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 * 25 * $DragonFly: src/sys/kern/kern_nrandom.c,v 1.7 2008/08/01 04:42:30 dillon Exp $ 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 */ 168 typedef u_int32_t u4; /* unsigned four bytes, 32 bits */ 169 170 #define ALPHA (8) 171 #define SIZE (1 << ALPHA) 172 #define MASK (SIZE - 1) 173 #define ind(x) ((x) & (SIZE - 1)) 174 #define barrel(a) (((a) << 20) ^ ((a) >> 12)) /* beta=32,shift=20 */ 175 176 static 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 u4 *counter /* counter */ 183 ) 184 { 185 u4 a, b, x, y, i; 186 187 a = *aa; 188 b = *bb + *counter; 189 ++*counter; 190 for (i = 0; i < SIZE; ++i) { 191 x = m[i]; 192 a = barrel(a) + m[ind(i + (SIZE / 2))]; /* set a */ 193 m[i] = y = m[ind(x)] + a + b; /* set m */ 194 r[i] = b = m[ind(y >> ALPHA)] + x; /* set r */ 195 } 196 *bb = b; *aa = a; 197 } 198 199 /*-------------------------- IBAA CSPRNG -------------------------------*/ 200 201 202 static u4 IBAA_memory[SIZE]; 203 static u4 IBAA_results[SIZE]; 204 static u4 IBAA_aa; 205 static u4 IBAA_bb; 206 static u4 IBAA_counter; 207 208 static volatile int IBAA_byte_index; 209 210 211 static void IBAA_Init(void); 212 static void IBAA_Call(void); 213 static void IBAA_Seed(const u_int32_t val); 214 static u_char IBAA_Byte(void); 215 216 /* 217 * Initialize IBAA. 218 */ 219 static void 220 IBAA_Init(void) 221 { 222 size_t i; 223 224 for (i = 0; i < SIZE; ++i) { 225 IBAA_memory[i] = i; 226 } 227 IBAA_aa = IBAA_bb = 0; 228 IBAA_counter = 0; 229 IBAA_byte_index = sizeof(IBAA_results); /* force IBAA_Call() */ 230 } 231 232 /* 233 * PRIVATE: Call IBAA to produce 256 32-bit u4 results. 234 */ 235 static void 236 IBAA_Call (void) 237 { 238 IBAA(IBAA_memory, IBAA_results, &IBAA_aa, &IBAA_bb, &IBAA_counter); 239 IBAA_byte_index = 0; 240 } 241 242 /* 243 * Add a 32-bit u4 seed value into IBAAs memory. Mix the low 4 bits 244 * with 4 bits of PNG data to reduce the possibility of a seeding-based 245 * attack. 246 */ 247 static void 248 IBAA_Seed (const u_int32_t val) 249 { 250 static int memIndex; 251 u4 *iptr; 252 253 iptr = &IBAA_memory[memIndex & MASK]; 254 *iptr = ((*iptr << 3) | (*iptr >> 29)) + (val ^ (IBAA_Byte() & 15)); 255 ++memIndex; 256 } 257 258 /* 259 * Extract a byte from IBAAs 256 32-bit u4 results array. 260 * 261 * NOTE: This code is designed to prevent MP races from taking 262 * IBAA_byte_index out of bounds. 263 */ 264 static u_char 265 IBAA_Byte(void) 266 { 267 u_char result; 268 int index; 269 270 index = IBAA_byte_index; 271 if (index == sizeof(IBAA_results)) { 272 IBAA_Call(); 273 index = 0; 274 } 275 result = ((u_char *)IBAA_results)[index]; 276 IBAA_byte_index = index + 1; 277 return result; 278 } 279 280 /*------------------------------ IBAA ----------------------------------*/ 281 282 283 /*------------------------------- L15 ----------------------------------*/ 284 285 /* 286 * IMPORTANT NOTE: LByteType must be exactly 8-bits in size or this software 287 * will not function correctly. 288 */ 289 typedef unsigned char LByteType; 290 291 #define L15_STATE_SIZE 256 292 293 static LByteType L15_x, L15_y; 294 static LByteType L15_start_x; 295 static LByteType L15_state[L15_STATE_SIZE]; 296 297 /* 298 * PRIVATE FUNCS: 299 */ 300 301 static void L15_Swap(const LByteType pos1, const LByteType pos2); 302 static void L15_InitState(void); 303 static void L15_KSA(const LByteType * const key, 304 const size_t keyLen); 305 static void L15_Discard(const LByteType numCalls); 306 307 /* 308 * PUBLIC INTERFACE: 309 */ 310 static void L15(const LByteType * const key, const size_t keyLen); 311 static LByteType L15_Byte(void); 312 static void L15_Vector(const LByteType * const key, 313 const size_t keyLen); 314 315 static __inline void 316 L15_Swap(const LByteType pos1, const LByteType pos2) 317 { 318 const LByteType save1 = L15_state[pos1]; 319 320 L15_state[pos1] = L15_state[pos2]; 