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.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 6A2C8C433EF for ; Fri, 25 Feb 2022 10:58:22 +0000 (UTC) Received: from localhost ([::1]:49646 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nNYIn-0001lA-Dc for qemu-devel@archiver.kernel.org; Fri, 25 Feb 2022 05:58:21 -0500 Received: from eggs.gnu.org ([209.51.188.92]:52376) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nNXzz-0005ce-RY for qemu-devel@nongnu.org; Fri, 25 Feb 2022 05:38:58 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:47354) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nNXzw-0001DN-H1 for qemu-devel@nongnu.org; Fri, 25 Feb 2022 05:38:55 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1645785520; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Ait68bCLPZgU08GUtkMsgL4AE3KFDcmnrVIdep4pyvw=; b=gtMiEhf7dBm1sBYjLvg8jPe4huFHlOe8W24/k4ZCX6rtY5bBB1AuZ3sjJcO8lWB6X2T36U 9oOZOXZlrs+uh7+oaU8bg9bPDiVmKywi92CWpHCv3jOPul/bfrORhaTPrFiPLV7rOUEiMo ZGcU2yEwtl4eXUU5a8A8CHHnLMcTvtc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-79-7gF6m_XaN0CepHs2oHvxdg-1; Fri, 25 Feb 2022 05:38:36 -0500 X-MC-Unique: 7gF6m_XaN0CepHs2oHvxdg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 71716180FD73; Fri, 25 Feb 2022 10:38:33 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (unknown [10.39.193.171]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3FD841053B16; Fri, 25 Feb 2022 10:37:52 +0000 (UTC) Subject: Re: [PATCH v3 2/2] virt: vmgenid: introduce driver for reinitializing RNG on VM fork To: "Jason A. Donenfeld" , linux-hyperv@vger.kernel.org, kvm@vger.kernel.org, linux-crypto@vger.kernel.org, qemu-devel@nongnu.org, linux-kernel@vger.kernel.org References: <20220224133906.751587-1-Jason@zx2c4.com> <20220224133906.751587-3-Jason@zx2c4.com> From: Laszlo Ersek Message-ID: Date: Fri, 25 Feb 2022 11:37:51 +0100 MIME-Version: 1.0 In-Reply-To: <20220224133906.751587-3-Jason@zx2c4.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Received-SPF: pass client-ip=170.10.129.124; envelope-from=lersek@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: , Cc: wei.liu@kernel.org, kys@microsoft.com, berrange@redhat.com, ehabkost@redhat.com, adrian@parity.io, mst@redhat.com, decui@microsoft.com, haiyangz@microsoft.com, ben@skyportsystems.com, raduweis@amazon.com, jannh@google.com, linux@dominikbrodowski.net, ebiggers@kernel.org, graf@amazon.com, tytso@mit.edu, gregkh@linuxfoundation.org, imammedo@redhat.com, colmmacc@amazon.com, sthemmin@microsoft.com, ardb@kernel.org, dwmw@amazon.co.uk Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 02/24/22 14:39, Jason A. Donenfeld wrote: > VM Generation ID is a feature from Microsoft, described at > , and supported by > Hyper-V and QEMU. Its usage is described in Microsoft's RNG whitepaper, > , as: > > If the OS is running in a VM, there is a problem that most > hypervisors can snapshot the state of the machine and later rewind > the VM state to the saved state. This results in the machine running > a second time with the exact same RNG state, which leads to serious > security problems. To reduce the window of vulnerability, Windows > 10 on a Hyper-V VM will detect when the VM state is reset, retrieve > a unique (not random) value from the hypervisor, and reseed the root > RNG with that unique value. This does not eliminate the > vulnerability, but it greatly reduces the time during which the RNG > system will produce the same outputs as it did during a previous > instantiation of the same VM state. > > Linux has the same issue, and given that vmgenid is supported already by > multiple hypervisors, we can implement more or less the same solution. > So this commit wires up the vmgenid ACPI notification to the RNG's newly > added add_vmfork_randomness() function. > > It can be used from qemu via the `-device vmgenid,guid=auto` parameter. > After setting that, use `savevm` in the monitor to save the VM state, > then quit QEMU, start it again, and use `loadvm`. That will trigger this > driver's notify function, which hands the new UUID to the RNG. This is > described in . > And there are hooks for this in libvirt as well, described in > . > > Note, however, that the treatment of this as a UUID is considered to be > an accidental QEMU nuance, per > , > so this driver simply treats these bytes as an opaque 128-bit binary > blob, as per the spec. This doesn't really make a difference anyway, > considering that's how it ends up when handed to the RNG in the end. > > This driver builds on prior work from Adrian Catangiu at Amazon, and it > is my hope that that team can resume maintenance of this driver. > > Cc: Adrian Catangiu > Cc: Laszlo Ersek > Cc: Daniel P. Berrangé > Cc: Dominik Brodowski > Cc: Ard Biesheuvel > Signed-off-by: Jason A. Donenfeld > --- > drivers/virt/Kconfig | 9 +++ > drivers/virt/Makefile | 1 + > drivers/virt/vmgenid.c | 121 +++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 131 insertions(+) > create mode 100644 drivers/virt/vmgenid.c > > diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig > index 8061e8ef449f..d3276dc2095c 100644 > --- a/drivers/virt/Kconfig > +++ b/drivers/virt/Kconfig > @@ -13,6 +13,15 @@ menuconfig VIRT_DRIVERS > > if VIRT_DRIVERS > > +config VMGENID > + tristate "Virtual Machine Generation ID driver" > + default y > + depends on ACPI > + help > + Say Y here to use the hypervisor-provided Virtual Machine Generation ID > + to reseed the RNG when the VM is cloned. This is highly recommended if > + you intend to do any rollback / cloning / snapshotting of VMs. > + > config FSL_HV_MANAGER > tristate "Freescale hypervisor management driver" > depends on FSL_SOC > diff --git a/drivers/virt/Makefile b/drivers/virt/Makefile > index 3e272ea60cd9..108d0ffcc9aa 100644 > --- a/drivers/virt/Makefile > +++ b/drivers/virt/Makefile > @@ -4,6 +4,7 @@ > # > > obj-$(CONFIG_FSL_HV_MANAGER) += fsl_hypervisor.o > +obj-$(CONFIG_VMGENID) += vmgenid.o > obj-y += vboxguest/ > > obj-$(CONFIG_NITRO_ENCLAVES) += nitro_enclaves/ > diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c > new file mode 100644 > index 000000000000..5da4dc8f25e3 > --- /dev/null > +++ b/drivers/virt/vmgenid.c > @@ -0,0 +1,121 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Virtual Machine Generation ID driver > + * > + * Copyright (C) 2022 Jason A. Donenfeld . All Rights Reserved. > + * Copyright (C) 2020 Amazon. All rights reserved. > + * Copyright (C) 2018 Red Hat Inc. All rights reserved. > + */ > + > +#include > +#include > +#include > +#include > + > +ACPI_MODULE_NAME("vmgenid"); > + > +enum { VMGENID_SIZE = 16 }; > + > +static struct { > + u8 this_id[VMGENID_SIZE]; > + u8 *next_id; > +} state; > + > +static int vmgenid_acpi_add(struct acpi_device *device) > +{ > + struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER }; > + union acpi_object *pss; > + phys_addr_t phys_addr; > + acpi_status status; > + int ret = 0; > + > + if (!device) > + return -EINVAL; > + > + status = acpi_evaluate_object(device->handle, "ADDR", NULL, &buffer); > + if (ACPI_FAILURE(status)) { > + ACPI_EXCEPTION((AE_INFO, status, "Evaluating ADDR")); > + return -ENODEV; > + } > + pss = buffer.pointer; > + if (!pss || pss->type != ACPI_TYPE_PACKAGE || pss->package.count != 2 || > + pss->package.elements[0].type != ACPI_TYPE_INTEGER || > + pss->package.elements[1].type != ACPI_TYPE_INTEGER) { > + ret = -EINVAL; > + goto out; > + } > + > + phys_addr = (pss->package.elements[0].integer.value << 0) | > + (pss->package.elements[1].integer.value << 32); > + state.next_id = acpi_os_map_memory(phys_addr, VMGENID_SIZE); > + if (!state.next_id) { > + ret = -ENOMEM; > + goto out; > + } > + device->driver_data = &state; > + > + memcpy(state.this_id, state.next_id, sizeof(state.this_id)); > + add_device_randomness(state.this_id, sizeof(state.this_id)); > + > +out: > + ACPI_FREE(buffer.pointer); > + return ret; > +} > + > +static int vmgenid_acpi_remove(struct acpi_device *device) > +{ > + if (!device || acpi_driver_data(device) != &state) > + return -EINVAL; > + device->driver_data = NULL; > + if (state.next_id) > + acpi_os_unmap_memory(state.next_id, VMGENID_SIZE); > + state.next_id = NULL; > + return 0; > +} > + > +static void vmgenid_acpi_notify(struct acpi_device *device, u32 event) > +{ > + u8 old_id[VMGENID_SIZE]; > + > + if (!device || acpi_driver_data(device) != &state) > + return; > + memcpy(old_id, state.this_id, sizeof(old_id)); > + memcpy(state.this_id, state.next_id, sizeof(state.this_id)); > + if (!memcmp(old_id, state.this_id, sizeof(old_id))) > + return; > + add_vmfork_randomness(state.this_id, sizeof(state.this_id)); > +} > + > +static const struct acpi_device_id vmgenid_ids[] = { > + {"VMGENID", 0}, > + {"QEMUVGID", 0}, > + { }, > +}; > + > +static struct acpi_driver acpi_driver = { > + .name = "vm_generation_id", > + .ids = vmgenid_ids, > + .owner = THIS_MODULE, > + .ops = { > + .add = vmgenid_acpi_add, > + .remove = vmgenid_acpi_remove, > + .notify = vmgenid_acpi_notify, > + } > +}; > + > +static int __init vmgenid_init(void) > +{ > + return acpi_bus_register_driver(&acpi_driver); > +} > + > +static void __exit vmgenid_exit(void) > +{ > + acpi_bus_unregister_driver(&acpi_driver); > +} > + > +module_init(vmgenid_init); > +module_exit(vmgenid_exit); > + > +MODULE_DEVICE_TABLE(acpi, vmgenid_ids); > +MODULE_DESCRIPTION("Virtual Machine Generation ID"); > +MODULE_LICENSE("GPL v2"); > I'm not an experienced reviewer for the kernel. I've made an effort to check several -- although not all -- aspects of this patch, and it looks OK to me. Reviewed-by: Laszlo Ersek Thanks Laszlo