Merge branch 'fix-sdk-use-secure-random' into 'master'

[Random] Provide initialized secure random instead of seed

See merge request codingame/game-engine!310

Author: CodinGameCommunity

engine/core/src/main/java/com/codingame/gameengine/core/MultiplayerGameManager.java

@@ -2,8 +2,11 @@
 
 import java.io.IOException;
 import java.io.StringReader;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
 import java.util.List;
 import java.util.Properties;
+import java.util.Random;
 import java.util.Scanner;
 import java.util.Map.Entry;
 import java.util.concurrent.ThreadLocalRandom;
@@ -21,8 +24,11 @@
 @Singleton
 public final class MultiplayerGameManager<T extends AbstractMultiplayerPlayer> extends GameManager<T> {
 
+    private static final String RANDOM_SECURE_SHA1PRNG_ALGORITHM = "SHA1PRNG";
+
     private Properties gameParameters;
     private long seed;
+    private Random random;
 
     @Override
     protected void readGameProperties(InputCommand iCmd, Scanner s) {
@@ -46,6 +52,15 @@ protected void readGameProperties(InputCommand iCmd, Scanner s) {
             }
         }
         gameParameters.setProperty("seed", String.valueOf(seed));
+
+		try {
+			// This random generator is reproducible whereas default one (native PRNG is not)
+			random = SecureRandom.getInstance(RANDOM_SECURE_SHA1PRNG_ALGORITHM);
+			random.setSeed(seed);
+		} catch (NoSuchAlgorithmException e1) {
+			log.error("Error while creating secure random number generator. Default to non-secure random generator", e1);
+			random = new Random(seed);
+		}
     }
 
     @Override
@@ -70,15 +85,29 @@ public int getPlayerCount() {
 
     /**
      * <p>
-     * The seed is used to generated parameters such as width and height.<br>
-     * If a seed is present in the given input, the input value should override the generated values.
+     * The seed is used to initialize the Random number generator.<br>
+     * If a seed is present in the given input, the input value should override the generated values.<br>
+     * 
+     * The seed should NOT be used directly in referee but through the random number generator provided by @method getRandom
      * </p>
      * 
      * @return an <code>long</code> containing a given or generated seed.
      */
     public long getSeed() {
         return seed;
     }
+    
+    /**
+     * <p>
+     * The random generator is used to generated parameters such as width and height.<br>
+     * The provided random generator is a SecureRandom using the SHAPRNG algorithm.<br>
+     * </p>
+     * 
+     * @return an <code>Random</code> containing a given or generated seed.
+     */
+    public Random getRandom() {
+        return random;
+    }
 
     /**
      * <p>

playground/misc/misc-3-release-notes.md

@@ -8,6 +8,7 @@ The CodinGame SDK is regularly updated and improved. This document lets you know
 
 - Updated links to pixi docs
 - Updated log4j dependency
+- Use secure random
 
 ## 4.1.6