From patchwork Wed Feb 23 13:12:30 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: 12756902 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8B599C433FE for ; Wed, 23 Feb 2022 13:13:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240773AbiBWNNc (ORCPT ); Wed, 23 Feb 2022 08:13:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35758 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240755AbiBWNN2 (ORCPT ); Wed, 23 Feb 2022 08:13:28 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4F143A994E; Wed, 23 Feb 2022 05:13:00 -0800 (PST) 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 F2C5FB81F9D; Wed, 23 Feb 2022 13:12:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0AAE5C340EB; Wed, 23 Feb 2022 13:12:55 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="hm90A+4f" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1645621975; 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: in-reply-to:in-reply-to:references:references; bh=tyY2HOAHKsoDLSNU4qhPTpE77sJsVX4J6vRZHKCspPA=; b=hm90A+4fdTE041NEWb7wQAZIrHImYAp8Mw/P/V+8TLwdVW6Auj6cy8OHEHQrNYSQKEp0zg BkC+68f6gszTlE1MbBpe3aHgDMuwh3dmA9cr1eVnCyz8xb4aBsPGQPuua9twOIu5MAat6/ n+EI5IPOXZYazoQ/PgnRGme5OaNxnjk= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 3b10fb2e (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Wed, 23 Feb 2022 13:12:55 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, qemu-devel@nongnu.org, kvm@vger.kernel.org, linux-s390@vger.kernel.org, adrian@parity.io Cc: "Jason A. Donenfeld" , dwmw@amazon.co.uk, acatan@amazon.com, graf@amazon.com, colmmacc@amazon.com, sblbir@amazon.com, raduweis@amazon.com, jannh@google.com, gregkh@linuxfoundation.org, tytso@mit.edu Subject: [PATCH RFC v1 1/2] random: add mechanism for VM forks to reinitialize crng Date: Wed, 23 Feb 2022 14:12:30 +0100 Message-Id: <20220223131231.403386-2-Jason@zx2c4.com> In-Reply-To: <20220223131231.403386-1-Jason@zx2c4.com> References: <20220223131231.403386-1-Jason@zx2c4.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org When a VM forks, we must immediately mix in additional information to the stream of random output so that two forks or a rollback don't produce the same stream of random numbers, which could have catastrophic cryptographic consequences. This commit adds a simple API, add_vmfork_ randomness(), for that. Cc: Theodore Ts'o Cc: Jann Horn Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 58 ++++++++++++++++++++++++++++++++++++++++++ include/linux/random.h | 1 + 2 files changed, 59 insertions(+) diff --git a/drivers/char/random.c b/drivers/char/random.c index 536237a0f073..29d6ce484d15 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -344,6 +344,46 @@ static void crng_reseed(void) } } +/* + * This mixes unique_vm_id directly into the base_crng key as soon as + * possible, similarly to crng_pre_init_inject(), even if the crng is + * already running, in order to immediately branch streams from prior + * VM instances. + */ +static void crng_vm_fork_inject(const void *unique_vm_id, size_t len) +{ + unsigned long flags, next_gen; + struct blake2s_state hash; + + /* + * Unlike crng_reseed(), we take the lock as early as possible, + * since we don't want the RNG to be used until it's updated. + */ + spin_lock_irqsave(&base_crng.lock, flags); + + /* + * Also update the generation, while locked, as early as + * possible. This will mean unlocked reads of the generation + * will cause a reseeding of per-cpu crngs, and those will + * spin on the base_crng lock waiting for the rest of this + * operation to complete, which achieves the goal of blocking + * the production of new output until this is done. + */ + next_gen = base_crng.generation + 1; + if (next_gen == ULONG_MAX) + ++next_gen; + WRITE_ONCE(base_crng.generation, next_gen); + WRITE_ONCE(base_crng.birth, jiffies); + + /* This is the same formulation used by crng_pre_init_inject(). */ + blake2s_init(&hash, sizeof(base_crng.key)); + blake2s_update(&hash, base_crng.key, sizeof(base_crng.key)); + blake2s_update(&hash, unique_vm_id, len); + blake2s_final(&hash, base_crng.key); + + spin_unlock_irqrestore(&base_crng.lock, flags); +} + /* * This generates a ChaCha block using the provided key, and then * immediately overwites that key with half the block. It returns @@ -935,6 +975,7 @@ static bool drain_entropy(void *buf, size_t nbytes) * void add_hwgenerator_randomness(const void *buffer, size_t count, * size_t entropy); * void add_bootloader_randomness(const void *buf, size_t size); + * void add_vmfork_randomness(const void *unique_vm_id, size_t size); * void add_interrupt_randomness(int irq); * * add_device_randomness() adds data to the input pool that @@ -966,6 +1007,11 @@ static bool drain_entropy(void *buf, size_t nbytes) * add_device_randomness(), depending on whether or not the configuration * option CONFIG_RANDOM_TRUST_BOOTLOADER is set. * + * add_vmfork_randomness() adds a unique (but not neccessarily secret) ID + * representing the current instance of a VM to the pool, without crediting, + * and then immediately mixes that ID into the current base_crng key, so + * that it takes effect prior to a reseeding. + * * add_interrupt_randomness() uses the interrupt timing as random * inputs to the entropy pool. Using the cycle counters and the irq source * as inputs, it feeds the input pool roughly once a second or after 64 @@ -1195,6 +1241,18 @@ void add_bootloader_randomness(const void *buf, size_t size) } EXPORT_SYMBOL_GPL(add_bootloader_randomness); +/* + * Handle a new unique VM ID, which is unique, not secret, so we + * don't credit it, but we do mix it into the entropy pool and + * inject it into the crng. + */ +void add_vmfork_randomness(const void *unique_vm_id, size_t size) +{ + add_device_randomness(unique_vm_id, size); + crng_vm_fork_inject(unique_vm_id, size); +} +EXPORT_SYMBOL_GPL(add_vmfork_randomness); + struct fast_pool { union { u32 pool32[4]; diff --git a/include/linux/random.h b/include/linux/random.h index 6148b8d1ccf3..51b8ed797732 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -34,6 +34,7 @@ extern void add_input_randomness(unsigned int type, unsigned int code, extern void add_interrupt_randomness(int irq) __latent_entropy; extern void add_hwgenerator_randomness(const void *buffer, size_t count, size_t entropy); +extern void add_vmfork_randomness(const void *unique_vm_id, size_t size); extern void get_random_bytes(void *buf, size_t nbytes); extern int wait_for_random_bytes(void); From patchwork Wed Feb 23 13:12:31 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: 12756903 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 36E49C4332F for ; Wed, 23 Feb 2022 13:13:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240780AbiBWNNg (ORCPT ); Wed, 23 Feb 2022 08:13:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240779AbiBWNNe (ORCPT ); Wed, 23 Feb 2022 08:13:34 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 84D5AA9A61; Wed, 23 Feb 2022 05:13:04 -0800 (PST) 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 C63FAB81FA1; Wed, 23 Feb 2022 13:13:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D8155C340E7; Wed, 23 Feb 2022 13:12:59 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="kP/TNLRo" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1645621979; 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: in-reply-to:in-reply-to:references:references; bh=lgLtq+lfYFesl4+M3nDQfreFYpTzpLlZU30SsFv1B9I=; b=kP/TNLRoQCYE16+kAQxyXUKZW27z79tNX+j9khdmnW/pHUrLp5TsQg+Sst5dY0RUvma5Mv bQflcE8AP3p/qcnEe0Ytn5tTaN6qKbYLfiX7li7x4NV/wK5zU/k/H2vnZMaPw50Tc8hoNc F6CVnKlFZJXSeHIRZPpAohvSylF0vbk= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 25ac14b1 (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Wed, 23 Feb 2022 13:12:58 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, qemu-devel@nongnu.org, kvm@vger.kernel.org, linux-s390@vger.kernel.org, adrian@parity.io Cc: "Jason A. Donenfeld" , dwmw@amazon.co.uk, acatan@amazon.com, graf@amazon.com, colmmacc@amazon.com, sblbir@amazon.com, raduweis@amazon.com, jannh@google.com, gregkh@linuxfoundation.org, tytso@mit.edu Subject: [PATCH RFC v1 2/2] drivers/virt: add vmgenid driver for reinitializing RNG Date: Wed, 23 Feb 2022 14:12:31 +0100 Message-Id: <20220223131231.403386-3-Jason@zx2c4.com> In-Reply-To: <20220223131231.403386-1-Jason@zx2c4.com> References: <20220223131231.403386-1-Jason@zx2c4.