[RFC PATCH 1/5] security: Add support for SCTP security hooks
Richard Haines
richard_c_haines at btinternet.com
Tue Oct 17 14:02:47 UTC 2017
The SCTP security hooks are explained in:
Documentation/security/LSM-sctp.txt
Signed-off-by: Richard Haines <richard_c_haines at btinternet.com>
---
Documentation/security/LSM-sctp.txt | 212 ++++++++++++++++++++++++++++++++++++
include/linux/lsm_hooks.h | 37 +++++++
include/linux/security.h | 27 +++++
security/security.c | 23 ++++
4 files changed, 299 insertions(+)
create mode 100644 Documentation/security/LSM-sctp.txt
diff --git a/Documentation/security/LSM-sctp.txt b/Documentation/security/LSM-sctp.txt
new file mode 100644
index 0000000..30fe9b5
--- /dev/null
+++ b/Documentation/security/LSM-sctp.txt
@@ -0,0 +1,212 @@
+ 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.txt
+
+
+security_sctp_assoc_request()
+------------------------------
+This new hook has been added to net/sctp/sm_statefuns.c where it passes the
+ at ep and @chunk->skb (the association INIT or INIT ACK 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.
+ @sctp_cid - set to sctp packet type (SCTP_CID_INIT or SCTP_CID_INIT_ACK).
+
+The security module performs the following operations:
+ 1) 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.
+
+ 2) If not the first association, validate the @ep->base.sk peer_sid against
+ the @skb peer sid to determine whether the association should be allowed
+ or denied.
+
+ 3) If @sctp_cid = SCTP_CID_INIT, then set the sctp @ep sid to socket's sid
+ (from ep->base.sk) with MLS portion taken from @skb peer sid. This will
+ only 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.
+
+ To support this hook include/net/sctp/structs.h "struct sctp_endpoint"
+ has been updated with the following:
+
+ /* Security identifiers from incoming (INIT). These are set by
+ * security_sctp_assoc_request(). These will only be used by
+ * SCTP TCP type sockets and peeled off connections as they
+ * cause a new socket to be generated. security_sctp_sk_clone()
+ * will then plug these into the new socket.
+ */
+ u32 secid;
+ u32 peer_secid;
+
+
+security_sctp_bind_connect()
+-----------------------------
+This new hook has been added to net/sctp/socket.c and net/sctp/sm_make_chunk.c.
+It 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 setsockopts):
+ /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()
+-------------------------
+This new hook has been added to net/sctp/socket.c sctp_sock_migrate() that is
+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 old sctp endpoint structure.
+ @sk - pointer to old sock structure.
+ @sk - pointer to new sock structure.
+
+security_inet_conn_established()
+---------------------------------
+This hook has been added to net/sctp/sm_statefuns.c COOKIE ECHO processing
+where it sets the connection's peer sid to that in @skb.
+
+ @sk - pointer to sock structure.
+ @skb - pointer to skbuff of the COOKIE ECHO packet.
+
+
+Security Hooks used for Association Establishment
+==================================================
+The following diagram shows the use of security_sctp_connect_bind(),
+security_sctp_assoc_request(), security_inet_conn_established() in
+net/sctp/sm_statefuns.c and security_sctp_sk_clone() in net/sctp/socket.c,
+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.
+ sctp_sf_do_5_1C_ack
+ Respond to an INIT ACK chunk.
+ SCTP peer endpoint"A" initiated
+ this association to SCTP peer
+ endpoint "Z". Call
+ security_sctp_assoc_request()
+ to set the peer label if first
+ association. If not first
+ association, check whether
+ allowed, IF so send:
+ COOKIE ECHO ------------------------------------------>
+ ELSE audit event and silently |
+ discard the packet. |
+ |
+ <------------------------------------------- COOKIE ACK
+ | |
+ sctp_sf_do_5_1E_ca |
+ Call security_inet_conn_established() |
+ to set the correct peer sid. |
+ | |
+ | net/sctp/socket.c sctp_copy_sock()
+ | If SCTP_SOCKET_TCP or peeled off
+ | socket security_sctp_sk_clone() is
+ | called to clone the new socket.
+ | |
+ ESTABLISHED ESTABLISHED
+ | |
+ ------------------------------------------------------------------
+ | Association Established |
+ ------------------------------------------------------------------
+
+
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 3a90feb..42370a7 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -913,6 +913,33 @@
* associated with the TUN device's security structure.
* @security pointer to the TUN devices's security structure.
*
+ * Security hooks for SCTP
+ *
+ * @sctp_assoc_request:
+ * If first association, then set the peer sid to that in @skb. If
+ * @sctp_cid is from an INIT chunk, then set the sctp endpoint sid to
+ * socket's sid (ep->base.sk) with MLS portion taken from peer sid.
+ * @ep pointer to sctp endpoint structure.
+ * @skb pointer to skbuff of association packet.
+ * @sctp_cid whether association from INIT or INIT_ACK chunk.
+ * Return 0 on success, error on failure.
+ * @sctp_bind_connect:
+ * Validiate permissions required for each address associated with sock
+ * @sk. Depending on @optname, the addresses will be treated as either
+ * for a connect or bind service. The @addrlen is calculated on each
+ * ipv4 and ipv6 address using sizeof(struct sockaddr_in) or
+ * sizeof(struct sockaddr_in6).
