1 .. SPDX-License-Identifier: GPL-2.0
2
3 ====
4 SCTP
5 ====
6
7 SCTP LSM Support
8 ================
9
10 Security Hooks
11 --------------
12
13 For security module support, three SCTP specific hooks have been implemented::
14
15 security_sctp_assoc_request()
16 security_sctp_bind_connect()
17 security_sctp_sk_clone()
18 security_sctp_assoc_established()
19
20 The usage of these hooks are described below with the SELinux implementation
21 described in the `SCTP SELinux Support`_ chapter.
22
23
24 security_sctp_assoc_request()
25 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
26 Passes the ``@asoc`` and ``@chunk->skb`` of the association INIT packet to the
27 security module. Returns 0 on success, error on failure.
28 ::
29
30 @asoc - pointer to sctp association structure.
31 @skb - pointer to skbuff of association packet.
32
33
34 security_sctp_bind_connect()
35 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
36 Passes one or more ipv4/ipv6 addresses to the security module for validation
37 based on the ``@optname`` that will result in either a bind or connect
38 service as shown in the permission check tables below.
39 Returns 0 on success, error on failure.
40 ::
41
42 @sk - Pointer to sock structure.
43 @optname - Name of the option to validate.
44 @address - One or more ipv4 / ipv6 addresses.
45 @addrlen - The total length of address(s). This is calculated on each
46 ipv4 or ipv6 address using sizeof(struct sockaddr_in) or
47 sizeof(struct sockaddr_in6).
48
49 ------------------------------------------------------------------
50 | BIND Type Checks |
51 | @optname | @address contains |
52 |----------------------------|-----------------------------------|
53 | SCTP_SOCKOPT_BINDX_ADD | One or more ipv4 / ipv6 addresses |
54 | SCTP_PRIMARY_ADDR | Single ipv4 or ipv6 address |
55 | SCTP_SET_PEER_PRIMARY_ADDR | Single ipv4 or ipv6 address |
56 ------------------------------------------------------------------
57
58 ------------------------------------------------------------------
59 | CONNECT Type Checks |
60 | @optname | @address contains |
61 |----------------------------|-----------------------------------|
62 | SCTP_SOCKOPT_CONNECTX | One or more ipv4 / ipv6 addresses |
63 | SCTP_PARAM_ADD_IP | One or more ipv4 / ipv6 addresses |
64 | SCTP_SENDMSG_CONNECT | Single ipv4 or ipv6 address |
65 | SCTP_PARAM_SET_PRIMARY | Single ipv4 or ipv6 address |
66 ------------------------------------------------------------------
67
68 A summary of the ``@optname`` entries is as follows::
69
70 SCTP_SOCKOPT_BINDX_ADD - Allows additional bind addresses to be
71 associated after (optionally) calling
72 bind(3).
73 sctp_bindx(3) adds a set of bind
74 addresses on a socket.
75
76 SCTP_SOCKOPT_CONNECTX - Allows the allocation of multiple
77 addresses for reaching a peer
78 (multi-homed).
79 sctp_connectx(3) initiates a connection
80 on an SCTP socket using multiple
81 destination addresses.
82
83 SCTP_SENDMSG_CONNECT - Initiate a connection that is generated by a
84 sendmsg(2) or sctp_sendmsg(3) on a new association.
85
86 SCTP_PRIMARY_ADDR - Set local primary address.
87
88 SCTP_SET_PEER_PRIMARY_ADDR - Request peer sets address as
89 association primary.
90
91 SCTP_PARAM_ADD_IP - These are used when Dynamic Address
92 SCTP_PARAM_SET_PRIMARY - Reconfiguration is enabled as explained below.
93
94
95 To support Dynamic Address Reconfiguration the following parameters must be
96 enabled on both endpoints (or use the appropriate **setsockopt**\(2))::
97
98 /proc/sys/net/sctp/addip_enable
99 /proc/sys/net/sctp/addip_noauth_enable
100
101 then the following *_PARAM_*'s are sent to the peer in an
102 ASCONF chunk when the corresponding ``@optname``'s are present::
103
104 @optname ASCONF Parameter
105 ---------- ------------------
106 SCTP_SOCKOPT_BINDX_ADD -> SCTP_PARAM_ADD_IP
107 SCTP_SET_PEER_PRIMARY_ADDR -> SCTP_PARAM_SET_PRIMARY
108
109
110 security_sctp_sk_clone()
111 ~~~~~~~~~~~~~~~~~~~~~~~~
112 Called whenever a new socket is created by **accept**\(2)
113 (i.e. a TCP style socket) or when a socket is 'peeled off' e.g userspace
114 calls **sctp_peeloff**\(3).
