net: Find dst with sk's xfrm policy not ctl_sk

commit e22aa14866684f77b4f6b6cae98539e520ddb731 upstream.

If we set XFRM security policy by calling setsockopt with option
IPV6_XFRM_POLICY, the policy will be stored in 'sock_policy' in 'sock'
struct. However tcp_v6_send_response doesn't look up dst_entry with the
actual socket but looks up with tcp control socket. This may cause a
problem that a RST packet is sent without ESP encryption & peer's TCP
socket can't receive it.
This patch will make the function look up dest_entry with actual socket,
if the socket has XFRM policy(sock_policy), so that the TCP response
packet via this function can be encrypted, & aligned on the encrypted
TCP socket.

Tested: We encountered this problem when a TCP socket which is encrypted
in ESP transport mode encryption, receives challenge ACK at SYN_SENT
state. After receiving challenge ACK, TCP needs to send RST to
establish the socket at next SYN try. But the RST was not encrypted &
peer TCP socket still remains on ESTABLISHED state.
So we verified this with test step as below.
[Test step]
1. Making a TCP state mismatch between client(IDLE) & server(ESTABLISHED).
2. Client tries a new connection on the same TCP ports(src & dst).
3. Server will return challenge ACK instead of SYN,ACK.
4. Client will send RST to server to clear the SOCKET.
5. Client will retransmit SYN to server on the same TCP ports.
[Expected result]
The TCP connection should be established.

Cc: Maciej Żenczykowski <maze@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Sehee Lee <seheele@google.com>
Signed-off-by: Sewook Seo <sewookseo@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 65242172e41c2f18c6c2976b188740902998d32c..73030094c6e6f2e94bc43cb73690cafe7aada1d8 100644 (file)
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -1190,6 +1190,8 @@ int __xfrm_sk_clone_policy(struct sock *sk, const struct sock *osk);
 
 static inline int xfrm_sk_clone_policy(struct sock *sk, const struct sock *osk)
 {
+       if (!sk_fullsock(osk))
+               return 0;
        sk->sk_policy[0] = NULL;
        sk->sk_policy[1] = NULL;
        if (unlikely(osk->sk_policy[0] || osk->sk_policy[1]))

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 7aff0179b3c2d0b5d695d70452de00057128c1da..ef786c6232df721aef30e86fffce68da6c7c4ede 100644 (file)
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1704,7 +1704,7 @@ void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
                           tcp_hdr(skb)->source, tcp_hdr(skb)->dest,
                           arg->uid);
        security_skb_classify_flow(skb, flowi4_to_flowi_common(&fl4));
-       rt = ip_route_output_key(net, &fl4);
+       rt = ip_route_output_flow(net, &fl4, sk);
        if (IS_ERR(rt))
                return;
 

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index dae0776c49487609ecd582be4bc0cd0d9d339856..88a45d5650da452696c190226daf907da6e4b4f2 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -817,6 +817,7 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
                ctl_sk->sk_priority = (sk->sk_state == TCP_TIME_WAIT) ?
                                   inet_twsk(sk)->tw_priority : sk->sk_priority;
                transmit_time = tcp_transmit_time(sk);
+               xfrm_sk_clone_policy(ctl_sk, sk);
        }
        ip_send_unicast_reply(ctl_sk,
                              skb, &TCP_SKB_CB(skb)->header.h4.opt,
@@ -825,6 +826,7 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
                              transmit_time);
 
        ctl_sk->sk_mark = 0;
+       xfrm_sk_free_policy(ctl_sk);
        sock_net_set(ctl_sk, &init_net);
        __TCP_INC_STATS(net, TCP_MIB_OUTSEGS);
        __TCP_INC_STATS(net, TCP_MIB_OUTRSTS);

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 8ab39cf57d435f27e45a7060951da64f23976b1d..66d00368db828140d94ef61a82da4dc2d1c03908 100644 (file)
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1001,7 +1001,10 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
         * Underlying function will use this to retrieve the network
         * namespace
         */
-       dst = ip6_dst_lookup_flow(sock_net(ctl_sk), ctl_sk, &fl6, NULL);
+       if (sk && sk->sk_state != TCP_TIME_WAIT)
+               dst = ip6_dst_lookup_flow(net, sk, &fl6, NULL); /*sk's xfrm_policy can be referred*/
+       else
+               dst = ip6_dst_lookup_flow(net, ctl_sk, &fl6, NULL);
        if (!IS_ERR(dst)) {
                skb_dst_set(buff, dst);
                ip6_xmit(ctl_sk, buff, &fl6, fl6.flowi6_mark, NULL,