[PATCH net v3 2/2] security: implement sctp_assoc_established hook in selinux

[Paul Moore]

On Sat, Feb 12, 2022 at 12:59 PM Ondrej Mosnacek <omosnace at redhat.com> wrote:
>
> Do this by extracting the peer labeling per-association logic from
> selinux_sctp_assoc_request() into a new helper
> selinux_sctp_process_new_assoc() and use this helper in both
> selinux_sctp_assoc_request() and selinux_sctp_assoc_established(). This
> ensures that the peer labeling behavior as documented in
> Documentation/security/SCTP.rst is applied both on the client and server
> side:
> """
> An SCTP socket will only have one peer label assigned to it. This will be
> assigned during the establishment of the first association. Any further
> associations on this socket will have their packet peer label compared to
> the sockets peer label, and only if they are different will the
> ``association`` permission be validated. This is validated by checking the
> socket peer sid against the received packets peer sid to determine whether
> the association should be allowed or denied.
> """
>
> At the same time, it also ensures that the peer label of the association
> is set to the correct value, such that if it is peeled off into a new
> socket, the socket's peer label  will then be set to the association's
> peer label, same as it already works on the server side.
>
> While selinux_inet_conn_established() (which we are replacing by
> selinux_sctp_assoc_established() for SCTP) only deals with assigning a
> peer label to the connection (socket), in case of SCTP we need to also
> copy the (local) socket label to the association, so that
> selinux_sctp_sk_clone() can then pick it up for the new socket in case
> of SCTP peeloff.
>
> Careful readers will notice that the selinux_sctp_process_new_assoc()
> helper also includes the "IPv4 packet received over an IPv6 socket"
> check, even though it hadn't been in selinux_sctp_assoc_request()
> before. While such check is not necessary in
> selinux_inet_conn_request() (because struct request_sock's family field
> is already set according to the skb's family), here it is needed, as we
> don't have request_sock and we take the initial family from the socket.
> In selinux_sctp_assoc_established() it is similarly needed as well (and
> also selinux_inet_conn_established() already has it).
>
> Fixes: 72e89f50084c ("security: Add support for SCTP security hooks")
> Reported-by: Prashanth Prahlad <pprahlad at redhat.com>
> Based-on-patch-by: Xin Long <lucien.xin at gmail.com>
> Signed-off-by: Ondrej Mosnacek <omosnace at redhat.com>
> ---
>  security/selinux/hooks.c | 90 +++++++++++++++++++++++++++++-----------
>  1 file changed, 66 insertions(+), 24 deletions(-)

This patch, and patch 1/2, look good to me; I'm assuming this resolves
all of the known SELinux/SCTP problems identified before the new year?

If I can get an ACK from one of the SCTP and/or netdev folks I'll
merge this into the selinux/next branch.

-- 
paul-moore.com