From mboxrd@z Thu Jan 1 00:00:00 1970 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 BCAD32DECB4; Mon, 27 Oct 2025 19:51:23 +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=1761594683; cv=none; b=SwFqoLVdOsPVnUGT8Hk/OLcXnNOPj5B3QllxarTdYz95zctdHKNOyvQWYYnZ6by9eLwfAIGMlvkQGak+O1GOLXex1OujHI/AZ2CUiX1cohbIhO0+mrYwVFlYESPxJbAT4AC9PwSsueYII1FlaLl09gV56yzZ9/2Kw+vDcEZXU3Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761594683; c=relaxed/simple; bh=Pk4X+7GFkmLsnGR/SwJNrClCir6ovgFLwHy360kWcBY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Hd0s0KPMGUYGCqOC77IubU68oWXkPC1NBd16+kdZ8tnHanQwrTU+GqSsU5syWhlwvZ6PPWhgy1fqWG5yZj44iMcbztMtaA2fzhxRwYvJxKPPwYdPDHqnX/SCHkX4gYiEwu2WrHDdExjThFOQ6Tz4WkiQ+35olIn/UutOlf0xjDc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WQ62Njui; 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="WQ62Njui" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CF68BC4CEF1; Mon, 27 Oct 2025 19:51:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761594683; bh=Pk4X+7GFkmLsnGR/SwJNrClCir6ovgFLwHy360kWcBY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WQ62Njuijfkcq9Yzi/L+qU6Gb1+aLtA7bFCHwa2oGLNiBe73pwQ9dd6k0LcgJmUeT jvfTU93ykAt+iwV0YmENlCqN3dxzc18OR5d1jz+RGjI9zag6jVPbkHKaP+BDZSxcmy Ih5yTXi44Gp0yGhrAv3s1ckPc5EkONGBmJMTqBANJ/tdjcN0Q5wEd9By4z/b3SFv3S yszA2vYDGPQZSDsk7LTJwll3MCtr6fWm1ba5QXgcD1MewYRCyFpmCs6HeZ7DDxD/Pq M1bFn+eBM/2WKzmHSgTdMD6aNTlWQQF1vYRdt/Xzi2A3PEnwNyDQmQGLQZ0eSrBHFi +E2UDAHJB7b2g== Date: Mon, 27 Oct 2025 21:51:19 +0200 From: Jarkko Sakkinen To: Jan Kiszka Cc: Peter Huewe , linux-integrity@vger.kernel.org, Linux Kernel Mailing List , Ilias Apalodimas , Jens Wiklander , OP-TEE TrustedFirmware , linux-crypto@vger.kernel.org Subject: Re: [PATCH] hwrng: tpm: Do not enable by default Message-ID: References: Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Oct 21, 2025 at 02:46:15PM +0200, Jan Kiszka wrote: > From: Jan Kiszka > > As seen with optee_ftpm, which uses ms-tpm-20-ref [1], a TPM may write > the current time epoch to its NV storage every 4 seconds if there are > commands sent to it. The 60 seconds periodic update of the entropy pool > that the hwrng kthread does triggers this, causing about 4 writes per > requests. Makes 2 millions per year for a 24/7 device, and that is a lot > for its backing NV storage. > > It is therefore better to make the user intentionally enable this, > providing a chance to read the warning. > > [1] https://github.com/Microsoft/ms-tpm-20-ref > > Signed-off-by: Jan Kiszka Looking at DRBG_* from [1] I don't see anything you describe. If OPTEE writes NVRAM, then the implementation is broken. Also AFAIK, it is pre-seeded per power cycle. There's nothing that even distantly relates on using NVRAM. [1] https://trustedcomputinggroup.org/wp-content/uploads/TPM-2.0-1.83-Part-4-Supporting-Routines-Code.pdf BR, Jarkko From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.trustedfirmware.org (lists.trustedfirmware.org [18.214.241.189]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7BBC2CCF9E5 for ; Mon, 27 Oct 2025 19:51:35 +0000 (UTC) Received: from lists.trustedfirmware.org (localhost [127.0.0.1]) by lists.trustedfirmware.org (Postfix) with ESMTP id B45844FF9E for ; Mon, 27 Oct 2025 19:51:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=lists.trustedfirmware.org; s=2024; t=1761594694; bh=Pk4X+7GFkmLsnGR/SwJNrClCir6ovgFLwHy360kWcBY=; h=Date:To:Subject:References:In-Reply-To:CC:List-Id:List-Archive: List-Help:List-Owner:List-Post:List-Subscribe:List-Unsubscribe: From:Reply-To:From; b=B/5Raqcemh3+wRTjxyvNsWf13sIXM3I7hdPlvcgV0lAsbzy2VdLWoonWbyZWH7VQw pB5zVBzLlFkFT+Or3vhluJaluidRuthPGiQFREINXYGubwDl7SPzvFDrKa5udTh4sg 9Fj24m6SrkYgOkcjNyeQyMdAHvy4Vj30SnAtrXEzeJmhP2OPo6FzPswboVo5xZDYnm 7v14wdM6dm3TB352l+HNIV0NCfr5Tz383FDjddnnE5lUotG5F591EdCEUhZfCWuZPL JfDvk8eC80p/bKer94O0DmGoOzR0I8L2nvjMosZjXgucXZF9aH1xsBpN3keKfcleBV SNuL7KPmuJH4w== Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by lists.trustedfirmware.org (Postfix) with ESMTPS id 598CD41B65 for ; Mon, 27 Oct 2025 19:51:24 +0000 (UTC) Authentication-Results: lists.trustedfirmware.