From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-189.mta1.migadu.com (out-189.mta1.migadu.com [95.215.58.189]) (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 F34683B95E9 for ; Mon, 27 Apr 2026 12:41:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.189 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777293694; cv=none; b=XuNXDLMACsWr9Xitu9MDvKe8SYHNYI3/Ol2x9MaJJPKRPT6wVj4T0mguksaPZQsqX2JgEtsVXEfbdnlg5/eTnUwKj3NgTkOgx4H+UEZuF0edTpC58ZSLEKSaB04JtbEbh/OWmWAbo4G75iV5LD/fBbNEfkxlsQOY2bPuraMKphw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777293694; c=relaxed/simple; bh=rPsElOTnBU2IAaqPJKzszB9VzGW4gBafqHa3s/4eJvE=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=SUCKtaE6qOGfAU+14rt9gkm1PDFTpcVMbQLk7cPvfY76C03Ql/6o80pJUBkKCYFNP/Ke23jGw2bKW0ZCZ2zvnDGh7dfrYPkGU1cfJPJozsPmZlVQq0AvrT4xIP+X9XxQJjMFQMUPEv/v9Z5lJ51LGga/zNo1bmLiTRBJS8DyaU8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=SwVYql80; arc=none smtp.client-ip=95.215.58.189 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="SwVYql80" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1777293690; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=1hHanKhgSNPNyW7BtonFlH3iX6W/a+wogWqZOKIosO4=; b=SwVYql808T4i1NosCr+5XCBhbYxszy3j4bdvpSaN7hyrUVPJnDS4kjM7GTFV70EEhnhQ64 j5xjEVw9xCl1EK7bCx0xNVB8b93VYELLiIv91pgtpuFtKoWtOChxkAr777c65OBkvcvmoi cDLcCsPZiWVaUi8UxSi7++5yOh2tiEE= From: Thorsten Blum To: Thorsten Blum , Herbert Xu , "David S. Miller" , Nicolas Ferre , Alexandre Belloni , Claudiu Beznea , =?UTF-8?q?Marek=20Beh=C3=BAn?= , Ard Biesheuvel , Linus Walleij Cc: stable@vger.kernel.org, linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH] crypto: atmel-sha204a - drop hwrng quality reduction for ATSHA204A Date: Mon, 27 Apr 2026 14:40:32 +0200 Message-ID: <20260427124030.315590-3-thorsten.blum@linux.dev> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3771; i=thorsten.blum@linux.dev; h=from:subject; bh=rPsElOTnBU2IAaqPJKzszB9VzGW4gBafqHa3s/4eJvE=; b=owGbwMvMwCUWt7pQ4caZUj3G02pJDJnvI+02/HdQN7hmPueCfHr9w5tdL9aeNPmQs8Yga+78N IGLjaXMHaUsDGJcDLJiiiwPZv2Y4VtaU7nJJGInzBxWJpAhDFycAjCRDGmG/2ETlnxR8p9cppF5 Vl3/07rAaxx/brz2KuF9/7Q/tukskwAjw28np8U5s2a5rLsqqqPIVPV/F8+JU24qlqmrv4WrP3q 1kQEA X-Developer-Key: i=thorsten.blum@linux.dev; a=openpgp; fpr=1D60735E8AEF3BE473B69D84733678FD8DFEEAD4 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Commit 8006aff15516 ("crypto: atmel-sha204a - Set hwrng quality to lowest possible") reduced the hwrng quality to 1 based on a review by Bill Cox [1]. However, despite its title, the review only tested the ATSHA204, not the ATSHA204A. In the same thread, Atmel engineer Landon Cox wrote "this behavior has been eliminated entirely"[2] in the ATSHA204A and "this problem does not affect the ATECC108 or the ATECC108A (or the ATSHA204A)"[3]. According to the official ATSHA204A datasheet [4], the device contains a high-quality hardware RNG that combines its output with an internal seed value stored in EEPROM or SRAM to generate random numbers. The device also implements all security functions using SHA-256, and the driver uses the chip's Random command in seed-update mode. Keep 'quality = 1' for ATSHA204, but drop the explicit hwrng quality reduction for ATSHA204A and fall back to the hwrng core default. [1] https://www.metzdowd.com/pipermail/cryptography/2014-December/023858.html [2] https://www.metzdowd.com/pipermail/cryptography/2014-December/023852.html [3] https://www.metzdowd.com/pipermail/cryptography/2014-December/023886.html [4] https://ww1.microchip.com/downloads/en/DeviceDoc/ATSHA204A-Data-Sheet-40002025A.pdf Fixes: 8006aff15516 ("crypto: atmel-sha204a - Set hwrng quality to lowest possible") Cc: stable@vger.kernel.org Signed-off-by: Thorsten Blum --- drivers/crypto/atmel-sha204a.c | 40 ++++++++++++++++++---------------- 1 file changed, 21 insertions(+), 19 deletions(-) diff --git a/drivers/crypto/atmel-sha204a.c b/drivers/crypto/atmel-sha204a.c index dbb39ed0cea1..df69fb190e52 100644 --- a/drivers/crypto/atmel-sha204a.c +++ b/drivers/crypto/atmel-sha204a.c @@ -19,6 +19,25 @@ #include #include "atmel-i2c.h" +enum atmel_sha204a_variant { + ATSHA204 = 1, + ATSHA204A, +}; + +static const struct of_device_id atmel_sha204a_dt_ids[] __maybe_unused = { + { .compatible = "atmel,atsha204", .data = (void *)ATSHA204 }, + { .compatible = "atmel,atsha204a", .data = (void *)ATSHA204A }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, atmel_sha204a_dt_ids); + +static const struct i2c_device_id atmel_sha204a_id[] = { + { .name = "atsha204", .driver_data = ATSHA204 }, + { .name = "atsha204a", .driver_data = ATSHA204A }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(i2c, atmel_sha204a_id); + static void atmel_sha204a_rng_done(struct atmel_i2c_work_data *work_data, void *areq, int status) { @@ -171,11 +190,8 @@ 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; + if ((uintptr_t)i2c_get_match_data(client) == ATSHA204) + i2c_priv->hwrng.quality = 1; ret = devm_hwrng_register(&client->dev, &i2c_priv->hwrng); if (ret) @@ -202,20 +218,6 @@ static void atmel_sha204a_remove(struct i2c_client *client) kfree((void *)i2c_priv->hwrng.priv); } -static const struct of_device_id atmel_sha204a_dt_ids[] __maybe_unused = { - { .compatible = "atmel,atsha204", }, - { .compatible = "atmel,atsha204a", }, - { /* sentinel */ } -}; -MODULE_DEVICE_TABLE(of, atmel_sha204a_dt_ids); - -static const struct i2c_device_id atmel_sha204a_id[] = { - { "atsha204" }, - { "atsha204a" }, - { /* sentinel */ } -}; -MODULE_DEVICE_TABLE(i2c, atmel_sha204a_id); - static struct i2c_driver atmel_sha204a_driver = { .probe = atmel_sha204a_probe, .remove = atmel_sha204a_remove,