638 lines
15 KiB
Markdown
638 lines
15 KiB
Markdown
# Forward Auth TOTP
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A lightweight forward authentication service for Caddy (or any reverse proxy) that uses TOTP (Time-based One-Time Password) tokens for user authentication.
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## Features
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- 🔐 TOTP-based authentication (compatible with Google Authenticator, Authy, 1Password, etc.)
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- 🎫 JWT session management with configurable duration (default: 24 hours)
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- 🛡️ Built-in rate limiting (5 attempts per 15 minutes)
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- 👥 Support for multiple users (1-20+ TOTP seeds)
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- 🪶 Lightweight SQLite database
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- 🚀 Single binary deployment
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- 🔄 Works with Caddy's `forward_auth` directive
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- 📱 Mobile-friendly login page
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- 🔒 Secure by default with HTTPS cookie settings
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## Prerequisites
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- Go 1.21 or higher
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- SQLite3
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- Caddy v2 (or any reverse proxy that supports forward authentication)
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## Installation
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### Clone the repository
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```bash
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git clone https://github.com/yourusername/forward-auth-totp.git
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cd forward-auth-totp
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```
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### Install dependencies
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```bash
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go mod download
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```
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### Build the application
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```bash
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go build -o forward-auth main.go
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```
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## Configuration
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### Environment Variables
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| Variable | Description | Default | Required |
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|----------|-------------|---------|----------|
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| `JWT_SECRET` | Secret key for signing JWT tokens | None | **Yes** |
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**Important:** The `JWT_SECRET` environment variable is **required**. The application will not start without it.
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Generate a secure secret:
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```bash
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openssl rand -base64 32
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```
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Set it before running:
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```bash
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export JWT_SECRET="your-very-secure-random-secret-here-min-32-chars"
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```
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### Application Constants
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You can modify these constants in `main.go` if needed:
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| Constant | Description | Default |
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|----------|-------------|---------|
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| `sessionDuration` | JWT session duration | 24 hours |
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| `dbFile` | SQLite database file path | `auth.db` |
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| `jwtCookie` | Cookie name for JWT token | `auth_token` |
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| `maxLoginAttempts` | Maximum failed login attempts | 5 |
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| `rateLimitWindow` | Rate limit time window | 15 minutes |
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## Usage
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### First Run
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On first run, the application will automatically generate a TOTP seed:
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```bash
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export JWT_SECRET="$(openssl rand -base64 32)"
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./forward-auth
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```
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Output:
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```
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No seeds found, generating one...
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New TOTP seed generated:
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Secret: JBSWY3DPEHPK3PXP
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OTPAuth URL: otpauth://totp/ForwardAuthApp:user?secret=JBSWY3DPEHPK3PXP&issuer=ForwardAuthApp
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Use this to set up your authenticator app.
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Starting auth server on :3000
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```
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**Add to Authenticator App:**
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1. Open your authenticator app (Google Authenticator, Authy, 1Password, etc.)
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2. Scan the QR code (generate one from the OTPAuth URL) or manually enter the secret
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3. Use the 6-digit code to log in
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### Generate Additional TOTP Seeds
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For multiple users, generate additional seeds:
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```bash
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./forward-auth -generate
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```
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Each seed represents a separate user. The application will check all seeds when validating OTP codes.
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### Running as a Service
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#### systemd (Linux)
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Create `/etc/systemd/system/forward-auth.service`:
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```ini
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[Unit]
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Description=Forward Auth TOTP Service
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After=network.target
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[Service]
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Type=simple
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User=www-data
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WorkingDirectory=/opt/forward-auth
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Environment="JWT_SECRET=your-secure-secret-here-change-this"
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ExecStart=/opt/forward-auth/forward-auth
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Restart=on-failure
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RestartSec=5s
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# Security hardening
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NoNewPrivileges=true
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PrivateTmp=true
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ProtectSystem=strict
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ProtectHome=true
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ReadWritePaths=/opt/forward-auth
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[Install]
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WantedBy=multi-user.target
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```
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Deploy and start:
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```bash
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sudo mkdir -p /opt/forward-auth
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sudo cp forward-auth /opt/forward-auth/
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sudo chown -R www-data:www-data /opt/forward-auth
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sudo chmod 600 /opt/forward-auth/auth.db # After first run
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sudo systemctl enable forward-auth
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sudo systemctl start forward-auth
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sudo systemctl status forward-auth
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```
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#### Docker (Optional)
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Create `Dockerfile`:
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```dockerfile
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FROM golang:1.21-alpine AS builder
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WORKDIR /app
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COPY go.mod go.sum ./
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RUN go mod download
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COPY main.go ./
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RUN go build -o forward-auth main.go
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FROM alpine:latest
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RUN apk --no-cache add ca-certificates sqlite
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WORKDIR /root/
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COPY --from=builder /app/forward-auth .
