# OAuth2-Proxy Authentication Gateway
# Red Panda Approved

## Overview

OAuth2-Proxy provides authentication for services that don't natively support SSO/OIDC.
It acts as a reverse proxy that requires users to authenticate via Casdoor before
accessing the upstream service.

This document describes the generic approach for adding OAuth2-Proxy authentication
to any service in the Agathos infrastructure.

## Architecture

```
┌──────────────┐     ┌───────────────┐     ┌────────────────┐     ┌───────────────┐
│   Browser    │────▶│    HAProxy    │────▶│  OAuth2-Proxy  │────▶│  Your Service │
│              │     │   (titania)   │     │   (titania)    │     │   (any host)  │
└──────────────┘     └───────┬───────┘     └───────┬────────┘     └───────────────┘
                             │                     │
                             │     ┌───────────────▼───────────────┐
                             └────▶│          Casdoor              │
                                   │    (OIDC Provider - titania)  │
                                   └───────────────────────────────┘
```

## How It Works

1. User requests `https://service.ouranos.helu.ca/`
2. HAProxy routes to OAuth2-Proxy (titania:22082)
3. OAuth2-Proxy checks for valid session cookie
4. **No session?** → Redirect to Casdoor login → After login, redirect back with cookie
5. **Valid session?** → Forward request to upstream service

## File Structure

```
ansible/oauth2_proxy/
├── deploy.yml                # Main deployment playbook
├── docker-compose.yml.j2     # Docker Compose template
├── oauth2-proxy.cfg.j2       # OAuth2-Proxy configuration
└── stage.yml                 # Validation/staging playbook
```

Monitoring configuration is integrated into the host-specific Alloy config:
- `ansible/alloy/titania/config.alloy.j2` - Contains OAuth2-Proxy log collection and metrics scraping

## Variable Architecture

The OAuth2-Proxy template uses **generic variables** (`oauth2_proxy_*`) that are
mapped from **service-specific variables** in host_vars:

```
Vault (service-specific)         Host Vars (mapping)              Template (generic)
────────────────────────         ───────────────────              ──────────────────
vault_<service>_oauth2_*    ──►  <service>_oauth2_*    ──►       oauth2_proxy_*
```

This allows:
- Multiple services to use the same OAuth2-Proxy template
- Service-specific credentials in vault
- Clear naming conventions

## Configuration Steps

### Step 1: Create Casdoor Application

1. Login to Casdoor at `https://id.ouranos.helu.ca/` (Casdoor SSO)
2. Navigate to **Applications** → **Add**
3. Configure:
   - **Name**: `<your-service>` (e.g., `searxng`, `jupyter`)
   - **Organization**: `heluca` (or your organization)
   - **Redirect URLs**: `https://<service>.ouranos.helu.ca/oauth2/callback`
   - **Grant Types**: `authorization_code`, `refresh_token`
4. Save and note the **Client ID** and **Client Secret**

### Step 2: Add Vault Secrets

```bash
ansible-vault edit ansible/inventory/group_vars/all/vault.yml
```

Add service-specific credentials:
```yaml
# SearXNG OAuth2 credentials
vault_searxng_oauth2_client_id: "abc123..."
vault_searxng_oauth2_client_secret: "secret..."
vault_searxng_oauth2_cookie_secret: "<generate-with-command-below>"
```

Generate cookie secret:
```bash
openssl rand -base64 32
```

### Step 3: Configure Host Variables

Add to the host that will run OAuth2-Proxy (typically `titania.incus.yml`):

```yaml
# =============================================================================
# <Service> OAuth2 Configuration (Service-Specific)
# =============================================================================
<service>_oauth2_client_id: "{{ vault_<service>_oauth2_client_id }}"
<service>_oauth2_client_secret: "{{ vault_<service>_oauth2_client_secret }}"
<service>_oauth2_cookie_secret: "{{ vault_<service>_oauth2_cookie_secret }}"

# =============================================================================
# OAuth2-Proxy Configuration (Generic Template Variables)
# =============================================================================
oauth2_proxy_user: oauth2proxy
oauth2_proxy_group: oauth2proxy
oauth2_proxy_uid: 802
oauth2_proxy_gid: 802
oauth2_proxy_directory: /srv/oauth2-proxy
oauth2_proxy_port: 22082

# OIDC Configuration
oauth2_proxy_oidc_issuer_url: "http://titania.incus:{{ casdoor_port }}"

# Map service-specific credentials to generic template variables
oauth2_proxy_client_id: "{{ <service>_oauth2_client_id }}"
oauth2_proxy_client_secret: "{{ <service>_oauth2_client_secret }}"
oauth2_proxy_cookie_secret: "{{ <service>_oauth2_cookie_secret }}"

# Service-specific URLs
oauth2_proxy_redirect_url: "https://<service>.{{ haproxy_domain }}/oauth2/callback"
oauth2_proxy_upstream_url: "http://<service-host>:<service-port>"
oauth2_proxy_cookie_domain: "{{ haproxy_domain }}"

# Access Control
oauth2_proxy_email_domains:
  - "*"  # Or restrict to specific domains

# Session Configuration
oauth2_proxy_cookie_expire: "168h"
oauth2_proxy_cookie_refresh: "1h"

# SSL Verification
oauth2_proxy_skip_ssl_verify: true  # Set false for production
```

### Step 4: Update HAProxy Backend

Change the service backend to route through OAuth2-Proxy:

```yaml
haproxy_backends:
  - subdomain: "<service>"
    backend_host: "titania.incus"  # OAuth2-Proxy host
    backend_port: 22082            # OAuth2-Proxy port
    health_path: "/ping"           # OAuth2-Proxy health endpoint
```

