text: /*
   * magic.c - PPP Magic Number routines.
   *
   * Copyright (c) 1984-2000 Carnegie Mellon University. All rights reserved.
   *
   * 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. The name "Carnegie Mellon University" must not be used to
   *    endorse or promote products derived from this software without
   *    prior written permission. For permission or any legal
   *    details, please contact
   *      Office of Technology Transfer
   *      Carnegie Mellon University
   *      5000 Forbes Avenue
   *      Pittsburgh, PA  15213-3890
   *      (412) 268-4387, fax: (412) 268-7395
   *      tech-transfer@andrew.cmu.edu
   *
   * 4. Redistributions of any form whatsoever must retain the following
   *    acknowledgment:
   *    "This product includes software developed by Computing Services
   *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
   *
   * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
   * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
   * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
   * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
   * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
   * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  /*****************************************************************************
   * randm.c - Random number generator program file.
   *
   * Copyright (c) 2003 by Marc Boucher, Services Informatiques (MBSI) inc.
   * Copyright (c) 1998 by Global Election Systems Inc.
   *
   * The authors hereby grant permission to use, copy, modify, distribute,
   * and license this software and its documentation for any purpose, provided
   * that existing copyright notices are retained in all copies and that this
   * notice and the following disclaimer are included verbatim in any
   * distributions. No written agreement, license, or royalty fee is required
   * for any of the authorized uses.
   *
   * THIS SOFTWARE IS PROVIDED BY THE 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 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.
   *
   ******************************************************************************
   * REVISION HISTORY
   *
   * 03-01-01 Marc Boucher <marc@mbsi.ca>
   *   Ported to lwIP.
   * 98-06-03 Guy Lancaster <lancasterg@acm.org>, Global Election Systems Inc.
   *   Extracted from avos.
   *****************************************************************************/
  
  #include "interface/LwIp/src/include/lwip/opt.h"
  #if PPP_SUPPORT /* don't build if not configured for use in lwipopts.h */
  
  #include "netif/ppp/ppp_impl.h"
  #include "netif/ppp/magic.h"
  
  #if PPP_MD5_RANDM /* Using MD5 for better randomness if enabled */
  
  #if LWIP_INCLUDED_POLARSSL_MD5
  #include "netif/ppp/polarssl/md5.h"
  #else
  #include "polarssl/md5.h"
  #endif
  
  #define MD5_HASH_SIZE 16
  static char magic_randpool[MD5_HASH_SIZE]; /* Pool of randomness. */
  static long magic_randcount; /* Pseudo-random incrementer */
  static u32_t magic_randomseed; /* Seed used for random number generation. */
  
  /*
   * Churn the randomness pool on a random event.  Call this early and often
   *  on random and semi-random system events to build randomness in time for
   *  usage.  For randomly timed events, pass a null pointer and a zero length
   *  and this will use the system timer and other sources to add randomness.
   *  If new random data is available, pass a pointer to that and it will be
   *  included.
   *
   * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
   */
  static void magic_churnrand(char *rand_data, u32_t rand_len)
  {
  	md5_context md5_ctx;
  
  	/* LWIP_DEBUGF(LOG_INFO, ("magic_churnrand: %u@%P\n", rand_len, rand_data)); */
  	md5_starts(&md5_ctx);
  	md5_update(&md5_ctx, (u_char *)magic_randpool, sizeof(magic_randpool));
  	if (rand_data)
  	{
  		md5_update(&md5_ctx, (u_char *)rand_data, rand_len);
  	}
  	else
  	{
  		struct
  		{
  			/* INCLUDE fields for any system sources of randomness */
  			u32_t jiffies;
  #ifdef LWIP_RAND
  			u32_t rand;
  #endif /* LWIP_RAND */
  		}sys_data;
  		magic_randomseed += sys_jiffies();
  		sys_data.jiffies = magic_randomseed;
  #ifdef LWIP_RAND
  		sys_data.rand = LWIP_RAND();
  #endif /* LWIP_RAND */
  		/* Load sys_data fields here. */
  		md5_update(&md5_ctx, (u_char *)&sys_data, sizeof(sys_data));
  	}
  	md5_finish(&md5_ctx, (u_char *)magic_randpool);
  	/*  LWIP_DEBUGF(LOG_INFO, ("magic_churnrand: -> 0\n")); */
  }
  
  /*
   * Initialize the random number generator.
   */
  void magic_init(void)
  {
  	magic_churnrand(NULL, 0);
  }
  
  /*
   * Randomize our random seed value.
   */
  void magic_randomize(void)
  {
  	magic_churnrand(NULL, 0);
  }
  
