Geodata: Support automatically updating .dat files and hot reloading (#5992)

https://github.com/XTLS/Xray-core/pull/5992#issuecomment-4320551920

Usage: https://github.com/XTLS/Xray-core/pull/5992#issuecomment-4291168039

common/platform/filesystem/file.go

@@ -1,6 +1,7 @@
 package filesystem
 
 import (
+	"errors"
 	"io"
 	"os"
 	"path/filepath"
@@ -26,11 +27,48 @@ func ReadFile(path string) ([]byte, error) {
 }
 
 func ReadAsset(file string) ([]byte, error) {
-	return ReadFile(platform.GetAssetLocation(file))
+	path, _, err := getAssetFileLocation(file)
+	if err != nil {
+		return nil, err
+	}
+	return ReadFile(path)
 }
 
 func OpenAsset(file string) (io.ReadCloser, error) {
-	return NewFileReader(platform.GetAssetLocation(file))
+	path, _, err := getAssetFileLocation(file)
+	if err != nil {
+		return nil, err
+	}
+	return NewFileReader(path)
+}
+
+func StatAsset(file string) (os.FileInfo, error) {
+	_, info, err := getAssetFileLocation(file)
+	return info, err
+}
+
+func ResolveAsset(file string) (string, error) {
+	path, _, err := getAssetFileLocation(file)
+	return path, err
+}
+
+func getAssetFileLocation(file string) (string, os.FileInfo, error) {
+	if !filepath.IsLocal(file) || file == "." {
+		return "", nil, errors.New("asset path must stay in asset directory")
+	}
+	local, err := filepath.Localize(file)
+	if err != nil {
+		return "", nil, err
+	}
+	path := platform.GetAssetLocation(local)
+	info, err := os.Stat(path)
+	if err != nil {
+		return "", nil, err
+	}
+	if !info.Mode().IsRegular() {
+		return "", nil, errors.New("asset is not a regular file")
+	}
+	return path, info, nil
 }
 
 func ReadCert(file string) ([]byte, error) {

common/platform/filesystem/file_test.go

@@ -0,0 +1,32 @@
+package filesystem_test
+
+import (
+	"path/filepath"
+	"testing"
+
+	. "github.com/xtls/xray-core/common/platform/filesystem"
+)
+
+func TestStatAssetRejectsInvalidPath(t *testing.T) {
+	for _, file := range []string{
+		"",
+		".",
+		"..",
+		"../geoip.dat",
+		"nested/..",
+		"nested/../geoip.dat",
+		"nested//geoip.dat",
+		"/geoip.dat",
+		"/tmp/geoip.dat",
+		`C:\geoip.dat`,
+		`C:geoip.dat`,
+		`\\server\share\geoip.dat`,
+		`nested\geoip.dat`,
+		`nested\..\geoip.dat`,
+		filepath.Join(t.TempDir(), "geoip.dat"),
+	} {
+		if _, err := StatAsset(file); err == nil {
+			t.Fatalf("expected error for %q", file)
+		}
+	}
+}