Converted to Mersenne Twister for random.

Randomerer! Also: Fixed a security problem. Can you find it?

5 files changed, 125 insertions, 2 deletions

diff --git a/src/common/Makefile b/src/common/Makefile
index b5b8f7c..9218a55 100644
--- a/src/common/Makefile
+++ b/src/common/Makefile
@@ -1,4 +1,4 @@
-txt sql all: core.o socket.o timer.o grfio.o db.o lock.o nullpo.o malloc.o
+txt sql all: core.o socket.o timer.o grfio.o db.o lock.o nullpo.o malloc.o mt_rand.o
 
 core.o: core.c core.h
 socket.o: socket.c socket.h mmo.h
@@ -8,6 +8,7 @@ db.o: db.c db.h
 lock.o: lock.h
 nullpo.o: nullpo.c nullpo.h
 malloc.o: malloc.c malloc.h
+mt_rand.o: mt_rand.c mt_rand.h
 
 clean:
 	rm -f *.o
diff --git a/src/common/core.c b/src/common/core.c
index 7267d8f..94a754b 100644
--- a/src/common/core.c
+++ b/src/common/core.c
@@ -13,6 +13,7 @@
 #include "socket.h"
 #include "timer.h"
 #include "version.h"
+#include "mt_rand.h"
 
 #ifdef MEMWATCH
 #include "memwatch.h"
@@ -133,6 +134,8 @@ int main(int argc,char **argv)
 {
 	int next;
 
+	mt_seed(time(NULL) ^ getpid() ^ getppid());
+
 	Net_Init();
 	do_socket();
 
