1 files changed, 83 insertions, 0 deletions
diff --git a/src/main/java/com/gitblit/utils/SecureRandom.java b/src/main/java/com/gitblit/utils/SecureRandom.java
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+++ b/src/main/java/com/gitblit/utils/SecureRandom.java
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+/*
+ * Copyright 2016 gitblit.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.gitblit.utils;
+
+/**
+ * Wrapper class for java.security.SecureRandom, which will periodically reseed
+ * the PRNG in case an instance of the class has been running for a long time.
+ *
+ * @author Florian Zschocke
+ */
+public class SecureRandom {
+
+	/** Period (in ms) after which a new SecureRandom will be created in order to get a fresh random seed. */
+	private static final long RESEED_PERIOD = 24 * 60 * 60 * 1000; /* 24 hours */
+
+
+	private long last;
+	private java.security.SecureRandom random;
+
+
+
+	public SecureRandom() {
+		// Make sure the SecureRandom is seeded right from the start.
+		// This also lets any blocks during seeding occur at creation
+		// and prevents it from happening when getting next random bytes.
+		seed();
+	}
+
+
+
+	public byte[] randomBytes(int num) {
+		byte[] bytes = new byte[num];
+		nextBytes(bytes);
+		return bytes;
+	}
+
+
+	public void nextBytes(byte[] bytes) {
+		random.nextBytes(bytes);
+		reseed(false);
+	}
+
+
+	void reseed(boolean forced) {
+		long ts = System.currentTimeMillis();
+		if (forced || (ts - last) > RESEED_PERIOD) {
+			last = ts;
+			runReseed();
+		}
+	}
+
+
+
+	private void seed() {
+		random = new java.security.SecureRandom();
+		random.nextBytes(new byte[0]);
+		last = System.currentTimeMillis();
+	}
+
+
+	private void runReseed() {
+		// Have some other thread hit the penalty potentially incurred by reseeding,
+		// so that we can immediately return and not block the operation in progress.
+		new Thread() {
+			public void run() {
+				seed();
+			}
+		}.start();
+	}
+}