/* $NetBSD: rndpool.c,v 1.4 1997/10/13 20:00:19 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 . 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 #include #include #include #include /* * The random pool "taps" */ #define TAP1 13 #define TAP2 113 #define TAP3 230 #define TAP4 412 static rndpool_t _global_rndpool; 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; } void rndpool_init_global(void) { rndpool_init(&_global_rndpool); } u_int32_t rndpool_get_entropy_count(rp) rndpool_t *rp; { if (rp == NULL) rp = &_global_rndpool; return rp->entropy; } void rndpool_set_entropy_count(rp, entropy) rndpool_t *rp; u_int32_t entropy; { if (rp == NULL) rp = &_global_rndpool; 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; { if (rp == NULL) rp = &_global_rndpool; rp->entropy += entropy; if (rp->entropy > RND_POOLBITS) rp->entropy = RND_POOLBITS; } u_int32_t * rndpool_get_pool(rp) rndpool_t *rp; { if (rp == NULL) rp = &_global_rndpool; 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; { if (rp == NULL) rp = &_global_rndpool; /* * 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)]; 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; { if (rp == NULL) rp = &_global_rndpool; 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; if (rp == NULL) rp = &_global_rndpool; 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; if (rp == NULL) rp = &_global_rndpool; 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); }