Fix checkstyle issues

pgpainless-core/src/main/java/org/pgpainless/decryption_verification/MessageMetadata.java

@@ -90,7 +90,7 @@ public class MessageMetadata {
         return (LiteralData) nested;
     }
 
-    public static abstract class Layer {
+    public abstract static class Layer {
         protected final List<SignatureVerification> verifiedSignatures = new ArrayList<>();
         protected final List<SignatureVerification.Failure> failedSignatures = new ArrayList<>();
         protected Nested child;
@@ -198,11 +198,11 @@ public class MessageMetadata {
     }
 
 
-    private static abstract class LayerIterator<O> implements Iterator<O> {
+    private abstract static class LayerIterator<O> implements Iterator<O> {
         private Nested current;
         Layer last = null;
 
-        public LayerIterator(Message message) {
+        LayerIterator(Message message) {
             super();
             this.current = message.child;
             if (matches(current)) {

pgpainless-core/src/main/java/org/pgpainless/decryption_verification/OpenPgpMessageInputStream.java

@@ -50,6 +50,8 @@ import org.pgpainless.key.protection.UnlockSecretKey;
 import org.pgpainless.signature.SignatureUtils;
 import org.pgpainless.util.Passphrase;
 import org.pgpainless.util.Tuple;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
@@ -60,6 +62,8 @@ import java.util.List;
 
 public class OpenPgpMessageInputStream extends InputStream {
 
+    private static final Logger LOGGER = LoggerFactory.getLogger(OpenPgpMessageInputStream.class);
+
     protected final PDA automaton = new PDA();
     protected final ConsumerOptions options;
     protected final OpenPgpMetadata.Builder resultBuilder;
@@ -519,7 +523,7 @@ public class OpenPgpMessageInputStream extends InputStream {
         private final PGPOnePassSignatureList list;
         private final List<Boolean> encapsulating;
 
-        public PGPOnePassSignatureListWrapper(PGPOnePassSignatureList signatures, List<Boolean> encapsulating) {
+        PGPOnePassSignatureListWrapper(PGPOnePassSignatureList signatures, List<Boolean> encapsulating) {
             this.list = signatures;
             this.encapsulating = encapsulating;
         }
@@ -529,7 +533,7 @@ public class OpenPgpMessageInputStream extends InputStream {
         }
     }
 
-    private static class Signatures {
+    private static final class Signatures {
         final ConsumerOptions options;
         List<PGPSignature> detachedSignatures = new ArrayList<>();
         List<PGPSignature> prependedSignatures = new ArrayList<>();
@@ -551,7 +555,6 @@ public class OpenPgpMessageInputStream extends InputStream {
         }
 
         void addPrependedSignatures(PGPSignatureList signatures) {
-            System.out.println("Adding " + signatures.size() + " prepended Signatures");
             for (PGPSignature signature : signatures) {
                 long keyId = SignatureUtils.determineIssuerKeyId(signature);
                 PGPPublicKeyRing certificate = findCertificate(keyId);
@@ -561,7 +564,6 @@ public class OpenPgpMessageInputStream extends InputStream {
         }
 
         void addOnePassSignatures(PGPOnePassSignatureListWrapper signatures) {
-            System.out.println("Adding " + signatures.size() + " OPSs");
             for (PGPOnePassSignature ops : signatures.list) {
                 PGPPublicKeyRing certificate = findCertificate(ops.getKeyID());
                 initialize(ops, certificate);
@@ -570,7 +572,6 @@ public class OpenPgpMessageInputStream extends InputStream {
         }
 
         void addOnePassCorrespondingSignatures(PGPSignatureList signatures) {
-            System.out.println("Adding " + signatures.size() + " Corresponding Signatures");
             for (PGPSignature signature : signatures) {
                 correspondingSignatures.add(signature);
             }
@@ -631,9 +632,9 @@ public class OpenPgpMessageInputStream extends InputStream {
                 try {
                     verified = detached.verify();
                 } catch (PGPException e) {
-                    System.out.println(e.getMessage());
+                    LOGGER.debug("Cannot verify detached signature.", e);
                 }
-                System.out.println("Detached Signature by " + Long.toHexString(detached.getKeyID()) + " is " + (verified ? "verified" : "unverified"));
+                LOGGER.debug("Detached Signature by " + Long.toHexString(detached.getKeyID()) + " is " + (verified ? "verified" : "unverified"));
             }
 
             for (PGPSignature prepended : prependedSignatures) {
@@ -641,9 +642,9 @@ public class OpenPgpMessageInputStream extends InputStream {
                 try {
                     verified = prepended.verify();
                 } catch (PGPException e) {
-                    System.out.println(e.getMessage());
+                    LOGGER.debug("Cannot verify prepended signature.", e);
                 }
-                System.out.println("Prepended Signature by " + Long.toHexString(prepended.getKeyID()) + " is " + (verified ? "verified" : "unverified"));
+                LOGGER.debug("Prepended Signature by " + Long.toHexString(prepended.getKeyID()) + " is " + (verified ? "verified" : "unverified"));
             }
 