321 L15_state[pos2] = save1; 322 } 323 324 static void 325 L15_InitState (void) 326 { 327 size_t i; 328 for (i = 0; i < L15_STATE_SIZE; ++i) 329 L15_state[i] = i; 330 } 331 332 #define L_SCHEDULE(xx) \ 333 \ 334 for (i = 0; i < L15_STATE_SIZE; ++i) { \ 335 L15_Swap(i, (stateIndex += (L15_state[i] + (xx)))); \ 336 } 337 338 static void 339 L15_KSA (const LByteType * const key, const size_t keyLen) 340 { 341 size_t i, keyIndex; 342 LByteType stateIndex = 0; 343 344 L_SCHEDULE(keyLen); 345 for (keyIndex = 0; keyIndex < keyLen; ++keyIndex) { 346 L_SCHEDULE(key[keyIndex]); 347 } 348 } 349 350 static void 351 L15_Discard(const LByteType numCalls) 352 { 353 LByteType i; 354 for (i = 0; i < numCalls; ++i) { 355 (void)L15_Byte(); 356 } 357 } 358 359 360 /* 361 * PUBLIC INTERFACE: 362 */ 363 static void 364 L15(const LByteType * const key, const size_t keyLen) 365 { 366 L15_x = L15_start_x = 0; 367 L15_y = L15_STATE_SIZE - 1; 368 L15_InitState(); 369 L15_KSA(key, keyLen); 370 L15_Discard(L15_Byte()); 371 } 372 373 static LByteType 374 L15_Byte(void) 375 { 376 LByteType z; 377 378 L15_Swap(L15_state[L15_x], L15_y); 379 z = (L15_state [L15_x++] + L15_state[L15_y--]); 380 if (L15_x == L15_start_x) { 381 --L15_y; 382 } 383 return (L15_state[z]); 384 } 385 386 static void 387 L15_Vector (const LByteType * const key, const size_t keyLen) 388 { 389 L15_KSA(key, keyLen); 390 } 391 392 /*------------------------------- L15 ----------------------------------*/ 393 394 /************************************************************************ 395 * KERNEL INTERFACE * 396 ************************************************************************ 397 * 398 * By Robin J Carey and Matthew Dillon. 399 */ 400 401 static int rand_thread_signal = 1; 402 static void NANOUP_EVENT(void); 403 static thread_t rand_td; 404 static struct spinlock rand_spin; 405 406 static int nrandevents; 407 SYSCTL_INT(_kern, OID_AUTO, nrandevents, CTLFLAG_RD, &nrandevents, 0, ""); 408 static int seedenable; 409 SYSCTL_INT(_kern, OID_AUTO, seedenable, CTLFLAG_RW, &seedenable, 0, ""); 410 411 /* 412 * Called from early boot 413 */ 414 void 415 rand_initialize(void) 416 { 417 struct timespec now; 418 int i; 419 420 spin_init(&rand_spin); 421 422 /* Initialize IBAA. */ 423 IBAA_Init(); 424 425 /* Initialize L15. */ 426 nanouptime(&now); 427 L15((const LByteType *)&now.tv_nsec, sizeof(now.tv_nsec)); 428 for (i = 0; i < (SIZE / 2); ++i) { 429 nanotime(&now); 430 IBAA_Seed(now.tv_nsec); 431 L15_Vector((const LByteType *)&now.tv_nsec, 432 sizeof(now.tv_nsec)); 433 nanouptime(&now); 434 IBAA_Seed(now.tv_nsec); 435 L15_Vector((const LByteType *)&now.tv_nsec, 436 sizeof(now.tv_nsec)); 437 } 438 439 /* 440 * Warm up the generator to get rid of weak initial states. 441 */ 442 for (i = 0; i < 10; ++i) 443 IBAA_Call(); 444 } 445 446 /* 447 * Keyboard events 448 */ 449 void 450 add_keyboard_randomness(u_char scancode) 451 { 452 spin_lock_wr(&rand_spin); 453 L15_Vector((const LByteType *) &scancode, sizeof (scancode)); 454 spin_unlock_wr(&rand_spin); 455 add_interrupt_randomness(0); 456 } 457 458 /* 459 * Interrupt events. This is SMP safe and allowed to race. 460 */ 461 void 462 add_interrupt_randomness(int intr) 463 { 464 if (rand_thread_signal == 0) { 465 rand_thread_signal = 1; 466 lwkt_schedule(rand_td); 467 } 468 } 469 470 /* 471 * True random number source 472 */ 473 void 474 add_true_randomness(int val) 475 { 476 spin_lock_wr(&rand_spin); 477 IBAA_Seed(val); 478 L15_Vector((const LByteType *) &val, sizeof (val)); 479 ++nrandevents; 480 spin_unlock_wr(&rand_spin); 481 } 482 483 int 484 add_buffer_randomness(const char *buf, int bytes) 485 { 486 int error; 487 int i; 488 489 if (seedenable && securelevel <= 0) { 490 while (bytes >= sizeof(int)) { 491 add_true_randomness(*(const int *)buf); 492 buf += sizeof(int); 493 bytes -= sizeof(int); 494 } 495 error = 0; 496 497 /* 498 * Warm up the generator to get rid of weak initial states. 