Re: lnk_file read permission

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 ([email protected]) 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/[email protected]/message/J7ZRMNQ5MJNN3NH2EOMZIBNGRXKQ554N/

Thanks.

> 
> --
> Ondrej Mosnacek
> Software Engineer, Platform Security - SELinux kernel
> Red Hat, Inc.

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