From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.20]) (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 7BEA9156967 for ; Mon, 29 Jan 2024 21:04:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=134.134.136.20 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706562268; cv=none; b=g4exEdFwIGynaoL/CzQUTw08jy7Ys1tNIk8ySYkygz8F2s/3L0bpRj1EbViWo7AezCZg62LgTNIkW3Iv8LKrD0ixDoYWfkMfZVbBb4MgB1fE8Wwgr6848Ayy3OMNUBd+gjoVgdqQkRWzvPL7dHLRaU+Hhgk6R4gRwF5Kaf3GvC8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706562268; c=relaxed/simple; bh=txLCLPkzKVHdhvYurzAAldVYFeaSAhmddBNWP92y3q0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=dIrFO3i9pfGQkJHssy02mwVwLE2BGGpuX93DDG4j/t3hbtlEKs4bd3LneFZgEhS6Jb/BMVU2vWnUjaBapW5zZIwrEq9FEuqAmlx3hpspeaIHE7Xx56E2Ix1U2/fxL7kSa4AMhYAnp/QlQFoxdMGSfirssmiT5dz2xeBnJIPvT/k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=EXF1gTWh; arc=none smtp.client-ip=134.134.136.20 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="EXF1gTWh" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1706562266; x=1738098266; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=txLCLPkzKVHdhvYurzAAldVYFeaSAhmddBNWP92y3q0=; b=EXF1gTWhhfvwkPP+4UwEBN9ZuzJc1hW7TLErpnCMnEs5qKjLs4Hb8D53 lEvGlCsN3KKqL0HlpRwPKJE3rVMr02ErirmFR429XbzUyL5A7i+3uuglz Jixig7jqJYdlAN3xjLrYFUaVkrGcCusuEeMTvZAt/hUmoBR0BCygh7gKK iuh+h1Hfk97ZnHINvaiz4pW0JSPsOpb18+2QgDkAE855Vz7xcfJBJ4WbO 8SYUEDxlRm11wmyETAIAtUkGtOHEan+O5YgOmMcxsvRvu3GL+ZfPvAaWa Ct8j/l31DeobmHb3Ky855jwWKpXLNzQ9jFHET7klng2YrOj/yJj84GVw9 w==; X-IronPort-AV: E=McAfee;i="6600,9927,10968"; a="393521289" X-IronPort-AV: E=Sophos;i="6.05,227,1701158400"; d="scan'208";a="393521289" Received: from fmviesa002.fm.intel.com ([10.60.135.142]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jan 2024 13:04:25 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.05,227,1701158400"; d="scan'208";a="22226347" Received: from swayomab-mobl1.amr.corp.intel.com (HELO [10.212.130.221]) ([10.212.130.221]) by fmviesa002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jan 2024 13:04:23 -0800 Message-ID: <3a37eae3-9d3c-420c-a1c7-2d14f6982774@intel.com> Date: Mon, 29 Jan 2024 13:04:23 -0800 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC] Randomness on confidential computing platforms Content-Language: en-US To: "Kirill