security: Add support for SCTP security hooks

The SCTP security hooks are explained in:
Documentation/security/LSM-sctp.rst

Signed-off-by: Richard Haines <richard_c_haines@btinternet.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

Documentation/security/LSM-sctp.rst

@@ -0,0 +1,175 @@
+SCTP LSM Support
+================
+
+For security module support, three SCTP specific hooks have been implemented::
+
+    security_sctp_assoc_request()
+    security_sctp_bind_connect()
+    security_sctp_sk_clone()
+
+Also the following security hook has been utilised::
+
+    security_inet_conn_established()
+
+The usage of these hooks are described below with the SELinux implementation
+described in ``Documentation/security/SELinux-sctp.rst``
+
+
+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.
+
+
+security_sctp_bind_connect()
+-----------------------------
+Passes one or more ipv4/ipv6 addresses to the security module for validation
+based on the ``@optname`` that will result in either a bind or connect
+service as shown in the permission check tables below.
+Returns 0 on success, error on failure.
+::
+
+    @sk      - Pointer to sock structure.
+    @optname - Name of the option to validate.
+    @address - One or more ipv4 / ipv6 addresses.
+    @addrlen - The total length of address(s). This is calculated on each
+               ipv4 or ipv6 address using sizeof(struct sockaddr_in) or
+               sizeof(struct sockaddr_in6).
+
+  ------------------------------------------------------------------
+  |                     BIND Type 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 Type 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       |
+  ------------------------------------------------------------------
+
+A summary of the ``@optname`` entries is as follows::
+
+    SCTP_SOCKOPT_BINDX_ADD - Allows additional bind addresses to be
+                             associated after (optionally) calling
+                             bind(3).
+                             sctp_bindx(3) adds a set of bind
+                             addresses on a socket.
+
+    SCTP_SOCKOPT_CONNECTX - Allows the allocation of multiple
+                            addresses for reaching a peer
+                            (multi-homed).
+                            sctp_connectx(3) initiates a connection
+                            on an SCTP socket using multiple
+                            destination addresses.
+
+    SCTP_SENDMSG_CONNECT  - Initiate a connection that is generated by a
+                            sendmsg(2) or sctp_sendmsg(3) on a new asociation.
+
+    SCTP_PRIMARY_ADDR     - Set local primary address.
+
+    SCTP_SET_PEER_PRIMARY_ADDR - Request peer sets address as
+                                 association primary.
+
+    SCTP_PARAM_ADD_IP          - These are used when Dynamic Address
+    SCTP_PARAM_SET_PRIMARY     - Reconfiguration is enabled as explained below.
+
+
+To support Dynamic Address Reconfiguration the following parameters must be
+enabled on both endpoints (or use the appropriate **setsockopt**\(2))::
+
+    /proc/sys/net/sctp/addip_enable
+    /proc/sys/net/sctp/addip_noauth_enable
+
+then the following *_PARAM_*'s are sent to the peer in an
+ASCONF chunk when the corresponding ``@optname``'s are present::
+
+          @optname                      ASCONF Parameter
+         ----------                    ------------------
+    SCTP_SOCKOPT_BINDX_ADD     ->   SCTP_PARAM_ADD_IP
+    SCTP_SET_PEER_PRIMARY_ADDR ->   SCTP_PARAM_SET_PRIMARY
+
+
+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).
+::
+
+    @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::
+
+    @sk  - pointer to sock structure.
+    @skb - pointer to skbuff of the COOKIE ACK packet.
+
+
+Security Hooks used for Association Establishment
+=================================================
+The following diagram shows the use of ``security_sctp_bind_connect()``,
+``security_sctp_assoc_request()``, ``security_inet_conn_established()`` when
+establishing an association.
+::
+
+      SCTP endpoint "A"                                SCTP endpoint "Z"
+      =================                                =================
+    sctp_sf_do_prm_asoc()
+ Association setup can be initiated
+ by a connect(2), sctp_connectx(3),
+ sendmsg(2) or sctp_sendmsg(3).
+ These will result in a call to
+ security_sctp_bind_connect() to
+ initiate an association to
+ SCTP peer endpoint "Z".
+         INIT --------------------------------------------->
+                                                   sctp_sf_do_5_1B_init()
+                                                 Respond to an INIT chunk.
+                                             SCTP peer endpoint "A" is
+                                             asking for an association. Call
+                                             security_sctp_assoc_request()
+                                             to set the peer label if first
+                                             association.
+                                             If not first association, check
+                                             whether allowed, IF so send:
+          <----------------------------------------------- INIT ACK
+          |                                  ELSE audit event and silently
+          |                                       discard the packet.
+          |
+    COOKIE ECHO ------------------------------------------>
+                                                          |
+                                                          |
+                                                          |
+          <------------------------------------------- COOKIE ACK
+          |                                               |
+    sctp_sf_do_5_1E_ca                                    |
+ Call security_inet_conn_established()                    |
+ to set the peer label.                                   |
+          |                                               |
+          |                               If SCTP_SOCKET_TCP or peeled off
+          |                               socket security_sctp_sk_clone() is
+          |                               called to clone the new socket.
+          |                                               |
+      ESTABLISHED                                    ESTABLISHED
+          |                                               |
+    ------------------------------------------------------------------
+    |                     Association Established                    |
+    ------------------------------------------------------------------
+
+

