このプロジェクトの目的は、spring-boot 環境における log4j CVE-2021-44228 のエクスプロイト脆弱性を実演し、その修正方法を示すことです。
このプロジェクトには3つのサブモジュールが含まれています。そのうちの1つは脆弱なコードを含み、他の2つはパッチが適用されています。
プロジェクトのルートで ./mvnw clean test を実行すると、両方のモジュールのテストが実行されます。
log4shell-example-unpatched では、多くの例外が表示されます（テストは依然として成功します。これは想定内です）。接続しようとするサーバーから正しい応答が得られないためです。
デフォルトのロガーをオーバーライドして log4j2 実装を使用するようにし、使用する log4j2 のバージョンをオーバーライドしていない場合、アプリケーションは脆弱になります。pom は次のようになります：```xml org.springframework.boot spring-boot-starter org.springframework.boot spring-boot-starter-logging
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-log4j2</artifactId>
</dependency>
`log4shell-example-unpatched` 内のテストを実行することで、ログ呼び出しが脆弱であることを確認できます。このテストは、ログ呼び出しが脆弱な場合に成功します。
### 自身のアプリケーションが脆弱かどうかを確認するための Spring 統合テストの使用
#### 1. `Log4ShellTest` をプロジェクトに追加する
`log4shell-example-patched-version` から `Log4ShellTest` をプロジェクトに追加します:```java
import lombok.extern.log4j.Log4j2;
import lombok.extern.slf4j.Slf4j;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.stereotype.Component;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicInteger;
@SpringBootTest
@Import(Log4ShellTest.Log4ShellConfig.class)
public class Log4ShellTest {
@Autowired
private List<Log4ShellService> servicesToTest;
@Test
public void testVulnerabilityPatched() throws Exception {
CountDownLatch waitLatch = new CountDownLatch(1);
AtomicInteger connectionAttemptCounter = new AtomicInteger();
Thread listener = new Thread(() -> {
try {
ServerSocket socket = new ServerSocket(22345);
while(true) {
waitLatch.countDown();
Socket connection = socket.accept();
connectionAttemptCounter.getAndIncrement();
connection.close();
}
}
catch(IOException ex) {
throw new IllegalStateException(ex);
}
});
listener.start();
waitLatch.await();
servicesToTest.forEach(service -> service.testLog("${jndi:ldap://127.0.0.1:22345}"));
Assertions.assertEquals(0, connectionAttemptCounter.get());
// If you're not using lombok, change the 6 to 2
Assertions.assertEquals(6, servicesToTest.size());
listener.interrupt();
}
@Configuration
@ComponentScan
public static class Log4ShellConfig {
}
public interface Log4ShellService {
void testLog(String arg);
}
@Component
public static class Service1 implements Log4ShellService {
private static final Logger logger = LogManager.getLogger("Test");
@Override
public void testLog(String arg) {
logger.info("Test: " + arg);
}
}
@Component
public static class Service2 implements Log4ShellService {
private static final Logger logger = LogManager.getLogger("Test");
@Override
public void testLog(String arg) {
logger.info("Test: {}", arg);
}
}
// Remove this class if you're not using lombok
@Component
@Slf4j
public static class Service3 implements Log4ShellService {
@Override
public void testLog(String arg) {
log.info("Test: {}", arg);
}
}
// Remove this class if you're not using lombok
@Component
@Slf4j
public static class Service4 implements Log4ShellService {
@Override
public void testLog(String arg) {
log.info("Test: " + arg);
}
}
// Remove this class if you're not using lombok
@Component
@Log4j2
public static class Service5 implements Log4ShellService {
@Override
public void testLog(String arg) {
log.info("Test: {}", arg);
}
}
// Remove this class if you're not using lombok
@Component
@Log4j2
public static class Service6 implements Log4ShellService {
@Override
public void testLog(String arg) {
log.info("Test: " + arg);
}
}
}
テストを実行し、失敗することを確認します。失敗しない場合、以下のログ行が表示され、脆弱ではありません。``` 2021-12-13 22:05:01.197 INFO 21216 --- [ main] Test : Test: ${jndi:ldap://127.0.0.1:22345} 2021-12-13 22:05:01.198 INFO 21216 --- [ main] Test : Test: ${jndi:ldap://127.0.0.1:22345} 2021-12-13 22:05:01.199 INFO 21216 --- [ main] n.c.l.Log4ShellTest$Service3 : Test: ${jndi:ldap://127.0.0.1:22345} 2021-12-13 22:05:01.199 INFO 21216 --- [ main] n.c.l.Log4ShellTest$Service4 : Test: ${jndi:ldap://127.0.0.1:22345} 2021-12-13 22:05:01.199 INFO 21216 --- [ main] n.c.l.L.Service5 : Test: ${jndi:ldap://127.0.0.1:22345} 2021-12-13 22:05:01.199 INFO 21216 --- [ main] n.c.l.L.Service6 : Test: ${jndi:ldap://127.0.0.1:22345}
