The Tor Browser: mobile/android/base/background/fxa/FxAccountUtils.java@fc2d59ddac77 (annotated)

mobile/android/base/background/fxa/FxAccountUtils.java@fc2d59ddac77 (annotated)

mobile/android/base/background/fxa/FxAccountUtils.java

Wed, 31 Dec 2014 07:22:50 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 07:22:50 +0100
branch: TOR_BUG_3246
changeset 4: fc2d59ddac77
permissions: -rw-r--r--

Correct previous dual key logic pending first delivery installment.

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 package org.mozilla.gecko.background.fxa;
 import java.io.UnsupportedEncodingException;
 import java.math.BigInteger;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.security.GeneralSecurityException;
 import java.security.InvalidKeyException;
 import java.security.NoSuchAlgorithmException;
 import org.mozilla.gecko.background.common.log.Logger;
 import org.mozilla.gecko.background.nativecode.NativeCrypto;
 import org.mozilla.gecko.sync.Utils;
 import org.mozilla.gecko.sync.crypto.HKDF;
 import org.mozilla.gecko.sync.crypto.KeyBundle;
 import org.mozilla.gecko.sync.crypto.PBKDF2;
 public class FxAccountUtils {
   private static final String LOG_TAG = FxAccountUtils.class.getSimpleName();
   public static final int SALT_LENGTH_BYTES = 32;
   public static final int SALT_LENGTH_HEX = 2 * SALT_LENGTH_BYTES;
   public static final int HASH_LENGTH_BYTES = 16;
   public static final int HASH_LENGTH_HEX = 2 * HASH_LENGTH_BYTES;
   public static final int CRYPTO_KEY_LENGTH_BYTES = 32;
   public static final int CRYPTO_KEY_LENGTH_HEX = 2 * CRYPTO_KEY_LENGTH_BYTES;
   public static final String KW_VERSION_STRING = "identity.mozilla.com/picl/v1/";
   public static final int NUMBER_OF_QUICK_STRETCH_ROUNDS = 1000;
   public static String bytes(String string) throws UnsupportedEncodingException {
     return Utils.byte2Hex(string.getBytes("UTF-8"));
   }
   public static byte[] KW(String name) throws UnsupportedEncodingException {
     return Utils.concatAll(
         KW_VERSION_STRING.getBytes("UTF-8"),
         name.getBytes("UTF-8"));
   }
   public static byte[] KWE(String name, byte[] emailUTF8) throws UnsupportedEncodingException {
     return Utils.concatAll(
         KW_VERSION_STRING.getBytes("UTF-8"),
         name.getBytes("UTF-8"),
         ":".getBytes("UTF-8"),
         emailUTF8);
   }
   /**
    * Calculate the SRP verifier <tt>x</tt> value.
    */
   public static BigInteger srpVerifierLowercaseX(byte[] emailUTF8, byte[] srpPWBytes, byte[] srpSaltBytes)
       throws NoSuchAlgorithmException, UnsupportedEncodingException {
     byte[] inner = Utils.sha256(Utils.concatAll(emailUTF8, ":".getBytes("UTF-8"), srpPWBytes));
     byte[] outer = Utils.sha256(Utils.concatAll(srpSaltBytes, inner));
     return new BigInteger(1, outer);
   }
   /**
    * Calculate the SRP verifier <tt>v</tt> value.
    */
   public static BigInteger srpVerifierLowercaseV(byte[] emailUTF8, byte[] srpPWBytes, byte[] srpSaltBytes, BigInteger g, BigInteger N)
       throws NoSuchAlgorithmException, UnsupportedEncodingException {
     BigInteger x = srpVerifierLowercaseX(emailUTF8, srpPWBytes, srpSaltBytes);
     BigInteger v = g.modPow(x, N);
     return v;
   }
   /**
    * Format x modulo N in hexadecimal, using as many characters as N takes (in hexadecimal).
    * @param x to format.
    * @param N modulus.
    * @return x modulo N in hexadecimal.
    */
   public static String hexModN(BigInteger x, BigInteger N) {
     int byteLength = (N.bitLength() + 7) / 8;
     int hexLength = 2 * byteLength;
     return Utils.byte2Hex(Utils.hex2Byte((x.mod(N)).toString(16), byteLength), hexLength);
   }
   /**
    * The first engineering milestone of PICL (Profile-in-the-Cloud) was
    * comprised of Sync 1.1 fronted by a Firefox Account. The sync key was
    * generated from the Firefox Account password-derived kB value using this
    * method.
    */
   public static KeyBundle generateSyncKeyBundle(final byte[] kB) throws InvalidKeyException, NoSuchAlgorithmException, UnsupportedEncodingException {
     byte[] encryptionKey = new byte[32];
     byte[] hmacKey = new byte[32];
     byte[] derived = HKDF.derive(kB, new byte[0], FxAccountUtils.KW("oldsync"), 2*32);
