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tcp: secure_seq: add back ports to TS offset
This reverts 28ee1b7 ("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: 28ee1b7 ("secure_seq: downgrade to per-host timestamp offsets") Reported-by: Zhouyan Deng <dengzhouyan_nwpu@163.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com> Acked-by: Florian Westphal <fw@strlen.de> Link: https://patch.msgid.link/20260302205527.1982836-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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8 files changed

Lines changed: 127 additions & 108 deletions

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‎include/net/secure_seq.h‎

Lines changed: 38 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -5,16 +5,47 @@
55
#include <linux/types.h>
66

77
struct net;
8+
extern struct net init_net;
9+
10+
union tcp_seq_and_ts_off {
11+
struct {
12+
u32 seq;
13+
u32 ts_off;
14+
};
15+
u64 hash64;
16+
};
817

918
u64 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport);
1019
u64 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
1120
__be16 dport);
12-
u32 secure_tcp_seq(__be32 saddr, __be32 daddr,
13-
__be16 sport, __be16 dport);
14-
u32 secure_tcp_ts_off(const struct net *net, __be32 saddr, __be32 daddr);
15-
u32 secure_tcpv6_seq(const __be32 *saddr, const __be32 *daddr,
16-
__be16 sport, __be16 dport);
17-
u32 secure_tcpv6_ts_off(const struct net *net,
18-
const __be32 *saddr, const __be32 *daddr);
21+
union tcp_seq_and_ts_off
22+
secure_tcp_seq_and_ts_off(const struct net *net, __be32 saddr, __be32 daddr,
23+
__be16 sport, __be16 dport);
24+
25+
static inline u32 secure_tcp_seq(__be32 saddr, __be32 daddr,
26+
__be16 sport, __be16 dport)
27+
{
28+
union tcp_seq_and_ts_off ts;
29+
30+
ts = secure_tcp_seq_and_ts_off(&init_net, saddr, daddr,
31+
sport, dport);
32+
33+
return ts.seq;
34+
}
35+
36+
union tcp_seq_and_ts_off
37+
secure_tcpv6_seq_and_ts_off(const struct net *net, const __be32 *saddr,
38+
const __be32 *daddr,
39+
__be16 sport, __be16 dport);
40+
41+
static inline u32 secure_tcpv6_seq(const __be32 *saddr, const __be32 *daddr,
42+
__be16 sport, __be16 dport)
43+
{
44+
union tcp_seq_and_ts_off ts;
45+
46+
ts = secure_tcpv6_seq_and_ts_off(&init_net, saddr, daddr,
47+
sport, dport);
1948

49+
return ts.seq;
50+
}
2051
#endif /* _NET_SECURE_SEQ */

‎include/net/tcp.h‎

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -43,6 +43,7 @@
4343
#include <net/dst.h>
4444
#include <net/mptcp.h>
4545
#include <net/xfrm.h>
46+
#include <net/secure_seq.h>
4647

4748
#include <linux/seq_file.h>
4849
#include <linux/memcontrol.h>
@@ -2464,8 +2465,9 @@ struct tcp_request_sock_ops {
24642465
struct flowi *fl,
24652466
struct request_sock *req,
24662467
u32 tw_isn);
2467-
u32 (*init_seq)(const struct sk_buff *skb);
2468-
u32 (*init_ts_off)(const struct net *net, const struct sk_buff *skb);
2468+
union tcp_seq_and_ts_off (*init_seq_and_ts_off)(
2469+
const struct net *net,
2470+
const struct sk_buff *skb);
24692471
int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
24702472
struct flowi *fl, struct request_sock *req,
24712473
struct tcp_fastopen_cookie *foc,

‎net/core/secure_seq.c‎

Lines changed: 29 additions & 51 deletions
Original file line numberDiff line numberDiff line change
@@ -20,19 +20,13 @@
2020
#include <net/tcp.h>
2121

2222
static siphash_aligned_key_t net_secret;
23-
static siphash_aligned_key_t ts_secret;
2423

2524
#define EPHEMERAL_PORT_SHUFFLE_PERIOD (10 * HZ)
2625

2726
static __always_inline void net_secret_init(void)
2827
{
2928
net_get_random_once(&net_secret, sizeof(net_secret));
3029
}
31-
32-
static __always_inline void ts_secret_init(void)
33-
{
34-
net_get_random_once(&ts_secret, sizeof(ts_secret));
35-
}
3630
#endif
3731

3832
#ifdef CONFIG_INET
@@ -53,28 +47,9 @@ static u32 seq_scale(u32 seq)
5347
#endif
5448

5549
#if IS_ENABLED(CONFIG_IPV6)
56-
u32 secure_tcpv6_ts_off(const struct net *net,
57-
const __be32 *saddr, const __be32 *daddr)
58-
{
59-
const struct {
60-
struct in6_addr saddr;
61-
struct in6_addr daddr;
62-
} __aligned(SIPHASH_ALIGNMENT) combined = {
63-
.saddr = *(struct in6_addr *)saddr,
64-
.daddr = *(struct in6_addr *)daddr,
65-
};
66-
67-
if (READ_ONCE(net->ipv4.sysctl_tcp_timestamps) != 1)
68-
return 0;
69-
70-
ts_secret_init();
71-
return siphash(&combined, offsetofend(typeof(combined), daddr),
72-
&ts_secret);
73-
}
74-
EXPORT_IPV6_MOD(secure_tcpv6_ts_off);
75-
76-
u32 secure_tcpv6_seq(const __be32 *saddr, const __be32 *daddr,
77-
__be16 sport, __be16 dport)
50+
union tcp_seq_and_ts_off
51+
secure_tcpv6_seq_and_ts_off(const struct net *net, const __be32 *saddr,
52+
const __be32 *daddr, __be16 sport, __be16 dport)
7853
{
7954
const struct {
8055
struct in6_addr saddr;
@@ -87,14 +62,20 @@ u32 secure_tcpv6_seq(const __be32 *saddr, const __be32 *daddr,
8762
.sport = sport,
8863
.dport = dport
8964
};
90-
u32 hash;
65+
union tcp_seq_and_ts_off st;
9166

