1 files changed, 255 insertions, 0 deletions
diff --git a/mobile/android/services/src/main/java/org/mozilla/gecko/browserid/DSACryptoImplementation.java b/mobile/android/services/src/main/java/org/mozilla/gecko/browserid/DSACryptoImplementation.java
new file mode 100644
index 000000000..a04a89c8e
--- /dev/null
+++ b/mobile/android/services/src/main/java/org/mozilla/gecko/browserid/DSACryptoImplementation.java
@@ -0,0 +1,255 @@
+/* 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.browserid;
+
+import android.annotation.SuppressLint;
+
+import org.mozilla.gecko.background.common.log.Logger;
+import org.mozilla.gecko.sync.ExtendedJSONObject;
+import org.mozilla.gecko.sync.NonObjectJSONException;
+import org.mozilla.gecko.sync.Utils;
+import org.mozilla.gecko.util.PRNGFixes;
+
+import java.math.BigInteger;
+import java.security.GeneralSecurityException;
+import java.security.KeyFactory;
+import java.security.KeyPair;
+import java.security.KeyPairGenerator;
+import java.security.NoSuchAlgorithmException;
+import java.security.Signature;
+import java.security.interfaces.DSAParams;
+import java.security.interfaces.DSAPrivateKey;
+import java.security.interfaces.DSAPublicKey;
+import java.security.spec.DSAPrivateKeySpec;
+import java.security.spec.DSAPublicKeySpec;
+import java.security.spec.InvalidKeySpecException;
+import java.security.spec.KeySpec;
+
+public class DSACryptoImplementation {
+  private static final String LOG_TAG = DSACryptoImplementation.class.getSimpleName();
+
+  public static final String SIGNATURE_ALGORITHM = "SHA1withDSA";
+  public static final int SIGNATURE_LENGTH_BYTES = 40; // DSA signatures are always 40 bytes long.
+
+  /**
+   * Parameters are serialized as hex strings. Hex-versus-decimal was
+   * reverse-engineered from what the Persona public verifier accepted. We
+   * expect to follow the JOSE/JWT spec as it solidifies, and that will probably
+   * mean unifying this base.
+   */
+  protected static final int SERIALIZATION_BASE = 16;
+
+  protected static class DSAVerifyingPublicKey implements VerifyingPublicKey {
+    protected final DSAPublicKey publicKey;
+
+    public DSAVerifyingPublicKey(DSAPublicKey publicKey) {
+      this.publicKey = publicKey;
+    }
+
+    /**
+     * Serialize to a JSON object.
+     * <p>
+     * Parameters are serialized as hex strings. Hex-versus-decimal was
+     * reverse-engineered from what the Persona public verifier accepted.
+     */
+    @Override
+    public ExtendedJSONObject toJSONObject() {
+      DSAParams params = publicKey.getParams();
+      ExtendedJSONObject o = new ExtendedJSONObject();
+      o.put("algorithm", "DS");
+      o.put("y", publicKey.getY().toString(SERIALIZATION_BASE));
+      o.put("g", params.getG().toString(SERIALIZATION_BASE));
+      o.put("p", params.getP().toString(SERIALIZATION_BASE));
+      o.put("q", params.getQ().toString(SERIALIZATION_BASE));
+      return o;
+    }
+
+    @Override
+    public boolean verifyMessage(byte[] bytes, byte[] signature)
+        throws GeneralSecurityException {
+      if (bytes == null) {
+        throw new IllegalArgumentException("bytes must not be null");
+      }
+      if (signature == null) {
+        throw new IllegalArgumentException("signature must not be null");
+      }
+      if (signature.length != SIGNATURE_LENGTH_BYTES) {
+        return false;
+      }
+      byte[] first = new byte[signature.length / 2];
+      byte[] second = new byte[signature.length / 2];
+      System.arraycopy(signature, 0, first, 0, first.length);
+      System.arraycopy(signature, first.length, second, 0, second.length);
+      BigInteger r = new BigInteger(Utils.byte2Hex(first), 16);
+      BigInteger s = new BigInteger(Utils.byte2Hex(second), 16);
+      // This is awful, but encoding an extra 0 byte works better on devices.
