selinux: Add SCTP support

The SELinux SCTP implementation is explained in:
Documentation/security/SELinux-sctp.rst
Signed-off-by: Richard Haines <richard_c_haines@btinternet.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

Documentation/security/SELinux-sctp.rst

+SCTP SELinux Support
+=====================
+
+Security Hooks
+===============
+
+``Documentation/security/LSM-sctp.rst`` describes the following SCTP security
+hooks with the SELinux specifics expanded below::
+
+    security_sctp_assoc_request()
+    security_sctp_bind_connect()
+    security_sctp_sk_clone()
+    security_inet_conn_established()
+
+
+security_sctp_assoc_request()
+-----------------------------
+Passes the ``@ep`` and ``@chunk->skb`` of the association INIT packet to the
+security module. Returns 0 on success, error on failure.
+::
+
+    @ep - pointer to sctp endpoint structure.
+    @skb - pointer to skbuff of association packet.
+
+The security module performs the following operations:
+     IF this is the first association on ``@ep->base.sk``, then set the peer
+     sid to that in ``@skb``. This will ensure there is only one peer sid
+     assigned to ``@ep->base.sk`` that may support multiple associations.
+
+     ELSE validate the ``@ep->base.sk peer_sid`` against the ``@skb peer sid``
+     to determine whether the association should be allowed or denied.
+
+     Set the sctp ``@ep sid`` to socket's sid (from ``ep->base.sk``) with
+     MLS portion taken from ``@skb peer sid``. This will be used by SCTP
+     TCP style sockets and peeled off connections as they cause a new socket
+     to be generated.
+
+     If IP security options are configured (CIPSO/CALIPSO), then the ip
+     options are set on the socket.
+
+
+security_sctp_bind_connect()
+-----------------------------
+Checks permissions required for ipv4/ipv6 addresses based on the ``@optname``
+as follows::
+
+  ------------------------------------------------------------------
+  |                   BIND Permission Checks                       |
+  |       @optname             |         @address contains         |
+  |----------------------------|-----------------------------------|
+  | SCTP_SOCKOPT_BINDX_ADD     | One or more ipv4 / ipv6 addresses |
+  | SCTP_PRIMARY_ADDR          | Single ipv4 or ipv6 address       |
+  | SCTP_SET_PEER_PRIMARY_ADDR | Single ipv4 or ipv6 address       |
+  ------------------------------------------------------------------
+
+  ------------------------------------------------------------------
+  |                 CONNECT Permission Checks                      |
+  |       @optname             |         @address contains         |
+  |----------------------------|-----------------------------------|
+  | SCTP_SOCKOPT_CONNECTX      | One or more ipv4 / ipv6 addresses |
+  | SCTP_PARAM_ADD_IP          | One or more ipv4 / ipv6 addresses |
+  | SCTP_SENDMSG_CONNECT       | Single ipv4 or ipv6 address       |
+  | SCTP_PARAM_SET_PRIMARY     | Single ipv4 or ipv6 address       |
+  ------------------------------------------------------------------
+
+
+``Documentation/security/LSM-sctp.rst`` gives a summary of the ``@optname``
+entries and also describes ASCONF chunk processing when Dynamic Address
+Reconfiguration is enabled.
+
+
+security_sctp_sk_clone()
+-------------------------
+Called whenever a new socket is created by **accept**\(2) (i.e. a TCP style
+socket) or when a socket is 'peeled off' e.g userspace calls
+**sctp_peeloff**\(3). ``security_sctp_sk_clone()`` will set the new
+sockets sid and peer sid to that contained in the ``@ep sid`` and
+``@ep peer sid`` respectively.
+::
+
+    @ep - pointer to current sctp endpoint structure.
+    @sk - pointer to current sock structure.
+    @sk - pointer to new sock structure.
+
+
+security_inet_conn_established()
+---------------------------------
+Called when a COOKIE ACK is received where it sets the connection's peer sid
+to that in ``@skb``::
+
+    @sk  - pointer to sock structure.
+    @skb - pointer to skbuff of the COOKIE ACK packet.
+
+
+Policy Statements
+==================
+The following class and permissions to support SCTP are available within the
+kernel::
+
+    class sctp_socket inherits socket { node_bind }
+
+whenever the following policy capability is enabled::
+
+    policycap extended_socket_class;
+
+SELinux SCTP support adds the ``name_connect`` permission for connecting
+to a specific port type and the ``association`` permission that is explained
+in the section below.
+
+If userspace tools have been updated, SCTP will support the ``portcon``
+statement as shown in the following example::
+
+    portcon sctp 1024-1036 system_u:object_r:sctp_ports_t:s0
+
+
+SCTP Peer Labeling
+===================
+An SCTP socket will only have one peer label assigned to it. This will be
+assigned during the establishment of the first association. Once the peer
+label has been assigned, any new associations will have the ``association``
+permission validated by checking the socket peer sid against the received
+packets peer sid to determine whether the association should be allowed or
+denied.
+
+NOTES:
+   1) If peer labeling is not enabled, then the peer context will always be
+      ``SECINITSID_UNLABELED`` (``unlabeled_t`` in Reference Policy).
+
+   2) As SCTP can support more than one transport address per endpoint
+      (multi-homing) on a single socket, it is possible to configure policy
+      and NetLabel to provide different peer labels for each of these. As the
+      socket peer label is determined by the first associations transport
+      address, it is recommended that all peer labels are consistent.
+
+   3) **getpeercon**\(3) may be used by userspace to retrieve the sockets peer
+      context.
+
+   4) While not SCTP specific, be aware when using NetLabel that if a label
+      is assigned to a specific interface, and that interface 'goes down',
+      then the NetLabel service will remove the entry. Therefore ensure that
+      the network startup scripts call **netlabelctl**\(8) to set the required
+      label (see **netlabel-config**\(8) helper script for details).
+
+   5) The NetLabel SCTP peer labeling rules apply as discussed in the following
+      set of posts tagged "netlabel" at: http://www.paul-moore.com/blog/t.
+
+   6) CIPSO is only supported for IPv4 addressing: ``socket(AF_INET, ...)``
+      CALIPSO is only supported for IPv6 addressing: ``socket(AF_INET6, ...)``
+
+      Note the following when testing CIPSO/CALIPSO:
+         a) CIPSO will send an ICMP packet if an SCTP packet cannot be
+            delivered because of an invalid label.
+         b) CALIPSO does not send an ICMP packet, just silently discards it.
+
+   7) IPSEC is not supported as RFC 3554 - sctp/ipsec support has not been
+      implemented in userspace (**racoon**\(8) or **ipsec_pluto**\(8)),
+      although the kernel supports SCTP/IPSEC.

