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path: root/drivers/misc/nsm.c
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-rw-r--r--drivers/misc/nsm.c506
1 files changed, 506 insertions, 0 deletions
diff --git a/drivers/misc/nsm.c b/drivers/misc/nsm.c
new file mode 100644
index 000000000000..0eaa3b4484bd
--- /dev/null
+++ b/drivers/misc/nsm.c
@@ -0,0 +1,506 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Amazon Nitro Secure Module driver.
+ *
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * The Nitro Secure Module implements commands via CBOR over virtio.
+ * This driver exposes a raw message ioctls on /dev/nsm that user
+ * space can use to issue these commands.
+ */
+
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/interrupt.h>
+#include <linux/hw_random.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/virtio.h>
+#include <linux/wait.h>
+#include <uapi/linux/nsm.h>
+
+/* Timeout for NSM virtqueue respose in milliseconds. */
+#define NSM_DEFAULT_TIMEOUT_MSECS (120000) /* 2 minutes */
+
+/* Maximum length input data */
+struct nsm_data_req {
+ u32 len;
+ u8 data[NSM_REQUEST_MAX_SIZE];
+};
+
+/* Maximum length output data */
+struct nsm_data_resp {
+ u32 len;
+ u8 data[NSM_RESPONSE_MAX_SIZE];
+};
+
+/* Full NSM request/response message */
+struct nsm_msg {
+ struct nsm_data_req req;
+ struct nsm_data_resp resp;
+};
+
+struct nsm {
+ struct virtio_device *vdev;
+ struct virtqueue *vq;
+ struct mutex lock;
+ struct completion cmd_done;
+ struct miscdevice misc;
+ struct hwrng hwrng;
+ struct work_struct misc_init;
+ struct nsm_msg msg;
+};
+
+/* NSM device ID */
+static const struct virtio_device_id id_table[] = {
+ { VIRTIO_ID_NITRO_SEC_MOD, VIRTIO_DEV_ANY_ID },
+ { 0 },
+};
+
+static struct nsm *file_to_nsm(struct file *file)
+{
+ return container_of(file->private_data, struct nsm, misc);
+}
+
+static struct nsm *hwrng_to_nsm(struct hwrng *rng)
+{
+ return container_of(rng, struct nsm, hwrng);
+}
+
+#define CBOR_TYPE_MASK 0xE0
+#define CBOR_TYPE_MAP 0xA0
+#define CBOR_TYPE_TEXT 0x60
+#define CBOR_TYPE_ARRAY 0x40
+#define CBOR_HEADER_SIZE_SHORT 1
+
+#define CBOR_SHORT_SIZE_MAX_VALUE 23
+#define CBOR_LONG_SIZE_U8 24
+#define CBOR_LONG_SIZE_U16 25
+#define CBOR_LONG_SIZE_U32 26
+#define CBOR_LONG_SIZE_U64 27
+
+static bool cbor_object_is_array(const u8 *cbor_object, size_t cbor_object_size)
+{
+ if (cbor_object_size == 0 || cbor_object == NULL)
+ return false;
+
+ return (cbor_object[0] & CBOR_TYPE_MASK) == CBOR_TYPE_ARRAY;
+}
+
+static int cbor_object_get_array(u8 *cbor_object, size_t cbor_object_size, u8 **cbor_array)
+{
+ u8 cbor_short_size;
+ void *array_len_p;
+ u64 array_len;
+ u64 array_offset;
+
+ if (!cbor_object_is_array(cbor_object, cbor_object_size))
+ return -EFAULT;
+
+ cbor_short_size = (cbor_object[0] & 0x1F);
+
