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

From: Richard Haines <[email-masked]>
Date: Fri, 20 Oct 2017 13:04:55 +0100

On Fri, 2017-10-20 at 07:16 -0400, Neil Horman wrote:
> On Wed, Oct 18, 2017 at 11:05:09PM +0800, Xin Long wrote:
> > On Tue, Oct 17, 2017 at 9:58 PM, Richard Haines
> > <[email-masked]> wrote:
> > > Add security hooks to allow security modules to exercise access
> > > control
> > > over SCTP.
> > > 
> > > Signed-off-by: Richard Haines <[email-masked]>
> > > ---
> > >  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_PRI
> > > MARY,
> > > +                                              (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

Thanks for the comments. I've just added the hook as requested for my
next update, however I have not managed to trigger these areas using
the lksctp-tools tests. Can you suggest any suitable tools for testing
these scenarios.

Thanks
Richard
> 
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