NetBSD/sys/dev/rndpool.c

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/* $NetBSD: rndpool.c,v 1.5 1997/10/20 15:03:19 explorer Exp $ */
/*-
* Copyright (c) 1997 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Michael Graff <explorer@flame.org>. This code uses ideas and
* algorithms from the Linux driver written by Ted Ts'o.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the NetBSD
* Foundation, Inc. and its contributors.
* 4. Neither the name of The NetBSD Foundation nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/param.h>
#include <sys/types.h>
#include <sys/systm.h>
#include <sys/md5.h>
#include <sys/rnd.h>
/*
* The random pool "taps"
*/
#define TAP1 99
#define TAP2 59
#define TAP3 31
#define TAP4 9
#define TAP5 7
static inline void rndpool_add_one_word(rndpool_t *, u_int32_t);
void
rndpool_init(rp)
rndpool_t *rp;
{
rp->cursor = RND_POOLWORDS - 1;
rp->entropy = 0;
rp->rotate = 0;
}
u_int32_t
rndpool_get_entropy_count(rp)
rndpool_t *rp;
{
return rp->entropy;
}
void
rndpool_set_entropy_count(rp, entropy)
rndpool_t *rp;
u_int32_t entropy;
{
rp->entropy = entropy;
if (rp->entropy > RND_POOLBITS)
rp->entropy = RND_POOLBITS;
}
void
rndpool_increment_entropy_count(rp, entropy)
rndpool_t *rp;
u_int32_t entropy;
{
rp->entropy += entropy;
if (rp->entropy > RND_POOLBITS)
rp->entropy = RND_POOLBITS;
}
u_int32_t *
rndpool_get_pool(rp)
rndpool_t *rp;
{
return (rp->pool);
}
u_int32_t
rndpool_get_poolsize(void)
{
return (RND_POOLWORDS);
}
/*
* Add one word to the pool, rotating the input as needed.
*/
static inline void
rndpool_add_one_word(rp, val)
rndpool_t *rp;
u_int32_t val;
{
/*
* Steal some values out of the pool, and xor them into the
* word we were given.
*
* Store the new value into the pool using xor. This will
* prevent the actual values from being known to the caller
* since the previous values are assumed to be unknown as well.
*/
val ^= rp->pool[(rp->cursor + TAP1) & (RND_POOLWORDS - 1)];
val ^= rp->pool[(rp->cursor + TAP2) & (RND_POOLWORDS - 1)];
val ^= rp->pool[(rp->cursor + TAP3) & (RND_POOLWORDS - 1)];
val ^= rp->pool[(rp->cursor + TAP4) & (RND_POOLWORDS - 1)];
val ^= rp->pool[(rp->cursor + TAP5) & (RND_POOLWORDS - 1)];
rp->pool[rp->cursor++] ^=
((val << rp->rotate) | (val >> (31 - rp->rotate)));
/*
* If we have looped around the pool, increment the rotate
* variable so the next value will get xored in slightly
* rotated. Increment by a value that is relativly prime to
* the word size to try to spread the bits throughout the pool
* quickly when the pool is empty.
*/
if (rp->cursor == RND_POOLWORDS) {
rp->cursor = 0;
rp->rotate = (rp->rotate + 7) & 31;
}
}
/*
* Add one byte to the pool. Update entropy estimate if an estimate
* was given.
*/
void
rndpool_add_uint32(rp, val, entropy)
rndpool_t *rp;
u_int32_t val;
u_int32_t entropy;
{
val = (val << rp->rotate) | (val >> rp->rotate);
rp->rotate = (rp->rotate + 1) & 0x07;
rndpool_add_one_word(rp, val);
if (entropy) {
rp->entropy += entropy;
if (rp->entropy > RND_POOLBITS)
rp->entropy = RND_POOLBITS;
}
}
/*
* add a buffer's worth of data to the pool.
*/
void
rndpool_add_data(rp, p, len, entropy)
rndpool_t *rp;
void *p;
u_int32_t len;
u_int32_t entropy;
{
u_int32_t val;
u_int8_t *buf;
buf = p;
for (; len > 3 ; len -= 4) {
val = *((u_int32_t *)buf);
rndpool_add_one_word(rp, val);
buf += 4;
}
val = 0;
if (len != 0) {
switch (len) {
case 3:
val = *buf++;
case 2:
val = val << 8 | *buf++;
case 1:
val = val << 8 | *buf++;
}
rndpool_add_one_word(rp, val);
}
if (entropy) {
rp->entropy += entropy;
if (rp->entropy > RND_POOLBITS)
rp->entropy = RND_POOLBITS;
}
}
/*
* Extract some number of bytes from the random pool, decreasing the
* estimate of randomness as each byte is extracted.
*
* Do this by stiring the pool and returning a part of hash as randomness.
* Note that no secrets are given away here since parts of the hash are
* xored together before returned.
*
* Honor the request from the caller to only return good data, any data,
* etc. Note that we must have at least 64 bits of entropy in the pool
* before we return anything in the high-quality modes.
*/
int
rndpool_extract_data(rp, p, len, mode)
rndpool_t *rp;
void *p;
u_int32_t len;
u_int32_t mode;
{
u_int i;
MD5_CTX md5;
u_int32_t digest[4];
u_int32_t remain;
u_int8_t *buf;
int good;
buf = p;
remain = len;
if (mode == RND_EXTRACT_ANY)
good = 1;
else
good = (rp->entropy >= 64); /* size of hash returned */
/*
* While bytes are requested, stir the pool with a hash function and
* copy some of the bytes from that hash out, preserving the secret
* hash value itself.
*/
while (good && (remain != 0)) {
MD5Init(&md5);
MD5Update(&md5, (u_int8_t *)rp->pool, RND_POOLWORDS * 4);
MD5Final((u_int8_t *)digest, &md5);
/*
* Add the hash into the pool. This helps stir the pool a
* bit, and also guarantees that the next hash will generate
* a different value if no new values were added to the
* pool.
*/
for (i = 0 ; i < 4 ; i++)
rndpool_add_one_word(rp, digest[i]);
/*
* copy out the bytes, but xor two bytes from the hash
* together before returning them. This allows us (with
* MD5 as the hash function) to return 8 bytes per hash
* call and not give out any information to the caller.
*/
digest[0] ^= digest[2];
digest[1] ^= digest[3];
if (remain < 8) {
bcopy(digest, buf, remain);
buf += remain;
if (rp->entropy >= remain * 8)
rp->entropy -= remain * 8;
else
rp->entropy = 0;
remain = 0;
} else {
bcopy(digest, buf, 8);
buf += 8;
remain -= 8;
if (rp->entropy >= 64)
rp->entropy -= 64;
else
rp->entropy = 0;
}
if (mode == RND_EXTRACT_GOOD)
good = (rp->entropy >= 64);
}
bzero(&md5, sizeof(MD5_CTX));
bzero(digest, sizeof(digest));
return (len - remain);
}