Jarvis/internal/server/server.go

// Package server wires jarvis's HTTP surface: the Grafana webhook
// receiver, a background diagnostic worker, and the authenticated Atom feed.
package server

import (
	"crypto/subtle"
	"net/http"
)

// Config holds the server's runtime configuration.
type Config struct {
	// WebhookToken authenticates Grafana -> jarvis on POST /webhook/grafana.
	// Sent by Grafana as a Bearer token (Authorization: Bearer <token>).
	WebhookToken string
	// FeedUser / FeedPassword gate the Atom feed with HTTP Basic auth
	// (what miniflux connects with).
	FeedUser     string
	FeedPassword string
	// FeedTitle / FeedID / BaseURL describe the feed document.
	FeedTitle string
	FeedID    string
	BaseURL   string
	// FeedLimit caps how many entries the feed serves.
	FeedLimit int
}

// bearerAuth wraps h, requiring "Authorization: Bearer <token>". If token is
// empty the endpoint is left open (useful for local dev only).
func bearerAuth(token string, h http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if token != "" {
			const prefix = "Bearer "
			got := r.Header.Get("Authorization")
			if len(got) <= len(prefix) ||
				subtle.ConstantTimeCompare([]byte(got[len(prefix):]), []byte(token)) != 1 {
				http.Error(w, "unauthorized", http.StatusUnauthorized)
				return
			}
		}
		h(w, r)
	}
}

// basicAuth wraps h with HTTP Basic auth. If user is empty the endpoint is
// left open (local dev only).
func basicAuth(user, pass string, h http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if user != "" {
			u, p, ok := r.BasicAuth()
			userOK := subtle.ConstantTimeCompare([]byte(u), []byte(user)) == 1
			passOK := subtle.ConstantTimeCompare([]byte(p), []byte(pass)) == 1
			if !ok || !userOK || !passOK {
				w.Header().Set("WWW-Authenticate", `Basic realm="jarvis"`)
				http.Error(w, "unauthorized", http.StatusUnauthorized)
				return
			}
		}
		h(w, r)
	}
}