 
@@ -654,9 +655,9 @@ public class OpenPgpMessageInputStream extends InputStream {
                 try {
                     verified = ops.verify(signature);
                 } catch (PGPException e) {
-                    System.out.println(e.getMessage());
+                    LOGGER.debug("Cannot verify OPS signature.", e);
                 }
-                System.out.println("One-Pass-Signature by " + Long.toHexString(ops.getKeyID()) + " is " + (verified ? "verified" : "unverified"));
+                LOGGER.debug("One-Pass-Signature by " + Long.toHexString(ops.getKeyID()) + " is " + (verified ? "verified" : "unverified"));
             }
         }
     }

pgpainless-core/src/main/java/org/pgpainless/decryption_verification/automaton/InputAlphabet.java

@@ -1,3 +1,7 @@
+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
 package org.pgpainless.decryption_verification.automaton;
 
 import org.bouncycastle.openpgp.PGPCompressedData;

pgpainless-core/src/main/java/org/pgpainless/decryption_verification/automaton/PDA.java

@@ -1,3 +1,7 @@
+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
 package org.pgpainless.decryption_verification.automaton;
 
 import org.pgpainless.exception.MalformedOpenPgpMessageException;

pgpainless-core/src/main/java/org/pgpainless/decryption_verification/automaton/StackAlphabet.java

@@ -1,3 +1,7 @@
+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
 package org.pgpainless.decryption_verification.automaton;
 
 public enum StackAlphabet {

pgpainless-core/src/main/java/org/pgpainless/decryption_verification/automaton/package-info.java

@@ -0,0 +1,8 @@
+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+/**
+ * Pushdown Automaton to verify validity of packet sequences according to the OpenPGP Message format.
+ */
+package org.pgpainless.decryption_verification.automaton;

pgpainless-core/src/test/java/org/pgpainless/decryption_verification/OpenPgpMessageInputStreamTest.java

@@ -35,6 +35,7 @@ import org.junit.jupiter.params.provider.MethodSource;
 import org.pgpainless.PGPainless;
 import org.pgpainless.algorithm.CompressionAlgorithm;
 import org.pgpainless.algorithm.StreamEncoding;
+import org.pgpainless.algorithm.SymmetricKeyAlgorithm;
 import org.pgpainless.encryption_signing.EncryptionOptions;
 import org.pgpainless.encryption_signing.EncryptionResult;
 import org.pgpainless.encryption_signing.EncryptionStream;
@@ -118,7 +119,7 @@ public class OpenPgpMessageInputStreamTest {
             "=K9Zl\n" +
             "-----END PGP MESSAGE-----";
 
-    public static final String SIG_LIT = "" +
+    public static final String SIG_COMP_LIT = "" +
             "-----BEGIN PGP MESSAGE-----\n" +
             "Version: BCPG v1.71\n" +
             "\n" +
@@ -235,9 +236,9 @@ public class OpenPgpMessageInputStreamTest {
     }
 
     public static void genKey() throws PGPException, InvalidAlgorithmParameterException, NoSuchAlgorithmException, IOException {
-        System.out.println(PGPainless.asciiArmor(
+        PGPainless.asciiArmor(
-                PGPainless.generateKeyRing().modernKeyRing("Alice <alice@pgpainless.org>")
+                PGPainless.generateKeyRing().modernKeyRing("Alice <alice@pgpainless.org>"),
-        ));
+                System.out);
     }
 
     public static void genSIG_LIT() throws PGPException, IOException {
@@ -265,54 +266,46 @@ public class OpenPgpMessageInputStreamTest {
         armorOut.close();
 
