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Message-ID: <202106081616.EC17DC1D0D@keescook>
Date: Tue, 8 Jun 2021 16:19:31 -0700
From: Kees Cook <keescook@...omium.org>
To: John Wood <john.wood@....com>
Cc: Jann Horn <jannh@...gle.com>, Jonathan Corbet <corbet@....net>,
James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>, Shuah Khan <shuah@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
Arnd Bergmann <arnd@...db.de>, Andi Kleen <ak@...ux.intel.com>,
valdis.kletnieks@...edu,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Randy Dunlap <rdunlap@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org,
linux-kselftest@...r.kernel.org, linux-arch@...r.kernel.org,
linux-hardening@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v8 0/8] Fork brute force attack mitigation
On Sat, Jun 05, 2021 at 05:03:57PM +0200, John Wood wrote:
> [...]
> the kselftest to avoid the detection ;) ). So, in this version, to track
> all the statistical data (info related with application crashes), the
> extended attributes feature for the executable files are used. The xattr is
> also used to mark the executables as "not allowed" when an attack is
> detected. Then, the execve system call rely on this flag to avoid following
> executions of this file.
I have some concerns about this being actually usable and not creating
DoS situations. For example, let's say an attacker had found a hard-to-hit
bug in "sudo", and starts brute forcing it. When the brute LSM notices,
it'll make "sudo" unusable for the entire system, yes?
And a reboot won't fix it, either, IIUC.
It seems like there is a need to track "user" running "prog", and have
that be timed out. Are there use-cases here where that wouldn't be
sufficient?
-Kees
--
Kees Cook
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