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SubjectRe: [PATCH v3] Restrict unprivileged access to kernel syslog
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On Sun, 2011-01-02 at 10:05 +0100, Pavel Machek wrote:
> Hi!
>
> > The kernel syslog contains debugging information that is often useful
> > during exploitation of other vulnerabilities, such as kernel heap
> > addresses. Rather than futilely attempt to sanitize hundreds (or
> > thousands) of printk statements and simultaneously cripple useful
> > debugging functionality, it is far simpler to create an option that
> > prevents unprivileged users from reading the syslog.
> >
> > This patch, loosely based on grsecurity's GRKERNSEC_DMESG, creates the
> > dmesg_restrict sysctl. When set to "0", the default, no restrictions
> > are enforced. When set to "1", only users with CAP_SYS_ADMIN can read
> > the kernel syslog via dmesg(8) or other mechanisms.
>
> Ok, this is very very ugly.
>
> You essentially create a bit to control what other bit does. Clean
> solution would be CAP_SYS_DMESG, and make sure that is given to
> processes by default...
>
> ...and that would be actually very good thing -- on cellphones, you
> want some users without ability to connect to network, so you could
> introduce CAP_NETWORK etc...
>
> Pavel

The CONFIG was added on suggestion that it would make it easier for
distributions to enable this behavior by default. The patch was
modified to use CAP_SYSLOG, which seems in line with what you want.

Thanks,
Dan



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