Add email domain blacklisting

src/main/java/net/frozenorb/apiv3/route/users/POSTUsersIdRegister.java

@@ -10,18 +10,15 @@ import net.frozenorb.apiv3.model.NotificationTemplate;
 import net.frozenorb.apiv3.model.User;
 import net.frozenorb.apiv3.unsorted.BlockingCallback;
 import net.frozenorb.apiv3.unsorted.Notification;
+import net.frozenorb.apiv3.util.EmailUtils;
 import net.frozenorb.apiv3.util.ErrorUtils;
 
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
-import java.util.regex.Pattern;
 
 public final class POSTUsersIdRegister implements Handler<RoutingContext> {
 
-    private static final Pattern VALID_EMAIL_PATTERN = Pattern.compile(
+
-            "^[A-Z0-9._%+-]+@[A-Z0-9.-]+\\.[A-Z]{2,6}$",
-            Pattern.CASE_INSENSITIVE
-    );
 
     public void handle(RoutingContext ctx) {
         BlockingCallback<User> userCallback = new BlockingCallback<>();
@@ -41,11 +38,16 @@ public final class POSTUsersIdRegister implements Handler<RoutingContext> {
         JsonObject requestBody = ctx.getBodyAsJson();
         String email = requestBody.getString("email");
 
-        if (!VALID_EMAIL_PATTERN.matcher(email).matches()) {
+        if (!EmailUtils.isValidEmail(email)) {
             ErrorUtils.respondInvalidInput(ctx, email + " is not a valid email.");
             return;
         }
 
+        if (EmailUtils.isBannedEmailDomain(email)) {
+            ErrorUtils.respondInvalidInput(ctx, email + " is from a blacklisted domain.");
+            return;
+        }
+
         if (user.getPendingEmailToken() != null && (System.currentTimeMillis() - user.getPendingEmailTokenSetAt().toEpochMilli()) < TimeUnit.DAYS.toMillis(2)) {
             ErrorUtils.respondGeneric(ctx, 200, "We just recently sent you a confirmation email. Please wait before trying to register again.");
             return;

src/main/java/net/frozenorb/apiv3/util/EmailUtils.java

@@ -0,0 +1,51 @@
+package net.frozenorb.apiv3.util;
+
+import com.google.common.collect.ImmutableSet;
+import io.vertx.core.http.HttpClient;
+import io.vertx.core.http.HttpClientOptions;
+import lombok.experimental.UtilityClass;
+import lombok.extern.slf4j.Slf4j;
+import net.frozenorb.apiv3.APIv3;
+
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+import java.util.regex.Pattern;
+
+@Slf4j
+@UtilityClass
+public class EmailUtils {
+
+    private static final Pattern VALID_EMAIL_PATTERN = Pattern.compile(
+            "^[A-Z0-9._%+-]+@[A-Z0-9.-]+\\.[A-Z]{2,6}$",
+            Pattern.CASE_INSENSITIVE
+    );
+    private static final HttpClient httpsClient = APIv3.getVertxInstance().createHttpClient(new HttpClientOptions().setSsl(true).setTrustAll(true));
+    private static Set<String> bannedEmailDomains = ImmutableSet.of();
+
+    static {
+        updateBannedEmailDomains();
+        APIv3.getVertxInstance().setPeriodic(TimeUnit.MINUTES.toMillis(10), (id) -> updateBannedEmailDomains());
+    }
+
+    private static void updateBannedEmailDomains() {
+        httpsClient.get(443, "raw.githubusercontent.com", "/martenson/disposable-email-domains/master/disposable_email_blacklist.conf", (response) -> {
+            response.bodyHandler((body) -> bannedEmailDomains = ImmutableSet.copyOf(body.toString().split("\n")));
+            response.exceptionHandler(Throwable::printStackTrace);
+        }).end();
+    }
+
+    public static boolean isBannedEmailDomain(String email) {
+        if (email == null) {
+            return false;
+        }
+
+        String[] split = email.split("@");
+        String domain = split[1];
+        return split.length == 2 && bannedEmailDomains.contains(domain.toLowerCase());
+    }
+
+    public static boolean isValidEmail(String email) {
+        return VALID_EMAIL_PATTERN.matcher(email).matches();
+    }
+
+}