[v3,net] tcp: randomize timestamps on syncookies

diff --git a/include/net/secure_seq.h b/include/net/secure_seq.h
index fe236b3429f0d8caeb1adc367b5b4a20591c848b..b94006f6fbdde0d78fe33b9c2d86159e291c30cf 100644
--- a/include/net/secure_seq.h
+++ b/include/net/secure_seq.h
@@ -6,10 +6,12 @@ 
 u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport);
 u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
 			       __be16 dport);
-u32 secure_tcp_seq_and_tsoff(__be32 saddr, __be32 daddr,
-			     __be16 sport, __be16 dport, u32 *tsoff);
-u32 secure_tcpv6_seq_and_tsoff(const __be32 *saddr, const __be32 *daddr,
-			       __be16 sport, __be16 dport, u32 *tsoff);
+u32 secure_tcp_seq(__be32 saddr, __be32 daddr,
+		   __be16 sport, __be16 dport);
+u32 secure_tcp_ts_off(__be32 saddr, __be32 daddr);
+u32 secure_tcpv6_seq(const __be32 *saddr, const __be32 *daddr,
+		     __be16 sport, __be16 dport);
+u32 secure_tcpv6_ts_off(const __be32 *saddr, const __be32 *daddr);
 u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
 				__be16 sport, __be16 dport);
 u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 270e5cc43c99e7030e95af218095cf9f283950bc..8c0e5a901d6424fbd01233cd3adfdce52076f7a9 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -470,7 +470,7 @@  void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
 /* From syncookies.c */
 struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
 				 struct request_sock *req,
-				 struct dst_entry *dst);
+				 struct dst_entry *dst, u32 tsoff);
 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
 		      u32 cookie);
 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
@@ -1822,7 +1822,8 @@  struct tcp_request_sock_ops {
 #endif
 	struct dst_entry *(*route_req)(const struct sock *sk, struct flowi *fl,
 				       const struct request_sock *req);
-	__u32 (*init_seq_tsoff)(const struct sk_buff *skb, u32 *tsoff);
+	u32 (*init_seq)(const struct sk_buff *skb);
+	u32 (*init_ts_off)(const struct sk_buff *skb);
 	int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
 			   struct flowi *fl, struct request_sock *req,
 			   struct tcp_fastopen_cookie *foc,
diff --git a/net/core/secure_seq.c b/net/core/secure_seq.c
index 6bd2f8fb0476baabf507557fc0d06b6787511c70..ae35cce3a40d70387bee815798933aa43a0e6d84 100644
--- a/net/core/secure_seq.c
+++ b/net/core/secure_seq.c
@@ -24,9 +24,13 @@  static siphash_key_t ts_secret __read_mostly;
 
 static __always_inline void net_secret_init(void)
 {
-	net_get_random_once(&ts_secret, sizeof(ts_secret));
 	net_get_random_once(&net_secret, sizeof(net_secret));
 }
+
+static __always_inline void ts_secret_init(void)
+{
+	net_get_random_once(&ts_secret, sizeof(ts_secret));
+}
 #endif
 
 #ifdef CONFIG_INET
@@ -47,7 +51,7 @@  static u32 seq_scale(u32 seq)
 #endif
 
 #if IS_ENABLED(CONFIG_IPV6)
-static u32 secure_tcpv6_ts_off(const __be32 *saddr, const __be32 *daddr)
+u32 secure_tcpv6_ts_off(const __be32 *saddr, const __be32 *daddr)
 {
 	const struct {
 		struct in6_addr saddr;
@@ -60,12 +64,14 @@  static u32 secure_tcpv6_ts_off(const __be32 *saddr, const __be32 *daddr)
 	if (sysctl_tcp_timestamps != 1)
 		return 0;
 
+	ts_secret_init();
 	return siphash(&combined, offsetofend(typeof(combined), daddr),
 		       &ts_secret);
 }
+EXPORT_SYMBOL(secure_tcpv6_ts_off);
 
-u32 secure_tcpv6_seq_and_tsoff(const __be32 *saddr, const __be32 *daddr,
-			       __be16 sport, __be16 dport, u32 *tsoff)
+u32 secure_tcpv6_seq(const __be32 *saddr, const __be32 *daddr,
+		     __be16 sport, __be16 dport)
 {
 	const struct {
 		struct in6_addr saddr;
@@ -78,14 +84,14 @@  u32 secure_tcpv6_seq_and_tsoff(const __be32 *saddr, const __be32 *daddr,
 		.sport = sport,
 		.dport = dport
 	};
-	u64 hash;
+	u32 hash;
+
 	net_secret_init();
 	hash = siphash(&combined, offsetofend(typeof(combined), dport),
 		       &net_secret);
-	*tsoff = secure_tcpv6_ts_off(saddr, daddr);
 	return seq_scale(hash);
 }
-EXPORT_SYMBOL(secure_tcpv6_seq_and_tsoff);
+EXPORT_SYMBOL(secure_tcpv6_seq);
 
 u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
 			       __be16 dport)
@@ -107,11 +113,12 @@  EXPORT_SYMBOL(secure_ipv6_port_ephemeral);
 #endif
 
