From patchwork Tue Apr 22 09:57:18 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Marek_Beh=C3=BAn?= X-Patchwork-Id: 883273 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EF9251EB1A8; Tue, 22 Apr 2025 09:57:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745315845; cv=none; b=er9tpzmtfDibbE9Pu9E9aTUiUnnTvJ4ZD8jglcMck2OTrQljYw5ytcPEJ4LCHDhZ9JqOEIQGHY3Kh2Ra2Iwhkt84oQEIIWrLIiL5aTnwNggunu8mXmdT6zrDg05fE82xBlJb8OZLGFyjbbwke9qeJjcP4XElsh0ht2rldalA4Pw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745315845; c=relaxed/simple; bh=t1U5iu98UOVrBT4ZBbp17ocR2D+pzk83ZqkZJHQyekw=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=G86rwTsOXZlYxLcxCiy6pCTjcic8AMfZ3HjcYkEaYqPKO+iMjYdF0Me/jXzqGO9oVeZcskzTn58buU3IPpaTTjScVAxWcGh1PPg/FRpKTXO+sQlFejd67AvSgviz6YqsAexbysGn8HJu8yPxxjEHAYkPzzK+SfbnzrSh69MPuTI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oRY1KBfX; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oRY1KBfX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 31B2DC4CEE9; Tue, 22 Apr 2025 09:57:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1745315844; bh=t1U5iu98UOVrBT4ZBbp17ocR2D+pzk83ZqkZJHQyekw=; h=From:To:Cc:Subject:Date:From; b=oRY1KBfXD6XpEip2QJIKF9vcSvOYFSGYWB0yBS2TWWN5XoySex5XlxZQCPTgqSV/F ygHLWy89V2pRzcET2vZhQSkH4AzcEz+Wgyv25q9Hu5x254EpYG3RdSnq01Qhfqu5Fu Hg5ywdrncFxOLNJ5Nxk+11e9H0mRkJrVr6zOebhcrfGLxOoFT6vt0MkDGX+UehGJU9 URsZlrh0Si+X4AQdnCX0qGjPvHkZXPozCyQcJJ1rFLVD4cL2o9j6ZvOrrPfcF9JmS2 ih6c+DOzJleOp6+LRk7lkUmlJok5QtjmwdLw99V3ycWVCrZyooXKY2ydUFB92V/BDt yjEmO4PBxHDGQ== From: =?utf-8?q?Marek_Beh=C3=BAn?= To: linux-crypto@vger.kernel.org Cc: =?utf-8?q?Marek_Beh=C3=BAn?= , Herbert Xu , "David S. Miller" , Nicolas Ferre , Alexandre Belloni , Claudiu Beznea , Ard Biesheuvel , Linus Walleij , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH] crypto: atmel-sha204a - Set hwrng quality to lowest possible Date: Tue, 22 Apr 2025 11:57:18 +0200 Message-ID: <20250422095718.17360-1-kabel@kernel.org> X-Mailer: git-send-email 2.49.0 Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 According to the review by Bill Cox [1], the Atmel SHA204A random number generator produces random numbers with very low entropy. Set the lowest possible entropy for this chip just to be safe. [1] https://www.metzdowd.com/pipermail/cryptography/2014-December/023858.html Fixes: da001fb651b00e1d ("crypto: atmel-i2c - add support for SHA204A random number generator") Signed-off-by: Marek Behún --- drivers/crypto/atmel-sha204a.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/crypto/atmel-sha204a.c b/drivers/crypto/atmel-sha204a.c index 75bebec2c757..0fcf4a39de27 100644 --- a/drivers/crypto/atmel-sha204a.c +++ b/drivers/crypto/atmel-sha204a.c @@ -163,6 +163,12 @@ static int atmel_sha204a_probe(struct i2c_client *client) i2c_priv->hwrng.name = dev_name(&client->dev); i2c_priv->hwrng.read = atmel_sha204a_rng_read; + /* + * According to review by Bill Cox [1], this HWRNG has very low entropy. + * [1] https://www.metzdowd.com/pipermail/cryptography/2014-December/023858.html + */ + i2c_priv->hwrng.quality = 1; + ret = devm_hwrng_register(&client->dev, &i2c_priv->hwrng); if (ret) dev_warn(&client->dev, "failed to register RNG (%d)\n", ret);