Re: posix capabilities inheritance

[Pavel Machek <pavel@ucw.cz>]

Hi!

> > The code to drop privs is not hard, but it's also not trivial.
> 
> Here's an example code sequence that demonstrates how a setuid-to-root
> application could drop all capabilities except for CAP_IPC_LOCK and
> then run with the non-privileged uid:
> 
>     #include <sys/prctl.h>
>     #include <sys/capability.h>
> 
> 	...
> 
> 	cap_t c;
> 
> 	if (prctl(PR_SET_KEEPCAPS, 1UL, 0UL, 0UL, 0UL) < 0 ||
> 	    seteuid(getuid()) < 0 ||
> 	    !(c = cap_from_text("cap_ipc_lock=eip")) ||
> 	    cap_set_proc(c) < 0)
> 		/* handle error */;
> 
> However, I agree that it's often not viable to require application
> changes to achieve the desired result.

IIRC, libraries have special startup sections that run before
main(). And c++ constructors do, too; so wrapper still might be safer
option.

								Pavel
-- 
When do you have a heart between your knees?
[Johanka's followup: and *two* hearts?]