329 lines
7.8 KiB
C
329 lines
7.8 KiB
C
/* $NetBSD: rndpool.c,v 1.4 1997/10/13 20:00:19 explorer Exp $ */
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/*-
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* Copyright (c) 1997 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Michael Graff <explorer@flame.org>. This code uses ideas and
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* algorithms from the Linux driver written by Ted Ts'o.
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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, this list of conditions and the following disclaimer.
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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. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, 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 OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/param.h>
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#include <sys/types.h>
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#include <sys/systm.h>
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#include <sys/md5.h>
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#include <sys/rnd.h>
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/*
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* The random pool "taps"
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*/
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#define TAP1 13
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#define TAP2 113
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#define TAP3 230
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#define TAP4 412
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static rndpool_t _global_rndpool;
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static inline void rndpool_add_one_word(rndpool_t *, u_int32_t);
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void
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rndpool_init(rp)
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rndpool_t *rp;
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{
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rp->cursor = RND_POOLWORDS - 1;
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rp->entropy = 0;
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rp->rotate = 0;
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}
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void
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rndpool_init_global(void)
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{
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rndpool_init(&_global_rndpool);
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}
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u_int32_t
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rndpool_get_entropy_count(rp)
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rndpool_t *rp;
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{
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if (rp == NULL)
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rp = &_global_rndpool;
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return rp->entropy;
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}
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void
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rndpool_set_entropy_count(rp, entropy)
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rndpool_t *rp;
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u_int32_t entropy;
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{
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if (rp == NULL)
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rp = &_global_rndpool;
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rp->entropy = entropy;
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if (rp->entropy > RND_POOLBITS)
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rp->entropy = RND_POOLBITS;
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}
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void
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rndpool_increment_entropy_count(rp, entropy)
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rndpool_t *rp;
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u_int32_t entropy;
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{
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if (rp == NULL)
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rp = &_global_rndpool;
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rp->entropy += entropy;
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if (rp->entropy > RND_POOLBITS)
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rp->entropy = RND_POOLBITS;
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}
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u_int32_t *
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rndpool_get_pool(rp)
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rndpool_t *rp;
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{
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if (rp == NULL)
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rp = &_global_rndpool;
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return (rp->pool);
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}
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u_int32_t
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rndpool_get_poolsize(void)
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{
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return (RND_POOLWORDS);
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}
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/*
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* Add one word to the pool, rotating the input as needed.
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*/
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static inline void
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rndpool_add_one_word(rp, val)
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rndpool_t *rp;
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u_int32_t val;
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{
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if (rp == NULL)
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rp = &_global_rndpool;
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/*
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* Steal some values out of the pool, and xor them into the
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* word we were given.
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*
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* Store the new value into the pool using xor. This will
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* prevent the actual values from being known to the caller
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* since the previous values are assumed to be unknown as well.
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*/
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val ^= rp->pool[(rp->cursor + TAP1) & (RND_POOLWORDS - 1)];
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val ^= rp->pool[(rp->cursor + TAP2) & (RND_POOLWORDS - 1)];
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val ^= rp->pool[(rp->cursor + TAP3) & (RND_POOLWORDS - 1)];
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val ^= rp->pool[(rp->cursor + TAP4) & (RND_POOLWORDS - 1)];
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rp->pool[rp->cursor++] ^=
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((val << rp->rotate) | (val >> (31 - rp->rotate)));
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/*
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* If we have looped around the pool, increment the rotate
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* variable so the next value will get xored in slightly
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* rotated. Increment by a value that is relativly prime to
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* the word size to try to spread the bits throughout the pool
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* quickly when the pool is empty.
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*/
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if (rp->cursor == RND_POOLWORDS) {
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rp->cursor = 0;
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rp->rotate = (rp->rotate + 7) & 31;
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}
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}
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/*
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* Add one byte to the pool. Update entropy estimate if an estimate
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* was given.