+ /* Decoding byte array length */
+ array_offset = CBOR_HEADER_SIZE_SHORT;
+ if (cbor_short_size >= CBOR_LONG_SIZE_U8)
+ array_offset += BIT(cbor_short_size - CBOR_LONG_SIZE_U8);
+
+ if (cbor_object_size < array_offset)
+ return -EFAULT;
+
+ array_len_p = &cbor_object[1];
+
+ switch (cbor_short_size) {
+ case CBOR_SHORT_SIZE_MAX_VALUE: /* short encoding */
+ array_len = cbor_short_size;
+ break;
+ case CBOR_LONG_SIZE_U8:
+ array_len = *(u8 *)array_len_p;
+ break;
+ case CBOR_LONG_SIZE_U16:
+ array_len = be16_to_cpup((__be16 *)array_len_p);
+ break;
+ case CBOR_LONG_SIZE_U32:
+ array_len = be32_to_cpup((__be32 *)array_len_p);
+ break;
+ case CBOR_LONG_SIZE_U64:
+ array_len = be64_to_cpup((__be64 *)array_len_p);
+ break;
+ }
+
+ if (cbor_object_size < array_offset)
+ return -EFAULT;
+
+ if (cbor_object_size - array_offset < array_len)
+ return -EFAULT;
+
+ if (array_len > INT_MAX)
+ return -EFAULT;
+
+ *cbor_array = cbor_object + array_offset;
+ return array_len;
+}
+
+/* Copy the request of a raw message to kernel space */
+static int fill_req_raw(struct nsm *nsm, struct nsm_data_req *req,
+ struct nsm_raw *raw)
+{
+ /* Verify the user input size. */
+ if (raw->request.len > sizeof(req->data))
+ return -EMSGSIZE;
+
+ /* Copy the request payload */
+ if (copy_from_user(req->data, u64_to_user_ptr(raw->request.addr),
+ raw->request.len))
+ return -EFAULT;
+
+ req->len = raw->request.len;
+
+ return 0;
+}
+
+/* Copy the response of a raw message back to user-space */
+static int parse_resp_raw(struct nsm *nsm, struct nsm_data_resp *resp,
+ struct nsm_raw *raw)
+{
+ /* Truncate any message that does not fit. */
+ raw->response.len = min_t(u64, raw->response.len, resp->len);
+
+ /* Copy the response content to user space */
+ if (copy_to_user(u64_to_user_ptr(raw->response.addr),
+ resp->data, raw->response.len))
+ return -EFAULT;
+
+ return 0;
+}
+
+/* Virtqueue interrupt handler */
+static void nsm_vq_callback(struct virtqueue *vq)
+{
+ struct nsm *nsm = vq->vdev->priv;
+
+ complete(&nsm->cmd_done);
+}
+
+/* Forward a message to the NSM device and wait for the response from it */
+static int nsm_sendrecv_msg_locked(struct nsm *nsm)
+{
+ struct device *dev = &nsm->vdev->dev;
+ struct scatterlist sg_in, sg_out;
+ struct nsm_msg *msg = &nsm->msg;
+ struct virtqueue *vq = nsm->vq;
+ unsigned int len;
+ void *queue_buf;
+ bool kicked;
+ int rc;
+
+ /* Initialize scatter-gather lists with request and response buffers. */
+ sg_init_one(&sg_out, msg->req.data, msg->req.len);
+ sg_init_one(&sg_in, msg->resp.data, sizeof(msg->resp.data));
+
+ init_completion(&nsm->cmd_done);
+ /* Add the request buffer (read by the device). */
+ rc = virtqueue_add_outbuf(vq, &sg_out, 1, msg->req.data, GFP_KERNEL);
+ if (rc)
+ return rc;
+
+ /* Add the response buffer (written by the device). */
