Messages in this thread | | | Date | Tue, 22 Jun 1999 11:41:35 +0200 (CEST) | From | Domas Mituzas <> | Subject | Re: immutable flag on ext2fs |
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Hello pals,
2.2 kernels have full capabilities for protecting removing immutable flags and much more. The simpliest way to make a secure system is to have two kernels. One vanilla, and second a little bit patched... just look at theese lines in /usr/src/linux/include/linux/capability.h: #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_INH_SET to_cap_t(~0 & ~CAP_TO_MASK(CAP_SETPCAP))
For secure kernel you can make something like:
#define CAP_FULL_SET to_cap_t(~0 & ~CAP_TO_MASK(CAP_SETPCAP) & ~CAP_TO_MASK(CAP_LINUX_IMMUTABLE))
So even root will not be able to remove immutable flags with this kernel. Or there are more funny things... adding right here CAP_NET_RAW will disable ability to run sniffers (and sending ping).
just look into that capability.h and you will find everything you can tweak out =]
some more enteresting examples:
/* Allow ptrace() of any process */ #define CAP_SYS_PTRACE 19
huh, noone will able to trace processes.
/* Allow manipulation of system clock */ /* Allow irix_stime on mips */ /* Allow setting the real-time clock */ #define CAP_SYS_TIME 25
changing time is impossible any more :-)
There are other capabilities, that restrict accessing devices directly etc. But theese cannot be restricted in kernel - they should be controlled at boot time... But it is not impossible to change it in a running system - using modules or just raw kernel image file. Then you can safely turn on securebits and your system is invulnerable.
With respect, Domas Mituzas
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