Util: Use secure random number generation

RyanGrieb · Nov 27, 2023 · 1897f0a · 1897f0a
1 parent 3fc140c
commit 1897f0a
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Showing 5 changed files with 29 additions and 11 deletions.
diff --git a/client/index.html b/client/index.html
@@ -1,6 +1,6 @@
 <!DOCTYPE html>
 
-<html>
+<html lang="en" xml:lang="en">
 
 <head>
   <!-- Prevents our "Start" button from flickering when loading the image. 

diff --git a/client/src/scene/SceneBackground.ts b/client/src/scene/SceneBackground.ts
@@ -2,6 +2,7 @@ import { Actor } from "./Actor";
 import { Game } from "../Game";
 import { GameImage } from "../Assets";
 import { SpriteRegion } from "../Assets";
+import { Numbers } from "../util/Numbers";
 
 export class SceneBackground {
   public static generateOcean() {
@@ -44,7 +45,7 @@ export class SceneBackground {
         tileActors.push(
           new Actor({
             image: Game.getInstance().getImage(GameImage.SPRITESHEET),
-            spriteRegion: Math.random() < 0.1 ? SpriteRegion.GRASS_HILL : SpriteRegion.GRASS,
+            spriteRegion: Numbers.safeRandom() < 0.1 ? SpriteRegion.GRASS_HILL : SpriteRegion.GRASS,
             x: xPos,
             y: yPos,
             width: 32,
@@ -55,20 +56,20 @@ export class SceneBackground {
     }
 
     // Sparse background with a random unit
-    //const spriteRegionNum = Math.floor(Math.random() * 9); // Random sprite region b/w 0-2
+    //const spriteRegionNum = Math.floor(Numbers.safeRandom() * 9); // Random sprite region b/w 0-2
     for (let y = -1; y < (Game.getInstance().getHeight() + 24) / 24; y++) {
       for (let x = -1; x < (Game.getInstance().getWidth() + 32) / 32; x++) {
         let yPos = y * 24;
         let xPos = x * 32;
         if (y % 2 != 0) {
           xPos += 16;
         }
-        if (Math.random() > 0.02) continue;
+        if (Numbers.safeRandom() > 0.02) continue;
 
         tileActors.push(
           new Actor({
             image: Game.getInstance().getImage(GameImage.SPRITESHEET),
-            spriteRegion: Object.values(SpriteRegion)[Math.floor(Math.random() * 9)],
+            spriteRegion: Object.values(SpriteRegion)[Math.floor(Numbers.safeRandom() * 9)],
             x: xPos,
             y: yPos,
             width: 32,

diff --git a/client/src/util/Numbers.ts b/client/src/util/Numbers.ts
@@ -14,4 +14,11 @@ export class Numbers {
 
     return sum;
   }
+
+  public static safeRandom() {
+    const crypto = window.crypto;
+    const array = new Uint32Array(1);
+    crypto.getRandomValues(array);
+    return array[0] / (0xffffffff + 1);
+  }
 }
diff --git a/server/src/map/GameMap.ts b/server/src/map/GameMap.ts
@@ -5,6 +5,7 @@ import { MapResources } from "./MapResources";
 import { TileIndexer } from "./TileIndexer";
 import { Unit } from "../unit/Unit";
 import PriorityQueue from "ts-priority-queue";
+import { Numbers } from "../util/Numbers";
 
 enum MapSize {
   DUEL = "48x32",
@@ -182,13 +183,13 @@ export class GameMap {
     //Assign top 10% of tiles to have a 50% of becoming a hill tile
     const totalHills = tallestTiles.length * 0.1;
     for (let i = 0; i < totalHills; i++) {
-      if (Math.random() < 0.5) tallestTiles[i].replaceTileType("grass", "grass_hill");
+      if (Numbers.safeRandom() < 0.5) tallestTiles[i].replaceTileType("grass", "grass_hill");
     }
 
     // TODO: Spawn hills in patches?
     // For all other grass tiles, make it a 13% of becoming a hill tile.
     for (let i = 0; i < tallestTiles.length; i++) {
-      if (Math.random() < 0.13) tallestTiles[i].replaceTileType("grass", "grass_hill");
+      if (Numbers.safeRandom() < 0.13) tallestTiles[i].replaceTileType("grass", "grass_hill");
     }
 
     //Assign the top 5% of tiles to be mountains
@@ -230,7 +231,7 @@ export class GameMap {
         if (yPercent <= 0.1 || yPercent >= 0.9) {
           this.setTileBiome({ tile: currentTile, tileType: "snow" });
         } else if ((yPercent > 0.1 && yPercent < 0.15) || (yPercent > 0.85 && yPercent < 0.9)) {
-          if (Math.random() > 0.25) {
+          if (Numbers.safeRandom() > 0.25) {
             for (const adjTile of currentTile.getAdjacentTiles()) {
               if (!adjTile) continue;
               //FIXME: This can create single ocean/freshwater tiles.
@@ -382,7 +383,7 @@ export class GameMap {
     for (const tile of [...TileIndexer.getTilesByTileType("ocean")]) {
       for (const adjTile of tile.getAdjacentTiles()) {
         if (!adjTile) continue;
-        if (adjTile.containsTileType("shallow_ocean") && Math.random() > 0.75) {
+        if (adjTile.containsTileType("shallow_ocean") && Numbers.safeRandom() > 0.75) {
           tile.replaceTileType("ocean", "shallow_ocean");
         }
       }
@@ -749,7 +750,7 @@ export class GameMap {
 
   private setTilesBiome(tiles: Tile[], tileType: string, setChance: number) {
     for (const tile of tiles) {
-      if (!tile || Math.random() > setChance) continue;
+      if (!tile || Numbers.safeRandom() > setChance) continue;
       this.setTileBiome({ tile: tile, tileType: tileType });
     }
   }
@@ -846,7 +847,7 @@ export class GameMap {
         // Skip if we want to avoid resource tiles
         if (avoidResourceTiles && MapResources.isResourceTile(tile)) continue;
 
-        if (Math.random() <= options.setTileChance) {
+        if (Numbers.safeRandom() <= options.setTileChance) {
           this.setTileBiome({
             tile: tile,
             tileType: options.setTileType,

diff --git a/server/src/util/Numbers.ts b/server/src/util/Numbers.ts
@@ -0,0 +1,9 @@
+import crypto from "crypto";
+
+export class Numbers {
+  public static safeRandom() {
+    const buffer = crypto.randomBytes(4); // 4 bytes for a 32-bit number
+    const randomNum = buffer.readUInt32BE(0) / (0xffffffff + 1);
+    return randomNum;
+  }
+}