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