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Message-ID: <20091230184752.GA18712@us.ibm.com>
Date: Wed, 30 Dec 2009 12:47:52 -0600
From: "Serge E. Hallyn" <serue@...ibm.com>
To: Michael Stone <michael@...top.org>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
linux-security-module@...r.kernel.org,
Andi Kleen <andi@...stfloor.org>, David Lang <david@...g.hm>,
Oliver Hartkopp <socketcan@...tkopp.net>,
Alan Cox <alan@...rguk.ukuu.org.uk>,
Herbert Xu <herbert@...dor.apana.org.au>,
Valdis Kletnieks <Valdis.Kletnieks@...edu>,
Bryan Donlan <bdonlan@...il.com>,
Evgeniy Polyakov <zbr@...emap.net>,
"C. Scott Ananian" <cscott@...ott.net>,
James Morris <jmorris@...ei.org>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Bernie Innocenti <bernie@...ewiz.org>,
Mark Seaborn <mrs@...hic-beasts.com>,
Randy Dunlap <randy.dunlap@...cle.com>,
Américo Wang <xiyou.wangcong@...il.com>,
Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
Samir Bellabes <sam@...ack.fr>,
Casey Schaufler <casey@...aufler-ca.com>,
Pavel Machek <pavel@....cz>
Subject: Re: [PATCH 1/3] Security: Add disablenetwork interface. (v4)
Quoting Michael Stone (michael@...top.org):
> Daniel Bernstein has observed [1] that security-conscious userland processes
> may benefit from the ability to irrevocably remove their ability to create,
> bind, connect to, or send messages except in the case of previously connected
> sockets or AF_UNIX filesystem sockets.
>
> This patch provides
>
> * a new configuration option named CONFIG_SECURITY_DISABLENETWORK,
> * a new prctl option-pair (PR_SET_NETWORK, PR_GET_NETWORK),
> * a new prctl(PR_SET_NETWORK) flag named PR_NETWORK_OFF, and
> * a new task_struct flags field named "network"
>
> Signed-off-by: Michael Stone <michael@...top.org>
> ---
> include/linux/prctl.h | 7 +++++
> include/linux/prctl_network.h | 7 +++++
> include/linux/sched.h | 4 +++
> kernel/sys.c | 53 +++++++++++++++++++++++++++++++++++++++++
> security/Kconfig | 11 ++++++++
> 5 files changed, 82 insertions(+), 0 deletions(-)
> create mode 100644 include/linux/prctl_network.h
>
> diff --git a/include/linux/prctl.h b/include/linux/prctl.h
> index a3baeb2..4eb4110 100644
> --- a/include/linux/prctl.h
> +++ b/include/linux/prctl.h
> @@ -102,4 +102,11 @@
>
> #define PR_MCE_KILL_GET 34
>
> +/* Get/set process disable-network flags */
> +#define PR_SET_NETWORK 35
> +#define PR_GET_NETWORK 36
> +# define PR_NETWORK_ON 0
> +# define PR_NETWORK_OFF 1
> +# define PR_NETWORK_ALL_FLAGS 1
> +
> #endif /* _LINUX_PRCTL_H */
> diff --git a/include/linux/prctl_network.h b/include/linux/prctl_network.h
> new file mode 100644
> index 0000000..d18f8cb
> --- /dev/null
> +++ b/include/linux/prctl_network.h
> @@ -0,0 +1,7 @@
> +#ifndef _LINUX_PRCTL_NETWORK_H
> +#define _LINUX_PRCTL_NETWORK_H
> +
> +extern long prctl_get_network(unsigned long*);
> +extern long prctl_set_network(unsigned long*);
> +
> +#endif /* _LINUX_PRCTL_NETWORK_H */
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index f2f842d..6fcaef8 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1403,6 +1403,10 @@ struct task_struct {
> #endif
> seccomp_t seccomp;
>
> +#ifdef CONFIG_SECURITY_DISABLENETWORK
> + unsigned long network;
> +#endif
> +
> /* Thread group tracking */
> u32 parent_exec_id;
> u32 self_exec_id;
> diff --git a/kernel/sys.c b/kernel/sys.c
> index 26a6b73..b48f021 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -35,6 +35,7 @@
> #include <linux/cpu.h>
> #include <linux/ptrace.h>
> #include <linux/fs_struct.h>
> +#include <linux/prctl_network.h>
>
> #include <linux/compat.h>
> #include <linux/syscalls.h>
> @@ -1578,6 +1579,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
> else
> error = PR_MCE_KILL_DEFAULT;
> break;
> + case PR_SET_NETWORK:
> + error = prctl_set_network((unsigned long*)arg2);
> + break;
> + case PR_GET_NETWORK:
> + error = prctl_get_network((unsigned long*)arg2);
> + break;
> default:
> error = -EINVAL;
> break;
> @@ -1585,6 +1592,52 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
> return error;
> }
>
> +#ifdef CONFIG_SECURITY_DISABLENETWORK
> +
> +long prctl_get_network(unsigned long* user)
> +{
> + return put_user(current->network, user);
> +}
> +
> +long prctl_set_network(unsigned long* user)
> +{
> + unsigned long network_flags;
> + long ret;
> +
> + ret = -EFAULT;
> + if (copy_from_user(&network_flags, user, sizeof(network_flags)))
> + goto out;
Do you expect to pass more than 32 bits through this interface at
some point? If not, how about avoiding the copy, and just passing
a long into prctl_set_network(), and having prctl_get_network
return 0 or a positive value indicating the active bits?
So
long prctl_get_network(void)
{
return current->network;
}
long prctl_set_network(unsigned long network_flags)
{
if (network_flags & ~PR_NETWORK_ALL_FLAGS)
return -EINVAL;
if (current->network & ~network_flags)
return -EPERM;
current->network = network_flags;
return 0;
}
> + ret = -EINVAL;
> + if (network_flags & ~PR_NETWORK_ALL_FLAGS)
> + goto out;
> +
> + /* only dropping access is permitted */
> + ret = -EPERM;
> + if (current->network & ~network_flags)
whitespace.
> + goto out;
> +
> + current->network = network_flags;
> + ret = 0;
> +
> +out:
> + return ret;
> +}
> +
> +#else
> +
> +long prctl_get_network(unsigned long* user)
> +{
> + return -ENOSYS;
> +}
> +
> +long prctl_set_network(unsigned long* user)
> +{
> + return -ENOSYS;
> +}
> +
> +#endif /* ! CONFIG_SECURITY_DISABLENETWORK */
> +
> SYSCALL_DEFINE3(getcpu, unsigned __user *, cpup, unsigned __user *, nodep,
> struct getcpu_cache __user *, unused)
> {
> diff --git a/security/Kconfig b/security/Kconfig
> index 226b955..afd7f76 100644
> --- a/security/Kconfig
> +++ b/security/Kconfig
> @@ -137,6 +137,17 @@ config LSM_MMAP_MIN_ADDR
> this low address space will need the permission specific to the
> systems running LSM.
>
> +config SECURITY_DISABLENETWORK
> + bool "Socket and networking discretionary access control"
> + depends on SECURITY_NETWORK
> + help
> + This enables processes to drop networking privileges via
> + prctl(PR_SET_NETWORK, PR_NETWORK_OFF).
> +
> + See Documentation/disablenetwork.txt for more information.
> +
> + If you are unsure how to answer this question, answer N.
> +
> source security/selinux/Kconfig
> source security/smack/Kconfig
> source security/tomoyo/Kconfig
> --
> 1.6.6.rc2
> --
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