Add detection of untrusted deserialization in snakeyaml library

.github/CODEOWNERS

@@ -43,6 +43,7 @@ dd-java-agent/agent-iast/              @DataDog/asm-java
 dd-java-agent/instrumentation/*iast*   @DataDog/asm-java
 dd-java-agent/instrumentation/*appsec* @DataDog/asm-java
 dd-java-agent/instrumentation/json/    @DataDog/asm-java
+dd-java-agent/instrumentation/snakeyaml/    @DataDog/asm-java
 dd-smoke-tests/iast-util/              @DataDog/asm-java
 dd-smoke-tests/spring-security/        @DataDog/asm-java
 dd-java-agent/instrumentation/commons-fileupload/    @DataDog/asm-java
@@ -54,4 +55,4 @@ dd-java-agent/instrumentation/spring-security-5/ @DataDog/asm-java
 
 # @DataDog/data-jobs-monitoring
 dd-java-agent/instrumentation/spark/            @DataDog/data-jobs-monitoring
-dd-java-agent/instrumentation/spark-executor/   @DataDog/data-jobs-monitoring
+dd-java-agent/instrumentation/spark-executor/   @DataDog/data-jobs-monitoring

dd-java-agent/agent-tooling/src/main/resources/datadog/trace/agent/tooling/bytebuddy/matcher/ignored_class_name.trie

@@ -354,6 +354,8 @@
 0 org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite
 2 org.xml.*
 2 org.yaml.snakeyaml.*
+# Need for IAST sink
+0 org.yaml.snakeyaml.Yaml
 # saves ~0.5s skipping instrumentation of almost ~470 classes
 2 scala.collection.*
 

dd-java-agent/instrumentation/snakeyaml/build.gradle

@@ -0,0 +1,24 @@
+muzzle {
+  pass {
+    name = 'snakeyaml-1.x'
+    group = "org.yaml"
+    module = "snakeyaml"
+    versions = "[1.4, 2.0)"
+    assertInverse = true
+  }
+  fail {
+    group = "org.yaml"
+    module = 'snakeyaml'
+    versions = "[2.0,)"
+  }
+}
+
+apply from: "$rootDir/gradle/java.gradle"
+addTestSuiteForDir('latestDepTest', 'test')
+
+dependencies {
+  compileOnly group: 'org.yaml', name: 'snakeyaml', version: '1.33'
+  testImplementation group: 'org.yaml', name: 'snakeyaml', version: '1.33'
+
+  latestDepTestImplementation group: 'org.yaml', name: 'snakeyaml', version: '1.+'
+}

dd-java-agent/instrumentation/snakeyaml/src/main/java/datadog/trace/instrumentation/snakeyaml/SnakeYamlHelper.java

@@ -0,0 +1,39 @@
+package datadog.trace.instrumentation.snakeyaml;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.UndeclaredThrowableException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.yaml.snakeyaml.Yaml;
+import org.yaml.snakeyaml.constructor.BaseConstructor;
+
+public final class SnakeYamlHelper {
+  private SnakeYamlHelper() {}
+
+  private static final Logger log = LoggerFactory.getLogger(SnakeYamlHelper.class);
+
+  private static final Field CONSTRUCTOR = prepareConstructor();
+
+  private static Field prepareConstructor() {
+    Field constructor = null;
+    try {
+      constructor = Yaml.class.getDeclaredField("constructor");
+      constructor.setAccessible(true);
+    } catch (Throwable e) {
+      log.debug("Failed to get Yaml constructor", e);
+      return null;
+    }
+    return constructor;
+  }
+
+  public static BaseConstructor fetchConstructor(Yaml yaml) {
+    if (CONSTRUCTOR == null) {
+      return null;
+    }
+    try {
+      return (BaseConstructor) CONSTRUCTOR.get(yaml);
+    } catch (IllegalAccessException e) {
+      throw new UndeclaredThrowableException(e);
+    }
+  }
+}

dd-java-agent/instrumentation/snakeyaml/src/main/java/datadog/trace/instrumentation/snakeyaml/SnakeYamlInstrumenter.java