diff --git a/src/common/mt_rand.c b/src/common/mt_rand.c
new file mode 100644
index 0000000..ab733ae
--- /dev/null
+++ b/src/common/mt_rand.c
@@ -0,0 +1,110 @@
+/*
+// This is the ``Mersenne Twister'' random number generator MT19937, which
+// generates pseudorandom integers uniformly distributed in 0..(2^32 - 1)
+// starting from any odd seed in 0..(2^32 - 1).  This version is a recode
+// by Shawn Cokus (Cokus@math.washington.edu) on March 8, 1998 of a version by
+// Takuji Nishimura (who had suggestions from Topher Cooper and Marc Rieffel in
+// July-August 1997).
+//
+// Effectiveness of the recoding (on Goedel2.math.washington.edu, a DEC Alpha
+// running OSF/1) using GCC -O3 as a compiler: before recoding: 51.6 sec. to
+// generate 300 million random numbers; after recoding: 24.0 sec. for the same
+// (i.e., 46.5% of original time), so speed is now about 12.5 million random
+// number generations per second on this machine.
+//
+// According to the URL <http://www.math.keio.ac.jp/~matumoto/emt.html>
+// (and paraphrasing a bit in places), the Mersenne Twister is ``designed
+// with consideration of the flaws of various existing generators,'' has
+// a period of 2^19937 - 1, gives a sequence that is 623-dimensionally
+// equidistributed, and ``has passed many stringent tests, including the
+// die-hard test of G. Marsaglia and the load test of P. Hellekalek and
+// S. Wegenkittl.''  It is efficient in memory usage (typically using 2506
+// to 5012 bytes of static data, depending on data type sizes, and the code
+// is quite short as well).  It generates random numbers in batches of 624
+// at a time, so the caching and pipelining of modern systems is exploited.
+// It is also divide- and mod-free.
+//
+// This library is free software; you can redistribute it and/or modify it
+// under the terms of the GNU Library General Public License as published by
+// the Free Software Foundation (either version 2 of the License or, at your
+// option, any later version).  This library is distributed in the hope that
+// it will be useful, but WITHOUT ANY WARRANTY, without even the implied
+// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+// the GNU Library General Public License for more details.  You should have
+// received a copy of the GNU Library General Public License along with this
+// library; if not, write to the Free Software Foundation, Inc., 59 Temple
+// Place, Suite 330, Boston, MA 02111-1307, USA.
+//
+// The code as Shawn received it included the following notice:
+//
+//   Copyright (C) 1997 Makoto Matsumoto and Takuji Nishimura.  When
+//   you use this, send an e-mail to <matumoto@math.keio.ac.jp> with
+//   an appropriate reference to your work.
+//
+// It would be nice to CC: <Cokus@math.washington.edu> when you write.
+//
+*/
+
+#include <time.h>
+#include "mt_rand.h"
+
+#define N              (624)                 /* length of state vector */
+#define M              (397)                 /* a period parameter */
+#define K              (0x9908B0DFU)         /* a magic constant */
+#define hiBit(u)       ((u) & 0x80000000U)   /* mask all but highest bit of u */
+#define loBit(u)       ((u) & 0x00000001U)   /* mask all but lowest bit of u */
+#define loBits(u)      ((u) & 0x7FFFFFFFU)   /* mask the highest bit of u */
+#define mixBits(u, v)  (hiBit(u)|loBits(v))  /* move hi bit of u to hi bit of v */
+
+static unsigned long   state[N+1];     /* state vector + 1 extra to not violate ANSI C */
+static unsigned long   *next;          /* next random value is computed from here */
+static int     left = -1;      /* can *next++ this many times before reloading */
+
+
+void mt_seed(unsigned long seed)
+{
+    register unsigned long x = (seed | 1U) & 0xFFFFFFFFU, *s = state;
+    register int    j;
+
+    for(left=0, *s++=x, j=N; --j;
+        *s++ = (x*=69069U) & 0xFFFFFFFFU);
+}
+
+
+unsigned long mt_reload(void)
+{
+    register unsigned long *p0=state, *p2=state+2, *pM=state+M, s0, s1;
+    register int    j;
+
+    if(left < -1)
+        mt_seed(time(NULL));
+
+    left=N-1, next=state+1;
+
+    for(s0=state[0], s1=state[1], j=N-M+1; --j; s0=s1, s1=*p2++)
+        *p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
+
+    for(pM=state, j=M; --j; s0=s1, s1=*p2++)
+        *p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
+
+    s1=state[0], *p0 = *pM ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
+    s1 ^= (s1 >> 11);
+    s1 ^= (s1 <<  7) & 0x9D2C5680U;
+    s1 ^= (s1 << 15) & 0xEFC60000U;
+    return(s1 ^ (s1 >> 18));
+}
+
+
+unsigned long mt_random(void)
+{
+    unsigned long y;
+
+    if(--left < 0)
+        return(mt_reload());
+
+    y  = *next++;
+    y ^= (y >> 11);
+    y ^= (y <<  7) & 0x9D2C5680U;
+    y ^= (y << 15) & 0xEFC60000U;
+    return(y ^ (y >> 18));
+}
diff --git a/src/common/mt_rand.h b/src/common/mt_rand.h
new file mode 100644
index 0000000..07f6ef0
--- /dev/null
+++ b/src/common/mt_rand.h
@@ -0,0 +1,8 @@
+#ifndef __mt_rand_h
+#define __mt_rand_h
+
+void mt_seed(unsigned long seed);
+unsigned long mt_reload(void);
+unsigned long mt_random(void);
+
+#endif /* __mt_rand_h */
diff --git a/src/common/utils.h b/src/common/utils.h
index 794a0b6..ba96da1 100644
--- a/src/common/utils.h
+++ b/src/common/utils.h
@@ -1,3 +1,4 @@
+#include "mt_rand.h"
 
 #ifndef NULL
 #define NULL (void *)0
@@ -38,5 +39,5 @@
  * MRAND(10), returns 0-9.
  * MPRAND(5,10) returns 5-14.
  */
-#define MRAND(mod) (int) ((float)mod * (rand() / (RAND_MAX + 1.0)))
+#define MRAND(mod) (int) ((float)mod * (mt_random() / (RAND_MAX + 1.0)))
 #define MPRAND(add, mod) add + MRAND(mod)