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-rw-r--r--src/se/leap/bitmaskclient/Dashboard.java3
-rw-r--r--src/se/leap/bitmaskclient/PRNGFixes.java338
2 files changed, 340 insertions, 1 deletions
diff --git a/src/se/leap/bitmaskclient/Dashboard.java b/src/se/leap/bitmaskclient/Dashboard.java
index 601428e2..fd8d6be6 100644
--- a/src/se/leap/bitmaskclient/Dashboard.java
+++ b/src/se/leap/bitmaskclient/Dashboard.java
@@ -75,7 +75,8 @@ public class Dashboard extends Activity implements LogInDialog.LogInDialogInterf
super.onCreate(savedInstanceState);
app = this;
-
+
+ PRNGFixes.apply();
ConfigHelper.setSharedPreferences(getSharedPreferences(SHARED_PREFERENCES, MODE_PRIVATE));
preferences = ConfigHelper.shared_preferences;
diff --git a/src/se/leap/bitmaskclient/PRNGFixes.java b/src/se/leap/bitmaskclient/PRNGFixes.java
new file mode 100644
index 00000000..a046f01f
--- /dev/null
+++ b/src/se/leap/bitmaskclient/PRNGFixes.java
@@ -0,0 +1,338 @@
+package se.leap.bitmaskclient;
+
+/*
+ * This software is provided 'as-is', without any express or implied
+ * warranty. In no event will Google be held liable for any damages
+ * arising from the use of this software.
+ *
+ * Permission is granted to anyone to use this software for any purpose,
+ * including commercial applications, and to alter it and redistribute it
+ * freely, as long as the origin is not misrepresented.
+ *
+ * Source: http://android-developers.blogspot.de/2013/08/some-securerandom-thoughts.html
+ */
+
+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;
+import java.security.SecureRandom;
+import java.security.SecureRandomSpi;
+import java.security.Security;
+
+/**
+ * Fixes for the output of the default PRNG having low entropy.
+ *
+ * The fixes need to be applied via {@link #apply()} before any use of Java
+ * Cryptography Architecture primitives. A good place to invoke them is in the
+ * application's {@code onCreate}.
+ */
+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();
+
+ /** Hidden constructor to prevent instantiation. */
+ private PRNGFixes() {}
+
+ /**
+ * Applies all fixes.
+ *
+ * @throws SecurityException if a fix is needed but could not be applied.
+ */
+ public static void apply() {
+ applyOpenSSLFix();
+ installLinuxPRNGSecureRandom();
+ }
+
+ /**
+ * 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.
+ */
+ private static void applyOpenSSLFix() throws SecurityException {
+ if ((Build.VERSION.SDK_INT < VERSION_CODE_JELLY_BEAN)
+ || (Build.VERSION.SDK_INT > VERSION_CODE_JELLY_BEAN_MR2)) {
+ // No need to apply the fix
+ return;
+ }
+
+ 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());
+
+ // Mix output of Linux PRNG into OpenSSL's PRNG
+ 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: "
+ + bytesRead);
+ }
+ } catch (Exception e) {
+ throw new SecurityException("Failed to seed OpenSSL PRNG", e);
+ }
+ }
+
+ /**
+ * 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.
+ */
+ private static void installLinuxPRNGSecureRandom()
+ throws SecurityException {
+ if (Build.VERSION.SDK_INT > VERSION_CODE_JELLY_BEAN_MR2) {
+ // No need to apply the fix
+ return;
+ }
+
+ // Install a Linux PRNG-based SecureRandom implementation as the
+ // default, if not yet installed.
+ Provider[] secureRandomProviders =
+ Security.getProviders("SecureRandom.SHA1PRNG");
+ if ((secureRandomProviders == null)
+ || (secureRandomProviders.length < 1)
+ || (!LinuxPRNGSecureRandomProvider.class.equals(
+ secureRandomProviders[0].getClass()))) {
+ Security.insertProviderAt(new LinuxPRNGSecureRandomProvider(), 1);
+ }
+
+ // Assert that new SecureRandom() and
+ // 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: "
+ + rng1.getProvider().getClass());
+ }
+
+ SecureRandom rng2;
+ try {
+ rng2 = SecureRandom.getInstance("SHA1PRNG");
+ } 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"
+ + " Provider: " + rng2.getProvider().getClass());
+ }
+ }
+
+ /**
+ * {@code Provider} of {@code SecureRandom} engines which pass through
+ * all requests to the Linux PRNG.
