394 lines
10 KiB
C
394 lines
10 KiB
C
/*
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* kern_random.c -- A strong random number generator
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*
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* $FreeBSD$
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*
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* Version 0.95, last modified 18-Oct-95
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*
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* Copyright Theodore Ts'o, 1994, 1995. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, and the entire permission notice in its entirety,
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* including the disclaimer of warranties.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote
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* products derived from this software without specific prior
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* written permission.
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*
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* ALTERNATIVELY, this product may be distributed under the terms of
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* the GNU Public License, in which case the provisions of the GPL are
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* required INSTEAD OF the above restrictions. (This clause is
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* necessary due to a potential bad interaction between the GPL and
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* the restrictions contained in a BSD-style copyright.)
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/select.h>
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#include <sys/poll.h>
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#include <sys/timetc.h>
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#include <sys/md5.h>
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#include <sys/random.h>
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#ifdef __i386__
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#include <i386/isa/icu.h>
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#endif
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#ifdef __alpha__
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/*
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XXX the below should be used. However there is too much "16"
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hardcodeing in kern_random.c right now. -- obrien
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#include <machine/ipl.h>
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#if NHWI > 0
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#define ICU_LEN (NHWI)
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#else
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#define ICU_LEN (NSWI)
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#endif
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*/
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#define ICU_LEN 16
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#endif
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#define MAX_BLKDEV 4
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/*
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* The pool is stirred with a primitive polynomial of degree 128
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* over GF(2), namely x^128 + x^99 + x^59 + x^31 + x^9 + x^7 + 1.
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* For a pool of size 64, try x^64+x^62+x^38+x^10+x^6+x+1.
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*/
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#define POOLWORDS 128 /* Power of 2 - note that this is 32-bit words */
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#define POOLBITS (POOLWORDS*32)
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#if POOLWORDS == 128
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#define TAP1 99 /* The polynomial taps */
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#define TAP2 59
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#define TAP3 31
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#define TAP4 9
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#define TAP5 7
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#elif POOLWORDS == 64
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#define TAP1 62 /* The polynomial taps */
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#define TAP2 38
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#define TAP3 10
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#define TAP4 6
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#define TAP5 1
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#else
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#error No primitive polynomial available for chosen POOLWORDS
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#endif
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#define WRITEBUFFER 512 /* size in bytes */
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/* There is actually only one of these, globally. */
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struct random_bucket {
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u_int add_ptr;
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u_int entropy_count;
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int input_rotate;
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u_int32_t *pool;
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struct selinfo rsel;
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};
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/* There is one of these per entropy source */
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struct timer_rand_state {
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u_long last_time;
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int last_delta;
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int nbits;
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};
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static struct random_bucket random_state;
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static u_int32_t random_pool[POOLWORDS];
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static struct timer_rand_state keyboard_timer_state;
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static struct timer_rand_state extract_timer_state;
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static struct timer_rand_state irq_timer_state[ICU_LEN];
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#ifdef notyet
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static struct timer_rand_state blkdev_timer_state[MAX_BLKDEV];
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#endif
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static struct wait_queue *random_wait;
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#ifndef MIN
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#define MIN(a,b) (((a) < (b)) ? (a) : (b))
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#endif
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void
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rand_initialize(void)
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{
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random_state.add_ptr = 0;
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random_state.entropy_count = 0;
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random_state.pool = random_pool;
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random_wait = NULL;
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random_state.rsel.si_flags = 0;
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random_state.rsel.si_pid = 0;
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}
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/*
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* This function adds an int into the entropy "pool". It does not
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* update the entropy estimate. The caller must do this if appropriate.
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*
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* The pool is stirred with a primitive polynomial of degree 128
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* over GF(2), namely x^128 + x^99 + x^59 + x^31 + x^9 + x^7 + 1.
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* For a pool of size 64, try x^64+x^62+x^38+x^10+x^6+x+1.