 #ifdef CONFIG_INET
-static u32 secure_tcp_ts_off(__be32 saddr, __be32 daddr)
+u32 secure_tcp_ts_off(__be32 saddr, __be32 daddr)
 {
 	if (sysctl_tcp_timestamps != 1)
 		return 0;
 
+	ts_secret_init();
 	return siphash_2u32((__force u32)saddr, (__force u32)daddr,
 			    &ts_secret);
 }
@@ -121,15 +128,15 @@  static u32 secure_tcp_ts_off(__be32 saddr, __be32 daddr)
  * it would be easy enough to have the former function use siphash_4u32, passing
  * the arguments as separate u32.
  */
-u32 secure_tcp_seq_and_tsoff(__be32 saddr, __be32 daddr,
-			     __be16 sport, __be16 dport, u32 *tsoff)
+u32 secure_tcp_seq(__be32 saddr, __be32 daddr,
+		   __be16 sport, __be16 dport)
 {
-	u64 hash;
+	u32 hash;
+
 	net_secret_init();
 	hash = siphash_3u32((__force u32)saddr, (__force u32)daddr,
 			    (__force u32)sport << 16 | (__force u32)dport,
 			    &net_secret);
-	*tsoff = secure_tcp_ts_off(saddr, daddr);
 	return seq_scale(hash);
 }
 
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 496b97e17aaf7ed2cf41cef303cb0696927f66ac..0257d965f11119acf8c55888d6e672d171ef5f08 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -16,6 +16,7 @@ 
 #include <linux/siphash.h>
 #include <linux/kernel.h>
 #include <linux/export.h>
+#include <net/secure_seq.h>
 #include <net/tcp.h>
 #include <net/route.h>
 
@@ -203,7 +204,7 @@  EXPORT_SYMBOL_GPL(__cookie_v4_check);
 
 struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
 				 struct request_sock *req,
-				 struct dst_entry *dst)
+				 struct dst_entry *dst, u32 tsoff)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	struct sock *child;
@@ -213,6 +214,7 @@  struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
 						 NULL, &own_req);
 	if (child) {
 		atomic_set(&req->rsk_refcnt, 1);
+		tcp_sk(child)->tsoffset = tsoff;
 		sock_rps_save_rxhash(child, skb);
 		inet_csk_reqsk_queue_add(sk, req, child);
 	} else {
@@ -292,6 +294,7 @@  struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	struct rtable *rt;
 	__u8 rcv_wscale;
 	struct flowi4 fl4;
+	u32 tsoff = 0;
 
 	if (!sock_net(sk)->ipv4.sysctl_tcp_syncookies || !th->ack || th->rst)
 		goto out;
@@ -311,6 +314,11 @@  struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	memset(&tcp_opt, 0, sizeof(tcp_opt));
 	tcp_parse_options(skb, &tcp_opt, 0, NULL);
 
+	if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {
+		tsoff = secure_tcp_ts_off(ip_hdr(skb)->daddr, ip_hdr(skb)->saddr);
+		tcp_opt.rcv_tsecr -= tsoff;
+	}
+
 	if (!cookie_timestamp_decode(&tcp_opt))
 		goto out;
 
@@ -381,7 +389,7 @@  struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	ireq->rcv_wscale  = rcv_wscale;
 	ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, sock_net(sk), &rt->dst);
 
-	ret = tcp_get_cookie_sock(sk, skb, req, &rt->dst);
+	ret = tcp_get_cookie_sock(sk, skb, req, &rt->dst, tsoff);
 	/* ip_queue_xmit() depends on our flow being setup
 	 * Normal sockets get it right from inet_csk_route_child_sock()
 	 */
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9739962bfb3fd2d39cb13f643def223f4f17fcb6..5a3ad09e2786fb41ad12681d09938c645b69866d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -85,7 +85,6 @@  int sysctl_tcp_dsack __read_mostly = 1;
 int sysctl_tcp_app_win __read_mostly = 31;
 int sysctl_tcp_adv_win_scale __read_mostly = 1;
 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale);
-EXPORT_SYMBOL(sysctl_tcp_timestamps);
 
