feat: add fsx module and implement specific error for snap context

Author: emmanuelgautier

.github/workflows/ci.yml

@@ -2,8 +2,6 @@ name: CI
 
 on:
   push:
-    tags:
-      - "v*.*.*"
     branches:
       - main
   pull_request:

fsx/fsx.go

@@ -0,0 +1,33 @@
+package fsx
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+)
+
+var ErrSnapPermission = errors.New("permission denied: this binary was installed via snap which restricts filesystem access; please install using a different method (e.g. direct binary, docker, or package manager)")
+
+var ErrPermission = errors.New("permission denied: the process does not have access to read this file")
+
+func isSnapProcess() bool {
+	return os.Getenv("SNAP") != "" || os.Getenv("SNAP_NAME") != "" || strings.HasPrefix(os.Getenv("SNAP_USER_DATA"), "/home/")
+}
+
+func ReadFile(path string) ([]byte, error) {
+	data, err := os.ReadFile(path)
+	if err == nil {
+		return data, nil
+	}
+
+	if errors.Is(err, os.ErrPermission) {
+		if isSnapProcess() {
+			return nil, fmt.Errorf("%w: %s", ErrSnapPermission, path)
+		}
+
+		return nil, fmt.Errorf("%w: %s", ErrPermission, path)
+	}
+
+	return nil, err
+}

fsx/fsx_test.go

@@ -0,0 +1,84 @@
+package fsx_test
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/cerberauth/x/fsx"
+)
+
+func TestReadFile_Success(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "test.txt")
+	if err := os.WriteFile(path, []byte("hello"), 0600); err != nil {
+		t.Fatalf("failed to create test file: %v", err)
+	}
+
+	data, err := fsx.ReadFile(path)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if string(data) != "hello" {
+		t.Errorf("expected %q, got %q", "hello", string(data))
+	}
+}
+
+func TestReadFile_NotFound(t *testing.T) {
+	_, err := fsx.ReadFile("/nonexistent/path/file.txt")
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if errors.Is(err, fsx.ErrPermission) || errors.Is(err, fsx.ErrSnapPermission) {
+		t.Errorf("expected a not-found error, got permission error: %v", err)
+	}
+}
+
+func TestReadFile_PermissionDenied_Generic(t *testing.T) {
+	if os.Getuid() == 0 {
+		t.Skip("skipping permission test: running as root")
+	}
+
+	t.Setenv("SNAP", "")
+	t.Setenv("SNAP_NAME", "")
+	t.Setenv("SNAP_USER_DATA", "")
+
+	dir := t.TempDir()
+	path := filepath.Join(dir, "noaccess.txt")
+	if err := os.WriteFile(path, []byte("secret"), 0000); err != nil {
+		t.Fatalf("failed to create test file: %v", err)
+	}
+
+	_, err := fsx.ReadFile(path)
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if !errors.Is(err, fsx.ErrPermission) {
+		t.Errorf("expected ErrPermission, got: %v", err)
+	}
+}
+
+func TestReadFile_PermissionDenied_Snap(t *testing.T) {
+	if os.Getuid() == 0 {
+		t.Skip("skipping permission test: running as root")
+	}
+
+	t.Setenv("SNAP", "/snap/myapp/current")
+	t.Setenv("SNAP_NAME", "myapp")
+	t.Setenv("SNAP_USER_DATA", "")
+
+	dir := t.TempDir()
+	path := filepath.Join(dir, "noaccess.txt")
+	if err := os.WriteFile(path, []byte("secret"), 0000); err != nil {
+		t.Fatalf("failed to create test file: %v", err)
+	}
+
+	_, err := fsx.ReadFile(path)
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if !errors.Is(err, fsx.ErrSnapPermission) {
+		t.Errorf("expected ErrSnapPermission, got: %v", err)
+	}
+}