+ * @sk pointer to sock structure.
+ * @optname name of the option to validate.
+ * @address list containing one or more ipv4/ipv6 addresses.
+ * @addrlen total length of address(s).
+ * Return 0 on success, error on failure.
+ * @sctp_sk_clone:
+ * Sets the new child socket's sid to the old endpoint sid.
+ * @ep pointer to old sctp endpoint structure.
+ * @sk pointer to old sock structure.
+ * @sk pointer to new sock structure.
+ *
* Security hooks for Infiniband
*
* @ib_pkey_access:
@@ -1640,6 +1667,13 @@ union security_list_options {
int (*tun_dev_attach_queue)(void *security);
int (*tun_dev_attach)(struct sock *sk, void *security);
int (*tun_dev_open)(void *security);
+ int (*sctp_assoc_request)(struct sctp_endpoint *ep,
+ struct sk_buff *skb,
+ int sctp_cid);
+ int (*sctp_bind_connect)(struct sock *sk, int optname,
+ struct sockaddr *address, int addrlen);
+ void (*sctp_sk_clone)(struct sctp_endpoint *ep, struct sock *sk,
+ struct sock *newsk);
#endif /* CONFIG_SECURITY_NETWORK */
#ifdef CONFIG_SECURITY_INFINIBAND
@@ -1880,6 +1914,9 @@ struct security_hook_heads {
struct list_head tun_dev_attach_queue;
struct list_head tun_dev_attach;
struct list_head tun_dev_open;
+ struct list_head sctp_assoc_request;
+ struct list_head sctp_bind_connect;
+ struct list_head sctp_sk_clone;
#endif /* CONFIG_SECURITY_NETWORK */
#ifdef CONFIG_SECURITY_INFINIBAND
struct list_head ib_pkey_access;
diff --git a/include/linux/security.h b/include/linux/security.h
index 834b355..2054023 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -114,6 +114,7 @@ struct xfrm_policy;
struct xfrm_state;
struct xfrm_user_sec_ctx;
struct seq_file;
+struct sctp_endpoint;
#ifdef CONFIG_MMU
extern unsigned long mmap_min_addr;
@@ -1240,6 +1241,12 @@ int security_tun_dev_create(void);
int security_tun_dev_attach_queue(void *security);
int security_tun_dev_attach(struct sock *sk, void *security);
int security_tun_dev_open(void *security);
+int security_sctp_assoc_request(struct sctp_endpoint *ep, struct sk_buff *skb,
+ int sctp_cid);
+int security_sctp_bind_connect(struct sock *sk, int optname,
+ struct sockaddr *address, int addrlen);
+void security_sctp_sk_clone(struct sctp_endpoint *ep, struct sock *sk,
+ struct sock *newsk);
#else /* CONFIG_SECURITY_NETWORK */
static inline int security_unix_stream_connect(struct sock *sock,
@@ -1432,6 +1439,26 @@ static inline int security_tun_dev_open(void *security)
{
return 0;
}
+
+static inline int security_sctp_assoc_request(struct sctp_endpoint *ep,
+ struct sk_buff *skb,
+ int sctp_cid)
+{
+ return 0;
+}
+
+static inline int security_sctp_bind_connect(struct sock *sk, int optname,
+ struct sockaddr *address,
+ int addrlen)
+{
+ return 0;
+}
+
+static inline void security_sctp_sk_clone(struct sctp_endpoint *ep,
+ struct sock *sk,
+ struct sock *newsk)
+{
+}
#endif /* CONFIG_SECURITY_NETWORK */
#ifdef CONFIG_SECURITY_INFINIBAND
diff --git a/security/security.c b/security/security.c
index 3013237..798fc6e 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1482,6 +1482,7 @@ void security_inet_conn_established(struct sock *sk,
{
call_void_hook(inet_conn_established, sk, skb);
}
+EXPORT_SYMBOL(security_inet_conn_established);
int security_secmark_relabel_packet(u32 secid)
{
@@ -1537,6 +1538,28 @@ int security_tun_dev_open(void *security)
}
EXPORT_SYMBOL(security_tun_dev_open);
+int security_sctp_assoc_request(struct sctp_endpoint *ep, struct sk_buff *skb,
+ int sctp_cid)
+{
+ return call_int_hook(sctp_assoc_request, 0, ep, skb, sctp_cid);
+}
+EXPORT_SYMBOL(security_sctp_assoc_request);
+
+int security_sctp_bind_connect(struct sock *sk, int optname,
+ struct sockaddr *address, int addrlen)
+{
+ return call_int_hook(sctp_bind_connect, 0, sk, optname,
+ address, addrlen);
+}
+EXPORT_SYMBOL(security_sctp_bind_connect);
+
+void security_sctp_sk_clone(struct sctp_endpoint *ep, struct sock *sk,
+ struct sock *newsk)
+{
+ call_void_hook(sctp_sk_clone, ep, sk, newsk);
+}
+EXPORT_SYMBOL(security_sctp_sk_clone);
+
#endif /* CONFIG_SECURITY_NETWORK */
#ifdef CONFIG_SECURITY_INFINIBAND
--
2.13.6
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