11/5/2020 Generate An Ssh Key For Jenkins
With many of the tools commonly used in a Continuous Delivery pipeline, Windows is not the original OS the tool was developed for. Although support and adoption are growing all the time, there can still be some pain points and gotchas in configuring some of them to work as you would expect on a Windows OS.
For Windows: Install the necessary plugins for the repository (ex: GitHub install GitHub and GitHub Authentication plugins) in Jenkins. You can generate a key with Putty key generator, or by running the following command in git bash: $ ssh-keygen -t rsa -b 4096 -C [email protected]. Dec 03, 2017 When generating SSH key for Jenkins user, two files were created (idrsa and idrsa.pub). One of them is public and the other is private. Public key goes to GitHub.
Nov 22, 2016 1) Generate Public Key & Private Key(SSH Keys) of the user. Command: ssh-keygen -t rsa -C '[email protected]', Just press to accept the default location and file name. Enter, and re-enter, a passphrase when prompted. Or Just Press Enter to leave it as blank There are other ways too to generate SSH Keys. If you don't already have an SSH key, you must generate a new SSH key.If you're unsure whether you already have an SSH key, check for existing keys. If you don't want to reenter your passphrase every time you use your SSH key, you can add your key to the SSH agent, which manages your SSH keys and remembers your passphrase.
In this post, we’re going to combine two of the big hitters in this space, Jenkins and Git. Jenkins is the most widely adopted solution for automating build and CI/CD pipelines and Git is the dominant force in source control management. We’re going to get Jenkins talking to a remote Git repository, specifically a private GitHub repository, using SSH authentication.
Git was developed specifically for managing the development of the Linux kernel (by Linus Torvolds himself no less) and was brought to Windows as an afterthought. Git comes bundled with OpenSSH, which does not yet have a production-ready implementation on Windows, although Microsoft is working on one that is currently pre-release [Win32-OpenSSH]. For this reason, Git for Windows is bundled with MINGW, a minimal GNU development environment that runs on Windows.
With that background out of the way, let’s get started.
Requirements
A note on installing Git for Windows
The first “gotcha” is how you install Git on the Jenkins worker in the first place. The Git plugin for Jenkins is not yet compatible with the Git Credential Manager for Windows. Ensure that you uncheck the box for this option at installation time.
If you see Jenkins hanging and timing out after ten minutes when executing a git fetch, this is a sign that you have the Git Credential Manager installed. The job is hanging because the Git Credential Manager has intercepted the command and is ignoring any other preconfigured authentication mechanism.
The only way around this at the moment is to choose not to install it.
Telling Jenkins where to find Git
After installation, our first job is to configure the Tool Location for Git. First, let’s figure out what the location is. Open PowerShell and input:
This will output something similar to:
Copy the path to git.exe.
In Jenkins, click Manage Jenkins then Configure System. In Global properties check Tool Locations, select (Git) Default and enter the path to git.exe in the Home textbox.
Save and exit the page.
Generating SSH keys for the Jenkins service
On Windows, the Jenkins services run as the Local System user by default, not your own user identity. It’s important to understand that Jenkins will be executing the Git commands and authenticating in the context of that user identity. This is important because OpenSSH will look for the SSH keys in the home directory of the user and the Local System account does not use the same home directory that your own personal account has.
Finding the Local System home directory
You probably don’t know what your Local System account considers its home directory. To find out, you need to start a command prompt as the Local System user and resolve %UserProfile%, but that’s easier said than done.
One way to run a process as the Local System account is to use PsExec, a Sysinternals tool that is normally used to execute programs on remote hosts. Using the -s parameter starts the process as Local System, so execute the following from PowerShell:
This will open a command prompt as Local System. Then resolve %UserProfile%:
This will output a path similar to:
So for me, C:WINDOWSsystem32configsystemprofile is the home directory of my Local Service account.
Generating keys with OpenSSH![]()
One approach to enabling your Local Service account to work over SSH with a remote repo is to copy the .ssh directory from your personal home directory (containing previously generated and configured keys) over to the Local Service home directory, so that it effectively uses the same identity as your personal account over SSH. But I prefer to keep Local Service as a separate identity with its own keys, so generating new SSH keys is what we will be doing next.
From the Local Service command prompt you started with PsExec earlier, execute:
This will start Bash in a MINGW window, the minimal GNU environment for Windows that I mentioned earlier, as the Local System user.
Execute the following to generate a new public and private RSA key with OpenSSH:
The proposed location of the keys will default to the home directory of the Local Service account that you discovered earlier, keep this default. When OpenSSH asks for a passphrase, just press Enter (and again on confirmation) to opt for no passphrase.
It is, of course, better to use SSH keys that are encrypted with a passphrase, but I have found that the Git plugin for Jenkins does not work very well with SSH keys that require a passphrase, even though its Credentials UI does allow you to enter one.
That whole workflow should look similar to the below:
You should see that there is now a .ssh directory in the Local Service home directory containing a public and private key pair. id_rsa.pub is the public key and is_rsa is the private key. The local Jenkins server will use the private key and the remote Git server will use the public key.
Adding the public key in GitHub
This next part is quite simple, we’re going to register the public key with our remote Git server. https://high-powerpizza600.weebly.com/blog/microsoft-windows-activation-key-generator. I’m going to use my personal GitHub, but it should be simple to replace these steps with the equivalents for the likes of BitBucket, etc.
And we’re done. Let’s test that we can now authenticate successfully with the corresponding private key.
Testing the SSH keys
Back in the MINGW shell (still running as our Local Service account) enter the following to connect to GitHub with SSH:
You will probably find that github.com is not yet a known host and you will get a prompt similar to below.
Just enter yes to accept the connection. On successfully connecting you will see:
We can see that the keys are correctly associated with our GitHub account.
Testing with a Jenkins project
Now all that remains is to test everything with a Jenkins project. For this I have a private GitHub repository containing the following Jenkinsfile:
This pipeline script just outputs “Hello, World!” to the console output, so nothing too interesting. Now we just need a Jenkins job to execute it:
The “Pipeline script from SCM” option means that the job definition lives in the SCM system itself and must be fetched to run. Our job won’t work at all if Jenkins isn’t successful in authenticating with GitHub using our SSH keys.
Make sure that the Repository URL is in a form that will use SSH to authenticate. A HTTPS URI, e.g. https://github.com/user/repo.git, will be expecting a username and password. See Git – The Protocols for more information.
Because OpenSSH will default to looking in %UserProfile%.ssh for keys, we don’t actually need to tell Jenkins what the private key is. So I’ve associated no credentials with this test job. Of course, you could choose to if you had a need.
If we run this, we should see: Ssh generate rsa host key.
We can see “Hello, World!” so we successfully fetched the job definition from the private Git repository.
To access a Git repository Jenkins can use an SSH key.
To add the SSH key to the Jenkins server use the following Chef scriptStore the SSH key in an encrypted data bag called “keys”.Add the following to the Jenkins Chef recipe
To specify the SSH key in the Git stepJenkins Github Ssh Private Key
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December 2020
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