+ rc = virtqueue_add_inbuf(vq, &sg_in, 1, msg->resp.data, GFP_KERNEL);
+ if (rc)
+ goto cleanup;
+
+ kicked = virtqueue_kick(vq);
+ if (!kicked) {
+ /* Cannot kick the virtqueue. */
+ rc = -EIO;
+ goto cleanup;
+ }
+
+ /* If the kick succeeded, wait for the device's response. */
+ if (!wait_for_completion_io_timeout(&nsm->cmd_done,
+ msecs_to_jiffies(NSM_DEFAULT_TIMEOUT_MSECS))) {
+ rc = -ETIMEDOUT;
+ goto cleanup;
+ }
+
+ queue_buf = virtqueue_get_buf(vq, &len);
+ if (!queue_buf || (queue_buf != msg->req.data)) {
+ dev_err(dev, "wrong request buffer.");
+ rc = -ENODATA;
+ goto cleanup;
+ }
+
+ queue_buf = virtqueue_get_buf(vq, &len);
+ if (!queue_buf || (queue_buf != msg->resp.data)) {
+ dev_err(dev, "wrong response buffer.");
+ rc = -ENODATA;
+ goto cleanup;
+ }
+
+ msg->resp.len = len;
+
+ rc = 0;
+
+cleanup:
+ if (rc) {
+ /* Clean the virtqueue. */
+ while (virtqueue_get_buf(vq, &len) != NULL)
+ ;
+ }
+
+ return rc;
+}
+
+static int fill_req_get_random(struct nsm *nsm, struct nsm_data_req *req)
+{
+ /*
+ * 69 # text(9)
+ * 47657452616E646F6D # "GetRandom"
+ */
+ const u8 request[] = { CBOR_TYPE_TEXT + strlen("GetRandom"),
+ 'G', 'e', 't', 'R', 'a', 'n', 'd', 'o', 'm' };
+
+ memcpy(req->data, request, sizeof(request));
+ req->len = sizeof(request);
+
+ return 0;
+}
+
+static int parse_resp_get_random(struct nsm *nsm, struct nsm_data_resp *resp,
+ void *out, size_t max)
+{
+ /*
+ * A1 # map(1)
+ * 69 # text(9) - Name of field
+ * 47657452616E646F6D # "GetRandom"
+ * A1 # map(1) - The field itself
+ * 66 # text(6)
+ * 72616E646F6D # "random"
+ * # The rest of the response is random data
+ */
+ const u8 response[] = { CBOR_TYPE_MAP + 1,
+ CBOR_TYPE_TEXT + strlen("GetRandom"),
+ 'G', 'e', 't', 'R', 'a', 'n', 'd', 'o', 'm',
+ CBOR_TYPE_MAP + 1,
+ CBOR_TYPE_TEXT + strlen("random"),
+ 'r', 'a', 'n', 'd', 'o', 'm' };
+ struct device *dev = &nsm->vdev->dev;
+ u8 *rand_data = NULL;
+ u8 *resp_ptr = resp->data;
+ u64 resp_len = resp->len;
+ int rc;
+
+ if ((resp->len < sizeof(response) + 1) ||
+ (memcmp(resp_ptr, response, sizeof(response)) != 0)) {
+ dev_err(dev, "Invalid response for GetRandom");
+ return -EFAULT;
+ }
+
+ resp_ptr += sizeof(response);
+ resp_len -= sizeof(response);
+
+ rc = cbor_object_get_array(resp_ptr, resp_len, &rand_data);
+ if (rc < 0) {
+ dev_err(dev, "GetRandom: Invalid CBOR encoding\n");
+ return rc;
+ }
+
+ rc = min_t(size_t, rc, max);
+ memcpy(out, rand_data, rc);
+
+ return rc;
+}
+
+/*
+ * HwRNG implementation
+ */
+static int nsm_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+ struct nsm *nsm = hwrng_to_nsm(rng);
+ struct device *dev = &nsm->vdev->dev;
+ int rc = 0;
+
+ /* NSM always needs to wait for a response */
+ if (!wait)
+ return 0;
+
+ mutex_lock(&nsm->lock);
+
+ rc = fill_req_get_random(nsm, &nsm->msg.req);
+ if (rc != 0)
+ goto out;
+
