Fix SQLite3 Cell data overflow reading for databases with header.reserved_size set

dissect/database/sqlite3/sqlite3.py

@@ -512,7 +512,6 @@ def data(self) -> bytes:
         if not self._data:
             offset = self._offset + self._record_offset
             page_data = self.page.data
-            page_size = self.page.sqlite.page_size
 
             if self.size <= self.max_payload_size:
                 size = max(self.size, 4)
@@ -545,7 +544,7 @@ def data(self) -> bytes:
                     # overflow_size is the size of the page data without the
                     # extra 4 bytes for the next overflow page, so it needs to
                     # be added.
-                    data_size = min(overflow_size + 4, page_size)
+                    data_size = min(overflow_size + 4, self.page.sqlite.usable_page_size)
                     page_buf = self.page.sqlite.raw_page(overflow_page)[:data_size]
 
                     overflow_page = c_sqlite3.uint32(page_buf[:4])

tests/sqlite3/test_sqlite3.py

@@ -6,6 +6,7 @@
 import pytest
 
 from dissect.database.sqlite3 import sqlite3
+from tests._util import absolute_path
 
 if TYPE_CHECKING:
     from pathlib import Path
@@ -93,3 +94,34 @@ def test_empty(empty_db: BinaryIO) -> None:
 
     assert s.encoding == "utf-8"
     assert len(list(s.tables())) == 0
+
+
+def test_cell_overflow_reserved_page_size_regression() -> None:
+    """Test if we handle databases with reserve_bytes greater than 0 correctly.
+
+    This test case emulates a database with a page size of 4kb and with reserve_bytes set to 32.
+    We then commit a row to a dummy table with a value of 8kb, forcing a cell overflow to a new page.
+
+    Test data generated using:
+
+        $ sqlite3 example.db
+        SQLite version 3.45.1 2024-01-30 16:01:20
+        Enter ".help" for usage hints.
+        sqlite> .filectrl reserve_bytes 32
+        32
+        sqlite> VACUUM;
+        sqlite> CREATE TABLE foo ("id" INTEGER PRIMARY KEY AUTOINCREMENT, "text" TEXT NOT NULL);
+        sqlite> .quit
+
+        $ python
+        >>> import sqlite3
+        >>> con = sqlite3.connect("example.db"); cur = con.cursor()
+        >>> cur.execute('INSERT INTO foo VALUES (1, ?)', ("A" * 8192,))
+        >>> con.commit(); con.close()
+    """
+
+    db = sqlite3.SQLite3(absolute_path("_data/sqlite3/overflow.db"))
+    assert db.header.reserved_size == 32
+    assert db.header.page_size == 4096
+    assert db.usable_page_size == db.header.page_size - db.header.reserved_size
+    assert db.table("foo").row(0).text == "A" * 8192