[LSM]: Networking netlink socket capability hooks.

include/linux/security.h

@@ -31,7 +31,8 @@
 #include <linux/shm.h>
 #include <linux/msg.h>
 #include <linux/sched.h>
-
+#include <linux/skbuff.h>
+#include <linux/netlink.h>
 
 /*
  * These functions are in security/capability.c and are used
@@ -48,6 +49,20 @@ extern int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
 extern void cap_task_kmod_set_label (void);
 extern void cap_task_reparent_to_init (struct task_struct *p);
 
+static inline int cap_netlink_send (struct sk_buff *skb)
+{
+	NETLINK_CB (skb).eff_cap = current->cap_effective;
+	return 0;
+}
+
+static inline int cap_netlink_recv (struct sk_buff *skb)
+{
+	if (!cap_raised (NETLINK_CB (skb).eff_cap, CAP_NET_ADMIN))
+		return -EPERM;
+	return 0;
+}
+
+
 /*
  * Values used in the task_security_ops calls
  */
@@ -64,11 +79,6 @@ extern void cap_task_reparent_to_init (struct task_struct *p);
 #define LSM_SETID_FS	8
 
 /* forward declares to avoid warnings */
-struct sock;
-struct socket;
-struct sockaddr;
-struct msghdr;
-struct sk_buff;
 struct nfsctl_arg;
 struct sched_param;
 struct swap_info_struct;
@@ -588,6 +598,21 @@ struct swap_info_struct;
  * 	is being reparented to the init task.
  *	@p contains the task_struct for the kernel thread.
  *
+ * Security hooks for Netlink messaging.
+ *
+ * @netlink_send:
+ *	Save security information for a netlink message so that permission
+ *	checking can be performed when the message is processed.  The security
+ *	information can be saved using the eff_cap field of the
+ *      netlink_skb_parms structure.
+ *	@skb contains the sk_buff structure for the netlink message.
+ *	Return 0 if the information was successfully saved.
+ * @netlink_recv:
+ *	Check permission before processing the received netlink message in
+ *	@skb.
+ *	@skb contains the sk_buff structure for the netlink message.
+ *	Return 0 if permission is granted.
+ *
  * Security hooks for Unix domain networking.
  *
  * @unix_stream_connect:
@@ -1077,6 +1102,9 @@ struct security_operations {
 	int (*sem_semop) (struct sem_array * sma, 
 			  struct sembuf * sops, unsigned nsops, int alter);
 
+	int (*netlink_send) (struct sk_buff * skb);
+	int (*netlink_recv) (struct sk_buff * skb);
+
 	/* allow module stacking */
 	int (*register_security) (const char *name,
 	                          struct security_operations *ops);
@@ -1701,6 +1729,16 @@ static inline int security_sem_semop (struct sem_array * sma,
 	return security_ops->sem_semop(sma, sops, nsops, alter);
 }
 
+static inline int security_netlink_send(struct sk_buff * skb)
+{
+	return security_ops->netlink_send(skb);
+}
+
+static inline int security_netlink_recv(struct sk_buff * skb)
+{
+	return security_ops->netlink_recv(skb);
+}
+
 /* prototypes */
 extern int security_scaffolding_startup	(void);
 extern int register_security	(struct security_operations *ops);
@@ -2262,6 +2300,21 @@ static inline int security_sem_semop (struct sem_array * sma,
 	return 0;
 }
 
+/*
+ * The netlink capability defaults need to be used inline by default
+ * (rather than hooking into the capability module) to reduce overhead
+ * in the networking code.
+ */
+static inline int security_netlink_send (struct sk_buff *skb)
+{
+	return cap_netlink_send (skb);
+}
+
+static inline int security_netlink_recv (struct sk_buff *skb)
+{
+	return cap_netlink_recv (skb);
+}
+
 #endif	/* CONFIG_SECURITY */
 
 #ifdef CONFIG_SECURITY_NETWORK

net/core/rtnetlink.c

@@ -34,6 +34,7 @@
 #include <linux/capability.h>
 #include <linux/skbuff.h>
 #include <linux/init.h>
+#include <linux/security.h>
 
 #include <asm/uaccess.h>
 #include <asm/system.h>
@@ -363,7 +364,7 @@ rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, int *errp)
 	sz_idx = type>>2;
 	kind = type&3;
 
