PRNG fixes were a nop ever since we switched to 4.4+
This commit is contained in:
Daniel Gultsch
parent
521bb7846c
commit
f23311ab3f
|
|
@ -1,327 +0,0 @@
|
|||
package eu.siacs.conversations.utils;
|
||||
|
||||
import android.os.Build;
|
||||
import android.os.Process;
|
||||
import android.util.Log;
|
||||
|
||||
import java.io.ByteArrayOutputStream;
|
||||
import java.io.DataInputStream;
|
||||
import java.io.DataOutputStream;
|
||||
import java.io.File;
|
||||
import java.io.FileInputStream;
|
||||
import java.io.FileOutputStream;
|
||||
import java.io.IOException;
|
||||
import java.io.OutputStream;
|
||||
import java.io.UnsupportedEncodingException;
|
||||
import java.security.NoSuchAlgorithmException;
|
||||
import java.security.Provider;
|
||||
import java.security.SecureRandom;
|
||||
import java.security.SecureRandomSpi;
|
||||
import java.security.Security;
|
||||
|
||||
/**
|
||||
* Fixes for the output of the default PRNG having low entropy.
|
||||
*
|
||||
* The fixes need to be applied via {@link #apply()} before any use of Java
|
||||
* Cryptography Architecture primitives. A good place to invoke them is in the
|
||||
* application's {@code onCreate}.
|
||||
*/
|
||||
public final class PRNGFixes {
|
||||
|
||||
private static final int VERSION_CODE_JELLY_BEAN = 16;
|
||||
private static final int VERSION_CODE_JELLY_BEAN_MR2 = 18;
|
||||
private static final byte[] BUILD_FINGERPRINT_AND_DEVICE_SERIAL = getBuildFingerprintAndDeviceSerial();
|
||||
|
||||
/** Hidden constructor to prevent instantiation. */
|
||||
private PRNGFixes() {
|
||||
}
|
||||
|
||||
/**
|
||||
* Applies all fixes.
|
||||
*
|
||||
* @throws SecurityException
|
||||
* if a fix is needed but could not be applied.
|
||||
*/
|
||||
public static void apply() {
|
||||
applyOpenSSLFix();
|
||||
installLinuxPRNGSecureRandom();
|
||||
}
|
||||
|
||||
/**
|
||||
* Applies the fix for OpenSSL PRNG having low entropy. Does nothing if the
|
||||
* fix is not needed.
|
||||
*
|
||||
* @throws SecurityException
|
||||
* if the fix is needed but could not be applied.
|
||||
*/
|
||||
private static void applyOpenSSLFix() throws SecurityException {
|
||||
if ((Build.VERSION.SDK_INT < VERSION_CODE_JELLY_BEAN)
|
||||
|| (Build.VERSION.SDK_INT > VERSION_CODE_JELLY_BEAN_MR2)) {
|
||||
// No need to apply the fix
|
||||
return;
|
||||
}
|
||||
|
||||
try {
|
||||
// Mix in the device- and invocation-specific seed.
|
||||
Class.forName("org.apache.harmony.xnet.provider.jsse.NativeCrypto")
|
||||
.getMethod("RAND_seed", byte[].class)
|
||||
.invoke(null, generateSeed());
|
||||
|
||||
// Mix output of Linux PRNG into OpenSSL's PRNG
|
||||
int bytesRead = (Integer) Class
|
||||
.forName(
|
||||
"org.apache.harmony.xnet.provider.jsse.NativeCrypto")
|
||||
.getMethod("RAND_load_file", String.class, long.class)
|
||||
.invoke(null, "/dev/urandom", 1024);
|
||||
if (bytesRead != 1024) {
|
||||
throw new IOException(
|
||||
"Unexpected number of bytes read from Linux PRNG: "
|
||||
+ bytesRead);
|
||||
}
|
||||
} catch (Exception e) {
|
||||
throw new SecurityException("Failed to seed OpenSSL PRNG", e);
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Installs a Linux PRNG-backed {@code SecureRandom} implementation as the
|
||||
* default. Does nothing if the implementation is already the default or if
|
||||
* there is not need to install the implementation.
|
||||
*
|
||||
* @throws SecurityException
|
||||
* if the fix is needed but could not be applied.
|
||||
*/
|
||||
private static void installLinuxPRNGSecureRandom() throws SecurityException {
|
||||
if (Build.VERSION.SDK_INT > VERSION_CODE_JELLY_BEAN_MR2) {
|
||||
// No need to apply the fix
|
||||
return;
|
||||
}
|
||||
|
||||
// Install a Linux PRNG-based SecureRandom implementation as the
|
||||
// default, if not yet installed.