include/linux/lsm_hooks.h

@@ -906,6 +906,33 @@
  *	associated with the TUN device's security structure.
  *	@security pointer to the TUN devices's security structure.
  *
+ * Security hooks for SCTP
+ *
+ * @sctp_assoc_request:
+ *	Passes the @ep and @chunk->skb of the association INIT packet to
+ *	the security module.
+ *	@ep pointer to sctp endpoint structure.
+ *	@skb pointer to skbuff of association packet.
+ *	Return 0 on success, error on failure.
+ * @sctp_bind_connect:
+ *	Validiate permissions required for each address associated with sock
+ *	@sk. Depending on @optname, the addresses will be treated as either
+ *	for a connect or bind service. The @addrlen is calculated on each
+ *	ipv4 and ipv6 address using sizeof(struct sockaddr_in) or
+ *	sizeof(struct sockaddr_in6).
+ *	@sk pointer to sock structure.
+ *	@optname name of the option to validate.
+ *	@address list containing one or more ipv4/ipv6 addresses.
+ *	@addrlen total length of address(s).
+ *	Return 0 on success, error on failure.
+ * @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).
+ *	@ep pointer to current sctp endpoint structure.
+ *	@sk pointer to current sock structure.
+ *	@sk pointer to new sock structure.
+ *
  * Security hooks for Infiniband
  *
  * @ib_pkey_access:
@@ -1665,6 +1692,12 @@ union security_list_options {
 	int (*tun_dev_attach_queue)(void *security);
 	int (*tun_dev_attach)(struct sock *sk, void *security);
 	int (*tun_dev_open)(void *security);
+	int (*sctp_assoc_request)(struct sctp_endpoint *ep,
+				  struct sk_buff *skb);
+	int (*sctp_bind_connect)(struct sock *sk, int optname,
+				 struct sockaddr *address, int addrlen);
+	void (*sctp_sk_clone)(struct sctp_endpoint *ep, struct sock *sk,
+			      struct sock *newsk);
 #endif	/* CONFIG_SECURITY_NETWORK */
 
 #ifdef CONFIG_SECURITY_INFINIBAND
@@ -1914,6 +1947,9 @@ struct security_hook_heads {
 	struct list_head tun_dev_attach_queue;
 	struct list_head tun_dev_attach;
 	struct list_head tun_dev_open;
+	struct list_head sctp_assoc_request;
+	struct list_head sctp_bind_connect;
+	struct list_head sctp_sk_clone;
 #endif	/* CONFIG_SECURITY_NETWORK */
 #ifdef CONFIG_SECURITY_INFINIBAND
 	struct list_head ib_pkey_access;

include/linux/security.h

@@ -115,6 +115,7 @@ struct xfrm_policy;
 struct xfrm_state;
 struct xfrm_user_sec_ctx;
 struct seq_file;
+struct sctp_endpoint;
 
 #ifdef CONFIG_MMU
 extern unsigned long mmap_min_addr;
@@ -1229,6 +1230,11 @@ int security_tun_dev_create(void);
 int security_tun_dev_attach_queue(void *security);
 int security_tun_dev_attach(struct sock *sk, void *security);
 int security_tun_dev_open(void *security);
+int security_sctp_assoc_request(struct sctp_endpoint *ep, struct sk_buff *skb);
+int security_sctp_bind_connect(struct sock *sk, int optname,
+			       struct sockaddr *address, int addrlen);
+void security_sctp_sk_clone(struct sctp_endpoint *ep, struct sock *sk,
+			    struct sock *newsk);
 
 #else	/* CONFIG_SECURITY_NETWORK */
 static inline int security_unix_stream_connect(struct sock *sock,
@@ -1421,6 +1427,25 @@ static inline int security_tun_dev_open(void *security)
 {
 	return 0;
 }
+
+static inline int security_sctp_assoc_request(struct sctp_endpoint *ep,
+					      struct sk_buff *skb)
+{
+	return 0;
+}
+
+static inline int security_sctp_bind_connect(struct sock *sk, int optname,
+					     struct sockaddr *address,
+					     int addrlen)
+{
+	return 0;
+}
+
+static inline void security_sctp_sk_clone(struct sctp_endpoint *ep,
+					  struct sock *sk,
+					  struct sock *newsk)
+{
+}
 #endif	/* CONFIG_SECURITY_NETWORK */
 
 #ifdef CONFIG_SECURITY_INFINIBAND

security/security.c

@@ -1473,6 +1473,7 @@ void security_inet_conn_established(struct sock *sk,
 {
 	call_void_hook(inet_conn_established, sk, skb);
 }
+EXPORT_SYMBOL(security_inet_conn_established);
 
 int security_secmark_relabel_packet(u32 secid)
 {
@@ -1528,6 +1529,27 @@ int security_tun_dev_open(void *security)
 }
 EXPORT_SYMBOL(security_tun_dev_open);
 
+int security_sctp_assoc_request(struct sctp_endpoint *ep, struct sk_buff *skb)
+{
+	return call_int_hook(sctp_assoc_request, 0, ep, skb);
+}
+EXPORT_SYMBOL(security_sctp_assoc_request);
+
+int security_sctp_bind_connect(struct sock *sk, int optname,
+			       struct sockaddr *address, int addrlen)
+{
+	return call_int_hook(sctp_bind_connect, 0, sk, optname,
+			     address, addrlen);
+}
+EXPORT_SYMBOL(security_sctp_bind_connect);
+
+void security_sctp_sk_clone(struct sctp_endpoint *ep, struct sock *sk,
+			    struct sock *newsk)
+{
+	call_void_hook(sctp_sk_clone, ep, sk, newsk);
+}
+EXPORT_SYMBOL(security_sctp_sk_clone);
+
 #endif	/* CONFIG_SECURITY_NETWORK */
 
 #ifdef CONFIG_SECURITY_INFINIBAND