         String armored = out.toString();
+        // CHECKSTYLE:OFF
         System.out.println(armored
                 .replace("-----BEGIN PGP SIGNATURE-----\n", "-----BEGIN PGP MESSAGE-----\n")
                 .replace("-----END PGP SIGNATURE-----", "-----END PGP MESSAGE-----"));
+        // CHECKSTYLE:ON
     }
 
     public static void genSENC_LIT() throws PGPException, IOException {
-        ByteArrayOutputStream out = new ByteArrayOutputStream();
         EncryptionStream enc = PGPainless.encryptAndOrSign()
-                .onOutputStream(out)
+                .onOutputStream(System.out)
                 .withOptions(ProducerOptions.encrypt(EncryptionOptions.get()
                                 .addPassphrase(Passphrase.fromPassword(PASSPHRASE)))
                         .overrideCompressionAlgorithm(CompressionAlgorithm.UNCOMPRESSED));
         enc.write(PLAINTEXT.getBytes(StandardCharsets.UTF_8));
         enc.close();
-
-        System.out.println(out);
     }
 
     public static void genPENC_COMP_LIT() throws IOException, PGPException {
         PGPSecretKeyRing secretKeys = PGPainless.readKeyRing().secretKeyRing(KEY);
         PGPPublicKeyRing cert = PGPainless.extractCertificate(secretKeys);
-
-        ByteArrayOutputStream out = new ByteArrayOutputStream();
         EncryptionStream enc = PGPainless.encryptAndOrSign()
-                .onOutputStream(out)
+                .onOutputStream(System.out)
                 .withOptions(ProducerOptions.encrypt(EncryptionOptions.get()
                                 .addRecipient(cert))
                         .overrideCompressionAlgorithm(CompressionAlgorithm.ZLIB));
 
         Streams.pipeAll(new ByteArrayInputStream(PLAINTEXT.getBytes(StandardCharsets.UTF_8)), enc);
         enc.close();
-
-        System.out.println(out);
     }
 
     public static void genOPS_LIT_SIG() throws PGPException, IOException {
         PGPSecretKeyRing secretKeys = PGPainless.readKeyRing().secretKeyRing(KEY);
 
-        ByteArrayOutputStream out = new ByteArrayOutputStream();
         EncryptionStream enc = PGPainless.encryptAndOrSign()
-                .onOutputStream(out)
+                .onOutputStream(System.out)
                 .withOptions(ProducerOptions.sign(SigningOptions.get()
                         .addSignature(SecretKeyRingProtector.unprotectedKeys(), secretKeys))
                         .overrideCompressionAlgorithm(CompressionAlgorithm.UNCOMPRESSED));
         Streams.pipeAll(new ByteArrayInputStream(PLAINTEXT.getBytes(StandardCharsets.UTF_8)), enc);
         enc.close();
-
-        System.out.println(out);
     }
 
     interface Processor {
@@ -322,7 +315,8 @@ public class OpenPgpMessageInputStreamTest {
     private static Stream<Arguments> provideMessageProcessors() {
         return Stream.of(
                 Arguments.of(Named.of("read(buf,off,len)", (Processor) OpenPgpMessageInputStreamTest::processReadBuffered)),
-                Arguments.of(Named.of("read()", (Processor) OpenPgpMessageInputStreamTest::processReadSequential)));
+                Arguments.of(Named.of("read()", (Processor) OpenPgpMessageInputStreamTest::processReadSequential))
+        );
     }
 
     @ParameterizedTest(name = "Process LIT using {0}")
@@ -349,7 +343,8 @@ public class OpenPgpMessageInputStreamTest {
 
     @ParameterizedTest(name = "Process COMP(LIT) using {0}")
     @MethodSource("provideMessageProcessors")
-    public void testProcessCOMP_LIT(Processor processor) throws PGPException, IOException {
+    public void testProcessCOMP_LIT(Processor processor)
+            throws PGPException, IOException {
         Tuple<String, MessageMetadata> result = processor.process(COMP_LIT, ConsumerOptions.get());
         String plain = result.getA();
         assertEquals(PLAINTEXT, plain);
@@ -366,7 +361,8 @@ public class OpenPgpMessageInputStreamTest {
 
     @ParameterizedTest(name = "Process COMP(COMP(LIT)) using {0}")
     @MethodSource("provideMessageProcessors")
-    public void testProcessCOMP_COMP_LIT(Processor processor) throws PGPException, IOException {
+    public void testProcessCOMP_COMP_LIT(Processor processor)
+            throws PGPException, IOException {
         Tuple<String, MessageMetadata> result = processor.process(COMP_COMP_LIT, ConsumerOptions.get());
         String plain = result.getA();
         assertEquals(PLAINTEXT, plain);
@@ -376,29 +372,37 @@ public class OpenPgpMessageInputStreamTest {
         assertEquals(CompressionAlgorithm.ZIP, compressionAlgorithms.next());
         assertEquals(CompressionAlgorithm.BZIP2, compressionAlgorithms.next());
         assertFalse(compressionAlgorithms.hasNext());
+        assertNull(metadata.getEncryptionAlgorithm());
     }
 
