/* $NetBSD: rndpool.c,v 1.14 2001/11/15 09:48:03 lukem 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 . 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 __KERNEL_RCSID(0, "$NetBSD: rndpool.c,v 1.14 2001/11/15 09:48:03 lukem Exp $"); #include #include #include #include /* * 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(rndpool_t *rp) { rp->cursor = 0; rp->rotate = 0; memset(&rp->stats, 0, sizeof(rp->stats)); rp->stats.curentropy = 0; rp->stats.poolsize = RND_POOLWORDS; rp->stats.threshold = RND_ENTROPY_THRESHOLD; rp->stats.maxentropy = RND_POOLBITS; assert(RND_ENTROPY_THRESHOLD*2 <= 20); /* XXX sha knowledge */ } u_int32_t rndpool_get_entropy_count(rndpool_t *rp) { return (rp->stats.curentropy); } void rndpool_get_stats(rndpool_t *rp, void *rsp, int size) { memcpy(rsp, &rp->stats, size); } void rndpool_increment_entropy_count(rndpool_t *rp, u_int32_t entropy) { rp->stats.curentropy += entropy; rp->stats.added += entropy; if (rp->stats.curentropy > RND_POOLBITS) { rp->stats.discarded += (rp->stats.curentropy - RND_POOLBITS); rp->stats.curentropy = RND_POOLBITS; } } u_int32_t * rndpool_get_pool(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(rndpool_t *rp, u_int32_t val) { /* * Steal some values out of the pool, and xor them into the * word we were given. * * Mix 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)]; if (rp->rotate != 0) val = ((val << rp->rotate) | (val >> (32 - rp->rotate))); rp->pool[rp->cursor++] ^= val; /* * If we have looped around the pool, increment the rotate * variable so the next value will get xored in rotated to * a different position. * 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; } } #if 0 /* * Stir a 32-bit value (with possibly less entropy than that) into the pool. * Update entropy estimate. */ void rndpool_add_uint32(rndpool_t *rp, u_int32_t val, u_int32_t entropy) { rndpool_add_one_word(rp, val); rp->entropy += entropy; rp->stats.added += entropy; if (rp->entropy > RND_POOLBITS) { rp->stats.discarded += (rp->entropy - RND_POOLBITS); rp->entropy = RND_POOLBITS; } } #endif /* * Add a buffer's worth of data to the pool. */ void rndpool_add_data(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; } if (len != 0) { val = 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); } rp->stats.curentropy += entropy; rp->stats.added += entropy; if (rp->stats.curentropy > RND_POOLBITS) { rp->stats.discarded += (rp->stats.curentropy - RND_POOLBITS); rp->stats.curentropy = 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(rndpool_t *rp, void *p, u_int32_t len, u_int32_t mode) { u_int i; SHA1_CTX hash; u_char digest[20]; /* XXX SHA knowledge */ u_int32_t remain, deltae, count; u_int8_t *buf; int good; buf = p; remain = len; if (mode == RND_EXTRACT_ANY) good = 1; else good = (rp->stats.curentropy >= (8 * RND_ENTROPY_THRESHOLD)); assert(RND_ENTROPY_THRESHOLD*2 <= 20); /* XXX SHA knowledge */ while (good && (remain != 0)) { /* * While bytes are requested, compute the hash of the pool, * and then "fold" the hash in half with XOR, keeping the * exact hash value secret, as it will be stirred back into * the pool. * * XXX this approach needs examination by competant * cryptographers! It's rather expensive per bit but * also involves every bit of the pool in the * computation of every output bit.. */ SHA1Init(&hash); SHA1Update(&hash, (u_int8_t *)rp->pool, RND_POOLWORDS * 4); SHA1Final(digest, &hash); /* * Stir the hash back into the pool. This guarantees * that the next hash will generate a different value * if no new values were added to the pool. */ for (i = 0; i < 5; i++) { u_int32_t word; memcpy(&word, &digest[i * 4], 4); rndpool_add_one_word(rp, word); } count = min(remain, RND_ENTROPY_THRESHOLD); for (i = 0; i < count; i++) buf[i] = digest[i] ^ digest[i + RND_ENTROPY_THRESHOLD]; buf += count; deltae = count * 8; remain -= count; deltae = min(deltae, rp->stats.curentropy); rp->stats.removed += deltae; rp->stats.curentropy -= deltae; if (rp->stats.curentropy == 0) rp->stats.generated += (count * 8) - deltae; if (mode == RND_EXTRACT_GOOD) good = (rp->stats.curentropy >= (8 * RND_ENTROPY_THRESHOLD)); } memset(&hash, 0, sizeof(hash)); memset(digest, 0, sizeof(digest)); return (len - remain); }