Fix PRNG seeding to resist guessing

[empserver] / src / util / fairland.c

diff --git a/src/util/fairland.c b/src/util/fairland.c
index 57d79a543efbd344a541864e2215983263e3e340..d95282f2c60e82ee872f093ba680e1dbe47ee670 100644 (file)
--- a/src/util/fairland.c
+++ b/src/util/fairland.c
@@ -29,6 +29,7 @@
  *  Known contributors to this file:
  *     Ken Stevens, 1995
  *     Steve McClure, 1998
+ *     Markus Armbruster, 2004-2012
  */
 
 #include <config.h>
@@ -70,6 +71,7 @@ static int quiet = 0;
 #include <stdarg.h>
 #include <stdio.h>
 #include <unistd.h>
+#include "chance.h"
 #include "file.h"
 #include "optlist.h"
 #include "prototypes.h"
@@ -115,7 +117,6 @@ static char *program_name;
 
 #define new_x(newx) (((newx) + WORLD_X) % WORLD_X)
 #define new_y(newy) (((newy) + WORLD_Y) % WORLD_Y)
-#define rnd(x) (random() % (x))
 
 static int secs;               /* number of sectors grown */
 static int ctot;               /* total number of continents and islands grown */
@@ -178,9 +179,10 @@ main(int argc, char *argv[])
     int opt;
     char *config_file = NULL;
     int i = 0;
+    int seed_set = 0;
 
     program_name = argv[0];
-    rnd_seed = time(NULL);
+    rnd_seed = 0;
 
     while ((opt = getopt(argc, argv, "ae:hioqR:s:v")) != EOF) {
        switch (opt) {
@@ -201,6 +203,7 @@ main(int argc, char *argv[])
            break;
        case 'R':
            rnd_seed = strtoul(optarg, NULL, 10);
+           seed_set = 1;
            break;
        case 's':
            outfile = optarg;
@@ -218,7 +221,9 @@ main(int argc, char *argv[])
     }
     parse_args(argc - optind, argv + optind);
 
-    srandom(rnd_seed);
+    if (!seed_set)
+       rnd_seed = pick_seed();
+    seed_prng(rnd_seed);
     empfile_init();
     if (emp_config(config_file) < 0)
        exit(1);
@@ -558,7 +563,7 @@ fl_move(int j)
 {
     int i, n, newx, newy;
 
-    for (i = rnd(6), n = 0; n < 6; i = (i + 1) % 6, ++n) {
+    for (i = roll0(6), n = 0; n < 6; i = (i + 1) % 6, ++n) {
        newx = new_x(capx[j] + dirx[i]);
        newy = new_y(capy[j] + diry[i]);
        if (iso(j, newx, newy) >= iso(j, capx[j], capy[j])) {
@@ -675,7 +680,7 @@ new_try(int c)
        if (sectc[c][0])
            return 0;
     } else {
-       i = starti = (spike && sectc[c][secs - 1]) ? secs - 1 : rnd(secs);
+       i = starti = (spike && sectc[c][secs - 1]) ? secs - 1 : roll0(secs);
        do {
            if (sectc[c][i])
                return i;
@@ -695,7 +700,7 @@ grow_one_sector(int c)
 {
     int done, coast_search, try1, x, y, newx, newy, i, n, sx, sy;
 
-    spike = rnd(100) < sp;
+    spike = roll0(100) < sp;
     if ((try1 = new_try(c)) == -1)
        return 0;
     x = sx = sectx[c][try1];
@@ -704,7 +709,7 @@ grow_one_sector(int c)
     done = 0;
     do {
        if (spike) {
-           for (i = rnd(6), n = 0; n < 12 && !done; i = (i + 1) % 6, ++n) {
+           for (i = roll0(6), n = 0; n < 12 && !done; i = (i + 1) % 6, ++n) {
                newx = new_x(x + dirx[i]);
                newy = new_y(y + diry[i]);
                if (own[newx][newy] == -1 &&
@@ -715,7 +720,7 @@ grow_one_sector(int c)
                        done = 1;
            }
        } else
-           for (i = rnd(6), n = 0; n < 6 && !done; i = (i + 1) % 6, ++n) {
+           for (i = roll0(6), n = 0; n < 6 && !done; i = (i + 1) % 6, ++n) {
                newx = new_x(x + dirx[i]);
                newy = new_y(y + diry[i]);
                if (own[newx][newy] == -1)
@@ -774,8 +779,8 @@ static int
 place_island(int c, int *xp, int *yp)
 {
     int d, sx, sy;
-    int ssy = rnd(WORLD_Y);
-    int ssx = new_x(rnd(WORLD_X / 2) * 2 + ssy % 2);
+    int ssy = roll0(WORLD_Y);
+    int ssx = new_x(roll0(WORLD_X / 2) * 2 + ssy % 2);
 
     if (ssx > WORLD_X - 2)
        ssx = new_x(ssx + 2);
@@ -809,7 +814,7 @@ grow_islands(void)
        secs = 0;
        if (!place_island(c, &x, &y))
            return;
-       isiz = 1 + rnd(2 * is - 1);
+       isiz = roll(2 * is - 1);
        do {
            ++secs;
            find_coast(c);
@@ -895,7 +900,7 @@ elevate_land(void)
        for (k = nm, mountain_search = 0;
             k && mountain_search < MOUNTAIN_SEARCH_MAX;
             ++mountain_search) {
-           r = rnd(total);
+           r = roll0(total);
            for (i = 0; i < ns; ++i)
                if (r < weight[i] && ELEV == -INFINITY &&
                    (c >= nc ||
@@ -949,10 +954,10 @@ elevate_land(void)
        for (i = 0; i < ns; ++i) {
            if (ELEV == INFINITY) {
                if (dsea[i] == 1)
-                   ELEV = HILLMIN + rnd(PLATMIN - HILLMIN);
+                   ELEV = HILLMIN + roll0(PLATMIN - HILLMIN);
                else
-                   ELEV = HIGHMIN + rnd((256 - HIGHMIN) / 2) +
-                     rnd((256 - HIGHMIN) / 2);
+                   ELEV = HIGHMIN + roll0((256 - HIGHMIN) / 2) +
+                     roll0((256 - HIGHMIN) / 2);
            } else if (c < nc &&
                       (((capx[c] == sectx[c][i] && capy[c] == secty[c][i])) ||
                        ((new_x(capx[c] + 2) == sectx[c][i] &&
@@ -972,7 +977,7 @@ elevate_sea(void)
     for (y = 0; y < WORLD_Y; ++y) {
        for (x = y % 2; x < WORLD_X; x += 2) {
            if (elev[x][y] == -INFINITY)
-               elev[x][y] = -rnd((distance_to_land() * 20 + 27)) - 1;
+               elev[x][y] = -roll(distance_to_land() * 20 + 27);
        }
     }
 }
@@ -999,7 +1004,7 @@ set_oil(int e)
 {
     int oil = 0;
     if (e < LANDMIN)
-       oil = (LANDMIN - e) * 2 + rnd(2);
+       oil = (LANDMIN - e) * 2 + roll0(2);
     else if (e <= OIL_MAX)
        oil = (120 * (OIL_MAX - e + 1)) / (OIL_MAX - LANDMIN + 1);
     if (oil > 100)