Implement revocation of subkeys

pgpainless-core/src/main/java/org/pgpainless/key/modification/KeyRingEditor.java

@@ -55,6 +55,7 @@ import org.pgpainless.key.protection.PasswordBasedSecretKeyRingProtector;
 import org.pgpainless.key.protection.SecretKeyRingProtector;
 import org.pgpainless.key.protection.UnprotectedKeysProtector;
 import org.pgpainless.key.protection.passphrase_provider.SolitaryPassphraseProvider;
+import org.pgpainless.key.util.KeyRingUtils;
 import org.pgpainless.key.util.OpenPgpKeyAttributeUtil;
 import org.pgpainless.util.NotYetImplementedException;
 import org.pgpainless.util.Passphrase;
@@ -274,8 +275,32 @@ public class KeyRingEditor implements KeyRingEditorInterface {
     }
 
     @Override
-    public KeyRingEditorInterface revokeSubKey(OpenPgpV4Fingerprint fingerprint, SecretKeyRingProtector protector) {
+    public KeyRingEditorInterface revokeSubKey(OpenPgpV4Fingerprint fingerprint, SecretKeyRingProtector protector)
-        throw new NotYetImplementedException();
+            throws PGPException {
+        PGPSecretKey primaryKey = secretKeyRing.getSecretKey();
+        PGPPrivateKey privateKey = primaryKey.extractPrivateKey(protector.getDecryptor(primaryKey.getKeyID()));
+
+        PGPPublicKey revokeeSubKey = secretKeyRing.getPublicKey(fingerprint.getKeyId());
+        if (revokeeSubKey == null) {
+            throw new NoSuchElementException("No subkey with fingerprint " + fingerprint + " found.");
+        }
+
+        PGPContentSignerBuilder contentSignerBuilder = new BcPGPContentSignerBuilder(
+                primaryKey.getPublicKey().getAlgorithm(),
+                defaultDigestHashAlgorithm.getAlgorithmId());
+        PGPSignatureGenerator signatureGenerator = new PGPSignatureGenerator(contentSignerBuilder);
+        signatureGenerator.init(SignatureType.SUBKEY_REVOCATION.getCode(), privateKey);
+
+        // Generate revocation
+        PGPSignature subKeyRevocation = signatureGenerator.generateCertification(primaryKey.getPublicKey(), revokeeSubKey);
+        revokeeSubKey = PGPPublicKey.addCertification(revokeeSubKey, subKeyRevocation);
+
+        // Inject revoked public key into key ring
+        PGPPublicKeyRing publicKeyRing = KeyRingUtils.publicKeyRingFrom(secretKeyRing);
+        publicKeyRing = PGPPublicKeyRing.insertPublicKey(publicKeyRing, revokeeSubKey);
+        secretKeyRing = PGPSecretKeyRing.replacePublicKeys(secretKeyRing, publicKeyRing);
+
+        return this;
     }
 
     @Override

pgpainless-core/src/main/java/org/pgpainless/key/modification/KeyRingEditorInterface.java

@@ -102,7 +102,7 @@ public interface KeyRingEditorInterface {
      * @param fingerprint fingerprint of the subkey to be revoked
      * @return the builder
      */
-    KeyRingEditorInterface revokeSubKey(OpenPgpV4Fingerprint fingerprint, SecretKeyRingProtector secretKeyRingProtector);
+    KeyRingEditorInterface revokeSubKey(OpenPgpV4Fingerprint fingerprint, SecretKeyRingProtector secretKeyRingProtector) throws PGPException;
 
     /**
      * Revoke the subkey binding signature of a subkey.

pgpainless-core/src/main/java/org/pgpainless/key/util/KeyRingUtils.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2020 Paul Schaub.
+ *
+ * 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 org.pgpainless.key.util;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+import org.bouncycastle.openpgp.PGPPublicKey;
+import org.bouncycastle.openpgp.PGPPublicKeyRing;
+import org.bouncycastle.openpgp.PGPSecretKeyRing;
+
+public class KeyRingUtils {
+
+    public static PGPPublicKeyRing publicKeyRingFrom(PGPSecretKeyRing secretKeys) {
+        List<PGPPublicKey> publicKeyList = new ArrayList<>();
+        Iterator<PGPPublicKey> publicKeyIterator = secretKeys.getPublicKeys();
+        while (publicKeyIterator.hasNext()) {
+            publicKeyList.add(publicKeyIterator.next());
+        }
+        PGPPublicKeyRing publicKeyRing = new PGPPublicKeyRing(publicKeyList);
+        return publicKeyRing;
+    }
+}

pgpainless-core/src/test/java/org/pgpainless/key/modification/RevokeSubKeyTest.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2020 Paul Schaub.
+ *
+ * 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 org.pgpainless.key.modification;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.io.IOException;
+import java.util.Iterator;
+
+import org.bouncycastle.openpgp.PGPException;
+import org.bouncycastle.openpgp.PGPSecretKey;
+import org.bouncycastle.openpgp.PGPSecretKeyRing;
+import org.junit.Test;
+import org.pgpainless.PGPainless;
+import org.pgpainless.key.OpenPgpV4Fingerprint;
+import org.pgpainless.key.TestKeys;
+import org.pgpainless.key.protection.PasswordBasedSecretKeyRingProtector;
+import org.pgpainless.key.protection.SecretKeyRingProtector;
+import org.pgpainless.util.Passphrase;
+
+public class RevokeSubKeyTest {
+
+    @Test
+    public void revokeSukeyTest() throws IOException, PGPException {
+        PGPSecretKeyRing secretKeys = TestKeys.getCryptieSecretKeyRing();
+
+        Iterator<PGPSecretKey> keysIterator = secretKeys.iterator();
+        PGPSecretKey primaryKey = keysIterator.next();
+        PGPSecretKey subKey = keysIterator.next();
+
+        assertFalse(subKey.getPublicKey().hasRevocation());
+
+        SecretKeyRingProtector protector = PasswordBasedSecretKeyRingProtector
+                .forKey(secretKeys, Passphrase.fromPassword("password123"));
+
+        secretKeys = PGPainless.modifyKeyRing(secretKeys)
+                .revokeSubKey(new OpenPgpV4Fingerprint(subKey), protector)
+                .done();
+        keysIterator = secretKeys.iterator();
+        primaryKey = keysIterator.next();
+        subKey = keysIterator.next();
+
+        assertTrue(subKey.getPublicKey().hasRevocation());
+    }
+}