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*
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* We rotate the input word by a changing number of bits, to help
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* assure that all bits in the entropy get toggled. Otherwise, if we
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* consistently feed the entropy pool small numbers (like ticks and
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* scancodes, for example), the upper bits of the entropy pool don't
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* get affected. --- TYT, 10/11/95
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*/
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static __inline void
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add_entropy_word(struct random_bucket *r, const u_int32_t input)
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{
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u_int i;
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u_int32_t w;
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w = (input << r->input_rotate) | (input >> (32 - r->input_rotate));
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i = r->add_ptr = (r->add_ptr - 1) & (POOLWORDS-1);
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if (i)
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r->input_rotate = (r->input_rotate + 7) & 31;
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else
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/*
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* At the beginning of the pool, add an extra 7 bits
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* rotation, so that successive passes spread the
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* input bits across the pool evenly.
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*/
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r->input_rotate = (r->input_rotate + 14) & 31;
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/* XOR in the various taps */
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w ^= r->pool[(i+TAP1)&(POOLWORDS-1)];
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w ^= r->pool[(i+TAP2)&(POOLWORDS-1)];
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w ^= r->pool[(i+TAP3)&(POOLWORDS-1)];
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w ^= r->pool[(i+TAP4)&(POOLWORDS-1)];
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w ^= r->pool[(i+TAP5)&(POOLWORDS-1)];
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w ^= r->pool[i];
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/* Rotate w left 1 bit (stolen from SHA) and store */
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r->pool[i] = (w << 1) | (w >> 31);
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}
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/*
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* This function adds entropy to the entropy "pool" by using timing
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* delays. It uses the timer_rand_state structure to make an estimate
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* of how any bits of entropy this call has added to the pool.
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*
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* The number "num" is also added to the pool - it should somehow describe
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* the type of event which just happened. This is currently 0-255 for
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* keyboard scan codes, and 256 upwards for interrupts.
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* On the i386, this is assumed to be at most 16 bits, and the high bits
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* are used for a high-resolution timer.
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*/
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static void
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add_timer_randomness(struct random_bucket *r, struct timer_rand_state *state,
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u_int num)
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{
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int delta, delta2;
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u_int nbits;
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u_int32_t time;
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num ^= timecounter->tc_get_timecount(timecounter) << 16;
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r->entropy_count += 2;
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time = ticks;
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add_entropy_word(r, (u_int32_t) num);
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add_entropy_word(r, time);
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/*
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* Calculate number of bits of randomness we probably
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* added. We take into account the first and second order
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* deltas in order to make our estimate.
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*/
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delta = time - state->last_time;
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state->last_time = time;
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delta2 = delta - state->last_delta;
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state->last_delta = delta;
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if (delta < 0) delta = -delta;
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if (delta2 < 0) delta2 = -delta2;
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delta = MIN(delta, delta2) >> 1;
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for (nbits = 0; delta; nbits++)
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delta >>= 1;
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r->entropy_count += nbits;
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/* Prevent overflow */
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if (r->entropy_count > POOLBITS)
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r->entropy_count = POOLBITS;
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if (r->entropy_count >= 8)
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selwakeup(&random_state.rsel);
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}
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void
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add_keyboard_randomness(u_char scancode)
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{
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add_timer_randomness(&random_state, &keyboard_timer_state, scancode);
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}
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void
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add_interrupt_randomness(void *vsc)
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{
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int intr;
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struct random_softc *sc = vsc;
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(sc->sc_handler)(sc->sc_arg);
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intr = sc->sc_intr;
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add_timer_randomness(&random_state, &irq_timer_state[intr], intr);
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}
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#ifdef notused
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void
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add_blkdev_randomness(int major)
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{
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if (major >= MAX_BLKDEV)
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return;
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add_timer_randomness(&random_state, &blkdev_timer_state[major],
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0x200+major);
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}
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#endif /* notused */
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#if POOLWORDS % 16
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#error extract_entropy() assumes that POOLWORDS is a multiple of 16 words.