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*/
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void
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rndpool_add_uint32(rp, val, entropy)
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rndpool_t *rp;
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u_int32_t val;
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u_int32_t entropy;
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{
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if (rp == NULL)
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rp = &_global_rndpool;
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val = (val << rp->rotate) | (val >> rp->rotate);
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rp->rotate = (rp->rotate + 1) & 0x07;
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rndpool_add_one_word(rp, val);
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if (entropy) {
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rp->entropy += entropy;
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if (rp->entropy > RND_POOLBITS)
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rp->entropy = RND_POOLBITS;
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}
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}
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/*
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* add a buffer's worth of data to the pool.
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*/
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void
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rndpool_add_data(rp, p, len, entropy)
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rndpool_t *rp;
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void *p;
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u_int32_t len;
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u_int32_t entropy;
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{
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u_int32_t val;
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u_int8_t *buf;
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if (rp == NULL)
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rp = &_global_rndpool;
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buf = p;
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for (; len > 3 ; len -= 4) {
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val = *((u_int32_t *)buf);
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rndpool_add_one_word(rp, val);
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buf += 4;
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}
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val = 0;
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if (len != 0) {
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switch (len) {
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case 3:
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val = *buf++;
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case 2:
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val = val << 8 | *buf++;
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case 1:
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val = val << 8 | *buf++;
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}
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rndpool_add_one_word(rp, val);
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}
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if (entropy) {
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rp->entropy += entropy;
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if (rp->entropy > RND_POOLBITS)
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rp->entropy = RND_POOLBITS;
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}
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}
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/*
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* Extract some number of bytes from the random pool, decreasing the
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* estimate of randomness as each byte is extracted.
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*
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* Do this by stiring the pool and returning a part of hash as randomness.
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* Note that no secrets are given away here since parts of the hash are
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* xored together before returned.
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*
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* Honor the request from the caller to only return good data, any data,
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* etc. Note that we must have at least 64 bits of entropy in the pool
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* before we return anything in the high-quality modes.
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*/
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int
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rndpool_extract_data(rp, p, len, mode)
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rndpool_t *rp;
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void *p;
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u_int32_t len;
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u_int32_t mode;
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{
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u_int i;
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MD5_CTX md5;
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u_int32_t digest[4];
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u_int32_t remain;
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u_int8_t *buf;
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int good;
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if (rp == NULL)
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rp = &_global_rndpool;
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buf = p;
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remain = len;
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if (mode == RND_EXTRACT_ANY)
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good = 1;
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else
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good = (rp->entropy >= 64); /* size of hash returned */
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/*
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* While bytes are requested, stir the pool with a hash function and
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* copy some of the bytes from that hash out, preserving the secret
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* hash value itself.
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*/
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while (good && (remain != 0)) {
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MD5Init(&md5);
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MD5Update(&md5, (u_int8_t *)rp->pool, RND_POOLWORDS * 4);
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MD5Final((u_int8_t *)digest, &md5);
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/*
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* Add the hash into the pool. This helps stir the pool a
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* bit, and also guarantees that the next hash will generate
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* a different value if no new values were added to the
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* pool.
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*/
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for (i = 0 ; i < 4 ; i++)
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rndpool_add_one_word(rp, digest[i]);
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/*
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* copy out the bytes, but xor two bytes from the hash
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* together before returning them. This allows us (with
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* MD5 as the hash function) to return 8 bytes per hash
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* call and not give out any information to the caller.
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*/
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digest[0] ^= digest[2];
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digest[1] ^= digest[3];
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if (remain < 8) {
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bcopy(digest, buf, remain);
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buf += remain;
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if (rp->entropy >= remain * 8)
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rp->entropy -= remain * 8;
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else
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rp->entropy = 0;
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remain = 0;
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} else {
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bcopy(digest, buf, 8);
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buf += 8;
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remain -= 8;
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if (rp->entropy >= 64)
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rp->entropy -= 64;
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else
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rp->entropy = 0;
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}
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if (mode == RND_EXTRACT_GOOD)
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good = (rp->entropy >= 64);
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}
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bzero(&md5, sizeof(MD5_CTX));
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bzero(digest, sizeof(digest));
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return (len - remain);
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}
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