kernel-hardening - Re: [PATCH v6 7/8] Documentation: Add documentation for the Brute LSM

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Date: Fri, 26 Mar 2021 16:41:41 +0100
From: John Wood <john.wood@....com>
To: Jonathan Corbet <corbet@....net>
Cc: Kees Cook <keescook@...omium.org>, Jann Horn <jannh@...gle.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	James Morris <jmorris@...ei.org>, Shuah Khan <shuah@...nel.org>,
	John Wood <john.wood@....com>, "Serge E. Hallyn" <serge@...lyn.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andi Kleen <ak@...ux.intel.com>,
	kernel test robot <oliver.sang@...el.com>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v6 7/8] Documentation: Add documentation for the Brute LSM

On Sun, Mar 21, 2021 at 12:50:47PM -0600, Jonathan Corbet wrote:
> John Wood <john.wood@....com> writes:
>
> > Add some info detailing what is the Brute LSM, its motivation, weak
> > points of existing implementations, proposed solutions, enabling,
> > disabling and self-tests.
> >
> > Signed-off-by: John Wood <john.wood@....com>
> > ---
> >  Documentation/admin-guide/LSM/Brute.rst | 278 ++++++++++++++++++++++++
> >  Documentation/admin-guide/LSM/index.rst |   1 +
> >  security/brute/Kconfig                  |   3 +-
> >  3 files changed, 281 insertions(+), 1 deletion(-)
> >  create mode 100644 Documentation/admin-guide/LSM/Brute.rst
>
> Thanks for including documentation with the patch!
>
> As you get closer to merging this, though, you'll want to take a minute
> (OK, a few minutes) to build the docs and look at the result; there are

Thanks, I will do it.

> a number of places where you're not going to get what you expect.  Just
> as an example:
>
> [...]
>
> > +Based on the above scenario it would be nice to have this detected and
> > +mitigated, and this is the goal of this implementation. Specifically the
> > +following attacks are expected to be detected:
> > +
> > +1.- Launching (fork()/exec()) a setuid/setgid process repeatedly until a
> > +    desirable memory layout is got (e.g. Stack Clash).
> > +2.- Connecting to an exec()ing network daemon (e.g. xinetd) repeatedly until a
> > +    desirable memory layout is got (e.g. what CTFs do for simple network
> > +    service).
> > +3.- Launching processes without exec() (e.g. Android Zygote) and exposing state
> > +    to attack a sibling.
> > +4.- Connecting to a fork()ing network daemon (e.g. apache) repeatedly until the
> > +    previously shared memory layout of all the other children is exposed (e.g.
> > +    kind of related to HeartBleed).
>
> Sphinx will try to recognize your enumerated list, but that may be a bit
> more punctuation than it is prepared to deal with; I'd take the hyphens
> out, if nothing else.

Thanks. I will fix this for the next version.

> > +These statistics are hold by the brute_stats struct.
> > +
> > +struct brute_cred {
> > +	kuid_t uid;
> > +	kgid_t gid;
> > +	kuid_t suid;
> > +	kgid_t sgid;
> > +	kuid_t euid;
> > +	kgid_t egid;
> > +	kuid_t fsuid;
> > +	kgid_t fsgid;
> > +};
>
> That will certainly not render the way you want.  What you need here is
> a literal block:
>
> These statistics are hold by the brute_stats struct::
>
>     struct brute_cred {
> 	kuid_t uid;
> 	kgid_t gid;
> 	kuid_t suid;
> 	kgid_t sgid;
> 	kuid_t euid;
> 	kgid_t egid;
> 	kuid_t fsuid;
> 	kgid_t fsgid;
>     };
>
> The "::" causes all of the indented text following to be formatted
> literally.

Thanks a lot for your comments and guidance. I will build the docs and
check if the output is as I want.

> Thanks,
>
> jon

Regards,
John Wood
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