Commit 165573e4 authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

tcp: secure_seq: add back ports to TS offset 



This reverts 28ee1b74 ("secure_seq: downgrade to per-host timestamp offsets")

tcp_tw_recycle went away in 2017.

Zhouyan Deng reported off-path TCP source port leakage via
SYN cookie side-channel that can be fixed in multiple ways.

One of them is to bring back TCP ports in TS offset randomization.

As a bonus, we perform a single siphash() computation
to provide both an ISN and a TS offset.

Fixes: 28ee1b74 ("secure_seq: downgrade to per-host timestamp offsets")
Reported-by: default avatarZhouyan Deng <dengzhouyan_nwpu@163.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarKuniyuki Iwashima <kuniyu@google.com>
Acked-by: default avatarFlorian Westphal <fw@strlen.de>
Link: https://patch.msgid.link/20260302205527.1982836-1-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 7f083faf

include/net/secure_seq.h

+38 −7
Original line number Diff line number Diff line
@@ -5,16 +5,47 @@ 
#include <linux/types.h>



struct net;

extern struct net init_net;



union tcp_seq_and_ts_off {

	struct {

		u32 seq;

		u32 ts_off;

	};

	u64 hash64;

};



u64 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport);

u64 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,

			       __be16 dport);

u32 secure_tcp_seq(__be32 saddr, __be32 daddr,

union tcp_seq_and_ts_off

secure_tcp_seq_and_ts_off(const struct net *net, __be32 saddr, __be32 daddr,

			  __be16 sport, __be16 dport);

u32 secure_tcp_ts_off(const struct net *net, __be32 saddr, __be32 daddr);

u32 secure_tcpv6_seq(const __be32 *saddr, const __be32 *daddr,



static inline u32 secure_tcp_seq(__be32 saddr, __be32 daddr,

				 __be16 sport, __be16 dport)

{

	union tcp_seq_and_ts_off ts;



	ts = secure_tcp_seq_and_ts_off(&init_net, saddr, daddr,

				       sport, dport);



	return ts.seq;

}



union tcp_seq_and_ts_off

secure_tcpv6_seq_and_ts_off(const struct net *net, const __be32 *saddr,

			    const __be32 *daddr,

			    __be16 sport, __be16 dport);

u32 secure_tcpv6_ts_off(const struct net *net,

			const __be32 *saddr, const __be32 *daddr);



static inline u32 secure_tcpv6_seq(const __be32 *saddr, const __be32 *daddr,

				   __be16 sport, __be16 dport)

{

	union tcp_seq_and_ts_off ts;



	ts = secure_tcpv6_seq_and_ts_off(&init_net, saddr, daddr,

					 sport, dport);



	return ts.seq;

}

#endif /* _NET_SECURE_SEQ */

include/net/tcp.h

+4 −2
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ 
#include <net/dst.h>

#include <net/mptcp.h>

#include <net/xfrm.h>

#include <net/secure_seq.h>



#include <linux/seq_file.h>

#include <linux/memcontrol.h>
@@ -2464,8 +2465,9 @@ struct tcp_request_sock_ops { 
				       struct flowi *fl,

				       struct request_sock *req,

				       u32 tw_isn);

	u32 (*init_seq)(const struct sk_buff *skb);

	u32 (*init_ts_off)(const struct net *net, const struct sk_buff *skb);

	union tcp_seq_and_ts_off (*init_seq_and_ts_off)(

					const struct net *net,

					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,

net/core/secure_seq.c

+29 −51
Original line number Diff line number Diff line
@@ -20,7 +20,6 @@ 
#include <net/tcp.h>



static siphash_aligned_key_t net_secret;

static siphash_aligned_key_t ts_secret;



#define EPHEMERAL_PORT_SHUFFLE_PERIOD (10 * HZ)
@@ -28,11 +27,6 @@ static __always_inline void net_secret_init(void) 
{

	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
@@ -53,28 +47,9 @@ static u32 seq_scale(u32 seq) 
#endif



#if IS_ENABLED(CONFIG_IPV6)

u32 secure_tcpv6_ts_off(const struct net *net,

			const __be32 *saddr, const __be32 *daddr)

{

	const struct {

		struct in6_addr saddr;

		struct in6_addr daddr;

	} __aligned(SIPHASH_ALIGNMENT) combined = {

		.saddr = *(struct in6_addr *)saddr,

		.daddr = *(struct in6_addr *)daddr,

	};



	if (READ_ONCE(net->ipv4.sysctl_tcp_timestamps) != 1)

		return 0;



	ts_secret_init();

	return siphash(&combined, offsetofend(typeof(combined), daddr),

		       &ts_secret);

}

EXPORT_IPV6_MOD(secure_tcpv6_ts_off);



u32 secure_tcpv6_seq(const __be32 *saddr, const __be32 *daddr,

		     __be16 sport, __be16 dport)

union tcp_seq_and_ts_off

secure_tcpv6_seq_and_ts_off(const struct net *net, const __be32 *saddr,

			    const __be32 *daddr, __be16 sport, __be16 dport)

