Fix an issue where the random number generator's random event injector
[dragonfly.git] / sys / kern / kern_nrandom.c
CommitLineData
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1/*
2 * Copyright (c) 2004, 2005, 2006 Robin J Carey. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions, and the following disclaimer,
9 * without modification, immediately at the beginning of the file.
10 * 2. The name of the author may not be used to endorse or promote products
11 * derived from this software without specific prior written permission.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
17 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23 * SUCH DAMAGE.
24 *
53d9cb72 25 * $DragonFly: src/sys/kern/kern_nrandom.c,v 1.6 2008/02/16 20:40:47 dillon Exp $
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26 */
27/* --- NOTES ---
28 *
29 * Note: The word "entropy" is often incorrectly used to describe
30 * random data. The word "entropy" originates from the science of
31 * Physics. The correct descriptive definition would be something
32 * along the lines of "seed", "unpredictable numbers" or
33 * "unpredictable data".
34 *
35 * Note: Some /dev/[u]random implementations save "seed" between
36 * boots which represents a security hazard since an adversary
37 * could acquire this data (since it is stored in a file). If
38 * the unpredictable data used in the above routines is only
39 * generated during Kernel operation, then an adversary can only
40 * acquire that data through a Kernel security compromise and/or
41 * a cryptographic algorithm failure/cryptanalysis.
42 *
43 * Note: On FreeBSD-4.11, interrupts have to be manually enabled
44 * using the rndcontrol(8) command.
45 *
46 * --- DESIGN (FreeBSD-4.11 based) ---
47 *
48 * The rnddev module automatically initializes itself the first time
49 * it is used (client calls any public rnddev_*() interface routine).
50 * Both CSPRNGs are initially seeded from the precise nano[up]time() routines.
51 * Tests show this method produces good enough results, suitable for intended
52 * use. It is necessary for both CSPRNGs to be completely seeded, initially.
53 *
54 * After initialization and during Kernel operation the only suitable
55 * unpredictable data available is:
56 *
57 * (1) Keyboard scan-codes.
58 * (2) Nanouptime acquired by a Keyboard/Read-Event.
59 * (3) Suitable interrupt source; hard-disk/ATA-device.
60 *
61 * (X) Mouse-event (xyz-data unsuitable); NOT IMPLEMENTED.
62 *
63 * This data is added to both CSPRNGs in real-time as it happens/
64 * becomes-available. Additionally, unpredictable (?) data may be
65 * acquired from a true-random number generator if such a device is
66 * available to the system (not advisable !).
67 * Nanouptime() acquired by a Read-Event is a very important aspect of
68 * this design, since it ensures that unpredictable data is added to
69 * the CSPRNGs even if there are no other sources.
70 * The nanouptime() Kernel routine is used since time relative to
71 * boot is less adversary-known than time itself.
72 *
73 * This design has been thoroughly tested with debug logging
74 * and the output from both /dev/random and /dev/urandom has
75 * been tested with the DIEHARD test-suite; both pass.
76 *
77 * MODIFICATIONS MADE TO ORIGINAL "kern_random.c":
78 *
79 * 6th July 2005:
80 *
81 * o Changed ReadSeed() function to schedule future read-seed-events
82 * by at least one second. Previous implementation used a randomised
83 * scheduling { 0, 1, 2, 3 seconds }.
84 * o Changed SEED_NANOUP() function to use a "previous" accumulator
85 * algorithm similar to ReadSeed(). This ensures that there is no
86 * way that an adversary can tell what number is being added to the
87 * CSPRNGs, since the number added to the CSPRNGs at Event-Time is
88 * the sum of nanouptime()@Event and an unknown/secret number.
89 * o Changed rnddev_add_interrupt() function to schedule future
90 * interrupt-events by at least one second. Previous implementation
91 * had no scheduling algorithm which allowed an "interrupt storm"
92 * to occur resulting in skewed data entering into the CSPRNGs.
93 *
94 *
95 * 9th July 2005:
96 *
97 * o Some small cleanups and change all internal functions to be
98 * static/private.
99 * o Removed ReadSeed() since its functionality is already performed
100 * by another function { rnddev_add_interrupt_OR_read() } and remove
101 * the silly rndByte accumulator/feedback-thing (since multipying by
102 * rndByte could yield a value of 0).
