selinux: Set socket NetLabel based on connection endpoint

Previous work enabled the use of address based NetLabel selectors, which while
highly useful, brought the potential for additional per-packet overhead when
used.  This patch attempts to solve that by applying NetLabel socket labels
when sockets are connect()'d.  This should alleviate the per-packet NetLabel
labeling for all connected sockets (yes, it even works for connected DGRAM
sockets).

Signed-off-by: Paul Moore <paul.moore@hp.com>
Reviewed-by: James Morris <jmorris@namei.org>

1 files changed, 74 insertions, 0 deletions

diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
index e13d6dbb66ab..23768b9d6b64 100644
--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -1810,6 +1810,80 @@ socket_setattr_failure:
 }
 
 /**
+ * cipso_v4_sock_delattr - Delete the CIPSO option from a socket
+ * @sk: the socket
+ *
+ * Description:
+ * Removes the CIPSO option from a socket, if present.
+ *
+ */
+void cipso_v4_sock_delattr(struct sock *sk)
+{
+	u8 hdr_delta;
+	struct ip_options *opt;
+	struct inet_sock *sk_inet;
+
+	sk_inet = inet_sk(sk);
+	opt = sk_inet->opt;
+	if (opt == NULL || opt->cipso == 0)
+		return;
+
+	if (opt->srr || opt->rr || opt->ts || opt->router_alert) {
+		u8 cipso_len;
+		u8 cipso_off;
+		unsigned char *cipso_ptr;
+		int iter;
+		int optlen_new;
+
+		cipso_off = opt->cipso - sizeof(struct iphdr);
+		cipso_ptr = &opt->__data[cipso_off];
+		cipso_len = cipso_ptr[1];
+
+		if (opt->srr > opt->cipso)
+			opt->srr -= cipso_len;
+		if (opt->rr > opt->cipso)
+			opt->rr -= cipso_len;
+		if (opt->ts > opt->cipso)
+			opt->ts -= cipso_len;
+		if (opt->router_alert > opt->cipso)
+			opt->router_alert -= cipso_len;
+		opt->cipso = 0;
+
+		memmove(cipso_ptr, cipso_ptr + cipso_len,
+			opt->optlen - cipso_off - cipso_len);
+
+		/* determining the new total option length is tricky because of
+		 * the padding necessary, the only thing i can think to do at
+		 * this point is walk the options one-by-one, skipping the
+		 * padding at the end to determine the actual option size and
+		 * from there we can determine the new total option length */
+		iter = 0;
+		optlen_new = 0;
+		while (iter < opt->optlen)
+			if (opt->__data[iter] != IPOPT_NOP) {
+				iter += opt->__data[iter + 1];
+				optlen_new = iter;
+			} else
+				iter++;
+		hdr_delta = opt->optlen;
+		opt->optlen = (optlen_new + 3) & ~3;
+		hdr_delta -= opt->optlen;
+	} else {
+		/* only the cipso option was present on the socket so we can
+		 * remove the entire option struct */
+		sk_inet->opt = NULL;
+		hdr_delta = opt->optlen;
+		kfree(opt);
+	}
+
+	if (sk_inet->is_icsk && hdr_delta > 0) {
+		struct inet_connection_sock *sk_conn = inet_csk(sk);
+		sk_conn->icsk_ext_hdr_len -= hdr_delta;
+		sk_conn->icsk_sync_mss(sk, sk_conn->icsk_pmtu_cookie);
+	}
+}
+
+/**
  * cipso_v4_getattr - Helper function for the cipso_v4_*_getattr functions
  * @cipso: the CIPSO v4 option
  * @secattr: the security attributes