source: UsbWattMeter/trunk/lwip-1.4.1/src/netif/ppp/randm.c@ 164

Last change on this file since 164 was 164, checked in by coas-nagasima, 6 years ago

TOPPERS/ECNLサンプルアプリ「USB充電器電力計」を追加

  • Property svn:eol-style set to native
  • Property svn:keywords set to Id
  • Property svn:mime-type set to text/x-csrc
File size: 7.8 KB
Line 
1/*****************************************************************************
2* randm.c - Random number generator program file.
3*
4* Copyright (c) 2003 by Marc Boucher, Services Informatiques (MBSI) inc.
5* Copyright (c) 1998 by Global Election Systems Inc.
6*
7* The authors hereby grant permission to use, copy, modify, distribute,
8* and license this software and its documentation for any purpose, provided
9* that existing copyright notices are retained in all copies and that this
10* notice and the following disclaimer are included verbatim in any
11* distributions. No written agreement, license, or royalty fee is required
12* for any of the authorized uses.
13*
14* THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS *AS IS* AND ANY EXPRESS OR
15* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17* IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
18* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24*
25******************************************************************************
26* REVISION HISTORY
27*
28* 03-01-01 Marc Boucher <marc@mbsi.ca>
29* Ported to lwIP.
30* 98-06-03 Guy Lancaster <lancasterg@acm.org>, Global Election Systems Inc.
31* Extracted from avos.
32*****************************************************************************/
33
34#include "lwip/opt.h"
35
36#if PPP_SUPPORT /* don't build if not configured for use in lwipopts.h */
37
38#include "md5.h"
39#include "randm.h"
40
41#include "ppp_impl.h"
42#include "pppdebug.h"
43
44#include <string.h>
45
46#if MD5_SUPPORT /* this module depends on MD5 */
47#define RANDPOOLSZ 16 /* Bytes stored in the pool of randomness. */
48
49/*****************************/
50/*** LOCAL DATA STRUCTURES ***/
51/*****************************/
52static char randPool[RANDPOOLSZ]; /* Pool of randomness. */
53static long randCount = 0; /* Pseudo-random incrementer */
54
55
56/***********************************/
57/*** PUBLIC FUNCTION DEFINITIONS ***/
58/***********************************/
59/*
60 * Initialize the random number generator.
61 *
62 * Since this is to be called on power up, we don't have much
63 * system randomess to work with. Here all we use is the
64 * real-time clock. We'll accumulate more randomness as soon
65 * as things start happening.
66 */
67void
68avRandomInit()
69{
70 avChurnRand(NULL, 0);
71}
72
73/*
74 * Churn the randomness pool on a random event. Call this early and often
75 * on random and semi-random system events to build randomness in time for
76 * usage. For randomly timed events, pass a null pointer and a zero length
77 * and this will use the system timer and other sources to add randomness.
78 * If new random data is available, pass a pointer to that and it will be
79 * included.
80 *
81 * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
82 */
83void
84avChurnRand(char *randData, u32_t randLen)
85{
86 MD5_CTX md5;
87
88 /* LWIP_DEBUGF(LOG_INFO, ("churnRand: %u@%P\n", randLen, randData)); */
89 MD5Init(&md5);
90 MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
91 if (randData) {
92 MD5Update(&md5, (u_char *)randData, randLen);
93 } else {
94 struct {
95 /* INCLUDE fields for any system sources of randomness */
96 char foobar;
97 } sysData;
98
99 /* Load sysData fields here. */
100 MD5Update(&md5, (u_char *)&sysData, sizeof(sysData));
101 }
102 MD5Final((u_char *)randPool, &md5);
103/* LWIP_DEBUGF(LOG_INFO, ("churnRand: -> 0\n")); */
104}
105
106/*
107 * Use the random pool to generate random data. This degrades to pseudo
108 * random when used faster than randomness is supplied using churnRand().
109 * Note: It's important that there be sufficient randomness in randPool
110 * before this is called for otherwise the range of the result may be
111 * narrow enough to make a search feasible.
112 *
113 * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
114 *
