Add more strict hostname validation on host:check flows

gbrodman · gbrodman · commit eae1b4fa6cfa · 2025-12-26T18:18:57.000-05:00
We do most of these on host create already so we should also do them on
host checks. The only added change is the character validation (our
existing hostnames all match these).
diff --git a/core/src/main/java/google/registry/flows/domain/DomainFlowUtils.java b/core/src/main/java/google/registry/flows/domain/DomainFlowUtils.java
@@ -218,7 +218,7 @@ public static InternetDomainName validateDomainName(String name) throws EppExcep
     return domainName;
   }
 
-  private static void validateFirstLabel(String firstLabel) throws EppException {
+  public static void validateFirstLabel(String firstLabel) throws EppException {
     if (firstLabel.length() > MAX_LABEL_SIZE) {
       throw new DomainLabelTooLongException();
     }
diff --git a/core/src/main/java/google/registry/flows/host/HostCheckFlow.java b/core/src/main/java/google/registry/flows/host/HostCheckFlow.java
@@ -65,6 +65,7 @@ public EppResponse run() throws EppException {
         ForeignKeyUtils.loadKeys(Host.class, hostnames, clock.nowUtc()).keySet();
     ImmutableList.Builder<HostCheck> checks = new ImmutableList.Builder<>();
     for (String hostname : hostnames) {
+      HostFlowUtils.validateHostName(hostname);
       boolean unused = !existingIds.contains(hostname);
       checks.add(HostCheck.create(unused, hostname, unused ? null : "In use"));
     }
diff --git a/core/src/main/java/google/registry/flows/host/HostFlowUtils.java b/core/src/main/java/google/registry/flows/host/HostFlowUtils.java
@@ -14,12 +14,14 @@
 
 package google.registry.flows.host;
 
+import static google.registry.flows.domain.DomainFlowUtils.validateFirstLabel;
 import static google.registry.model.EppResourceUtils.isActive;
 import static google.registry.model.tld.Tlds.findTldForName;
 import static google.registry.util.PreconditionsUtils.checkArgumentNotNull;
 import static java.util.stream.Collectors.joining;
 
 import com.google.common.base.Ascii;
+import com.google.common.base.CharMatcher;
 import com.google.common.net.InternetDomainName;
 import google.registry.flows.EppException;
 import google.registry.flows.EppException.AuthorizationErrorException;
@@ -38,6 +40,10 @@
 /** Static utility functions for host flows. */
 public class HostFlowUtils {
 