|
||||
Provider[] secureRandomProviders = Security
|
||||
.getProviders("SecureRandom.SHA1PRNG");
|
||||
if ((secureRandomProviders == null)
|
||||
|| (secureRandomProviders.length < 1)
|
||||
|| (!LinuxPRNGSecureRandomProvider.class
|
||||
.equals(secureRandomProviders[0].getClass()))) {
|
||||
Security.insertProviderAt(new LinuxPRNGSecureRandomProvider(), 1);
|
||||
}
|
||||
|
||||
// Assert that new SecureRandom() and
|
||||
// SecureRandom.getInstance("SHA1PRNG") return a SecureRandom backed
|
||||
// by the Linux PRNG-based SecureRandom implementation.
|
||||
SecureRandom rng1 = new SecureRandom();
|
||||
if (!LinuxPRNGSecureRandomProvider.class.equals(rng1.getProvider()
|
||||
.getClass())) {
|
||||
throw new SecurityException(
|
||||
"new SecureRandom() backed by wrong Provider: "
|
||||
+ rng1.getProvider().getClass());
|
||||
}
|
||||
|
||||
SecureRandom rng2;
|
||||
try {
|
||||
rng2 = SecureRandom.getInstance("SHA1PRNG");
|
||||
} catch (NoSuchAlgorithmException e) {
|
||||
throw new SecurityException("SHA1PRNG not available", e);
|
||||
}
|
||||
if (!LinuxPRNGSecureRandomProvider.class.equals(rng2.getProvider()
|
||||
.getClass())) {
|
||||
throw new SecurityException(
|
||||
"SecureRandom.getInstance(\"SHA1PRNG\") backed by wrong"
|
||||
+ " Provider: " + rng2.getProvider().getClass());
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* {@code Provider} of {@code SecureRandom} engines which pass through all
|
||||
* requests to the Linux PRNG.
|
||||
*/
|
||||
private static class LinuxPRNGSecureRandomProvider extends Provider {
|
||||
|
||||
public LinuxPRNGSecureRandomProvider() {
|
||||
super("LinuxPRNG", 1.0,
|
||||
"A Linux-specific random number provider that uses"
|
||||
+ " /dev/urandom");
|
||||
// Although /dev/urandom is not a SHA-1 PRNG, some apps
|
||||
// explicitly request a SHA1PRNG SecureRandom and we thus need to
|
||||
// prevent them from getting the default implementation whose output
|
||||
// may have low entropy.
|
||||
put("SecureRandom.SHA1PRNG", LinuxPRNGSecureRandom.class.getName());
|
||||
put("SecureRandom.SHA1PRNG ImplementedIn", "Software");
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* {@link SecureRandomSpi} which passes all requests to the Linux PRNG (
|
||||
* {@code /dev/urandom}).
|
||||
*/
|
||||
public static class LinuxPRNGSecureRandom extends SecureRandomSpi {
|
||||
|
||||
/*
|
||||
* IMPLEMENTATION NOTE: Requests to generate bytes and to mix in a seed
|
||||
* are passed through to the Linux PRNG (/dev/urandom). Instances of
|
||||
* this class seed themselves by mixing in the current time, PID, UID,
|
||||
* build fingerprint, and hardware serial number (where available) into
|
||||
* Linux PRNG.
|
||||
*
|
||||
* Concurrency: Read requests to the underlying Linux PRNG are
|
||||
* serialized (on sLock) to ensure that multiple threads do not get
|
||||
* duplicated PRNG output.
|
||||
*/
|
||||
|
||||
private static final File URANDOM_FILE = new File("/dev/urandom");
|
||||
|
||||
private static final Object sLock = new Object();
|
||||
|
||||
/**
|
||||
* Input stream for reading from Linux PRNG or {@code null} if not yet
|
||||
* opened.
|
||||
*
|
||||
* @GuardedBy("sLock")
|
||||
*/
|
||||
private static DataInputStream sUrandomIn;
|
||||
|
||||
/**
|
||||
* Output stream for writing to Linux PRNG or {@code null} if not yet
|
||||
* opened.
|
||||
*
|
||||
* @GuardedBy("sLock")
|
||||
*/
|
||||
private static OutputStream sUrandomOut;
|
||||
|
||||
/**
|
||||
* Whether this engine instance has been seeded. This is needed because
|
||||
* each instance needs to seed itself if the client does not explicitly
|
||||
* seed it.
|
||||
*/
|
||||
private boolean mSeeded;
|
||||
|
||||
@Override
|
||||
protected void engineSetSeed(byte[] bytes) {
|
||||
try {
|
||||
OutputStream out;
|
||||
synchronized (sLock) {
|
||||
out = getUrandomOutputStream();
|
||||
}
|
||||
out.write(bytes);
|
||||
out.flush();
|
||||
} catch (IOException e) {
|
||||
// On a small fraction of devices /dev/urandom is not writable.