103 * o Made IBAA/L14 public interface become static/private;
104 * Local to this file (not changed to that in the original C modules).
105 *
106 * 16th July 2005:
107 *
108 * o SEED_NANOUP() -> NANOUP_EVENT() function rename.
109 * o Make NANOUP_EVENT() handle the time-buffering directly so that all
110 * time-stamp-events use this single time-buffer (including keyboard).
111 * This removes dependancy on "time_second" Kernel variable.
112 * o Removed second-time-buffer code in rnddev_add_interrupt_OR_read (void).
113 * o Rewrote the time-buffering algorithm in NANOUP_EVENT() to use a
114 * randomised time-delay range.
115 *
116 * 12th Dec 2005:
117 *
118 * o Updated to (hopefully final) L15 algorithm.
119 *
120 * 12th June 2006:
121 *
122 * o Added missing (u_char *) cast in RnddevRead() function.
123 * o Changed copyright to 3-clause BSD license and cleaned up the layout
124 * of this file.
125 */
126
127#include <sys/types.h>
128#include <sys/kernel.h>
129#include <sys/systm.h>
130#include <sys/poll.h>
131#include <sys/random.h>
132#include <sys/systimer.h>
133#include <sys/time.h>
134#include <sys/proc.h>
135#include <sys/lock.h>
136#include <sys/sysctl.h>
137#include <sys/spinlock.h>
138#include <machine/clock.h>
139
140#include <sys/thread2.h>
141#include <sys/spinlock2.h>
142
143/*
144 * Portability note: The u_char/unsigned char type is used where
145 * uint8_t from <stdint.h> or u_int8_t from <sys/types.h> should really
146 * be being used. On FreeBSD, it is safe to make the assumption that these
147 * different types are equivalent (on all architectures).
148 * The FreeBSD <sys/crypto/rc4> module also makes this assumption.
149 */
150
151/*------------------------------ IBAA ----------------------------------*/
152
153/*-------------------------- IBAA CSPRNG -------------------------------*/
154
155/*
156 * NOTE: The original source code from which this source code (IBAA)
157 * was taken has no copyright/license. The algorithm has no patent
158 * and is freely/publicly available from:
159 *
160 * http://www.burtleburtle.net/bob/rand/isaac.html
161 */
162
163/*
164 * ^ means XOR, & means bitwise AND, a<<b means shift a by b.
165 * barrel(a) shifts a 19 bits to the left, and bits wrap around
166 * ind(x) is (x AND 255), or (x mod 256)
167 */
168typedef u_int32_t u4; /* unsigned four bytes, 32 bits */
169
170#define ALPHA (8)
171#define SIZE (1 << ALPHA)
c26b3d4d 172#define MASK (SIZE - 1)
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173#define ind(x) ((x) & (SIZE - 1))
174#define barrel(a) (((a) << 19) ^ ((a) >> 13)) /* beta=32,shift=19 */
175
176static void IBAA
177(
178 u4 *m, /* Memory: array of SIZE ALPHA-bit terms */
179 u4 *r, /* Results: the sequence, same size as m */
180 u4 *aa, /* Accumulator: a single value */
181 u4 *bb /* the previous result */
182)
183{
184 u4 a, b, x, y, i;
185
186 a = *aa; b = *bb;
187 for (i = 0; i < SIZE; ++i) {
188 x = m[i];
189 a = barrel(a) + m[ind(i + (SIZE / 2))]; /* set a */
190 m[i] = y = m[ind(x)] + a + b; /* set m */
191 r[i] = b = m[ind(y >> ALPHA)] + x; /* set r */
192 }
193 *bb = b; *aa = a;
194}
195
196/*-------------------------- IBAA CSPRNG -------------------------------*/
197
198
199static u4 IBAA_memory[SIZE];
200static u4 IBAA_results[SIZE];
201static u4 IBAA_aa;
202static u4 IBAA_bb;
203
204static volatile int IBAA_byte_index;
205
206
207static void IBAA_Init(void);
208static void IBAA_Call(void);
209static void IBAA_Seed(const u_int32_t val);
210static u_char IBAA_Byte(void);
211
212/*
213 * Initialize IBAA.
