1 /* 2 * random.c -- A strong random number generator 3 * 4 * Version 0.94, last modified 11-Oct-95 5 * 6 * Copyright Theodore Ts'o, 1994, 1995. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, and the entire permission notice in its entirety, 13 * including the disclaimer of warranties. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. The name of the author may not be used to endorse or promote 18 * products derived from this software without specific prior 19 * written permission. 20 * 21 * ALTERNATIVELY, this product may be distributed under the terms of 22 * the GNU Public License, in which case the provisions of the GPL are 23 * required INSTEAD OF the above restrictions. (This clause is 24 * necessary due to a potential bad interaction between the GPL and 25 * the restrictions contained in a BSD-style copyright.) 26 * 27 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED 28 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 30 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, 31 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 32 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 33 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 35 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 36 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 37 * OF THE POSSIBILITY OF SUCH DAMAGE. 38 */ 39
40 /* 41 * (now, with legal B.S. out of the way.....) 42 * 43 * This routine gathers environmental noise from device drivers, etc., 44 * and returns good random numbers, suitable for cryptographic use. 45 * Besides the obvious cryptographic uses, these numbers are also good 46 * for seeding TCP sequence numbers, and other places where it is 47 * desireable to have numbers which are not only random, but hard to 48 * predict by an attacker. 49 * 50 * Theory of operation 51 * =================== 52 * 53 * Computers are very predictable devices. Hence it is extremely hard 54 * to produce truely random numbers on a computer --- as opposed to 55 * pseudo-random numbers, which can easily generated by using a 56 * algorithm. Unfortunately, it is very easy for attackers to guess 57 * the sequence of pseudo-random number generators, and for some 58 * applications this is not acceptable. So instead, we must try to 59 * gather "environmental noise" from the computer's environment, which 60 * must be hard for outside attackers to observe, and use that to 61 * generate random numbers. In a Unix environment, this is best done 62 * from inside the kernel. 63 * 64 * Sources of randomness from the environment include inter-keyboard 65 * timings, inter-interrupt timings from some interrupts, and other 66 * events which are both (a) non-deterministic and (b) hard for an 67 * outside observer to measure. Randomness from these sources are 68 * added to an "entropy pool", which is mixed using a CRC-like function. 69 * This is not cryptographically strong, but it is adequate assuming 70 * the randomness is not chosen maliciously, and it is fast enough that 71 * the overhead of doing it on every interrupt is very reasonable. 72 * As random bytes are mixed into the entropy pool, the routines keep 73 * an *estimate* of how many bits of randomness have been stored into 74 * the random number generator's internal state. 