fix(execd): encode non-ASCII filenames in Content-Disposition header

components/execd/pkg/web/controller/filesystem_download.go

@@ -18,6 +18,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"net/url"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -55,7 +56,7 @@ func (c *FilesystemController) DownloadFile() {
 	}
 
 	c.ctx.Header("Content-Type", "application/octet-stream")
-	c.ctx.Header("Content-Disposition", "attachment; filename="+filepath.Base(filePath))
+	c.ctx.Header("Content-Disposition", formatContentDisposition(filepath.Base(filePath)))
 	c.ctx.Header("Content-Length", strconv.FormatInt(fileInfo.Size(), 10))
 
 	if rangeHeader := c.ctx.GetHeader("Range"); rangeHeader != "" {
@@ -81,3 +82,25 @@ func (c *FilesystemController) DownloadFile() {
 
 	http.ServeContent(c.ctx.Writer, c.ctx.Request, filepath.Base(filePath), fileInfo.ModTime(), file)
 }
+
+// formatContentDisposition formats the Content-Disposition header value with proper
+// encoding for non-ASCII filenames according to RFC 6266 and RFC 5987.
+func formatContentDisposition(filename string) string {
+	// Check if filename contains non-ASCII characters
+	needsEncoding := false
+	for _, r := range filename {
+		if r > 127 {
+			needsEncoding = true
+			break
+		}
+	}
+
+	if !needsEncoding {
+		return "attachment; filename=\"" + filename + "\""
+	}
+
+	// Use RFC 5987 encoding for non-ASCII filenames
+	// Format: attachment; filename="fallback"; filename*=UTF-8''encoded_name
+	encodedFilename := url.PathEscape(filename)
+	return "attachment; filename=\"" + encodedFilename + "\"; filename*=UTF-8''" + encodedFilename
+}

components/execd/pkg/web/controller/filesystem_test.go

@@ -118,3 +118,44 @@ func TestReplaceContentFailsUnknownFile(t *testing.T) {
 
 	require.Contains(t, []int{http.StatusNotFound, http.StatusInternalServerError}, rec.Code, "expected failure status")
 }
+
+func TestFormatContentDisposition(t *testing.T) {
+	tests := []struct {
+		name     string
+		filename string
+		want     string
+	}{
+		{
+			name:     "ASCII filename",
+			filename: "test.txt",
+			want:     "attachment; filename=\"test.txt\"",
+		},
+		{
+			name:     "Chinese filename",
+			filename: "测试文件.txt",
+			want:     "attachment; filename=\"%E6%B5%8B%E8%AF%95%E6%96%87%E4%BB%B6.txt\"; filename*=UTF-8''%E6%B5%8B%E8%AF%95%E6%96%87%E4%BB%B6.txt",
+		},
+		{
+			name:     "Japanese filename",
+			filename: "テスト.txt",
+			want:     "attachment; filename=\"%E3%83%86%E3%82%B9%E3%83%88.txt\"; filename*=UTF-8''%E3%83%86%E3%82%B9%E3%83%88.txt",
+		},
+		{
+			name:     "Special characters in filename",
+			filename: "file with spaces.txt",
+			want:     "attachment; filename=\"file with spaces.txt\"",
+		},
+		{
+			name:     "Mixed ASCII and non-ASCII",
+			filename: "report-报告.pdf",
+			want:     "attachment; filename=\"report-%E6%8A%A5%E5%91%8A.pdf\"; filename*=UTF-8''report-%E6%8A%A5%E5%91%8A.pdf",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := formatContentDisposition(tt.filename)
+			require.Equal(t, tt.want, got)
+		})
+	}
+}