 /* rfc5961 challenge ack rate limiting */
 int sysctl_tcp_challenge_ack_limit = 1000;
@@ -6347,8 +6346,8 @@  int tcp_conn_request(struct request_sock_ops *rsk_ops,
 	if (security_inet_conn_request(sk, skb, req))
 		goto drop_and_free;
 
-	if (isn && tmp_opt.tstamp_ok)
-		af_ops->init_seq_tsoff(skb, &tcp_rsk(req)->ts_off);
+	if (tmp_opt.tstamp_ok)
+		tcp_rsk(req)->ts_off = af_ops->init_ts_off(skb);
 
 	if (!want_cookie && !isn) {
 		/* Kill the following clause, if you dislike this way. */
@@ -6368,7 +6367,7 @@  int tcp_conn_request(struct request_sock_ops *rsk_ops,
 			goto drop_and_release;
 		}
 
-		isn = af_ops->init_seq_tsoff(skb, &tcp_rsk(req)->ts_off);
+		isn = af_ops->init_seq(skb);
 	}
 	if (!dst) {
 		dst = af_ops->route_req(sk, &fl, req);
@@ -6380,7 +6379,6 @@  int tcp_conn_request(struct request_sock_ops *rsk_ops,
 
 	if (want_cookie) {
 		isn = cookie_init_sequence(af_ops, sk, skb, &req->mss);
-		tcp_rsk(req)->ts_off = 0;
 		req->cookie_ts = tmp_opt.tstamp_ok;
 		if (!tmp_opt.tstamp_ok)
 			inet_rsk(req)->ecn_ok = 0;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index cbbafe546c0f5c5f43531eaf24f5b460264785c6..3a51582bef551f0dffd4e6b3968e23d29fcda6d1 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -94,12 +94,18 @@  static int tcp_v4_md5_hash_hdr(char *md5_hash, const struct tcp_md5sig_key *key,
 struct inet_hashinfo tcp_hashinfo;
 EXPORT_SYMBOL(tcp_hashinfo);
 
-static u32 tcp_v4_init_seq_and_tsoff(const struct sk_buff *skb, u32 *tsoff)
+static u32 tcp_v4_init_seq(const struct sk_buff *skb)
 {
-	return secure_tcp_seq_and_tsoff(ip_hdr(skb)->daddr,
-					ip_hdr(skb)->saddr,
-					tcp_hdr(skb)->dest,
-					tcp_hdr(skb)->source, tsoff);
+	return secure_tcp_seq(ip_hdr(skb)->daddr,
+			      ip_hdr(skb)->saddr,
+			      tcp_hdr(skb)->dest,
+			      tcp_hdr(skb)->source);
+}
+
+static u32 tcp_v4_init_ts_off(const struct sk_buff *skb)
+{
+	return secure_tcp_ts_off(ip_hdr(skb)->daddr,
+				 ip_hdr(skb)->saddr);
 }
 
 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp)
@@ -145,7 +151,6 @@  int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 	struct flowi4 *fl4;
 	struct rtable *rt;
 	int err;
-	u32 seq;
 	struct ip_options_rcu *inet_opt;
 	struct inet_timewait_death_row *tcp_death_row = &sock_net(sk)->ipv4.tcp_death_row;
 
@@ -232,13 +237,13 @@  int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 	rt = NULL;
 
 	if (likely(!tp->repair)) {
-		seq = secure_tcp_seq_and_tsoff(inet->inet_saddr,
-					       inet->inet_daddr,
-					       inet->inet_sport,
-					       usin->sin_port,
-					       &tp->tsoffset);
 		if (!tp->write_seq)
-			tp->write_seq = seq;
+			tp->write_seq = secure_tcp_seq(inet->inet_saddr,
+						       inet->inet_daddr,
+						       inet->inet_sport,
+						       usin->sin_port);
+		tp->tsoffset = secure_tcp_ts_off(inet->inet_saddr,
+						 inet->inet_daddr);
 	}
 
 	inet->inet_id = tp->write_seq ^ jiffies;
@@ -1239,7 +1244,8 @@  static const struct tcp_request_sock_ops tcp_request_sock_ipv4_ops = {
 	.cookie_init_seq =	cookie_v4_init_sequence,
 #endif
 	.route_req	=	tcp_v4_route_req,
-	.init_seq_tsoff	=	tcp_v4_init_seq_and_tsoff,
+	.init_seq	=	tcp_v4_init_seq,
+	.init_ts_off	=	tcp_v4_init_ts_off,
 	.send_synack	=	tcp_v4_send_synack,
 };
 
