BSD-license-compatible, and NO_STACK build variants
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Joseph Henry
294
ext/lwip/src/netif/ppp/magic.c
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294
ext/lwip/src/netif/ppp/magic.c
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/*
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* magic.c - PPP Magic Number routines.
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*
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* Copyright (c) 1984-2000 Carnegie Mellon University. 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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*
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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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*
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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
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* 3. The name "Carnegie Mellon University" must not be used to
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* endorse or promote products derived from this software without
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* prior written permission. For permission or any legal
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* details, please contact
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* Office of Technology Transfer
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* Carnegie Mellon University
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* 5000 Forbes Avenue
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* Pittsburgh, PA 15213-3890
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* (412) 268-4387, fax: (412) 268-7395
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* tech-transfer@andrew.cmu.edu
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*
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* 4. Redistributions of any form whatsoever must retain the following
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* acknowledgment:
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* "This product includes software developed by Computing Services
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* at Carnegie Mellon University (http://www.cmu.edu/computing/)."
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*
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* CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
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* THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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* AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
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* FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
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* AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
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* OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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/*****************************************************************************
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* randm.c - Random number generator program file.
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*
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* Copyright (c) 2003 by Marc Boucher, Services Informatiques (MBSI) inc.
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* Copyright (c) 1998 by Global Election Systems Inc.
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*
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* The authors hereby grant permission to use, copy, modify, distribute,
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* and license this software and its documentation for any purpose, provided
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* that existing copyright notices are retained in all copies and that this
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* notice and the following disclaimer are included verbatim in any
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* distributions. No written agreement, license, or royalty fee is required
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* for any of the authorized uses.
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*
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* THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS *AS IS* AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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******************************************************************************
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* REVISION HISTORY
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*
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* 03-01-01 Marc Boucher <marc@mbsi.ca>
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* Ported to lwIP.
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* 98-06-03 Guy Lancaster <lancasterg@acm.org>, Global Election Systems Inc.
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* Extracted from avos.
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*****************************************************************************/
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#include "netif/ppp/ppp_opts.h"
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#if PPP_SUPPORT /* don't build if not configured for use in lwipopts.h */
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#include "netif/ppp/ppp_impl.h"
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#include "netif/ppp/magic.h"
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#if PPP_MD5_RANDM /* Using MD5 for better randomness if enabled */
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#include "netif/ppp/pppcrypt.h"
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#define MD5_HASH_SIZE 16
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static char magic_randpool[MD5_HASH_SIZE]; /* Pool of randomness. */
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static long magic_randcount; /* Pseudo-random incrementer */
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static u32_t magic_randomseed; /* Seed used for random number generation. */
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/*
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* Churn the randomness pool on a random event. Call this early and often
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* on random and semi-random system events to build randomness in time for
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* usage. For randomly timed events, pass a null pointer and a zero length
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* and this will use the system timer and other sources to add randomness.
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* If new random data is available, pass a pointer to that and it will be
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* included.
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*
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* Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
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*/
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static void magic_churnrand(char *rand_data, u32_t rand_len) {
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lwip_md5_context md5_ctx;
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/* LWIP_DEBUGF(LOG_INFO, ("magic_churnrand: %u@%P\n", rand_len, rand_data)); */
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lwip_md5_init(&md5_ctx);
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lwip_md5_starts(&md5_ctx);
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lwip_md5_update(&md5_ctx, (u_char *)magic_randpool, sizeof(magic_randpool));
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if (rand_data) {
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lwip_md5_update(&md5_ctx, (u_char *)rand_data, rand_len);
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} else {
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struct {
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/* INCLUDE fields for any system sources of randomness */
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u32_t jiffies;
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#ifdef LWIP_RAND
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u32_t rand;
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#endif /* LWIP_RAND */
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} sys_data;
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magic_randomseed += sys_jiffies();
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sys_data.jiffies = magic_randomseed;
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#ifdef LWIP_RAND
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sys_data.rand = LWIP_RAND();
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#endif /* LWIP_RAND */
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/* Load sys_data fields here. */
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lwip_md5_update(&md5_ctx, (u_char *)&sys_data, sizeof(sys_data));
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}
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lwip_md5_finish(&md5_ctx, (u_char *)magic_randpool);
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lwip_md5_free(&md5_ctx);
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/* LWIP_DEBUGF(LOG_INFO, ("magic_churnrand: -> 0\n")); */
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}
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/*
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* Initialize the random number generator.
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*/
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void magic_init(void) {
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magic_churnrand(NULL, 0);
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}
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/*
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* Randomize our random seed value.
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*/
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void magic_randomize(void) {
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magic_churnrand(NULL, 0);
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}
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/*
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* magic_random_bytes - Fill a buffer with random bytes.
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*
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* Use the random pool to generate random data. This degrades to pseudo
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* random when used faster than randomness is supplied using magic_churnrand().
