When running Linux inside a Nitro Enclave, the hypervisor provides a special virtio device called "NSM". This device has 2 main functions: 1) Provide attestation reports 2) Modify PCR state 3) Provide entropy This patch adds the core NSM driver that exposes a /dev/nsm device node which user space can use to request attestation documents and influence PCR states. A follow up patch will add a hwrng driver to feed its entropy into the kernel. Originally-by: Petre Eftime <petre.eftime@xxxxxxxxx> Signed-off-by: Alexander Graf <graf@xxxxxxxxxx> --- v1 -> v2: - Remove boilerplate - Add uapi header v2 -> v3: - Move globals to device struct - Add compat handling - Simplify some naming - Remove debug prints - Use module_virtio_driver - Drop use of uio.h --- MAINTAINERS | 10 + drivers/misc/Kconfig | 11 + drivers/misc/Makefile | 1 + drivers/misc/nsm.c | 423 +++++++++++++++++++++++++++++++++++++++ include/linux/nsm.h | 35 ++++ include/uapi/linux/nsm.h | 29 +++ 6 files changed, 509 insertions(+) create mode 100644 drivers/misc/nsm.c create mode 100644 include/linux/nsm.h create mode 100644 include/uapi/linux/nsm.h diff --git a/MAINTAINERS b/MAINTAINERS index b19995690904..d54bf3ea2b9d 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -15098,6 +15098,16 @@ F: include/linux/nitro_enclaves.h F: include/uapi/linux/nitro_enclaves.h F: samples/nitro_enclaves/ +NITRO SECURE MODULE (NSM) +M: Alexander Graf <graf@xxxxxxxxxx> +L: linux-kernel@xxxxxxxxxxxxxxx +L: The AWS Nitro Enclaves Team <aws-nitro-enclaves-devel@xxxxxxxxxx> +S: Supported +W: https://aws.amazon.com/ec2/nitro/nitro-enclaves/ +F: drivers/misc/nsm.c +F: include/linux/nsm.h +F: include/uapi/linux/nsm.h + NOHZ, DYNTICKS SUPPORT M: Frederic Weisbecker <frederic@xxxxxxxxxx> M: Thomas Gleixner <tglx@xxxxxxxxxxxxx> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig index cadd4a820c03..7b1ed309d469 100644 --- a/drivers/misc/Kconfig +++ b/drivers/misc/Kconfig @@ -562,6 +562,17 @@ config TPS6594_PFSM This driver can also be built as a module. If so, the module will be called tps6594-pfsm. +config NSM + tristate "Nitro (Enclaves) Security Module support" + depends on VIRTIO + help + This driver provides support for the Nitro Security Module + in AWS EC2 Nitro based Enclaves. The driver exposes a /dev/nsm + device user space can use to communicate with the hypervisor. + + To compile this driver as a module, choose M here. + The module will be called nsm. + source "drivers/misc/c2port/Kconfig" source "drivers/misc/eeprom/Kconfig" source "drivers/misc/cb710/Kconfig" diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile index f2a4d1ff65d4..ea6ea5bbbc9c 100644 --- a/drivers/misc/Makefile +++ b/drivers/misc/Makefile @@ -67,3 +67,4 @@ obj-$(CONFIG_TMR_MANAGER) += xilinx_tmr_manager.o obj-$(CONFIG_TMR_INJECT) += xilinx_tmr_inject.o obj-$(CONFIG_TPS6594_ESM) += tps6594-esm.o obj-$(CONFIG_TPS6594_PFSM) += tps6594-pfsm.o +obj-$(CONFIG_NSM) += nsm.o diff --git a/drivers/misc/nsm.c b/drivers/misc/nsm.c new file mode 100644 index 000000000000..c4fd072babdf --- /dev/null +++ b/drivers/misc/nsm.c @@ -0,0 +1,423 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Amazon Nitro Secure Module driver. + * + * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved. + */ + +#include <linux/nsm.h> +#include <linux/file.h> +#include <linux/fs.h> +#include <linux/interrupt.h> +#include <linux/miscdevice.h> +#include <linux/module.h> +#include <linux/mutex.h> +#include <linux/slab.h> +#include <linux/string.h> +#include <linux/uaccess.h> +#include <linux/uio.h> +#include <linux/virtio_config.h> +#include <linux/virtio_ids.h> +#include <linux/wait.h> +#include <uapi/linux/nsm.h> + +#define NSM_REQUEST_MAX_SIZE 0x1000 +#define NSM_RESPONSE_MAX_SIZE 0x3000 + +/* Timeout for NSM virtqueue respose in milliseconds. */ +#define NSM_DEFAULT_TIMEOUT_MSECS (120000) /* 2 minutes */ + +struct nsm { + struct list_head node; + struct virtio_device *vdev; + struct virtqueue *vq; + struct mutex lock; + wait_queue_head_t wq; + bool device_notified; + struct miscdevice misc; +}; + +/* NSM device ID */ +static const struct virtio_device_id id_table[] = { + { VIRTIO_ID_NITRO_SEC_MOD, VIRTIO_DEV_ANY_ID }, + { 0 }, +}; + +/* + * We want to support nsm_rng, but not link the modules. So we create this + * intermediate layer to allow the rng driver to register lazily into us. + */ +static struct nsm_hwrng *nsm_hwrng; + +/* + * The rng driver can probe at any time, even after we already finished + * initializing all nsm devices. Keep a list of all devices around so that + * we can establish the link dynamically + */ +static LIST_HEAD(nsm_devices); + +static inline struct nsm *to_nsm(struct file *file) +{ + return container_of(file->private_data, struct nsm, misc); +} + +/* Copy an entire message from user-space to kernel-space */ +static int message_memdup_from_user(struct nsm_kernel_message *dst, u64 src_addr) +{ + struct nsm_message shallow_copy; + + if (!src_addr || !dst) + return -EINVAL; + + /* The destination's request and response buffers should be NULL. */ + if (dst->request.iov_base || dst->response.iov_base) + return -EINVAL; + + /* First, make a shallow copy to be able to read the inner pointers */ + if (copy_from_user(&shallow_copy, u64_to_user_ptr(src_addr), + sizeof(shallow_copy)) != 0) + return -EINVAL; + + /* Verify the user input size. */ + if (shallow_copy.request.len > NSM_REQUEST_MAX_SIZE) + return -EMSGSIZE; + + /* Allocate kernel memory for the user request */ + dst->request.iov_len = shallow_copy.request.len; + dst->request.iov_base = kmalloc(dst->request.iov_len, GFP_KERNEL); + if (!dst->request.iov_base) + return -ENOMEM; + + /* Copy the request content */ + if (copy_from_user(dst->request.iov_base, + u64_to_user_ptr(shallow_copy.request.addr), + dst->request.iov_len) != 0) { + kfree(dst->request.iov_base); + return -EFAULT; + } + + /* Allocate kernel memory for the response, up to a fixed limit */ + dst->response.iov_len = shallow_copy.response.len; + if (dst->response.iov_len > NSM_RESPONSE_MAX_SIZE) + dst->response.iov_len = NSM_RESPONSE_MAX_SIZE; + + dst->response.iov_base = kmalloc(dst->response.iov_len, GFP_KERNEL); + if (!dst->response.iov_base) { + kfree(dst->request.iov_base); + return -ENOMEM; + } + + return 0; +} + +/* Copy a message back to user-space */ +static int message_copy_to_user(u64 user_addr, struct nsm_kernel_message *kern_msg) +{ + struct nsm_message shallow_copy; + + if (!kern_msg || !user_addr) + return -EINVAL; + + /* + * First, do a shallow copy of the user-space message. This is needed in + * order to get the request block data, which we do not need to copy but + * must preserve in the message sent back to user-space. + */ + if (copy_from_user(&shallow_copy, u64_to_user_ptr(user_addr), + sizeof(shallow_copy)) != 0) + return -EINVAL; + + /* Do not exceed the capacity of the user-provided response buffer */ + shallow_copy.response.len = kern_msg->response.iov_len; + + /* Only the response content must be copied back to user-space */ + if (copy_to_user(u64_to_user_ptr(shallow_copy.response.addr), + kern_msg->response.iov_base, + shallow_copy.response.len) != 0) + return -EINVAL; + + if (copy_to_user(u64_to_user_ptr(user_addr), &shallow_copy, + sizeof(shallow_copy)) != 0) + return -EFAULT; + + return 0; +} + +/* Virtqueue interrupt handler */ +static void nsm_vq_callback(struct virtqueue *vq) +{ + struct nsm *nsm = vq->vdev->priv; + + nsm->device_notified = true; + wake_up(&nsm->wq); +} + +/* Forward a message to the NSM device and wait for the response from it */ +int nsm_communicate_with_device(struct virtio_device *vdev, + struct nsm_kernel_message *message) +{ + struct nsm *nsm = vdev->priv; + struct virtqueue *vq = nsm->vq; + struct scatterlist sg_in, sg_out; + unsigned int len; + void *queue_buf; + bool kicked; + int rc; + + if (!vdev) + return -EINVAL; + + if (!message) + return -EINVAL; + + /* Verify if buffer memory is valid. */ + if (!virt_addr_valid(message->request.iov_base) || + !virt_addr_valid(((u8 *)message->request.iov_base) + + message->request.iov_len - 1) || + !virt_addr_valid(message->response.iov_base) || + !virt_addr_valid(((u8 *)message->response.iov_base) + + message->response.iov_len - 1)) + return -EINVAL; + + /* Initialize scatter-gather lists with request and response buffers. */ + sg_init_one(&sg_out, message->request.iov_base, + message->request.iov_len); + sg_init_one(&sg_in, message->response.iov_base, + message->response.iov_len); + + mutex_lock(&nsm->lock); + + /* Add the request buffer (read by the device). */ + rc = virtqueue_add_outbuf(vq, &sg_out, 1, message->request.iov_base, + GFP_KERNEL); + if (rc) { + mutex_unlock(&nsm->lock); + return rc; + } + + /* Add the response buffer (written by the device). */ + rc = virtqueue_add_inbuf(vq, &sg_in, 1, message->response.iov_base, + GFP_KERNEL); + if (rc) + goto cleanup; + + nsm->device_notified = false; + kicked = virtqueue_kick(vq); + if (!kicked) { + /* Cannot kick the virtqueue. */ + rc = -EIO; + goto cleanup; + } + + /* If the kick succeeded, wait for the device's response. */ + rc = wait_event_timeout(nsm->wq, + nsm->device_notified == true, + msecs_to_jiffies(NSM_DEFAULT_TIMEOUT_MSECS)); + if (!rc) { + rc = -ETIMEDOUT; + goto cleanup; + } + + queue_buf = virtqueue_get_buf(vq, &len); + if (!queue_buf || (queue_buf != message->request.iov_base)) { + pr_err("NSM device received wrong request buffer."); + rc = -ENODATA; + goto cleanup; + } + + queue_buf = virtqueue_get_buf(vq, &len); + if (!queue_buf || (queue_buf != message->response.iov_base)) { + pr_err("NSM device received wrong response buffer."); + rc = -ENODATA; + goto cleanup; + } + + /* Make sure the response length doesn't exceed the buffer capacity. */ + if (len < message->response.iov_len) + message->response.iov_len = len; + + rc = 0; + +cleanup: + if (rc) { + /* Clean the virtqueue. */ + while (virtqueue_get_buf(vq, &len) != NULL) + ; + } + + mutex_unlock(&nsm->lock); + return rc; +} +EXPORT_SYMBOL_GPL(nsm_communicate_with_device); + +static long nsm_dev_ioctl(struct file *file, unsigned int cmd, + unsigned long arg) +{ + struct nsm_kernel_message message = {}; + struct nsm *nsm = to_nsm(file); + int status = 0; + + if (cmd != NSM_IOCTL_REQUEST) + return -EINVAL; + + /* Copy the message from user-space to kernel-space */ + status = message_memdup_from_user(&message, arg); + if (status != 0) + return status; + + /* Communicate with the NSM device */ + status = nsm_communicate_with_device(nsm->vdev, &message); + + if (status != 0) + goto out; + + /* Copy the response back to user-space */ + status = message_copy_to_user(arg, &message); + +out: + /* At this point, everything succeeded, so clean up and finish. */ + kfree(message.request.iov_base); + kfree(message.response.iov_base); + + return status; +} + +static int nsm_dev_file_open(struct inode *node, struct file *file) +{ + return 0; +} + +static int nsm_dev_file_close(struct inode *inode, struct file *file) +{ + return 0; +} + +static int nsm_device_init_vq(struct virtio_device *vdev) +{ + struct virtqueue *vq = virtio_find_single_vq(vdev, + nsm_vq_callback, "nsm.vq.0"); + struct nsm *nsm = vdev->priv; + + if (IS_ERR(vq)) + return PTR_ERR(vq); + + nsm->vq = vq; + + return 0; +} + +static const struct file_operations nsm_dev_fops = { + .open = nsm_dev_file_open, + .release = nsm_dev_file_close, + .unlocked_ioctl = nsm_dev_ioctl, + .compat_ioctl = compat_ptr_ioctl, +}; + +/* Handler for probing the NSM device */ +static int nsm_device_probe(struct virtio_device *vdev) +{ + struct nsm *nsm; + int rc; + + nsm = kzalloc(sizeof(*nsm), GFP_KERNEL); + if (!nsm) + return -ENOMEM; + + vdev->priv = nsm; + nsm->vdev = vdev; + + rc = nsm_device_init_vq(vdev); + if (rc) { + pr_err("NSM device queue failed to initialize: %d.