75 * 76 * When random bytes are desired, they are obtained by taking the MD5 77 * hash of the contents of the "entropy pool". The MD5 hash avoids 78 * exposing the internal state of the entropy pool. It is believed to 79 * be computationally infeasible to derive any useful information 80 * about the input of MD5 from its output. Even if it is possible to 81 * analyze MD5 in some clever way, as long as the amount of data 82 * returned from the generator is less than the inherent entropy in 83 * the pool, the output data is totally unpredictable. For this 84 * reason, the routine decreases its internal estimate of how many 85 * bits of "true randomness" are contained in the entropy pool as it 86 * outputs random numbers. 87 * 88 * If this estimate goes to zero, the routine can still generate 89 * random numbers; however, an attacker may (at least in theory) be 90 * able to infer the future output of the generator from prior 91 * outputs. This requires successful cryptanalysis of MD5, which is 92 * not believed to be feasible, but there is a remote possiblility. 93 * Nonetheless, these numbers should be useful for the vast majority 94 * of purposes. 95 * 96 * Exported interfaces ---- output 97 * =============================== 98 * 99 * There are three exported interfaces; the first is one designed to 100 * be used from within the kernel: 101 * 102 * void get_random_bytes(void *buf, int nbytes); 103 * 104 * This interface will return the requested number of random bytes, 105 * and place it in the requested buffer. 106 * 107 * The two other interfaces are two character devices /dev/random and 108 * /dev/urandom. /dev/random is suitable for use when very high 109 * quality randomness is desired (for example, for key generation or 110 * one-time pads), as it will only return a maximum of the number of 111 * bits of randomness (as estimated by the random number generator) 112 * contained in the entropy pool. 113 * 114 * The /dev/urandom device does not have this limit, and will return 115 * as many bytes as are requested. As more and more random bytes are 116 * requested without giving time for the entropy pool to recharge, 117 * this will result in random numbers that are merely cryptographically 118 * strong. For many applications, however, this is acceptable. 119 * 120 * Exported interfaces ---- input 121 * ============================== 122 * 123 * The current exported interfaces for gathering environmental noise 124 * from the devices are: 125 * 126 * void add_keyboard_randomness(unsigned char scancode); 127 * void add_mouse_randomness(__u32 mouse_data); 128 * void add_interrupt_randomness(int irq); 129 * void add_blkdev_randomness(int irq); 130 * 131 * add_keyboard_randomness() uses the inter-keypress timing, as well as the 132 * scancode as random inputs into the "entropy pool". 133 * 134 * add_mouse_randomness() uses the mouse interrupt timing, as well as 135 * the reported position of the mouse from the hardware. 136 * 137 * add_interrupt_randomness() uses the inter-interrupt timing as random 138 * inputs to the entropy pool. Note that not all interrupts are good 139 * sources of randomness! For example, the timer interrupts is not a 140 * good choice, because the periodicity of the interrupts is to 141 * regular, and hence predictable to an attacker. Disk interrupts are 142 * a better measure, since the timing of the disk interrupts are more 143 * unpredictable. 