fix #969: Implement error prone ReverseDnsLookup for unexpected reverse dns lookups

README.md

@@ -172,6 +172,7 @@ Safe Logging can be found at [github.com/palantir/safe-logging](https://github.c
 - `JUnit5SuiteMisuse`: When migrating from JUnit4 -> JUnit5, classes annotated with `@RunWith(Suite.class)` are dangerous because if they reference any JUnit5 test classes, these tests will silently not run!
 - `PreferAssertj`: Prefer AssertJ fluent assertions.
 - `ThrowError`: Prefer throwing a RuntimeException rather than Error.
+- `ReverseDnsLookup`: Calling address.getHostName may result in an unexpected DNS lookup.
 
 ### Programmatic Application
 

baseline-error-prone/src/main/java/com/palantir/baseline/errorprone/ReverseDnsLookup.java

@@ -0,0 +1,72 @@
+/*
+ * (c) Copyright 2019 Palantir Technologies Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.palantir.baseline.errorprone;
+
+import com.google.auto.service.AutoService;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.fixes.SuggestedFixes;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.Matcher;
+import com.google.errorprone.matchers.method.MethodMatchers;
+import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.MethodInvocationTree;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+
+@AutoService(BugChecker.class)
+@BugPattern(
+        name = "ReverseDnsLookup",
+        link = "https://github.com/palantir/gradle-baseline#baseline-error-prone-checks",
+        linkType = BugPattern.LinkType.CUSTOM,
+        severity = BugPattern.SeverityLevel.WARNING,
+        summary = "Calling address.getHostName may result in a reverse DNS lookup which is a network request, making "
+                + "the invocation significantly more expensive than expected depending on the environment.\n"
+                + "This check is intended to be advisory - it's fine to @SuppressWarnings(\"ReverseDnsLookup\") "
+                + "in certain cases, but is usually not recommended.")
+public final class ReverseDnsLookup extends BugChecker implements BugChecker.MethodInvocationTreeMatcher {
+
+    private static final Matcher<ExpressionTree> INET_SOCKET_ADDRESS_MATCHER = MethodMatchers.instanceMethod()
+            .onDescendantOf(InetSocketAddress.class.getName())
+            .named("getHostName");
+
+    private static final Matcher<ExpressionTree> INET_ADDRESS_MATCHER = MethodMatchers.instanceMethod()
+            .onDescendantOf(InetAddress.class.getName())
+            .namedAnyOf("getHostName", "getCanonicalHostName");
+
+    @Override
+    public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
+        if (INET_SOCKET_ADDRESS_MATCHER.matches(tree, state)) {
+            return buildDescription(tree)
+                    // Suggested fix exists to provide context when compilation fails, it shouldn't be used
+                    // as a drop in replacement because the unresolved string may not be sufficient in some
+                    // cases, particularly involving auditing.
+                    .addFix(SuggestedFixes.renameMethodInvocation(tree, "getHostString", state))
+                    .build();
+        }
+        if (INET_ADDRESS_MATCHER.matches(tree, state)) {
+            return buildDescription(tree)
+                    // Suggested fix exists to provide context when compilation fails, it shouldn't be used
+                    // as a drop in replacement because the unresolved string may not be sufficient in some
+                    // cases, particularly involving auditing.
+                    .addFix(SuggestedFixes.renameMethodInvocation(tree, "getHostAddress", state))
+                    .build();
+        }
+        return Description.NO_MATCH;
+    }
+}

baseline-error-prone/src/test/java/com/palantir/baseline/errorprone/ReverseDnsLookupTest.java

@@ -0,0 +1,58 @@
+/*
+ * (c) Copyright 2019 Palantir Technologies Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.palantir.baseline.errorprone;
+
+import com.google.errorprone.BugCheckerRefactoringTestHelper;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.parallel.Execution;
+import org.junit.jupiter.api.parallel.ExecutionMode;
+
+@Execution(ExecutionMode.CONCURRENT)
+class ReverseDnsLookupTest {
+
+    @Test
+    void testFix() {
+        fix()
+                .addInputLines(
+                        "Test.java",
+                        "import java.net.InetAddress;",
+                        "import java.net.InetSocketAddress;",
+                        "class Test {",
+                        "  void f(InetAddress ia, InetSocketAddress isa) {",
+                        "    ia.getHostName();",
+                        "    ia.getCanonicalHostName();",
+                        "    isa.getHostName();",
+                        "  }",
+                        "}")
+                .addOutputLines(
+                        "Test.java",
+                        "import java.net.InetAddress;",
+                        "import java.net.InetSocketAddress;",
+                        "class Test {",
+                        "  void f(InetAddress ia, InetSocketAddress isa) {",
+                        "    ia.getHostAddress();",
+                        "    ia.getHostAddress();",
+                        "    isa.getHostString();",
+                        "  }",
+                        "}")
+                .doTest(BugCheckerRefactoringTestHelper.TestMode.TEXT_MATCH);
+    }
+
+    private BugCheckerRefactoringTestHelper fix() {
+        return BugCheckerRefactoringTestHelper.newInstance(new ReverseDnsLookup(), getClass());
+    }
+}

changelog/@unreleased/pr-970.v2.yml

@@ -0,0 +1,13 @@
+type: improvement
+improvement:
+  description: |-
+    Implement error prone ReverseDnsLookup for unexpected reverse dns lookups
+
+    Calling address.getHostName may result in a DNS lookup which is a network request,
+    making the invocation significantly more expensive than expected depending on the
+    environment.
+    This check  is intended to be advisory - it's fine to
+    @SuppressWarnings("ReverseDnsLookup") in certain cases, but is usually not
+    recommended.
+  links:
+  - https://github.com/palantir/gradle-baseline/pull/970