  /*
   * magic_random_bytes - Fill a buffer with random bytes.
   *
   * Use the random pool to generate random data.  This degrades to pseudo
   *  random when used faster than randomness is supplied using magic_churnrand().
   * Note: It's important that there be sufficient randomness in magic_randpool
   *  before this is called for otherwise the range of the result may be
   *  narrow enough to make a search feasible.
   *
   * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
   *
   * XXX Why does he not just call magic_churnrand() for each block?  Probably
   *  so that you don't ever publish the seed which could possibly help
   *  predict future values.
   * XXX Why don't we preserve md5 between blocks and just update it with
   *  magic_randcount each time?  Probably there is a weakness but I wish that
   *  it was documented.
   */
  void magic_random_bytes(unsigned char *buf, u32_t buf_len)
  {
  	md5_context md5_ctx;
  	u_char tmp[MD5_HASH_SIZE];
  	u32_t n;
  
  	while (buf_len > 0)
  	{
  		md5_starts(&md5_ctx);
  		md5_update(&md5_ctx, (u_char *)magic_randpool, sizeof(magic_randpool));
  		md5_update(&md5_ctx, (u_char *)&magic_randcount, sizeof(magic_randcount));
  		md5_finish(&md5_ctx, tmp);
  		magic_randcount++;
  		n = LWIP_MIN(buf_len, MD5_HASH_SIZE);
  		MEMCPY(buf, tmp, n);
  		buf += n;
  		buf_len -= n;
  	}
  }
  
  /*
   * Return a new random number.
   */
  u32_t magic(void)
  {
  	u32_t new_rand;
  
  	magic_random_bytes((unsigned char *)&new_rand, sizeof(new_rand));
  
  	return new_rand;
  }
  
  #else /* PPP_MD5_RANDM */
  
  /*****************************/
  /*** LOCAL DATA STRUCTURES ***/
  /*****************************/
  #ifndef LWIP_RAND
  static int magic_randomized; /* Set when truely randomized. */
  #endif /* LWIP_RAND */
  static u32_t magic_randomseed; /* Seed used for random number generation. */
  
  /***********************************/
  /*** PUBLIC FUNCTION DEFINITIONS ***/
  /***********************************/
  
  /*
   * Initialize the random number generator.
   *
   * Here we attempt to compute a random number seed but even if
   * it isn't random, we'll randomize it later.
   *
   * The current method uses the fields from the real time clock,
   * the idle process counter, the millisecond counter, and the
   * hardware timer tick counter.  When this is invoked
   * in startup(), then the idle counter and timer values may
   * repeat after each boot and the real time clock may not be
   * operational.  Thus we call it again on the first random
   * event.
   */
  void magic_init(void)
  {
  	magic_randomseed += sys_jiffies();
  #ifndef LWIP_RAND
  	/* Initialize the Borland random number generator. */
  	srand((unsigned)magic_randomseed);
  #endif /* LWIP_RAND */
  }
  
  /*
   * magic_init - Initialize the magic number generator.
   *
   * Randomize our random seed value.  Here we use the fact that
   * this function is called at *truely random* times by the polling
   * and network functions.  Here we only get 16 bits of new random
   * value but we use the previous value to randomize the other 16
   * bits.
   */
  void magic_randomize(void)
  {
  #ifndef LWIP_RAND
  	if (!magic_randomized)
  	{
  		magic_randomized = !0;
  		magic_init();
  		/* The initialization function also updates the seed. */
  	}
  	else
  	{
  #endif /* LWIP_RAND */
  		magic_randomseed += sys_jiffies();
  #ifndef LWIP_RAND
  	}
  #endif /* LWIP_RAND */
  }
  
  /*
   * Return a new random number.
   *
   * Here we use the Borland rand() function to supply a pseudo random
   * number which we make truely random by combining it with our own
   * seed which is randomized by truely random events.
   * Thus the numbers will be truely random unless there have been no
   * operator or network events in which case it will be pseudo random
   * seeded by the real time clock.
   */
  u32_t magic(void)
  {
  #ifdef LWIP_RAND
  	return LWIP_RAND() + magic_randomseed;
  #else /* LWIP_RAND */
  	return ((u32_t)rand() << 16) + (u32_t)rand() + magic_randomseed;
  #endif /* LWIP_RAND */
  }
  
  /*
   * magic_random_bytes - Fill a buffer with random bytes.
   */
  void magic_random_bytes(unsigned char *buf, u32_t buf_len)
  {
  	u32_t new_rand, n;
  
  	while (buf_len > 0)
  	{
  		new_rand = magic();
  		n = LWIP_MIN(buf_len, sizeof(new_rand));
  		MEMCPY(buf, &new_rand, n);
  		buf += n;
  		buf_len -= n;
  	}
  }
  #endif /* PPP_MD5_RANDM */
  
  /*
   * Return a new random number between 0 and (2^pow)-1 included.
   */
  u32_t magic_pow(u8_t pow)
  {
  	return magic() & ~(~0UL<<pow);
  }
  
  #endif /* PPP_SUPPORT */
  
  