499 */ 500 for (i = 0; i < 10; ++i) 501 IBAA_Call(); 502 } else { 503 error = EPERM; 504 } 505 return (error); 506 } 507 508 /* 509 * Poll (always succeeds) 510 */ 511 int 512 random_poll(cdev_t dev, int events) 513 { 514 int revents = 0; 515 516 if (events & (POLLIN | POLLRDNORM)) 517 revents |= events & (POLLIN | POLLRDNORM); 518 if (events & (POLLOUT | POLLWRNORM)) 519 revents |= events & (POLLOUT | POLLWRNORM); 520 521 return (revents); 522 } 523 524 /* 525 * Heavy weight random number generator. May return less then the 526 * requested number of bytes. 527 */ 528 u_int 529 read_random(void *buf, u_int nbytes) 530 { 531 u_int i; 532 533 spin_lock_wr(&rand_spin); 534 for (i = 0; i < nbytes; ++i) 535 ((u_char *)buf)[i] = IBAA_Byte(); 536 spin_unlock_wr(&rand_spin); 537 add_interrupt_randomness(0); 538 return(i); 539 } 540 541 /* 542 * Lightweight random number generator. Must return requested number of 543 * bytes. 544 */ 545 u_int 546 read_random_unlimited(void *buf, u_int nbytes) 547 { 548 u_int i; 549 550 spin_lock_wr(&rand_spin); 551 for (i = 0; i < nbytes; ++i) 552 ((u_char *)buf)[i] = L15_Byte(); 553 spin_unlock_wr(&rand_spin); 554 add_interrupt_randomness(0); 555 return (i); 556 } 557 558 /* 559 * Random number generator helper thread. This limits code overhead from 560 * high frequency events by delaying the clearing of rand_thread_signal. 561 */ 562 static 563 void 564 rand_thread_loop(void *dummy) 565 { 566 int count; 567 568 for (;;) { 569 NANOUP_EVENT (); 570 spin_lock_wr(&rand_spin); 571 count = (int)(L15_Byte() * hz / (256 * 10) + hz / 10); 572 spin_unlock_wr(&rand_spin); 573 tsleep(rand_td, 0, "rwait", count); 574 crit_enter(); 575 lwkt_deschedule_self(rand_td); 576 cpu_sfence(); 577 rand_thread_signal = 0; 578 crit_exit(); 579 lwkt_switch(); 580 } 581 } 582 583 static 584 void 585 rand_thread_init(void) 586 { 587 lwkt_create(rand_thread_loop, NULL, &rand_td, NULL, 0, 0, "random"); 588 } 589 590 SYSINIT(rand, SI_SUB_HELPER_THREADS, SI_ORDER_ANY, rand_thread_init, 0); 591 592 /* 593 * Time-buffered event time-stamping. This is necessary to cutoff higher 594 * event frequencies, e.g. an interrupt occuring at 25Hz. In such cases 595 * the CPU is being chewed and the timestamps are skewed (minimal variation). 596 * Use a nano-second time-delay to limit how many times an Event can occur 597 * in one second; <= 5Hz. Note that this doesn't prevent time-stamp skewing. 598 * This implementation randmoises the time-delay between events, which adds 599 * a layer of security/unpredictability with regard to read-events (a user 600 * controlled input). 601 * 602 * Note: now.tv_nsec should range [ 0 - 1000,000,000 ]. 603 * Note: "ACCUM" is a security measure (result = capped-unknown + unknown), 604 * and also produces an uncapped (>=32-bit) value. 605 */ 606 static void 607 NANOUP_EVENT(void) 608 { 609 static struct timespec ACCUM = { 0, 0 }; 610 static struct timespec NEXT = { 0, 0 }; 611 struct timespec now; 612 613 nanouptime(&now); 614 spin_lock_wr(&rand_spin); 615 if ((now.tv_nsec > NEXT.tv_nsec) || (now.tv_sec != NEXT.tv_sec)) { 616 /* 617 * Randomised time-delay: 200e6 - 350e6 ns; 5 - 2.86 Hz. 618 */ 619 unsigned long one_mil; 620 unsigned long timeDelay; 621 622 one_mil = 1000000UL; /* 0.001 s */ 623 timeDelay = (one_mil * 200) + 624 (((unsigned long)ACCUM.tv_nsec % 151) * one_mil); 625 NEXT.tv_nsec = now.tv_nsec + timeDelay; 626 NEXT.tv_sec = now.tv_sec; 627 ACCUM.tv_nsec += now.tv_nsec; 628 629 /* 630 * The TSC, if present, generally has an even higher 631 * resolution. Integrate a portion of it into our seed. 632 */ 633 if (tsc_present) 634 ACCUM.tv_nsec ^= rdtsc() & 255; 635 636 IBAA_Seed(ACCUM.tv_nsec); 637 L15_Vector((const LByteType *)&ACCUM.tv_nsec, 638 sizeof(ACCUM.tv_nsec)); 639 ++nrandevents; 640 } 641 spin_unlock_wr(&rand_spin); 642 } 643 644