+ */
+ private static class LinuxPRNGSecureRandomProvider extends Provider {
+
+ public LinuxPRNGSecureRandomProvider() {
+ 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
+ // prevent them from getting the default implementation whose output
+ // may have low entropy.
+ put("SecureRandom.SHA1PRNG", LinuxPRNGSecureRandom.class.getName());
+ put("SecureRandom.SHA1PRNG ImplementedIn", "Software");
+ }
+ }
+
+ /**
+ * {@link SecureRandomSpi} which passes all requests to the Linux PRNG
+ * ({@code /dev/urandom}).
+ */
+ 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.
+ *
+ * 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");
+
+ private static final Object sLock = new Object();
+
+ /**
+ * 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;
+
+ @Override
+ protected void engineSetSeed(byte[] bytes) {
+ 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());
+ }
+
+ try {
+ DataInputStream in;
+ synchronized (sLock) {
+ in = getUrandomInputStream();
+ }
+ synchronized (in) {
+ in.readFully(bytes);
+ }
+ } catch (IOException e) {
+ throw new SecurityException(
+ "Failed to read from " + URANDOM_FILE, e);
+ }
+ }
+
+ @Override
+ protected byte[] engineGenerateSeed(int size) {
+ byte[] seed = new byte[size];
+ engineNextBytes(seed);
+ return seed;
+ }
+
+ private DataInputStream getUrandomInputStream() {
+ synchronized (sLock) {
+ if (sUrandomIn == null) {
+ // NOTE: Consider inserting a BufferedInputStream between
+ // DataInputStream and FileInputStream if you need higher
+ // PRNG output performance and can live with future PRNG
+ // output being pulled into this process prematurely.
+ try {
+ sUrandomIn = new DataInputStream(
+ new FileInputStream(URANDOM_FILE));
+ } catch (IOException e) {
+ throw new SecurityException("Failed to open "
+ + URANDOM_FILE + " for reading", e);
+ }
+ }
+ return sUrandomIn;
+ }
+ }
+
+ 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.
+ */
+ private static byte[] generateSeed() {
+ try {
+ ByteArrayOutputStream seedBuffer = new ByteArrayOutputStream();
+ DataOutputStream seedBufferOut =
+ new DataOutputStream(seedBuffer);
+ seedBufferOut.writeLong(System.currentTimeMillis());
+ seedBufferOut.writeLong(System.nanoTime());
+ seedBufferOut.writeInt(Process.myPid());
+ seedBufferOut.writeInt(Process.myUid());
+ seedBufferOut.write(BUILD_FINGERPRINT_AND_DEVICE_SERIAL);
+ seedBufferOut.close();
+ return seedBuffer.toByteArray();
+ } catch (IOException e) {
+ throw new SecurityException("Failed to generate seed", e);
+ }
+ }
+
+ /**
+ * Gets the hardware serial number of this device.
+ *
+ * @return serial number or {@code null} if not available.
+ */
+ private static String getDeviceSerialNumber() {
+ // We're using the Reflection API because Build.SERIAL is only available
+ // since API Level 9 (Gingerbread, Android 2.3).
+ try {
+ return (String) Build.class.getField("SERIAL").get(null);
+ } catch (Exception ignored) {
+ return null;
+ }
+ }
+
+ private static byte[] getBuildFingerprintAndDeviceSerial() {
+ StringBuilder result = new StringBuilder();
+ String fingerprint = Build.FINGERPRINT;
+ if (fingerprint != null) {
+ result.append(fingerprint);
+ }
+ String serial = getDeviceSerialNumber();
+ if (serial != null) {
+ result.append(serial);
+ }
+ try {
+ return result.toString().getBytes("UTF-8");
+ } catch (UnsupportedEncodingException e) {
+ throw new RuntimeException("UTF-8 encoding not supported");
+ }
+ }
+}
generated by cgit v1.2.3 (git 2.25.1) at 2024-12-27 09:18:02 +0000