summaryrefslogtreecommitdiff
path: root/drivers/misc/nsm.c
blob: ef7b32742340999add6533472f0fe00a1a812742 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
// 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,
	.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");