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 9FF9F1A9B24; Mon, 23 Mar 2026 05:24:50 +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=1774243490; cv=none; b=IATKVN72c2uoZLruhvtNwu3WkQI3qlwbPLDLaE2Jb1oOCxkk/BEI97wN8WEIjP8f7thIl5pK5MVEizN8uyFUhhuMjtgDnRb2oM+PnzIoQgaj0xrAesuQtV+cd7KyaaLlfgrpr93c64AxWceLC8+dyjmXP6m4+U9C+fqt05VEa48= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774243490; c=relaxed/simple; bh=eusF8SOMQWdbEbP43z8o44IbOKrIx4jUr4mjRCu4esk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Fp90Cbcxm9ZAKPEzelNihrq+y6CyevPhJtlVuR1dg3JVEcTx5tMca/edt8ROJrnkIsL2ZgZ8Vd/f51jgEaU3Dm7Q01ncj/vEpqvXOSv1AK3/BjQvO009/QTXkxtSL+ARg07OTiyE8LVWTqGnm+CpmITiFaXSSXgRbruA54t3Y4g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FAjYcblD; 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="FAjYcblD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ED056C4CEF7; Mon, 23 Mar 2026 05:24:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774243490; bh=eusF8SOMQWdbEbP43z8o44IbOKrIx4jUr4mjRCu4esk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FAjYcblDepO7Nr0g/KCmmWlfPUIzrpar+YncGrJtTKYBT86afGPc1gekRVhhQ9jAh 1peOX9EEO0aneq02PYMC/or0/FfwzGYsTGEZZCSdmjvnLnIrSIRzyLticQerMWnRNX ZDjB9jzaqfCD8rNUDvVX6uk9nFHMRl23vAoVL9f8hWFbbxEKtq2abIddAN8naPsVCL Ld0Hna4noMu4CohaRlSyprhV3UUJOzM++05Sgc8Z0GWpe2mJkvv0A4JO8CDfPxL81g wTexPTWSbmuhWYhLNpKwFv9RY8GEJ+nO3ojBme/JbtShrn0UKw39SLZlCwf3qqwEQs jYMc2zxLGPQJQ== Date: Mon, 23 Mar 2026 07:24:46 +0200 From: Jarkko Sakkinen To: Mimi Zohar Cc: Chris Fenner , linux-integrity@vger.kernel.org, Jonathan McDowell , Eric Biggers , James Bottomley , David Howells , Paul Moore , James Morris , "Serge E. Hallyn" , "open list:KEYS-TRUSTED" , "open list:SECURITY SUBSYSTEM" , open list , Roberto Sassu Subject: Re: [PATCH v9 01/11] KEYS: trusted: Use get_random-fallback for TPM Message-ID: References: <20260125192526.782202-1-jarkko@kernel.org> <20260125192526.782202-2-jarkko@kernel.org> <06a08cbbe47111a1795e5dcd42fb8cc4be643a72.camel@linux.ibm.com> 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 Thu, Mar 05, 2026 at 10:37:08AM -0500, Mimi Zohar wrote: > On Tue, 2026-03-03 at 23:32 +0200, Jarkko Sakkinen wrote: > > On Fri, Feb 20, 2026 at 10:30:26AM -0800, Chris Fenner wrote: > > > My conclusion about TCG_TPM2_HMAC after [1] and [2] was that > > > TPM2_TCG_HMAC doesn't (or didn't at the time) actually solve the > > > threat model it claims to (active interposer adversaries), while > > > dramatically increasing the cost of many kernel TPM activities beyond > > > the amount that would have been required to just solve for > > > passive/bus-sniffer interposer adversaries. The added symmetric crypto > > > required to secure a TPM transaction is almost not noticeable; the big > > > performance problem is the re-bootstrapping of the session with ECDH > > > for every command. > > > > > > My primary concern at that time was, essentially, that TCG_TPM2_HMAC > > > punts on checking that the key that was used to secure the session was > > > actually resident in a real TPM and not just an interposer adversary. > > > I wrote up my understanding at > > > https://www.dlp.rip/decorative-cryptography, for anyone who wants a > > > long-form opinionated take :). > > > > > > Unless I'm wrong, or TCG_TPM2_HMAC has changed dramatically since > > > August, I don't think "TPM2_TCG_HMAC makes this too costly" is a > > > compelling reason to make a security decision. (There could be other > > > reasons to make choices about whether to use the TPM as a source of > > > randomness in the kernel! This just isn't one IMHO.) > > > > > > The version of TCG_TPM2_HMAC that I'd like to see someday would be one > > > that fully admits that its threat model is only passive interposers, > > > and sets up one session upon startup and ContextSaves/ContextLoads it > > > back into the TPM as needed in order to secure parameter encryption > > > for e.g., GetRandom() and Unseal() calls. > > > > Neither agreeing nor disagreeing but this patch set clearly does not > > move forward and I spent already enough energy for this. For better > > ideas the patches are available in queue branch. > > Jarkko, you totally ignored my comments below. I object to your removing the > TPM trusted-keys RNG support. It has not been removed but I can keep the patches still backed up in a branch, can't I? BR, Jarkko