lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Thu, 3 Sep 2015 20:17:05 -0700
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Michael Tirado <mtirado418@...il.com>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Tycho Andersen <tycho.andersen@...onical.com>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
	Kees Cook <keescook@...omium.org>
Subject: Re: eBPF / seccomp globals?

On Fri, Sep 04, 2015 at 01:01:20AM +0000, Michael Tirado wrote:
> Hiyall,
> 
> I have created a seccomp white list filter for a program that launches
> other less trustworthy programs.  It's working great so far, but I
> have run into a little roadblock.  the launcher program needs to call
> execve as it's final step, but that may not be present in the white
> list.  I am wondering if there is any way to use some sort of global
> variable that will be preserved between syscall filter calls so that I
> can allow only one execve, if not present in white list by
> incrementing a counter variable.
> 
> I see that in Documentation/networking/filter.txt one of the registers
> is documented as being a pointer to struct sk_buff, in the seccomp
> context this is a pointer to struct seccomp_data  instead, right?  and
> the line about callee saved registers R6-R9  probably refers to them
> being saved across calls within that filter, and not calls between
> filters?

R6-R9 are the registered preserved across calls to helper functions
within single program. They are not preserved across invocations
of the same program. At the start of the program only R1 (pointer
to context) is valid.
The eBPF programs used for kprobes, sockets and TC can simulate
global state via maps. Like a map of one element can have some
'struct globals { ... }' as a value in such map. Then programs
can keep global state in there. If a key into such map is cpu_id,
then such state becomes per-cpu global. Other tricks possible too.
Unfortunately seccomp doesn't have access to eBPF yet
(only classic BPF is supported), but, I believe, Tycho is
working on adding eBPF to seccomp and criu of eBPF programs...

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists