2 * kern_random.c -- A strong random number generator
6 * Version 0.95, last modified 18-Oct-95
8 * Copyright Theodore Ts'o, 1994, 1995. All rights reserved.
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42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/kernel.h>
47 #include <sys/random.h>
48 #include <sys/systm.h>
49 #include <sys/select.h>
50 #include <sys/timetc.h>
52 #include <machine/ipl.h>
53 #include <machine/mutex.h>
56 #include <i386/isa/icu.h>
60 XXX the below should be used. However there is too much "16"
61 hardcodeing in kern_random.c right now. -- obrien
62 #include <machine/ipl.h>
64 #define ICU_LEN (NHWI)
66 #define ICU_LEN (NSWI)
75 * The pool is stirred with a primitive polynomial of degree 128
76 * over GF(2), namely x^128 + x^99 + x^59 + x^31 + x^9 + x^7 + 1.
77 * For a pool of size 64, try x^64+x^62+x^38+x^10+x^6+x+1.
79 #define POOLWORDS 128 /* Power of 2 - note that this is 32-bit words */
80 #define POOLBITS (POOLWORDS*32)
83 #define TAP1 99 /* The polynomial taps */
89 #define TAP1 62 /* The polynomial taps */
95 #error No primitive polynomial available for chosen POOLWORDS
98 #define WRITEBUFFER 512 /* size in bytes */
100 /* There is actually only one of these, globally. */
101 struct random_bucket {
109 /* There is one of these per entropy source */
110 struct timer_rand_state {
116 static struct random_bucket random_state;
117 static u_int32_t random_pool[POOLWORDS];
118 static struct timer_rand_state keyboard_timer_state;
119 static struct timer_rand_state extract_timer_state;
120 static struct timer_rand_state irq_timer_state[ICU_LEN];
122 static struct timer_rand_state blkdev_timer_state[MAX_BLKDEV];
124 static struct wait_queue *random_wait;
127 #define MIN(a,b) (((a) < (b)) ? (a) : (b))
131 rand_initialize(void)
133 random_state.add_ptr = 0;
134 random_state.entropy_count = 0;
135 random_state.pool = random_pool;
137 random_state.rsel.si_flags = 0;
138 random_state.rsel.si_pid = 0;
142 * This function adds an int into the entropy "pool". It does not
143 * update the entropy estimate. The caller must do this if appropriate.
145 * The pool is stirred with a primitive polynomial of degree 128
146 * over GF(2), namely x^128 + x^99 + x^59 + x^31 + x^9 + x^7 + 1.
147 * For a pool of size 64, try x^64+x^62+x^38+x^10+x^6+x+1.
149 * We rotate the input word by a changing number of bits, to help
150 * assure that all bits in the entropy get toggled. Otherwise, if we
151 * consistently feed the entropy pool small numbers (like ticks and
152 * scancodes, for example), the upper bits of the entropy pool don't
153 * get affected. --- TYT, 10/11/95
156 add_entropy_word(struct random_bucket *r, const u_int32_t input)
161 w = (input << r->input_rotate) | (input >> (32 - r->input_rotate));
162 i = r->add_ptr = (r->add_ptr - 1) & (POOLWORDS-1);
164 r->input_rotate = (r->input_rotate + 7) & 31;
167 * At the beginning of the pool, add an extra 7 bits
168 * rotation, so that successive passes spread the
169 * input bits across the pool evenly.
171 r->input_rotate = (r->input_rotate + 14) & 31;
173 /* XOR in the various taps */
174 w ^= r->pool[(i+TAP1)&(POOLWORDS-1)];
175 w ^= r->pool[(i+TAP2)&(POOLWORDS-1)];
176 w ^= r->pool[(i+TAP3)&(POOLWORDS-1)];
177 w ^= r->pool[(i+TAP4)&(POOLWORDS-1)];
178 w ^= r->pool[(i+TAP5)&(POOLWORDS-1)];
180 /* Rotate w left 1 bit (stolen from SHA) and store */
181 r->pool[i] = (w << 1) | (w >> 31);
185 * This function adds entropy to the entropy "pool" by using timing
186 * delays. It uses the timer_rand_state structure to make an estimate
187 * of how any bits of entropy this call has added to the pool.
189 * The number "num" is also added to the pool - it should somehow describe
190 * the type of event which just happened. This is currently 0-255 for
191 * keyboard scan codes, and 256 upwards for interrupts.
192 * On the i386, this is assumed to be at most 16 bits, and the high bits
193 * are used for a high-resolution timer.
