Date: Tue, 23 Jan 2007 14:44:01 +0300 From: "Andrew N. Below" <defan@zenon.net> To: <freebsd-hackers@freebsd.org> Subject: how to deny reading of several sysctls (for a set of uids, f.e.) Message-ID: <082f01c73ee3$c6b3f810$970da8c0@jam.zenon.net>
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Hello.
System - RELENG_6.
Easiest way I found is to patch libc.
But in this case we still can get an original library and use
LD_PRELOAD.
Is there any way to obtain uid of calling process (thread?)
within the kernel?
We have following extern in src/lib/libc/gen/sysctl.c:
[..]
extern int __sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp,
void *newp, size_t newlen);
[..]
And there is __sysctl (src/sys/kern/kern_sysctl.c):
[..]
/*
* MPSAFE
*/
int
__sysctl(struct thread *td, struct sysctl_args *uap)
[..]
1. Whether this function is called from libc sysctl() ?
2. What can we get from td here? My knowledge about FreeBSD kernel
and kernel threads is not yet enough for understanding this.
I also thought about passing control variable from libc
to kernel, but it seems to be bad idea.
Any other ways?
--
Andrew N. Below
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