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EXPOSE 3000
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CMD ["./forward-auth"]
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```
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Build and run:
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```bash
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docker build -t forward-auth .
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docker run -d \
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-p 3000:3000 \
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-v $(pwd)/data:/root \
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-e JWT_SECRET="your-secret-here" \
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--name forward-auth \
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forward-auth
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```
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## Caddy Configuration
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### Basic Configuration
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```caddyfile
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# Your protected application
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app.example.com {
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forward_auth localhost:3000 {
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uri /verify
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copy_headers X-Original-URI
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}
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reverse_proxy localhost:8080
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}
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# Auth service (optional, if you want login page accessible externally)
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auth.example.com {
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reverse_proxy localhost:3000
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}
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```
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### Recommended Configuration with Login Page Access
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```caddyfile
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app.example.com {
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# Allow unauthenticated access to login page
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@login {
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path /login*
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}
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handle @login {
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reverse_proxy localhost:3000
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}
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# Protect all other routes
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forward_auth localhost:3000 {
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uri /verify
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copy_headers X-Original-URI
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}
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reverse_proxy localhost:8080
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}
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```
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### Multiple Protected Services (Shared Authentication)
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```caddyfile
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# Auth service
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auth.example.com {
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reverse_proxy localhost:3000
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}
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# Protected app 1
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app1.example.com {
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forward_auth auth.example.com {
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uri /verify
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copy_headers X-Original-URI
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}
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reverse_proxy localhost:8080
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}
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# Protected app 2
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app2.example.com {
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forward_auth auth.example.com {
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uri /verify
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copy_headers X-Original-URI
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}
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reverse_proxy localhost:8081
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}
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```
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### With SSL/TLS
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```caddyfile
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app.example.com {
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# Automatic HTTPS via Caddy
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forward_auth localhost:3000 {
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uri /verify
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copy_headers X-Original-URI
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}
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reverse_proxy localhost:8080
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}
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```
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## API Endpoints
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| Endpoint | Method | Description |
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|----------|--------|-------------|
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| `/verify` | GET | Verify JWT token (used by forward auth) |
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| `/login` | GET | Display login form |
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| `/login` | POST | Process OTP submission |
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| `/health` | GET | Health check endpoint |
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### Endpoint Details
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#### GET /verify
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Returns:
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- `204 No Content` - Valid authentication
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- `302 Found` - Redirect to login (with `?next=` parameter)
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#### GET /login
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Query parameters:
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- `next` (optional) - Redirect URL after successful login
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#### POST /login
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Form parameters:
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- `otp` (required) - 6-digit TOTP code
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- `next` (optional) - Redirect URL after successful login
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Returns:
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- `302 Found` - Successful login, redirects to `next` URL
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- `401 Unauthorized` - Invalid OTP
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- `429 Too Many Requests` - Rate limit exceeded
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#### GET /health
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Returns:
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- `200 OK` - Service is healthy
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## Security Features
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### Rate Limiting
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The application includes built-in rate limiting to prevent brute force attacks:
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- **Maximum attempts:** 5 failed login attempts
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- **Time window:** 15 minutes
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- **Per IP address tracking**
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- **Automatic cleanup:** Old entries removed every 5 minutes
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- **Reset on success:** Successful login clears rate limit for that IP
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When rate limited, users see: "Too many failed attempts. Try again in 15 minutes."
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### Cookie Security
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Cookies are configured with security best practices:
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- `HttpOnly: true` - Prevents JavaScript access
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- `Secure: true` - HTTPS only (requires SSL/TLS)
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- `SameSite: Lax` - CSRF protection
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- `Path: /` - Available to all routes
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### Open Redirect Protection
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The application validates redirect URLs to prevent open redirect attacks. Only relative URLs starting with `/` are allowed.