\n", rc); + goto err_init_vq; + } + + mutex_init(&nsm->lock); + init_waitqueue_head(&nsm->wq); + + nsm->misc = (struct miscdevice) { + .minor = MISC_DYNAMIC_MINOR, + .name = "nsm", + .fops = &nsm_dev_fops, + .mode = 0666 + }; + + rc = misc_register(&nsm->misc); + if (rc) { + pr_err("NSM misc device registration error: %d.\n", rc); + goto err_misc; + } + + if (nsm_hwrng) + nsm_hwrng->probe(vdev); + + list_add(&nsm->node, &nsm_devices); + + return 0; + +err_misc: + vdev->config->del_vqs(vdev); +err_init_vq: + kfree(nsm); + return rc; +} + +/* Handler for removing the NSM device */ +static void nsm_device_remove(struct virtio_device *vdev) +{ + struct nsm *nsm = vdev->priv; + + if (nsm_hwrng) + nsm_hwrng->remove(vdev); + + vdev->config->del_vqs(vdev); + misc_deregister(&nsm->misc); + list_del(&nsm->node); +} + +int nsm_register_hwrng(struct nsm_hwrng *_nsm_hwrng) +{ + struct nsm *nsm; + + if (nsm_hwrng) + return -EEXIST; + + nsm_hwrng = _nsm_hwrng; + + list_for_each_entry(nsm, &nsm_devices, node) + nsm_hwrng->probe(nsm->vdev); + + return 0; +} +EXPORT_SYMBOL_GPL(nsm_register_hwrng); + +void nsm_unregister_hwrng(struct nsm_hwrng *_nsm_hwrng) +{ + struct nsm *nsm; + + if (_nsm_hwrng != nsm_hwrng) + return; + + list_for_each_entry(nsm, &nsm_devices, node) + nsm_hwrng->remove(nsm->vdev); + nsm_hwrng = NULL; +} +EXPORT_SYMBOL_GPL(nsm_unregister_hwrng); + +/* NSM device configuration structure */ +static struct virtio_driver virtio_nsm_driver = { + .feature_table = 0, + .feature_table_size = 0, + .feature_table_legacy = 0, + .feature_table_size_legacy = 0, + .driver.name = KBUILD_MODNAME, + .driver.owner = THIS_MODULE, + .id_table = id_table, + .probe = nsm_device_probe, + .remove = nsm_device_remove, +}; + +module_virtio_driver(virtio_nsm_driver); +MODULE_DEVICE_TABLE(virtio, id_table); +MODULE_DESCRIPTION("Virtio NSM driver"); +MODULE_LICENSE("GPL"); diff --git a/include/linux/nsm.h b/include/linux/nsm.h new file mode 100644 index 000000000000..82753de5485e --- /dev/null +++ b/include/linux/nsm.h @@ -0,0 +1,35 @@ +/* SPDX-License-Identifier: GPL-2.0 + * + * Amazon Nitro Secure Module driver. + * + * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved. + */ + +#ifndef __LINUX_NSM_H +#define __LINUX_NSM_H + +#include <linux/uio.h> +#include <linux/virtio.h> + +#define NSM_RESPONSE_MAX_SIZE 0x3000 + +struct nsm_hwrng { + int (*probe)(struct virtio_device *dev); + void (*remove)(struct virtio_device *dev); +}; + +int nsm_register_hwrng(struct nsm_hwrng *nsm_hwrng); +void nsm_unregister_hwrng(struct nsm_hwrng *nsm_hwrng); + +/* Copy of NSM message in kernel-space */ +struct nsm_kernel_message { + /* Copy of user request in kernel memory */ + struct kvec request; + /* Copy of user response in kernel memory */ + struct kvec response; +}; + +int nsm_communicate_with_device(struct virtio_device *dev, + struct nsm_kernel_message *message); + +#endif /* __LINUX_NSM_H */ diff --git a/include/uapi/linux/nsm.h b/include/uapi/linux/nsm.h new file mode 100644 index 000000000000..4100f8c69f36 --- /dev/null +++ b/include/uapi/linux/nsm.h @@ -0,0 +1,29 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +/* + * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved. + */ + +#ifndef __UAPI_LINUX_NSM_H +#define __UAPI_LINUX_NSM_H + +#include <linux/ioctl.h> +#include <linux/types.h> + +struct nsm_iovec +{ + __u64 addr; /* Virtual address of target buffer */ + __u64 len; /* Length of target buffer */ +}; + +/* NSM message from user-space */ +struct nsm_message { + /* Request from user */ + struct nsm_iovec request; + /* Response to user */ + struct nsm_iovec response; +}; + +#define NSM_MAGIC 0x0A +#define NSM_IOCTL_REQUEST _IOWR(NSM_MAGIC, 0, struct nsm_message) + +#endif /* __UAPI_LINUX_MISC_BCM_VK_H */ -- 2.40.1 Amazon Development Center Germany GmbH Krausenstr. 38 10117 Berlin Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B Sitz: Berlin Ust-ID: DE 289 237 879
