Replace JAXB with Apache Commons Codec dependency.

The reason is that JAXB won't be part of standard Java 9 anymore, and
the only reason why we used it was to get rid of Apache Commons Codec
as dependency, three years ago. Now it makes sense to just go back to
Apache Commons Codec in preparation of upgrading to Java 9.

Partially reverts 1734d166.

Fixes #25444.

CHANGELOG.md

+# Changes in version 2.5.0 - 2018-??-??
+
+ * Medium changes
+   - Go back to using Apache Commons Codec as base64 and hexadecimal
+     codec rather than using JAXB which won't be available anymore
+     after upgrading from Java 8 to 9. Applications must provide
+     Apache Commons Codec 1.10 as dependency.
+
+
 # Changes in version 2.4.0 - 2018-05-23
 
  * Medium changes

build.xml

@@ -14,6 +14,7 @@
   <property name="jarpatternprop" value="empty" />
 
   <patternset id="runtime" >
+      <include name="commons-codec-1.10.jar"/>
       <include name="commons-compress-1.13.jar"/>
       <include name="jackson-annotations-2.8.6.jar"/>
       <include name="jackson-core-2.8.6.jar"/>

src/main/java/org/torproject/descriptor/impl/DescriptorImpl.java

@@ -6,6 +6,9 @@ package org.torproject.descriptor.impl;
 import org.torproject.descriptor.Descriptor;
 import org.torproject.descriptor.DescriptorParseException;
 
+import org.apache.commons.codec.binary.Base64;
+import org.apache.commons.codec.binary.Hex;
+
 import java.io.ByteArrayInputStream;
 import java.io.File;
 import java.io.InputStreamReader;
@@ -19,8 +22,6 @@ import java.util.Map;
 import java.util.Scanner;
 import java.util.Set;
 
-import javax.xml.bind.DatatypeConverter;
-
 public abstract class DescriptorImpl implements Descriptor {
 
   public static final String NL = "\n";
@@ -383,7 +384,7 @@ public abstract class DescriptorImpl implements Descriptor {
         end = ascii.indexOf(endToken) + endToken.length();
       }
       if (start >= 0 && end >= 0 && end > start) {
-        this.digestSha1Hex = DatatypeConverter.printHexBinary(
+        this.digestSha1Hex = Hex.encodeHexString(
             messageDigest("SHA-1", start, end)).toLowerCase();
       }
     }
@@ -426,7 +427,7 @@ public abstract class DescriptorImpl implements Descriptor {
         end = ascii.indexOf(endToken) + endToken.length();
       }
       if (start >= 0 && end >= 0 && end > start) {
-        this.digestSha256Base64 = DatatypeConverter.printBase64Binary(
+        this.digestSha256Base64 = Base64.encodeBase64String(
             messageDigest("SHA-256", start, end)).replaceAll("=", "");
       }
     }

src/main/java/org/torproject/descriptor/impl/ParseHelper.java

@@ -5,6 +5,9 @@ package org.torproject.descriptor.impl;
 
 import org.torproject.descriptor.DescriptorParseException;
 
+import org.apache.commons.codec.binary.Base64;
+import org.apache.commons.codec.binary.Hex;
+
 import java.text.DateFormat;
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
@@ -19,8 +22,6 @@ import java.util.TreeMap;
 import java.util.TreeSet;
 import java.util.regex.Pattern;
 
-import javax.xml.bind.DatatypeConverter;
-
 /**
  * Parse helper for descriptor contents.
  *
@@ -302,8 +303,7 @@ public class ParseHelper {
           + "' in line '" + line + "' is not a valid base64-encoded "
           + "20-byte value.");
     }
-    return DatatypeConverter.printHexBinary(
-        DatatypeConverter.parseBase64Binary(base64String + "="))
+    return Hex.encodeHexString(Base64.decodeBase64(base64String + "="))
         .toUpperCase();
   }
 
@@ -322,8 +322,7 @@ public class ParseHelper {
           + "' in line '" + line + "' is not a valid base64-encoded "
           + "32-byte value.");
     }
-    return DatatypeConverter.printHexBinary(
-        DatatypeConverter.parseBase64Binary(base64String + "="))
+    return Hex.encodeHexString(Base64.decodeBase64(base64String + "="))
         .toUpperCase();
   }
 
@@ -457,8 +456,7 @@ public class ParseHelper {
         .substring(beginEd25519CertLine.length(),
         identityEd25519CryptoBlock.length()
         - endEd25519CertLine.length()).replaceAll("=", "");
-    byte[] identityEd25519 = DatatypeConverter.parseBase64Binary(
-        identityEd25519Base64);
+    byte[] identityEd25519 = Base64.decodeBase64(identityEd25519Base64);
     if (identityEd25519.length < 40) {
       throw new DescriptorParseException("Invalid length of "
           + "identity-ed25519 (in bytes): " + identityEd25519.length);
@@ -494,8 +492,8 @@ public class ParseHelper {
           byte[] masterKeyEd25519 = new byte[32];
           System.arraycopy(identityEd25519, extensionStart + 4,
               masterKeyEd25519, 0, masterKeyEd25519.length);
-          String masterKeyEd25519Base64 = DatatypeConverter
-              .printBase64Binary(masterKeyEd25519).replaceAll("=", "");
+          String masterKeyEd25519Base64
+              = Base64.encodeBase64String(masterKeyEd25519).replaceAll("=", "");
           String masterKeyEd25519Base64NoTrailingEqualSigns =
               masterKeyEd25519Base64.replaceAll("=", "");
           return masterKeyEd25519Base64NoTrailingEqualSigns;