InetAddresses: cleanup and implement final fallback

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

app/src/main/java/com/wireguard/config/InetAddresses.java

@@ -6,35 +6,34 @@
 package com.wireguard.config;
 
 import android.os.Build;
-import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.net.Inet4Address;
 import java.net.Inet6Address;
 import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.util.regex.Pattern;
+
+import javax.annotation.Nullable;
 
 /**
  * Utility methods for creating instances of {@link InetAddress}.
  */
 public final class InetAddresses {
-    private static Method PARSER_METHOD;
-
+    @Nullable private static final Method PARSER_METHOD;
+    private static final Pattern WONT_TOUCH_RESOLVER = Pattern.compile("^(((([0-9A-Fa-f]{1,4}:){7}([0-9A-Fa-f]{1,4}|:))|(([0-9A-Fa-f]{1,4}:){6}(:[0-9A-Fa-f]{1,4}|((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){5}(((:[0-9A-Fa-f]{1,4}){1,2})|:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){4}(((:[0-9A-Fa-f]{1,4}){1,3})|((:[0-9A-Fa-f]{1,4})?:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){3}(((:[0-9A-Fa-f]{1,4}){1,4})|((:[0-9A-Fa-f]{1,4}){0,2}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){2}(((:[0-9A-Fa-f]{1,4}){1,5})|((:[0-9A-Fa-f]{1,4}){0,3}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){1}(((:[0-9A-Fa-f]{1,4}){1,6})|((:[0-9A-Fa-f]{1,4}){0,4}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(:(((:[0-9A-Fa-f]{1,4}){1,7})|((:[0-9A-Fa-f]{1,4}){0,5}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:)))(%.+)?)|((?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))$");
 
-    private static Method getParserMethod() {
-        if (PARSER_METHOD != null)
-                return PARSER_METHOD;
+    static {
+        Method m = null;
         try {
-            // This method is only present on Android.
-            // noinspection JavaReflectionMemberAccess
-            PARSER_METHOD = InetAddress.class.getMethod("parseNumericAddress", String.class);
-        } catch (final NoSuchMethodException e) {
-            throw new RuntimeException(e);
+            if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q)
+                // noinspection JavaReflectionMemberAccess
+                m = InetAddress.class.getMethod("parseNumericAddress", String.class);
+        } catch (final Exception ignored) {
         }
-        return PARSER_METHOD;
+        PARSER_METHOD = m;
     }
 
-    private InetAddresses() {
-        // Prevent instantiation.
-    }
+    private InetAddresses() { }
 
     /**
      * Parses a numeric IPv4 or IPv6 address without performing any DNS lookups.
@@ -46,19 +45,28 @@ public final class InetAddresses {
         if (address.isEmpty())
             throw new ParseException(InetAddress.class, address, "Empty address");
         try {
-            if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q)
-                return (InetAddress) getParserMethod().invoke(null, address);
-            else
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q)
                 return android.net.InetAddresses.parseNumericAddress(address);
-        } catch (final IllegalAccessException | InvocationTargetException e) {
+            else if (PARSER_METHOD != null)
+                return (InetAddress) PARSER_METHOD.invoke(null, address);
+            else
+                throw new NoSuchMethodException("parseNumericAddress");
+        } catch (final IllegalArgumentException e) {
+            throw new ParseException(InetAddress.class, address, e);
+        } catch (final Exception e) {
             final Throwable cause = e.getCause();
             // Re-throw parsing exceptions with the original type, as callers might try to catch
             // them. On the other hand, callers cannot be expected to handle reflection failures.
             if (cause instanceof IllegalArgumentException)
                 throw new ParseException(InetAddress.class, address, cause);
-            throw new RuntimeException(e);
-        } catch (final IllegalArgumentException e) {
-                throw new ParseException(InetAddress.class, address, e);
+            try {
+                if (WONT_TOUCH_RESOLVER.matcher(address).matches())
+                    return InetAddress.getByName(address);
+                else
+                    throw new ParseException(InetAddress.class, address, "Not an IP address");
+            } catch (final UnknownHostException f) {
+                throw new ParseException(InetAddress.class, address, f);
+            }
         }
     }
 }