netdev - Re: [PATCH V4 4/4] selinux: Add SCTP support

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Message-ID: <CAHC9VhR9AkU4nF8VjCiGERtTU5OEtSUQFcDDhJeyJe2gzM=1gQ@mail.gmail.com>
Date:   Wed, 10 Jan 2018 11:37:50 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     Richard Haines <richard_c_haines@...nternet.com>
Cc:     selinux@...ho.nsa.gov, netdev@...r.kernel.org,
        linux-sctp@...r.kernel.org, linux-security-module@...r.kernel.org,
        Vlad Yasevich <vyasevich@...il.com>, nhorman@...driver.com,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Eric Paris <eparis@...isplace.org>, marcelo.leitner@...il.com,
        casey@...aufler-ca.com
Subject: Re: [PATCH V4 4/4] selinux: Add SCTP support

On Sat, Dec 30, 2017 at 12:20 PM, Richard Haines
<richard_c_haines@...nternet.com> wrote:
> The SELinux SCTP implementation is explained in:
> Documentation/security/SELinux-sctp.rst
>
> Signed-off-by: Richard Haines <richard_c_haines@...nternet.com>
> ---
>  Documentation/security/SELinux-sctp.rst | 157 ++++++++++++++++++
>  security/selinux/hooks.c                | 280 +++++++++++++++++++++++++++++---
>  security/selinux/include/classmap.h     |   2 +-
>  security/selinux/include/netlabel.h     |  21 ++-
>  security/selinux/include/objsec.h       |   4 +
>  security/selinux/netlabel.c             | 138 ++++++++++++++--
>  6 files changed, 570 insertions(+), 32 deletions(-)
>  create mode 100644 Documentation/security/SELinux-sctp.rst

...

> +/**
> + * selinux_netlbl_socket_connect - Label a client-side socket on connect
> + * @sk: the socket to label
> + * @addr: the destination address
> + *
> + * Description:
> + * Attempt to label a connected socket with NetLabel using the given address.
> + * Returns zero values on success, negative values on failure.
> + *
> + */
> +int selinux_netlbl_socket_connect(struct sock *sk, struct sockaddr *addr)
> +{
> +       int rc;
> +       struct sk_security_struct *sksec = sk->sk_security;
> +
> +       if (sksec->nlbl_state != NLBL_REQSKB &&
> +           sksec->nlbl_state != NLBL_CONNLABELED)
> +               return 0;
> +
> +       lock_sock(sk);
> +       rc = selinux_netlbl_socket_connect_helper(sk, addr);
>         release_sock(sk);
> +
>         return rc;
>  }
> +
> +/**
> + * selinux_netlbl_socket_connect_locked - Label a client-side socket on
> + * connect
> + * @sk: the socket to label
> + * @addr: the destination address
> + *
> + * Description:
> + * Attempt to label a connected socket that already has the socket locked
> + * with NetLabel using the given address.
> + * Returns zero values on success, negative values on failure.
> + *
> + */
> +int selinux_netlbl_socket_connect_locked(struct sock *sk,
> +                                        struct sockaddr *addr)
> +{
> +       struct sk_security_struct *sksec = sk->sk_security;
> +
> +       if (sksec->nlbl_state != NLBL_REQSKB &&
> +           sksec->nlbl_state != NLBL_CONNLABELED)
> +               return 0;
> +
> +       return selinux_netlbl_socket_connect_helper(sk, addr);
> +}

[Sorry for the review delay, the holidays and some associated travel
made it hard to find some quiet time to look at the latest patches.]

I probably should have been a bit more clear in my last comment, but
what I had in mind was something like the following:

int selinux_netlbl_socket_connect_locked(...)
{
    if (sksec->nlbl_state ...)
        return 0;

    return selinux_netlbl_socket_connect_helper();
}

int selinux_netlbl_socket_connect(...)
{
    int rc;

    lock_sock();
    rc = selinux_netlbl_socket_connect_locked();
    release_sock();

    return rc;
}

Yes, you do end up checking nlbl_state while the socket lock is held,
but I believe the benefit of consolidating the code outweighs any
additional overhead (I believe it would be "noise" anyway).

Otherwise, this all looks good to me.

-- 
paul moore
www.paul-moore.com