Currently I'm using 0750 for directories and 0640 for files. Is it possible to lower these permissions? I know this depends on the setup of the hoster (FTP/PHP/Apache user in same group?). But what is possible? Which permission Typo3 really needs for running correctly?
According to install tool the following folders should be writable:
- fileadmin
- fileadmin/_temp_
- typo3
- typo3conf
- typo3conf/ext
- typo3conf/l10n
- typo3temp
- uploads
- uploads/media
- uploads/pics
- uploads/tf
There is no need for write permissions on typo3/. This is only needed, if you want to install an system extension (what you should not do) and for some .htaccess files which could be created by the install tool (create them by hand, or change permissions afterwards).
Usually your FTP-User and your Webserver-User are different. So they should be in the same group. So you need to set permissions to 0770 (directorys) and 0660 (files) so you can upload files via FTP and edit them via TYPO3. Otherwise you upload an file via FTP with 0630 - and you will not be able to delete that file via TYPO3.
来源：https://stackoverflow.com/questions/9300160/what-are-the-lowest-possible-permissions-for-typo3