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Message-ID: <20100115081308.GA14443@heat>
Date: Fri, 15 Jan 2010 03:13:08 -0500
From: Michael Stone <michael@...top.org>
To: linux-kernel@...r.kernel.org
Cc: 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>,
Andrew Morgan <morgan@...nel.org>,
Michael Stone <michael@...top.org>
Subject: disablenetwork (v5): Require CAP_SETPCAP to enable disablenetwork.
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))
+ 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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