Make KeyType compatible with Android Keystore (hierynomus#586)

* Make KeyType compatible with Android Keystore

Android Keystore private keys do not implement PrivateKey since the
raw key material is not available to applications.

With this commit, sshj's KeyType correctly detects the algorithm
associated with Android Keystore keys, which makes them usable for SSH
authentication.

* Extract RSA, DSA, ECDSA and EC into constants

* Fix license lint issue

Co-authored-by: Jeroen van Erp <jeroen@hierynomus.com>

Author: FabianHenneke

src/main/java/com/hierynomus/sshj/common/KeyAlgorithm.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright (C)2009 - SSHJ Contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.hierynomus.sshj.common;
+
+public class KeyAlgorithm {
+
+    public static final String RSA = "RSA";
+    public static final String DSA = "DSA";
+
+    /** Elliptic curve signature key algorithm for use with BouncyCastle **/
+    public static final String ECDSA = "ECDSA";
+
+    /** General elliptic curve algorithm identifier for use with BouncyCastle **/
+    public static final String EC_BC = "EC";
+
+    /** General elliptic curve algorithm identifier for use with the Android Keystore **/
+    public static final String EC_KEYSTORE = "EC";
+}

src/main/java/com/hierynomus/sshj/userauth/keyprovider/OpenSSHKeyV1KeyFile.java

@@ -15,6 +15,7 @@
  */
 package com.hierynomus.sshj.userauth.keyprovider;
 
+import com.hierynomus.sshj.common.KeyAlgorithm;
 import com.hierynomus.sshj.common.KeyDecryptionFailedException;
 import com.hierynomus.sshj.transport.cipher.BlockCiphers;
 import net.i2p.crypto.eddsa.EdDSAPrivateKey;
@@ -216,7 +217,7 @@ private KeyPair readUnencrypted(final PlainBuffer keyBuffer, final PublicKey pub
                 keyBuffer.readMPInt(); // iqmp (q^-1 mod p)
                 keyBuffer.readMPInt(); // p (Prime 1)
                 keyBuffer.readMPInt(); // q (Prime 2)
-                kp = new KeyPair(publicKey, SecurityUtils.getKeyFactory("RSA").generatePrivate(new RSAPrivateKeySpec(n, d)));
+                kp = new KeyPair(publicKey, SecurityUtils.getKeyFactory(KeyAlgorithm.RSA).generatePrivate(new RSAPrivateKeySpec(n, d)));
                 break;
             case ECDSA256:
                 kp = new KeyPair(publicKey, createECDSAPrivateKey(kt, keyBuffer, "P-256"));
@@ -248,7 +249,7 @@ private PrivateKey createECDSAPrivateKey(KeyType kt, PlainBuffer buffer, String
         X9ECParameters ecParams = NISTNamedCurves.getByName(name);
         ECNamedCurveSpec ecCurveSpec = new ECNamedCurveSpec(name, ecParams.getCurve(), ecParams.getG(), ecParams.getN());
         ECPrivateKeySpec pks = new ECPrivateKeySpec(s, ecCurveSpec);
-        return SecurityUtils.getKeyFactory("ECDSA").generatePrivate(pks);
+        return SecurityUtils.getKeyFactory(KeyAlgorithm.ECDSA).generatePrivate(pks);
 
     }
 }

src/main/java/net/schmizz/sshj/common/ECDSAVariationsAdapter.java

@@ -15,6 +15,7 @@
  */
 package net.schmizz.sshj.common;
 
+import com.hierynomus.sshj.common.KeyAlgorithm;
 import com.hierynomus.sshj.secg.SecgUtils;
 import org.bouncycastle.asn1.nist.NISTNamedCurves;
 import org.bouncycastle.asn1.x9.X9ECParameters;
@@ -87,7 +88,7 @@ static PublicKey readPubKeyFromBuffer(Buffer<?> buf, String variation) throws Ge
             ECPoint p = new ECPoint(bigX, bigY);
             ECPublicKeySpec publicKeySpec = new ECPublicKeySpec(p, ecCurveSpec);
 
-            KeyFactory keyFactory = KeyFactory.getInstance("ECDSA");
+            KeyFactory keyFactory = KeyFactory.getInstance(KeyAlgorithm.ECDSA);
             return keyFactory.generatePublic(publicKeySpec);
         } catch (Exception ex) {
             throw new GeneralSecurityException(ex);
@@ -103,7 +104,7 @@ static void writePubKeyContentsIntoBuffer(PublicKey pk, Buffer<?> buf) {
     }
 
     static boolean isECKeyWithFieldSize(Key key, int fieldSize) {
-        return "ECDSA".equals(key.getAlgorithm())
+        return (KeyAlgorithm.ECDSA.equals(key.getAlgorithm()) || KeyAlgorithm.EC_KEYSTORE.equals(key.getAlgorithm()))
                 && fieldSizeFromKey((ECKey) key) == fieldSize;
     }
 

src/main/java/net/schmizz/sshj/common/KeyType.java

@@ -15,6 +15,7 @@
  */
 package net.schmizz.sshj.common;
 