A. Shutemov" Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , x86@kernel.org, Theodore Ts'o , "Jason A. Donenfeld" , Kuppuswamy Sathyanarayanan , Elena Reshetova , Jun Nakajima , Tom Lendacky , "Kalra, Ashish" , Sean Christopherson , linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org References: <20240126134230.1166943-1-kirill.shutemov@linux.intel.com> <276aaeee-cb01-47d3-a3bf-f8fa2e59016c@intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; keydata= xsFNBE6HMP0BEADIMA3XYkQfF3dwHlj58Yjsc4E5y5G67cfbt8dvaUq2fx1lR0K9h1bOI6fC oAiUXvGAOxPDsB/P6UEOISPpLl5IuYsSwAeZGkdQ5g6m1xq7AlDJQZddhr/1DC/nMVa/2BoY 2UnKuZuSBu7lgOE193+7Uks3416N2hTkyKUSNkduyoZ9F5twiBhxPJwPtn/wnch6n5RsoXsb ygOEDxLEsSk/7eyFycjE+btUtAWZtx+HseyaGfqkZK0Z9bT1lsaHecmB203xShwCPT49Blxz VOab8668QpaEOdLGhtvrVYVK7x4skyT3nGWcgDCl5/Vp3TWA4K+IofwvXzX2ON/Mj7aQwf5W iC+3nWC7q0uxKwwsddJ0Nu+dpA/UORQWa1NiAftEoSpk5+nUUi0WE+5DRm0H+TXKBWMGNCFn c6+EKg5zQaa8KqymHcOrSXNPmzJuXvDQ8uj2J8XuzCZfK4uy1+YdIr0yyEMI7mdh4KX50LO1 pmowEqDh7dLShTOif/7UtQYrzYq9cPnjU2ZW4qd5Qz2joSGTG9eCXLz5PRe5SqHxv6ljk8mb ApNuY7bOXO/A7T2j5RwXIlcmssqIjBcxsRRoIbpCwWWGjkYjzYCjgsNFL6rt4OL11OUF37wL QcTl7fbCGv53KfKPdYD5hcbguLKi/aCccJK18ZwNjFhqr4MliQARAQABzUVEYXZpZCBDaHJp c3RvcGhlciBIYW5zZW4gKEludGVsIFdvcmsgQWRkcmVzcykgPGRhdmUuaGFuc2VuQGludGVs LmNvbT7CwXgEEwECACIFAlQ+9J0CGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEGg1 lTBwyZKwLZUP/0dnbhDc229u2u6WtK1s1cSd9WsflGXGagkR6liJ4um3XCfYWDHvIdkHYC1t MNcVHFBwmQkawxsYvgO8kXT3SaFZe4ISfB4K4CL2qp4JO+nJdlFUbZI7cz/Td9z8nHjMcWYF IQuTsWOLs/LBMTs+ANumibtw6UkiGVD3dfHJAOPNApjVr+M0P/lVmTeP8w0uVcd2syiaU5jB aht9CYATn+ytFGWZnBEEQFnqcibIaOrmoBLu2b3fKJEd8Jp7NHDSIdrvrMjYynmc6sZKUqH2 I1qOevaa8jUg7wlLJAWGfIqnu85kkqrVOkbNbk4TPub7VOqA6qG5GCNEIv6ZY7HLYd/vAkVY E8Plzq/NwLAuOWxvGrOl7OPuwVeR4hBDfcrNb990MFPpjGgACzAZyjdmYoMu8j3/MAEW4P0z F5+EYJAOZ+z212y1pchNNauehORXgjrNKsZwxwKpPY9qb84E3O9KYpwfATsqOoQ6tTgr+1BR CCwP712H+E9U5HJ0iibN/CDZFVPL1bRerHziuwuQuvE0qWg0+0SChFe9oq0KAwEkVs6ZDMB2 P16MieEEQ6StQRlvy2YBv80L1TMl3T90Bo1UUn6ARXEpcbFE0/aORH/jEXcRteb+vuik5UGY 5TsyLYdPur3TXm7XDBdmmyQVJjnJKYK9AQxj95KlXLVO38lczsFNBFRjzmoBEACyAxbvUEhd GDGNg0JhDdezyTdN8C9BFsdxyTLnSH31NRiyp1QtuxvcqGZjb2trDVuCbIzRrgMZLVgo3upr MIOx1CXEgmn23Zhh0EpdVHM8IKx9Z7V0r+rrpRWFE8/wQZngKYVi49PGoZj50ZEifEJ5qn/H Nsp2+Y+bTUjDdgWMATg9DiFMyv8fvoqgNsNyrrZTnSgoLzdxr89FGHZCoSoAK8gfgFHuO54B lI8QOfPDG9WDPJ66HCodjTlBEr/Cwq6GruxS5i2Y33YVqxvFvDa1tUtl+iJ2SWKS9kCai2DR 