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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * particular file as subject to the "Classpath" exception as provided
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 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
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package sun.security.provider;

/**
 * <P> This class generates seeds for the cryptographically strong random
 * number generator.
 * <P> The seed is produced using one of two techniques, via a computation
 * of current system activity or from an entropy gathering device.
 * <p> In the default technique the seed is  produced by counting the
 * number of times the VM manages to loop in a given period. This number
 * roughly reflects the machine load at that point in time.
 * The samples are translated using a permutation (s-box)
 * and then XORed together. This process is non linear and
 * should prevent the samples from "averaging out". The s-box
 * was designed to have even statistical distribution; it's specific
 * values are not crucial for the security of the seed.
 * We also create a number of sleeper threads which add entropy
 * to the system by keeping the scheduler busy.
 * Twenty such samples should give us roughly 160 bits of randomness.
 * <P> These values are gathered in the background by a daemon thread
 * thus allowing the system to continue performing it's different
 * activites, which in turn add entropy to the random seed.
 * <p> The class also gathers miscellaneous system information, some
 * machine dependent, some not. This information is then hashed together
 * with the 20 seed bytes.
 * <P> The alternative to the above approach is to acquire seed material
 * from an entropy gathering device, such as /dev/random. This can be
 * accomplished by setting the value of the "securerandom.source"
 * security property (in the Java security properties file) to a URL
 * specifying the location of the entropy gathering device.
 * In the event the specified URL cannot be accessed the default
 * mechanism is used.
 * The Java security properties file is located in the file named
 * &lt;JAVA_HOME&gt;/lib/security/java.security.
 * &lt;JAVA_HOME&gt; refers to the value of the java.home system property,
 * and specifies the directory where the JRE is installed.
 *
 * @author Joshua Bloch
 * @author Gadi Guy
 */

import java.security.*;
import java.io.*;
import java.util.Properties;
import java.util.Enumeration;
import java.net.*;
import sun.security.util.Debug;

abstract class SeedGenerator {

    // Static instance is created at link time
    private static SeedGenerator instance;

    private static final Debug debug = Debug.getInstance("provider");

    final static String URL_DEV_RANDOM = SunEntries.URL_DEV_RANDOM;
    final static String URL_DEV_URANDOM = SunEntries.URL_DEV_URANDOM;

    // Static initializer to hook in selected or best performing generator
    static {
        String egdSource = SunEntries.getSeedSource();

        // Try the URL specifying the source
        // e.g. file:/dev/random
        //
        // The URL file:/dev/random or file:/dev/urandom is used to indicate
        // the SeedGenerator using OS support, if available.
        // On Windows, the causes MS CryptoAPI to be used.
        // On Solaris and Linux, this is the identical to using
        // URLSeedGenerator to read from /dev/random

        if (egdSource.equals(URL_DEV_RANDOM) || egdSource.equals(URL_DEV_URANDOM)) {
            try {
                instance = new NativeSeedGenerator();
                if (debug != null) {
                    debug.println("Using operating system seed generator");
                }
            } catch (IOException e) {
                if (debug != null) {
                    debug.println("Failed to use operating system seed "
                                  + "generator: " + e.toString());
                }
            }
        } else if (egdSource.length() != 0) {
            try {
                instance = new URLSeedGenerator(egdSource);
                if (debug != null) {
                    debug.println("Using URL seed generator reading from "
                                  + egdSource);
                }
            } catch (IOException e) {
                if (debug != null)
                    debug.println("Failed to create seed generator with "
                                  + egdSource + ": " + e.toString());
            }
        }

        // Fall back to ThreadedSeedGenerator
        if (instance == null) {
            if (debug != null) {
                debug.println("Using default threaded seed generator");
            }
            instance = new ThreadedSeedGenerator();
        }
    }