security/selinux/include/classmap.h

@@ -176,7 +176,7 @@ struct security_class_mapping secclass_map[] = {
 	  { COMMON_CAP2_PERMS, NULL } },
 	{ "sctp_socket",
 	  { COMMON_SOCK_PERMS,
-	    "node_bind", NULL } },
+	    "node_bind", "name_connect", "association", NULL } },
 	{ "icmp_socket",
 	  { COMMON_SOCK_PERMS,
 	    "node_bind", NULL } },

security/selinux/include/netlabel.h

@@ -32,6 +32,7 @@
 #include <linux/skbuff.h>
 #include <net/sock.h>
 #include <net/request_sock.h>
+#include <net/sctp/structs.h>
 
 #include "avc.h"
 #include "objsec.h"
@@ -52,9 +53,11 @@ int selinux_netlbl_skbuff_getsid(struct sk_buff *skb,
 int selinux_netlbl_skbuff_setsid(struct sk_buff *skb,
 				 u16 family,
 				 u32 sid);
-
+int selinux_netlbl_sctp_assoc_request(struct sctp_endpoint *ep,
+				     struct sk_buff *skb);
 int selinux_netlbl_inet_conn_request(struct request_sock *req, u16 family);
 void selinux_netlbl_inet_csk_clone(struct sock *sk, u16 family);
+void selinux_netlbl_sctp_sk_clone(struct sock *sk, struct sock *newsk);
 int selinux_netlbl_socket_post_create(struct sock *sk, u16 family);
 int selinux_netlbl_sock_rcv_skb(struct sk_security_struct *sksec,
 				struct sk_buff *skb,
@@ -64,6 +67,8 @@ int selinux_netlbl_socket_setsockopt(struct socket *sock,
 				     int level,
 				     int optname);
 int selinux_netlbl_socket_connect(struct sock *sk, struct sockaddr *addr);
+int selinux_netlbl_socket_connect_locked(struct sock *sk,
+					 struct sockaddr *addr);
 