テストが失敗した場合、接続が閉じられたことを示すスタックトレースが表示されるはずです:```
2021-12-13 22:06:50,635 main WARN Error looking up JNDI resource [ldap://127.0.0.1:22345]. javax.naming.CommunicationException: anonymous bind failed: 127.0.0.1:22345 [Root exception is java.net.SocketException: Socket closed]
at java.naming/com.sun.jndi.ldap.LdapClient.authenticate(LdapClient.java:198)
at java.naming/com.sun.jndi.ldap.LdapCtx.connect(LdapCtx.java:2895)
at java.naming/com.sun.jndi.ldap.LdapCtx.<init>(LdapCtx.java:348)
at java.naming/com.sun.jndi.url.ldap.ldapURLContextFactory.getUsingURLIgnoreRootDN(ldapURLContextFactory.java:60)
at java.naming/com.sun.jndi.url.ldap.ldapURLContext.getRootURLContext(ldapURLContext.java:61)
at java.naming/com.sun.jndi.toolkit.url.GenericURLContext.lookup(GenericURLContext.java:204)
at java.naming/com.sun.jndi.url.ldap.ldapURLContext.lookup(ldapURLContext.java:94)
at java.naming/javax.naming.InitialContext.lookup(InitialContext.java:409)
at org.apache.logging.log4j.core.net.JndiManager.lookup(JndiManager.java:172)
at org.apache.logging.log4j.core.lookup.JndiLookup.lookup(JndiLookup.java:56)
at org.apache.logging.log4j.core.lookup.Interpolator.lookup(Interpolator.java:221)
at org.apache.logging.log4j.core.lookup.StrSubstitutor.resolveVariable(StrSubstitutor.java:1110)
at org.apache.logging.log4j.core.lookup.StrSubstitutor.substitute(StrSubstitutor.java:1033)
at org.apache.logging.log4j.core.lookup.StrSubstitutor.substitute(StrSubstitutor.java:912)
at org.apache.logging.log4j.core.lookup.StrSubstitutor.replace(StrSubstitutor.java:467)
at org.apache.logging.log4j.core.pattern.MessagePatternConverter.format(MessagePatternConverter.java:132)
at org.apache.logging.log4j.core.pattern.PatternFormatter.format(PatternFormatter.java:38)
at org.apache.logging.log4j.core.layout.PatternLayout$PatternSerializer.toSerializable(PatternLayout.java:344)
at org.apache.logging.log4j.core.layout.PatternLayout.toText(PatternLayout.java:244)
at org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:229)
at org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:59)
at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.directEncodeEvent(AbstractOutputStreamAppender.java:197)
at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.tryAppend(AbstractOutputStreamAppender.java:190)
at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.append(AbstractOutputStreamAppender.java:181)
at org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderControl.java:156)
at org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderControl.java:129)
at org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursion(AppenderControl.java:120)
at org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:84)
at org.apache.logging.log4j.core.config.LoggerConfig.callAppenders(LoggerConfig.java:540)
at org.apache.logging.log4j.core.config.LoggerConfig.processLogEvent(LoggerConfig.java:498)
at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:481)
at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:456)
at org.apache.logging.log4j.core.config.AwaitCompletionReliabilityStrategy.log(AwaitCompletionReliabilityStrategy.java:82)
at org.apache.logging.log4j.core.Logger.log(Logger.java:161)
at org.apache.logging.log4j.spi.AbstractLogger.tryLogMessage(AbstractLogger.java:2205)
at org.apache.logging.log4j.spi.AbstractLogger.logMessageTrackRecursion(AbstractLogger.java:2159)
at org.apache.logging.log4j.spi.AbstractLogger.logMessageSafely(AbstractLogger.java:2142)
at org.apache.logging.log4j.spi.AbstractLogger.logMessage(AbstractLogger.java:2017)
