1/*-
2 * Copyright (c) 2000-2013 Mark R V Murray
3 * Copyright (c) 2013 Arthur Mesh
4 * Copyright (c) 2004 Robert N. M. Watson
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer
12 *    in this position and unchanged.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 */
29
30#include <sys/cdefs.h>
31__FBSDID("$FreeBSD$");
32
33#include "opt_random.h"
34
35#include <sys/param.h>
36#include <sys/systm.h>
37#include <sys/eventhandler.h>
38#include <sys/kernel.h>
39#include <sys/kthread.h>
40#include <sys/linker.h>
41#include <sys/lock.h>
42#include <sys/malloc.h>
43#include <sys/mutex.h>
44#include <sys/random.h>
45#include <sys/selinfo.h>
46#include <sys/sysctl.h>
47#include <sys/unistd.h>
48
49#include <machine/cpu.h>
50#include <machine/vmparam.h>
51
52#include <dev/random/randomdev.h>
53#include <dev/random/randomdev_soft.h>
54#include <dev/random/random_adaptors.h>
55#include <dev/random/random_harvestq.h>
56#include <dev/random/live_entropy_sources.h>
57#include <dev/random/rwfile.h>
58
59#define RANDOM_FIFO_MAX	1024	/* How many events to queue up */
60
61/*
62 * The harvest mutex protects the consistency of the entropy fifos and
63 * empty fifo and other associated structures.
64 */
65struct mtx	harvest_mtx;
66
67/* Lockable FIFO queue holding entropy buffers */
68struct entropyfifo {
69	int count;
70	STAILQ_HEAD(harvestlist, harvest) head;
71};
72
73/* Empty entropy buffers */
74static struct entropyfifo emptyfifo;
75
76/* Harvested entropy */
77static struct entropyfifo harvestfifo;
78
79/* <0 to end the kthread, 0 to let it run, 1 to flush the harvest queues */
80int random_kthread_control = 0;
81
82static struct proc *random_kthread_proc;
83
84static event_proc_f random_cb;
85
86#ifdef RANDOM_RWFILE
87static const char *entropy_files[] = {
88	"/entropy",
89	NULL
90};
91#endif
92
93/* Deal with entropy cached externally if this is present.
94 * Lots of policy may eventually arrive in this function.
95 * Called after / is mounted.
96 */
97static void
98random_harvestq_cache(void *arg __unused)
99{
100	uint8_t *keyfile, *data;
101	size_t size, i;
102#ifdef RANDOM_RWFILE
103	const char **entropy_file;
104	uint8_t *zbuf;
105	int error;
106#endif
107
108	/* Get stuff that may have been preloaded by loader(8) */
109	keyfile = preload_search_by_type("/boot/entropy");
110	if (keyfile != NULL) {
111		data = preload_fetch_addr(keyfile);
112		size = preload_fetch_size(keyfile);
113		if (data != NULL && size != 0) {
114			for (i = 0; i < size; i += 16)
115				random_harvestq_internal(get_cyclecount(), data + i, 16, 16, RANDOM_CACHED);
116			printf("random: read %zu bytes from preloaded cache\n", size);
117			bzero(data, size);
118		}
119		else
120			printf("random: no preloaded entropy cache available\n");
121	}
122
123#ifdef RANDOM_RWFILE
124	/* Read and attempt to overwrite the entropy cache files.
125	 * If the file exists, can be read and then overwritten,
126	 * then use it. Ignore it otherwise, but print out what is
127	 * going on.