+      byte[] encoded = ASNUtils.encodeTwoArraysToASN1(
+          Utils.hex2Byte(r.toString(16), 1 + SIGNATURE_LENGTH_BYTES / 2),
+          Utils.hex2Byte(s.toString(16), 1 + SIGNATURE_LENGTH_BYTES / 2));
+
+      final Signature signer = Signature.getInstance(SIGNATURE_ALGORITHM);
+      signer.initVerify(publicKey);
+      signer.update(bytes);
+      return signer.verify(encoded);
+    }
+  }
+
+  protected static class DSASigningPrivateKey implements SigningPrivateKey {
+    protected final DSAPrivateKey privateKey;
+
+    public DSASigningPrivateKey(DSAPrivateKey privateKey) {
+      this.privateKey = privateKey;
+    }
+
+    @Override
+    public String getAlgorithm() {
+      return "DS" + (privateKey.getParams().getP().bitLength() + 7)/8;
+    }
+
+    /**
+     * Serialize to a JSON object.
+     * <p>
+     * Parameters are serialized as decimal strings. Hex-versus-decimal was
+     * reverse-engineered from what the Persona public verifier accepted.
+     */
+    @Override
+    public ExtendedJSONObject toJSONObject() {
+      DSAParams params = privateKey.getParams();
+      ExtendedJSONObject o = new ExtendedJSONObject();
+      o.put("algorithm", "DS");
+      o.put("x", privateKey.getX().toString(SERIALIZATION_BASE));
+      o.put("g", params.getG().toString(SERIALIZATION_BASE));
+      o.put("p", params.getP().toString(SERIALIZATION_BASE));
+      o.put("q", params.getQ().toString(SERIALIZATION_BASE));
+      return o;
+    }
+
+    @SuppressLint("TrulyRandom")
+    @Override
+    public byte[] signMessage(byte[] bytes)
+        throws GeneralSecurityException {
+      if (bytes == null) {
+        throw new IllegalArgumentException("bytes must not be null");
+      }
+
+      try {
+        PRNGFixes.apply();
+      } catch (Exception e) {
+        // Not much to be done here: it was weak before, and we couldn't patch it, so it's weak now.  Not worth aborting.
+        Logger.error(LOG_TAG, "Got exception applying PRNGFixes!  Cryptographic data produced on this device may be weak.  Ignoring.", e);
+      }
+
+      final Signature signer = Signature.getInstance(SIGNATURE_ALGORITHM);
+      signer.initSign(privateKey);
+      signer.update(bytes);
+      final byte[] signature = signer.sign();
+
+      final byte[][] arrays = ASNUtils.decodeTwoArraysFromASN1(signature);
+      BigInteger r = new BigInteger(arrays[0]);
+      BigInteger s = new BigInteger(arrays[1]);
+      // This is awful, but signatures are always 40 bytes long.
+      byte[] decoded = Utils.concatAll(
+          Utils.hex2Byte(r.toString(16), SIGNATURE_LENGTH_BYTES / 2),
+          Utils.hex2Byte(s.toString(16), SIGNATURE_LENGTH_BYTES / 2));
+      return decoded;
+    }
+  }
+
+  public static BrowserIDKeyPair generateKeyPair(int keysize)
+      throws NoSuchAlgorithmException {
+    final KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("DSA");
+    keyPairGenerator.initialize(keysize);
+    final KeyPair keyPair = keyPairGenerator.generateKeyPair();
+    DSAPrivateKey privateKey = (DSAPrivateKey) keyPair.getPrivate();
+    DSAPublicKey publicKey = (DSAPublicKey) keyPair.getPublic();
+    return new BrowserIDKeyPair(new DSASigningPrivateKey(privateKey), new DSAVerifyingPublicKey(publicKey));
+  }
+
+  public static SigningPrivateKey createPrivateKey(BigInteger x, BigInteger p, BigInteger q, BigInteger g) throws NoSuchAlgorithmException, InvalidKeySpecException {
+    if (x == null) {
+      throw new IllegalArgumentException("x must not be null");
+    }
+    if (p == null) {
+      throw new IllegalArgumentException("p must not be null");
+    }
+    if (q == null) {
+      throw new IllegalArgumentException("q must not be null");
