Smack: unlabeled outgoing ambient packets

Smack uses CIPSO labeling, but allows for unlabeled packets by
specifying an "ambient" label that is applied to incoming unlabeled
packets.

Because the other end of the connection may dislike IP options, and ssh
is one know application that behaves thus, it is prudent to respond in
kind.

This patch changes the network labeling behavior such that an outgoing
packet that would be given a CIPSO label that matches the ambient label
is left unlabeled.  An "unlbl" domain is added and the netlabel
defaulting mechanism invoked rather than assuming that everything is
CIPSO.  Locking has been added around changes to the ambient label as
the mechanisms used to do so are more involved.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 28 insertions, 8 deletions

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 2b5d6f72f678..25cbfa3f71f4 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1251,9 +1251,8 @@ static void smack_to_secattr(char *smack, struct netlbl_lsm_secattr *nlsp)
 
 	switch (smack_net_nltype) {
 	case NETLBL_NLTYPE_CIPSOV4:
-		nlsp->domain = NULL;
-		nlsp->flags = NETLBL_SECATTR_DOMAIN;
-		nlsp->flags |= NETLBL_SECATTR_MLS_LVL;
+		nlsp->domain = kstrdup(smack, GFP_ATOMIC);
+		nlsp->flags = NETLBL_SECATTR_DOMAIN | NETLBL_SECATTR_MLS_LVL;
 
 		rc = smack_to_cipso(smack, &cipso);
 		if (rc == 0) {
@@ -1282,15 +1281,14 @@ static int smack_netlabel(struct sock *sk)
 {
 	struct socket_smack *ssp;
 	struct netlbl_lsm_secattr secattr;
-	int rc = 0;
+	int rc;
 
 	ssp = sk->sk_security;
 	netlbl_secattr_init(&secattr);
 	smack_to_secattr(ssp->smk_out, &secattr);
-	if (secattr.flags != NETLBL_SECATTR_NONE)
-		rc = netlbl_sock_setattr(sk, &secattr);
-
+	rc = netlbl_sock_setattr(sk, &secattr);
 	netlbl_secattr_destroy(&secattr);
+
 	return rc;
 }
 
@@ -1313,6 +1311,7 @@ static int smack_inode_setsecurity(struct inode *inode, const char *name,
 	struct inode_smack *nsp = inode->i_security;
 	struct socket_smack *ssp;
 	struct socket *sock;
+	int rc = 0;
 
 	if (value == NULL || size > SMK_LABELLEN)
 		return -EACCES;
@@ -1341,7 +1340,10 @@ static int smack_inode_setsecurity(struct inode *inode, const char *name,
 		ssp->smk_in = sp;
 	else if (strcmp(name, XATTR_SMACK_IPOUT) == 0) {
 		ssp->smk_out = sp;
-		return smack_netlabel(sock->sk);
+		rc = smack_netlabel(sock->sk);
+		if (rc != 0)
+			printk(KERN_WARNING "Smack: \"%s\" netlbl error %d.\n",
+			       __func__, -rc);
 	} else
 		return -EOPNOTSUPP;
 
@@ -2214,6 +2216,9 @@ static void smack_sock_graft(struct sock *sk, struct socket *parent)
 	ssp->smk_packet[0] = '\0';
 
 	rc = smack_netlabel(sk);
+	if (rc != 0)
+		printk(KERN_WARNING "Smack: \"%s\" netlbl error %d.\n",
+		       __func__, -rc);
 }
 
 /**
@@ -2346,6 +2351,20 @@ static int smack_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 }
 
 /*
+ * smack_secctx_to_secid - return the secid for a smack label
+ * @secdata: smack label
+ * @seclen: how long result is
+ * @secid: outgoing integer
+ *
+ * Exists for audit and networking code.
+ */
+static int smack_secctx_to_secid(char *secdata, u32 seclen, u32 *secid)
+{
+	*secid = smack_to_secid(secdata);
+	return 0;
+}
+
+/*
  * smack_release_secctx - don't do anything.
  * @key_ref: unused
  * @context: unused
@@ -2475,6 +2494,7 @@ static struct security_operations smack_ops = {
 	.key_permission = 		smack_key_permission,
 #endif /* CONFIG_KEYS */
 	.secid_to_secctx = 		smack_secid_to_secctx,
+	.secctx_to_secid = 		smack_secctx_to_secid,
 	.release_secctx = 		smack_release_secctx,
 };