Implement ProducerOptions.setHideArmorHeaders()

Fixes #328

pgpainless-core/src/main/java/org/pgpainless/encryption_signing/EncryptionStream.java

@@ -86,7 +86,7 @@ public final class EncryptionStream extends OutputStream {
         outermostStream = new BufferedOutputStream(outermostStream);
 
         LOGGER.debug("Wrap encryption output in ASCII armor");
-        armorOutputStream = ArmoredOutputStreamFactory.get(outermostStream);
+        armorOutputStream = ArmoredOutputStreamFactory.get(outermostStream, options);
         if (options.hasComment()) {
             String[] commentLines = options.getComment().split("\n");
             for (String commentLine : commentLines) {

pgpainless-core/src/main/java/org/pgpainless/encryption_signing/ProducerOptions.java

@@ -22,6 +22,7 @@ public final class ProducerOptions {
     private StreamEncoding encodingField = StreamEncoding.BINARY;
     private boolean applyCRLFEncoding = false;
     private boolean cleartextSigned = false;
+    private boolean hideArmorHeaders = false;
 
     private CompressionAlgorithm compressionAlgorithmOverride = PGPainless.getPolicy().getCompressionAlgorithmPolicy()
             .defaultCompressionAlgorithm();
@@ -302,4 +303,22 @@ public final class ProducerOptions {
     public @Nullable SigningOptions getSigningOptions() {
         return signingOptions;
     }
+
+    public boolean isHideArmorHeaders() {
+        return hideArmorHeaders;
+    }
+
+    /**
+     * If set to <pre>true</pre>, armor headers like version or comments will be omitted from armored output.
+     * By default, armor headers are not hidden.
+     * Note: If comments are added via {@link #setComment(String)}, those are not omitted, even if
+     * {@link #hideArmorHeaders} is set to <pre>true</pre>.
+     *
+     * @param hideArmorHeaders true or false
+     * @return this
+     */
+    public ProducerOptions setHideArmorHeaders(boolean hideArmorHeaders) {
+        this.hideArmorHeaders = hideArmorHeaders;
+        return this;
+    }
 }

pgpainless-core/src/main/java/org/pgpainless/util/ArmoredOutputStreamFactory.java

@@ -7,6 +7,7 @@ package org.pgpainless.util;
 import java.io.OutputStream;
 
 import org.bouncycastle.bcpg.ArmoredOutputStream;
+import org.pgpainless.encryption_signing.ProducerOptions;
 
 /**
  * Factory to create configured {@link ArmoredOutputStream ArmoredOutputStreams}.
@@ -37,6 +38,16 @@ public final class ArmoredOutputStreamFactory {
         return armoredOutputStream;
     }
 
+    public static ArmoredOutputStream get(OutputStream outputStream, ProducerOptions options) {
+        if (options.isHideArmorHeaders()) {
+            ArmoredOutputStream armorOut = new ArmoredOutputStream(outputStream);
+            armorOut.clearHeaders();
+            return armorOut;
+        } else {
+            return get(outputStream);
+        }
+    }
+
     /**
      * Overwrite the version header of ASCII armors with a custom value.
      * Newlines in the version info string result in multiple version header entries.

pgpainless-core/src/test/java/org/pgpainless/encryption_signing/HideArmorHeadersTest.java

@@ -0,0 +1,34 @@
+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.encryption_signing;
+
+import org.bouncycastle.openpgp.PGPException;
+import org.junit.jupiter.api.Test;
+import org.pgpainless.PGPainless;
+import org.pgpainless.util.Passphrase;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class HideArmorHeadersTest {
+
+    @Test
+    public void testVersionHeaderIsOmitted() throws PGPException, IOException {
+        ByteArrayOutputStream out = new ByteArrayOutputStream();
+        EncryptionStream encryptionStream = PGPainless.encryptAndOrSign()
+                .onOutputStream(out)
+                .withOptions(ProducerOptions.encrypt(
+                        EncryptionOptions.get()
+                                .addPassphrase(Passphrase.fromPassword("sw0rdf1sh")))
+                        .setHideArmorHeaders(true));
+
+        encryptionStream.write("Hello, World!\n".getBytes());
+        encryptionStream.close();
+
+        assertTrue(out.toString().startsWith("-----BEGIN PGP MESSAGE-----\n\n")); // No "Version: PGPainless"
+    }
+}