144 * 145 * add_blkdev_randomness() times the finishing time of block requests. 146 * 147 * All of these routines try to estimate how many bits of randomness a 148 * particular randomness source. They do this by keeping track of the 149 * first and second order deltas of the event timings. 150 * 151 * Acknowledgements: 152 * ================= 153 * 154 * Ideas for constructing this random number generator were derived 155 * from the Pretty Good Privacy's random number generator, and from 156 * private discussions with Phil Karn. Colin Plumb provided a faster 157 * random number generator, which speed up the mixing function of the 158 * entropy pool, taken from PGP 3.0 (under development). It has since 159 * been modified by myself to provide better mixing in the case where 160 * the input values to add_entropy_word() are mostly small numbers. 161 * 162 * Any flaws in the design are solely my responsibility, and should 163 * not be attributed to the Phil, Colin, or any of authors of PGP. 164 * 165 * The code for MD5 transform was taken from Colin Plumb's 166 * implementation, which has been placed in the public domain. The 167 * MD5 cryptographic checksum was devised by Ronald Rivest, and is 168 * documented in RFC 1321, "The MD5 Message Digest Algorithm". 169 * 170 * Further background information on this topic may be obtained from 171 * RFC 1750, "Randomness Recommendations for Security", by Donald 172 * Eastlake, Steve Crocker, and Jeff Schiller. 173 */ 174
175 #include <linux/sched.h>
176 #include <linux/kernel.h>
177 #include <linux/major.h>
178 #include <linux/string.h>
179 #include <linux/fcntl.h>
180 #include <linux/malloc.h>
181 #include <linux/random.h>
182
183 #include <asm/segment.h>
184 #include <asm/irq.h>
185 #include <asm/io.h>
186
187 /* 188 * The pool is stirred with a primitive polynomial of degree 128 189 * over GF(2), namely x^128 + x^119 + x^72 + x^64 + x^14 + x^8 + 1. 190 * For a pool of size 64, try x^64+x^62+x^38+x^10+x^6+x+1. 191 */ 192 #definePOOLWORDS 128 /* Power of 2 - note that this is 32-bit words */ 193 #definePOOLBITS (POOLWORDS*32)
194 #ifPOOLWORDS == 128
195 #defineTAP1 119 /* The polynomial taps */ 196 #defineTAP2 72
197 #defineTAP3 64
198 #defineTAP4 14
199 #defineTAP5 8
200 #elifPOOLWORDS == 64
201 #defineTAP1 62 /* The polynomial taps */ 202 #defineTAP2 38
203 #defineTAP3 10
204 #defineTAP4 6
205 #defineTAP5 1
206 #else 207 #error No primitive polynomial available for chosen POOLWORDS
208 #endif 209
210 /* There is actually only one of these, globally. */ 211 structrandom_bucket{ 212 unsignedadd_ptr;
213 unsignedentropy_count;
214 intinput_rotate;
215 __u32 *pool;
216 };
217
218 /* There is one of these per entropy source */ 219 structtimer_rand_state{ 220 unsignedlonglast_time;
221 intlast_delta;
222 intnbits;
223 };
224
225 staticstructrandom_bucketrandom_state;
226 static__u32random_pool[POOLWORDS];
227 staticstructtimer_rand_statekeyboard_timer_state;
228 staticstructtimer_rand_statemouse_timer_state;
229 staticstructtimer_rand_stateextract_timer_state;
230 staticstructtimer_rand_state *irq_timer_state[NR_IRQS];
231 staticstructtimer_rand_state *blkdev_timer_state[MAX_BLKDEV];
232 staticstructwait_queue *random_wait;
233
234 #ifndefMIN 235 #defineMIN(a,b) (((a) < (b)) ? (a) : (b))
236 #endif 237
238 voidrand_initialize(void)