{

	const struct {

		struct in6_addr saddr;
@@ -87,14 +62,20 @@ u32 secure_tcpv6_seq(const __be32 *saddr, const __be32 *daddr, 
		.sport = sport,

		.dport = dport

	};

	u32 hash;

	union tcp_seq_and_ts_off st;



	net_secret_init();

	hash = siphash(&combined, offsetofend(typeof(combined), dport),



	st.hash64 = siphash(&combined, offsetofend(typeof(combined), dport),

			    &net_secret);

	return seq_scale(hash);



	if (READ_ONCE(net->ipv4.sysctl_tcp_timestamps) != 1)

		st.ts_off = 0;



	st.seq = seq_scale(st.seq);

	return st;

}

EXPORT_SYMBOL(secure_tcpv6_seq);

EXPORT_SYMBOL(secure_tcpv6_seq_and_ts_off);



u64 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,

			       __be16 dport)
@@ -118,33 +99,30 @@ EXPORT_SYMBOL(secure_ipv6_port_ephemeral); 
#endif



#ifdef CONFIG_INET

u32 secure_tcp_ts_off(const struct net *net, __be32 saddr, __be32 daddr)

{

	if (READ_ONCE(net->ipv4.sysctl_tcp_timestamps) != 1)

		return 0;



	ts_secret_init();

	return siphash_2u32((__force u32)saddr, (__force u32)daddr,

			    &ts_secret);

}



/* secure_tcp_seq_and_tsoff(a, b, 0, d) == secure_ipv4_port_ephemeral(a, b, d),

 * but fortunately, `sport' cannot be 0 in any circumstances. If this changes,

 * it would be easy enough to have the former function use siphash_4u32, passing

 * the arguments as separate u32.

 */

u32 secure_tcp_seq(__be32 saddr, __be32 daddr,

union tcp_seq_and_ts_off

secure_tcp_seq_and_ts_off(const struct net *net, __be32 saddr, __be32 daddr,

			  __be16 sport, __be16 dport)

{

	u32 hash;

	u32 ports = (__force u32)sport << 16 | (__force u32)dport;

	union tcp_seq_and_ts_off st;



	net_secret_init();

	hash = siphash_3u32((__force u32)saddr, (__force u32)daddr,

			    (__force u32)sport << 16 | (__force u32)dport,

			    &net_secret);

	return seq_scale(hash);



	st.hash64 = siphash_3u32((__force u32)saddr, (__force u32)daddr,

				 ports, &net_secret);



	if (READ_ONCE(net->ipv4.sysctl_tcp_timestamps) != 1)

		st.ts_off = 0;



	st.seq = seq_scale(st.seq);

	return st;

}

EXPORT_SYMBOL_GPL(secure_tcp_seq);

EXPORT_SYMBOL_GPL(secure_tcp_seq_and_ts_off);



u64 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)

{

net/ipv4/syncookies.c

+8 −3
Original line number Diff line number Diff line
@@ -378,9 +378,14 @@ static struct request_sock *cookie_tcp_check(struct net *net, struct sock *sk, 
	tcp_parse_options(net, skb, &tcp_opt, 0, NULL);



	if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {

		tsoff = secure_tcp_ts_off(net,

		union tcp_seq_and_ts_off st;



		st = secure_tcp_seq_and_ts_off(net,

					       ip_hdr(skb)->daddr,

					  ip_hdr(skb)->saddr);

					       ip_hdr(skb)->saddr,

					       tcp_hdr(skb)->dest,

					       tcp_hdr(skb)->source);

		tsoff = st.ts_off;

		tcp_opt.rcv_tsecr -= tsoff;

	}

net/ipv4/tcp_input.c

+6 −2
Original line number Diff line number Diff line
@@ -7646,6 +7646,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, 
	const struct tcp_sock *tp = tcp_sk(sk);

	struct net *net = sock_net(sk);

	struct sock *fastopen_sk = NULL;

	union tcp_seq_and_ts_off st;

	struct request_sock *req;

	bool want_cookie = false;

	struct dst_entry *dst;
@@ -7715,9 +7716,12 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, 
	if (!dst)

		goto drop_and_free;



	if (tmp_opt.tstamp_ok || (!want_cookie && !isn))

		st = af_ops->init_seq_and_ts_off(net, skb);



	if (tmp_opt.tstamp_ok) {

		tcp_rsk(req)->req_usec_ts = dst_tcp_usec_ts(dst);

		tcp_rsk(req)->ts_off = af_ops->init_ts_off(net, skb);

		tcp_rsk(req)->ts_off = st.ts_off;

	}

	if (!want_cookie && !isn) {

		int max_syn_backlog = READ_ONCE(net->ipv4.sysctl_max_syn_backlog);
@@ -7739,7 +7743,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, 
			goto drop_and_release;

		}



		isn = af_ops->init_seq(skb);

		isn = st.seq;

	}



	tcp_ecn_create_request(req, skb, sk, dst);