214 */
215static void
216IBAA_Init(void)
217{
218 size_t i;
219
220 for (i = 0; i < SIZE; ++i) {
221 IBAA_memory[i] = i;
222 }
223 IBAA_aa = IBAA_bb = 0;
224 IBAA_byte_index = sizeof(IBAA_results); /* force IBAA_Call() */
225}
226
227/*
228 * PRIVATE: Call IBAA to produce 256 32-bit u4 results.
229 */
230static void
231IBAA_Call (void)
232{
233 IBAA(IBAA_memory, IBAA_results, &IBAA_aa, &IBAA_bb);
234 IBAA_byte_index = 0;
235}
236
237/*
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238 * Add a 32-bit u4 seed value into IBAAs memory. Mix the low 4 bits
239 * with 4 bits of PNG data to reduce the possibility of a seeding-based
240 * attack.
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241 */
242static void
243IBAA_Seed (const u_int32_t val)
244{
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245 static int memIndex;
246 u4 *iptr;
c0b252c3 247
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248 iptr = &IBAA_memory[memIndex & MASK];
249 *iptr = ((*iptr << 3) | (*iptr >> 29)) + (val ^ (IBAA_Byte() & 15));
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250 ++memIndex;
251}
252
253/*
254 * Extract a byte from IBAAs 256 32-bit u4 results array.
255 *
256 * NOTE: This code is designed to prevent MP races from taking
257 * IBAA_byte_index out of bounds.
258 */
259static u_char
260IBAA_Byte(void)
261{
262 u_char result;
263 int index;
264
265 index = IBAA_byte_index;
266 if (index == sizeof(IBAA_results)) {
267 IBAA_Call();
268 index = 0;
269 }
270 result = ((u_char *)IBAA_results)[index];
271 IBAA_byte_index = index + 1;
272 return result;
273}
274
275/*------------------------------ IBAA ----------------------------------*/
276
277
278/*------------------------------- L15 ----------------------------------*/
279
280/*
281 * IMPORTANT NOTE: LByteType must be exactly 8-bits in size or this software
282 * will not function correctly.
283 */
284typedef unsigned char LByteType;
285
286#define L15_STATE_SIZE 256
287
288static LByteType L15_x, L15_y;
289static LByteType L15_start_x;
290static LByteType L15_state[L15_STATE_SIZE];
291
292/*
293 * PRIVATE FUNCS:
294 */
295
296static void L15_Swap(const LByteType pos1, const LByteType pos2);
297static void L15_InitState(void);
298static void L15_KSA(const LByteType * const key,
299 const size_t keyLen);
300static void L15_Discard(const LByteType numCalls);
301
302/*
303 * PUBLIC INTERFACE:
304 */
305static void L15(const LByteType * const key, const size_t keyLen);
306static LByteType L15_Byte(void);
307static void L15_Vector(const LByteType * const key,
308 const size_t keyLen);
309
310static __inline void
311L15_Swap(const LByteType pos1, const LByteType pos2)
312{
313 const LByteType save1 = L15_state[pos1];
314
315 L15_state[pos1] = L15_state[pos2];
316 L15_state[pos2] = save1;
317}
318
319static void
320L15_InitState (void)
321{
322 size_t i;
323 for (i = 0; i < L15_STATE_SIZE; ++i)
324 L15_state[i] = i;
325}
326
327#define L_SCHEDULE(xx) \
328 \
329for (i = 0; i < L15_STATE_SIZE; ++i) { \
330 L15_Swap(i, (stateIndex += (L15_state[i] + (xx)))); \
331}
332
333static void
334L15_KSA (const LByteType * const key, const size_t keyLen)
335{
336 size_t i, keyIndex;
337 LByteType stateIndex = 0;
338
339 L_SCHEDULE(keyLen);
340 for (keyIndex = 0; keyIndex < keyLen; ++keyIndex) {
341 L_SCHEDULE(key[keyIndex]);
342 }
343}
344
345static void
346L15_Discard(const LByteType numCalls)
347{
348 LByteType i;
349 for (i = 0; i < numCalls; ++i) {
350 (void)L15_Byte();
351 }
352}
353
354
355/*
356 * PUBLIC INTERFACE:
357 */
358static void
359L15(const LByteType * const key, const size_t keyLen)
360{
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361 L15_x = L15_start_x = 0;
362 L15_y = L15_STATE_SIZE - 1;
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363 L15_InitState();
364 L15_KSA(key, keyLen);
365 L15_Discard(L15_Byte());
366}
367
368static LByteType
369L15_Byte(void)
370{
371 LByteType z;
372
373 L15_Swap(L15_state[L15_x], L15_y);
374 z = (L15_state [L15_x++] + L15_state[L15_y--]);
375 if (L15_x == L15_start_x) {
376 --L15_y;
377 }
378 return (L15_state[z]);
379}
380
381static void
382L15_Vector (const LByteType * const key, const size_t keyLen)
383{
384 L15_KSA(key, keyLen);
385}
386
387/*------------------------------- L15 ----------------------------------*/
388
389/************************************************************************
390 * KERNEL INTERFACE *
391 ************************************************************************
392 *
393 * By Robin J Carey and Matthew Dillon.
