linux-kernel - [PATCH v2 12/25] tcp: ipv6: Add AO signing for tcp_v6_send

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Date:   Mon,  1 Nov 2021 18:34:47 +0200
From:   Leonard Crestez <cdleonard@...il.com>
To:     David Ahern <dsahern@...nel.org>, Shuah Khan <shuah@...nel.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Yuchung Cheng <ycheng@...gle.com>,
        Francesco Ruggeri <fruggeri@...sta.com>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Christoph Paasch <cpaasch@...le.com>,
        Ivan Delalande <colona@...sta.com>,
        Priyaranjan Jha <priyarjha@...gle.com>, netdev@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 12/25] tcp: ipv6: Add AO signing for tcp_v6_send_response

This is a special code path for acks and resets outside of normal
connection establishment and closing.

Signed-off-by: Leonard Crestez <cdleonard@...il.com>
---
 net/ipv4/tcp_authopt.c |  2 ++
 net/ipv6/tcp_ipv6.c    | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c
index a48b741c83e4..c9d201d8f7a7 100644
--- a/net/ipv4/tcp_authopt.c
+++ b/net/ipv4/tcp_authopt.c
@@ -296,10 +296,11 @@ struct tcp_authopt_key_info *__tcp_authopt_select_key(const struct sock *sk,
 						      const struct sock *addr_sk,
 						      u8 *rnextkeyid)
 {
 	return tcp_authopt_lookup_send(info, addr_sk, -1);
 }
+EXPORT_SYMBOL(__tcp_authopt_select_key);
 
 static struct tcp_authopt_info *__tcp_authopt_info_get_or_create(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct tcp_authopt_info *info;
@@ -1202,10 +1203,11 @@ int tcp_authopt_hash(char *hash_location,
 	 * try to make it obvious inside the packet.
 	 */
 	memset(hash_location, 0, TCP_AUTHOPT_MACLEN);
 	return err;
 }
+EXPORT_SYMBOL(tcp_authopt_hash);
 
 static struct tcp_authopt_key_info *tcp_authopt_lookup_recv(struct sock *sk,
 							    struct sk_buff *skb,
 							    struct tcp_authopt_info *info,
 							    int recv_id)
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 96a29caf56c7..68f9545e4347 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -902,13 +902,37 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
 	struct sock *ctl_sk = net->ipv6.tcp_sk;
 	unsigned int tot_len = sizeof(struct tcphdr);
 	__be32 mrst = 0, *topt;
 	struct dst_entry *dst;
 	__u32 mark = 0;
+#ifdef CONFIG_TCP_AUTHOPT
+	struct tcp_authopt_info *authopt_info = NULL;
+	struct tcp_authopt_key_info *authopt_key_info = NULL;
+	u8 authopt_rnextkeyid;
+#endif
 
 	if (tsecr)
 		tot_len += TCPOLEN_TSTAMP_ALIGNED;
+#ifdef CONFIG_TCP_AUTHOPT
+	/* Key lookup before SKB allocation */
+	if (static_branch_unlikely(&tcp_authopt_needed) && sk) {
+		if (sk->sk_state == TCP_TIME_WAIT)
+			authopt_info = tcp_twsk(sk)->tw_authopt_info;
+		else
+			authopt_info = rcu_dereference(tcp_sk(sk)->authopt_info);
+
+		if (authopt_info) {
+			authopt_key_info = __tcp_authopt_select_key(sk, authopt_info, sk,
+								    &authopt_rnextkeyid);
+			if (authopt_key_info) {
+				tot_len += TCPOLEN_AUTHOPT_OUTPUT;
+				/* Don't use MD5 */
+				key = NULL;
+			}
+		}
+	}
+#endif
 #ifdef CONFIG_TCP_MD5SIG
 	if (key)
 		tot_len += TCPOLEN_MD5SIG_ALIGNED;
 #endif
 
@@ -961,10 +985,24 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
 		tcp_v6_md5_hash_hdr((__u8 *)topt, key,
 				    &ipv6_hdr(skb)->saddr,
 				    &ipv6_hdr(skb)->daddr, t1);
 	}
 #endif
+#ifdef CONFIG_TCP_AUTHOPT
+	/* Compute the TCP-AO mac. Unlike in the ipv4 case we have a real SKB */
+	if (static_branch_unlikely(&tcp_authopt_needed) && authopt_key_info) {
+		*topt++ = htonl((TCPOPT_AUTHOPT << 24) |
+				(TCPOLEN_AUTHOPT_OUTPUT << 16) |
+				(authopt_key_info->send_id << 8) |
+				(authopt_rnextkeyid));
+		tcp_authopt_hash((char *)topt,
+				 authopt_key_info,
+				 authopt_info,
+				 (struct sock *)sk,
+				 buff);
+	}
+#endif
 
 	memset(&fl6, 0, sizeof(fl6));
 	fl6.daddr = ipv6_hdr(skb)->saddr;
 	fl6.saddr = ipv6_hdr(skb)->daddr;
 	fl6.flowlabel = label;
-- 
2.25.1