Refactor server routes

internal/server/auth/auth.go

@@ -0,0 +1,39 @@
+package auth
+
+import (
+	"crypto/sha256"
+	"crypto/subtle"
+	"net/http"
+
+	"git.a71.su/Andrew71/hibiscus-txt/internal/config"
+)
+
+// BasicAuth middleware handles authentication & authorization for the app.
+// It uses BasicAuth because I doubt there is a need for something sophisticated in a small hobby project.
+// Originally taken from Alex Edwards's https://www.alexedwards.net/blog/basic-authentication-in-go, MIT Licensed (13.03.2024).
+func BasicAuth(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		username, password, ok := r.BasicAuth()
+		if ok {
+			// Calculate SHA-256 hashes for equal length in ConstantTimeCompare
+			usernameHash := sha256.Sum256([]byte(username))
+			passwordHash := sha256.Sum256([]byte(password))
+			expectedUsernameHash := sha256.Sum256([]byte(config.Cfg.Username))
+			expectedPasswordHash := sha256.Sum256([]byte(config.Cfg.Password))
+
+			usernameMatch := subtle.ConstantTimeCompare(usernameHash[:], expectedUsernameHash[:]) == 1
+			passwordMatch := subtle.ConstantTimeCompare(passwordHash[:], expectedPasswordHash[:]) == 1
+
+			if usernameMatch && passwordMatch {
+				next.ServeHTTP(w, r)
+				return
+			} else {
+				noteLoginFail(username, password, r)
+			}
+		}
+
+		// Unauthorized, inform client that we have auth and return 401
+		w.Header().Set("WWW-Authenticate", `Basic realm="restricted", charset="UTF-8"`)
+		http.Error(w, "Unauthorized", http.StatusUnauthorized)
+	})
+}