+  /** Validator for ASCII lowercase letters, digits, and "-_", allowing "." as a separator */
+  private static final CharMatcher HOST_NAME_ALLOWED_CHARS =
+      CharMatcher.inRange('a', 'z').or(CharMatcher.inRange('0', '9').or(CharMatcher.anyOf("-._")));
+
   /** Checks that a host name is valid. */
   public static InternetDomainName validateHostName(String name) throws EppException {
     checkArgumentNotNull(name, "Must specify host name to validate");
@@ -53,6 +59,9 @@ public static InternetDomainName validateHostName(String name) throws EppExcepti
       if (!name.equals(hostNamePunyCoded)) {
         throw new HostNameNotPunyCodedException(hostNamePunyCoded);
       }
+      if (!HOST_NAME_ALLOWED_CHARS.matchesAllOf(name)) {
+        throw new BadHostNameCharacterException();
+      }
       InternetDomainName hostName = InternetDomainName.from(name);
       if (!name.equals(hostName.toString())) {
         throw new HostNameNotNormalizedException(hostName.toString());
@@ -71,6 +80,7 @@ public static InternetDomainName validateHostName(String name) throws EppExcepti
       if (hostName.parts().size() < effectiveTld.parts().size() + 2) {
         throw new HostNameTooShallowException();
       }
+      validateFirstLabel(hostName.parts().getFirst());
       return hostName;
     } catch (IllegalArgumentException e) {
       throw new InvalidHostNameException();
@@ -180,4 +190,11 @@ public HostNameNotNormalizedException(String expectedHostName) {
           String.format("Host names must be in normalized format; expected %s", expectedHostName));
     }
   }
+
+  /** Host names can only contain a-z, 0-9, '.', '_', and '-'. */
+  static class BadHostNameCharacterException extends ParameterValueSyntaxErrorException {
+    public BadHostNameCharacterException() {
+      super("Host names can only contain a-z, 0-9, '.', '_', and '-'");
+    }
+  }
 }
diff --git a/core/src/test/java/google/registry/flows/host/HostCheckFlowTest.java b/core/src/test/java/google/registry/flows/host/HostCheckFlowTest.java
@@ -20,7 +20,9 @@
 import static google.registry.testing.EppExceptionSubject.assertAboutEppExceptions;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
+import com.google.common.collect.ImmutableMap;
 import google.registry.flows.EppException;
+import google.registry.flows.EppException.ParameterValueSyntaxErrorException;
 import google.registry.flows.FlowUtils.NotLoggedInException;
 import google.registry.flows.ResourceCheckFlowTestCase;
 import google.registry.flows.exceptions.TooManyResourceChecksException;
@@ -95,4 +97,36 @@ void testIcannActivityReportField_getsLogged() throws Exception {
     runFlow();
     assertIcannReportingActivityFieldLogged("srs-host-check");
   }
+
+  @Test
+  void testFailure_dotHost() throws Exception {
+    setEppInput("host_check_generic.xml", ImmutableMap.of("HOSTNAME", ".host"));
+    assertAboutEppExceptions()
+        .that(assertThrows(ParameterValueSyntaxErrorException.class, this::runFlow))
+        .marshalsToXml();
+  }
+
+  @Test
+  void testFailure_dashHost() {
+    setEppInput("host_check_generic.xml", ImmutableMap.of("HOSTNAME", "-host"));
+    assertAboutEppExceptions()
+        .that(assertThrows(ParameterValueSyntaxErrorException.class, this::runFlow))
+        .marshalsToXml();
+  }
+
+  @Test
+  void testFailure_underscoreHost() {
+    setEppInput("host_check_generic.xml", ImmutableMap.of("HOSTNAME", "_host"));
+    assertAboutEppExceptions()
+        .that(assertThrows(ParameterValueSyntaxErrorException.class, this::runFlow))
+        .marshalsToXml();
+  }
+
+  @Test
+  void testFailure_hostDash() {
+    setEppInput("host_check_generic.xml", ImmutableMap.of("HOSTNAME", "host-"));
+    assertAboutEppExceptions()
+        .that(assertThrows(ParameterValueSyntaxErrorException.class, this::runFlow))
+        .marshalsToXml();
+  }
 }
diff --git a/core/src/test/java/google/registry/flows/host/HostCreateFlowTest.java b/core/src/test/java/google/registry/flows/host/HostCreateFlowTest.java
@@ -39,12 +39,12 @@
 import google.registry.flows.exceptions.ResourceCreateContentionException;
 import google.registry.flows.host.HostCreateFlow.SubordinateHostMustHaveIpException;
 import google.registry.flows.host.HostCreateFlow.UnexpectedExternalHostIpException;
+import google.registry.flows.host.HostFlowUtils.BadHostNameCharacterException;
 import google.registry.flows.host.HostFlowUtils.HostNameNotLowerCaseException;
 import google.registry.flows.host.HostFlowUtils.HostNameNotNormalizedException;
 import google.registry.flows.host.HostFlowUtils.HostNameNotPunyCodedException;
 import google.registry.flows.host.HostFlowUtils.HostNameTooLongException;
 import google.registry.flows.host.HostFlowUtils.HostNameTooShallowException;
-import google.registry.flows.host.HostFlowUtils.InvalidHostNameException;
 import google.registry.flows.host.HostFlowUtils.SuperordinateDomainDoesNotExistException;
 import google.registry.flows.host.HostFlowUtils.SuperordinateDomainInPendingDeleteException;
 import google.registry.model.ForeignKeyUtils;
@@ -286,7 +286,7 @@ private void doFailingHostNameTest(String hostName, Class<? extends EppException
 
   @Test
   void testFailure_badCharacter() {
-    doFailingHostNameTest("foo bar", InvalidHostNameException.class);
+    doFailingHostNameTest("foo bar", BadHostNameCharacterException.class);
   }
 
