Add PGPainless.asciiArmor(PGPSignature)

pgpainless-core/src/main/java/org/pgpainless/PGPainless.java

@@ -14,6 +14,7 @@ import org.bouncycastle.openpgp.PGPException;
 import org.bouncycastle.openpgp.PGPKeyRing;
 import org.bouncycastle.openpgp.PGPPublicKeyRing;
 import org.bouncycastle.openpgp.PGPSecretKeyRing;
+import org.bouncycastle.openpgp.PGPSignature;
 import org.pgpainless.decryption_verification.DecryptionBuilder;
 import org.pgpainless.decryption_verification.DecryptionStream;
 import org.pgpainless.encryption_signing.EncryptionBuilder;
@@ -27,6 +28,7 @@ import org.pgpainless.key.modification.secretkeyring.SecretKeyRingEditorInterfac
 import org.pgpainless.key.parsing.KeyRingReader;
 import org.pgpainless.key.util.KeyRingUtils;
 import org.pgpainless.policy.Policy;
+import org.pgpainless.signature.SignatureUtils;
 import org.pgpainless.util.ArmorUtils;
 
 public final class PGPainless {
@@ -102,6 +104,19 @@ public final class PGPainless {
         }
     }
 
+    /**
+     * Wrap the detached signature in ASCII armor.
+     *
+     * @param signature detached signature
+     * @return ascii armored string
+     *
+     * @throws IOException in case of an error in the {@link ArmoredOutputStream}
+     */
+    public static String asciiArmor(@Nonnull PGPSignature signature)
+            throws IOException {
+        return ArmorUtils.toAsciiArmoredString(signature);
+    }
+
     /**
      * Wrap a key of certificate in ASCII armor and write the result into the given {@link OutputStream}.
      *

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

@@ -156,6 +156,38 @@ public final class ArmorUtils {
         return sb.toString();
     }
 
+    /**
+     * Return the ASCII armored representation of the given detached signature.
+     * The signature will not be stripped of non-exportable subpackets or trust-packets.
+     * If you need to strip those (e.g. because the signature is intended to be sent to a third party), use
+     * {@link #toAsciiArmoredString(PGPSignature, boolean)} and provide <pre>true</pre> as boolean value.
+     *
+     * @param signature signature
+     * @return ascii armored string
+     *
+     * @throws IOException in case of an error in the {@link ArmoredOutputStream}
+     */
+    @Nonnull
+    public static String toAsciiArmoredString(@Nonnull PGPSignature signature) throws IOException {
+        return toAsciiArmoredString(signature, false);
+    }
+
+    /**
+     * Return the ASCII armored representation of the given detached signature.
+     * If <pre>export</pre> is true, the signature will be stripped of non-exportable subpackets or trust-packets.
+     * If it is <pre>false</pre>, the signature will be encoded as-is.
+     *
+     * @param signature signature
+     * @return ascii armored string
+     *
+     * @throws IOException in case of an error in the {@link ArmoredOutputStream}
+     */
+    @Nonnull
+    public static String toAsciiArmoredString(@Nonnull PGPSignature signature, boolean export)
+            throws IOException {
+        return toAsciiArmoredString(signature.getEncoded(export));
+    }
+
     /**
      * Return the ASCII armored encoding of the given OpenPGP data bytes.
      *

pgpainless-core/src/test/java/org/pgpainless/util/ArmorUtilsTest.java

@@ -24,6 +24,7 @@ import org.bouncycastle.openpgp.PGPObjectFactory;
 import org.bouncycastle.openpgp.PGPPublicKey;
 import org.bouncycastle.openpgp.PGPPublicKeyRing;
 import org.bouncycastle.openpgp.PGPSecretKeyRing;
+import org.bouncycastle.openpgp.PGPSignature;
 import org.bouncycastle.openpgp.PGPUtil;
 import org.bouncycastle.util.io.Streams;
 import org.junit.jupiter.api.AfterAll;
@@ -39,6 +40,7 @@ import org.pgpainless.key.TestKeys;
 import org.pgpainless.key.generation.KeySpec;
 import org.pgpainless.key.generation.type.ecc.EllipticCurve;
 import org.pgpainless.key.generation.type.ecc.ecdsa.ECDSA;
+import org.pgpainless.signature.SignatureUtils;
 
 public class ArmorUtilsTest {
 
@@ -128,6 +130,21 @@ public class ArmorUtilsTest {
         assertTrue(ascii.startsWith("-----BEGIN PGP PRIVATE KEY BLOCK-----\n"));
     }
 
+    @Test
+    public void signatureToAsciiArmoredString() throws PGPException, IOException {
+        String SIG = "-----BEGIN PGP SIGNATURE-----\n" +
+                "Version: PGPainless\n" +
+                "\n" +
+                "iHUEARMKAB0WIQRPZlxNwsRmC8ZCXkFXNuaTGs83DAUCYJ/x5gAKCRBXNuaTGs83\n" +
+                "DFRwAP9/4wMvV3WcX59Clo7mkRce6iwW3VBdiN+yMu3tjmHB2wD/RfE28Q1v4+eo\n" +
+                "ySNgbyvqYYsNr0fnBwaG3aaj+u5ExiE=\n" +
+                "=Z2SO\n" +
+                "-----END PGP SIGNATURE-----\n";
+        PGPSignature signature = SignatureUtils.readSignatures(SIG).get(0);
+        String armored = PGPainless.asciiArmor(signature);
+        assertEquals(SIG, armored);
+    }
+
     @Test
     public void testAsciiArmorToStream() throws IOException, PGPException {
         PGPSecretKeyRing secretKeys = TestKeys.getEmilSecretKeyRing();