128	 */
129	data = malloc(PAGE_SIZE, M_ENTROPY, M_WAITOK);
130	zbuf = __DECONST(void *, zero_region);
131	for (entropy_file = entropy_files; *entropy_file; entropy_file++) {
132		error = randomdev_read_file(*entropy_file, data, PAGE_SIZE);
133		if (error == 0) {
134			printf("random: entropy cache '%s' provides %ld bytes\n", *entropy_file, (long)PAGE_SIZE);
135			error = randomdev_write_file(*entropy_file, zbuf, PAGE_SIZE);
136			if (error == 0) {
137				printf("random: entropy cache '%s' contents used and successfully overwritten\n", *entropy_file);
138				for (i = 0; i < PAGE_SIZE; i += 16)
139					random_harvestq_internal(get_cyclecount(), data + i, 16, 16, RANDOM_CACHED);
140			}
141			else
142				printf("random: entropy cache '%s' not overwritten and therefore not used; error = %d\n", *entropy_file, error);
143		}
144		else
145			printf("random: entropy cache '%s' not present or unreadable; error = %d\n", *entropy_file, error);
146	}
147	bzero(data, PAGE_SIZE);
148	free(data, M_ENTROPY);
149#endif
150}
151EVENTHANDLER_DEFINE(mountroot, random_harvestq_cache, NULL, 0);
152
153static void
154random_kthread(void *arg)
155{
156	STAILQ_HEAD(, harvest) local_queue;
157	struct harvest *event = NULL;
158	int local_count;
159	event_proc_f entropy_processor = arg;
160
161	STAILQ_INIT(&local_queue);
162	local_count = 0;
163
164	/* Process until told to stop */
165	mtx_lock_spin(&harvest_mtx);
166	for (; random_kthread_control >= 0;) {
167
168		/*
169		 * Grab all the entropy events.
170		 * Drain entropy source records into a thread-local
171		 * queue for processing while not holding the mutex.
172		 */
173		STAILQ_CONCAT(&local_queue, &harvestfifo.head);
174		local_count += harvestfifo.count;
175		harvestfifo.count = 0;
176
177		/*
178		 * Deal with events, if any.
179		 * Then transfer the used events back into the empty fifo.
180		 */
181		if (!STAILQ_EMPTY(&local_queue)) {
182			mtx_unlock_spin(&harvest_mtx);
183			STAILQ_FOREACH(event, &local_queue, next)
184				entropy_processor(event);
185			mtx_lock_spin(&harvest_mtx);
186			STAILQ_CONCAT(&emptyfifo.head, &local_queue);
187			emptyfifo.count += local_count;
188			local_count = 0;
189		}
190
191		KASSERT(local_count == 0, ("random_kthread: local_count %d",
192		    local_count));
193
194		/*
195		 * Do only one round of the hardware sources for now.
196		 * Later we'll need to make it rate-adaptive.
197		 */
198		mtx_unlock_spin(&harvest_mtx);
199		live_entropy_sources_feed(1, entropy_processor);
200		mtx_lock_spin(&harvest_mtx);
201
202		/*
203		 * If a queue flush was commanded, it has now happened,
204		 * and we can mark this by resetting the command.
205		 */
206
207		if (random_kthread_control == 1)
208			random_kthread_control = 0;
209
210		/* Work done, so don't belabour the issue */
211		msleep_spin_sbt(&random_kthread_control, &harvest_mtx,
212		    "-", SBT_1S/10, 0, C_PREL(1));
213
214	}
215	mtx_unlock_spin(&harvest_mtx);
216
217	random_set_wakeup_exit(&random_kthread_control);
218	/* NOTREACHED */
219}
220
221void
222random_harvestq_init(event_proc_f cb)
223{
224	int i;
225	struct harvest *np;
226
227	/* Initialise the harvest fifos */
228
229	/* Contains the currently unused event structs. */
230	STAILQ_INIT(&emptyfifo.head);
231	for (i = 0; i < RANDOM_FIFO_MAX; i++) {
232		np = malloc(sizeof(struct harvest), M_ENTROPY, M_WAITOK);