@@ -0,0 +1,90 @@
+package datadog.trace.instrumentation.snakeyaml;
+
+import static datadog.trace.agent.tooling.bytebuddy.matcher.ClassLoaderMatchers.hasClassNamed;
+import static datadog.trace.agent.tooling.bytebuddy.matcher.NameMatchers.named;
+import static net.bytebuddy.matcher.ElementMatchers.isMethod;
+import static net.bytebuddy.matcher.ElementMatchers.not;
+import static net.bytebuddy.matcher.ElementMatchers.takesArguments;
+
+import com.google.auto.service.AutoService;
+import datadog.trace.agent.tooling.Instrumenter;
+import datadog.trace.agent.tooling.InstrumenterModule;
+import datadog.trace.api.iast.InstrumentationBridge;
+import datadog.trace.api.iast.Sink;
+import datadog.trace.api.iast.VulnerabilityTypes;
+import datadog.trace.api.iast.sink.UntrustedDeserializationModule;
+import java.io.InputStream;
+import java.io.Reader;
+import net.bytebuddy.asm.Advice;
+import net.bytebuddy.matcher.ElementMatcher;
+import org.yaml.snakeyaml.Yaml;
+import org.yaml.snakeyaml.constructor.BaseConstructor;
+import org.yaml.snakeyaml.constructor.Constructor;
+
+@AutoService(InstrumenterModule.class)
+public class SnakeYamlInstrumenter extends InstrumenterModule.Iast
+    implements Instrumenter.ForSingleType {
+
+  public SnakeYamlInstrumenter() {
+    super("snakeyaml", "snakeyaml");
+  }
+
+  @Override
+  public String muzzleDirective() {
+    return "snakeyaml-1.x";
+  }
+
+  static final ElementMatcher.Junction<ClassLoader> NOT_SNAKEYAML_2 =
+      not(hasClassNamed("org.yaml.snakeyaml.inspector.TagInspector"));
+
+  @Override
+  public ElementMatcher.Junction<ClassLoader> classLoaderMatcher() {
+    return NOT_SNAKEYAML_2;
+  }
+
+  @Override
+  public String[] helperClassNames() {
+    return new String[] {
+      packageName + ".SnakeYamlHelper",
+    };
+  }
+
+  @Override
+  public String instrumentedType() {
+    return "org.yaml.snakeyaml.Yaml";
+  }
+
+  @Override
+  public void methodAdvice(MethodTransformer transformer) {
+    transformer.applyAdvice(
+        named("load")
+            .and(isMethod())
+            .and(
+                takesArguments(String.class)
+                    .or(takesArguments(InputStream.class))
+                    .or(takesArguments(Reader.class))),
+        SnakeYamlInstrumenter.class.getName() + "$LoadAdvice");
+  }
+
+  public static class LoadAdvice {
+
+    @Advice.OnMethodEnter(suppress = Throwable.class)
+    @Sink(VulnerabilityTypes.UNTRUSTED_DESERIALIZATION)
+    public static void onEnter(
+        @Advice.Argument(0) final Object data, @Advice.This final Yaml self) {
+      if (data == null) {
+        return;
+      }
+      final UntrustedDeserializationModule untrustedDeserialization =
+          InstrumentationBridge.UNTRUSTED_DESERIALIZATION;
+      if (untrustedDeserialization == null) {
+        return;
+      }
+      final BaseConstructor constructor = SnakeYamlHelper.fetchConstructor(self);
+      // For versions prior to 1.7 (not included), the constructor field is null
+      if (constructor instanceof Constructor || constructor == null) {
+        untrustedDeserialization.onObject(data);
+      }
+    }
+  }
+}

dd-java-agent/instrumentation/snakeyaml/src/test/groovy/SnakeYamlInstrumenterTest.groovy