+ rc = nsm_sendrecv_msg_locked(nsm);
+ if (rc != 0)
+ goto out;
+
+ rc = parse_resp_get_random(nsm, &nsm->msg.resp, data, max);
+ if (rc < 0)
+ goto out;
+
+ dev_dbg(dev, "RNG: returning rand bytes = %d", rc);
+out:
+ mutex_unlock(&nsm->lock);
+ return rc;
+}
+
+static long nsm_dev_ioctl(struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ void __user *argp = u64_to_user_ptr((u64)arg);
+ struct nsm *nsm = file_to_nsm(file);
+ struct nsm_raw raw;
+ int r = 0;
+
+ if (cmd != NSM_IOCTL_RAW)
+ return -EINVAL;
+
+ if (_IOC_SIZE(cmd) != sizeof(raw))
+ return -EINVAL;
+
+ /* Copy user argument struct to kernel argument struct */
+ r = -EFAULT;
+ if (copy_from_user(&raw, argp, _IOC_SIZE(cmd)))
+ goto out;
+
+ mutex_lock(&nsm->lock);
+
+ /* Convert kernel argument struct to device request */
+ r = fill_req_raw(nsm, &nsm->msg.req, &raw);
+ if (r)
+ goto out;
+
+ /* Send message to NSM and read reply */
+ r = nsm_sendrecv_msg_locked(nsm);
+ if (r)
+ goto out;
+
+ /* Parse device response into kernel argument struct */
+ r = parse_resp_raw(nsm, &nsm->msg.resp, &raw);
+ if (r)
+ goto out;
+
+ /* Copy kernel argument struct back to user argument struct */
+ r = -EFAULT;
+ if (copy_to_user(argp, &raw, sizeof(raw)))
+ goto out;
+
+ r = 0;
+
+out:
+ mutex_unlock(&nsm->lock);
+ return r;
+}
+
+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 = {
+ .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 device *dev = &vdev->dev;
+ struct nsm *nsm;
+ int rc;
+
+ nsm = devm_kzalloc(&vdev->dev, sizeof(*nsm), GFP_KERNEL);
+ if (!nsm)
+ return -ENOMEM;
+
+ vdev->priv = nsm;
+ nsm->vdev = vdev;
+
+ rc = nsm_device_init_vq(vdev);
+ if (rc) {
+ dev_err(dev, "queue failed to initialize: %d.\n", rc);
+ goto err_init_vq;
+ }
+
+ mutex_init(&nsm->lock);
+
+ /* Register as hwrng provider */
+ nsm->hwrng = (struct hwrng) {
+ .read = nsm_rng_read,
+ .name = "nsm-hwrng",
+ .quality = 1000,
+ };
+
+ rc = hwrng_register(&nsm->hwrng);
+ if (rc) {
+ dev_err(dev, "RNG initialization error: %d.\n", rc);
+ goto err_hwrng;
+ }
+
+ /* Register /dev/nsm device node */
+ nsm->misc = (struct miscdevice) {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "nsm",
+ .fops = &nsm_dev_fops,
+ .mode = 0666,
+ };
+
+ rc = misc_register(&nsm->misc);
+ if (rc) {
+ dev_err(dev, "misc device registration error: %d.\n", rc);
+ goto err_misc;
+ }
+
+ return 0;
+
+err_misc:
+ hwrng_unregister(&nsm->hwrng);
+err_hwrng:
+ vdev->config->del_vqs(vdev);
+err_init_vq:
+ return rc;
+}
+
+/* Handler for removing the NSM device */
+static void nsm_device_remove(struct virtio_device *vdev)
+{
+ struct nsm *nsm = vdev->priv;
+
+ hwrng_unregister(&nsm->hwrng);
+
+ vdev->config->del_vqs(vdev);
+ misc_deregister(&nsm->misc);
+}
+
+/* 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");
generated by cgit (git 2.34.1) at 2024-05-20 17:11:54 +0000