[NetLabel]: protect the CIPSOv4 socket option from setsockopt()

This patch makes two changes to protect applications from either removing or
tampering with the CIPSOv4 IP option on a socket.  The first is the requirement
that applications have the CAP_NET_RAW capability to set an IPOPT_CIPSO option
on a socket; this prevents untrusted applications from setting their own
CIPSOv4 security attributes on the packets they send.  The second change is to
SELinux and it prevents applications from setting any IPv4 options when there
is an IPOPT_CIPSO option already present on the socket; this prevents
applications from removing CIPSOv4 security attributes from the packets they
send.

Signed-off-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 37 insertions, 0 deletions

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index b1f6fb36c699..bfe122764c98 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -2682,4 +2682,41 @@ u32 selinux_netlbl_socket_getpeersec_dgram(struct sk_buff *skb)
 
         return peer_sid;
 }
+
+/**
+ * selinux_netlbl_socket_setsockopt - Do not allow users to remove a NetLabel
+ * @sock: the socket
+ * @level: the socket level or protocol
+ * @optname: the socket option name
+ *
+ * Description:
+ * Check the setsockopt() call and if the user is trying to replace the IP
+ * options on a socket and a NetLabel is in place for the socket deny the
+ * access; otherwise allow the access.  Returns zero when the access is
+ * allowed, -EACCES when denied, and other negative values on error.
+ *
+ */
+int selinux_netlbl_socket_setsockopt(struct socket *sock,
+                                     int level,
+                                     int optname)
+{
+        int rc = 0;
+        struct inode *inode = SOCK_INODE(sock);
+        struct sk_security_struct *sksec = sock->sk->sk_security;
+        struct inode_security_struct *isec = inode->i_security;
+        struct netlbl_lsm_secattr secattr;
+
+        mutex_lock(&isec->lock);
+        if (level == IPPROTO_IP && optname == IP_OPTIONS &&
+            sksec->nlbl_state == NLBL_LABELED) {
+                netlbl_secattr_init(&secattr);
+                rc = netlbl_socket_getattr(sock, &secattr);
+                if (rc == 0 && (secattr.cache || secattr.mls_lvl_vld))
+                        rc = -EACCES;
+                netlbl_secattr_destroy(&secattr);
+        }
+        mutex_unlock(&isec->lock);
+
+        return rc;
+}
 #endif /* CONFIG_NETLABEL */