at org.apache.logging.log4j.spi.AbstractLogger.logIfEnabled(AbstractLogger.java:1983)
at org.apache.logging.log4j.spi.AbstractLogger.info(AbstractLogger.java:1320)
at nl.chilit.log4shellexampleunpatched.Log4ShellTest$Service1.testLog(Log4ShellTest.java:78)
at nl.chilit.log4shellexampleunpatched.Log4ShellTest.lambda$testVulnerabilityNotPatched$1(Log4ShellTest.java:52)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at nl.chilit.log4shellexampleunpatched.Log4ShellTest.testVulnerabilityNotPatched(Log4ShellTest.java:52)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:567)
at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:725)
at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$7(TestMethodTestDescriptor.java:214)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:210)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:135)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:66)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:151)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:35)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:54)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:107)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:114)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:86)
at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:86)
at org.junit.platform.launcher.core.SessionPerRequestLauncher.execute(SessionPerRequestLauncher.java:53)
at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
Caused by: java.net.SocketException: Socket closed
at java.base/sun.nio.ch.NioSocketImpl.ensureOpenAndConnected(NioSocketImpl.java:165)
at java.base/sun.nio.ch.NioSocketImpl.beginWrite(NioSocketImpl.java:366)
at java.base/sun.nio.ch.NioSocketImpl.implWrite(NioSocketImpl.java:411)
at java.base/sun.nio.ch.NioSocketImpl.write(NioSocketImpl.java:440)
at java.base/sun.nio.ch.NioSocketImpl$2.write(NioSocketImpl.java:826)
at java.base/java.net.Socket$SocketOutputStream.write(Socket.java:1045)
at java.base/java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:81)
at java.base/java.io.BufferedOutputStream.flush(BufferedOutputStream.java:142)
at java.naming/com.sun.jndi.ldap.Connection.writeRequest(Connection.java:414)
at java.naming/com.sun.jndi.ldap.Connection.writeRequest(Connection.java:387)
at java.naming/com.sun.jndi.ldap.LdapClient.ldapBind(LdapClient.java:359)
at java.naming/com.sun.jndi.ldap.LdapClient.authenticate(LdapClient.java:192)
... 110 more
以下に説明する方法のいずれかでアプリケーションにパッチを適用し、テストを再実行してください。テストは緑色になるはずです。
脆弱性は、いくつかの方法で緩和できます。これは log4shell-example-patched-system-property および log4shell-example-patched-version で実証されています。
アプリケーションのセットアップが許せば、脆弱性を排除する最善の方法は、log4jのバージョンを最低でも2.15にアップグレードすることです。
これは、log4j2.version を 2.15.0 に設定することで行えます:```xml
<log4j2.version>2.15.0</log4j2.version>
この解決策は*チェーン内のどこかでspring-boot-parentアーティファクトを親として使用している場合にのみ機能します*。`dependencyManagement`を使用してspring-bootの依存関係を管理している場合、この解決策は機能しません:```xml
<!-- if you are using dependency management like this, upping the version by setting log4j2.version is NOT going to work -->
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>2.6.1</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
その場合、log4jの各部分のバージョンを上書きする必要があり、すぐに混乱します。
注: この修正は log4jバージョン 2.10以上 でのみ機能します
システムプロパティ log4j2.formatMsgNoLookups を true に設定することでも問題を軽減できます。注意: この設定は application.properties や application.yml では行えません。
以下のいずれかの方法で設定する必要があります:
-Dlog4j2.formatMsgNoLookups=true を追加する）LOG4J_FORMAT_MSG_NO_LOOKUPS を true に設定する）log4shell-example-patched-system-property で示されているように、Spring Boot が起動する前（SpringApplication.run(...) を呼び出す前）にシステムプロパティを設定する最後の解決策は Log4JMitigationExtension と Log4JMitigationExtension の両方に実装されています。統合テストでは Log4JMitigationExtension の main メソッドを使用しないため、
log4j がタイムリーにプロパティを認識できるように、拡張機能を使用してプロパティを設定しています。