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SeedGenerator
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instance: SeedGenerator
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debug: Debug
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URL_DEV_RANDOM: String
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URL_DEV_URANDOM: String
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static class initializer
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generateSeed(byte[]): void
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getSeedBytes(byte[]): void
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getSystemEntropy(): byte[]
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addNetworkAdapterInfo(MessageDigest): void
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longToByteArray(long): byte[]
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ThreadedSeedGenerator
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URLSeedGenerator
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/*
* Copyright (c) 1996, 2014, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* 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).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
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
* <JAVA_HOME>/lib/security/java.security.
* <JAVA_HOME> 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());
}
}
}
}