Re: [RFC PATCH 3/5] sctp: Add LSM hooks

On Wed, Oct 18, 2017 at 11:05:09PM +0800, Xin Long wrote:

On Tue, Oct 17, 2017 at 9:58 PM, Richard Haines
[off-list ref] wrote:

quoted

Add security hooks to allow security modules to exercise access control
over SCTP.

Signed-off-by: Richard Haines <redacted>
---
 include/net/sctp/structs.h | 10 ++++++++
 include/uapi/linux/sctp.h  |  1 +
 net/sctp/sm_make_chunk.c   | 12 +++++++++
 net/sctp/sm_statefuns.c    | 14 ++++++++++-
 net/sctp/socket.c          | 61 +++++++++++++++++++++++++++++++++++++++++++++-
 5 files changed, 96 insertions(+), 2 deletions(-)

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 7767577..6e72e3e 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h

@@ -1270,6 +1270,16 @@ struct sctp_endpoint {
              reconf_enable:1;

        __u8  strreset_enable;
+
+       /* 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;
 };

 /* Recover the outter endpoint structure. */

diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
index 6217ff8..c04812f 100644
--- a/include/uapi/linux/sctp.h
+++ b/include/uapi/linux/sctp.h

@@ -122,6 +122,7 @@ typedef __s32 sctp_assoc_t;
 #define SCTP_RESET_ASSOC       120
 #define SCTP_ADD_STREAMS       121
 #define SCTP_SOCKOPT_PEELOFF_FLAGS 122
+#define SCTP_SENDMSG_CONNECT   123

 /* PR-SCTP policies */
 #define SCTP_PR_SCTP_NONE      0x0000

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 6110447..ca4705b 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c

@@ -3059,6 +3059,12 @@ static __be16 sctp_process_asconf_param(struct sctp_association *asoc,
                if (af->is_any(&addr))
                        memcpy(&addr, &asconf->source, sizeof(addr));

+               if (security_sctp_bind_connect(asoc->ep->base.sk,
+                                              SCTP_PARAM_ADD_IP,
+                                              (struct sockaddr *)&addr,
+                                              af->sockaddr_len))
+                       return SCTP_ERROR_REQ_REFUSED;
+
                /* ADDIP 4.3 D9) If an endpoint receives an ADD IP address
                 * request and does not have the local resources to add this
                 * new address to the association, it MUST return an Error

@@ -3125,6 +3131,12 @@ static __be16 sctp_process_asconf_param(struct sctp_association *asoc,
                if (af->is_any(&addr))
                        memcpy(&addr.v4, sctp_source(asconf), sizeof(addr));

+               if (security_sctp_bind_connect(asoc->ep->base.sk,
+                                              SCTP_PARAM_SET_PRIMARY,
+                                              (struct sockaddr *)&addr,
+                                              af->sockaddr_len))
+                       return SCTP_ERROR_REQ_REFUSED;
+
                peer = sctp_assoc_lookup_paddr(asoc, &addr);
                if (!peer)
                        return SCTP_ERROR_DNS_FAILED;

diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index b2a74c3..4ba5805 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c

@@ -314,6 +314,11 @@ sctp_disposition_t sctp_sf_do_5_1B_init(struct net *net,
        sctp_unrecognized_param_t *unk_param;
        int len;

+       /* Update socket peer label if first association. */
+       if (security_sctp_assoc_request((struct sctp_endpoint *)ep,
+                                       chunk->skb, SCTP_CID_INIT))
+               return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+
        /* 6.10 Bundling
         * An endpoint MUST NOT bundle INIT, INIT ACK or
         * SHUTDOWN COMPLETE with any other chunks.

@@ -446,7 +451,6 @@ sctp_disposition_t sctp_sf_do_5_1B_init(struct net *net,
        }

        sctp_add_cmd_sf(commands, SCTP_CMD_NEW_ASOC, SCTP_ASOC(new_asoc));
-
        sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));

        /*

@@ -507,6 +511,11 @@ sctp_disposition_t sctp_sf_do_5_1C_ack(struct net *net,
        struct sctp_chunk *err_chunk;
        struct sctp_packet *packet;

+       /* Update socket peer label if first association. */
+       if (security_sctp_assoc_request((struct sctp_endpoint *)ep,
+                                       chunk->skb, SCTP_CID_INIT_ACK))
+               return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+

Just thinking security_sctp_assoc_request hook should also be in
sctp_sf_do_unexpected_init() and sctp_sf_do_5_2_4_dupcook() ?

I agree, i think if this hook is gating on the creation of a new association,
they should be in all the locations where that happens
Neil

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