Repository: Chainlit/chainlit
Issue category: Security Vulnerability

Issue:
fix(security): add auth to /project/file get endpoint
fixes https://github.com/Chainlit/chainlit/issues/1101


Hints:
Thanks @qvalentin for the report & fix! We'd like to take this along in the next release.

Any chance you could add a regression unittest demonstrating the issue and it's resolution?

Patch:
diff --git a/backend/chainlit/server.py b/backend/chainlit/server.py
index b4bf0dd989..7c4a824b68 100644
--- a/backend/chainlit/server.py
+++ b/backend/chainlit/server.py
@@ -41,6 +41,7 @@
     APIRouter,
     Depends,
     FastAPI,
+    File,
     Form,
     HTTPException,
     Query,
@@ -839,11 +840,9 @@ async def delete_thread(
 
 @router.post("/project/file")
 async def upload_file(
+    current_user: Annotated[Union[User, PersistedUser], Depends(get_current_user)],
     session_id: str,
     file: UploadFile,
-    current_user: Annotated[
-        Union[None, User, PersistedUser], Depends(get_current_user)
-    ],
 ):
     """Upload a file to the session files directory."""
 
@@ -868,17 +867,21 @@ async def upload_file(
 
     content = await file.read()
 
+    assert file.filename, "No filename for uploaded file"
+    assert file.content_type, "No content type for uploaded file"
+
     file_response = await session.persist_file(
         name=file.filename, content=content, mime=file.content_type
     )
 
-    return JSONResponse(file_response)
+    return JSONResponse(content=file_response)
 
 
 @router.get("/project/file/{file_id}")
 async def get_file(
     file_id: str,
-    session_id: Optional[str] = None,
+    session_id: str,
+    current_user: Annotated[Union[User, PersistedUser], Depends(get_current_user)],
 ):
     """Get a file from the session files directory."""
 
@@ -888,10 +891,17 @@ async def get_file(
 
     if not session:
         raise HTTPException(
-            status_code=404,
-            detail="Session not found",
+            status_code=401,
+            detail="Unauthorized",
         )
 
+    if current_user:
+        if not session.user or session.user.identifier != current_user.identifier:
+            raise HTTPException(
+                status_code=401,
+                detail="You are not authorized to download files from this session",
+            )
+
     if file_id in session.files:
         file = session.files[file_id]
         return FileResponse(file["path"], media_type=file["type"])


Test patch:
diff --git a/backend/tests/conftest.py b/backend/tests/conftest.py
index 94ae4a596a..7cc4266371 100644
--- a/backend/tests/conftest.py
+++ b/backend/tests/conftest.py
@@ -1,5 +1,6 @@
 import datetime
 from contextlib import asynccontextmanager
+from typing import Callable
 from unittest.mock import AsyncMock, Mock
 
 import pytest
@@ -20,20 +21,30 @@ def persisted_test_user():
 
 
 @pytest.fixture
-def mock_session():
-    mock = Mock(spec=WebsocketSession)
-    mock.id = "test_session_id"
-    mock.user_env = {"test_env": "value"}
-    mock.chat_settings = {}
-    mock.chat_profile = None
-    mock.http_referer = None
-    mock.client_type = "webapp"
-    mock.languages = ["en"]
-    mock.thread_id = "test_thread_id"
-    mock.emit = AsyncMock()
-    mock.has_first_interaction = True
-
-    return mock
+def mock_session_factory(persisted_test_user: PersistedUser) -> Callable[..., Mock]:
+    def create_mock_session(**kwargs) -> Mock:
+        mock = Mock(spec=WebsocketSession)
+        mock.user = kwargs.get("user", persisted_test_user)
+        mock.id = kwargs.get("id", "test_session_id")
+        mock.user_env = kwargs.get("user_env", {"test_env": "value"})
+        mock.chat_settings = kwargs.get("chat_settings", {})
+        mock.chat_profile = kwargs.get("chat_profile", None)
+        mock.http_referer = kwargs.get("http_referer", None)
+        mock.client_type = kwargs.get("client_type", "webapp")
+        mock.languages = kwargs.get("languages", ["en"])
+        mock.thread_id = kwargs.get("thread_id", "test_thread_id")
+        mock.emit = AsyncMock()
+        mock.has_first_interaction = kwargs.get("has_first_interaction", True)
+        mock.files = kwargs.get("files", {})
+
+        return mock
+
+    return create_mock_session
+
+
+@pytest.fixture
+def mock_session(mock_session_factory) -> Mock:
+    return mock_session_factory()
 
