Messages in this thread Patch in this message | | | Date | Mon, 01 May 2006 01:07:14 +0200 | From | devzero@web ... | Subject | Re: another kconfig target for building monolithic ker nel (for security) ? |
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hello !
thanks for help - i found that there seems another way for securing /dev/{k}mem (at least in recent kernels) - the docomentation for the "BSD Secure Levels Linux Security Module" (at Documentation/seclvl.txt) tells:
Level 1 (Default): - /dev/mem and /dev/kmem are read-only - IMMUTABLE and APPEND extended attributes, if set, may not be unset - Cannot load or unload kernel modules - Cannot write directly to a mounted block device - Cannot perform raw I/O operations - Cannot perform network administrative tasks - Cannot setuid any file
so - no need for compiling a static/monolithic kernel anymore !?
regards roland
> -----Ursprüngliche Nachricht----- > Von: Nix <nix@esperi.org.uk> > Gesendet: 30.04.06 12:57:49 > An: Arjan van de Ven <arjan@infradead.org> > CC: davej@redhat.com, linux-kernel@vger.kernel.org > Betreff: Re: another kconfig target for building monolithic kernel (for security) ?
> On 29 Apr 2006, Arjan van de Ven prattled cheerily: > > On Sat, 2006-04-29 at 12:43 -0400, Dave Jones wrote: > >> On Sat, Apr 29, 2006 at 03:03:55PM +0200, devzero@web.de wrote: > >> > >> > i want to harden a linux system (dedicated root server on the internet) by recompiling the kernel without support for lkm (to prevent installation of lkm based rootkits etc) > >> > >> Loading modules via /dev/kmem is trivial thanks to a bunch of tutorials and > >> examples on the web, so this alone doesn't make life that much more difficult for attackers. > > > > /dev/kmem should be a config option too though > > Yeah, but in practice this should work (somewhat old patch, should still > apply): > > diff -durN 2.6.14-seal-orig/include/linux/capability.h 2.6.14-seal/include/linux/capability.h > --- 2.6.14-seal-orig/include/linux/capability.h 2005-10-29 15:15:00.000000000 +0100 > +++ 2.6.14-seal/include/linux/capability.h 2005-10-29 15:25:48.000000000 +0100 > @@ -311,7 +311,7 @@ > > #define CAP_EMPTY_SET to_cap_t(0) > #define CAP_FULL_SET to_cap_t(~0) > -#define CAP_INIT_EFF_SET to_cap_t(~0 & ~CAP_TO_MASK(CAP_SETPCAP)) > +#define CAP_INIT_EFF_SET to_cap_t(~0 & ~CAP_TO_MASK(CAP_SETPCAP) & ~CAP_TO_MASK(CAP_SYS_RAWIO)) > #define CAP_INIT_INH_SET to_cap_t(0) > > #define CAP_TO_MASK(x) (1 << (x)) > > > (and /dev/mem should get the filter patch that fedora has ;-) > > Agreed. > > -- > `On a scale of 1-10, X's "brokenness rating" is 1.1, but that's only > because bringing Windows into the picture rescaled "brokenness" by > a factor of 10.' --- Peter da Silva
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