k8ssh

k8ssh is a tool that allows you to SSH into Kubernetes pods using service accounts. It provides a secure way to access your Kubernetes pods without exposing them directly.

Features

• SSH into Kubernetes pods
• SFTP support
• Impersonation using Kubernetes service accounts
• Command execution with annotations

Installation

To install k8ssh, you need to have Go installed on your machine. Then, you can clone the repository and build the binary.

git clone https://github.com/guilhem/k8ssh.git
cd k8ssh
go build -o k8ssh ./cmd

Usage

To start the k8ssh server, use the serve command:

./k8ssh serve --address :2222

This will start the server on port 2222. You can then SSH into your Kubernetes pods using the following command:

ssh -i /path/to/private/key [email protected]@localhost -p 2222

SFTP

To use SFTP, you can use the following command:

sftp -i /path/to/private/key [email protected]@localhost -P 2222

User Management

k8ssh uses the service account name as the username when you SSH into a pod. You can configure the public key for the service account using the ssh.barpilot.io/publickey annotation.

To add user with a public key, you can use the following configuration:

apiVersion: v1
kind: ServiceAccount
metadata:
  name: my-user-ssh
  annotations:
    ssh.barpilot.io/publickey: "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABgQD..."

Access Control

k8ssh uses Kubernetes RBAC to control access to the pods. You can grant access to user service account to a specific pod by adding the following RBAC configuration:

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: pod-access
rules:
- apiGroups: [""]
  resources: ["pods/exec"]
  verbs: ["create"]
  resourceNames:
  - my-pod

You can then bind this role to a user or group using the following RBAC configuration:

apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: pod-access
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: pod-access
subjects:
- kind: ServiceAccount
  name: my-user-ssh
  namespace: default

Command Management

You can configure the command to execute when the user logs in using the ssh.barpilot.io/command annotation.

You can also configure a prefix command to execute before the main command using the ssh.barpilot.io/prefix-command annotation.

Pod Example

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
  annotations:
    ssh.barpilot.io/command: "bash"
    ssh.barpilot.io/prefix-command: "echo Prefix;"

Impersonation

k8ssh use impersonation to enforce the Kubernetes RBAC rules. When you SSH into a pod, k8ssh will impersonate the service account associated with the pod. This allows you to access the pod with the same permissions as the service account.

To impersonate a service account, you need to have the impersonate permission in the Kubernetes RBAC rules. You can grant this permission by adding the following rule to your RBAC configuration:

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: impersonate
rules:
- apiGroups: [""]
  resources: ["serviceaccounts"]
  verbs: ["impersonate"]

You can then bind this role to a user or group using the following RBAC configuration to your k8ssh service account:

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: k8sssh-impersonate
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: impersonate
subjects:
- kind: ServiceAccount
  name: k8ssh
  namespace: default

Configuration

k8ssh uses annotations on service accounts and pods to configure the SSH and SFTP commands. The following annotations are supported:

• ssh.barpilot.io/publickey: The public key for the service account.
• ssh.barpilot.io/command: The command to execute when the user logs in.
• ssh.barpilot.io/prefix-command: A prefix command to execute before the main command.

Contributing

We welcome contributions to k8ssh. To contribute, please follow these steps:

1. Fork the repository
2. Create a new branch (git checkout -b feature-branch)
3. Make your changes
4. Commit your changes (git commit -am 'Add new feature')
5. Push to the branch (git push origin feature-branch)
6. Create a new Pull Request

License

k8ssh is licensed under the Apache License, Version 2.0. See LICENSE for more information.