 
 @asynccontextmanager
diff --git a/backend/tests/test_server.py b/backend/tests/test_server.py
index 6aa9c16d5a..36c65124d6 100644
--- a/backend/tests/test_server.py
+++ b/backend/tests/test_server.py
@@ -1,12 +1,19 @@
 import os
 from pathlib import Path
-from unittest.mock import Mock, create_autospec, mock_open
+import pathlib
+from typing import Callable
+from unittest.mock import AsyncMock, Mock, create_autospec, mock_open
+import datetime  # Added import for datetime
 
 import pytest
+import tempfile
+from chainlit.session import WebsocketSession
 from chainlit.auth import get_current_user
 from chainlit.config import APP_ROOT, ChainlitConfig, load_config
 from chainlit.server import app
 from fastapi.testclient import TestClient
+from chainlit.types import FileReference
+from chainlit.user import PersistedUser  # Added import for PersistedUser
 
 
 @pytest.fixture
@@ -219,7 +226,7 @@ def test_get_avatar_non_existent_favicon(
 
 
 def test_avatar_path_traversal(
-    test_client: TestClient, monkeypatch: pytest.MonkeyPatch, tmp_path
+    test_client: TestClient, monkeypatch: pytest.MonkeyPatch, tmp_path: pathlib.Path
 ):
     """Test to prevent potential path traversal in avatar route on Windows."""
 
@@ -240,6 +247,268 @@ def test_avatar_path_traversal(
     assert response.status_code == 400
 