/* */ 239 { 240 random_state.add_ptr = 0;
241 random_state.entropy_count = 0;
242 random_state.pool = random_pool;
243 memset(irq_timer_state, 0, sizeof(irq_timer_state));
244 memset(blkdev_timer_state, 0, sizeof(blkdev_timer_state));
245 random_wait = NULL;} 246
247 voidrand_initialize_irq(intirq)
/* */ 248 { 249 if (irq >= NR_IRQS || irq_timer_state[irq])
250 return;
251
252 /* 253 * If kamlloc returns null, we just won't use that entropy 254 * source. 255 */ 256 irq_timer_state[irq] = kmalloc(sizeof(structtimer_rand_state),
257 GFP_KERNEL);
258 } 259
260 voidrand_initialize_blkdev(intmajor)
/* */ 261 { 262 if (major >= MAX_BLKDEV || blkdev_timer_state[major])
263 return;
264
265 /* 266 * If kamlloc returns null, we just won't use that entropy 267 * source. 268 */ 269 blkdev_timer_state[major] = kmalloc(sizeof(structtimer_rand_state),
270 GFP_KERNEL);
271 } 272
273 /* 274 * This function adds a byte into the entropy "pool". It does not 275 * update the entropy estimate. The caller must do this if appropriate. 276 * 277 * The pool is stirred with a primitive polynomial of degree 128 278 * over GF(2), namely x^128 + x^119 + x^72 + x^64 + x^14 + x^8 + 1. 279 * For a pool of size 64, try x^64+x^62+x^38+x^10+x^6+x+1. 280 * 281 * We rotate the input word by a changing number of bits, to help 282 * assure that all bits in the entropy get toggled. Otherwise, if we 283 * consistently feed the entropy pool small numbers (like jiffies and 284 * scancodes, for example), the upper bits of the entropy pool don't 285 * get affected. --- TYT, 10/11/95 286 */ 287 staticinlinevoidadd_entropy_word(structrandom_bucket *r,
/* */ 288 const__u32input)
289 { 290 unsignedi;
291 __u32w;
292
293 w = (input << r->input_rotate) | (input >> (32 - r->input_rotate));
294 i = r->add_ptr = (r->add_ptr - 1) & (POOLWORDS-1);
295 if (i)
296 r->input_rotate = (r->input_rotate + 7) & 31;
297 else 298 /* 299 * At the beginning of the pool, add an extra 7 bits 300 * rotation, so that successive passes spread the 301 * input bits across the pool evenly. 302 */ 303 r->input_rotate = (r->input_rotate + 14) & 31;
304
305 /* XOR in the various taps */ 306 w ^= r->pool[(i+TAP1)&(POOLWORDS-1)];
307 w ^= r->pool[(i+TAP2)&(POOLWORDS-1)];
308 w ^= r->pool[(i+TAP3)&(POOLWORDS-1)];
309 w ^= r->pool[(i+TAP4)&(POOLWORDS-1)];
310 w ^= r->pool[(i+TAP5)&(POOLWORDS-1)];
311 w ^= r->pool[i];
312 /* Rotate w left 1 bit (stolen from SHA) and store */ 313 r->pool[i] = (w << 1) | (w >> 31);
314 } 315
316 /* 317 * This function adds entropy to the entropy "pool" by using timing 318 * delays. It uses the timer_rand_state structure to make an estimate 319 * of how many bits of entropy this call has added to the pool. 320 * 321 * The number "num" is also added to the pool - it should somehow describe 322 * the type of event which just happened. This is currently 0-255 for 323 * keyboard scan codes, and 256 upwards for interrupts. 324 * On the i386, this is assumed to be at most 16 bits, and the high bits 325 * are used for a high-resolution timer. 326 * 327 * TODO: Read the time stamp register on the Pentium. 328 */ 329 staticvoidadd_timer_randomness(structrandom_bucket *r,
/* */ 330 structtimer_rand_state *state, unsignednum)
331 { 332 intdelta, delta2;
333 unsignednbits;
334 __u32time;
335
336 #ifdefined (__i386__)
337 if (x86_capability & 16) { 338 unsignedlonglow, high;