### Step 5: Deploy

```bash
cd ansible

# Validate configuration
ansible-playbook oauth2_proxy/stage.yml

# Deploy OAuth2-Proxy
ansible-playbook oauth2_proxy/deploy.yml

# Update HAProxy routing
ansible-playbook haproxy/deploy.yml
```

## Complete Example: SearXNG

### Vault Variables
```yaml
vault_searxng_oauth2_client_id: "searxng-client-id-from-casdoor"
vault_searxng_oauth2_client_secret: "searxng-client-secret-from-casdoor"
vault_searxng_oauth2_cookie_secret: "ABCdef123..."
```

### Host Variables (titania.incus.yml)
```yaml
# SearXNG OAuth2 (service-specific)
searxng_oauth2_client_id: "{{ vault_searxng_oauth2_client_id }}"
searxng_oauth2_client_secret: "{{ vault_searxng_oauth2_client_secret }}"
searxng_oauth2_cookie_secret: "{{ vault_searxng_oauth2_cookie_secret }}"

# OAuth2-Proxy (generic mapping)
oauth2_proxy_client_id: "{{ searxng_oauth2_client_id }}"
oauth2_proxy_client_secret: "{{ searxng_oauth2_client_secret }}"
oauth2_proxy_cookie_secret: "{{ searxng_oauth2_cookie_secret }}"
oauth2_proxy_redirect_url: "https://searxng.{{ haproxy_domain }}/oauth2/callback"
oauth2_proxy_upstream_url: "http://oberon.incus:25599"
```

### HAProxy Backend
```yaml
- subdomain: "searxng"
  backend_host: "titania.incus"
  backend_port: 22082
  health_path: "/ping"
```

## Adding a Second Service (e.g., Jupyter)

When adding authentication to another service, you would:

1. Create a new Casdoor application for Jupyter
2. Add vault variables:
   ```yaml
   vault_jupyter_oauth2_client_id: "..."
   vault_jupyter_oauth2_client_secret: "..."
   vault_jupyter_oauth2_cookie_secret: "..."
   ```
3. Either:
   - **Option A**: Deploy a second OAuth2-Proxy instance on a different port
   - **Option B**: Configure the same OAuth2-Proxy with multiple upstreams (more complex)

For multiple services, **Option A** is recommended for isolation and simplicity.

## Monitoring

OAuth2-Proxy monitoring is handled by Grafana Alloy, which runs on each host.

### Architecture

```
OAuth2-Proxy ─────► Grafana Alloy ─────► Prometheus (prospero)
(titania)           (local agent)        (remote_write)
                         │
                         └─────────────► Loki (prospero)
                                         (log forwarding)
```

### Metrics (via Prometheus)

Alloy scrapes OAuth2-Proxy metrics at `/metrics` and forwards them to Prometheus:
- `oauth2_proxy_requests_total` - Total requests processed
- `oauth2_proxy_errors_total` - Total errors
- `oauth2_proxy_upstream_latency_seconds` - Latency to upstream service

Configuration in `ansible/alloy/titania/config.alloy.j2`:
```alloy
prometheus.scrape "oauth2_proxy" {
  targets = [{"__address__" = "127.0.0.1:{{oauth2_proxy_port}}"}]
  scrape_interval = "30s"
  forward_to = [prometheus.remote_write.default.receiver]
  job_name = "oauth2-proxy"
}
```

### Logs (via Loki)

OAuth2-Proxy logs are collected via syslog and forwarded to Loki:
```alloy
loki.source.syslog "oauth2_proxy_logs" {
  listener {
    address  = "127.0.0.1:{{oauth2_proxy_syslog_port}}"
    protocol = "tcp"
    labels = { job = "oauth2-proxy", hostname = "{{inventory_hostname}}" }
  }
  forward_to = [loki.write.default.receiver]
}
```

### Deploy Alloy After Changes

If you update the Alloy configuration:
```bash
ansible-playbook alloy/deploy.yml --limit titania.incus
```

## Security Considerations

1. **Cookie Security**:
   - `cookie_secure = true` - HTTPS only
   - `cookie_httponly = true` - No JavaScript access
   - `cookie_samesite = "lax"` - CSRF protection

2. **Access Control**:
   - Use `oauth2_proxy_email_domains` to restrict by email domain
   - Use `oauth2_proxy_allowed_groups` to restrict by Casdoor groups

3. **SSL Verification**:
   - Set `oauth2_proxy_skip_ssl_verify: false` in production
   - Ensure Casdoor has valid SSL certificates

## Troubleshooting

### Check OAuth2-Proxy Logs
```bash
ssh titania.incus
docker logs oauth2-proxy
```

### Test OIDC Discovery
```bash
curl http://titania.incus:22081/.well-known/openid-configuration
```

### Verify Cookie Domain
Ensure `oauth2_proxy_cookie_domain` matches your HAProxy domain.

### Common Issues

| Issue | Cause | Solution |
|-------|-------|----------|
| Redirect loop | Cookie domain mismatch | Check `oauth2_proxy_cookie_domain` |
| 403 Forbidden | Email domain not allowed | Update `oauth2_proxy_email_domains` |
| OIDC discovery failed | Casdoor not accessible | Check network/firewall |
| Invalid redirect URI | Mismatch in Casdoor app | Verify redirect URL in Casdoor |

## Related Documentation

- [SearXNG Authentication](services/searxng-auth.md) - Specific implementation details
- [Casdoor Documentation](casdoor.md) - Identity provider configuration