diff options
Diffstat (limited to 'src/eu/siacs/conversations/utils/PRNGFixes.java')
| -rw-r--r-- | src/eu/siacs/conversations/utils/PRNGFixes.java | 539 |
1 files changed, 270 insertions, 269 deletions
diff --git a/src/eu/siacs/conversations/utils/PRNGFixes.java b/src/eu/siacs/conversations/utils/PRNGFixes.java index cf28ff30..8fe67234 100644 --- a/src/eu/siacs/conversations/utils/PRNGFixes.java +++ b/src/eu/siacs/conversations/utils/PRNGFixes.java @@ -21,306 +21,307 @@ 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(); + 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() {} + /** 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 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; - } + /** + * 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()); + 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); - } - } + // 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; - } + /** + * 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); - } + // 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()); - } + // 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()); - } - } + 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 { + /** + * {@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"); - } - } + 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 { + /** + * {@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. - */ + /* + * 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 File URANDOM_FILE = new File("/dev/urandom"); - private static final Object sLock = new Object(); + 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; + /** + * 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; + /** + * 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; + /** + * 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 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()); - } + @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); - } - } + 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; - } + @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 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; - } - } - } + 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); - } - } + /** + * 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; - } - } + /** + * 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"); - } - } + 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"); + } + } }
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