test(migration): regression test for forged attachment size

Builds an in-memory export zip with a 2 MB payload and a data.json
that claims size: 0, then asserts neither the honest 2 MB row nor
the forged 0-size row ends up in the files table. Covers
GHSA-qh78-rvg3-cv54.

pkg/modules/migration/vikunja-file/vikunja_test.go

@@ -17,9 +17,12 @@
 package vikunjafile
 
 import (
+	"archive/zip"
+	"bytes"
 	"os"
 	"testing"
 
+	"code.vikunja.io/api/pkg/config"
 	"code.vikunja.io/api/pkg/db"
 	"code.vikunja.io/api/pkg/user"
 
@@ -74,6 +77,76 @@ func TestVikunjaFileMigrator_Migrate(t *testing.T) {
 			"created_by_id": u.ID,
 		}, false)
 	})
+	t.Run("rejects attachment with forged size smaller than content", func(t *testing.T) {
+		// Regression: GHSA-qh78-rvg3-cv54. Zip entry carries 2 MB of
+		// content but data.json claims size: 0, bypassing the 1 MB cap.
+		db.LoadAndAssertFixtures(t)
+
+		oldMax := config.FilesMaxSize.GetString()
+		config.FilesMaxSize.Set("1MB")
+		defer func() {
+			config.FilesMaxSize.Set(oldMax)
+			_ = config.SetMaxFileSizeMBytesFromString(oldMax)
+		}()
+		require.NoError(t, config.SetMaxFileSizeMBytesFromString("1MB"))
+
+		payload := make([]byte, 2*1024*1024)
+
+		dataJSON := `[{
+			"id": 1,
+			"title": "evil project",
+			"tasks": [{
+				"id": 1,
+				"title": "evil task",
+				"attachments": [{
+					"id": 1,
+					"file": {"id": 1, "name": "evil.bin", "size": 0}
+				}]
+			}],
+			"views": []
+		}]`
+
+		var zipBuf bytes.Buffer
+		zw := zip.NewWriter(&zipBuf)
+
+		vf, err := zw.Create("VERSION")
+		require.NoError(t, err)
+		_, err = vf.Write([]byte("dev"))
+		require.NoError(t, err)
+
+		df, err := zw.Create("data.json")
+		require.NoError(t, err)
+		_, err = df.Write([]byte(dataJSON))
+		require.NoError(t, err)
+
+		ff, err := zw.Create("files/1")
+		require.NoError(t, err)
+		_, err = ff.Write(payload)
+		require.NoError(t, err)
+
+		require.NoError(t, zw.Close())
+
+		m := &FileMigrator{}
+		u := &user.User{ID: 1}
+
+		reader := bytes.NewReader(zipBuf.Bytes())
+		err = m.Migrate(u, reader, int64(reader.Len()))
+
+		// create_from_structure.go skips the oversized attachment via
+		// `continue`, so Migrate succeeds for the rest of the project.
+		require.NoError(t, err)
+
+		// Forged 0-size row was the pre-fix outcome; assert neither
+		// size ends up persisted.
+		db.AssertMissing(t, "files", map[string]interface{}{
+			"name": "evil.bin",
+			"size": 2 * 1024 * 1024,
+		})
+		db.AssertMissing(t, "files", map[string]interface{}{
+			"name": "evil.bin",
+			"size": 0,
+		})
+	})
 	t.Run("should not accept an old import", func(t *testing.T) {
 		db.LoadAndAssertFixtures(t)