-	if (kind != 2 && !cap_raised(NETLINK_CB(skb).eff_cap, CAP_NET_ADMIN)) {
+	if (kind != 2 && security_netlink_recv(skb)) {
 		*errp = -EPERM;
 		return -1;
 	}

net/ipv4/netfilter/ip_queue.c

@@ -26,6 +26,7 @@
 #include <linux/brlock.h>
 #include <linux/sysctl.h>
 #include <linux/proc_fs.h>
+#include <linux/security.h>
 #include <net/sock.h>
 #include <net/route.h>
 
@@ -496,7 +497,7 @@ ipq_rcv_skb(struct sk_buff *skb)
 	if (type <= IPQM_BASE)
 		return;
 		
-	if(!cap_raised(NETLINK_CB(skb).eff_cap, CAP_NET_ADMIN))
+	if (security_netlink_recv(skb))
 		RCV_SKB_FAIL(-EPERM);
 	
 	write_lock_bh(&queue_lock);

net/ipv4/xfrm_user.c

@@ -16,6 +16,7 @@
 #include <linux/pfkeyv2.h>
 #include <linux/ipsec.h>
 #include <linux/init.h>
+#include <linux/security.h>
 #include <net/sock.h>
 #include <net/xfrm.h>
 
@@ -774,7 +775,7 @@ static int xfrm_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, int *err
 	link = &xfrm_dispatch[type];
 
 	/* All operations require privileges, even GET */
-	if (!cap_raised(NETLINK_CB(skb).eff_cap, CAP_NET_ADMIN)) {
+	if (security_netlink_recv(skb)) {
 		*errp = -EPERM;
 		return -1;
 	}

net/ipv6/netfilter/ip6_queue.c

@@ -539,7 +539,7 @@ ipq_rcv_skb(struct sk_buff *skb)
 	if (type <= IPQM_BASE)
 		return;
 	
-	if(!cap_raised(NETLINK_CB(skb).eff_cap, CAP_NET_ADMIN))
+	if (security_netlink_recv(skb))
 		RCV_SKB_FAIL(-EPERM);	
 
 	write_lock_bh(&queue_lock);

net/netlink/af_netlink.c

@@ -42,6 +42,7 @@
 #include <linux/proc_fs.h>
 #include <linux/smp_lock.h>
 #include <linux/notifier.h>
+#include <linux/security.h>
 #include <net/sock.h>
 #include <net/scm.h>
 
@@ -636,7 +637,12 @@ static int netlink_sendmsg(struct kiocb *iocb, struct socket *sock,
 	   check them, when this message will be delivered
 	   to corresponding kernel module.   --ANK (980802)
 	 */
-	NETLINK_CB(skb).eff_cap = current->cap_effective;
+
+	err = security_netlink_send(skb);
+	if (err) {
+		kfree_skb(skb);
+		goto out;
+	}
 
 	err = -EFAULT;
 	if (memcpy_fromiovec(skb_put(skb,len), msg->msg_iov, len)) {

security/capability.c

@@ -282,6 +282,8 @@ static struct security_operations capability_ops = {
 	.capset_check =			cap_capset_check,
 	.capset_set =			cap_capset_set,
 	.capable =			cap_capable,
+	.netlink_send =			cap_netlink_send,
+	.netlink_recv =			cap_netlink_recv,
 
 	.bprm_compute_creds =		cap_bprm_compute_creds,
 	.bprm_set_security =		cap_bprm_set_security,

security/dummy.c

@@ -597,6 +597,22 @@ static int dummy_sem_semop (struct sem_array *sma,
 	return 0;
 }
 
+static int dummy_netlink_send (struct sk_buff *skb)
+{
+	if (current->euid == 0)
+		cap_raise (NETLINK_CB (skb).eff_cap, CAP_NET_ADMIN);
+	else
+		NETLINK_CB (skb).eff_cap = 0;
+	return 0;
+}
+
+static int dummy_netlink_recv (struct sk_buff *skb)
+{
+	if (!cap_raised (NETLINK_CB (skb).eff_cap, CAP_NET_ADMIN))
+		return -EPERM;
+	return 0;
+}
+
 #ifdef CONFIG_SECURITY_NETWORK
 static int dummy_unix_stream_connect (struct socket *sock,
 				      struct socket *other,
@@ -819,6 +835,8 @@ void security_fixup_ops (struct security_operations *ops)
 	set_to_dummy_if_null(ops, sem_associate);
 	set_to_dummy_if_null(ops, sem_semctl);
 	set_to_dummy_if_null(ops, sem_semop);
+	set_to_dummy_if_null(ops, netlink_send);
+	set_to_dummy_if_null(ops, netlink_recv);
 	set_to_dummy_if_null(ops, register_security);
 	set_to_dummy_if_null(ops, unregister_security);
 #ifdef CONFIG_SECURITY_NETWORK