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Code Issues Releases Wiki Activity

Updated PRNGFixes from official blogpost

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This commit is contained in:
Dominik Schürmann 2013-09-17 16:53:50 +02:00
parent 0625061018
commit bb657e4add
2 changed files with 120 additions and 97 deletions
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7
OpenPGP-Keychain/AndroidManifest.xml
View File

@ -350,7 +350,7 @@
android:name=".ui.HelpActivity"
android:label="@string/title_help" />
<!-- Internal services/content provider (not exported) -->
<!-- Internal services/content providers (not exported) -->
<service
android:name=".service.PassphraseCacheService"
android:exported="false"
@ -364,7 +364,7 @@
android:authorities="org.sufficientlysecure.keychain.provider"
android:exported="false" />
<!-- Internal classes of OpenPGP (not exported) -->
<!-- Internal classes of the remote APIs (not exported) -->
<activity
android:name="org.sufficientlysecure.keychain.service.remote.RemoteServiceActivity"
android:exported="false"
@ -398,7 +398,6 @@
</service>
<!-- Extended Remote API -->
<service
android:name="org.sufficientlysecure.keychain.service.remote.ExtendedApiService"
android:enabled="true"
@ -416,7 +415,7 @@
<!-- TODO: authority! Make this API with content provider uris -->
<!-- <provider -->
<!-- android:name="org.sufficientlysecure.keychain.provider.KeychainServiceBlobProvider" -->
<!-- android:authorities="org.sufficientlysecure.keychain.provider.apgserviceblobprovider" -->
<!-- android:authorities="org.sufficientlysecure.keychain.provider.KeychainServiceBlobProvider" -->
<!-- android:permission="org.sufficientlysecure.keychain.permission.ACCESS_API" /> -->
</application>

192
OpenPGP-Keychain/src/org/sufficientlysecure/keychain/util/PRNGFixes.java
View File

@ -12,13 +12,16 @@ package org.sufficientlysecure.keychain.util;
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;
@ -51,22 +54,27 @@ import java.security.Security;
* random version, now Samsung's SELinux policy also prevents apps from opening
* /dev/urandom for writing. Since we shouldn't need to write to /dev/urandom anyway
* we now simply don't.
*
*
* Sep 17, 2013:
* Updated from official blogpost:
* Update: the original code sample below crashed on a small fraction of Android
* devices due to /dev/urandom not being writable. We have now updated the code sample to handle this case gracefully.
*/
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();
private static final byte[] BUILD_FINGERPRINT_AND_DEVICE_SERIAL =
getBuildFingerprintAndDeviceSerial();
/** Hidden constructor to prevent instantiation. */
private PRNGFixes() {
}
private PRNGFixes() {}
/**
* Applies all fixes.
*
* @throws SecurityException
* if a fix is needed but could not be applied.
* @throws SecurityException if a fix is needed but could not be applied.
*/
public static void apply() {
applyOpenSSLFix();
@ -74,10 +82,10 @@ public final class PRNGFixes {
}
/**
* Applies the fix for OpenSSL PRNG having low entropy. Does nothing if the fix is not needed.
* 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.
* @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)
@ -89,15 +97,17 @@ public final class PRNGFixes {
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());
.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")
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: "
throw new IOException(
"Unexpected number of bytes read from Linux PRNG: "
+ bytesRead);
}
} catch (Exception e) {
@ -106,14 +116,14 @@ public final class PRNGFixes {
}
/**
* 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.
* 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.
* @throws SecurityException if the fix is needed but could not be applied.
*/
private static void installLinuxPRNGSecureRandom() throws SecurityException {
private static void installLinuxPRNGSecureRandom()
throws SecurityException {
if (Build.VERSION.SDK_INT > VERSION_CODE_JELLY_BEAN_MR2) {
// No need to apply the fix
return;
@ -121,11 +131,12 @@ public final class PRNGFixes {
// Install a Linux PRNG-based SecureRandom implementation as the
// default, if not yet installed.
Provider[] secureRandomProviders = Security.getProviders("SecureRandom.SHA1PRNG");
Provider[] secureRandomProviders =
Security.getProviders("SecureRandom.SHA1PRNG");
if ((secureRandomProviders == null)
|| (secureRandomProviders.length < 1)
|| (!LinuxPRNGSecureRandomProvider.class
.equals(secureRandomProviders[0].getClass()))) {
|| (!LinuxPRNGSecureRandomProvider.class.equals(
secureRandomProviders[0].getClass()))) {
Security.insertProviderAt(new LinuxPRNGSecureRandomProvider(), 1);
}
@ -133,8 +144,10 @@ public final class PRNGFixes {
// 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: "
if (!LinuxPRNGSecureRandomProvider.class.equals(
rng1.getProvider().getClass())) {
throw new SecurityException(
"new SecureRandom() backed by wrong Provider: "
+ rng1.getProvider().getClass());
}
@ -144,21 +157,24 @@ public final class PRNGFixes {
} 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"
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.
* {@code Provider} of {@code SecureRandom} engines which pass through
* all requests to the Linux PRNG.
*/
@SuppressWarnings("serial")
private static class LinuxPRNGSecureRandomProvider extends Provider {
public LinuxPRNGSecureRandomProvider() {
super("LinuxPRNG", 1.0, "A Linux-specific random number provider that uses"
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
@ -170,19 +186,21 @@ public final class PRNGFixes {
}
/**
* {@link SecureRandomSpi} which passes all requests to the Linux PRNG ({@code /dev/urandom}).
* {@link SecureRandomSpi} which passes all requests to the Linux PRNG
* ({@code /dev/urandom}).
*/
@SuppressWarnings("serial")
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.
* 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.
* 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");
@ -190,46 +208,53 @@ public final class PRNGFixes {
private static final Object sLock = new Object();
/**
* Input stream for reading from Linux PRNG or {@code null} if not yet opened.
* 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;
/**
* 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);
// }
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());
// }
if (!mSeeded) {
// Mix in the device- and invocation-specific seed.
engineSetSeed(generateSeed());
}
try {
DataInputStream in;
@ -240,7 +265,8 @@ public final class PRNGFixes {
in.readFully(bytes);
}
} catch (IOException e) {
throw new SecurityException("Failed to read from " + URANDOM_FILE, e);
throw new SecurityException(
"Failed to read from " + URANDOM_FILE, e);
}
}
@ -259,38 +285,36 @@ public final class PRNGFixes {
// PRNG output performance and can live with future PRNG
// output being pulled into this process prematurely.
try {
sUrandomIn = new DataInputStream(new FileInputStream(URANDOM_FILE));
sUrandomIn = new DataInputStream(
new FileInputStream(URANDOM_FILE));
} catch (IOException e) {
throw new SecurityException("Failed to open " + URANDOM_FILE
+ " for reading", 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;
// }
// }
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.
* 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);
DataOutputStream seedBufferOut =
new DataOutputStream(seedBuffer);
seedBufferOut.writeLong(System.currentTimeMillis());
seedBufferOut.writeLong(System.nanoTime());
seedBufferOut.writeInt(Process.myPid());