From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lamorak.hansenpartnership.com (lamorak.hansenpartnership.com [198.37.111.173]) (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 6146D321442; Tue, 16 Dec 2025 06:48:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.37.111.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765867712; cv=none; b=EzQTzZcOtMCxDfA3u9sPFkvSBaGfzkr1HCvbf943pFp4S4SxFLgAUc7dqwmr1u9V5BTzPcifsQtCCr+DzFlK7SonIks75nFjmATXdrqO55AU1aONdYB3X0HVpqjLvFPKgVNwUXyOOBdjJYkwBkuwi8Z2NNmXNBTVYGZLnG7E7DU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765867712; c=relaxed/simple; bh=7hJvRz6vwdZirckhWi0Jb4gANaI51gofOFt3bbHBTfM=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=DHk+mqAJ+25tJ28BbSqR/3Pt8oGRmNSMu5xTIsEsQureX9ci/qBiK9EYTU5eC/KdP+TtcYoJZYAzn0SRHu5zrkQ48lqC8XV0a16Ntq6oCkQyRWfG4AlcofjSsrnqyYMvwBQh47PLElqzpW+GP/Yf4Lzax2IDgUPrWyo7RM74/do= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=HansenPartnership.com; spf=pass smtp.mailfrom=HansenPartnership.com; dkim=pass (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b=tUX9qhC3; arc=none smtp.client-ip=198.37.111.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=HansenPartnership.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=HansenPartnership.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b="tUX9qhC3" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=hansenpartnership.com; s=20151216; t=1765867704; bh=7hJvRz6vwdZirckhWi0Jb4gANaI51gofOFt3bbHBTfM=; h=Message-ID:Subject:From:To:Date:In-Reply-To:References:From; b=tUX9qhC3MDlMV5CZj96zgFkxWkWK72LnCS/ZH6tB/xpTJPtTe+7zK40D5XrgiM5C4 +FNaffTOM2t6iGJi94yPHTVFsr9nOe0Wpw5VzcC3iAhtY4KEP7pqhvemLUrGWDfiJF 5fhoihWDO/gOKTiBs1f5CKkxvrrUJhWc+gKoOxpg= Received: from [192.168.59.47] (unknown [46.140.184.114]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lamorak.hansenpartnership.com (Postfix) with ESMTPSA id 535CB1C024E; Tue, 16 Dec 2025 01:48:22 -0500 (EST) Message-ID: <1981bcdad096a820accf3a783181ae366cf2f8dd.camel@HansenPartnership.com> Subject: Re: [PATCH] KEYS: trusted: Use get_random-fallback for TPM From: James Bottomley To: Jarkko Sakkinen , Eric Biggers Cc: linux-integrity@vger.kernel.org, David Howells , Paul Moore , James Morris , "Serge E. Hallyn" , Mimi Zohar , "open list:KEYS/KEYRINGS" , "open list:SECURITY SUBSYSTEM" , open list , "Jason A. Donenfeld" Date: Tue, 16 Dec 2025 07:48:20 +0100 In-Reply-To: References: <20251214213236.339586-1-jarkko@kernel.org> <20251215200939.GA10539@google.com> Autocrypt: addr=James.Bottomley@HansenPartnership.com; prefer-encrypt=mutual; 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 8mT2Eh9SkH+YVOmaKsajgZgrBxA7fWmGoxXswEVxJIFj3vW7yNc0C5HaUdYa5iGOMs4kg2ht4s7yy7NRQuh7BifWjo6BQ6k4S1H+6axZucxhSV1L6zN9d+lr3Xo/vy1unzA== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.3 Precedence: bulk X-Mailing-List: linux-integrity@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2025-12-15 at 23:09 +0200, Jarkko Sakkinen wrote: > Using combined entropy also decreases corrateral damage caused by > e.g., a buggy TPM firmware, which does happen sometimes in the wild. Just to allay concerns on this point: the random number generator of a physical TPM is always based on a hardware entropy generating element. NIST specifies (and FIPS testing requires) that this hardware element conform to SP 800-90B which is about 84 pages of how a RNG should be conditioned and tested (and certified), so there should be very little chance of issues here. While TPMs have had problems caused by buggy firmware in the past, it's always affected areas that the FIPS testing doesn't cover in such depth (like the Infineon weak prime problem). People should feel confident in the TPM random number generator (particularly because it's the primary boot time entropy source for the in-kernel RNG on most laptops). Regards, James