   @Test
diff --git a/core/src/test/java/google/registry/flows/host/HostUpdateFlowTest.java b/core/src/test/java/google/registry/flows/host/HostUpdateFlowTest.java
@@ -54,13 +54,13 @@
 import google.registry.flows.ResourceFlowUtils.StatusNotClientSettableException;
 import google.registry.flows.exceptions.ResourceHasClientUpdateProhibitedException;
 import google.registry.flows.exceptions.ResourceStatusProhibitsOperationException;
+import google.registry.flows.host.HostFlowUtils.BadHostNameCharacterException;
 import google.registry.flows.host.HostFlowUtils.HostDomainNotOwnedException;
 import google.registry.flows.host.HostFlowUtils.HostNameNotLowerCaseException;
 import google.registry.flows.host.HostFlowUtils.HostNameNotNormalizedException;
 import google.registry.flows.host.HostFlowUtils.HostNameNotPunyCodedException;
 import google.registry.flows.host.HostFlowUtils.HostNameTooLongException;
 import google.registry.flows.host.HostFlowUtils.HostNameTooShallowException;
-import google.registry.flows.host.HostFlowUtils.InvalidHostNameException;
 import google.registry.flows.host.HostFlowUtils.SuperordinateDomainDoesNotExistException;
 import google.registry.flows.host.HostFlowUtils.SuperordinateDomainInPendingDeleteException;
 import google.registry.flows.host.HostUpdateFlow.CannotAddIpToExternalHostException;
@@ -1259,7 +1259,7 @@ private void doFailingHostNameTest(String hostName, Class<? extends EppException
 
   @Test
   void testFailure_renameToBadCharacter() throws Exception {
-    doFailingHostNameTest("foo bar", InvalidHostNameException.class);
+    doFailingHostNameTest("foo bar", BadHostNameCharacterException.class);
   }
 
   @Test
diff --git a/core/src/test/java/google/registry/rdap/RdapNameserverActionTest.java b/core/src/test/java/google/registry/rdap/RdapNameserverActionTest.java
@@ -74,7 +74,9 @@ void testInvalidNameserver_returns400() {
         .that(generateActualJson("invalid/host/name"))
         .isEqualTo(
             generateExpectedJsonError(
-                "invalid/host/name is not a valid nameserver: Invalid host name", 400));
+                "invalid/host/name is not a valid nameserver: Host names can only contain a-z, 0-9,"
+                    + " '.', '_', and '-'",
+                400));
     assertThat(response.getStatus()).isEqualTo(400);
   }
 