+import com.hierynomus.sshj.common.KeyAlgorithm;
 import com.hierynomus.sshj.signature.Ed25519PublicKey;
 import com.hierynomus.sshj.userauth.certificate.Certificate;
 import net.i2p.crypto.eddsa.EdDSAPublicKey;
@@ -30,9 +31,7 @@
 import java.security.Key;
 import java.security.KeyFactory;
 import java.security.PublicKey;
-import java.security.interfaces.DSAPrivateKey;
 import java.security.interfaces.DSAPublicKey;
-import java.security.interfaces.RSAPrivateKey;
 import java.security.interfaces.RSAPublicKey;
 import java.security.spec.DSAPublicKeySpec;
 import java.security.spec.RSAPublicKeySpec;
@@ -53,7 +52,7 @@ public PublicKey readPubKeyFromBuffer(Buffer<?> buf)
             } catch (Buffer.BufferException be) {
                 throw new GeneralSecurityException(be);
             }
-            final KeyFactory keyFactory = SecurityUtils.getKeyFactory("RSA");
+            final KeyFactory keyFactory = SecurityUtils.getKeyFactory(KeyAlgorithm.RSA);
             return keyFactory.generatePublic(new RSAPublicKeySpec(n, e));
         }
 
@@ -66,7 +65,7 @@ protected void writePubKeyContentsIntoBuffer(PublicKey pk, Buffer<?> buf) {
 
         @Override
         protected boolean isMyType(Key key) {
-            return (key instanceof RSAPublicKey || key instanceof RSAPrivateKey);
+            return KeyAlgorithm.RSA.equals(key.getAlgorithm());
         }
     },
 
@@ -84,7 +83,7 @@ public PublicKey readPubKeyFromBuffer(Buffer<?> buf)
             } catch (Buffer.BufferException be) {
                 throw new GeneralSecurityException(be);
             }
-            final KeyFactory keyFactory = SecurityUtils.getKeyFactory("DSA");
+            final KeyFactory keyFactory = SecurityUtils.getKeyFactory(KeyAlgorithm.DSA);
             return keyFactory.generatePublic(new DSAPublicKeySpec(y, p, q, g));
         }
 
@@ -99,7 +98,7 @@ protected void writePubKeyContentsIntoBuffer(PublicKey pk, Buffer<?> buf) {
 
         @Override
         protected boolean isMyType(Key key) {
-            return (key instanceof DSAPublicKey || key instanceof DSAPrivateKey);
+            return KeyAlgorithm.DSA.equals(key.getAlgorithm());
         }
 
     },

src/main/java/net/schmizz/sshj/transport/kex/Curve25519DH.java

@@ -15,6 +15,7 @@
  */
 package net.schmizz.sshj.transport.kex;
 
+import com.hierynomus.sshj.common.KeyAlgorithm;
 import net.schmizz.sshj.common.Factory;
 import net.schmizz.sshj.transport.random.Random;
 import org.bouncycastle.asn1.x9.X9ECParameters;
@@ -31,7 +32,7 @@ public class Curve25519DH extends DHBase {
     private byte[] secretKey;
 
     public Curve25519DH() {
-        super("ECDSA", "ECDH");
+        super(KeyAlgorithm.ECDSA, "ECDH");
     }
 
     @Override

src/main/java/net/schmizz/sshj/transport/kex/ECDH.java

@@ -15,6 +15,7 @@
  */
 package net.schmizz.sshj.transport.kex;
 
+import com.hierynomus.sshj.common.KeyAlgorithm;
 import net.schmizz.sshj.common.Factory;
 import net.schmizz.sshj.common.SecurityUtils;
 import net.schmizz.sshj.transport.random.Random;
@@ -54,7 +55,7 @@ public void init(AlgorithmParameterSpec params, Factory<Random> randomFactory) t
 
     @Override
     public void computeK(byte[] f) throws GeneralSecurityException {
-        KeyFactory keyFactory = SecurityUtils.getKeyFactory("EC");
+        KeyFactory keyFactory = SecurityUtils.getKeyFactory(KeyAlgorithm.EC_BC);
         ECPublicKeySpec keySpec = new ECPublicKeySpec(getDecoded(f, ecParameterSpec.getCurve()), ecParameterSpec);
         PublicKey yourPubKey = keyFactory.generatePublic(keySpec);
         agreement.doPhase(yourPubKey, true);

src/main/java/net/schmizz/sshj/transport/verification/OpenSSHKnownHosts.java

@@ -15,6 +15,7 @@
  */
 package net.schmizz.sshj.transport.verification;
 