196 add_timer_randomness(struct random_bucket *r, struct timer_rand_state *state,
203 num ^= timecounter->tc_get_timecount(timecounter) << 16;
204 r->entropy_count += 2;
208 add_entropy_word(r, (u_int32_t) num);
209 add_entropy_word(r, time);
212 * Calculate number of bits of randomness we probably
213 * added. We take into account the first and second order
214 * deltas in order to make our estimate.
216 delta = time - state->last_time;
217 state->last_time = time;
219 delta2 = delta - state->last_delta;
220 state->last_delta = delta;
222 if (delta < 0) delta = -delta;
223 if (delta2 < 0) delta2 = -delta2;
224 delta = MIN(delta, delta2) >> 1;
225 for (nbits = 0; delta; nbits++)
228 r->entropy_count += nbits;
230 /* Prevent overflow */
231 if (r->entropy_count > POOLBITS)
232 r->entropy_count = POOLBITS;
234 if (r->entropy_count >= 8)
235 selwakeup(&random_state.rsel);
239 add_keyboard_randomness(u_char scancode)
241 add_timer_randomness(&random_state, &keyboard_timer_state, scancode);
245 add_interrupt_randomness(void *vsc)
248 struct random_softc *sc = vsc;
250 (sc->sc_handler)(sc->sc_arg);
252 add_timer_randomness(&random_state, &irq_timer_state[intr], intr);
257 add_blkdev_randomness(int major)
259 if (major >= MAX_BLKDEV)
262 add_timer_randomness(&random_state, &blkdev_timer_state[major],
268 #error extract_entropy() assumes that POOLWORDS is a multiple of 16 words.
271 * This function extracts randomness from the "entropy pool", and
272 * returns it in a buffer. This function computes how many remaining
273 * bits of entropy are left in the pool, but it does not restrict the
274 * number of bytes that are actually obtained.
277 extract_entropy(struct random_bucket *r, char *buf, int nbytes)
282 add_timer_randomness(r, &extract_timer_state, nbytes);
284 /* Redundant, but just in case... */
285 if (r->entropy_count > POOLBITS)
286 r->entropy_count = POOLBITS;
287 /* Why is this here? Left in from Ted Ts'o. Perhaps to limit time. */
292 if (r->entropy_count / 8 >= nbytes)
293 r->entropy_count -= nbytes*8;
295 r->entropy_count = 0;
298 /* Hash the pool to get the output */
303 for (i = 0; i < POOLWORDS; i += 16)
304 MD5Transform(tmp, (char *)(r->pool+i));
305 /* Modify pool so next hash will produce different results */
306 add_entropy_word(r, tmp[0]);
307 add_entropy_word(r, tmp[1]);
308 add_entropy_word(r, tmp[2]);
309 add_entropy_word(r, tmp[3]);
311 * Run the MD5 Transform one more time, since we want
312 * to add at least minimal obscuring of the inputs to
313 * add_entropy_word(). --- TYT
315 MD5Transform(tmp, (char *)(r->pool));
317 /* Copy data to destination buffer */
324 /* Wipe data from memory */
325 bzero(tmp, sizeof(tmp));
330 #ifdef notused /* XXX NOT the exported kernel interface */
332 * This function is the exported kernel interface. It returns some
333 * number of good random numbers, suitable for seeding TCP sequence
337 get_random_bytes(void *buf, u_int nbytes)
339 extract_entropy(&random_state, (char *) buf, nbytes);
344 read_random(void *buf, u_int nbytes)
346 if ((nbytes * 8) > random_state.entropy_count)
347 nbytes = random_state.entropy_count / 8;
349 return extract_entropy(&random_state, (char *)buf, nbytes);
353 read_random_unlimited(void *buf, u_int nbytes)
355 return extract_entropy(&random_state, (char *)buf, nbytes);
360 write_random(const char *buf, u_int nbytes)
365 for (i = nbytes, p = (u_int32_t *)buf;
366 i >= sizeof(u_int32_t);
367 i-= sizeof(u_int32_t), p++)
368 add_entropy_word(&random_state, *p);
372 add_entropy_word(&random_state, word);
379 random_poll(dev_t dev, int events, struct proc *p)
383 mtx_enter_sched_quick();
384 if (events & (POLLIN | POLLRDNORM)) {
385 if (random_state.entropy_count >= 8)
386 revents |= events & (POLLIN | POLLRDNORM);
388 selrecord(p, &random_state.rsel);
390 mtx_exit_sched_quick();
391 if (events & (POLLOUT | POLLWRNORM))
392 revents |= events & (POLLOUT | POLLWRNORM); /* heh */