339 __asm__(".byte 0x0f,0x31"
340 :"=a" (low), "=d" (high));
341 time = (__u32) low;
342 num ^= (__u32) high;
343 }else{ 344 #if 0
345 /* 346 * On a 386, read the high resolution timer. We assume that 347 * this gives us 2 bits of randomness. 348 * 349 * This is turned off for now because of the speed hit 350 * it entails. 351 */ 352 outb_p(0x00, 0x43); /* latch the count ASAP */ 353 num |= inb_p(0x40) << 16;
354 num |= inb(0x40) << 24;
355 r->entropy_count += 2;
356 #endif 357
358 time = jiffies;
359 } 360 #else 361 time = jiffies;
362 #endif 363
364 add_entropy_word(r, (__u32) num);
365 add_entropy_word(r, time);
366
367 /* 368 * Calculate number of bits of randomness we probably 369 * added. We take into account the first and second order 370 * deltas in order to make our estimate. 371 */ 372 delta = time - state->last_time;
373 state->last_time = time;
374
375 delta2 = delta - state->last_delta;
376 state->last_delta = delta;
377
378 if (delta < 0) delta = -delta;
379 if (delta2 < 0) delta2 = -delta2;
380 delta = MIN(delta, delta2) >> 1;
381 for (nbits = 0; delta; nbits++)
382 delta >>= 1;
383
384 r->entropy_count += nbits;
385
386 /* Prevent overflow */ 387 if (r->entropy_count > POOLBITS)
388 r->entropy_count = POOLBITS;
389
390 wake_up_interruptible(&random_wait);
391 } 392
393 voidadd_keyboard_randomness(unsignedcharscancode)
/* */ 394 { 395 add_timer_randomness(&random_state, &keyboard_timer_state, scancode);
396 } 397
398 voidadd_mouse_randomness(__u32mouse_data)
/* */ 399 { 400 add_timer_randomness(&random_state, &mouse_timer_state, mouse_data);
401 } 402
403 voidadd_interrupt_randomness(intirq)
/* */ 404 { 405 if (irq >= NR_IRQS || irq_timer_state[irq] == 0)
406 return;
407
408 add_timer_randomness(&random_state, irq_timer_state[irq], 0x100+irq);
409 } 410
411 voidadd_blkdev_randomness(intmajor)
/* */ 412 { 413 if (major >= MAX_BLKDEV || blkdev_timer_state[major] == 0)
414 return;
415
416 add_timer_randomness(&random_state, blkdev_timer_state[major],
417 0x200+major);
418 } 419
420 /* 421 * MD5 transform algorithm, taken from code written by Colin Plumb, 422 * and put into the public domain 423 * 424 * QUESTION: Replace this with SHA, which as generally received better 425 * reviews from the cryptographic community? 426 */ 427
428 /* The four core functions - F1 is optimized somewhat */ 429
430 /* #define F1(x, y, z) (x & y | ~x & z) */ 431 #defineF1(x, y, z) (z ^ (x & (y ^ z)))
432 #defineF2(x, y, z) F1(z, x, y)
433 #defineF3(x, y, z) (x ^ y ^ z)
434 #defineF4(x, y, z) (y ^ (x | ~z))
435
436 /* This is the central step in the MD5 algorithm. */ 437 #defineMD5STEP(f, w, x, y, z, data, s) \
438 ( w += f(x, y, z) + data, w = w<<s | w>>(32-s), w += x )
439
440 /* 441 * The core of the MD5 algorithm, this alters an existing MD5 hash to 442 * reflect the addition of 16 longwords of new data. MD5Update blocks 443 * the data and converts bytes into longwords for this routine. 444 */ 445 staticvoidMD5Transform(__u32buf[4],
/* */ 446 __u32constin[16])
447 { 448 __u32a, b, c, d;
449
450 a = buf[0];
451 b = buf[1];
452 c = buf[2];
453 d = buf[3];
454
455 MD5STEP(F1, a, b, c, d, in[ 0]+0xd76aa478, 7);
456 MD5STEP(F1, d, a, b, c, in[ 1]+0xe8c7b756, 12);
457 MD5STEP(F1, c, d, a, b, in[ 2]+0x242070db, 17);
458 MD5STEP(F1, b, c, d, a, in[ 3]+0xc1bdceee, 22);
