am aa947f15: am a9bce468: am 84742149: Merge "Make EntropyMixer mix in output... (87e385ef) · Commits · e / os / android_frameworks_base

services/java/com/android/server/EntropyMixer.java

+34 −3

Original line number	Original line	Diff line number	Diff line
	@@ -36,7 +36,8 @@ import android.util.Slog;

	/**		/**
	* A service designed to load and periodically save "randomness"		* A service designed to load and periodically save "randomness"
	* for the Linux kernel.		* for the Linux kernel RNG and to mix in data from Hardware RNG (if present)
			* into the Linux RNG.
	*		*
	* <p>When a Linux system starts up, the entropy pool associated with		* <p>When a Linux system starts up, the entropy pool associated with
	* {@code /dev/random} may be in a fairly predictable state. Applications which		* {@code /dev/random} may be in a fairly predictable state. Applications which
	@@ -45,6 +46,13 @@ import android.util.Slog;
	* this effect, it's helpful to carry the entropy pool information across		* this effect, it's helpful to carry the entropy pool information across
	* shutdowns and startups.		* shutdowns and startups.
	*		*
			* <p>On systems with Hardware RNG (/dev/hw_random), a block of output from HW
			* RNG is mixed into the Linux RNG on EntropyMixer's startup and whenever
			* EntropyMixer periodically runs to save a block of output from Linux RNG on
			* disk. This mixing is done in a way that does not increase the Linux RNG's
			* entropy estimate is not increased. This is to avoid having to trust/verify
			* the quality and authenticity of the "randomness" of the HW RNG.
			*
	* <p>This class was modeled after the script in		* <p>This class was modeled after the script in
	* <a href="http://www.kernel.org/doc/man-pages/online/pages/man4/random.4.html">man		* <a href="http://www.kernel.org/doc/man-pages/online/pages/man4/random.4.html">man
	* 4 random</a>.		* 4 random</a>.
	@@ -57,6 +65,7 @@ public class EntropyMixer extends Binder {
	private static final long START_NANOTIME = System.nanoTime();		private static final long START_NANOTIME = System.nanoTime();

	private final String randomDevice;		private final String randomDevice;
			private final String hwRandomDevice;
	private final String entropyFile;		private final String entropyFile;

	/**		/**
	@@ -69,6 +78,7 @@ public class EntropyMixer extends Binder {
	Slog.e(TAG, "Will not process invalid message");		Slog.e(TAG, "Will not process invalid message");
	return;		return;
	}		}
			addHwRandomEntropy();
	writeEntropy();		writeEntropy();
	scheduleEntropyWriter();		scheduleEntropyWriter();
	}		}
	@@ -82,18 +92,25 @@ public class EntropyMixer extends Binder {
	};		};

	public EntropyMixer(Context context) {		public EntropyMixer(Context context) {
	this(context, getSystemDir() + "/entropy.dat", "/dev/urandom");		this(context, getSystemDir() + "/entropy.dat", "/dev/urandom", "/dev/hw_random");
	}		}

	/** Test only interface, not for public use */		/** Test only interface, not for public use */
	public EntropyMixer(Context context, String entropyFile, String randomDevice) {		public EntropyMixer(
			Context context,
			String entropyFile,
			String randomDevice,
			String hwRandomDevice) {
	if (randomDevice == null) { throw new NullPointerException("randomDevice"); }		if (randomDevice == null) { throw new NullPointerException("randomDevice"); }
			if (hwRandomDevice == null) { throw new NullPointerException("hwRandomDevice"); }
	if (entropyFile == null) { throw new NullPointerException("entropyFile"); }		if (entropyFile == null) { throw new NullPointerException("entropyFile"); }

	this.randomDevice = randomDevice;		this.randomDevice = randomDevice;
			this.hwRandomDevice = hwRandomDevice;
	this.entropyFile = entropyFile;		this.entropyFile = entropyFile;
	loadInitialEntropy();		loadInitialEntropy();
	addDeviceSpecificEntropy();		addDeviceSpecificEntropy();
			addHwRandomEntropy();
	writeEntropy();		writeEntropy();
	scheduleEntropyWriter();		scheduleEntropyWriter();
	IntentFilter broadcastFilter = new IntentFilter(Intent.ACTION_SHUTDOWN);		IntentFilter broadcastFilter = new IntentFilter(Intent.ACTION_SHUTDOWN);
	@@ -168,6 +185,20 @@ public class EntropyMixer extends Binder {
	}		}
	}		}

			/**
			* Mixes in the output from HW RNG (if present) into the Linux RNG.
			*/
			private void addHwRandomEntropy() {
			try {
			RandomBlock.fromFile(hwRandomDevice).toFile(randomDevice, false);
			Slog.i(TAG, "Added HW RNG output to entropy pool");
			} catch (FileNotFoundException ignored) {
			// HW RNG not present/exposed -- ignore
			} catch (IOException e) {
			Slog.w(TAG, "Failed to add HW RNG output to entropy pool", e);
			}
			}

	private static String getSystemDir() {		private static String getSystemDir() {
	File dataDir = Environment.getDataDirectory();		File dataDir = Environment.getDataDirectory();
	File systemDir = new File(dataDir, "system");		File systemDir = new File(dataDir, "system");

services/tests/servicestests/src/com/android/server/EntropyMixerTest.java

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -34,7 +34,7 @@ public class EntropyMixerTest extends AndroidTestCase {
	assertEquals(0, FileUtils.readTextFile(file, 0, null).length());		assertEquals(0, FileUtils.readTextFile(file, 0, null).length());

	// The constructor has the side effect of writing to file		// The constructor has the side effect of writing to file
	new EntropyMixer(getContext(), "/dev/null", file.getCanonicalPath());		new EntropyMixer(getContext(), "/dev/null", file.getCanonicalPath(), "/dev/null");

	assertTrue(FileUtils.readTextFile(file, 0, null).length() > 0);		assertTrue(FileUtils.readTextFile(file, 0, null).length() > 0);
	}		}