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diff --git a/Documentation/security/LSM-sctp.rst b/Documentation/security/LSM-sctp.rst new file mode 100644 index 000000000000..6e5a3925a860 --- /dev/null +++ b/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 | + ------------------------------------------------------------------ + + |