115 ::
116
117 @asoc - pointer to current sctp association structure.
118 @sk - pointer to current sock structure.
119 @newsk - pointer to new sock structure.
120
121
122 security_sctp_assoc_established()
123 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
124 Called when a COOKIE ACK is received, and the peer secid will be
125 saved into ``@asoc->peer_secid`` for client::
126
127 @asoc - pointer to sctp association structure.
128 @skb - pointer to skbuff of the COOKIE ACK packet.
129
130
131 Security Hooks used for Association Establishment
132 -------------------------------------------------
133
134 The following diagram shows the use of ``security_sctp_bind_connect()``,
135 ``security_sctp_assoc_request()``, ``security_sctp_assoc_established()`` when
136 establishing an association.
137 ::
138
139 SCTP endpoint "A" SCTP endpoint "Z"
140 ================= =================
141 sctp_sf_do_prm_asoc()
142 Association setup can be initiated
143 by a connect(2), sctp_connectx(3),
144 sendmsg(2) or sctp_sendmsg(3).
145 These will result in a call to
146 security_sctp_bind_connect() to
147 initiate an association to
148 SCTP peer endpoint "Z".
149 INIT --------------------------------------------->
150 sctp_sf_do_5_1B_init()
151 Respond to an INIT chunk.
152 SCTP peer endpoint "A" is asking
153 for a temporary association.
154 Call security_sctp_assoc_request()
155 to set the peer label if first
156 association.
157 If not first association, check
158 whether allowed, IF so send:
159 <----------------------------------------------- INIT ACK
160 | ELSE audit event and silently
161 | discard the packet.
162 |
163 COOKIE ECHO ------------------------------------------>
164 sctp_sf_do_5_1D_ce()
165 Respond to an COOKIE ECHO chunk.
166 Confirm the cookie and create a
167 permanent association.
168 Call security_sctp_assoc_request() to
169 do the same as for INIT chunk Response.
170 <------------------------------------------- COOKIE ACK
171 | |
172 sctp_sf_do_5_1E_ca |
173 Call security_sctp_assoc_established() |
174 to set the peer label. |
175 | |
176 | If SCTP_SOCKET_TCP or peeled off
177 | socket security_sctp_sk_clone() is
178 | called to clone the new socket.
179 | |
180 ESTABLISHED ESTABLISHED
181 | |
182 ------------------------------------------------------------------
183 | Association Established |
184 ------------------------------------------------------------------
185
186
187 SCTP SELinux Support
188 ====================
189
190 Security Hooks
191 --------------
192
193 The `SCTP LSM Support`_ chapter above describes the following SCTP security
194 hooks with the SELinux specifics expanded below::
195
196 security_sctp_assoc_request()
197 security_sctp_bind_connect()
198 security_sctp_sk_clone()
199 security_sctp_assoc_established()
200
201
202 security_sctp_assoc_request()
203 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
204 Passes the ``@asoc`` and ``@chunk->skb`` of the association INIT packet to the
205 security module. Returns 0 on success, error on failure.
206 ::
207
208 @asoc - pointer to sctp association structure.
209 @skb - pointer to skbuff of association packet.
210
211 The security module performs the following operations:
212 IF this is the first association on ``@asoc->base.sk``, then set the peer
213 sid to that in ``@skb``. This will ensure there is only one peer sid
214 assigned to ``@asoc->base.sk`` that may support multiple associations.
215
216 ELSE validate the ``@asoc->base.sk peer_sid`` against the ``@skb peer sid``
217 to determine whether the association should be allowed or denied.
218
219 Set the sctp ``@asoc sid`` to socket's sid (from ``asoc->base.sk``) with
220 MLS portion taken from ``@skb peer sid``. This will be used by SCTP
221 TCP style sockets and peeled off connections as they cause a new socket
222 to be generated.
223
224 If IP security options are configured (CIPSO/CALIPSO), then the ip
225 options are set on the socket.