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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. 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 Signed-off-by: Jason A. Donenfeld --- drivers/virt/Kconfig | 8 +++ drivers/virt/Makefile | 1 + drivers/virt/vmgenid.c | 133 +++++++++++++++++++++++++++++++++++++++++ 3 files changed, 142 insertions(+) create mode 100644 drivers/virt/vmgenid.c diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig index 8061e8ef449f..e7f9c1bca02b 100644 --- a/drivers/virt/Kconfig +++ b/drivers/virt/Kconfig @@ -13,6 +13,14 @@ menuconfig VIRT_DRIVERS if VIRT_DRIVERS +config VMGENID + bool "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. + 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..11ed7f668bb1 --- /dev/null +++ b/drivers/virt/vmgenid.c @@ -0,0 +1,133 @@ +// 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. + */ + +#define pr_fmt(fmt) "vmgenid: " fmt + +#include +#include +#include +#include +#include + +#define DEV_NAME "vmgenid" +ACPI_MODULE_NAME(DEV_NAME); + +static struct { + uuid_t uuid; + void *uuid_iomap; +} vmgenid_data; + +static int vmgenid_acpi_map(acpi_handle handle) +{ + phys_addr_t phys_addr = 0; + struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL }; + acpi_status status; + union acpi_object *pss; + union acpi_object *element; + int i; + + status = acpi_evaluate_object(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) + return -EINVAL; + + for (i = 0; i < pss->package.count; ++i) { + element = &pss->package.elements[i]; + if (element->type != ACPI_TYPE_INTEGER) + return -EINVAL; + phys_addr |= element->integer.value << i * 32; + } + + vmgenid_data.uuid_iomap = acpi_os_map_memory(phys_addr, sizeof(vmgenid_data.uuid)); + if (!vmgenid_data.uuid_iomap) { + pr_err("failed to map memory at %pa, size %zu\n", + &phys_addr, sizeof(vmgenid_data.uuid)); + return -ENOMEM; + } + + memcpy_fromio(&vmgenid_data.uuid, vmgenid_data.uuid_iomap, sizeof(vmgenid_data.uuid)); + + return 0; +} + +static int vmgenid_acpi_add(struct acpi_device *device) +{ + int ret; + + if (!device) + return -EINVAL; + ret = vmgenid_acpi_map(device->handle); + if (ret < 0) { + pr_err("failed to map acpi device: %d\n", ret); + return ret; + } + device->driver_data = &vmgenid_data; + add_device_randomness(&vmgenid_data.uuid, sizeof(vmgenid_data.uuid)); + return 0; +} + +static int vmgenid_acpi_remove(struct acpi_device *device) +{ + if (!device || acpi_driver_data(device) != &vmgenid_data) + return -EINVAL; + device->driver_data = NULL; + if (vmgenid_data.uuid_iomap) + acpi_os_unmap_memory(vmgenid_data.uuid_iomap, sizeof(vmgenid_data.uuid)); + vmgenid_data.uuid_iomap = NULL; + return 0; +} + +static void vmgenid_acpi_notify(struct acpi_device *device, u32 event) +{ + uuid_t old_uuid = vmgenid_data.uuid; + + if (!device || acpi_driver_data(device) != &vmgenid_data) + return; + memcpy_fromio(&vmgenid_data.uuid, vmgenid_data.uuid_iomap, sizeof(vmgenid_data.uuid)); + if (!memcmp(&old_uuid, &vmgenid_data.uuid, sizeof(vmgenid_data.uuid))) + return; + add_vmfork_randomness(&vmgenid_data.uuid, sizeof(vmgenid_data.uuid)); +} + +static const struct acpi_device_id vmgenid_ids[] = { + {"VMGENID", 0}, + {"QEMUVGID", 0}, + {"", 0}, +}; + +static struct acpi_driver acpi_vmgenid_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_vmgenid_driver); +} + +static void __exit vmgenid_exit(void) +{ + acpi_bus_unregister_driver(&acpi_vmgenid_driver); +} + +module_init(vmgenid_init); +module_exit(vmgenid_exit); + +MODULE_DESCRIPTION("Virtual Machine Generation ID"); +MODULE_LICENSE("GPL");