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 53BCC2E7653; Tue, 9 Dec 2025 18:27:24 +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=1765304845; cv=none; b=MnJ7jTJ1J987qFv4GRTTVRgpsXmFIY8Gv41XA9mHZUztcv92+qG1Qolecd8MPF/J2yASPIIHI8SCHXzS5FizfUHZGX/YXP5dL43GurHHHOB0tLikua1aQKluGgjqbMRb0wvUv73ZMi6+rsQjT1MVfqhs/qX9tGOK4cI+9xEUOug= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765304845; c=relaxed/simple; bh=Zl5u1a3GpQDX4mGUe2oRTt9rgp7JMmdOA5XWrWKB0RM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=klIGJMcRB2fC/yfLDyp5yprHTdUOrRf6h04RZugrlq3Ms9gBEoiSunZq4s05dLwOuyFXrdrl9NLrtzNWysR1ILUJzGYazCmaV0kj4IUMXFfPGahuk4mVwnQnjGUD4QU8XpkfZNH2aUaSTfSClxFLfazKD268N0c8UgIhzjSFN60= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ee4q71gg; 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="Ee4q71gg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6ADEFC4CEF5; Tue, 9 Dec 2025 18:27:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1765304844; bh=Zl5u1a3GpQDX4mGUe2oRTt9rgp7JMmdOA5XWrWKB0RM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Ee4q71ggbgIXL5QFmcfCeuY2A3FB2neqixGf85GP2oTGa8dpsDh51GMQ2DyUZv6A7 INxbcnzN6ZEyxXeGe/A+AoeD9HBI5OiyrPbBRc6BStA3a8LSHxmQqWYRXiv9Q0IOm2 yihjsGHDTkAeRs9oumo79w47zPJmLVXUY6kARdS/Qh7K7u4jgD72PtaGAs0u/mKGSB ymf1LUgUcfsz+9AZby7GgeMlKhfapCK+N6FoS90oYw4g748Xii5mW/s8yJjMaytMaw 3CcqL10tDYXyEdPSuqssxYt1lCa3X0p84hSD2psf+yEhBub5dYnk+zfGK2hXlc3I8L 9wkFaTZmNarqg== Date: Tue, 9 Dec 2025 20:27:21 +0200 From: Jarkko Sakkinen To: linux-integrity@vger.kernel.org Cc: Peter Huewe , Jason Gunthorpe , open list Subject: Re: [PATCH v2 0/5] Streamline TPM2 HMAC sessions Message-ID: References: <20251209100529.1700779-1-jarkko@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@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, Dec 09, 2025 at 07:32:27PM +0200, Jarkko Sakkinen wrote: > On Tue, Dec 09, 2025 at 05:42:55PM +0200, Jarkko Sakkinen wrote: > > On Tue, Dec 09, 2025 at 12:05:23PM +0200, Jarkko Sakkinen wrote: > > > Since we cannot at this point cache names of the keys given limitations > > > of the ASN.1 file format, I'll start a fresh patch set. Let's fixup what > > > we can right now. > > > > > > This patch set addresses two major issues in the feature: > > > > > > 1. Dynamic resolution without gain. All kernel sites have at most single > > > handle to authorize. Even if this changes some day this is how it is > > > as of today and we definitely do not want to dictate the future but > > > instead downscale code to the metrics that we have as of today. > > > 2. Eliminate at least one unnnecessary tpm2_read_public() call. > > > > > > Jarkko Sakkinen (5): > > > KEYS: trusted: Remove dead branch from tpm2_unseal_cmd > > > tpm2-sessions: Define TPM2_NAME_MAX_SIZE > > > KEYS: trusted: Re-orchestrate tpm2_read_public() calls > > > tpm2-sessions: Remove AUTH_MAX_NAMES > > > tpm-buf: Remove tpm_buf_append_handle > > > > > > drivers/char/tpm/tpm-buf.c | 25 ---- > > > drivers/char/tpm/tpm-sysfs.c | 2 +- > > > drivers/char/tpm/tpm2-cmd.c | 9 +- > > > drivers/char/tpm/tpm2-sessions.c | 130 ++++++--------------- > > > include/linux/tpm.h | 49 +++++--- > > > security/keys/trusted-keys/trusted_tpm2.c | 134 +++++++++++++--------- > > > 6 files changed, 155 insertions(+), 194 deletions(-) > > > > > > -- > > > 2.52.0 > > > > > > > For hwrng we can e.g., calculate factor by timing tpm2_get_random() with > > and without HMAC encryption. Then we can use this as frequency how often > > data is pulled. > > > > The other angle to combine this is to maintain largeish FIFO of random > > bytes and fill this when it goes below a treshold. > > > > Probably some combination of these will provide answer to performance > > and latency problem with hwrng when HMAC encryption is turned on: > > > > 1. The first amortizes the overall quota. > > 2. Second provides constant latency without major spikes. > > Another perhaps more unorthodox idea: > > 1. Calculate factor as said above. Let's call it N. > 2. Every Nth step seed a pseudo rng from TPM. > 3. On steps not divisible by N, pull from pseud rng. > > I'm not a cryptographer but would randomness suffer from this? Then the > seeds that woud come from TPM are HMAC encrypted at least without major > hits on performance. > > Just enumerated this. Not sure about this idea yet by any means but I do > like simplicy of it (and that also makes me concerned about missed > details). Third option would be to have simply a kthread with a rate that fills a pool and hwrng callbacks serves from that pool. If there is no bytes, there is no bytes (which is fine as far as API is concerned). This has optimal system latency properties I'd figure. BR, Jarkko