459 MD5STEP(F1, a, b, c, d, in[ 4]+0xf57c0faf, 7);
460 MD5STEP(F1, d, a, b, c, in[ 5]+0x4787c62a, 12);
461 MD5STEP(F1, c, d, a, b, in[ 6]+0xa8304613, 17);
462 MD5STEP(F1, b, c, d, a, in[ 7]+0xfd469501, 22);
463 MD5STEP(F1, a, b, c, d, in[ 8]+0x698098d8, 7);
464 MD5STEP(F1, d, a, b, c, in[ 9]+0x8b44f7af, 12);
465 MD5STEP(F1, c, d, a, b, in[10]+0xffff5bb1, 17);
466 MD5STEP(F1, b, c, d, a, in[11]+0x895cd7be, 22);
467 MD5STEP(F1, a, b, c, d, in[12]+0x6b901122, 7);
468 MD5STEP(F1, d, a, b, c, in[13]+0xfd987193, 12);
469 MD5STEP(F1, c, d, a, b, in[14]+0xa679438e, 17);
470 MD5STEP(F1, b, c, d, a, in[15]+0x49b40821, 22);
471
472 MD5STEP(F2, a, b, c, d, in[ 1]+0xf61e2562, 5);
473 MD5STEP(F2, d, a, b, c, in[ 6]+0xc040b340, 9);
474 MD5STEP(F2, c, d, a, b, in[11]+0x265e5a51, 14);
475 MD5STEP(F2, b, c, d, a, in[ 0]+0xe9b6c7aa, 20);
476 MD5STEP(F2, a, b, c, d, in[ 5]+0xd62f105d, 5);
477 MD5STEP(F2, d, a, b, c, in[10]+0x02441453, 9);
478 MD5STEP(F2, c, d, a, b, in[15]+0xd8a1e681, 14);
479 MD5STEP(F2, b, c, d, a, in[ 4]+0xe7d3fbc8, 20);
480 MD5STEP(F2, a, b, c, d, in[ 9]+0x21e1cde6, 5);
481 MD5STEP(F2, d, a, b, c, in[14]+0xc33707d6, 9);
482 MD5STEP(F2, c, d, a, b, in[ 3]+0xf4d50d87, 14);
483 MD5STEP(F2, b, c, d, a, in[ 8]+0x455a14ed, 20);
484 MD5STEP(F2, a, b, c, d, in[13]+0xa9e3e905, 5);
485 MD5STEP(F2, d, a, b, c, in[ 2]+0xfcefa3f8, 9);
486 MD5STEP(F2, c, d, a, b, in[ 7]+0x676f02d9, 14);
487 MD5STEP(F2, b, c, d, a, in[12]+0x8d2a4c8a, 20);
488
489 MD5STEP(F3, a, b, c, d, in[ 5]+0xfffa3942, 4);
490 MD5STEP(F3, d, a, b, c, in[ 8]+0x8771f681, 11);
491 MD5STEP(F3, c, d, a, b, in[11]+0x6d9d6122, 16);
492 MD5STEP(F3, b, c, d, a, in[14]+0xfde5380c, 23);
493 MD5STEP(F3, a, b, c, d, in[ 1]+0xa4beea44, 4);
494 MD5STEP(F3, d, a, b, c, in[ 4]+0x4bdecfa9, 11);
495 MD5STEP(F3, c, d, a, b, in[ 7]+0xf6bb4b60, 16);
496 MD5STEP(F3, b, c, d, a, in[10]+0xbebfbc70, 23);
497 MD5STEP(F3, a, b, c, d, in[13]+0x289b7ec6, 4);
498 MD5STEP(F3, d, a, b, c, in[ 0]+0xeaa127fa, 11);
499 MD5STEP(F3, c, d, a, b, in[ 3]+0xd4ef3085, 16);
500 MD5STEP(F3, b, c, d, a, in[ 6]+0x04881d05, 23);
501 MD5STEP(F3, a, b, c, d, in[ 9]+0xd9d4d039, 4);
502 MD5STEP(F3, d, a, b, c, in[12]+0xe6db99e5, 11);
503 MD5STEP(F3, c, d, a, b, in[15]+0x1fa27cf8, 16);
504 MD5STEP(F3, b, c, d, a, in[ 2]+0xc4ac5665, 23);
505
506 MD5STEP(F4, a, b, c, d, in[ 0]+0xf4292244, 6);
507 MD5STEP(F4, d, a, b, c, in[ 7]+0x432aff97, 10);
508 MD5STEP(F4, c, d, a, b, in[14]+0xab9423a7, 15);
509 MD5STEP(F4, b, c, d, a, in[ 5]+0xfc93a039, 21);
510 MD5STEP(F4, a, b, c, d, in[12]+0x655b59c3, 6);
511 MD5STEP(F4, d, a, b, c, in[ 3]+0x8f0ccc92, 10);
512 MD5STEP(F4, c, d, a, b, in[10]+0xffeff47d, 15);
513 MD5STEP(F4, b, c, d, a, in[ 1]+0x85845dd1, 21);
514 MD5STEP(F4, a, b, c, d, in[ 8]+0x6fa87e4f, 6);
515 MD5STEP(F4, d, a, b, c, in[15]+0xfe2ce6e0, 10);
516 MD5STEP(F4, c, d, a, b, in[ 6]+0xa3014314, 15);
517 MD5STEP(F4, b, c, d, a, in[13]+0x4e0811a1, 21);
518 MD5STEP(F4, a, b, c, d, in[ 4]+0xf7537e82, 6);
519 MD5STEP(F4, d, a, b, c, in[11]+0xbd3af235, 10);
520 MD5STEP(F4, c, d, a, b, in[ 2]+0x2ad7d2bb, 15);
521 MD5STEP(F4, b, c, d, a, in[ 9]+0xeb86d391, 21);
522
523 buf[0] += a;
524 buf[1] += b;
525 buf[2] += c;
526 buf[3] += d;
527 } 528
529 #undefF1 530 #undefF2 531 #undefF3 532 #undefF4 533 #undefMD5STEP 534
535
536 #ifPOOLWORDS % 16
537 #error extract_entropy() assumes that POOLWORDS is a multiple of 16 words.