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=WQ62Njui; dkim-atps=neutral Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 8D03360510; Mon, 27 Oct 2025 19:51:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CF68BC4CEF1; Mon, 27 Oct 2025 19:51:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761594683; bh=Pk4X+7GFkmLsnGR/SwJNrClCir6ovgFLwHy360kWcBY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WQ62Njuijfkcq9Yzi/L+qU6Gb1+aLtA7bFCHwa2oGLNiBe73pwQ9dd6k0LcgJmUeT jvfTU93ykAt+iwV0YmENlCqN3dxzc18OR5d1jz+RGjI9zag6jVPbkHKaP+BDZSxcmy Ih5yTXi44Gp0yGhrAv3s1ckPc5EkONGBmJMTqBANJ/tdjcN0Q5wEd9By4z/b3SFv3S yszA2vYDGPQZSDsk7LTJwll3MCtr6fWm1ba5QXgcD1MewYRCyFpmCs6HeZ7DDxD/Pq M1bFn+eBM/2WKzmHSgTdMD6aNTlWQQF1vYRdt/Xzi2A3PEnwNyDQmQGLQZ0eSrBHFi +E2UDAHJB7b2g== Date: Mon, 27 Oct 2025 21:51:19 +0200 To: Jan Kiszka Subject: Re: [PATCH] hwrng: tpm: Do not enable by default Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 598CD41B65 X-Spamd-Bar: --- X-Spamd-Result: default: False [-3.41 / 15.00]; BAYES_HAM(-2.41)[97.29%]; DMARC_POLICY_ALLOW(-0.50)[kernel.org,quarantine]; R_SPF_ALLOW(-0.20)[+ip4:172.105.4.254]; R_DKIM_ALLOW(-0.20)[kernel.org:s=k20201202]; MIME_GOOD(-0.10)[text/plain]; DWL_DNSWL_BLOCKED(0.00)[kernel.org:dkim]; RCVD_VIA_SMTP_AUTH(0.00)[]; ASN(0.00)[asn:63949, ipnet:172.105.0.0/19, country:SG]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; MISSING_XM_UA(0.00)[]; HAS_WP_URI(0.00)[]; RCPT_COUNT_SEVEN(0.00)[8]; MID_RHS_MATCH_FROM(0.00)[]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[gmx.de,vger.kernel.org,linaro.org,lists.trustedfirmware.org]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; RCVD_TLS_LAST(0.00)[]; DKIM_TRACE(0.00)[kernel.org:+] X-Rspamd-Action: no action X-Rspamd-Server: lists.trustedfirmware.org Message-ID-Hash: IQECSUBURPBQJ7QG5O72PUHSA6CPQVCU X-Message-ID-Hash: IQECSUBURPBQJ7QG5O72PUHSA6CPQVCU X-MailFrom: jarkko@kernel.org X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-op-tee.lists.trustedfirmware.org-0; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: Peter Huewe , linux-integrity@vger.kernel.org, Linux Kernel Mailing List , Ilias Apalodimas , OP-TEE TrustedFirmware , linux-crypto@vger.kernel.org X-Mailman-Version: 3.3.5 Precedence: list List-Id: Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: From: Jarkko Sakkinen via OP-TEE Reply-To: Jarkko Sakkinen On Tue, Oct 21, 2025 at 02:46:15PM +0200, Jan Kiszka wrote: > From: Jan Kiszka > > As seen with optee_ftpm, which uses ms-tpm-20-ref [1], a TPM may write > the current time epoch to its NV storage every 4 seconds if there are > commands sent to it. The 60 seconds periodic update of the entropy pool > that the hwrng kthread does triggers this, causing about 4 writes per > requests. Makes 2 millions per year for a 24/7 device, and that is a lot > for its backing NV storage. > > It is therefore better to make the user intentionally enable this, > providing a chance to read the warning. > > [1] https://github.com/Microsoft/ms-tpm-20-ref > > Signed-off-by: Jan Kiszka Looking at DRBG_* from [1] I don't see anything you describe. If OPTEE writes NVRAM, then the implementation is broken. Also AFAIK, it is pre-seeded per power cycle. There's nothing that even distantly relates on using NVRAM. [1] https://trustedcomputinggroup.org/wp-content/uploads/TPM-2.0-1.83-Part-4-Supporting-Routines-Code.pdf BR, Jarkko