Messages in this thread | | | Date | Thu, 3 Feb 2011 16:49:08 -0800 (PST) | From | david@lang ... | Subject | Re: CAP_SYSLOG, 2.6.38 and user space |
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On Thu, 3 Feb 2011, Serge E. Hallyn wrote:
> Quoting Gergely Nagy (algernon@balabit.hu): >> On Thu, 2011-02-03 at 15:32 +0000, Serge E. Hallyn wrote: >>>> Back in november, a patch was merged into the kernel (in commit >>>> ce6ada35bdf710d16582cc4869c26722547e6f11), that splits CAP_SYSLOG out of >>>> CAP_SYS_ADMIN. >>>> >>>> Sadly, this has an unwelcomed consequence, that any userspace syslogd >>>> that formerly used CAP_SYS_ADMIN will stop working, unless upgraded, or >>>> otherwise adapted to the change. >>>> >>>> However, updating userspace isn't that easy, either, if one wants to >>>> support multiple kernels with the same userspace binary: pre-2.6.38, one >>>> needs CAP_SYS_ADMIN, but later kernels will need CAP_SYS_ADMIN. It would >>>> be trivial to keep both, but that kind of defeats the purpose of >>>> CAP_SYSLOG, >>> >>> The idea would be to only use both when you detect a possibly older >>> kernel. >> >> I was considering that, but... how do I reliably detect an older kernel? >> So far, I didn't find a reliable way with which I can detect a kernel >> version at run-time (apart from parsing utsname) > > ... Why not parse utsname?
because the name may be different on different systems, a generic software package is not going to be able to interpret them all.
>>> However, you're right of course, I really should have provided some way >>> for userspace to click 'ok, got the message, now continue anyway because >>> I'm running older userspace for now,' i.e. a sysctl perhaps. >>> >>> Sorry about the trouble. Here is a patch to just warn for now, with >>> the changelog showing what i intend to push next. >>> >>> sorry again, >>> -serge >>> >>> From 2d7408541dd3a6e19a4265b028233789be6a40f4 Mon Sep 17 00:00:00 2001 >>> From: Serge Hallyn <serge@peq.(none)> >>> Date: Thu, 3 Feb 2011 09:26:15 -0600 >>> Subject: [PATCH 1/1] cap_syslog: don't refuse cap_sys_admin for now >>> >>> At 2.6.39 or 2.6.40, let's add a sysctl which defaults to 0. When >>> 0, refuse if cap_sys_admin, if 1, then allow. This will allow >>> users to acknowledge (permanently, if they must, using /etc/sysctl.conf) >>> that they've seen the syslog message about cap_sys_admin being >>> deprecated for syslog. >> >> Could we have it the other way around, at least for a while? Otherwise, > > Sure. > > So long as there is a definite path toward eventually having syslog > with CAP_SYS_ADMIN be denied.
I can see what you would want to allow for a syslog daemon to have CAP_SYSLOG without needing to have CAP_SYS_ADMIN, but why do you see it as important to deny the ability if someone has CAP_SYS_ADMIN?
David Lang
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