394 */
395
396static int rand_thread_signal = 1;
397static void NANOUP_EVENT(void);
398static thread_t rand_td;
399static struct spinlock rand_spin;
400
401static int nrandevents;
402SYSCTL_INT(_kern, OID_AUTO, nrandevents, CTLFLAG_RD, &nrandevents, 0, "");
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403static int seedenable;
404SYSCTL_INT(_kern, OID_AUTO, seedenable, CTLFLAG_RW, &seedenable, 0, "");
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405
406/*
407 * Called from early boot
408 */
409void
410rand_initialize(void)
411{
412 struct timespec now;
413 int i;
414
415 spin_init(&rand_spin);
416
417 /* Initialize IBAA. */
418 IBAA_Init();
419
420 /* Initialize L15. */
421 nanouptime(&now);
422 L15((const LByteType *)&now.tv_nsec, sizeof(now.tv_nsec));
423 for (i = 0; i < (SIZE / 2); ++i) {
424 nanotime(&now);
425 IBAA_Seed(now.tv_nsec);
426 L15_Vector((const LByteType *)&now.tv_nsec,
427 sizeof(now.tv_nsec));
428 nanouptime(&now);
429 IBAA_Seed(now.tv_nsec);
430 L15_Vector((const LByteType *)&now.tv_nsec,
431 sizeof(now.tv_nsec));
432 }
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433
434 /*
435 * Warm up the generator to get rid of weak initial states.
436 */
437 for (i = 0; i < 10; ++i)
438 IBAA_Call();
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439}
440
441/*
442 * Keyboard events
443 */
444void
445add_keyboard_randomness(u_char scancode)
446{
447 spin_lock_wr(&rand_spin);
448 L15_Vector((const LByteType *) &scancode, sizeof (scancode));
449 spin_unlock_wr(&rand_spin);
450 add_interrupt_randomness(0);
451}
452
453/*
53d9cb72 454 * Interrupt events. This is SMP safe and allowed to race.
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455 */
456void
457add_interrupt_randomness(int intr)
458{
459 if (rand_thread_signal == 0) {
460 rand_thread_signal = 1;
461 lwkt_schedule(rand_td);
462 }
463}
464
465/*
466 * True random number source
467 */
468void
469add_true_randomness(int val)
470{
471 spin_lock_wr(&rand_spin);
472 IBAA_Seed(val);
473 L15_Vector((const LByteType *) &val, sizeof (val));
474 ++nrandevents;
475 spin_unlock_wr(&rand_spin);
476}
477
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478int
479add_buffer_randomness(const char *buf, int bytes)
480{
481 int error;
01b40dc2 482 int i;
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483
484 if (seedenable && securelevel <= 0) {
485 while (bytes >= sizeof(int)) {
486 add_true_randomness(*(const int *)buf);
487 buf += sizeof(int);
488 bytes -= sizeof(int);
489 }
490 error = 0;
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491
492 /*
493 * Warm up the generator to get rid of weak initial states.
494 */
495 for (i = 0; i < 10; ++i)
496 IBAA_Call();
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497 } else {
498 error = EPERM;
499 }
500 return (error);
501}
502
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503/*
504 * Poll (always succeeds)
505 */
506int
b13267a5 507random_poll(cdev_t dev, int events)
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508{
509 int revents = 0;
510
511 if (events & (POLLIN | POLLRDNORM))
512 revents |= events & (POLLIN | POLLRDNORM);
513 if (events & (POLLOUT | POLLWRNORM))
514 revents |= events & (POLLOUT | POLLWRNORM);
515
516 return (revents);
517}
518
519/*
520 * Heavy weight random number generator. May return less then the
521 * requested number of bytes.
