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Commit 2854254c authored by Nick Kralevich's avatar Nick Kralevich
Browse files

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)
parent 77dcf735

services/java/com/android/server/RandomBlock.java

+17 −7
Original line number Diff line number Diff line
@@ -19,12 +19,12 @@ package com.android.server; 
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 @@ class RandomBlock { 


    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);

    }