Il 2020-07-30 10:11 Ondrej Mosnacek ha scritto:
There are attacks possible, although possibly not for the threat model that is interesting for a regular Fedora user. A symlink is technically still a file with some data in it (representing the path to the target, but you can basically put an arbitrary string there), so it could be used as a covert channel to smuggle some data between domains. In an MLS setting, which is one of the main target use cases of SELinux, such information leak could be a serious concern.
True, in a full MLS or strict selinux mode, symlink can be used to sneakly pass some unwanted data between domains. But, as you stated, this should be a non-issue for a targeted policy as used by Fedora, CentOS, etc.
So for Fedora it might indeed make sense to add some "domain_can_read_symlinks" boolean for people who customize things with symlinks a lot... But there might be other reasons for being careful with symlinks that you or I haven't thought of :) I'd suggest asking on the upstream mailing list (selinux@xxxxxxxxxxxxxxx) on if/why it's a good idea to follow the principle of least privilege also for symlinks. You are likely to get a more educated answer there.
The boolean "can_read_symlinks" is, indeed, a very good idea. I'll ask on upstream mailing list as you suggested.
I don't understand what is meant here... Do you have a link to the bugzilla in question?
Sorry, it was not on bugzilla, but on this same list: https://lists.fedoraproject.org/archives/list/selinux@xxxxxxxxxxxxxxxxxxxxxxx/message/J7ZRMNQ5MJNN3NH2EOMZIBNGRXKQ554N/
Thanks.
-- Ondrej Mosnacek Software Engineer, Platform Security - SELinux kernel Red Hat, Inc.
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