernel.org
Subject: Re: [PATCH] lib/crypto: chacha - Zeroize permuted_state before it leaves scope
Date: Fri, 27 Mar 2026 13:42:43 -0700 [thread overview]
Message-ID: <20260327204104.GA61750@quark> (raw)
In-Reply-To: <20260326032920.39408-1-ebiggers@kernel.org>
On Wed, Mar 25, 2026 at 08:29:20PM -0700, Eric Biggers wrote:
> 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
> Signed-off-by: Eric Biggers <ebiggers@kernel.org>
> ---
>
> This patch is targeting libcrypto-fixes
Applied to https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=libcrypto-fixes
- Eric
prev parent reply other threads:[~2026-03-27 20:42 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-26 3:29 [PATCH] lib/crypto: chacha - Zeroize permuted_state before it leaves scope Eric Biggers
2026-03-27 16:16 ` Ard Biesheuvel
2026-03-27 20:42 ` Eric Biggers [this message]
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