Kube Workspaces Proxy

Reverse proxy service for Kube Workspaces. Routes browser traffic to workspace pods running in Kubernetes, with per-request authentication and namespace-level access control.

Overview

The proxy sits between the ingress controller and workspace pods, handling:

• Authentication — validates kw-session HMAC-SHA256 tokens (cookie or Bearer header)
• Authorization — checks namespace access per request via User CRs (no caching = instant revocation)
• Reverse proxying — routes to workspace Services via cluster DNS
• Protocol support — HTTP, WebSocket, and SSE passthrough
• Per-image behavior — TLS backends, path prefix preservation, HTML rewriting, audio port routing

Architecture

Browser
│
▼
Ingress (/proxy/*)
│
▼
┌─────────────────────────────────────────────────┐
│ Proxy Service (:8080) │
│ │
│ Request Logging → CORS → Auth → Routing │
│ │
│ /healthz, /readyz → 200 OK │
│ /sw.js → no-op ServiceWorker │
│ /proxy/{ns}/{name} → reverse proxy handler │
└────────────────────────┬────────────────────────┘
│
▼
{name}.{namespace}.svc.cluster.local:80
(Workspace Pod)

Request Flow

1. Browser requests /proxy/{namespace}/{name}/{path...}
2. Auth middleware extracts token from kw-session cookie (or Authorization: Bearer)
3. Token signature verified against signing key from AuthConfig Secret
4. User CR looked up by email (fresh on every request)
5. Namespace access checked: admin role, personal namespace, or explicit spec.namespaceAccess[]
6. Workspace CR fetched to determine container image
7. Image CR matched to load proxy configuration (cached 30s)
8. Request forwarded to http://{name}.{namespace}.svc.cluster.local:80/{path}
9. Response headers rewritten (Location, Set-Cookie path)
10. kw-proxy-prefix cookie set on HTML responses for escaped request recovery

Getting Started

Prerequisites

• Go 1.26+
• Access to a Kubernetes cluster with Kube Workspaces CRDs installed
• AuthConfig CR (singleton named default) — auth can be disabled

Run Locally

# With KUBECONFIG pointing to your cluster
go run ./cmd/proxy/ --port=8091
# Or build and run
go build -o bin/proxy ./cmd/proxy/
./bin/proxy --port=8091

Environment Variables

Variable	Default	Description
HTTP_PORT	8080	Server listen port
PATH_PREFIX	/proxy	URL path prefix for proxy routes
ALLOWED_ORIGINS	(none)	Comma-separated CORS allowed origins
KUBECONFIG	(in-cluster)	Path to kubeconfig file (local dev)

Command-Line Flags

--port=8080 Server listen port (overrides HTTP_PORT)

Authentication

The proxy validates the same session tokens as the API service. Authentication is opt-in — when AuthConfig.spec.enabled is false (the default), all requests pass through without auth checks.

Token Format

base64url(JSON payload) . base64url(HMAC-SHA256 signature)

The signing key is read from a Kubernetes Secret referenced by AuthConfig.spec.session.signingKey.

Token Sources (checked in order)

1. kw-session HTTP cookie
2. Authorization: Bearer <token> header

Access Control

Role	Access
Admin	Full access to all namespaces
Editor/Viewer	Access to personal namespace + explicitly assigned namespaces
Disabled user	Rejected (403)

User CRs are looked up fresh on every request — disabling a user or revoking namespace access takes effect immediately.

Proxy Features

Path Prefix Preservation

For applications that support base URL configuration (e.g., linuxserver/webtop with SUBFOLDER), the proxy can forward the full path prefix to the backend:

# Normal mode (default): strips /proxy/{ns}/{name}
Request: /proxy/team/my-code/file.js
Backend: /file.js
# Preserve mode (annotation: kubeworkspaces.io/preserve-path-prefix=true):
Request: /proxy/team/my-code/file.js
Backend: /proxy/team/my-code/file.js

Audio Port Routing

Image CRs can define an audioPort in spec.proxyConfig. Requests to /audio/ within a workspace are routed to this alternate Service port:

Request: /proxy/team/my-desktop/audio/stream
Backend: http://my-desktop.team.svc.cluster.local:6902/audio/stream

Escaped Request Recovery

Some applications (e.g., KasmVNC WebSocket at /websockify) make requests that "escape" the proxy prefix. The proxy recovers these using:

1. Referer header — extracts the proxy prefix from the referring page
2. kw-proxy-prefix cookie — fallback when Referer is absent

HTML Response Rewriting

On HTML responses, the proxy:

• Sets the kw-proxy-prefix cookie (for escaped request recovery)
• Injects <base> tags when configured (injectBaseTag in Image CR)

WebSocket Support

WebSocket connections are proxied transparently. The Upgrade and Connection headers are passed through. Image CRs can declare known WebSocket paths in spec.proxyConfig.websocketPaths.

TLS Backends

When spec.proxyConfig.tlsInsecure: true is set on an Image CR, the proxy connects to the backend over TLS with certificate verification disabled (for self-signed certs common in VNC/desktop images).

CORS

Configurable via the ALLOWED_ORIGINS environment variable. Supports preflight (OPTIONS) requests.

Kubernetes Resources Accessed

Resource	Scope	Access	Caching
AuthConfig (kubeworkspaces.io/v1alpha1)	Cluster	Read	30s
User (kubeworkspaces.io/v1alpha1)	Cluster	Read	None (fresh per request)
Workspace (kubeworkspaces.io/v1alpha1)	Namespaced	Read	10s
Image (kubeworkspaces.io/v1alpha1)	Cluster	Read	30s
Secret	Namespaced	Read	With AuthConfig (30s)

The Kubernetes client is configured with QPS=50 and Burst=100 to prevent rate-limiting delays under load.

Docker

Build

docker build -t ghcr.io/kube-workspaces/proxy:latest .

Run

docker run -p 8080:8080 \
-e ALLOWED_ORIGINS="https://workspaces.example.com" \
-v ~/.kube/config:/home/nonroot/.kube/config:ro \
ghcr.io/kube-workspaces/proxy:latest

The production image uses distroless/static:nonroot (runs as UID 65532).

Project Structure

cmd/proxy/
main.go # Entrypoint, server setup, middleware chain
internal/
auth/
config.go # AuthConfig/User CR loading, namespace access checks
middleware.go # HTTP auth middleware
token.go # HMAC-SHA256 token validation
k8s/
client.go # Kubernetes dynamic client, Image/Workspace caching
proxy/
proxy.go # Reverse proxy handler, response rewriting
Dockerfile # Multi-stage build (golang → distroless)

Related Repositories

Repository	Role
kube-workspaces/controller	Defines CRDs, manages workspace lifecycle
kube-workspaces/api	REST API for workspace CRUD, issues session tokens
kube-workspaces/frontend	Web UI that navigates users to proxy URLs
kube-workspaces/deploy	Helm/Kustomize deployment manifests

License

See LICENSE.