Initial revision

main.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"crypto/subtle"
+	"log"
+	"net/http"
+	"net/http/httputil"
+	"net/url"
+	"os"
+)
+
+func main() {
+	target := mustEnv("PZ8_RELAY_TARGET_URL")
+	username := mustEnv("PZ8_RELAY_USERNAME")
+	password := mustEnv("PZ8_RELAY_PASSWORD")
+
+	addr := os.Getenv("PZ8_RELAY_LISTEN_ADDR")
+	if addr == "" {
+		addr = ":8080"
+	}
+
+	targetURL, err := url.Parse(target)
+	if err != nil {
+		log.Fatalf("invalid PZ8_RELAY_TARGET_URL: %v", err)
+	}
+
+	proxy := &httputil.ReverseProxy{
+		Rewrite: func(preq *httputil.ProxyRequest) {
+			preq.SetURL(targetURL)
+		},
+	}
+
+	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		u, p, ok := r.BasicAuth()
+		if !ok || subtle.ConstantTimeCompare([]byte(u), []byte(username)) != 1 ||
+			subtle.ConstantTimeCompare([]byte(p), []byte(password)) != 1 {
+			w.Header().Set("WWW-Authenticate", `Basic realm="pz8-relay"`)
+			http.Error(w, "unauthorized", http.StatusUnauthorized)
+			return
+		}
+		proxy.ServeHTTP(w, r)
+	})
+
+	log.Printf("pz8-relay listening on %s, proxying to %s", addr, targetURL.Redacted())
+	log.Fatal(http.ListenAndServe(addr, nil))
+}
+
+func mustEnv(key string) string {
+	v := os.Getenv(key)
+	if v == "" {
+		log.Fatalf("missing required env var: %s", key)
+	}
+	return v
+}