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### JWT Security
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- Tokens are signed with HS256
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- Include expiration time (`exp`)
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- Include issued at time (`iat`)
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- Validated on every request
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## Security Checklist
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### Production Deployment
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- [x] Set a strong `JWT_SECRET` (32+ characters, random)
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- [x] HTTPS enabled (Caddy handles this automatically)
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- [x] Cookie `Secure` flag enabled (already set in code)
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- [x] Rate limiting active (built-in, 5 attempts per 15 min)
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- [ ] Restrict database file permissions: `chmod 600 auth.db`
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- [ ] Run service as non-root user
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- [ ] Keep TOTP secrets backed up securely
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- [ ] Monitor logs for suspicious activity
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- [ ] Set up log rotation
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- [ ] Consider firewall rules to restrict port 3000
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### Additional Recommendations
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1. **Backup TOTP seeds:** Store them securely (e.g., password manager)
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2. **Time synchronization:** Ensure server time is accurate (use NTP)
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3. **Monitoring:** Set up alerts for repeated failed login attempts
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4. **Updates:** Keep Go and dependencies updated
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5. **Logs:** Review logs regularly for anomalies
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## Database Management
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### Backup
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```bash
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# Simple backup
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cp auth.db auth.db.backup
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# Timestamped backup
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cp auth.db "auth.db.backup.$(date +%Y%m%d_%H%M%S)"
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# Automated daily backup (cron)
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0 2 * * * cp /opt/forward-auth/auth.db "/opt/forward-auth/backups/auth.db.$(date +\%Y\%m\%d)"
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```
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### View All Seeds
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```bash
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sqlite3 auth.db "SELECT id, secret FROM seeds;"
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```
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### Count Seeds
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```bash
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sqlite3 auth.db "SELECT COUNT(*) FROM seeds;"
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```
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### Remove a Specific Seed
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```bash
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# By ID
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sqlite3 auth.db "DELETE FROM seeds WHERE id = 1;"
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# By secret (first few characters)
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sqlite3 auth.db "DELETE FROM seeds WHERE secret LIKE 'JBSWY%';"
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```
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### Reset Database
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```bash
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rm auth.db
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./forward-auth # Will generate a new seed automatically
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```
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## Troubleshooting
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### "Invalid OTP" Error
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**Causes:**
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- Device time not synchronized (TOTP is time-sensitive)
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- Wrong seed in authenticator app
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- OTP code expired (valid for 30 seconds)
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**Solutions:**
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```bash
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# Check server time
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date
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# Sync time (Linux)
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sudo ntpdate pool.ntp.org
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# or
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sudo timedatectl set-ntp true
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# Verify database has seeds
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sqlite3 auth.db "SELECT COUNT(*) FROM seeds;"
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```
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### "Too many failed attempts"
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This is the rate limiting feature. Wait 15 minutes or:
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```bash
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# Check current rate limits (requires modifying code to expose this)
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# For now, restart the service to clear in-memory rate limits
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sudo systemctl restart forward-auth
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```
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### Authentication Not Working
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```bash
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# Check if service is running
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sudo systemctl status forward-auth
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# Check service logs
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sudo journalctl -u forward-auth -f
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# Check Caddy logs
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sudo journalctl -u caddy -f
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# Verify health endpoint
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curl http://localhost:3000/health
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# Test verify endpoint
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curl -v http://localhost:3000/verify
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```
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### Cookie Not Persisting
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**Checklist:**
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- [ ] Using HTTPS in production (required for `Secure: true`)
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- [ ] Cookie domain matches your setup
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- [ ] Browser accepts cookies
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- [ ] No browser extensions blocking cookies
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- [ ] Clock skew between client and server
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### JWT_SECRET Not Set Error
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```
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JWT_SECRET environment variable must be set!
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```
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**Solution:**
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```bash
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# Generate a secret
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export JWT_SECRET="$(openssl rand -base64 32)"
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# Or set permanently in systemd service file
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sudo systemctl edit forward-auth
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# Add: Environment="JWT_SECRET=your-secret-here"
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```
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### Database Locked Error
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```bash
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# Check if file is being accessed by another process
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lsof auth.db
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# Ensure proper permissions
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sudo chown www-data:www-data auth.db
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sudo chmod 600 auth.db
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```
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## Performance
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This application is designed for light usage:
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| Metric | Value |
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|--------|-------|
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| Memory footprint | ~10-15 MB |
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| CPU usage | <1% (idle), ~2-3% (under load) |
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| Database size | <1 KB per seed (~20 KB for 20 seeds) |
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| Startup time | <100ms |
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| Request latency | <10ms (local), <50ms (network) |
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| Max throughput | 1000+ req/sec (limited by SQLite) |
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**Tested scenarios:**
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- 4 users, <100 requests/day: Negligible resource usage
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- 20 users, 500 requests/day: <5 MB memory, <1% CPU
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## Development
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### Run in Development Mode
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```bash
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export JWT_SECRET="dev-secret-do-not-use-in-production"
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go run main.go
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```
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### Enable Debug Logging
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Modify `main.go` to add debug logs:
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```go
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log.SetFlags(log.LstdFlags | log.Lshortfile)
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```
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### Test Rate Limiting
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```bash
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# Automated testing
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for i in {1..6}; do
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curl -X POST http://localhost:3000/login \
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-d "otp=000000" \
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-d "next=/"
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echo "Attempt $i"
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done
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```
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### Build for Different Platforms
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```bash
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# Linux (amd64)
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GOOS=linux GOARCH=amd64 go build -o forward-auth-linux-amd64 main.go
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# Linux (arm64) - for Raspberry Pi, etc.