|
||||
// Log and ignore.
|
||||
Log.w(PRNGFixes.class.getSimpleName(),
|
||||
"Failed to mix seed into " + URANDOM_FILE);
|
||||
} finally {
|
||||
mSeeded = true;
|
||||
}
|
||||
}
|
||||
|
||||
@Override
|
||||
protected void engineNextBytes(byte[] bytes) {
|
||||
if (!mSeeded) {
|
||||
// Mix in the device- and invocation-specific seed.
|
||||
engineSetSeed(generateSeed());
|
||||
}
|
||||
|
||||
try {
|
||||
DataInputStream in;
|
||||
synchronized (sLock) {
|
||||
in = getUrandomInputStream();
|
||||
}
|
||||
synchronized (in) {
|
||||
in.readFully(bytes);
|
||||
}
|
||||
} catch (IOException e) {
|
||||
throw new SecurityException("Failed to read from "
|
||||
+ URANDOM_FILE, e);
|
||||
}
|
||||
}
|
||||
|
||||
@Override
|
||||
protected byte[] engineGenerateSeed(int size) {
|
||||
byte[] seed = new byte[size];
|
||||
engineNextBytes(seed);
|
||||
return seed;
|
||||
}
|
||||
|
||||
private DataInputStream getUrandomInputStream() {
|
||||
synchronized (sLock) {
|
||||
if (sUrandomIn == null) {
|
||||
// NOTE: Consider inserting a BufferedInputStream between
|
||||
// DataInputStream and FileInputStream if you need higher
|
||||
// PRNG output performance and can live with future PRNG
|
||||
// output being pulled into this process prematurely.
|
||||
try {
|
||||
sUrandomIn = new DataInputStream(new FileInputStream(
|
||||
URANDOM_FILE));
|
||||
} catch (IOException e) {
|
||||
throw new SecurityException("Failed to open "
|
||||
+ URANDOM_FILE + " for reading", e);
|
||||
}
|
||||
}
|
||||
return sUrandomIn;
|
||||
}
|
||||
}
|
||||
|
||||
private OutputStream getUrandomOutputStream() throws IOException {
|
||||
synchronized (sLock) {
|
||||
if (sUrandomOut == null) {
|
||||
sUrandomOut = new FileOutputStream(URANDOM_FILE);
|
||||
}
|
||||
return sUrandomOut;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Generates a device- and invocation-specific seed to be mixed into the
|
||||
* Linux PRNG.
|
||||
*/
|
||||
private static byte[] generateSeed() {
|
||||
try {
|
||||
ByteArrayOutputStream seedBuffer = new ByteArrayOutputStream();
|
||||
DataOutputStream seedBufferOut = new DataOutputStream(seedBuffer);
|
||||
seedBufferOut.writeLong(System.currentTimeMillis());
|
||||
seedBufferOut.writeLong(System.nanoTime());
|
||||
seedBufferOut.writeInt(Process.myPid());
|
||||
seedBufferOut.writeInt(Process.myUid());
|
||||
seedBufferOut.write(BUILD_FINGERPRINT_AND_DEVICE_SERIAL);
|
||||
seedBufferOut.close();
|
||||
return seedBuffer.toByteArray();
|
||||
} catch (IOException e) {
|
||||
throw new SecurityException("Failed to generate seed", e);
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Gets the hardware serial number of this device.
|
||||
*
|
||||
* @return serial number or {@code null} if not available.
|
||||
*/
|
||||
private static String getDeviceSerialNumber() {
|
||||
// We're using the Reflection API because Build.SERIAL is only available
|
||||
// since API Level 9 (Gingerbread, Android 2.3).
|
||||
try {
|
||||
return (String) Build.class.getField("SERIAL").get(null);
|
||||
} catch (Exception ignored) {
|
||||
return null;
|
||||
}
|
||||
}
|
||||
|
||||
private static byte[] getBuildFingerprintAndDeviceSerial() {
|
||||
StringBuilder result = new StringBuilder();
|
||||
String fingerprint = Build.FINGERPRINT;
|
||||
if (fingerprint != null) {
|
||||
result.append(fingerprint);
|
||||
}
|
||||
String serial = getDeviceSerialNumber();
|
||||
if (serial != null) {
|
||||
result.append(serial);
|
||||
}
|
||||
try {
|
||||
return result.toString().getBytes("UTF-8");
|
||||
} catch (UnsupportedEncodingException e) {
|
||||
throw new RuntimeException("UTF-8 encoding not supported");
|
||||
}
|
||||
}
|
||||
}
|
||||
Loading…
Reference in a new issue