3BwVONJEYSDQaven/EHMlY1q8Vln3lGPsS11vSUK3QcNJjmrgYxH5KsVsf6PNRj9mp8Z1kIG qjRx08+nnyStWC0gZH6NrYyS9rpqH3j+hA2WcI7De51L4Rv9pFwzp161mvtc6eC/GxaiUGuH BNAVP0PY0fqvIC68p3rLIAW3f97uv4ce2RSQ7LbsPsimOeCo/5vgS6YQsj83E+AipPr09Caj 0hloj+hFoqiticNpmsxdWKoOsV0PftcQvBCCYuhKbZV9s5hjt9qn8CE86A5g5KqDf83Fxqm/ vXKgHNFHE5zgXGZnrmaf6resQzbvJHO0Fb0CcIohzrpPaL3YepcLDoCCgElGMGQjdCcSQ+Ci FCRl0Bvyj1YZUql+ZkptgGjikQARAQABwsFfBBgBAgAJBQJUY85qAhsMAAoJEGg1lTBwyZKw l4IQAIKHs/9po4spZDFyfDjunimEhVHqlUt7ggR1Hsl/tkvTSze8pI1P6dGp2XW6AnH1iayn yRcoyT0ZJ+Zmm4xAH1zqKjWplzqdb/dO28qk0bPso8+1oPO8oDhLm1+tY+cOvufXkBTm+whm +AyNTjaCRt6aSMnA/QHVGSJ8grrTJCoACVNhnXg/R0g90g8iV8Q+IBZyDkG0tBThaDdw1B2l asInUTeb9EiVfL/Zjdg5VWiF9LL7iS+9hTeVdR09vThQ/DhVbCNxVk+DtyBHsjOKifrVsYep WpRGBIAu3bK8eXtyvrw1igWTNs2wazJ71+0z2jMzbclKAyRHKU9JdN6Hkkgr2nPb561yjcB8 sIq1pFXKyO+nKy6SZYxOvHxCcjk2fkw6UmPU6/j/nQlj2lfOAgNVKuDLothIxzi8pndB8Jju KktE5HJqUUMXePkAYIxEQ0mMc8Po7tuXdejgPMwgP7x65xtfEqI0RuzbUioFltsp1jUaRwQZ MTsCeQDdjpgHsj+P2ZDeEKCbma4m6Ez/YWs4+zDm1X8uZDkZcfQlD9NldbKDJEXLIjYWo1PH hYepSffIWPyvBMBTW2W5FRjJ4vLRrJSUoEfJuPQ3vW9Y73foyo/qFoURHO48AinGPZ7PC7TF vUaNOTjKedrqHkaOcqB185ahG2had0xnFsDPlx5y In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/29/24 12:26, Kirill A. Shutemov wrote: >>> Do we care? >> I want to make sure I understand the scenario: >> >> 1. We're running in a guest under TDX (or SEV-SNP) >> 2. The VMM (or somebody) is attacking the guest by eating all the >> hardware entropy and RDRAND is effectively busted >> 3. Assuming kernel-based panic_on_warn and WARN_ON() rdrand_long() >> failure, that rdrand_long() never gets called. > Never gets called during attack. It can be used before and after. > >> 4. Userspace is using RDRAND output in some critical place like key >> generation and is not checking it for failure, nor mixing it with >> entropy from any other source >> 5. Userspace uses the failed RDRAND output to generate a key >> 6. Someone exploits the horrible key >> >> Is that it? > Yes. Is there something that fundamentally makes this a VMM vs. TDX guest problem? If a malicious VMM can exhaust RDRAND, why can't malicious userspace do the same? Let's assume buggy userspace exists. Is that userspace *uniquely* exposed to a naughty VMM or is that VMM just added to the list of things that can attack buggy userspace?