226
227
228 security_sctp_bind_connect()
229 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
230 Checks permissions required for ipv4/ipv6 addresses based on the ``@optname``
231 as follows::
232
233 ------------------------------------------------------------------
234 | BIND Permission Checks |
235 | @optname | @address contains |
236 |----------------------------|-----------------------------------|
237 | SCTP_SOCKOPT_BINDX_ADD | One or more ipv4 / ipv6 addresses |
238 | SCTP_PRIMARY_ADDR | Single ipv4 or ipv6 address |
239 | SCTP_SET_PEER_PRIMARY_ADDR | Single ipv4 or ipv6 address |
240 ------------------------------------------------------------------
241
242 ------------------------------------------------------------------
243 | CONNECT Permission Checks |
244 | @optname | @address contains |
245 |----------------------------|-----------------------------------|
246 | SCTP_SOCKOPT_CONNECTX | One or more ipv4 / ipv6 addresses |
247 | SCTP_PARAM_ADD_IP | One or more ipv4 / ipv6 addresses |
248 | SCTP_SENDMSG_CONNECT | Single ipv4 or ipv6 address |
249 | SCTP_PARAM_SET_PRIMARY | Single ipv4 or ipv6 address |
250 ------------------------------------------------------------------
251
252
253 `SCTP LSM Support`_ gives a summary of the ``@optname``
254 entries and also describes ASCONF chunk processing when Dynamic Address
255 Reconfiguration is enabled.
256
257
258 security_sctp_sk_clone()
259 ~~~~~~~~~~~~~~~~~~~~~~~~
260 Called whenever a new socket is created by **accept**\(2) (i.e. a TCP style
261 socket) or when a socket is 'peeled off' e.g userspace calls
262 **sctp_peeloff**\(3). ``security_sctp_sk_clone()`` will set the new
263 sockets sid and peer sid to that contained in the ``@asoc sid`` and
264 ``@asoc peer sid`` respectively.
265 ::
266
267 @asoc - pointer to current sctp association structure.
268 @sk - pointer to current sock structure.
269 @newsk - pointer to new sock structure.
270
271
272 security_sctp_assoc_established()
273 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
274 Called when a COOKIE ACK is received where it sets the connection's peer sid
275 to that in ``@skb``::
276
277 @asoc - pointer to sctp association structure.
278 @skb - pointer to skbuff of the COOKIE ACK packet.
279
280
281 Policy Statements
282 -----------------
283 The following class and permissions to support SCTP are available within the
284 kernel::
285
286 class sctp_socket inherits socket { node_bind }
287
288 whenever the following policy capability is enabled::
289
290 policycap extended_socket_class;
291
292 SELinux SCTP support adds the ``name_connect`` permission for connecting
293 to a specific port type and the ``association`` permission that is explained
294 in the section below.
295
296 If userspace tools have been updated, SCTP will support the ``portcon``
297 statement as shown in the following example::
298
299 portcon sctp 1024-1036 system_u:object_r:sctp_ports_t:s0
300
301
302 SCTP Peer Labeling
303 ------------------
304 An SCTP socket will only have one peer label assigned to it. This will be
305 assigned during the establishment of the first association. Any further
306 associations on this socket will have their packet peer label compared to
307 the sockets peer label, and only if they are different will the
308 ``association`` permission be validated. This is validated by checking the
309 socket peer sid against the received packets peer sid to determine whether
310 the association should be allowed or denied.
311
312 NOTES:
313 1) If peer labeling is not enabled, then the peer context will always be
314 ``SECINITSID_UNLABELED`` (``unlabeled_t`` in Reference Policy).
315
316 2) As SCTP can support more than one transport address per endpoint
317 (multi-homing) on a single socket, it is possible to configure policy
318 and NetLabel to provide different peer labels for each of these. As the
319 socket peer label is determined by the first associations transport
320 address, it is recommended that all peer labels are consistent.
321
322 3) **getpeercon**\(3) may be used by userspace to retrieve the sockets peer
323 context.
324
325 4) While not SCTP specific, be aware when using NetLabel that if a label
326 is assigned to a specific interface, and that interface 'goes down',
327 then the NetLabel service will remove the entry. Therefore ensure that
328 the network startup scripts call **netlabelctl**\(8) to set the required
329 label (see **netlabel-config**\(8) helper script for details).
330
331 5) The NetLabel SCTP peer labeling rules apply as discussed in the following
332 set of posts tagged "netlabel" at: https://www.paul-moore.com/blog/t.
333
334 6) CIPSO is only supported for IPv4 addressing: ``socket(AF_INET, ...)``
335 CALIPSO is only supported for IPv6 addressing: ``socket(AF_INET6, ...)``
336
337 Note the following when testing CIPSO/CALIPSO:
338 a) CIPSO will send an ICMP packet if an SCTP packet cannot be
339 delivered because of an invalid label.
340 b) CALIPSO does not send an ICMP packet, just silently discards it.
341
342 7) IPSEC is not supported as RFC 3554 - sctp/ipsec support has not been
343 implemented in userspace (**racoon**\(8) or **ipsec_pluto**\(8)),
344 although the kernel supports SCTP/IPSEC.
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