@@ -0,0 +1,54 @@
+import datadog.trace.agent.test.AgentTestRunner
+import datadog.trace.api.iast.InstrumentationBridge
+import datadog.trace.api.iast.sink.UntrustedDeserializationModule
+import org.yaml.snakeyaml.Yaml
+
+class SnakeYamlInstrumenterTest extends AgentTestRunner {
+
+  @Override
+  protected void configurePreAgent() {
+    injectSysConfig('dd.iast.enabled', 'true')
+  }
+
+  void 'test snakeyaml load with an input stream'() {
+    given:
+    final module = Mock(UntrustedDeserializationModule)
+    InstrumentationBridge.registerIastModule(module)
+
+    final InputStream inputStream = new ByteArrayInputStream("test".getBytes())
+
+    when:
+    new Yaml().load(inputStream)
+
+    then:
+    1 * module.onObject(_)
+  }
+
+  void 'test snakeyaml load with a reader'() {
+    given:
+    final module = Mock(UntrustedDeserializationModule)
+    InstrumentationBridge.registerIastModule(module)
+
+    final Reader reader = new StringReader("test")
+
+    when:
+    new Yaml().load(reader)
+
+    then:
+    1 * module.onObject(_)
+  }
+
+  void 'test snakeyaml load with a string'() {
+    given:
+    final module = Mock(UntrustedDeserializationModule)
+    InstrumentationBridge.registerIastModule(module)
+
+    final String string = "test"
+
+    when:
+    new Yaml().load(string)
+
+    then:
+    1 * module.onObject(_)
+  }
+}

dd-smoke-tests/iast-util/build.gradle

@@ -10,4 +10,5 @@ dependencies {
   api project(':dd-smoke-tests')
   compileOnly group: 'org.springframework.boot', name: 'spring-boot-starter-web', version: '1.5.18.RELEASE'
   compileOnly group: 'com.google.code.gson', name: 'gson', version: '2.10'
+  compileOnly group: 'org.yaml', name: 'snakeyaml', version: '1.33'
 }

dd-smoke-tests/iast-util/src/main/java/datadog/smoketest/springboot/controller/IastWebController.java

@@ -53,6 +53,7 @@
 import org.springframework.web.servlet.view.UrlBasedViewResolver;
 import org.w3c.dom.Document;
 import org.xml.sax.SAXException;
+import org.yaml.snakeyaml.Yaml;
 
 @RestController
 public class IastWebController {
@@ -421,6 +422,12 @@ public String untrustedDeserializationParts(HttpServletRequest request)
     return "OK";
   }
 
+  @GetMapping("/untrusted_deserialization/snakeyaml")
+  public String untrustedDeserializationSnakeYaml(@RequestParam("yaml") String param) {
+    new Yaml().load(param);
+    return "OK";
+  }
+
   private void withProcess(final Operation<Process> op) {
     Process process = null;
     try {

dd-smoke-tests/iast-util/src/testFixtures/groovy/datadog/smoketest/AbstractIastSpringBootTest.groovy

@@ -1122,5 +1122,18 @@ abstract class AbstractIastSpringBootTest extends AbstractIastServerSmokeTest {
     hasVulnerability { vul -> vul.type == 'UNTRUSTED_DESERIALIZATION' }
   }
 
+  void 'untrusted deserialization for snakeyaml with a string'() {
+    setup:
+    final String yaml = "test"
+    final url = "http://localhost:${httpPort}/untrusted_deserialization/snakeyaml?yaml=${yaml}"
+    final request = new Request.Builder().url(url).get().build()
+
+    when:
+    client.newCall(request).execute()
+
+    then:
+    hasVulnerability { vul -> vul.type == 'UNTRUSTED_DESERIALIZATION' }
+  }
+
 
 }

settings.gradle

@@ -410,6 +410,7 @@ include ':dd-java-agent:instrumentation:servlet:request-3'
 include ':dd-java-agent:instrumentation:servlet:request-5'
 include ':dd-java-agent:instrumentation:shutdown'
 include ':dd-java-agent:instrumentation:slick'
+include ':dd-java-agent:instrumentation:snakeyaml'
 include ':dd-java-agent:instrumentation:span-origin'
 include ':dd-java-agent:instrumentation:spark'
 include ':dd-java-agent:instrumentation:spark:spark_2.12'