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GOOS=linux GOARCH=arm64 go build -o forward-auth-linux-arm64 main.go
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# macOS (Intel)
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GOOS=darwin GOARCH=amd64 go build -o forward-auth-macos-amd64 main.go
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# macOS (Apple Silicon)
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GOOS=darwin GOARCH=arm64 go build -o forward-auth-macos-arm64 main.go
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# Windows
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GOOS=windows GOARCH=amd64 go build -o forward-auth.exe main.go
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```
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### Static Binary (no external dependencies)
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```bash
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CGO_ENABLED=1 go build -ldflags="-s -w" -o forward-auth main.go
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```
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## Monitoring
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### Log Examples
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Successful login:
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```
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2025/11/04 10:23:45 Starting auth server on :3000
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```
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Failed login attempt:
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```
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(Rate limiting is handled silently, check HTTP 429 responses in reverse proxy logs)
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```
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### Prometheus Metrics (Future Enhancement)
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Currently not implemented. Consider adding metrics for:
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- Total authentication attempts
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- Failed authentication attempts
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- Rate limit hits
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- Active sessions
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- Request latency
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## Migration
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### From Other Auth Systems
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To migrate users:
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1. Generate a new TOTP seed: `./forward-auth -generate`
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2. Provide the seed to each user
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3. Users add it to their authenticator app
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4. Test login before decommissioning old system
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### Updating JWT Secret
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```bash
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# 1. Generate new secret
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NEW_SECRET=$(openssl rand -base64 32)
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# 2. Update environment variable
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export JWT_SECRET="$NEW_SECRET"
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# 3. Restart service
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sudo systemctl restart forward-auth
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# Note: All existing sessions will be invalidated
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```
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## Contributing
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Contributions are welcome! Please feel free to submit a Pull Request.
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### Areas for Improvement
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- [ ] Admin API for seed management
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- [ ] Web UI for seed generation
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- [ ] Prometheus metrics endpoint
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- [ ] Failed login attempt logging/auditing
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- [ ] Multiple database backend support
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- [ ] Session revocation
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- [ ] Account-specific rate limiting
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## License
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MIT License - see LICENSE file for details
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## Acknowledgments
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- [golang-jwt/jwt](https://github.com/golang-jwt/jwt) - JWT implementation
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- [pquerna/otp](https://github.com/pquerna/otp) - TOTP implementation
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- [mattn/go-sqlite3](https://github.com/mattn/go-sqlite3) - SQLite driver
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- [Caddy](https://caddyserver.com/) - Modern web server with automatic HTTPS
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## Support
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For issues and questions:
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- Open an issue on GitHub
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- Check existing issues for solutions
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- Review the troubleshooting section above
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## FAQ
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**Q: Can I use this with Nginx or Traefik?**
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A: Yes! Any reverse proxy that supports forward authentication will work. You'll need to configure it to send requests to the `/verify` endpoint.
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**Q: How do I revoke a user's access?**
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A: Delete their TOTP seed from the database: `sqlite3 auth.db "DELETE FROM seeds WHERE id = X;"`
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**Q: Can I change the session duration?**
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A: Yes, modify the `sessionDuration` constant in `main.go` and rebuild.
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**Q: Is this suitable for production?**
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A: Yes, for small deployments (1-20 users). For larger deployments, consider enterprise authentication solutions.
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**Q: What happens if I lose the database?**
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A: You'll need to regenerate seeds and have users re-add them to their authenticator apps. Keep backups!
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**Q: Can I use this without Caddy?**
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A: Yes! It works with any reverse proxy that supports forward authentication (Nginx, Traefik, HAProxy, etc.).
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---
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**Note:** This is a lightweight authentication service designed for personal or small team use. For enterprise deployments, consider solutions with additional features like SSO, LDAP integration, audit logging, and compliance certifications. |