Better support for Armor headers

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

@@ -19,17 +19,27 @@ import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.util.ArrayList;
 import java.util.Iterator;
+import java.util.List;
 
+import org.bouncycastle.bcpg.ArmoredInputStream;
 import org.bouncycastle.bcpg.ArmoredOutputStream;
 import org.bouncycastle.openpgp.PGPKeyRing;
 import org.bouncycastle.openpgp.PGPPublicKeyRing;
 import org.bouncycastle.openpgp.PGPSecretKeyRing;
 import org.bouncycastle.util.io.Streams;
+import org.pgpainless.algorithm.HashAlgorithm;
 import org.pgpainless.key.OpenPgpV4Fingerprint;
 
 public class ArmorUtils {
 
+    public static final String HEADER_COMMENT = "Comment";
+    public static final String HEADER_VERSION = "Version";
+    public static final String HEADER_MESSAGEID = "MessageID";
+    public static final String HEADER_HASH = "Hash";
+    public static final String HEADER_CHARSET = "Charset";
+
     public static String toAsciiArmoredString(PGPSecretKeyRing secretKeys) throws IOException {
         MultiMap<String, String> header = keyToHeader(secretKeys);
         return toAsciiArmoredString(secretKeys.getEncoded(), header);
@@ -45,9 +55,9 @@ public class ArmorUtils {
         OpenPgpV4Fingerprint fingerprint = new OpenPgpV4Fingerprint(keyRing);
         Iterator<String> userIds = keyRing.getPublicKey().getUserIDs();
 
-        header.put("Comment", fingerprint.prettyPrint());
+        header.put(HEADER_COMMENT, fingerprint.prettyPrint());
         if (userIds.hasNext()) {
-            header.put("Comment", userIds.next());
+            header.put(HEADER_COMMENT, userIds.next());
         }
         return header;
     }
@@ -79,4 +89,45 @@ public class ArmorUtils {
 
         return out.toString();
     }
+
+    public static List<String> getCommendHeaderValues(ArmoredInputStream armor) {
+        return getArmorHeaderValues(armor, HEADER_COMMENT);
+    }
+
+    public static List<String> getMessageIdHeaderValues(ArmoredInputStream armor) {
+        return getArmorHeaderValues(armor, HEADER_MESSAGEID);
+    }
+
+    public static List<String> getHashHeaderValues(ArmoredInputStream armor) {
+        return getArmorHeaderValues(armor, HEADER_HASH);
+    }
+
+    public static List<HashAlgorithm> getHashAlgorithms(ArmoredInputStream armor) {
+        List<String> algorithmNames = getHashHeaderValues(armor);
+        List<HashAlgorithm> algorithms = new ArrayList<>(algorithmNames.size());
+        for (String name : algorithmNames) {
+            algorithms.add(HashAlgorithm.fromName(name));
+        }
+        return algorithms;
+    }
+
+    public static List<String> getVersionHeaderValues(ArmoredInputStream armor) {
+        return getArmorHeaderValues(armor, HEADER_VERSION);
+    }
+
+    public static List<String> getCharsetHeaderValues(ArmoredInputStream armor) {
+        return getArmorHeaderValues(armor, HEADER_CHARSET);
+    }
+
+    public static List<String> getArmorHeaderValues(ArmoredInputStream armor, String headerKey) {
+        String[] header = armor.getArmorHeaders();
+        String key = headerKey + ": ";
+        List<String> values = new ArrayList<>();
+        for (String line : header) {
+            if (line.startsWith(key)) {
+                values.add(line.substring(key.length()));
+            }
+        }
+        return values;
+    }
 }

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

@@ -28,7 +28,7 @@ public class ArmoredOutputStreamFactory {
 
     public static ArmoredOutputStream get(OutputStream outputStream) {
         ArmoredOutputStream armoredOutputStream = new ArmoredOutputStream(outputStream);
-        armoredOutputStream.setHeader(ArmoredOutputStream.VERSION_HDR, VERSION);
+        armoredOutputStream.setHeader(ArmorUtils.HEADER_VERSION, VERSION);
         return armoredOutputStream;
     }
 }

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

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2021 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.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.util.List;
+
+import org.bouncycastle.bcpg.ArmoredInputStream;
+import org.junit.jupiter.api.Test;
+import org.pgpainless.algorithm.HashAlgorithm;
+
+public class ArmorUtilsTest {
+
+    @Test
+    public void testParseArmorHeader() throws IOException {
+        String armoredKey = "-----BEGIN PGP PUBLIC KEY BLOCK-----\n" +
+                "Version: BCPG v1.68\n" +
+                "Hash: SHA512\n" +
+                "Comment: This is a comment\n" +
+                "Comment: This is another comment\n" +
+                "\n" +
+                "mDMEYJ/OsRYJKwYBBAHaRw8BAQdAaOs6IF1fWhN/dqwfSrxD/MNnBXVEx8WlecCa\n" +
+                "cAiSCv60DnRlc3RAdGVzdC50ZXN0iHgEExYKACAFAmCfzrECGwMFFgIDAQAECwkI\n" +
+                "BwUVCgkICwIeAQIZAQAKCRD2lyhrcqSwzDWIAP9i6LfaUp3gEhGQR3FojyhfPVB1\n" +
+                "Y3bBU7osj/XOpEN6RAD/YzL9VO45yYp1IUvU1NQWJy42ZHHZy4ZrjULLQ/HbpQW4\n" +
+                "OARgn86xEgorBgEEAZdVAQUBAQdASAPiuOakmDdL0HaSemeNB5Hl7lniD8vCeFgz\n" +
+                "OcgWjSYDAQgHiHUEGBYKAB0FAmCfzrECGwwFFgIDAQAECwkIBwUVCgkICwIeAQAK\n" +
+                "CRD2lyhrcqSwzJ4HAQD7uDYyEsqEGHI4LULfphxPSC5nG9pbBA3mL4ze46uDmAD/\n" +
+                "aea172D0TfBwQXZxujLECTce5/1jyTaM+ee8gfw1BQ8=\n" +
+                "=RQHd\n" +
+                "-----END PGP PUBLIC KEY BLOCK-----";
+
+        ByteArrayInputStream in = new ByteArrayInputStream(armoredKey.getBytes(StandardCharsets.UTF_8));
+        ArmoredInputStream armorIn = new ArmoredInputStream(in);
+
+        // No charset
+        assertEquals(0, ArmorUtils.getCharsetHeaderValues(armorIn).size());
+
+        // Version
+        List<String> versionHeader = ArmorUtils.getVersionHeaderValues(armorIn);
+        assertEquals(1, versionHeader.size());
+        assertEquals("BCPG v1.68", versionHeader.get(0));
+
+        // Hash
+        List<String> hashHeader = ArmorUtils.getHashHeaderValues(armorIn);
+        assertEquals(1, hashHeader.size());
+        assertEquals("SHA512", hashHeader.get(0));
+        List<HashAlgorithm> hashes = ArmorUtils.getHashAlgorithms(armorIn);
+        assertEquals(HashAlgorithm.SHA512, hashes.get(0));
+
+        // Comment
+        List<String> commentHeader = ArmorUtils.getCommendHeaderValues(armorIn);
+        assertEquals(2, commentHeader.size());
+        assertEquals("This is a comment", commentHeader.get(0));
+        assertEquals("This is another comment", commentHeader.get(1));
+
+        // MessageID
+        assertEquals(0, ArmorUtils.getMessageIdHeaderValues(armorIn).size());
+    }
+}