538 #endif 539 /* 540 * This function extracts randomness from the "entropy pool", and 541 * returns it in a buffer. This function computes how many remaining 542 * bits of entropy are left in the pool, but it does not restrict the 543 * number of bytes that are actually obtained. 544 */ 545 staticinlineintextract_entropy(structrandom_bucket *r, char * buf,
/* */ 546 intnbytes, intto_user)
547 { 548 intret, i;
549 __u32tmp[4];
550
551 add_timer_randomness(r, &extract_timer_state, nbytes);
552
553 /* Redundant, but just in case... */ 554 if (r->entropy_count > POOLBITS)
555 r->entropy_count = POOLBITS;
556 /* Why is this here? Left in from Ted Ts'o. Perhaps to limit time. */ 557 if (nbytes > 32768)
558 nbytes = 32768;
559
560 ret = nbytes;
561 if (r->entropy_count / 8 >= nbytes)
562 r->entropy_count -= nbytes*8;
563 else 564 r->entropy_count = 0;
565
566 while (nbytes) { 567 /* Hash the pool to get the output */ 568 tmp[0] = 0x67452301;
569 tmp[1] = 0xefcdab89;
570 tmp[2] = 0x98badcfe;
571 tmp[3] = 0x10325476;
572 for (i = 0; i < POOLWORDS; i += 16)
573 MD5Transform(tmp, r->pool+i);
574 /* Modify pool so next hash will produce different results */ 575 add_entropy_word(r, tmp[0]);
576 add_entropy_word(r, tmp[1]);
577 add_entropy_word(r, tmp[2]);
578 add_entropy_word(r, tmp[3]);
579 /* 580 * Run the MD5 Transform one more time, since we want 581 * to add at least minimal obscuring of the inputs to 582 * add_entropy_word(). --- TYT 583 */ 584 MD5Transform(tmp, r->pool);
585
586 /* Copy data to destination buffer */ 587 i = MIN(nbytes, 16);
588 if (to_user)
589 memcpy_tofs(buf, (__u8const *)tmp, i);
590 else 591 memcpy(buf, (__u8const *)tmp, i);
592 nbytes -= i;
593 buf += i;
594 } 595
596 /* Wipe data from memory */ 597 memset(tmp, 0, sizeof(tmp));
598
599 returnret;
600 } 601
602 /* 603 * This function is the exported kernel interface. It returns some 604 * number of good random numbers, suitable for seeding TCP sequence 605 * numbers, etc. 606 */ 607 voidget_random_bytes(void *buf, intnbytes)
/* */ 608 { 609 extract_entropy(&random_state, (char *) buf, nbytes, 0);
610 } 611
612 intread_random(structinode * inode, structfile * file,
/* */ 613 char * buf, intnbytes)
614 { 615 if (nbytes > random_state.entropy_count / 8)
616 nbytes = random_state.entropy_count / 8;
617
618 returnextract_entropy(&random_state, buf, nbytes, 1);
619 } 620
621 intread_random_unlimited(structinode * inode, structfile * file,
/* */ 622 char * buf, intnbytes)
623 { 624 returnextract_entropy(&random_state, buf, nbytes, 1);
625 } 626
627 intwrite_random(structinode * inode, structfile * file,
/* */ 628 constchar * buffer, intcount)
629 { 630 inti;
631 __u32word, *p;
632
633 for (i = count, p = (__u32 *)buffer;
634 i >= sizeof(__u32);
635 i-= sizeof(__u32), p++) { 636 memcpy_fromfs(&word, p, sizeof(__u32));
637 add_entropy_word(&random_state, word);
638 } 639 if (i) { 640 word = 0;
641 memcpy_fromfs(&word, p, i);
642 add_entropy_word(&random_state, word);
643 } 644 inode->i_mtime = CURRENT_TIME;
645 returncount;
646 } 647
648 intrandom_ioctl(structinode * inode, structfile * file,
/* */ 649 unsignedintcmd, unsignedlongarg)
650 { 651 int *p, max_size;
652
653 switch (cmd) { 654 caseRNDGETENTCNT:
655 put_user(random_state.entropy_count, (int *) arg);
656 return 0;
657 caseRNDADDTOENTCNT:
658 if (!suser())
659 return -EPERM;
660 random_state.entropy_count += get_user((int *) arg);
661 if (random_state.entropy_count > POOLBITS)
662 random_state.entropy_count = POOLBITS;
663 return 0;
664 caseRNDGETPOOL:
665 if (!suser())
666 return -EPERM;
667 p = (int *) arg;
668 put_user(random_state.entropy_count, p);
669 max_size = get_user(++p);
670 put_user(POOLWORDS, p);
671 if (max_size < 0)
672 return -EINVAL;
673 if (max_size > POOLWORDS)
674 max_size = POOLWORDS;
675 memcpy_tofs(++p, random_state.pool,
676 max_size*sizeof(__u32));
677 return 0;
678 default:
679 return -EINVAL;
680 } 681 }