233		STAILQ_INSERT_TAIL(&emptyfifo.head, np, next);
234	}
235	emptyfifo.count = RANDOM_FIFO_MAX;
236
237	/* Will contain the queued-up events. */
238	STAILQ_INIT(&harvestfifo.head);
239	harvestfifo.count = 0;
240
241	mtx_init(&harvest_mtx, "entropy harvest mutex", NULL, MTX_SPIN);
242
243	random_cb = cb;
244}
245
246static void
247random_harvestq_start_kproc(void *arg __unused)
248{
249	int error;
250
251	if (random_cb == NULL)
252		return;
253
254	/* Start the hash/reseed thread */
255	error = kproc_create(random_kthread, random_cb,
256	    &random_kthread_proc, RFHIGHPID, 0, "rand_harvestq"); /* RANDOM_CSPRNG_NAME */
257
258	if (error != 0)
259		panic("Cannot create entropy maintenance thread.");
260}
261SYSINIT(random_kthread, SI_SUB_DRIVERS, SI_ORDER_ANY,
262    random_harvestq_start_kproc, NULL);
263
264void
265random_harvestq_deinit(void)
266{
267	struct harvest *np;
268
269	/* Destroy the harvest fifos */
270	while (!STAILQ_EMPTY(&emptyfifo.head)) {
271		np = STAILQ_FIRST(&emptyfifo.head);
272		STAILQ_REMOVE_HEAD(&emptyfifo.head, next);
273		free(np, M_ENTROPY);
274	}
275	emptyfifo.count = 0;
276	while (!STAILQ_EMPTY(&harvestfifo.head)) {
277		np = STAILQ_FIRST(&harvestfifo.head);
278		STAILQ_REMOVE_HEAD(&harvestfifo.head, next);
279		free(np, M_ENTROPY);
280	}
281	harvestfifo.count = 0;
282
283	/*
284	 * Command the hash/reseed thread to end and wait for it to finish
285	 */
286	mtx_lock_spin(&harvest_mtx);
287	if (random_kthread_proc != NULL) {
288		random_kthread_control = -1;
289		msleep_spin((void *)&random_kthread_control, &harvest_mtx,
290		    "term", 0);
291	}
292	mtx_unlock_spin(&harvest_mtx);
293
294	mtx_destroy(&harvest_mtx);
295}
296
297/*
298 * Entropy harvesting routine.
299 * This is supposed to be fast; do not do anything slow in here!
300 *
301 * It is also illegal (and morally reprehensible) to insert any
302 * high-rate data here. "High-rate" is define as a data source
303 * that will usually cause lots of failures of the "Lockless read"
304 * check a few lines below. This includes the "always-on" sources
305 * like the Intel "rdrand" or the VIA Nehamiah "xstore" sources.
306 */
307void
308random_harvestq_internal(u_int64_t somecounter, const void *entropy,
309    u_int count, u_int bits, enum esource origin)
310{
311	struct harvest *event;
312
313	KASSERT(origin >= RANDOM_START && origin < ENTROPYSOURCE,
314	    ("random_harvest_internal: origin %d invalid\n", origin));
315
316	/* Lockless read to avoid lock operations if fifo is full. */
317	if (harvestfifo.count >= RANDOM_FIFO_MAX)
318		return;
319
320	mtx_lock_spin(&harvest_mtx);
321
322	/*
323	 * On't overfill the harvest queue; this could steal all
324	 * our memory.
325	 */
326	if (harvestfifo.count < RANDOM_FIFO_MAX) {
327		event = STAILQ_FIRST(&emptyfifo.head);
328		if (event != NULL) {
329			/* Add the harvested data to the fifo */
330			STAILQ_REMOVE_HEAD(&emptyfifo.head, next);
331			emptyfifo.count--;
332			event->somecounter = somecounter;
333			event->size = count;
334			event->bits = bits;
335			event->source = origin;
336
337			/* XXXX Come back and make this dynamic! */
338			count = MIN(count, HARVESTSIZE);
339			memcpy(event->entropy, entropy, count);
340
341			STAILQ_INSERT_TAIL(&harvestfifo.head,
342			    event, next);
343			harvestfifo.count++;
344		}
345	}
346
347	mtx_unlock_spin(&harvest_mtx);
348}
349