fix(mcp): reject control characters in FinDrive filenames

finbot/mcp/servers/findrive/server.py

@@ -59,6 +59,9 @@ def upload_file(
         if len(content.encode("utf-8")) > max_size:
             return {"error": f"File exceeds maximum size of {config.get('max_file_size_kb', 500)}KB"}
 
+        if any(c in filename for c in ("\n", "\r", "\t", "\x00")):
+            return {"error": "filename contains invalid control characters"}
+
         with db_session() as db:
             repo = FinDriveFileRepository(db, session_context)
 

tests/unit/mcp/test_findrive.py

@@ -0,0 +1,102 @@
+"""Tests for FinDrive's upload_file filename validation.
+
+GitHub issue #360 (Bug_151_MUST_FIX, FD-FNAME-003): upload_file passes
+filename straight through to repo.create_file with no control-character
+filtering, and separately logs it verbatim via logger.info -- a filename
+containing a newline is stored verbatim in the DB and, more importantly,
+injects a fake log line into the application log, corrupting the audit
+trail (a real log-injection vector, not just data hygiene).
+
+Verified against source before writing anything: finbot/mcp/servers/
+findrive/server.py's upload_file (create_findrive_server) has no
+validation on filename at all beyond the file-size check.
+"""
+
+import pytest
+
+from finbot.core.auth.session import session_manager
+from finbot.mcp.servers.findrive.server import create_findrive_server
+
+
+@pytest.fixture
+def session_context(db):
+    return session_manager.create_session(email="findrive_test@example.com")
+
+
+async def _upload_file(session_context, **kwargs):
+    mcp = create_findrive_server(session_context)
+    tool = await mcp.get_tool("upload_file")
+    return tool.fn(**kwargs)
+
+
+class TestFileNameValidation:
+
+    @pytest.mark.unit
+    @pytest.mark.asyncio
+    async def test_fd_fname_003_newline_in_filename_enables_log_injection(
+        self, db, session_context
+    ):
+        """Name matches GitHub issue #360's own specified acceptance-criteria
+        test name verbatim (kept for traceability back to the issue) --
+        describes the VULNERABILITY this guards against, not the assertion
+        direction: the test asserts the injection is now rejected."""
+        result = await _upload_file(
+            session_context,
+            filename="legit.pdf\nFAKE LOG ENTRY: admin login from 1.2.3.4",
+            content="some content",
+        )
+
+        assert "error" in result
+        assert "file_id" not in result
+
+    @pytest.mark.unit
+    @pytest.mark.asyncio
+    async def test_fd_fname_003b_carriage_return_in_filename_rejected(
+        self, db, session_context
+    ):
+        result = await _upload_file(
+            session_context,
+            filename="legit.pdf\rFAKE LOG ENTRY",
+            content="some content",
+        )
+
+        assert "error" in result
+
+    @pytest.mark.unit
+    @pytest.mark.asyncio
+    async def test_fd_fname_003c_null_byte_in_filename_rejected(self, db, session_context):
+        result = await _upload_file(
+            session_context,
+            filename="legit.pdf\x00hidden",
+            content="some content",
+        )
+
+        assert "error" in result
+
+    @pytest.mark.unit
+    @pytest.mark.asyncio
+    async def test_fd_fname_003d_tab_in_filename_rejected(self, db, session_context):
+        result = await _upload_file(
+            session_context,
+            filename="legit.pdf\thidden",
+            content="some content",
+        )
+
+        assert "error" in result
+
+    @pytest.mark.unit
+    @pytest.mark.asyncio
+    async def test_fd_upload_001_upload_returns_file_id_and_metadata(
+        self, db, session_context
+    ):
+        """Regression: ordinary, valid filenames must continue to work."""
+        result = await _upload_file(
+            session_context,
+            filename="invoice_march_2026.pdf",
+            content="ordinary invoice content",
+        )
+
+        assert "error" not in result
+        assert result["status"] == "uploaded"
+        assert result["filename"] == "invoice_march_2026.pdf"
+        assert isinstance(result["file_id"], int)