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