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Message-ID: <551280e51001161858q740bf246n2ed389920de689e7@mail.gmail.com>
Date: Sat, 16 Jan 2010 18:58:41 -0800
From: "Andrew G. Morgan" <morgan@...nel.org>
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>,
"Serge E. Hallyn" <serue@...ibm.com>, Pavel Machek <pavel@....cz>,
Al Viro <viro@...iv.linux.org.uk>,
Kyle Moffett <kyle@...fetthome.net>
Subject: Re: disablenetwork (v5): Require CAP_SETPCAP to enable
disablenetwork.
On Fri, Jan 15, 2010 at 12:13 AM, Michael Stone <michael@...top.org> wrote:
> We implement this check by allocating a new flag bit in task_struct->network
> and by propagating its semantics throughout the disablenetwork facility.
>
> Signed-off-by: Michael Stone <michael@...top.org>
> ---
> include/linux/prctl.h | 8 +++++---
> kernel/sys.c | 14 +++++++++++++-
> security/disablenetwork.c | 15 ++++++++-------
> 3 files changed, 26 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/prctl.h b/include/linux/prctl.h
> index 4eb4110..4fdb417 100644
> --- a/include/linux/prctl.h
> +++ b/include/linux/prctl.h
> @@ -105,8 +105,10 @@
> /* 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
> +# define PR_NETWORK_ON 0
> +# define PR_NETWORK_ENABLE_DN 1
> +# define PR_NETWORK_OFF 2
> +# define PR_NETWORK_ALL_FLAGS 3
> +# define PR_NETWORK_DN_FLAGS 3
>
> #endif /* _LINUX_PRCTL_H */
> diff --git a/kernel/sys.c b/kernel/sys.c
> index 1fadf10..4c7ef83 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -1608,7 +1608,19 @@ long prctl_set_network(unsigned long network_flags)
> if (current->network & ~network_flags)
> return -EPERM;
>
> - current->network = network_flags;
> + /* Only the superuser may permit a process to enable disablenetwork. */
> + if (!(current->network & PR_NETWORK_ENABLE_DN) &&
> + network_flags & PR_NETWORK_ENABLE_DN &&
> + !capable(CAP_SETPCAP))
Please use CAP_NET_ADMIN for this feature (and add the corresponding
comment in include/linux/capabilities.h).
Thanks
Andrew
> + return -EPERM;
> +
> + /* Only dn-enabled processes may activate disablenetwork. */
> + if (!(current->network & PR_NETWORK_OFF) &&
> + network_flags & PR_NETWORK_OFF &&
> + !(current->network & PR_NETWORK_ENABLE_DN))
> + return -EPERM;
> +
> + current->network |= network_flags;
> return 0;
> }
>
> diff --git a/security/disablenetwork.c b/security/disablenetwork.c
> index 27b88d7..02c0150 100644
> --- a/security/disablenetwork.c
> +++ b/security/disablenetwork.c
> @@ -19,10 +19,11 @@
> #include <net/sock.h>
> #include <linux/socket.h>
> #include <linux/disablenetwork.h>
> +#include <linux/prctl.h>
>
> -static inline int maybe_allow(void)
> +static inline int maybe_allow(unsigned long network_flags)
> {
> - if (current->network)
> + if ((network_flags & PR_NETWORK_DN_FLAGS) == PR_NETWORK_DN_FLAGS)
> return -EPERM;
> return 0;
> }
> @@ -32,7 +33,7 @@ int disablenetwork_security_socket_create(int family, int type,
> {
> if (family == AF_UNIX)
> return 0;
> - return maybe_allow();
> + return maybe_allow(current->network);
> }
>
> int disablenetwork_security_socket_bind(struct socket * sock,
> @@ -41,7 +42,7 @@ int disablenetwork_security_socket_bind(struct socket * sock,
> {
> if (address->sa_family == AF_UNIX)
> return 0;
> - return maybe_allow();
> + return maybe_allow(current->network);
> }
>
> int disablenetwork_security_socket_connect(struct socket * sock,
> @@ -50,7 +51,7 @@ int disablenetwork_security_socket_connect(struct socket * sock,
> {
> if (address->sa_family == AF_UNIX)
> return 0;
> - return maybe_allow();
> + return maybe_allow(current->network);
> }
>
> int disablenetwork_security_socket_sendmsg(struct socket * sock,
> @@ -59,14 +60,14 @@ int disablenetwork_security_socket_sendmsg(struct socket * sock,
> /* permit sockets which are PF_UNIX or connected; check others. */
> if (sock->sk->sk_family == PF_UNIX || msg->msg_name == NULL)
> return 0;
> - return maybe_allow();
> + return maybe_allow(current->network);
> }
>
> int disablenetwork_security_ptrace_access_check(struct task_struct *child,
> unsigned int mode)
> {
> /* does current have networking restrictions not shared by child? */
> - if (current->network & ~child->network)
> + if (maybe_allow(current->network) && !maybe_allow(child->network))
> return -EPERM;
> return 0;
> }
> --
> 1.6.6.rc2
>
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