diff --git a/core/src/test/resources/google/registry/flows/host/host_check_50.xml b/core/src/test/resources/google/registry/flows/host/host_check_50.xml
@@ -3,56 +3,56 @@
     <check>
       <host:check
        xmlns:host="urn:ietf:params:xml:ns:host-1.0">
-        <host:name>www1.tld</host:name>
-        <host:name>www2.tld</host:name>
-        <host:name>www3.tld</host:name>
-        <host:name>www4.tld</host:name>
-        <host:name>www5.tld</host:name>
-        <host:name>www6.tld</host:name>
-        <host:name>www7.tld</host:name>
-        <host:name>www8.tld</host:name>
-        <host:name>www9.tld</host:name>
-        <host:name>www10.tld</host:name>
-        <host:name>www11.tld</host:name>
-        <host:name>www12.tld</host:name>
-        <host:name>www13.tld</host:name>
-        <host:name>www14.tld</host:name>
-        <host:name>www15.tld</host:name>
-        <host:name>www16.tld</host:name>
-        <host:name>www17.tld</host:name>
-        <host:name>www18.tld</host:name>
-        <host:name>www19.tld</host:name>
-        <host:name>www20.tld</host:name>
-        <host:name>www21.tld</host:name>
-        <host:name>www22.tld</host:name>
-        <host:name>www23.tld</host:name>
-        <host:name>www24.tld</host:name>
-        <host:name>www25.tld</host:name>
-        <host:name>www26.tld</host:name>
-        <host:name>www27.tld</host:name>
-        <host:name>www28.tld</host:name>
-        <host:name>www29.tld</host:name>
-        <host:name>www30.tld</host:name>
-        <host:name>www31.tld</host:name>
-        <host:name>www32.tld</host:name>
-        <host:name>www33.tld</host:name>
-        <host:name>www34.tld</host:name>
-        <host:name>www35.tld</host:name>
-        <host:name>www36.tld</host:name>
-        <host:name>www37.tld</host:name>
-        <host:name>www38.tld</host:name>
-        <host:name>www39.tld</host:name>
-        <host:name>www40.tld</host:name>
-        <host:name>www41.tld</host:name>
-        <host:name>www42.tld</host:name>
-        <host:name>www43.tld</host:name>
-        <host:name>www44.tld</host:name>
-        <host:name>www45.tld</host:name>
-        <host:name>www46.tld</host:name>
-        <host:name>www47.tld</host:name>
-        <host:name>www48.tld</host:name>
-        <host:name>www49.tld</host:name>
-        <host:name>www50.tld</host:name>
+        <host:name>ns1.www1.tld</host:name>
+        <host:name>ns1.www2.tld</host:name>
+        <host:name>ns1.www3.tld</host:name>
+        <host:name>ns1.www4.tld</host:name>
+        <host:name>ns1.www5.tld</host:name>
+        <host:name>ns1.www6.tld</host:name>
+        <host:name>ns1.www7.tld</host:name>
+        <host:name>ns1.www8.tld</host:name>
+        <host:name>ns1.www9.tld</host:name>
+        <host:name>ns1.www10.tld</host:name>
+        <host:name>ns1.www11.tld</host:name>
+        <host:name>ns1.www12.tld</host:name>
+        <host:name>ns1.www13.tld</host:name>
+        <host:name>ns1.www14.tld</host:name>
+        <host:name>ns1.www15.tld</host:name>
+        <host:name>ns1.www16.tld</host:name>
+        <host:name>ns1.www17.tld</host:name>
+        <host:name>ns1.www18.tld</host:name>
+        <host:name>ns1.www19.tld</host:name>
+        <host:name>ns1.www20.tld</host:name>
+        <host:name>ns1.www21.tld</host:name>
+        <host:name>ns1.www22.tld</host:name>
+        <host:name>ns1.www23.tld</host:name>
+        <host:name>ns1.www24.tld</host:name>
+        <host:name>ns1.www25.tld</host:name>
+        <host:name>ns1.www26.tld</host:name>
+        <host:name>ns1.www27.tld</host:name>
+        <host:name>ns1.www28.tld</host:name>
+        <host:name>ns1.www29.tld</host:name>
+        <host:name>ns1.www30.tld</host:name>
+        <host:name>ns1.www31.tld</host:name>
+        <host:name>ns1.www32.tld</host:name>
+        <host:name>ns1.www33.tld</host:name>
+        <host:name>ns1.www34.tld</host:name>
+        <host:name>ns1.www35.tld</host:name>
+        <host:name>ns1.www36.tld</host:name>
+        <host:name>ns1.www37.tld</host:name>
+        <host:name>ns1.www38.tld</host:name>
+        <host:name>ns1.www39.tld</host:name>
+        <host:name>ns1.www40.tld</host:name>
+        <host:name>ns1.www41.tld</host:name>
+        <host:name>ns1.www42.tld</host:name>
+        <host:name>ns1.www43.tld</host:name>
+        <host:name>ns1.www44.tld</host:name>
+        <host:name>ns1.www45.tld</host:name>
+        <host:name>ns1.www46.tld</host:name>
+        <host:name>ns1.www47.tld</host:name>
+        <host:name>ns1.www48.tld</host:name>
+        <host:name>ns1.www49.tld</host:name>
+        <host:name>ns1.www50.tld</host:name>
       </host:check>
     </check>
     <clTRID>ABC-12345</clTRID>
diff --git a/core/src/test/resources/google/registry/flows/host/host_check_generic.xml b/core/src/test/resources/google/registry/flows/host/host_check_generic.xml
@@ -0,0 +1,11 @@
+<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
+    <command>
+        <check>
+            <host:check
+                    xmlns:host="urn:ietf:params:xml:ns:host-1.0">
+                <host:name>%HOSTNAME%</host:name>
+            </host:check>
+        </check>
+        <clTRID>ABC-12345</clTRID>
+    </command>
+</epp>

Original file line number	Diff line number	Diff line change
`@@ -218,7 +218,7 @@ public static InternetDomainName validateDomainName(String name) throws EppExcep`
`218`	`218`	`return domainName;`
`219`	`219`	`}`
`220`	`220`
`221`		`- private static void validateFirstLabel(String firstLabel) throws EppException {`
	`221`	`+ public static void validateFirstLabel(String firstLabel) throws EppException {`
`222`	`222`	`if (firstLabel.length() > MAX_LABEL_SIZE) {`
`223`	`223`	`throw new DomainLabelTooLongException();`
`224`	`224`	`}`
Original file line number	Diff line number	Diff line change
`@@ -65,6 +65,7 @@ public EppResponse run() throws EppException {`
`65`	`65`	`ForeignKeyUtils.loadKeys(Host.class, hostnames, clock.nowUtc()).keySet();`
`66`	`66`	`ImmutableList.Builder<HostCheck> checks = new ImmutableList.Builder<>();`
`67`	`67`	`for (String hostname : hostnames) {`
	`68`	`+ HostFlowUtils.validateHostName(hostname);`
`68`	`69`	`boolean unused = !existingIds.contains(hostname);`
`69`	`70`	`checks.add(HostCheck.create(unused, hostname, unused ? null : "In use"));`
`70`	`71`	`}`