     System.arraycopy(derived, 0*32, encryptionKey, 0, 1*32);
     System.arraycopy(derived, 1*32, hmacKey, 0, 1*32);
     return new KeyBundle(encryptionKey, hmacKey);
   }
   /**
    * Firefox Accounts are password authenticated, but clients should not store
    * the plain-text password for any amount of time. Equivalent, but slightly
    * more secure, is the quickly client-side stretched password.
    * <p>
    * We separate this since multiple login-time operations want it, and the
    * PBKDF2 operation is computationally expensive.
    */
   public static byte[] generateQuickStretchedPW(byte[] emailUTF8, byte[] passwordUTF8) throws GeneralSecurityException, UnsupportedEncodingException {
     byte[] S = FxAccountUtils.KWE("quickStretch", emailUTF8);
     try {
       return NativeCrypto.pbkdf2SHA256(passwordUTF8, S, NUMBER_OF_QUICK_STRETCH_ROUNDS, 32);
     } catch (final LinkageError e) {
       // This will throw UnsatisifiedLinkError (missing mozglue) the first time it is called, and
       // ClassNotDefFoundError, for the uninitialized NativeCrypto class, each subsequent time this
       // is called; LinkageError is their common ancestor.
       Logger.warn(LOG_TAG, "Got throwable stretching password using native pbkdf2SHA256 " +
           "implementation; ignoring and using Java implementation.", e);
       return PBKDF2.pbkdf2SHA256(passwordUTF8, S, NUMBER_OF_QUICK_STRETCH_ROUNDS, 32);
     }
   }
   /**
    * The password-derived credential used to authenticate to the Firefox Account
    * auth server.
    */
   public static byte[] generateAuthPW(byte[] quickStretchedPW) throws GeneralSecurityException, UnsupportedEncodingException {
     return HKDF.derive(quickStretchedPW, new byte[0], FxAccountUtils.KW("authPW"), 32);
   }
   /**
    * The password-derived credential used to unwrap keys managed by the Firefox
    * Account auth server.
    */
   public static byte[] generateUnwrapBKey(byte[] quickStretchedPW) throws GeneralSecurityException, UnsupportedEncodingException {
     return HKDF.derive(quickStretchedPW, new byte[0], FxAccountUtils.KW("unwrapBkey"), 32);
   }
   public static byte[] unwrapkB(byte[] unwrapkB, byte[] wrapkB) {
     if (unwrapkB == null) {
       throw new IllegalArgumentException("unwrapkB must not be null");
     }
     if (wrapkB == null) {
       throw new IllegalArgumentException("wrapkB must not be null");
     }
     if (unwrapkB.length != CRYPTO_KEY_LENGTH_BYTES || wrapkB.length != CRYPTO_KEY_LENGTH_BYTES) {
       throw new IllegalArgumentException("unwrapkB and wrapkB must be " + CRYPTO_KEY_LENGTH_BYTES + " bytes long");
     }
     byte[] kB = new byte[CRYPTO_KEY_LENGTH_BYTES];
     for (int i = 0; i < wrapkB.length; i++) {
       kB[i] = (byte) (wrapkB[i] ^ unwrapkB[i]);
     }
     return kB;
   }
   /**
    * The token server accepts an X-Client-State header, which is the
    * lowercase-hex-encoded first 16 bytes of the SHA-256 hash of the
    * bytes of kB.
    * @param kB a byte array, expected to be 32 bytes long.
    * @return a 32-character string.
    * @throws NoSuchAlgorithmException
    */
   public static String computeClientState(byte[] kB) throws NoSuchAlgorithmException {
     if (kB == null ||
         kB.length != 32) {
       throw new IllegalArgumentException("Unexpected kB.");
     }
     byte[] sha256 = Utils.sha256(kB);
     byte[] truncated = new byte[16];
     System.arraycopy(sha256, 0, truncated, 0, 16);
     return Utils.byte2Hex(truncated);    // This is automatically lowercase.
   }
   /**
    * Given an endpoint, calculate the corresponding BrowserID audience.
    * <p>
    * This is the domain, in web parlance.
    *
    * @param serverURI endpoint.
    * @return BrowserID audience.
    * @throws URISyntaxException
    */
   public static String getAudienceForURL(String serverURI) throws URISyntaxException {
     URI uri = new URI(serverURI);
     return new URI(uri.getScheme(), uri.getHost(), null, null).toString();
   }
 }

The Tor Browser / annotate

mobile/android/base/background/fxa/FxAccountUtils.java@fc2d59ddac77 (annotated)

mobile/android/base/background/fxa/FxAccountUtils.java