+    }
+    if (g == null) {
+      throw new IllegalArgumentException("g must not be null");
+    }
+    KeySpec keySpec = new DSAPrivateKeySpec(x, p, q, g);
+    KeyFactory keyFactory = KeyFactory.getInstance("DSA");
+    DSAPrivateKey privateKey = (DSAPrivateKey) keyFactory.generatePrivate(keySpec);
+    return new DSASigningPrivateKey(privateKey);
+  }
+
+  public static VerifyingPublicKey createPublicKey(BigInteger y, BigInteger p, BigInteger q, BigInteger g) throws NoSuchAlgorithmException, InvalidKeySpecException {
+    if (y == null) {
+      throw new IllegalArgumentException("n must not be null");
+    }
+    if (p == null) {
+      throw new IllegalArgumentException("p must not be null");
+    }
+    if (q == null) {
+      throw new IllegalArgumentException("q must not be null");
+    }
+    if (g == null) {
+      throw new IllegalArgumentException("g must not be null");
+    }
+    KeySpec keySpec = new DSAPublicKeySpec(y, p, q, g);
+    KeyFactory keyFactory = KeyFactory.getInstance("DSA");
+    DSAPublicKey publicKey = (DSAPublicKey) keyFactory.generatePublic(keySpec);
+    return new DSAVerifyingPublicKey(publicKey);
+  }
+
+  public static SigningPrivateKey createPrivateKey(ExtendedJSONObject o) throws InvalidKeySpecException, NoSuchAlgorithmException {
+    String algorithm = o.getString("algorithm");
+    if (!"DS".equals(algorithm)) {
+      throw new InvalidKeySpecException("algorithm must equal DS, was " + algorithm);
+    }
+    try {
+      BigInteger x = new BigInteger(o.getString("x"), SERIALIZATION_BASE);
+      BigInteger p = new BigInteger(o.getString("p"), SERIALIZATION_BASE);
+      BigInteger q = new BigInteger(o.getString("q"), SERIALIZATION_BASE);
+      BigInteger g = new BigInteger(o.getString("g"), SERIALIZATION_BASE);
+      return createPrivateKey(x, p, q, g);
+    } catch (NullPointerException | NumberFormatException e) {
+      throw new InvalidKeySpecException("x, p, q, and g must be integers encoded as strings, base " + SERIALIZATION_BASE);
+    }
+  }
+
+  public static VerifyingPublicKey createPublicKey(ExtendedJSONObject o) throws InvalidKeySpecException, NoSuchAlgorithmException {
+    String algorithm = o.getString("algorithm");
+    if (!"DS".equals(algorithm)) {
+      throw new InvalidKeySpecException("algorithm must equal DS, was " + algorithm);
+    }
+    try {
+      BigInteger y = new BigInteger(o.getString("y"), SERIALIZATION_BASE);
+      BigInteger p = new BigInteger(o.getString("p"), SERIALIZATION_BASE);
+      BigInteger q = new BigInteger(o.getString("q"), SERIALIZATION_BASE);
+      BigInteger g = new BigInteger(o.getString("g"), SERIALIZATION_BASE);
+      return createPublicKey(y, p, q, g);
+    } catch (NullPointerException | NumberFormatException e) {
+      throw new InvalidKeySpecException("y, p, q, and g must be integers encoded as strings, base " + SERIALIZATION_BASE);
+    }
+  }
+
+  public static BrowserIDKeyPair fromJSONObject(ExtendedJSONObject o) throws InvalidKeySpecException, NoSuchAlgorithmException {
+    try {
+      ExtendedJSONObject privateKey = o.getObject(BrowserIDKeyPair.JSON_KEY_PRIVATEKEY);
+      ExtendedJSONObject publicKey = o.getObject(BrowserIDKeyPair.JSON_KEY_PUBLICKEY);
+      if (privateKey == null) {
+        throw new InvalidKeySpecException("privateKey must not be null");
+      }
+      if (publicKey == null) {
+        throw new InvalidKeySpecException("publicKey must not be null");
+      }
+      return new BrowserIDKeyPair(createPrivateKey(privateKey), createPublicKey(publicKey));
+    } catch (NonObjectJSONException e) {
+      throw new InvalidKeySpecException("privateKey and publicKey must be JSON objects");
+    }
+  }
+}