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SubjectRe: Capabilities done right [diff against 2.3.1]
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> > No, it inherits the powers of the user...

Which reminds me.

Say you have an app, SUID 'lp' (random example user).

And say the app closes all file descriptors, opens a network socket and
dup's it (blindly). Sure, the app is buggy, but that's another issue.

And now the user can run it with less privilege and it fails to open a network
socket, and opens its later file descriptors to FDs 0,1,2 instead.

Now, the user has an easy way to (possibly) write things to the later file
descriptors, by doing anything which will cause stderr output.

Is this possible? Or does attempting to do something you don't have the
capability for yield an immediate signal/death (a normally fatal SIGCAP,
or whatever you felt like calling it)? Even if that happens, then you
may have a different problem - a way to kill processes in critical sections
where you might not presently be able to send them signals.

David.


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