Update Jenkins plugins behind a corporate proxy

Many teams are running Jenkins in their environment. Most of the time it needs to go through a corporate proxy in order to access external resources. It’s relatively easy to configure a proxy in the advanced plugin configuration. But if each domain needs to be white-listed, trouble starts almost certainly.

But let’s start with possible ways of updating Jenkins plugins.

The offline aka manual scenario

If you aren’t allowed to communicate with the internet from within your productive Jenkins environment at all, you still have some options to choose from:

1. Don’t update
   Not a good idea. Period.
2. Manually check and download all your plugins with the plugin index https://plugins.jenkins.io/
   Obviously, you don’t want to do this for a typical Jenkins setup with likely more than 70 plugins.
3. Run a second Jenkins in a zone where you DO have Internet access
   Check for updates and download the desired plugins. Then copy all the .hpi files to your productive Jenkins.

The corporate proxy scenario

If you’re allowed to communicate through a corporate proxy with the Internet, your half-way. But many corporate proxies force you to white-list all required domains or IP’s in order to control access to external resources.

At first, you might think “yeaahhhh… no problem!” and you ask your network security colleagues to enable:

• https://updates.jenkins.io for getting the plugins meta-data and 
• https://updates.jenkins-ci.org for getting the binaries

But then, the Jenkins mirroring features hits you.

The meta-data JSON https://updates.jenkins.io/update-center.json provides binary URLs like this: http://updates.jenkins-ci.org/download/plugins/slack/2.10/slack.hpi

But if you call this URL, you get first redirected to http://mirrors.jenkins-ci.org/plugins/slack/2.10/slack.hpi and then another redirect is done depending on your geographic location. In my case, I get redirected to http://ftp-chi.osuosl.org/pub/jenkins/plugins/slack/2.10/slack.hpi

As the status of the mirrors might change, the possibility of returned domains change as well and you’ll find yourself talking to your network security guy quite often.

By-pass mirroring by rewriting meta-data JSON

One possible solution to go round this mirroring feature is to download the update-center.json, rewrite all links and then use the rewritten JSON.

Download and rewrite JSON

Downloading and rewriting the official update-center.json could be done with many technologies. But I choose Jenkins for this as well. Therefore I created a simple Jenkins job name “update-center”, which is scheduled to run once every day.

The following declarative pipeline does the job:

pipeline {
  agent any
  stages {
    stage('Download and modify Update-Center Data') {
      steps {
        httpRequest(
                url: "https://updates.jenkins.io/update-center.json?id=default&version=" + Jenkins.instance.version,
                consoleLogResponseBody: false,
                acceptType: 'APPLICATION_JSON',
                httpProxy: 'http://my.corporate.proxy:8080',
                outputFile: 'update-center-original.json'
        )
        script {
          updateCenterJson = readFile file: 'update-center-original.json'
          updateCenterJson = updateCenterJson.replaceAll("http:\\/\\/updates\\.jenkins-ci\\.org\\/download\\/", "http://archives.jenkins-ci.org/")
        }
        writeFile text: updateCenterJson, file: 'update-center.json'
        archiveArtifacts 'update-center.json'
      }
    }
  } 
}

Some notes regarding the above pipeline:

• You need to replace my.corporate.proxy:8080 with your actual proxy.
• We read the current installed Jenkins version with Jenkins.instance.version. This needs to be explicitly approved: https://jenkins.io/doc/book/managing/script-approval/. If this isn’t an option, the version has to be hard-coded.
• The https://plugins.jenkins.io/http_request plugin is used to download the JSON. You could achieve a similar thing with a simple curl if you don’t want this plugin.
• You still need to white-list those two domains in your corporate proxy:
  • https://updates.jenkins.io
  • http://archives.jenkins-ci.org
• Instead of using archives.jenkins-ci.org, you should use a mirror as the official archives server doesn’t provide great performance.

Use the rewritten JSON

Proxy configuration

Go to the advanced Plugin Manager configuration http://localhost:8080/pluginManager/advanced (or Jenkins > Manage Jenkins > Manage Plugins > Advanced) and configure your corporate proxy:

Update Site configuration

You can configure the URL to the JSON at the bottom of the same page.

In my setup, http://localhost/job/update-center/lastSuccessfulBuild/artifact/update-center.json is used.

Now the update will check and download behind your corporate proxy!

Permission

Note: You need to ensure, that anonymous users have read permission to your artifacts. Read more about security configuration here: https://wiki.jenkins-ci.org/display/JENKINS/Standard+Security+Setup

Questions?

Should you have specific questions on this subject, please feel free to comment and share any question you have. If it helped you please like ❤️ or share📌 this story, so others like you can find it.

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