 #else
 static inline void selinux_netlbl_cache_invalidate(void)
@@ -113,6 +118,11 @@ static inline int selinux_netlbl_conn_setsid(struct sock *sk,
 	return 0;
 }
 
+static inline int selinux_netlbl_sctp_assoc_request(struct sctp_endpoint *ep,
+						    struct sk_buff *skb)
+{
+	return 0;
+}
 static inline int selinux_netlbl_inet_conn_request(struct request_sock *req,
 						   u16 family)
 {
@@ -122,6 +132,10 @@ static inline void selinux_netlbl_inet_csk_clone(struct sock *sk, u16 family)
 {
 	return;
 }
+static inline void selinux_netlbl_sctp_sk_clone(struct sock *sk, sock *newsk)
+{
+	return;
+}
 static inline int selinux_netlbl_socket_post_create(struct sock *sk,
 						    u16 family)
 {
@@ -145,6 +159,11 @@ static inline int selinux_netlbl_socket_connect(struct sock *sk,
 {
 	return 0;
 }
+static inline int selinux_netlbl_socket_connect_locked(struct sock *sk,
+						       struct sockaddr *addr)
+{
+	return 0;
+}
 #endif /* CONFIG_NETLABEL */
 
 #endif

security/selinux/include/objsec.h

@@ -130,6 +130,10 @@ struct sk_security_struct {
 	u32 sid;			/* SID of this object */
 	u32 peer_sid;			/* SID of peer */
 	u16 sclass;			/* sock security class */
+	enum {				/* SCTP association state */
+		SCTP_ASSOC_UNSET = 0,
+		SCTP_ASSOC_SET,
+	} sctp_assoc_state;
 };
 
 struct tun_security_struct {

security/selinux/netlabel.c

@@ -249,6 +249,7 @@ int selinux_netlbl_skbuff_setsid(struct sk_buff *skb,
 	sk = skb_to_full_sk(skb);
 	if (sk != NULL) {
 		struct sk_security_struct *sksec = sk->sk_security;
+
 		if (sksec->nlbl_state != NLBL_REQSKB)
 			return 0;
 		secattr = selinux_netlbl_sock_getattr(sk, sid);
@@ -269,6 +270,61 @@ int selinux_netlbl_skbuff_setsid(struct sk_buff *skb,
 	return rc;
 }
 
+/**
+ * selinux_netlbl_sctp_assoc_request - Label an incoming sctp association.
+ * @ep: incoming association endpoint.
+ * @skb: the packet.
+ *
+ * Description:
+ * A new incoming connection is represented by @ep, ......
+ * Returns zero on success, negative values on failure.
+ *
+ */
+int selinux_netlbl_sctp_assoc_request(struct sctp_endpoint *ep,
+				     struct sk_buff *skb)
+{
+	int rc;
+	struct netlbl_lsm_secattr secattr;
+	struct sk_security_struct *sksec = ep->base.sk->sk_security;
+	struct sockaddr *addr;
+	struct sockaddr_in addr4;
+#if IS_ENABLED(CONFIG_IPV6)
+	struct sockaddr_in6 addr6;
+#endif
+
+	if (ep->base.sk->sk_family != PF_INET &&
+				ep->base.sk->sk_family != PF_INET6)
+		return 0;
+
+	netlbl_secattr_init(&secattr);
+	rc = security_netlbl_sid_to_secattr(ep->secid, &secattr);
+	if (rc != 0)
+		goto assoc_request_return;
+
+	/* Move skb hdr address info to a struct sockaddr and then call
+	 * netlbl_conn_setattr().
+	 */
+	if (ip_hdr(skb)->version == 4) {
+		addr4.sin_family = AF_INET;
+		addr4.sin_addr.s_addr = ip_hdr(skb)->saddr;
+		addr = (struct sockaddr *)&addr4;
+#if IS_ENABLED(CONFIG_IPV6)
+	} else {
+		addr6.sin6_family = AF_INET6;
+		addr6.sin6_addr = ipv6_hdr(skb)->saddr;
+		addr = (struct sockaddr *)&addr6;
+#endif
+	}
+
+	rc = netlbl_conn_setattr(ep->base.sk, addr, &secattr);
+	if (rc == 0)
+		sksec->nlbl_state = NLBL_LABELED;
+
+assoc_request_return:
+	netlbl_secattr_destroy(&secattr);
+	return rc;
+}
+
 /**
  * selinux_netlbl_inet_conn_request - Label an incoming stream connection
  * @req: incoming connection request socket
@@ -318,6 +374,22 @@ void selinux_netlbl_inet_csk_clone(struct sock *sk, u16 family)
 		sksec->nlbl_state = NLBL_UNSET;
 }
 