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#endif
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/*
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* This function extracts randomness from the "entropy pool", and
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* returns it in a buffer. This function computes how many remaining
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* bits of entropy are left in the pool, but it does not restrict the
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* number of bytes that are actually obtained.
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*/
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static __inline int
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extract_entropy(struct random_bucket *r, char *buf, int nbytes)
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{
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int ret, i;
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u_int32_t tmp[4];
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add_timer_randomness(r, &extract_timer_state, nbytes);
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/* Redundant, but just in case... */
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if (r->entropy_count > POOLBITS)
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r->entropy_count = POOLBITS;
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/* Why is this here? Left in from Ted Ts'o. Perhaps to limit time. */
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if (nbytes > 32768)
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nbytes = 32768;
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ret = nbytes;
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if (r->entropy_count / 8 >= nbytes)
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r->entropy_count -= nbytes*8;
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else
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r->entropy_count = 0;
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while (nbytes) {
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/* Hash the pool to get the output */
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tmp[0] = 0x67452301;
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tmp[1] = 0xefcdab89;
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tmp[2] = 0x98badcfe;
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tmp[3] = 0x10325476;
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for (i = 0; i < POOLWORDS; i += 16)
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MD5Transform(tmp, (char *)(r->pool+i));
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/* Modify pool so next hash will produce different results */
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add_entropy_word(r, tmp[0]);
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add_entropy_word(r, tmp[1]);
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add_entropy_word(r, tmp[2]);
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add_entropy_word(r, tmp[3]);
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/*
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* Run the MD5 Transform one more time, since we want
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* to add at least minimal obscuring of the inputs to
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* add_entropy_word(). --- TYT
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*/
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MD5Transform(tmp, (char *)(r->pool));
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/* Copy data to destination buffer */
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i = MIN(nbytes, 16);
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bcopy(tmp, buf, i);
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nbytes -= i;
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buf += i;
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}
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/* Wipe data from memory */
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bzero(tmp, sizeof(tmp));
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return ret;
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}
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#ifdef notused /* XXX NOT the exported kernel interface */
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/*
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* This function is the exported kernel interface. It returns some
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* number of good random numbers, suitable for seeding TCP sequence
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* numbers, etc.
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*/
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void
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get_random_bytes(void *buf, u_int nbytes)
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{
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extract_entropy(&random_state, (char *) buf, nbytes);
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}
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#endif /* notused */
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u_int
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read_random(void *buf, u_int nbytes)
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{
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if ((nbytes * 8) > random_state.entropy_count)
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nbytes = random_state.entropy_count / 8;
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return extract_entropy(&random_state, (char *)buf, nbytes);
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}
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u_int
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read_random_unlimited(void *buf, u_int nbytes)
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{
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return extract_entropy(&random_state, (char *)buf, nbytes);
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}
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#ifdef notused
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u_int
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write_random(const char *buf, u_int nbytes)
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{
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u_int i;
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u_int32_t word, *p;
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for (i = nbytes, p = (u_int32_t *)buf;
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i >= sizeof(u_int32_t);
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i-= sizeof(u_int32_t), p++)
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add_entropy_word(&random_state, *p);
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if (i) {
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word = 0;
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bcopy(p, &word, i);
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add_entropy_word(&random_state, word);
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}
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return nbytes;
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}
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#endif /* notused */
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int
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random_poll(dev_t dev, int events, struct proc *p)
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{
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int s;
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int revents = 0;
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s = splhigh();
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if (events & (POLLIN | POLLRDNORM)) {
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if (random_state.entropy_count >= 8)
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revents |= events & (POLLIN | POLLRDNORM);
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else
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selrecord(p, &random_state.rsel);
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}
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splx(s);
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if (events & (POLLOUT | POLLWRNORM))
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revents |= events & (POLLOUT | POLLWRNORM); /* heh */
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return (revents);
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}
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