+import com.hierynomus.sshj.common.KeyAlgorithm;
 import com.hierynomus.sshj.transport.verification.KnownHostMatchers;
 import net.schmizz.sshj.common.*;
 import org.slf4j.Logger;
@@ -239,7 +240,7 @@ public KnownHostEntry parseEntry(String line)
                 final BigInteger e = new BigInteger(split[i++]);
                 final BigInteger n = new BigInteger(split[i++]);
                 try {
-                    final KeyFactory keyFactory = SecurityUtils.getKeyFactory("RSA");
+                    final KeyFactory keyFactory = SecurityUtils.getKeyFactory(KeyAlgorithm.RSA);
                     key = keyFactory.generatePublic(new RSAPublicKeySpec(n, e));
                 } catch (Exception ex) {
                     log.error("Error reading entry `{}`, could not create key", line, ex);

src/main/java/net/schmizz/sshj/userauth/keyprovider/PKCS5KeyFile.java

@@ -15,6 +15,7 @@
  */
 package net.schmizz.sshj.userauth.keyprovider;
 
+import com.hierynomus.sshj.common.KeyAlgorithm;
 import com.hierynomus.sshj.transport.cipher.BlockCiphers;
 import net.schmizz.sshj.common.Base64;
 import net.schmizz.sshj.common.ByteArrayUtils;
@@ -140,7 +141,7 @@ protected KeyPair readKeyPair()
             ASN1Data asn = new ASN1Data(data = decrypt(Base64.decode(sb.toString()), cipher, iv));
             switch (type) {
                 case RSA: {
-                    KeyFactory factory = KeyFactory.getInstance("RSA");
+                    KeyFactory factory = KeyFactory.getInstance(KeyAlgorithm.RSA);
                     asn.readNext();
                     BigInteger modulus = asn.readNext();
                     BigInteger pubExp = asn.readNext();
@@ -150,7 +151,7 @@ protected KeyPair readKeyPair()
                     return new KeyPair(pubKey, prvKey);
                 }
                 case DSA: {
-                    KeyFactory factory = KeyFactory.getInstance("DSA");
+                    KeyFactory factory = KeyFactory.getInstance(KeyAlgorithm.DSA);
                     asn.readNext();
                     BigInteger p = asn.readNext();
                     BigInteger q = asn.readNext();

src/main/java/net/schmizz/sshj/userauth/keyprovider/PuTTYKeyFile.java

@@ -15,6 +15,7 @@
  */
 package net.schmizz.sshj.userauth.keyprovider;
 
+import com.hierynomus.sshj.common.KeyAlgorithm;
 import net.schmizz.sshj.common.Base64;
 import net.schmizz.sshj.common.KeyType;
 import net.schmizz.sshj.userauth.password.PasswordUtils;
@@ -114,7 +115,7 @@ protected KeyPair readKeyPair() throws IOException {
 
             final KeyFactory factory;
             try {
-                factory = KeyFactory.getInstance("RSA");
+                factory = KeyFactory.getInstance(KeyAlgorithm.RSA);
             } catch (NoSuchAlgorithmException s) {
                 throw new IOException(s.getMessage(), s);
             }
@@ -141,7 +142,7 @@ protected KeyPair readKeyPair() throws IOException {
 
             final KeyFactory factory;
             try {
-                factory = KeyFactory.getInstance("DSA");
+                factory = KeyFactory.getInstance(KeyAlgorithm.DSA);
             } catch (NoSuchAlgorithmException s) {
                 throw new IOException(s.getMessage(), s);
             }

src/test/groovy/net/schmizz/sshj/signature/SignatureDSASpec.groovy

@@ -30,6 +30,7 @@
 */
 package net.schmizz.sshj.signature
 
+import com.hierynomus.sshj.common.KeyAlgorithm
 import spock.lang.Unroll;
 
 import java.math.BigInteger;
@@ -47,7 +48,7 @@ import spock.lang.Specification
 
 class SignatureDSASpec extends Specification {
 
-    def keyFactory = KeyFactory.getInstance("DSA")
+    def keyFactory = KeyFactory.getInstance(KeyAlgorithm.DSA)
 
     private PublicKey createPublicKey(final byte[] y, final byte[] p, final byte[] q, final byte[] g) throws Exception {
         final BigInteger publicKey = new BigInteger(y);