-    @ParameterizedTest(name = "Process SIG LIT using {0}")
+    @ParameterizedTest(name = "Process SIG COMP(LIT) using {0}")
     @MethodSource("provideMessageProcessors")
-    public void testProcessSIG_LIT(Processor processor) throws PGPException, IOException {
+    public void testProcessSIG_COMP_LIT(Processor processor) throws PGPException, IOException {
         PGPPublicKeyRing cert = PGPainless.extractCertificate(
                 PGPainless.readKeyRing().secretKeyRing(KEY));
 
-        Tuple<String, MessageMetadata> result = processor.process(SIG_LIT, ConsumerOptions.get()
+        Tuple<String, MessageMetadata> result = processor.process(SIG_COMP_LIT, ConsumerOptions.get()
                 .addVerificationCert(cert));
         String plain = result.getA();
         assertEquals(PLAINTEXT, plain);
+        MessageMetadata metadata = result.getB();
+        assertEquals(CompressionAlgorithm.ZIP, metadata.getCompressionAlgorithm());
+        assertNull(metadata.getEncryptionAlgorithm());
     }
 
     @ParameterizedTest(name = "Process SENC(LIT) using {0}")
     @MethodSource("provideMessageProcessors")
     public void testProcessSENC_LIT(Processor processor) throws PGPException, IOException {
-        Tuple<String, MessageMetadata> result = processor.process(SENC_LIT, ConsumerOptions.get().addDecryptionPassphrase(Passphrase.fromPassword(PASSPHRASE)));
+        Tuple<String, MessageMetadata> result = processor.process(SENC_LIT, ConsumerOptions.get()
+                .addDecryptionPassphrase(Passphrase.fromPassword(PASSPHRASE)));
         String plain = result.getA();
         assertEquals(PLAINTEXT, plain);
+        MessageMetadata metadata = result.getB();
+        assertNull(metadata.getCompressionAlgorithm());
+        assertEquals(SymmetricKeyAlgorithm.AES_256, metadata.getEncryptionAlgorithm());
     }
 
-    @ParameterizedTest(name = "Process PENC(LIT) using {0}")
+    @ParameterizedTest(name = "Process PENC(COMP(LIT)) using {0}")
     @MethodSource("provideMessageProcessors")
     public void testProcessPENC_COMP_LIT(Processor processor) throws IOException, PGPException {
         PGPSecretKeyRing secretKeys = PGPainless.readKeyRing().secretKeyRing(KEY);
@@ -406,6 +410,9 @@ public class OpenPgpMessageInputStreamTest {
                 .addDecryptionKey(secretKeys));
         String plain = result.getA();
         assertEquals(PLAINTEXT, plain);
+        MessageMetadata metadata = result.getB();
+        assertEquals(CompressionAlgorithm.ZLIB, metadata.getCompressionAlgorithm());
+        assertEquals(SymmetricKeyAlgorithm.AES_256, metadata.getEncryptionAlgorithm());
     }
 
     @ParameterizedTest(name = "Process OPS LIT SIG using {0}")
@@ -416,6 +423,9 @@ public class OpenPgpMessageInputStreamTest {
                 .addVerificationCert(cert));
         String plain = result.getA();
         assertEquals(PLAINTEXT, plain);
+        MessageMetadata metadata = result.getB();
+        assertNull(metadata.getEncryptionAlgorithm());
+        assertNull(metadata.getCompressionAlgorithm());
     }
 
     private static Tuple<String, MessageMetadata> processReadBuffered(String armoredMessage, ConsumerOptions options) throws PGPException, IOException {

pgpainless-core/src/test/java/org/pgpainless/decryption_verification/TeeBCPGInputStreamTest.java

@@ -9,6 +9,8 @@ import org.bouncycastle.openpgp.PGPException;
 import org.junit.jupiter.api.Test;
 import org.pgpainless.algorithm.OpenPgpPacket;
 import org.pgpainless.util.ArmoredInputStreamFactory;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
@@ -18,6 +20,7 @@ import java.nio.charset.StandardCharsets;
 
 public class TeeBCPGInputStreamTest {
 
+    private static final Logger LOGGER = LoggerFactory.getLogger(TeeBCPGInputStreamTest.class);
     private static final String INBAND_SIGNED = "-----BEGIN PGP MESSAGE-----\n" +
             "Version: PGPainless\n" +
             "\n" +
@@ -48,11 +51,11 @@ public class TeeBCPGInputStreamTest {
 
         int tag;
         while ((tag = nestedTeeIn.nextPacketTag()) != -1) {
-            System.out.println(OpenPgpPacket.requireFromTag(tag));
+            LOGGER.debug(OpenPgpPacket.requireFromTag(tag).toString());
             Packet packet = nestedTeeIn.readPacket();
         }
 
         nestedArmorOut.close();
-        System.out.println(nestedOut);
+        LOGGER.debug(nestedOut.toString());
     }
 }