Update RandomBlock to use RandomAccessFile. This helps
prevent certain unusual conditions from corrupting the
entropy file. (for example, if Android should happen to
crash while a write is in progress)
diff --git a/services/java/com/android/server/RandomBlock.java b/services/java/com/android/server/RandomBlock.java
index c08761e..4ac1c6e 100644
--- a/services/java/com/android/server/RandomBlock.java
+++ b/services/java/com/android/server/RandomBlock.java
@@ -19,12 +19,12 @@
import android.util.Log;
import java.io.Closeable;
+import java.io.DataOutput;
import java.io.EOFException;
import java.io.FileInputStream;
-import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
-import java.io.OutputStream;
+import java.io.RandomAccessFile;
/**
* A 4k block of random {@code byte}s.
@@ -63,17 +63,27 @@
void toFile(String filename) throws IOException {
Log.v(TAG, "writing to file " + filename);
- OutputStream out = null;
+ RandomAccessFile out = null;
try {
- // TODO: Investigate using RandomAccessFile
- out = new FileOutputStream(filename);
- toStream(out);
+ out = new RandomAccessFile(filename, "rws");
+ toDataOut(out);
+ truncateIfPossible(out);
} finally {
close(out);
}
}
- private void toStream(OutputStream out) throws IOException {
+ private static void truncateIfPossible(RandomAccessFile f) {
+ try {
+ f.setLength(BLOCK_SIZE);
+ } catch (IOException e) {
+ // ignore this exception. Sometimes, the file we're trying to
+ // write is a character device, such as /dev/urandom, and
+ // these character devices do not support setting the length.
+ }
+ }
+
+ private void toDataOut(DataOutput out) throws IOException {
out.write(block);
}
