--- /dev/null
+/*****************************************************************************
+* 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 "lwip/opt.h"
+
+#if PPP_SUPPORT /* don't build if not configured for use in lwipopts.h */
+
+#include "md5.h"
+#include "randm.h"
+
+#include "ppp.h"
+#include "pppdebug.h"
+
+
+#if MD5_SUPPORT /* this module depends on MD5 */
+#define RANDPOOLSZ 16 /* Bytes stored in the pool of randomness. */
+
+/*****************************/
+/*** LOCAL DATA STRUCTURES ***/
+/*****************************/
+static char randPool[RANDPOOLSZ]; /* Pool of randomness. */
+static long randCount = 0; /* Pseudo-random incrementer */
+
+
+/***********************************/
+/*** PUBLIC FUNCTION DEFINITIONS ***/
+/***********************************/
+/*
+ * Initialize the random number generator.
+ *
+ * Since this is to be called on power up, we don't have much
+ * system randomess to work with. Here all we use is the
+ * real-time clock. We'll accumulate more randomness as soon
+ * as things start happening.
+ */
+void
+avRandomInit()
+{
+ avChurnRand(NULL, 0);
+}
+
+/*
+ * 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
+ */
+void
+avChurnRand(char *randData, u32_t randLen)
+{
+ MD5_CTX md5;
+
+ /* ppp_trace(LOG_INFO, "churnRand: %u@%P\n", randLen, randData); */
+ MD5Init(&md5);
+ MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
+ if (randData) {
+ MD5Update(&md5, (u_char *)randData, randLen);
+ } else {
+ struct {
+ /* INCLUDE fields for any system sources of randomness */
+ char foobar;
+ } sysData;
+
+ /* Load sysData fields here. */
+ MD5Update(&md5, (u_char *)&sysData, sizeof(sysData));
+ }
+ MD5Final((u_char *)randPool, &md5);
+/* ppp_trace(LOG_INFO, "churnRand: -> 0\n"); */
+}
+
+/*
+ * Use the random pool to generate random data. This degrades to pseudo
+ * random when used faster than randomness is supplied using churnRand().
+ * Note: It's important that there be sufficient randomness in 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 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
+ * randCount each time? Probably there is a weakness but I wish that
+ * it was documented.
+ */
+void
+avGenRand(char *buf, u32_t bufLen)
+{
+ MD5_CTX md5;
+ u_char tmp[16];
+ u32_t n;
+
+ while (bufLen > 0) {
+ n = LWIP_MIN(bufLen, RANDPOOLSZ);
+ MD5Init(&md5);
+ MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
+ MD5Update(&md5, (u_char *)&randCount, sizeof(randCount));
+ MD5Final(tmp, &md5);
+ randCount++;
+ MEMCPY(buf, tmp, n);
+ buf += n;
+ bufLen -= n;
+ }
+}
+
+/*
+ * Return a new random number.
+ */
+u32_t
+avRandom()
+{
+ u32_t newRand;
+
+ avGenRand((char *)&newRand, sizeof(newRand));
+
+ return newRand;
+}
+
+#else /* MD5_SUPPORT */
+
+/*****************************/
+/*** LOCAL DATA STRUCTURES ***/
+/*****************************/
+static int avRandomized = 0; /* Set when truely randomized. */
+static u32_t avRandomSeed = 0; /* 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
+avRandomInit()
+{
+#if 0
+ /* Get a pointer into the last 4 bytes of clockBuf. */
+ u32_t *lptr1 = (u32_t *)((char *)&clockBuf[3]);
+
+ /*
+ * Initialize our seed using the real-time clock, the idle
+ * counter, the millisecond timer, and the hardware timer
+ * tick counter. The real-time clock and the hardware
+ * tick counter are the best sources of randomness but
+ * since the tick counter is only 16 bit (and truncated
+ * at that), the idle counter and millisecond timer
+ * (which may be small values) are added to help
+ * randomize the lower 16 bits of the seed.
+ */
+ readClk();
+ avRandomSeed += *(u32_t *)clockBuf + *lptr1 + OSIdleCtr
+ + ppp_mtime() + ((u32_t)TM1 << 16) + TM1;
+#else
+ avRandomSeed += sys_jiffies(); /* XXX */
+#endif
+
+ /* Initialize the Borland random number generator. */
+ srand((unsigned)avRandomSeed);
+}
+
+/*
+ * 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
+avRandomize(void)
+{
+ static u32_t last_jiffies;
+
+ if (!avRandomized) {
+ avRandomized = !0;
+ avRandomInit();
+ /* The initialization function also updates the seed. */
+ } else {
+ /* avRandomSeed += (avRandomSeed << 16) + TM1; */
+ avRandomSeed += (sys_jiffies() - last_jiffies); /* XXX */
+ }
+ last_jiffies = sys_jiffies();
+}
+
+/*
+ * 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
+avRandom()
+{
+ return ((((u32_t)rand() << 16) + rand()) + avRandomSeed);
+}
+
+#endif /* MD5_SUPPORT */
+
+#endif /* PPP_SUPPORT */