522 */
523u_int
524read_random(void *buf, u_int nbytes)
525{
526 u_int i;
527
528 spin_lock_wr(&rand_spin);
529 for (i = 0; i < nbytes; ++i)
530 ((u_char *)buf)[i] = IBAA_Byte();
531 spin_unlock_wr(&rand_spin);
532 add_interrupt_randomness(0);
533 return(i);
534}
535
536/*
537 * Lightweight random number generator. Must return requested number of
538 * bytes.
539 */
540u_int
541read_random_unlimited(void *buf, u_int nbytes)
542{
543 u_int i;
544
545 spin_lock_wr(&rand_spin);
546 for (i = 0; i < nbytes; ++i)
547 ((u_char *)buf)[i] = L15_Byte();
548 spin_unlock_wr(&rand_spin);
549 add_interrupt_randomness(0);
550 return (i);
551}
552
553/*
554 * Random number generator helper thread. This limits code overhead from
555 * high frequency events by delaying the clearing of rand_thread_signal.
556 */
557static
558void
559rand_thread_loop(void *dummy)
560{
561 int count;
562
563 for (;;) {
564 NANOUP_EVENT ();
565 spin_lock_wr(&rand_spin);
566 count = (int)(L15_Byte() * hz / (256 * 10) + hz / 10);
567 spin_unlock_wr(&rand_spin);
568 tsleep(rand_td, 0, "rwait", count);
53d9cb72 569 crit_enter();
c0b252c3 570 lwkt_deschedule_self(rand_td);
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571 cpu_sfence();
572 rand_thread_signal = 0;
573 crit_exit();
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574 lwkt_switch();
575 }
576}
577
578static
579void
580rand_thread_init(void)
581{
582 lwkt_create(rand_thread_loop, NULL, &rand_td, NULL, 0, 0, "random");
583}
584
585SYSINIT(rand, SI_SUB_HELPER_THREADS, SI_ORDER_ANY, rand_thread_init, 0);
586
587/*
588 * Time-buffered event time-stamping. This is necessary to cutoff higher
589 * event frequencies, e.g. an interrupt occuring at 25Hz. In such cases
590 * the CPU is being chewed and the timestamps are skewed (minimal variation).
591 * Use a nano-second time-delay to limit how many times an Event can occur
592 * in one second; <= 5Hz. Note that this doesn't prevent time-stamp skewing.
593 * This implementation randmoises the time-delay between events, which adds
594 * a layer of security/unpredictability with regard to read-events (a user
595 * controlled input).
596 *
597 * Note: now.tv_nsec should range [ 0 - 1000,000,000 ].
598 * Note: "ACCUM" is a security measure (result = capped-unknown + unknown),
599 * and also produces an uncapped (>=32-bit) value.
600 */
601static void
602NANOUP_EVENT(void)
603{
604 static struct timespec ACCUM = { 0, 0 };
605 static struct timespec NEXT = { 0, 0 };
606 struct timespec now;
607
608 nanouptime(&now);
609 spin_lock_wr(&rand_spin);
610 if ((now.tv_nsec > NEXT.tv_nsec) || (now.tv_sec != NEXT.tv_sec)) {
611 /*
612 * Randomised time-delay: 200e6 - 350e6 ns; 5 - 2.86 Hz.
613 */
614 unsigned long one_mil;
615 unsigned long timeDelay;
616
617 one_mil = 1000000UL; /* 0.001 s */
618 timeDelay = (one_mil * 200) + (((unsigned)ACCUM.tv_nsec % 151) * one_mil);
619 NEXT.tv_nsec = now.tv_nsec + timeDelay;
620 NEXT.tv_sec = now.tv_sec;
621 ACCUM.tv_nsec += now.tv_nsec;
622
623 /*
624 * The TSC, if present, generally has an even higher
625 * resolution. Integrate a portion of it into our seed.
626 */
627 if (tsc_present)
628 ACCUM.tv_nsec ^= rdtsc() & 255;
629
630 IBAA_Seed(ACCUM.tv_nsec);
631 L15_Vector((const LByteType *)&ACCUM.tv_nsec,
632 sizeof(ACCUM.tv_nsec));
633 ++nrandevents;
634 }
635 spin_unlock_wr(&rand_spin);
636}
637