fix(localio): reject special files before open

internal/localio/input.go

@@ -15,6 +15,7 @@ const defaultTextInputLimit = int64(8 << 20)
 
 var (
 	readTextInputAll  = io.ReadAll
+	statTextInputPath = os.Stat
 	openTextInputFile = os.Open
 	readTextInputRel  = filepath.Rel
 )
@@ -72,6 +73,16 @@ func ReadTextInput(spec string, stdin io.Reader, maxBytes int64) (string, error)
 	if err != nil || rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) || filepath.IsAbs(rel) {
 		return "", fmt.Errorf("LOCAL_INPUT_UNSAFE: @file 解析后逃逸工作目录")
 	}
+	pathInfo, err := statTextInputPath(realPath)
+	if err != nil {
+		return "", fmt.Errorf("LOCAL_INPUT_READ_FAILED: %w", err)
+	}
+	if !pathInfo.Mode().IsRegular() {
+		return "", fmt.Errorf("LOCAL_INPUT_INVALID: @file 必须是普通文件")
+	}
+	if pathInfo.Size() > maxBytes {
+		return "", fmt.Errorf("LOCAL_INPUT_TOO_LARGE: 文件大小 %d 超过 %d 字节", pathInfo.Size(), maxBytes)
+	}
 	file, err := openTextInputFile(realPath)
 	if err != nil {
 		return "", fmt.Errorf("LOCAL_INPUT_READ_FAILED: %w", err)

internal/localio/input_bounds_test.go

@@ -72,4 +72,54 @@ func TestCrossPlatformCoverageReadTextInputUsesOpenedDescriptorAndBoundedReadE2E
 			t.Fatal("file growth bypassed size limit")
 		}
 	})
+
+	t.Run("path becomes directory before descriptor check", func(t *testing.T) {
+		path := filepath.Join(dir, "becomes-directory.txt")
+		if err := os.WriteFile(path, []byte("safe"), 0o600); err != nil {
+			t.Fatal(err)
+		}
+		testseam.Swap(t, &openTextInputFile, func(candidate string) (*os.File, error) {
+			if removeErr := os.Remove(candidate); removeErr != nil {
+				return nil, removeErr
+			}
+			if mkdirErr := os.Mkdir(candidate, 0o700); mkdirErr != nil {
+				return nil, mkdirErr
+			}
+			return os.Open(candidate)
+		})
+		if _, err := ReadTextInput("@becomes-directory.txt", nil, 10); err == nil {
+			t.Fatal("path type replacement bypassed descriptor validation")
+		}
+	})
+
+	t.Run("file grows before descriptor check", func(t *testing.T) {
+		path := filepath.Join(dir, "grows-before-stat.txt")
+		if err := os.WriteFile(path, []byte("ok"), 0o600); err != nil {
+			t.Fatal(err)
+		}
+		testseam.Swap(t, &openTextInputFile, func(candidate string) (*os.File, error) {
+			file, openErr := os.Open(candidate)
+			if openErr != nil {
+				return nil, openErr
+			}
+			writer, writeOpenErr := os.OpenFile(candidate, os.O_APPEND|os.O_WRONLY, 0)
+			if writeOpenErr != nil {
+				_ = file.Close()
+				return nil, writeOpenErr
+			}
+			if _, writeErr := writer.WriteString("-too-large"); writeErr != nil {
+				_ = writer.Close()
+				_ = file.Close()
+				return nil, writeErr
+			}
+			if closeErr := writer.Close(); closeErr != nil {
+				_ = file.Close()
+				return nil, closeErr
+			}
+			return file, nil
+		})
+		if _, err := ReadTextInput("@grows-before-stat.txt", nil, 4); err == nil {
+			t.Fatal("pre-open growth bypassed descriptor size validation")
+		}
+	})
 }

internal/localio/input_fifo_unix_test.go

@@ -0,0 +1,46 @@
+//go:build unix
+
+// Copyright 2026 Alibaba Group
+// Licensed under the Apache License, Version 2.0
+
+package localio
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"syscall"
+	"testing"
+	"time"
+)
+
+func TestCrossPlatformCoverageReadTextInputRejectsUnconnectedFIFOWithoutBlockingE2E(t *testing.T) {
+	dir := t.TempDir()
+	old, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Chdir(dir); err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = os.Chdir(old) })
+
+	fifo := filepath.Join(dir, "input.fifo")
+	if err := syscall.Mkfifo(fifo, 0o600); err != nil {
+		t.Fatal(err)
+	}
+	result := make(chan error, 1)
+	go func() {
+		_, readErr := ReadTextInput("@input.fifo", nil, 1024)
+		result <- readErr
+	}()
+
+	select {
+	case err := <-result:
+		if err == nil || !strings.Contains(err.Error(), "LOCAL_INPUT_INVALID") {
+			t.Fatalf("FIFO rejection error = %v", err)
+		}
+	case <-time.After(time.Second):
+		t.Fatal("FIFO without a writer blocked text input validation")
+	}
+}

internal/localio/input_test.go

@@ -106,6 +106,9 @@ func TestCrossPlatformCoverageReadTextInputFailureBranchesE2E(t *testing.T) {
 		"relative": func(t *testing.T) {
 			testseam.Swap(t, &readTextInputRel, func(string, string) (string, error) { return "", errors.New("rel") })
 		},
+		"path stat": func(t *testing.T) {
+			testseam.Swap(t, &statTextInputPath, func(string) (os.FileInfo, error) { return nil, errors.New("stat") })
+		},
 		"open": func(t *testing.T) {
 			testseam.Swap(t, &openTextInputFile, func(string) (*os.File, error) { return nil, errors.New("open") })
 		},