From patchwork Thu Sep 22 15:28:47 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 12985473 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.gnu.org (lists.gnu.org [209.51.188.17]) (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 E85DEC6FA91 for ; Thu, 22 Sep 2022 15:55:35 +0000 (UTC) Received: from localhost ([::1]:39354 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1obOY1-000092-GF for qemu-devel@archiver.kernel.org; Thu, 22 Sep 2022 11:55:33 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:51614) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1obO8O-0001pZ-OF for qemu-devel@nongnu.org; Thu, 22 Sep 2022 11:29:05 -0400 Received: from ams.source.kernel.org ([145.40.68.75]:45364) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1obO8M-00065h-Nj for qemu-devel@nongnu.org; Thu, 22 Sep 2022 11:29:04 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id A7076B83877; Thu, 22 Sep 2022 15:29:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0DF86C433D6; Thu, 22 Sep 2022 15:28:58 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="mo3fnyyS" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1663860536; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=mgvOqEV2xm4TSx4tHkD6FTczT22w2CRk/X4Jy1Z9LbY=; b=mo3fnyySHFvmGx0jWo3+FOgaJ5qfct70cApo9gvVLi1To/7DEvbPABp4LLn+Vqw13wNF1d Z/0Xs4e36B66c3VRVP/In/jXqP2GSBO3nOl5aS7vD8wmPU4RvNFZ5xJ69dfZ9Cs94lBQT6 eG7Lq/a9vNyxAI4mReZn2aqjRvlez0M= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 91ba5763 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Thu, 22 Sep 2022 15:28:56 +0000 (UTC) From: "Jason A. Donenfeld" To: qemu-devel@nongnu.org, pbonzini@redhat.com Cc: "Jason A. Donenfeld" Subject: [PATCH] x86: re-initialize RNG seed when selecting kernel Date: Thu, 22 Sep 2022 17:28:47 +0200 Message-Id: <20220922152847.3670513-1-Jason@zx2c4.com> MIME-Version: 1.0 Received-SPF: pass client-ip=145.40.68.75; envelope-from=SRS0=dGS3=ZZ=zx2c4.com=Jason@kernel.org; helo=ams.source.kernel.org X-Spam_score_int: -67 X-Spam_score: -6.8 X-Spam_bar: ------ X-Spam_report: (-6.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HEADER_FROM_DIFFERENT_DOMAINS=0.25, RCVD_IN_DNSWL_HI=-5, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" We don't want it to be possible to re-read the RNG seed after ingesting it, because this ruins forward secrecy. Currently, however, the setup data section can just be re-read. Since the kernel is always read after the setup data, use the selection of the kernel as a trigger to re-initialize the RNG seed, just like we do on reboot, to preserve forward secrecy. Cc: Paolo Bonzini Signed-off-by: Jason A. Donenfeld --- Paolo- this applies on top of the 4 you merged this morning. -Jason hw/i386/x86.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/hw/i386/x86.c b/hw/i386/x86.c index f9a4ddaa4a..1148f70c03 100644 --- a/hw/i386/x86.c +++ b/hw/i386/x86.c @@ -1112,11 +1112,14 @@ void x86_load_linux(X86MachineState *x86ms, setup_data->len = cpu_to_le32(RNG_SEED_LENGTH); qemu_guest_getrandom_nofail(setup_data->data, RNG_SEED_LENGTH); qemu_register_reset(reset_rng_seed, setup_data); + fw_cfg_add_bytes_callback(fw_cfg, FW_CFG_KERNEL_DATA, reset_rng_seed, NULL, + setup_data, kernel, kernel_size, true); + } else { + fw_cfg_add_bytes(fw_cfg, FW_CFG_KERNEL_DATA, kernel, kernel_size); } fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_ADDR, prot_addr); fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_SIZE, kernel_size); - fw_cfg_add_bytes(fw_cfg, FW_CFG_KERNEL_DATA, kernel, kernel_size); sev_load_ctx.kernel_data = (char *)kernel; sev_load_ctx.kernel_size = kernel_size;