1 files changed, 217 insertions, 0 deletions
diff --git a/mobile/android/services/src/main/java/org/mozilla/gecko/background/fxa/FxAccountUtils.java b/mobile/android/services/src/main/java/org/mozilla/gecko/background/fxa/FxAccountUtils.java
new file mode 100644
index 000000000..2d29725a0
--- /dev/null
+++ b/mobile/android/services/src/main/java/org/mozilla/gecko/background/fxa/FxAccountUtils.java
@@ -0,0 +1,217 @@
+/* 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.AppConstants;
+import org.mozilla.gecko.R;
+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;
+
+import android.content.Context;
+
+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;
+
+  // For extra debugging.  Not final so it can be changed from Fennec, or from
+  // an add-on.
+  public static boolean LOG_PERSONAL_INFORMATION = false;
+
+  public static void pii(String tag, String message) {
+    if (FxAccountUtils.LOG_PERSONAL_INFORMATION) {
+      Logger.info(tag, "$$FxA PII$$: " + message);
+    }
+  }
+
+  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 UnsatisfiedLinkError (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(), null, uri.getHost(), uri.getPort(), null, null, null).toString();
+  }
+
+  public static String defaultClientName(Context context) {
+    String name = AppConstants.MOZ_APP_DISPLAYNAME; // The display name is never translated.
+    // Change "Firefox Aurora" or similar into "Aurora".
+    if (name.contains("Aurora")) {
+        name = "Aurora";
+    } else if (name.contains("Beta")) {
+        name = "Beta";
+    } else if (name.contains("Nightly")) {
+        name = "Nightly";
+    }
+    return context.getResources().getString(R.string.sync_default_client_name, name, android.os.Build.MODEL);
+  }
+}