fix(security): trusted-proxy-scoped login rate limit

backend/internal/config/config.go

@@ -5,20 +5,22 @@ import (
 	"os"
 	"path/filepath"
 	"strconv"
+	"strings"
 	"time"
 )
 
 type Config struct {
-	Addr          string
-	DatabaseURL   string
-	RedisURL      string
-	JWTSecret     []byte
-	AdminUser     string
-	AdminPassword string
-	BooksDir      string
-	CacheDir      string
-	ScanInterval  time.Duration
-	UploadMaxMB   int64
+	Addr           string
+	DatabaseURL    string
+	RedisURL       string
+	JWTSecret      []byte
+	AdminUser      string
+	AdminPassword  string
+	BooksDir       string
+	CacheDir       string
+	ScanInterval   time.Duration
+	UploadMaxMB    int64
+	TrustedProxies []string
 }
 
 func Load() (*Config, error) {
@@ -28,6 +30,16 @@ func Load() (*Config, error) {
 		}
 		return def
 	}
+	envList := func(k, def string) []string {
+		v := env(k, def)
+		out := make([]string, 0, len(strings.Split(v, ",")))
+		for _, s := range strings.Split(v, ",") {
+			if s = strings.TrimSpace(s); s != "" {
+				out = append(out, s)
+			}
+		}
+		return out
+	}
 	scanSec, err := strconv.Atoi(env("SCAN_INTERVAL_SEC", "60"))
 	if err != nil {
 		return nil, fmt.Errorf("SCAN_INTERVAL_SEC: %w", err)
@@ -49,15 +61,16 @@ func Load() (*Config, error) {
 		return dir
 	}
 	return &Config{
-		Addr:          env("ADDR", ":8080"),
-		DatabaseURL:   env("DATABASE_URL", ""),
-		RedisURL:      env("REDIS_URL", ""),
-		JWTSecret:     []byte(secret),
-		AdminUser:     env("ADMIN_USER", ""),
-		AdminPassword: env("ADMIN_PASSWORD", ""),
-		BooksDir:      resolveDir(env("BOOKS_DIR", "/data/books")),
-		CacheDir:      resolveDir(env("CACHE_DIR", "/data/cache")),
-		ScanInterval:  time.Duration(scanSec) * time.Second,
-		UploadMaxMB:   uploadMB,
+		Addr:           env("ADDR", ":8080"),
+		DatabaseURL:    env("DATABASE_URL", ""),
+		RedisURL:       env("REDIS_URL", ""),
+		JWTSecret:      []byte(secret),
+		AdminUser:      env("ADMIN_USER", ""),
+		AdminPassword:  env("ADMIN_PASSWORD", ""),
+		BooksDir:       resolveDir(env("BOOKS_DIR", "/data/books")),
+		CacheDir:       resolveDir(env("CACHE_DIR", "/data/cache")),
+		ScanInterval:   time.Duration(scanSec) * time.Second,
+		UploadMaxMB:    uploadMB,
+		TrustedProxies: envList("TRUSTED_PROXY_CIDRS", "172.16.0.0/12"),
 	}, nil
 }