+/**
+ * selinux_netlbl_sctp_sk_clone - Copy state to the newly created sock
+ * @sk: current sock
+ * @newsk: the new sock
+ *
+ * Description:
+ * Called whenever a new socket is created by accept(2) or sctp_peeloff(3).
+ */
+void selinux_netlbl_sctp_sk_clone(struct sock *sk, struct sock *newsk)
+{
+	struct sk_security_struct *sksec = sk->sk_security;
+	struct sk_security_struct *newsksec = newsk->sk_security;
+
+	newsksec->nlbl_state = sksec->nlbl_state;
+}
+
 /**
  * selinux_netlbl_socket_post_create - Label a socket using NetLabel
  * @sock: the socket to label
@@ -469,7 +541,8 @@ int selinux_netlbl_socket_setsockopt(struct socket *sock,
 }
 
 /**
- * selinux_netlbl_socket_connect - Label a client-side socket on connect
+ * selinux_netlbl_socket_connect_helper - Help label a client-side socket on
+ * connect
  * @sk: the socket to label
  * @addr: the destination address
  *
@@ -478,18 +551,13 @@ int selinux_netlbl_socket_setsockopt(struct socket *sock,
  * Returns zero values on success, negative values on failure.
  *
  */
-int selinux_netlbl_socket_connect(struct sock *sk, struct sockaddr *addr)
+static int selinux_netlbl_socket_connect_helper(struct sock *sk,
+						struct sockaddr *addr)
 {
 	int rc;
 	struct sk_security_struct *sksec = sk->sk_security;
 	struct netlbl_lsm_secattr *secattr;
 
-	if (sksec->nlbl_state != NLBL_REQSKB &&
-	    sksec->nlbl_state != NLBL_CONNLABELED)
-		return 0;
-
-	lock_sock(sk);
-
 	/* connected sockets are allowed to disconnect when the address family
 	 * is set to AF_UNSPEC, if that is what is happening we want to reset
 	 * the socket */
@@ -497,18 +565,61 @@ int selinux_netlbl_socket_connect(struct sock *sk, struct sockaddr *addr)
 		netlbl_sock_delattr(sk);
 		sksec->nlbl_state = NLBL_REQSKB;
 		rc = 0;
-		goto socket_connect_return;
+		return rc;
 	}
 	secattr = selinux_netlbl_sock_genattr(sk);
 	if (secattr == NULL) {
 		rc = -ENOMEM;
-		goto socket_connect_return;
+		return rc;
 	}
 	rc = netlbl_conn_setattr(sk, addr, secattr);
 	if (rc == 0)
 		sksec->nlbl_state = NLBL_CONNLABELED;
 
-socket_connect_return:
+	return rc;
+}
+
+/**
+ * selinux_netlbl_socket_connect_locked - Label a client-side socket on
+ * connect
+ * @sk: the socket to label
+ * @addr: the destination address
+ *
+ * Description:
+ * Attempt to label a connected socket that already has the socket locked
+ * with NetLabel using the given address.
+ * Returns zero values on success, negative values on failure.
+ *
+ */
+int selinux_netlbl_socket_connect_locked(struct sock *sk,
+					 struct sockaddr *addr)
+{
+	struct sk_security_struct *sksec = sk->sk_security;
+
+	if (sksec->nlbl_state != NLBL_REQSKB &&
+	    sksec->nlbl_state != NLBL_CONNLABELED)
+		return 0;
+
+	return selinux_netlbl_socket_connect_helper(sk, addr);
+}
+
+/**
+ * selinux_netlbl_socket_connect - Label a client-side socket on connect
+ * @sk: the socket to label
+ * @addr: the destination address
+ *
+ * Description:
+ * Attempt to label a connected socket with NetLabel using the given address.
+ * Returns zero values on success, negative values on failure.
+ *
+ */
+int selinux_netlbl_socket_connect(struct sock *sk, struct sockaddr *addr)
+{
+	int rc;
+
+	lock_sock(sk);
+	rc = selinux_netlbl_socket_connect_locked(sk, addr);
 	release_sock(sk);
+
 	return rc;
 }