    
Fill result with bytes from the queue. Wait for it if it isn't ready.
/** * Fill result with bytes from the queue. Wait for it if it isn't ready. */
static public void generateSeed(byte[] result) { instance.getSeedBytes(result); } abstract void getSeedBytes(byte[] result);
Retrieve some system information, hashed.
/** * Retrieve some system information, hashed. */
static byte[] getSystemEntropy() { byte[] ba; final MessageDigest md; try { md = MessageDigest.getInstance("SHA"); } catch (NoSuchAlgorithmException nsae) { throw new InternalError("internal error: SHA-1 not available."); } // The current time in millis byte b =(byte)System.currentTimeMillis(); md.update(b); java.security.AccessController.doPrivileged (new java.security.PrivilegedAction<Void>() { public Void run() { try { // System properties can change from machine to machine String s; Properties p = System.getProperties(); Enumeration<?> e = p.propertyNames(); while (e.hasMoreElements()) { s =(String)e.nextElement(); md.update(s.getBytes()); md.update(p.getProperty(s).getBytes()); } // Include network adapter names (and a Mac address) addNetworkAdapterInfo(md); // The temporary dir File f = new File(p.getProperty("java.io.tmpdir")); String[] sa = f.list(); for(int i = 0; i < sa.length; i++) md.update(sa[i].getBytes()); } catch (Exception ex) { md.update((byte)ex.hashCode()); } // get Runtime memory stats Runtime rt = Runtime.getRuntime(); byte[] memBytes = longToByteArray(rt.totalMemory()); md.update(memBytes, 0, memBytes.length); memBytes = longToByteArray(rt.freeMemory()); md.update(memBytes, 0, memBytes.length); return null; } }); return md.digest(); } /* * Include network adapter names and, if available, a Mac address * * See also java.util.concurrent.ThreadLocalRandom.initialSeed() */ private static void addNetworkAdapterInfo(MessageDigest md) { try { Enumeration<NetworkInterface> ifcs = NetworkInterface.getNetworkInterfaces(); while (ifcs.hasMoreElements()) { NetworkInterface ifc = ifcs.nextElement(); md.update(ifc.toString().getBytes()); if (!ifc.isVirtual()) { // skip fake addresses byte[] bs = ifc.getHardwareAddress(); if (bs != null) { md.update(bs); break; } } } } catch (Exception ignore) { } }
Helper function to convert a long into a byte array (least significant byte first).
/** * Helper function to convert a long into a byte array (least significant * byte first). */
private static byte[] longToByteArray(long l) { byte[] retVal = new byte[8]; for (int i=0; i<8; i++) { retVal[i] = (byte) l; l >>= 8; } return retVal; } /* // This method helps the test utility receive unprocessed seed bytes. public static int genTestSeed() { return myself.getByte(); } */ private static class ThreadedSeedGenerator extends SeedGenerator implements Runnable { // Queue is used to collect seed bytes private byte[] pool; private int start, end, count; // Thread group for our threads ThreadGroup seedGroup;
The constructor is only called once to construct the one instance we actually use. It instantiates the message digest and starts the thread going.
/** * The constructor is only called once to construct the one * instance we actually use. It instantiates the message digest * and starts the thread going. */
ThreadedSeedGenerator() { pool = new byte[20]; start = end = 0; MessageDigest digest; try { digest = MessageDigest.getInstance("SHA"); } catch (NoSuchAlgorithmException e) { throw new InternalError("internal error: SHA-1 not available."); } final ThreadGroup[] finalsg = new ThreadGroup[1]; Thread t = java.security.AccessController.doPrivileged (new java.security.PrivilegedAction<Thread>() { public Thread run() { ThreadGroup parent, group = Thread.currentThread().getThreadGroup(); while ((parent = group.getParent()) != null) group = parent; finalsg[0] = new ThreadGroup (group, "SeedGenerator ThreadGroup"); Thread newT = new Thread(finalsg[0], ThreadedSeedGenerator.this, "SeedGenerator Thread"); newT.setPriority(Thread.MIN_PRIORITY); newT.setDaemon(true); return newT; } }); seedGroup = finalsg[0]; t.start(); }
This method does the actual work. It collects random bytes and pushes them into the queue.
/** * This method does the actual work. It collects random bytes and * pushes them into the queue. */
final public void run() { try { while (true) { // Queue full? Wait till there's room. synchronized(this) { while (count >= pool.length) wait(); } int counter, quanta; byte v = 0; // Spin count must not be under 64000 for (counter = quanta = 0; (counter < 64000) && (quanta < 6); quanta++) { // Start some noisy threads try { BogusThread bt = new BogusThread(); Thread t = new Thread (seedGroup, bt, "SeedGenerator Thread"); t.start(); } catch (Exception e) { throw new InternalError("internal error: " + "SeedGenerator thread creation error."); } // We wait 250milli quanta, so the minimum wait time // cannot be under 250milli. int latch = 0; latch = 0; long l = System.currentTimeMillis() + 250; while (System.currentTimeMillis() < l) { synchronized(this){}; latch++; } // Translate the value using the permutation, and xor // it with previous values gathered. v ^= rndTab[latch % 255]; counter += latch; } // Push it into the queue and notify anybody who might // be waiting for it. synchronized(this) { pool[end] = v; end++; count++; if (end >= pool.length) end = 0; notifyAll(); } } } catch (Exception e) { throw new InternalError("internal error: " + "SeedGenerator