From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4CB45B06.2070905@domain.hid> Date: Tue, 12 Oct 2010 14:56:38 +0200 From: Anders Blomdell MIME-Version: 1.0 References: <4CB33738.206@domain.hid> <4CB338AB.3070803@domain.hid> <4CB339F9.5080202@domain.hid> <4CB33F04.3000600@domain.hid> <4CB34031.5090505@domain.hid> <4CB3424A.5090504@domain.hid> <4CB4299D.70600@domain.hid> <4CB43704.4020504@domain.hid> In-Reply-To: <4CB43704.4020504@domain.hid> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-help] Xenomai and capabilities List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "xenomai@xenomai.org" On 2010-10-12 12.23, Anders Blomdell wrote: > On 2010-10-12 11.25, Anders Blomdell wrote: >> On 2010-10-11 18.58, Jan Kiszka wrote: >>> Am 11.10.2010 18:49, Gilles Chanteperdrix wrote: >>>> Jan Kiszka wrote: >>>>> Am 11.10.2010 18:23, Gilles Chanteperdrix wrote: >>>>>> Jan Kiszka wrote: >>>>>>> enabling the Xenomai watchdog should provide a reasonably safe&secure >>>>>>> environment. >>>>>> AFAIK, the BIG FAT warning at the bottom of this page still applies. You >>>>>> can make an environment with no hardware lockups, but secure, I do not >>>>>> think so. We do not know how Xenomai APIs could be exploited for a >>>>>> non-root user to become root. >>>>> >>>>> For sure, no one audited the interface for security so far. There is no >>>>> hole in design that comes to my mind ATM, but I would be surprised as >>>>> well if you couldn't develop any exploit for some bug or missing check. >>>>> Still, there is a huge difference between giving anyone root access and >>>>> confining Xenomai access this way. >>>> >>>> I was just reacting to "reasonably secure". The experience proves that >>>> if you do not do any particular effort for security, then your code is >>>> not secure. Not even reasonably. >>> >>> This is no black-or-white domain, and I wouldn't say we spend no effort >>> on security at all. We do have interest in making the userspace APIs >>> robust which addresses security up to a certain level as well. >>> >>> What is still definitely not secure, though, is RTnet as it consequently >>> lacks any kind of check on user-passed addresses. But that's not >>> Xenomai's fault (rather mine). >> If I understand manpages and code correctly, xenomai is insecure by design (not >> a major problem here, I hope), but I had hoped to be able to avoid CAP_SYS_RAWIO >> which I think is the biggest security problem (access to /proc/kcore IS scary), >> but since CAP_SYS_NICE implies CAP_SYS_RAWIO via shadow.c: >> if (!capable(CAP_SYS_NICE) && >> (xn_gid_arg == -1 || !in_group_p(xn_gid_arg))) >> return -EPERM; >> >> wrap_raise_cap(CAP_SYS_NICE); >> wrap_raise_cap(CAP_IPC_LOCK); >> wrap_raise_cap(CAP_SYS_RAWIO); >> >> I will go for the group thing (simple and totally insecure) for now, and put >> some more thought into it later on. > Well, obviously this feature is somewhat broken: > >> testprog > Xenomai: binding failed: Cannot allocate memory. > > This is what syslog says: > Xenomai: testprog[2367] cannot map MAYDAY page > > Running as root works as it should. CAP_DAC_OVERRIDE fixes this issue (and how safe is that :-( ) How necessary are CAP_SYS_RAWIO and CAP_DAC_OVERRIDE [the two capabiltities i think have the most severe security implications] when main has started running, i.e. could I drop them after initialization and still do something useful? /Anders -- Anders Blomdell Email: anders.blomdell@domain.hid Department of Automatic Control Lund University Phone: +46 46 222 4625 P.O. Box 118 Fax: +46 46 138118 SE-221 00 Lund, Sweden