Sysctl syscall

Sysctl syscall

[Hasso Tepper]

Compiling the program which uses a lot "sysctl" syscalls, gives me this 
warning on Debian unstable:

"warning: the `sysctl' syscall has been removed from 2.6.18+ kernels, 
direct access to `/proc/sys' should be used instead."

Is it true? And what can be used as alternative which would work with both 
2.4 and 2.6 kernels and would work with capabilities (sys/capability.h)?
Accessing `/proc/sys' directly isn't such alternative as it doesn't work 
with capabilities.


regards,

-- 
Hasso Tepper
Elion Enterprises Ltd. [AS3249]
Data Communication Network Administrator

Re: Sysctl syscall

[Jan Engelhardt]

On Nov 16 2006 00:03, Hasso Tepper wrote:
>
>Compiling the program which uses a lot "sysctl" syscalls, gives me this 
>warning on Debian unstable:
>
>"warning: the `sysctl' syscall has been removed from 2.6.18+ kernels, 
>direct access to `/proc/sys' should be used instead."
>
>Is it true?

Well it was unobsoleted in 2.6.19 if I followed the list correctly.

>And what can be used as alternative which would work with both 
>2.4 and 2.6 kernels
>and would work with capabilities (sys/capability.h)?
>Accessing `/proc/sys' directly isn't such alternative as it doesn't work 
>with capabilities.



	-`J'
-- 

Re: Sysctl syscall

[Andi Kleen]

Hasso Tepper <hasso@estpak.ee> writes:
> 2.4 and 2.6 kernels and would work with capabilities (sys/capability.h)?
> Accessing `/proc/sys' directly isn't such alternative as it doesn't work 
> with capabilities.

What do you mean with "/proc/sys doesn't work with capabilities"?

-Andi

Re: Sysctl syscall

[Hasso Tepper]

Andi Kleen wrote:
> Hasso Tepper <hasso@estpak.ee> writes:
> > 2.4 and 2.6 kernels and would work with capabilities
> > (sys/capability.h)? Accessing `/proc/sys' directly isn't such
> > alternative as it doesn't work with capabilities.
>
> What do you mean with "/proc/sys doesn't work with capabilities"?

I have process which drops root privileges after startup and retains only 
some privileges using CAP_NET_ADMIN and CAP_SYS_ADMIN capabilities.
I can change values in /proc/sys/net/ipv[46]/* (like turning forwarding 
on/off) from this process using sysctl syscall, but I can't write 
directly into /proc/sys/net/ipv[46]/* from it.


regards,
 
-- 
Hasso Tepper
Elion Enterprises Ltd. [AS3249]
Data Communication Network Administrator

Re: Sysctl syscall

[Andi Kleen]

On Friday 17 November 2006 09:07, Hasso Tepper wrote:

> I have process which drops root privileges after startup and retains only 
> some privileges using CAP_NET_ADMIN and CAP_SYS_ADMIN capabilities.
> I can change values in /proc/sys/net/ipv[46]/* (like turning forwarding 
> on/off) from this process using sysctl syscall, but I can't write 
> directly into /proc/sys/net/ipv[46]/* from it.

That sounds more like a security bug than a feature to be preserved.

-Andi 

Re: Sysctl syscall

[Hasso Tepper]

Andi Kleen wrote:
> On Friday 17 November 2006 09:07, Hasso Tepper wrote:
> > I have process which drops root privileges after startup and retains
> > only some privileges using CAP_NET_ADMIN and CAP_SYS_ADMIN
> > capabilities. I can change values in /proc/sys/net/ipv[46]/* (like
> > turning forwarding on/off) from this process using sysctl syscall,
> > but I can't write directly into /proc/sys/net/ipv[46]/* from it.
>
> That sounds more like a security bug than a feature to be preserved.

Why? IMHO it's normal that process with CAP_NET_ADMIN capabilities can 
modify settings in /proc/sys/net/. From /usr/include/sys/capability.h:

/* Allow interface configuration */
/* Allow administration of IP firewall, masquerading and accounting */
/* Allow setting debug option on sockets */
/* Allow modification of routing tables */
/* Allow setting arbitrary process / process group ownership on
   sockets */
/* Allow binding to any address for transparent proxying */
/* Allow setting TOS (type of service) */
/* Allow setting promiscuous mode */
/* Allow clearing driver statistics */
/* Allow multicasting */
/* Allow read/write of device-specific registers */
/* Allow activation of ATM control sockets */

#define CAP_NET_ADMIN        12


regards,

-- 
Hasso Tepper
Elion Enterprises Ltd. [AS3249]
Data Communication Network Administrator

Sysctl syscall

[Hasso Tepper]

Compiling the program which uses a lot "sysctl" syscalls, gives me this 
warning on Debian unstable:

"warning: the `sysctl' syscall has been removed from 2.6.18+ kernels, 
direct access to `/proc/sys' should be used instead."

Is it true? And what can be used as alternative which would work with both 
2.4 and 2.6 kernels and would work with capabilities (sys/capability.h)?
Accessing `/proc/sys' directly isn't such alternative as it doesn't work 
with capabilities.


regards,

-- 
Hasso Tepper
Elion Enterprises Ltd. [AS3249]
Data Communication Network Administrator

Sysctl syscall

[Hasso Tepper]

Compiling the program which uses a lot "sysctl" syscalls, gives me this 
warning on Debian unstable:

"warning: the `sysctl' syscall has been removed from 2.6.18+ kernels, 
direct access to `/proc/sys' should be used instead."

Is it true? And what can be used as alternative which would work with both 
2.4 and 2.6 kernels and would work with capabilities (sys/capability.h)?
Accessing `/proc/sys' directly isn't such alternative as it doesn't work 
with capabilities.


regards,

-- 
Hasso Tepper
Elion Enterprises Ltd. [AS3249]
Data Communication Network Administrator