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>

1 files changed, 157 insertions, 0 deletions

diff --git a/Documentation/security/SELinux-sctp.rst b/Documentation/security/SELinux-sctp.rst
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+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.