thread generated an exception."); } } @Override void getSeedBytes(byte[] result) { for (int i = 0; i < result.length; i++) { result[i] = getSeedByte(); } } byte getSeedByte() { byte b = 0; try { // Wait for it... synchronized(this) { while (count <= 0) wait(); } } catch (Exception e) { if (count <= 0) throw new InternalError("internal error: " + "SeedGenerator thread generated an exception."); } synchronized(this) { // Get it from the queue b = pool[start]; pool[start] = 0; start++; count--; if (start == pool.length) start = 0; // Notify the daemon thread, just in case it is // waiting for us to make room in the queue. notifyAll(); } return b; } // The permutation was calculated by generating 64k of random // data and using it to mix the trivial permutation. // It should be evenly distributed. The specific values // are not crucial to the security of this class. private static byte[] rndTab = { 56, 30, -107, -6, -86, 25, -83, 75, -12, -64, 5, -128, 78, 21, 16, 32, 70, -81, 37, -51, -43, -46, -108, 87, 29, 17, -55, 22, -11, -111, -115, 84, -100, 108, -45, -15, -98, 72, -33, -28, 31, -52, -37, -117, -97, -27, 93, -123, 47, 126, -80, -62, -93, -79, 61, -96, -65, -5, -47, -119, 14, 89, 81, -118, -88, 20, 67, -126, -113, 60, -102, 55, 110, 28, 85, 121, 122, -58, 2, 45, 43, 24, -9, 103, -13, 102, -68, -54, -101, -104, 19, 13, -39, -26, -103, 62, 77, 51, 44, 111, 73, 18, -127, -82, 4, -30, 11, -99, -74, 40, -89, 42, -76, -77, -94, -35, -69, 35, 120, 76, 33, -73, -7, 82, -25, -10, 88, 125, -112, 58, 83, 95, 6, 10, 98, -34, 80, 15, -91, 86, -19, 52, -17, 117, 49, -63, 118, -90, 36, -116, -40, -71, 97, -53, -109, -85, 109, -16, -3, 104, -95, 68, 54, 34, 26, 114, -1, 106, -121, 3, 66, 0, 100, -84, 57, 107, 119, -42, 112, -61, 1, 48, 38, 12, -56, -57, 39, -106, -72, 41, 7, 71, -29, -59, -8, -38, 79, -31, 124, -124, 8, 91, 116, 99, -4, 9, -36, -78, 63, -49, -67, -87, 59, 101, -32, 92, 94, 53, -41, 115, -66, -70, -122, 50, -50, -22, -20, -18, -21, 23, -2, -48, 96, 65, -105, 123, -14, -110, 69, -24, -120, -75, 74, 127, -60, 113, 90, -114, 105, 46, 27, -125, -23, -44, 64 };
This inner thread causes the thread scheduler to become 'noisy', thus adding entropy to the system load. At least one instance of this class is generated for every seed byte.
/** * This inner thread causes the thread scheduler to become 'noisy', * thus adding entropy to the system load. * At least one instance of this class is generated for every seed byte. */
private static class BogusThread implements Runnable { final public void run() { try { for(int i = 0; i < 5; i++) Thread.sleep(50); // System.gc(); } catch (Exception e) { } } } } static class URLSeedGenerator extends SeedGenerator { private String deviceName; private InputStream devRandom;
The constructor is only called once to construct the one instance we actually use. It opens the entropy gathering device which will supply the randomness.
/** * The constructor is only called once to construct the one * instance we actually use. It opens the entropy gathering device * which will supply the randomness. */
URLSeedGenerator(String egdurl) throws IOException { if (egdurl == null) { throw new IOException("No random source specified"); } deviceName = egdurl; init(); } URLSeedGenerator() throws IOException { this(SeedGenerator.URL_DEV_RANDOM); } private void init() throws IOException { final URL device = new URL(deviceName); try { devRandom = java.security.AccessController.doPrivileged (new java.security.PrivilegedExceptionAction<InputStream>() { public InputStream run() throws IOException { /* * return a FileInputStream for file URLs and * avoid buffering. The openStream() call wraps * InputStream in a BufferedInputStream which * can buffer up to 8K bytes. This read is a * performance issue for entropy sources which * can be slow to replenish. */ if (device.getProtocol().equalsIgnoreCase("file")) { File deviceFile = getDeviceFile(device); return new FileInputStream(deviceFile); } else { return device.openStream(); } } }); } catch (Exception e) { throw new IOException("Failed to open " + deviceName, e.getCause()); } } /* * Use a URI to access this File. Previous code used a URL * which is less strict on syntax. If we encounter a * URISyntaxException we make best efforts for backwards * compatibility. e.g. space character in deviceName string. * * Method called within PrivilegedExceptionAction block. */ private File getDeviceFile(URL device) throws IOException { try { URI deviceURI = device.toURI(); if(deviceURI.isOpaque()) { // File constructor does not accept opaque URI URI localDir = new File(System.getProperty("user.dir")).toURI(); String uriPath = localDir.toString() + deviceURI.toString().substring(5); return new File(URI.create(uriPath)); } else { return new File(deviceURI); } } catch (URISyntaxException use) { /* * Make best effort to access this File. * We can try using the URL path. */ return new File(device.getPath()); } } @Override void getSeedBytes(byte[] result) { int len = result.length; int read = 0; try { while (read < len) { int count = devRandom.read(result, read, len - read); // /dev/random blocks - should never have EOF if (count < 0) throw new InternalError("URLSeedGenerator " + deviceName + " reached end of file"); read += count; } } catch (IOException ioe) { throw new InternalError("URLSeedGenerator " + deviceName + " generated exception: " + ioe.getMessage()); } } } }