Allow setting custom version header when encrypting/signing message

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

@@ -99,6 +99,12 @@ public final class EncryptionStream extends OutputStream {
                 }
             }
         }
+        if (options.hasVersion()) {
+            String version = options.getVersion().trim();
+            if (!version.isEmpty()) {
+                ArmorUtils.setVersionHeader(armorOutputStream, version);
+            }
+        }
         outermostStream = armorOutputStream;
     }
 

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

@@ -28,6 +28,7 @@ public final class ProducerOptions {
             .defaultCompressionAlgorithm();
     private boolean asciiArmor = true;
     private String comment = null;
+    private String version = null;
 
     private ProducerOptions(EncryptionOptions encryptionOptions, SigningOptions signingOptions) {
         this.encryptionOptions = encryptionOptions;
@@ -120,7 +121,7 @@ public final class ProducerOptions {
      * Set the comment header in ASCII armored output.
      * The default value is null, which means no comment header is added.
      * Multiline comments are possible using '\\n'.
-     *
+     * <br>
      * Note: If a default header comment is set using {@link org.pgpainless.util.ArmoredOutputStreamFactory#setComment(String)},
      * then both comments will be written to the produced ASCII armor.
      *
@@ -128,13 +129,25 @@ public final class ProducerOptions {
      * @return builder
      */
     public ProducerOptions setComment(String comment) {
-        if (!asciiArmor) {
-            throw new IllegalArgumentException("Comment can only be set when ASCII armoring is enabled.");
-        }
         this.comment = comment;
         return this;
     }
 
+    /**
+     * Set the version header in ASCII armored output.
+     * The default value is null, which means no version header is added.
+     * <br>
+     * Note: If the value is non-null, then this method overrides the default version header set using
+     * {@link org.pgpainless.util.ArmoredOutputStreamFactory#setVersionInfo(String)}.
+     *
+     * @param version version header, or null for no version info.
+     * @return builder
+     */
+    public ProducerOptions setVersion(String version) {
+        this.version = version;
+        return this;
+    }
+
     /**
      * Return comment set for header in ascii armored output.
      *
@@ -144,15 +157,33 @@ public final class ProducerOptions {
         return comment;
     }
 
+    /**
+     * Return the version info header in ascii armored output.
+     *
+     * @return version info
+     */
+    public String getVersion() {
+        return version;
+    }
+
     /**
      * Return whether a comment was set (!= null).
      *
-     * @return comment
+     * @return true if commend is set
      */
     public boolean hasComment() {
         return comment != null;
     }
 
+    /**
+     * Return whether a version header was set (!= null).
+     *
+     * @return true if version header is set
+     */
+    public boolean hasVersion() {
+        return version != null;
+    }
+
     public ProducerOptions setCleartextSigned() {
         if (signingOptions == null) {
             throw new IllegalArgumentException("Signing Options cannot be null if cleartext signing is enabled.");
@@ -233,7 +264,7 @@ public final class ProducerOptions {
     /**
      * Set format metadata field of the literal data packet.
      * Defaults to {@link StreamEncoding#BINARY}.
-     *
+     * <br>
      * This does not change the encoding of the wrapped data itself.
      * To apply CR/LF encoding to your input data before processing, use {@link #applyCRLFEncoding()} instead.
      *
@@ -257,7 +288,7 @@ public final class ProducerOptions {
     /**
      * Apply special encoding of line endings to the input data.
      * By default, this is disabled, which means that the data is not altered.
-     *
+     * <br>
      * Enabling it will change the line endings to CR/LF.
      * Note: The encoding will not be reversed when decrypting, so applying CR/LF encoding will result in
      * the identity "decrypt(encrypt(data)) == data == verify(sign(data))".

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

@@ -417,6 +417,22 @@ public final class ArmorUtils {
         return new Tuple<>(printed, countIdentities);
     }
 
+    /**
+     * Set the version header entry in the ASCII armor.
+     * If the version info is null or only contains whitespace characters, then the version header will be removed.
+     *
+     * @param armor armored output stream
+     * @param version version header.
+     */
+    public static void setVersionHeader(@Nonnull ArmoredOutputStream armor,
+                                        @Nullable String version) {
+        if (version == null || version.trim().isEmpty()) {
+            armor.setHeader(HEADER_VERSION, null);
+        } else {
+            armor.setHeader(HEADER_VERSION, version);
+        }
+    }
+
     /**
      * Add an ASCII armor header entry about the used hash algorithm into the {@link ArmoredOutputStream}.
      *