115 * XXX Why does he not just call churnRand() for each block? Probably
116 * so that you don't ever publish the seed which could possibly help
117 * predict future values.
118 * XXX Why don't we preserve md5 between blocks and just update it with
119 * randCount each time? Probably there is a weakness but I wish that
120 * it was documented.
121 */
122void
123avGenRand(char *buf, u32_t bufLen)
124{
125 MD5_CTX md5;
126 u_char tmp[16];
127 u32_t n;
128
129 while (bufLen > 0) {
130 n = LWIP_MIN(bufLen, RANDPOOLSZ);
131 MD5Init(&md5);
132 MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
133 MD5Update(&md5, (u_char *)&randCount, sizeof(randCount));
134 MD5Final(tmp, &md5);
135 randCount++;
136 MEMCPY(buf, tmp, n);
137 buf += n;
138 bufLen -= n;
139 }
140}
141
142/*
143 * Return a new random number.
144 */
145u32_t
146avRandom()
147{
148 u32_t newRand;
149
150 avGenRand((char *)&newRand, sizeof(newRand));
151
152 return newRand;
153}
154
155#else /* MD5_SUPPORT */
156
157/*****************************/
158/*** LOCAL DATA STRUCTURES ***/
159/*****************************/
160static int avRandomized = 0; /* Set when truely randomized. */
161static u32_t avRandomSeed = 0; /* Seed used for random number generation. */
162
163
164/***********************************/
165/*** PUBLIC FUNCTION DEFINITIONS ***/
166/***********************************/
167/*
168 * Initialize the random number generator.
169 *
170 * Here we attempt to compute a random number seed but even if
171 * it isn't random, we'll randomize it later.
172 *
173 * The current method uses the fields from the real time clock,
174 * the idle process counter, the millisecond counter, and the
175 * hardware timer tick counter. When this is invoked
176 * in startup(), then the idle counter and timer values may
177 * repeat after each boot and the real time clock may not be
178 * operational. Thus we call it again on the first random
179 * event.
180 */
181void
182avRandomInit()
183{
184#if 0
185 /* Get a pointer into the last 4 bytes of clockBuf. */
186 u32_t *lptr1 = (u32_t *)((char *)&clockBuf[3]);
187
188 /*
189 * Initialize our seed using the real-time clock, the idle
190 * counter, the millisecond timer, and the hardware timer
191 * tick counter. The real-time clock and the hardware
192 * tick counter are the best sources of randomness but
193 * since the tick counter is only 16 bit (and truncated
194 * at that), the idle counter and millisecond timer
195 * (which may be small values) are added to help
196 * randomize the lower 16 bits of the seed.
197 */
198 readClk();
199 avRandomSeed += *(u32_t *)clockBuf + *lptr1 + OSIdleCtr
200 + ppp_mtime() + ((u32_t)TM1 << 16) + TM1;
201#else
202 avRandomSeed += sys_jiffies(); /* XXX */
203#endif
204
205 /* Initialize the Borland random number generator. */
206 srand((unsigned)avRandomSeed);
207}
208
209/*
210 * Randomize our random seed value. Here we use the fact that
211 * this function is called at *truely random* times by the polling
212 * and network functions. Here we only get 16 bits of new random
213 * value but we use the previous value to randomize the other 16
214 * bits.
215 */
216void
217avRandomize(void)
218{
219 static u32_t last_jiffies;
220
221 if (!avRandomized) {
222 avRandomized = !0;
223 avRandomInit();
224 /* The initialization function also updates the seed. */
225 } else {
226 /* avRandomSeed += (avRandomSeed << 16) + TM1; */
227 avRandomSeed += (sys_jiffies() - last_jiffies); /* XXX */
228 }
229 last_jiffies = sys_jiffies();
230}
231
232/*
233 * Return a new random number.
234 * Here we use the Borland rand() function to supply a pseudo random
235 * number which we make truely random by combining it with our own
236 * seed which is randomized by truely random events.
237 * Thus the numbers will be truely random unless there have been no
238 * operator or network events in which case it will be pseudo random
239 * seeded by the real time clock.
240 */
241u32_t
242avRandom()
243{
244 return ((((u32_t)rand() << 16) + rand()) + avRandomSeed);
245}
246
247#endif /* MD5_SUPPORT */
248
249#endif /* PPP_SUPPORT */
Note: See TracBrowser for help on using the repository browser.