[Autofix][high] Alert #1: Time-of-check time-of-use filesystem race condition

[xengine-qyt]

🤖 Copilot Autofix 自动修复报告

---

📋 基本信息

字段	内容
Alert ID	#1
安全级别	high
规则名称	Time-of-check time-of-use filesystem race condition
问题文件	XEngine_Source/StorageModule_Session/Session_Stroage/Session_UPStroage.cpp 第 161 行
CWE 分类	external/cwe/cwe-367
规则标签	external/cwe/cwe-367, security

---

🔍 问题说明

Time-of-check time-of-use filesystem race condition

Often it is necessary to check the state of a file before using it. These checks usually take a file name to be checked, and if the check returns positively, then the file is opened or otherwise operated upon.

However, in the time between the check and the operation, the underlying file referenced by the file name could be changed by an attacker, causing unexpected behavior.

Recommendation

Wherever possible, use functions that operate on file descriptors rather than file names (for example, fchmod rather than chmod).

For access checks, you can temporarily change the UID and GID to that of the user whose permissions are being checked, and then perform the operation. This has the effect of "atomically" combining a permissions c

---

🤖 AI 修复思路

General fix: remove path-based pre-checks (access/stat) before open, and instead open first, then validate/inspect through the opened handle (or descriptor). This collapses check+use into one operation on the same object.

Best fix in this snippet:

• In XEngine_Source/StorageModule_Session/Session_Stroage/Session_UPStroage.cpp, replace the _xtaccess-gated block with logic that:
  1. Enters resume branch based on resume flags only.
  2. Attempts _xtfopen(lpszFileDir, _X("rb+")) directly.
  3. If open fails, return existing open-file error.
  4. If open succeeds, obtain size from the opened stream via fseek(..., SEEK_END) + ftell(...), then restore position with fseek(..., SEEK_SET).
• This removes the TOCTOU window caused by _xtaccess/_xtstat before open while keeping behavior (must exist + read/write open for resume, and using file length for overwrite logic).

No new imports or dependencies are required.

---

✅ Review 检查清单

• 理解了漏洞的成因和影响范围
• 确认 AI 修复逻辑正确，没有遗漏边界情况
• 确认修复没有改变原有业务逻辑
• 确认没有引入新的安全问题
• CI / 单元测试全部通过
• 如有必要，已补充对应的测试用例

---

此 PR 由 GitHub Copilot Autofix 自动生成，请仔细审核后再 merge。