Do not use commons-validator for domain validation

Author: oschwald

src/main/java/com/maxmind/minfraud/request/Email.java

@@ -13,7 +13,6 @@
 import java.util.HashMap;
 import java.util.Map;
 import java.util.regex.Pattern;
-import org.apache.commons.validator.routines.DomainValidator;
 import org.apache.commons.validator.routines.EmailValidator;
 
 /**
@@ -28,6 +27,9 @@ public final class Email extends AbstractModel {
     private static final Map<String, String> equivalentDomains;
     private static final Map<String, Boolean> fastmailDomains;
     private static final Map<String, Boolean> yahooDomains;
+    private static final Pattern DOMAIN_LABEL_PATTERN = Pattern.compile(
+        "^[a-zA-Z0-9]$|^[a-zA-Z0-9][a-zA-Z0-9\\-]*[a-zA-Z0-9]$"
+    );
     private static final Pattern DOT_PATTERN = Pattern.compile("\\.");
     private static final Pattern TRAILING_DOT_PATTERN = Pattern.compile("\\.+$");
     private static final Pattern REPEAT_COM_PATTERN = Pattern.compile("(?:\\.com){2,}$");
@@ -373,7 +375,7 @@ public Email.Builder hashAddress() {
          * @throws IllegalArgumentException when domain is not a valid domain.
          */
         public Email.Builder domain(String domain) {
-            if (enableValidation && !DomainValidator.getInstance().isValid(domain)) {
+            if (enableValidation && !isValidDomain(domain)) {
                 throw new IllegalArgumentException("The email domain " + domain + " is not valid.");
             }
             this.domain = domain;
@@ -491,6 +493,49 @@ private String cleanDomain(String domain) {
         return domain;
     }
 
+    private static boolean isValidDomain(String domain) {
+        if (domain == null || domain.isEmpty()) {
+            return false;
+        }
+
+        String asciiDomain;
+        try {
+            asciiDomain = IDN.toASCII(domain);
+        } catch (IllegalArgumentException e) {
+            return false;
+        }
+
+        if (domain.endsWith(".")) {
+            domain = domain.substring(0, domain.length() - 1);
+        }
+
+        if (asciiDomain.length() > 255) {
+            return false;
+        }
+
+        String[] labels = asciiDomain.split("\\.");
+
+        if (labels.length < 2) {
+            return false;
+        }
+
+        for (String label : labels) {
+            if (!isValidDomainLabel(label)) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    private static boolean isValidDomainLabel(String label) {
+        if (label == null || label.isEmpty() || label.length() > 63) {
+            return false;
+        }
+
+        return DOMAIN_LABEL_PATTERN.matcher(label).matches();
+    }
+
     /**
      * @return The domain of the email address used in the transaction.
      */

src/test/java/com/maxmind/minfraud/request/EmailTest.java

@@ -12,6 +12,8 @@
 import java.util.HashMap;
 import java.util.Map;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
 public class EmailTest {
 
@@ -264,11 +266,32 @@ public void testDomainWithoutValidation() {
         assertEquals(domain, email.getDomain());
     }
 
-    @Test
-    public void testInvalidDomain() {
+    @ParameterizedTest(name = "Run #{index}: domain = \"{0}\"")
+    @ValueSource(strings = {
+            "example",
+            "",
+            "   ",
+            " domain.com",
+            "domain.com ",
+            "domain com.com",
+            "domain_name.com",
+            "domain$.com",
+            "-domain.com",
+            "domain-.com",
+            "domain..com",
+            ".domain.com",
+            "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.com",
+            "a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a" +
+            ".a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a" +
+            ".a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a" +
+            ".a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a" +
+            ".com",
+            "xn--.com"
+    })
+    void testInvalidDomains(String invalidDomain) {
         assertThrows(
             IllegalArgumentException.class,
-            () -> new Builder().domain(" domain.com").build()
+            () -> new Builder().domain(invalidDomain).build()
         );
     }
 }