A requirement for the current user to own ttys

Egmont Koblinger egmont at gmail.com
Sun Mar 12 21:08:13 UTC 2017


Hi,

Why do you think on my system I cannot access vcs* devices. As far as I
> remember I never said that.
>

You did include the output of "ls -l /dev/vcs*" on your system, showing
that they're owned by vcsa and chmod 600. So, they are not directly
accessible to your 'echo' or 'ghost' users. They might be accessible via
cons.saver.


> I am sorry if didn't make it clear. On my system cons.saver is owned by
> the vcsa user and has the setuid bit. vcs* devices are owned by the vcsa
> user as well, and the user has read/write permissions.
>

> Once again, my questions were only about tty devices. I do not know why
> you're answering questions I never asked.
>
>
I am not sure if the same security policy should be applied to vcs* devices.
>

So, again, if I'm not mistaken, cons.saver basically does the following:
Based on the ownership, permissions etc. of _/dev/ttyX_, it either grants
or denies access to _/dev/vcsaX_. You cannot examine the ttyX and the vcsaX
story independently from each other. They are both part of 1 single complex
story.


Cheers,
egmont
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