[PATCH] netfilter: xt_socket: fix transparent match for IPv6 request sockets

[PATCH] netfilter: xt_socket: fix transparent match for IPv6 request sockets

[KOVACS Krisztian]

The introduction of TCP_NEW_SYN_RECV state, and the addition of request
sockets to the ehash table seems to have broken the --transparent option
of the socket match for IPv6 (around commit a9407000).

Now that the socket lookup finds the TCP_NEW_SYN_RECV socket instead of the
listener, the --transparent option tries to match on the no_srccheck flag
of the request socket.

Unfortunately, that flag was only set for IPv4 sockets in tcp_v4_init_req()
by copying the transparent flag of the listener socket. This effectively
causes '-m socket --transparent' not match on the ACK packet sent by the
client in a TCP handshake.

Based on the suggestion from Eric Dumazet, this change moves the code
initializing no_srccheck to tcp_conn_request(), rendering the above
scenario working again.

Fixes: a940700003 ("netfilter: xt_socket: prepare for TCP_NEW_SYN_RECV support")
Signed-off-by: Alex Badics <alex.badics@balabit.com>
Signed-off-by: KOVACS Krisztian <hidden@balabit.com>
---
 net/ipv4/tcp_input.c | 1 +
 net/ipv4/tcp_ipv4.c  | 1 -
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3ebf45b..1fb2e82 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6260,6 +6260,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 
 	tmp_opt.tstamp_ok = tmp_opt.saw_tstamp;
 	tcp_openreq_init(req, &tmp_opt, skb, sk);
+	inet_rsk(req)->no_srccheck = inet_sk(sk)->transparent;
 
 	/* Note: tcp_v6_init_req() might override ir_iif for link locals */
 	inet_rsk(req)->ir_iif = inet_request_bound_dev_if(sk, skb);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 7158d4f..b448eb9 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1195,7 +1195,6 @@ static void tcp_v4_init_req(struct request_sock *req,
 
 	sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
 	sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
-	ireq->no_srccheck = inet_sk(sk_listener)->transparent;
 	ireq->opt = tcp_v4_save_options(skb);
 }
 
-- 
2.10.0

Re: [PATCH] netfilter: xt_socket: fix transparent match for IPv6 request sockets

[Pablo Neira Ayuso]

On Fri, Sep 23, 2016 at 11:27:42AM +0200, KOVACS Krisztian wrote:
> The introduction of TCP_NEW_SYN_RECV state, and the addition of request
> sockets to the ehash table seems to have broken the --transparent option
> of the socket match for IPv6 (around commit a9407000).
> 
> Now that the socket lookup finds the TCP_NEW_SYN_RECV socket instead of the
> listener, the --transparent option tries to match on the no_srccheck flag
> of the request socket.
> 
> Unfortunately, that flag was only set for IPv4 sockets in tcp_v4_init_req()
> by copying the transparent flag of the listener socket. This effectively
> causes '-m socket --transparent' not match on the ACK packet sent by the
> client in a TCP handshake.
> 
> Based on the suggestion from Eric Dumazet, this change moves the code
> initializing no_srccheck to tcp_conn_request(), rendering the above
> scenario working again.

Applied, thanks Krisztian.

Re: [PATCH] netfilter: xt_socket: fix transparent match for IPv6 request sockets

[Eric Dumazet]

On Tue, 2016-09-20 at 15:26 +0200, KOVACS Krisztian wrote:
> The introduction of TCP_NEW_SYN_RECV state, and the addition of request
> sockets to the ehash table seems to have broken the --transparent option
> of the socket match for IPv6 (around commit a9407000).
> 
> Now that the socket lookup finds the TCP_NEW_SYN_RECV socket instead of the
> listener, the --transparent option tries to match on the no_srccheck flag
> of the request socket.
> 
> Unfortunately, that flag was only set for IPv4 sockets in tcp_v4_init_req()
> by copying the transparent flag of the listener socket. This effectively
> causes '-m socket --transparent' not match on the ACK packet sent by the
> client in a TCP handshake.
> 
> This change adds the same code initializing no_srccheck to
> tcp_v6_init_req(), rendering the above scenario working again.
> 
> Signed-off-by: Alex Badics <alex.badics@balabit.com>
> Signed-off-by: KOVACS Krisztian <hidden@balabit.com>
> ---
>  net/ipv6/tcp_ipv6.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index 94f4f89..21f2e5c 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -690,6 +690,7 @@ static void tcp_v6_init_req(struct request_sock *req,
>  
>  	ireq->ir_v6_rmt_addr = ipv6_hdr(skb)->saddr;
>  	ireq->ir_v6_loc_addr = ipv6_hdr(skb)->daddr;
> +	ireq->no_srccheck = inet_sk(sk_listener)->transparent;
>  
>  	/* So that link locals have meaning */
>  	if (!sk_listener->sk_bound_dev_if &&

Thanks a lot for the bug hunting guys.

Could you add the precise tag to help stable backports ?

Fixes: 12-digit-sha1 ("patch title")

Since it is a netdev patch, I would also copy netdev@ (done here)

Also what about moving this (IPv4/IPv6 common code) before the
af_ops->init_req(req, sk, skb); call, since it is no longer family
specific ?

Something like :

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3ebf45b38bc3..0fccfd6cc258 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6264,6 +6264,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 	/* Note: tcp_v6_init_req() might override ir_iif for link locals */
 	inet_rsk(req)->ir_iif = inet_request_bound_dev_if(sk, skb);
 
+	ireq->no_srccheck = inet_sk(sk)->transparent;
 	af_ops->init_req(req, sk, skb);
 
 	if (security_inet_conn_request(sk, skb, req))
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 7158d4f8dae4..b448eb9fe1b9 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1195,7 +1195,6 @@ static void tcp_v4_init_req(struct request_sock *req,
 
 	sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
 	sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
-	ireq->no_srccheck = inet_sk(sk_listener)->transparent;
 	ireq->opt = tcp_v4_save_options(skb);
 }
 

Re: [PATCH] netfilter: xt_socket: fix transparent match for IPv6 request sockets

[Eric Dumazet]

On Tue, 2016-09-20 at 08:01 -0700, Eric Dumazet wrote:

> 
> Something like :
> 
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index 3ebf45b38bc3..0fccfd6cc258 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -6264,6 +6264,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
>  	/* Note: tcp_v6_init_req() might override ir_iif for link locals */
>  	inet_rsk(req)->ir_iif = inet_request_bound_dev_if(sk, skb);
>  
> +	ireq->no_srccheck = inet_sk(sk)->transparent;

Since there is no @ireq there, simply use :

	inet_rsk(req)->no_srccheck = inet_sk(sk)->transparent;


>  	af_ops->init_req(req, sk, skb);
>