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* Note: It's important that there be sufficient randomness in magic_randpool
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* before this is called for otherwise the range of the result may be
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* narrow enough to make a search feasible.
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*
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* Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
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*
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* XXX Why does he not just call magic_churnrand() for each block? Probably
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* so that you don't ever publish the seed which could possibly help
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* predict future values.
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* XXX Why don't we preserve md5 between blocks and just update it with
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* magic_randcount each time? Probably there is a weakness but I wish that
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* it was documented.
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*/
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void magic_random_bytes(unsigned char *buf, u32_t buf_len) {
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lwip_md5_context md5_ctx;
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u_char tmp[MD5_HASH_SIZE];
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u32_t n;
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while (buf_len > 0) {
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lwip_md5_init(&md5_ctx);
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lwip_md5_starts(&md5_ctx);
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lwip_md5_update(&md5_ctx, (u_char *)magic_randpool, sizeof(magic_randpool));
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lwip_md5_update(&md5_ctx, (u_char *)&magic_randcount, sizeof(magic_randcount));
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lwip_md5_finish(&md5_ctx, tmp);
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lwip_md5_free(&md5_ctx);
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magic_randcount++;
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n = LWIP_MIN(buf_len, MD5_HASH_SIZE);
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MEMCPY(buf, tmp, n);
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buf += n;
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buf_len -= n;
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}
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}
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/*
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* Return a new random number.
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*/
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u32_t magic(void) {
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u32_t new_rand;
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magic_random_bytes((unsigned char *)&new_rand, sizeof(new_rand));
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return new_rand;
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}
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#else /* PPP_MD5_RANDM */
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/*****************************/
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/*** LOCAL DATA STRUCTURES ***/
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/*****************************/
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#ifndef LWIP_RAND
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static int magic_randomized; /* Set when truely randomized. */
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#endif /* LWIP_RAND */
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static u32_t magic_randomseed; /* Seed used for random number generation. */
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/***********************************/
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/*** PUBLIC FUNCTION DEFINITIONS ***/
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/***********************************/
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/*
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* Initialize the random number generator.
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*
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* Here we attempt to compute a random number seed but even if
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* it isn't random, we'll randomize it later.
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*
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* The current method uses the fields from the real time clock,
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* the idle process counter, the millisecond counter, and the
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* hardware timer tick counter. When this is invoked
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* in startup(), then the idle counter and timer values may
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* repeat after each boot and the real time clock may not be
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* operational. Thus we call it again on the first random
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* event.
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*/
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void magic_init(void) {
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magic_randomseed += sys_jiffies();
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#ifndef LWIP_RAND
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/* Initialize the Borland random number generator. */
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srand((unsigned)magic_randomseed);
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#endif /* LWIP_RAND */
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}
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/*
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* magic_init - Initialize the magic number generator.
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*
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* Randomize our random seed value. Here we use the fact that
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* this function is called at *truely random* times by the polling
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* and network functions. Here we only get 16 bits of new random
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* value but we use the previous value to randomize the other 16
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* bits.
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*/
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void magic_randomize(void) {
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#ifndef LWIP_RAND
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if (!magic_randomized) {
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magic_randomized = !0;
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magic_init();
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/* The initialization function also updates the seed. */
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} else {
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#endif /* LWIP_RAND */
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magic_randomseed += sys_jiffies();
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#ifndef LWIP_RAND
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}
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#endif /* LWIP_RAND */
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}
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/*
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* Return a new random number.
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*
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* Here we use the Borland rand() function to supply a pseudo random
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* number which we make truely random by combining it with our own
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* seed which is randomized by truely random events.
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* Thus the numbers will be truely random unless there have been no
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* operator or network events in which case it will be pseudo random
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* seeded by the real time clock.
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*/
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u32_t magic(void) {
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#ifdef LWIP_RAND
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return LWIP_RAND() + magic_randomseed;
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#else /* LWIP_RAND */
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return ((u32_t)rand() << 16) + (u32_t)rand() + magic_randomseed;
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#endif /* LWIP_RAND */
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}
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/*
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* magic_random_bytes - Fill a buffer with random bytes.
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*/
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void magic_random_bytes(unsigned char *buf, u32_t buf_len) {
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u32_t new_rand, n;
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while (buf_len > 0) {
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new_rand = magic();
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n = LWIP_MIN(buf_len, sizeof(new_rand));
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MEMCPY(buf, &new_rand, n);
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buf += n;
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buf_len -= n;
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}
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}
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#endif /* PPP_MD5_RANDM */
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/*
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* Return a new random number between 0 and (2^pow)-1 included.
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*/
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u32_t magic_pow(u8_t pow) {
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return magic() & ~(~0UL<<pow);
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}
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#endif /* PPP_SUPPORT */
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