mirror of
https://github.com/moparisthebest/k-9
synced 2024-11-27 11:42:16 -05:00
Use Google's fix for the PRNG mess
Source: http://android-developers.blogspot.de/2013/08/some-securerandom-thoughts.html
This commit is contained in:
parent
20fcd6f63d
commit
4fe6f90428
@ -545,6 +545,8 @@ public class K9 extends Application {
|
|||||||
@Override
|
@Override
|
||||||
public void onCreate() {
|
public void onCreate() {
|
||||||
maybeSetupStrictMode();
|
maybeSetupStrictMode();
|
||||||
|
PRNGFixes.apply();
|
||||||
|
|
||||||
super.onCreate();
|
super.onCreate();
|
||||||
app = this;
|
app = this;
|
||||||
|
|
||||||
|
337
src/com/fsck/k9/PRNGFixes.java
Normal file
337
src/com/fsck/k9/PRNGFixes.java
Normal file
@ -0,0 +1,337 @@
|
|||||||
|
/*
|
||||||
|
* This software is provided 'as-is', without any express or implied
|
||||||
|
* warranty. In no event will Google be held liable for any damages
|
||||||
|
* arising from the use of this software.
|
||||||
|
*
|
||||||
|
* Permission is granted to anyone to use this software for any purpose,
|
||||||
|
* including commercial applications, and to alter it and redistribute it
|
||||||
|
* freely, as long as the origin is not misrepresented.
|
||||||
|
*/
|
||||||
|
|
||||||
|
package com.fsck.k9;
|
||||||
|
|
||||||
|
import android.os.Build;
|
||||||
|
import android.os.Process;
|
||||||
|
|
||||||
|
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();
|
||||||
|
mSeeded = true;
|
||||||
|
} catch (IOException e) {
|
||||||
|
throw new SecurityException(
|
||||||
|
"Failed to mix seed into " + URANDOM_FILE, e);
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
@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() {
|
||||||
|
synchronized (sLock) {
|
||||||
|
if (sUrandomOut == null) {
|
||||||
|
try {
|
||||||
|
sUrandomOut = new FileOutputStream(URANDOM_FILE);
|
||||||
|
} catch (IOException e) {
|
||||||
|
throw new SecurityException("Failed to open "
|
||||||
|
+ URANDOM_FILE + " for writing", e);
|
||||||
|
}
|
||||||
|
}
|
||||||
|
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 New Issue
Block a user