Cleanup: Consolidate initialization of Android's SecureRandom class.

This replaces some copy-pasted snippets of code with a centralized
utility for securely initializing a SecureRandom instance (needed for
Android versions <= 4.3).

BUG=402732

Review URL: https://codereview.chromium.org/624183002

Cr-Commit-Position: refs/heads/master@{#299788}

remoting/android/java/src/org/chromium/chromoting/SecureRandomInitializer.java → base/android/java/src/org/chromium/base/SecureRandomInitializer.java

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-package org.chromium.chromoting;
+package org.chromium.base;
 
 import java.io.FileInputStream;
 import java.io.IOException;
@@ -16,6 +16,8 @@ import java.security.SecureRandom;
 public class SecureRandomInitializer {
     private static final int NUM_RANDOM_BYTES = 16;
 
+    private static byte[] sSeedBytes = new byte[NUM_RANDOM_BYTES];
+
     /**
      * Safely initializes the random number generator, by seeding it with data from /dev/urandom.
      */
@@ -23,11 +25,10 @@ public class SecureRandomInitializer {
         FileInputStream fis = null;
         try {
             fis = new FileInputStream("/dev/urandom");
-            byte[] bytes = new byte[NUM_RANDOM_BYTES];
-            if (bytes.length != fis.read(bytes)) {
+            if (fis.read(sSeedBytes) != sSeedBytes.length) {
                 throw new IOException("Failed to get enough random data.");
             }
-            generator.setSeed(bytes);
+            generator.setSeed(sSeedBytes);
         } finally {
             try {
                 if (fis != null) {

chrome/android/java/src/org/chromium/chrome/browser/WebappAuthenticator.java

@@ -8,6 +8,8 @@ import android.content.Context;
 import android.os.AsyncTask;
 import android.util.Log;
 
+import org.chromium.base.SecureRandomInitializer;
+
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
@@ -191,20 +193,7 @@ public class WebappAuthenticator {
                 public SecretKey call() throws Exception {
                     KeyGenerator generator = KeyGenerator.getInstance(MAC_ALGORITHM_NAME);
                     SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
-
-                    // Versions of SecureRandom from Android <= 4.3 do not seed themselves as
-                    // securely as possible. This workaround should suffice until the fixed version
-                    // is deployed to all users. getRandomBytes, which reads from /dev/urandom,
-                    // which is as good as the platform can get.
-                    //
-                    // TODO(palmer): Consider getting rid of this once the updated platform has
-                    // shipped to everyone. Alternately, leave this in as a defense against other
-                    // bugs in SecureRandom.
-                    byte[] seed = getRandomBytes(MAC_KEY_BYTE_COUNT);
-                    if (seed == null) {
-                        return null;
-                    }
-                    random.setSeed(seed);
+                    SecureRandomInitializer.initialize(random);
                     generator.init(MAC_KEY_BYTE_COUNT * 8, random);
                     return generator.generateKey();
                 }
@@ -213,29 +202,6 @@ public class WebappAuthenticator {
         }
     }
 
-    private static byte[] getRandomBytes(int count) {
-        FileInputStream fis = null;
-        try {
-            fis = new FileInputStream("/dev/urandom");
-            byte[] bytes = new byte[count];
-            if (bytes.length != fis.read(bytes)) {
-                return null;
-            }
-            return bytes;
-        } catch (Throwable t) {
-            // This causes the ultimate caller, i.e. getMac, to fail.
-            return null;
-        } finally {
-            try {
-                if (fis != null) {
-                    fis.close();
-                }
-            } catch (IOException e) {
-                // Nothing we can do.
-            }
-        }
-    }
-
     /**
      * @return A Mac, or null if it is not possible to instantiate one.
      */

content/public/android/java/src/org/chromium/content/browser/crypto/CipherFactory.java

@@ -8,6 +8,8 @@ import android.os.AsyncTask;
 import android.os.Bundle;
 import android.util.Log;
 
+import org.chromium.base.SecureRandomInitializer;
+
 import java.io.IOException;
 import java.security.GeneralSecurityException;
 import java.security.Key;
@@ -150,9 +152,8 @@ public class CipherFactory {
             @Override
             public CipherData call() {
                 // Poll random data to generate initialization parameters for the Cipher.
-                byte[] seed, iv;
+                byte[] iv;
                 try {
-                    seed = mRandomNumberProvider.getBytes(NUM_BYTES);
                     iv = mRandomNumberProvider.getBytes(NUM_BYTES);
                 } catch (IOException e) {
                     Log.e(TAG, "Couldn't get generator data.");
@@ -163,20 +164,15 @@ public class CipherFactory {
                 }
 
                 try {
-                    // Old versions of SecureRandom do not seed themselves as securely as possible.
-                    // This workaround should suffice until the fixed version is deployed to all
-                    // users. The seed comes from RandomNumberProvider.getBytes(), which reads
-                    // from /dev/urandom, which is as good as the platform can get.
-                    //
-                    // TODO(palmer): Consider getting rid of this once the updated platform has
-                    // shipped to everyone. Alternately, leave this in as a defense against other
-                    // bugs in SecureRandom.
                     SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
-                    random.setSeed(seed);
+                    SecureRandomInitializer.initialize(random);
 
                     KeyGenerator generator = KeyGenerator.getInstance("AES");
                     generator.init(128, random);
                     return new CipherData(generator.generateKey(), iv);
+                } catch (IOException e) {
+                    Log.e(TAG, "Couldn't get generator data.");
+                    return null;
                 } catch (GeneralSecurityException e) {
                     Log.e(TAG, "Couldn't get generator instances.");
                     return null;
@@ -270,4 +266,4 @@ public class CipherFactory {
     private CipherFactory() {
         mRandomNumberProvider = new ByteArrayGenerator();
     }
-}
+}
\ No newline at end of file

remoting/android/java/src/org/chromium/chromoting/ThirdPartyTokenFetcher.java

@@ -15,6 +15,8 @@ import android.text.TextUtils;
 import android.util.Base64;
 import android.util.Log;
 
+import org.chromium.base.SecureRandomInitializer;
+
 import java.io.IOException;
 import java.security.SecureRandom;
 import java.util.ArrayList;