B-42: 导入功能加固——逐工作表确认、流式上传与诊断证据

src/bank_importer/reader.py

@@ -10,6 +10,23 @@ class UnsupportedWorkbookError(RuntimeError):
     pass
 
 
+class CorruptWorkbookError(RuntimeError):
+    """The file cannot be opened as a valid Excel workbook.
+
+    Raised for corrupt/truncated files, wrong signatures and files that
+    exceed the resource limits. The message is user-safe: it never contains
+    server-side paths or the content-addressed storage filename.
+    """
+
+
+# Workbook resource guards (defense against decompression bombs and
+# accidentally giant exports). Bank statements are small; these bounds are
+# generous enough for real exports while keeping memory bounded.
+MAX_SHEETS = 50
+MAX_ROWS_PER_SHEET = 200_000
+MAX_COLS_PER_SHEET = 64
+
+
 @dataclass(frozen=True)
 class RawSheet:
     name: str
@@ -18,11 +35,18 @@ class RawSheet:
 
 def read_workbook(path: Path) -> tuple[RawSheet, ...]:
     suffix = path.suffix.lower()
-    if suffix == ".xlsx":
-        return _read_xlsx(path)
-    if suffix == ".xls":
-        return _read_xls(path)
-    raise UnsupportedWorkbookError(f"Unsupported workbook type: {suffix}")
+    try:
+        if suffix == ".xlsx":
+            return _read_xlsx(path)
+        if suffix == ".xls":
+            return _read_xls(path)
+        raise UnsupportedWorkbookError(f"Unsupported workbook type: {suffix}")
+    except (UnsupportedWorkbookError, CorruptWorkbookError):
+        raise
+    except Exception as exc:
+        raise CorruptWorkbookError(
+            "文件无法读取，可能已损坏或不是有效的 Excel 文件。"
+        ) from exc
 
 
 def _read_xlsx(path: Path) -> tuple[RawSheet, ...]:
@@ -35,13 +59,24 @@ def _read_xlsx(path: Path) -> tuple[RawSheet, ...]:
 
     workbook = load_workbook(path, read_only=True, data_only=True)
     try:
-        return tuple(
-            RawSheet(
-                name=worksheet.title,
-                rows=tuple(tuple(row) for row in worksheet.iter_rows(values_only=True)),
-            )
-            for worksheet in workbook.worksheets
-        )
+        sheets: list[RawSheet] = []
+        for worksheet in workbook.worksheets:
+            rows: list[tuple[Any, ...]] = []
+            for row_index, row in enumerate(worksheet.iter_rows(values_only=True)):
+                if row_index >= MAX_ROWS_PER_SHEET:
+                    raise CorruptWorkbookError(
+                        f"工作表「{worksheet.title}」超过 {MAX_ROWS_PER_SHEET} 行，已拒绝读取。"
+                    )
+                values = tuple(row)
+                if len(values) > MAX_COLS_PER_SHEET:
+                    raise CorruptWorkbookError(
+                        f"工作表「{worksheet.title}」列数超过 {MAX_COLS_PER_SHEET}，已拒绝读取。"
+                    )
+                rows.append(values)
+            sheets.append(RawSheet(name=worksheet.title, rows=tuple(rows)))
+            if len(sheets) > MAX_SHEETS:
+                raise CorruptWorkbookError(f"工作簿工作表数量超过 {MAX_SHEETS} 个，已拒绝读取。")
+        return tuple(sheets)
     finally:
         workbook.close()
 
@@ -57,8 +92,19 @@ def _read_xls(path: Path) -> tuple[RawSheet, ...]:
     workbook = xlrd.open_workbook(path, on_demand=True)
     sheets: list[RawSheet] = []
     try:
-        for sheet_name in workbook.sheet_names():
+        names = workbook.sheet_names()
+        if len(names) > MAX_SHEETS:
+            raise CorruptWorkbookError(f"工作簿工作表数量超过 {MAX_SHEETS} 个，已拒绝读取。")
+        for sheet_name in names:
             worksheet = workbook.sheet_by_name(sheet_name)
+            if worksheet.nrows > MAX_ROWS_PER_SHEET:
+                raise CorruptWorkbookError(
+                    f"工作表「{sheet_name}」超过 {MAX_ROWS_PER_SHEET} 行，已拒绝读取。"
+                )
+            if worksheet.ncols > MAX_COLS_PER_SHEET:
+                raise CorruptWorkbookError(
+                    f"工作表「{sheet_name}」列数超过 {MAX_COLS_PER_SHEET}，已拒绝读取。"
+                )
             rows: list[tuple[Any, ...]] = []
             for row_index in range(worksheet.nrows):
                 values: list[Any] = []