 
+@pytest.fixture
+def mock_session_get_by_id_patched(mock_session: Mock, monkeypatch: pytest.MonkeyPatch):
+    test_session_id = "test_session_id"
+
+    # Mock the WebsocketSession.get_by_id method to return the mock session
+    monkeypatch.setattr(
+        "chainlit.session.WebsocketSession.get_by_id",
+        lambda session_id: mock_session if session_id == test_session_id else None,
+    )
+
+    return mock_session
+
+
+def test_get_file_success(
+    test_client: TestClient,
+    mock_session_get_by_id_patched: Mock,
+    tmp_path: pathlib.Path,
+    mock_get_current_user: Mock,
+):
+    """
+    Test successful retrieval of a file from a session.
+    """
+    # Set current_user to match session.user
+    mock_get_current_user.return_value = mock_session_get_by_id_patched.user
+
+    # Create test data
+    test_content = b"Test file content"
+    test_file_id = "test_file_id"
+
+    # Create a temporary file with the test content
+    test_file = tmp_path / "test_file"
+    test_file.write_bytes(test_content)
+
+    mock_session_get_by_id_patched.files = {
+        test_file_id: {
+            "id": test_file_id,
+            "path": test_file,
+            "name": "test.txt",
+            "type": "text/plain",
+            "size": len(test_content),
+        }
+    }
+
+    # Make the GET request to retrieve the file
+    response = test_client.get(
+        f"/project/file/{test_file_id}?session_id={mock_session_get_by_id_patched.id}"
+    )
+
+    # Verify the response
+    assert response.status_code == 200
+    assert response.content == test_content
+    assert response.headers["content-type"].startswith("text/plain")
+
+
+def test_get_file_not_existent_file(
+    test_client: TestClient,
+    mock_session_get_by_id_patched: Mock,
+    mock_get_current_user: Mock,
+):
+    """
+    Test retrieval of a non-existing file from a session.
+    """
+    # Set current_user to match session.user
+    mock_get_current_user.return_value = mock_session_get_by_id_patched.user
+
+    # Make the GET request to retrieve the file
+    response = test_client.get("/project/file/test_file_id?session_id=test_session_id")
+
+    # Verify the response
+    assert response.status_code == 404
+
+
+def test_get_file_non_existing_session(
+    test_client: TestClient,
+    tmp_path: pathlib.Path,
+    mock_session_get_by_id_patched: Mock,
+    mock_session: Mock,
+    monkeypatch: pytest.MonkeyPatch,
+):
+    """
+    Test that an unauthenticated user cannot retrieve a file uploaded by an authenticated user.
+    """
+
+    # Attempt to access the file without authentication by providing an invalid session_id
+    response = test_client.get(
+        f"/project/file/nonexistent?session_id=unauthenticated_session_id"
+    )
+
+    # Verify the response
+    assert response.status_code == 401  # Unauthorized
+
+
+def test_upload_file_success(
+    test_client: TestClient,
+    test_config: ChainlitConfig,
+    mock_session_get_by_id_patched: Mock,
+):
+    """Test successful file upload."""
+
+    # Prepare the files to upload
+    file_content = b"Sample file content"
+    files = {
+        "file": ("test_upload.txt", file_content, "text/plain"),
+    }
+
+    # Mock the persist_file method to return a known value
+    expected_file_id = "mocked_file_id"
+    mock_session_get_by_id_patched.persist_file = AsyncMock(
+        return_value={
+            "id": expected_file_id,
+            "name": "test_upload.txt",
+            "type": "text/plain",
+            "size": len(file_content),
+        }
+    )
+
+    # Make the POST request to upload the file
+    response = test_client.post(
+        "/project/file",
+        files=files,
+        params={"session_id": mock_session_get_by_id_patched.id},
+    )
+
+    # Verify the response
+    assert response.status_code == 200
+    response_data = response.json()
+    assert "id" in response_data
+    assert response_data["id"] == expected_file_id
+    assert response_data["name"] == "test_upload.txt"
+    assert response_data["type"] == "text/plain"
+    assert response_data["size"] == len(file_content)
+
+    # Verify that persist_file was called with the correct arguments
+    mock_session_get_by_id_patched.persist_file.assert_called_once_with(
+        name="test_upload.txt", content=file_content, mime="text/plain"
+    )
+
+
+def test_file_access_by_different_user(
+    test_client: TestClient,
+    mock_session_get_by_id_patched: Mock,
+    persisted_test_user: PersistedUser,
+    tmp_path: pathlib.Path,
+    mock_session_factory: Callable[..., Mock],
+):
+    """Test that a file uploaded by one user cannot be accessed by another user."""
+
+    # Prepare the files to upload
+    file_content = b"Sample file content"
+    files = {
+        "file": ("test_upload.txt", file_content, "text/plain"),
+    }
+
+    # Mock the persist_file method to return a known value
+    expected_file_id = "mocked_file_id"
+    mock_session_get_by_id_patched.persist_file = AsyncMock(
+        return_value={
+            "id": expected_file_id,
+            "name": "test_upload.txt",
+            "type": "text/plain",
+            "size": len(file_content),
+        }
+    )
+
+    # Make the POST request to upload the file
+    response = test_client.post(
+        "/project/file",
+        files=files,
+        params={"session_id": mock_session_get_by_id_patched.id},
+    )
+
+    # Verify the response
+    assert response.status_code == 200
+
+    response_data = response.json()
+    assert "id" in response_data
+    file_id = response_data["id"]
+
+    # Create a second session with a different user
+    second_session = mock_session_factory(
+        id="another_session_id",
+        user=PersistedUser(
+            id="another_user_id",
+            createdAt=datetime.datetime.now().isoformat(),
+            identifier="another_user_identifier",
+        ),
+    )
+
+    # Attempt to access the uploaded file using the second user's session
+    response = test_client.get(
+        f"/project/file/{file_id}?session_id={second_session.id}"
+    )
+
+    # Verify that the access attempt fails
+    assert response.status_code == 401  # Unauthorized
+
+
+def test_upload_file_missing_file(
+    test_client: TestClient,
+    mock_session: Mock,
+):
+    """Test file upload with missing file in the request."""
+
+    # Make the POST request without a file
+    response = test_client.post(
+        "/project/file",
+        data={"session_id": mock_session.id},
+    )
+
+    # Verify the response
+    assert response.status_code == 422  # Unprocessable Entity
+    assert "detail" in response.json()
+
+
+def test_upload_file_invalid_session(
+    test_client: TestClient,
+):
+    """Test file upload with an invalid session."""
+
+    # Prepare the files to upload
+    file_content = b"Sample file content"
+    files = {
+        "file": ("test_upload.txt", file_content, "text/plain"),
+    }
+
+    # Make the POST request with an invalid session_id
+    response = test_client.post(
+        "/project/file",
+        files=files,
+        data={"session_id": "invalid_session_id"},
+    )
+
+    # Verify the response
+    assert response.status_code == 422
+
+
+def test_upload_file_unauthorized(
+    test_client: TestClient,
+    test_config: ChainlitConfig,
+    mock_session_get_by_id_patched: Mock,
+):
+    """Test file upload without proper authorization."""
+
+    # Mock the upload_file_session to have no user
+    mock_session_get_by_id_patched.user = None
+
+    # Prepare the files to upload
+    file_content = b"Sample file content"
+    files = {
+        "file": ("test_upload.txt", file_content, "text/plain"),
+    }
+
+    # Make the POST request to upload the file
+    response = test_client.post(
+        "/project/file",
+        files=files,
+        data={"session_id": mock_session_get_by_id_patched.id},
+    )
+
+    assert response.status_code == 422
+
+
 def test_project_translations_file_path_traversal(
     test_client: TestClient, monkeypatch: pytest.MonkeyPatch
 ):