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 895ff650db43017ef39344679771d94ad6eaaf00..5abc3692b9011b140816dc4ce6223e79e5defddb 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -18,6 +18,7 @@ 
 #include <linux/random.h>
 #include <linux/siphash.h>
 #include <linux/kernel.h>
+#include <net/secure_seq.h>
 #include <net/ipv6.h>
 #include <net/tcp.h>
 
@@ -143,6 +144,7 @@  struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	int mss;
 	struct dst_entry *dst;
 	__u8 rcv_wscale;
+	u32 tsoff = 0;
 
 	if (!sock_net(sk)->ipv4.sysctl_tcp_syncookies || !th->ack || th->rst)
 		goto out;
@@ -162,6 +164,12 @@  struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	memset(&tcp_opt, 0, sizeof(tcp_opt));
 	tcp_parse_options(skb, &tcp_opt, 0, NULL);
 
+	if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {
+		tsoff = secure_tcpv6_ts_off(ipv6_hdr(skb)->daddr.s6_addr32,
+					    ipv6_hdr(skb)->saddr.s6_addr32);
+		tcp_opt.rcv_tsecr -= tsoff;
+	}
+
 	if (!cookie_timestamp_decode(&tcp_opt))
 		goto out;
 
@@ -242,7 +250,7 @@  struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	ireq->rcv_wscale = rcv_wscale;
 	ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, sock_net(sk), dst);
 
-	ret = tcp_get_cookie_sock(sk, skb, req, dst);
+	ret = tcp_get_cookie_sock(sk, skb, req, dst, tsoff);
 out:
 	return ret;
 out_free:
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 8e42e8f54b705ed8780890c7434feeff1055599a..aeb9497b5bb754f2277dec4a4dec02bf25bdbbe5 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -101,12 +101,18 @@  static void inet6_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
 	}
 }
 
-static u32 tcp_v6_init_seq_and_tsoff(const struct sk_buff *skb, u32 *tsoff)
+static u32 tcp_v6_init_seq(const struct sk_buff *skb)
 {
-	return secure_tcpv6_seq_and_tsoff(ipv6_hdr(skb)->daddr.s6_addr32,
-					  ipv6_hdr(skb)->saddr.s6_addr32,
-					  tcp_hdr(skb)->dest,
-					  tcp_hdr(skb)->source, tsoff);
+	return secure_tcpv6_seq(ipv6_hdr(skb)->daddr.s6_addr32,
+				ipv6_hdr(skb)->saddr.s6_addr32,
+				tcp_hdr(skb)->dest,
+				tcp_hdr(skb)->source);
+}
+
+static u32 tcp_v6_init_ts_off(const struct sk_buff *skb)
+{
+	return secure_tcpv6_ts_off(ipv6_hdr(skb)->daddr.s6_addr32,
+				   ipv6_hdr(skb)->saddr.s6_addr32);
 }
 
 static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
@@ -122,7 +128,6 @@  static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 	struct flowi6 fl6;
 	struct dst_entry *dst;
 	int addr_type;
-	u32 seq;
 	int err;
 	struct inet_timewait_death_row *tcp_death_row = &sock_net(sk)->ipv4.tcp_death_row;
 
@@ -282,13 +287,13 @@  static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 	sk_set_txhash(sk);
 
 	if (likely(!tp->repair)) {
-		seq = secure_tcpv6_seq_and_tsoff(np->saddr.s6_addr32,
-						 sk->sk_v6_daddr.s6_addr32,
-						 inet->inet_sport,
-						 inet->inet_dport,
-						 &tp->tsoffset);
 		if (!tp->write_seq)
-			tp->write_seq = seq;
+			tp->write_seq = secure_tcpv6_seq(np->saddr.s6_addr32,
+							 sk->sk_v6_daddr.s6_addr32,
+							 inet->inet_sport,
+							 inet->inet_dport);
+		tp->tsoffset = secure_tcpv6_ts_off(np->saddr.s6_addr32,
+						   sk->sk_v6_daddr.s6_addr32);
 	}
 
 	if (tcp_fastopen_defer_connect(sk, &err))
@@ -749,7 +754,8 @@  static const struct tcp_request_sock_ops tcp_request_sock_ipv6_ops = {
 	.cookie_init_seq =	cookie_v6_init_sequence,
 #endif
 	.route_req	=	tcp_v6_route_req,
-	.init_seq_tsoff	=	tcp_v6_init_seq_and_tsoff,
+	.init_seq	=	tcp_v6_init_seq,
+	.init_ts_off	=	tcp_v6_init_ts_off,
 	.send_synack	=	tcp_v6_send_synack,
 };