Subject: Re: [RFC PATCH v9 06/18] LSM: Add inet_sys_snd_skb() LSM hook (fwd)

From: Paul Moore <[email-masked]>
Date: Sat, 22 Dec 2007 09:54:49 -0500

On Friday 21 December 2007 7:51:26 pm James Morris wrote:
> This is part of a large patchset which finally "fixes" labeled networking,
> which we're hoping to get into 2.6.25.
>
> Thread @ http://thread.gmane.org/gmane.linux.kernel.lsm/4894
>
> The patch below is the only one which is not self-contained & impacts on
> core networking code.
>
> If anyone has any objections or comments on this patch, please let us
> know.

Also, for the record, this is the same patch that was posted earlier in the 
week in an attempt to solicit comments.

> ---------- Forwarded message ----------
> Date: Fri, 21 Dec 2007 12:09:28 -0500
> From: Paul Moore <[email-masked]>
> To: [email-masked], [email-masked]
> Cc: [email-masked], [email-masked]
> Subject: [RFC PATCH v9 06/18] LSM: Add inet_sys_snd_skb() LSM hook
>
> Add an inet_sys_snd_skb() LSM hook to allow the LSM to provide packet level
> access control for all outbound packets.  Using the existing postroute_last
> netfilter hook turns out to be problematic as it is can be invoked multiple
> times for a single packet, e.g. individual IPsec transforms, adding
> unwanted overhead and complicating the security policy.
>
> Signed-off-by: Paul Moore <[email-masked]>
> ---
>
>  include/linux/security.h |   11 +++++++++++
>  net/ipv4/ip_output.c     |    7 +++++++
>  net/ipv6/ip6_output.c    |    5 +++++
>  security/dummy.c         |    8 +++++++-
>  security/security.c      |    6 ++++++
>  5 files changed, 36 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/security.h b/include/linux/security.h
> index db19c92..1b8d332 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -876,6 +876,10 @@ struct request_sock;
>   *     Sets the connection's peersid to the secmark on skb.
>   * @req_classify_flow:
>   *	Sets the flow's sid to the openreq sid.
> + * @inet_sys_snd_skb:
> + *	Check permissions on outgoing network packets.
> + *	@skb is the packet to check
> + *	@family is the packet's address family
>   *
>   * Security hooks for XFRM operations.
>   *
> @@ -1416,6 +1420,7 @@ struct security_operations {
>  	void (*inet_csk_clone)(struct sock *newsk, const struct request_sock
> *req); void (*inet_conn_established)(struct sock *sk, struct sk_buff *skb);
> void (*req_classify_flow)(const struct request_sock *req, struct flowi
> *fl); +	int (*inet_sys_snd_skb)(struct sk_buff *skb, int family);
>  #endif	/* CONFIG_SECURITY_NETWORK */
>
>  #ifdef CONFIG_SECURITY_NETWORK_XFRM
> @@ -2328,6 +2333,7 @@ void security_sk_free(struct sock *sk);
>  void security_sk_clone(const struct sock *sk, struct sock *newsk);
>  void security_sk_classify_flow(struct sock *sk, struct flowi *fl);
>  void security_req_classify_flow(const struct request_sock *req, struct
> flowi *fl); +int security_inet_sys_snd_skb(struct sk_buff *skb, int
> family);
>  void security_sock_graft(struct sock*sk, struct socket *parent);
>  int security_inet_conn_request(struct sock *sk,
>  			struct sk_buff *skb, struct request_sock *req);
> @@ -2471,6 +2477,11 @@ static inline void security_req_classify_flow(const
> struct request_sock *req, st {
>  }
>
> +static inline int security_inet_sys_snd_skb(struct sk_buff *skb, int
> family) +{
> +	return 0;
> +}
> +
>  static inline void security_sock_graft(struct sock* sk, struct socket
> *parent) {
>  }
> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
> index fd99fbd..82a7297 100644
> --- a/net/ipv4/ip_output.c
> +++ b/net/ipv4/ip_output.c
> @@ -204,6 +204,8 @@ static inline int ip_skb_dst_mtu(struct sk_buff *skb)
>
>  static int ip_finish_output(struct sk_buff *skb)
>  {
> +	int err;
> +
>  #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
>  	/* Policy lookup after SNAT yielded a new policy */
>  	if (skb->dst->xfrm != NULL) {
> @@ -211,6 +213,11 @@ static int ip_finish_output(struct sk_buff *skb)
>  		return dst_output(skb);
>  	}
>  #endif
> +
> +	err = security_inet_sys_snd_skb(skb, AF_INET);
> +	if (err)
> +		return err;
> +
>  	if (skb->len > ip_skb_dst_mtu(skb) && !skb_is_gso(skb))
>  		return ip_fragment(skb, ip_finish_output2);
>  	else
> diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
> index 6338a9c..44ddf32 100644
> --- a/net/ipv6/ip6_output.c
> +++ b/net/ipv6/ip6_output.c
> @@ -72,8 +72,13 @@ static __inline__ void ipv6_select_ident(struct sk_buff
> *skb, struct frag_hdr *f
>
>  static int ip6_output_finish(struct sk_buff *skb)
>  {
> +	int err;
>  	struct dst_entry *dst = skb->dst;
>
> +	err = security_inet_sys_snd_skb(skb, AF_INET6);
> +	if (err)
> +		return err;
> +
>  	if (dst->hh)
>  		return neigh_hh_output(dst->hh, skb);
>  	else if (dst->neighbour)
> diff --git a/security/dummy.c b/security/dummy.c
> index 0b62f95..384979a 100644
> --- a/security/dummy.c
> +++ b/security/dummy.c
> @@ -848,6 +848,11 @@ static inline void dummy_req_classify_flow(const
> struct request_sock *req, struct flowi *fl)
>  {
>  }
> +
> +static inline int dummy_inet_sys_snd_skb(struct sk_buff *skb, int family)
> +{
> +	return 0;
> +}
>  #endif	/* CONFIG_SECURITY_NETWORK */
>
>  #ifdef CONFIG_SECURITY_NETWORK_XFRM
> @@ -1122,7 +1127,8 @@ void security_fixup_ops (struct security_operations
> *ops) set_to_dummy_if_null(ops, inet_csk_clone);
>  	set_to_dummy_if_null(ops, inet_conn_established);
>  	set_to_dummy_if_null(ops, req_classify_flow);
> - #endif	/* CONFIG_SECURITY_NETWORK */
> +	set_to_dummy_if_null(ops, inet_sys_snd_skb);
> +#endif	/* CONFIG_SECURITY_NETWORK */
>  #ifdef  CONFIG_SECURITY_NETWORK_XFRM
>  	set_to_dummy_if_null(ops, xfrm_policy_alloc_security);
>  	set_to_dummy_if_null(ops, xfrm_policy_clone_security);
> diff --git a/security/security.c b/security/security.c
> index 3bdcada..7f55459 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -961,6 +961,12 @@ void security_req_classify_flow(const struct
> request_sock *req, struct flowi *fl }
>  EXPORT_SYMBOL(security_req_classify_flow);
>
> +int security_inet_sys_snd_skb(struct sk_buff *skb, int family)
> +{
> +	return security_ops->inet_sys_snd_skb(skb, family);
> +}
> +EXPORT_SYMBOL(security_inet_sys_snd_skb);
> +
>  void security_sock_graft(struct sock *sk, struct socket *parent)
>  {
>  	security_ops->sock_graft(sk, parent);
>
> -
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-- 
paul moore
linux security @ hp