9267
net_secret_init();
93-
hash = siphash(&combined, offsetofend(typeof(combined), dport),
94-
&net_secret);
95-
return seq_scale(hash);
68+
69+
st.hash64 = siphash(&combined, offsetofend(typeof(combined), dport),
70+
&net_secret);
71+
72+
if (READ_ONCE(net->ipv4.sysctl_tcp_timestamps) != 1)
73+
st.ts_off = 0;
74+
75+
st.seq = seq_scale(st.seq);
76+
return st;
9677
}
97-
EXPORT_SYMBOL(secure_tcpv6_seq);
78+
EXPORT_SYMBOL(secure_tcpv6_seq_and_ts_off);
9879

9980
u64 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
10081
__be16 dport)
@@ -118,33 +99,30 @@ EXPORT_SYMBOL(secure_ipv6_port_ephemeral);
11899
#endif
119100

120101
#ifdef CONFIG_INET
121-
u32 secure_tcp_ts_off(const struct net *net, __be32 saddr, __be32 daddr)
122-
{
123-
if (READ_ONCE(net->ipv4.sysctl_tcp_timestamps) != 1)
124-
return 0;
125-
126-
ts_secret_init();
127-
return siphash_2u32((__force u32)saddr, (__force u32)daddr,
128-
&ts_secret);
129-
}
130-
131102
/* secure_tcp_seq_and_tsoff(a, b, 0, d) == secure_ipv4_port_ephemeral(a, b, d),
132103
* but fortunately, `sport' cannot be 0 in any circumstances. If this changes,
133104
* it would be easy enough to have the former function use siphash_4u32, passing
134105
* the arguments as separate u32.
135106
*/
136-
u32 secure_tcp_seq(__be32 saddr, __be32 daddr,
137-
__be16 sport, __be16 dport)
107+
union tcp_seq_and_ts_off
108+
secure_tcp_seq_and_ts_off(const struct net *net, __be32 saddr, __be32 daddr,
109+
__be16 sport, __be16 dport)
138110
{
139-
u32 hash;
111+
u32 ports = (__force u32)sport << 16 | (__force u32)dport;
112+
union tcp_seq_and_ts_off st;
140113

141114
net_secret_init();
142-
hash = siphash_3u32((__force u32)saddr, (__force u32)daddr,
143-
(__force u32)sport << 16 | (__force u32)dport,
144-
&net_secret);
145-
return seq_scale(hash);
115+
116+
st.hash64 = siphash_3u32((__force u32)saddr, (__force u32)daddr,
117+
ports, &net_secret);
118+
119+
if (READ_ONCE(net->ipv4.sysctl_tcp_timestamps) != 1)
120+
st.ts_off = 0;
121+
122+
st.seq = seq_scale(st.seq);
123+
return st;
146124
}
147-
EXPORT_SYMBOL_GPL(secure_tcp_seq);
125+
EXPORT_SYMBOL_GPL(secure_tcp_seq_and_ts_off);
148126

149127
u64 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
150128
{

‎net/ipv4/syncookies.c‎

Lines changed: 8 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -378,9 +378,14 @@ static struct request_sock *cookie_tcp_check(struct net *net, struct sock *sk,
378378
tcp_parse_options(net, skb, &tcp_opt, 0, NULL);
379379

380380
if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {
381-
tsoff = secure_tcp_ts_off(net,
382-
ip_hdr(skb)->daddr,
383-
ip_hdr(skb)->saddr);
381+
union tcp_seq_and_ts_off st;
382+
383+
st = secure_tcp_seq_and_ts_off(net,
384+
ip_hdr(skb)->daddr,
385+
ip_hdr(skb)->saddr,
386+
tcp_hdr(skb)->dest,
387+
tcp_hdr(skb)->source);
388+
tsoff = st.ts_off;
384389
tcp_opt.rcv_tsecr -= tsoff;
385390
}
386391

‎net/ipv4/tcp_input.c‎

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7646,6 +7646,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
76467646
const struct tcp_sock *tp = tcp_sk(sk);
76477647
struct net *net = sock_net(sk);
76487648
struct sock *fastopen_sk = NULL;
7649+
union tcp_seq_and_ts_off st;
76497650
struct request_sock *req;
76507651
bool want_cookie = false;
76517652
struct dst_entry *dst;
@@ -7715,9 +7716,12 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
77157716
if (!dst)
77167717
goto drop_and_free;
77177718

7719+
if (tmp_opt.tstamp_ok || (!want_cookie && !isn))
7720+
st = af_ops->init_seq_and_ts_off(net, skb);
7721+
77187722
if (tmp_opt.tstamp_ok) {
77197723
tcp_rsk(req)->req_usec_ts = dst_tcp_usec_ts(dst);
7720-
tcp_rsk(req)->ts_off = af_ops->init_ts_off(net, skb);
7724+
tcp_rsk(req)->ts_off = st.ts_off;
77217725
}
77227726
if (!want_cookie && !isn) {
77237727
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,
77397743
goto drop_and_release;
77407744
}
77417745

7742-
isn = af_ops->init_seq(skb);
7746+
isn = st.seq;
77437747
}
77447748

77457749
tcp_ecn_create_request(req, skb, sk, dst);

‎net/ipv4/tcp_ipv4.c‎

Lines changed: 17 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -105,17 +105,14 @@ static DEFINE_PER_CPU(struct sock_bh_locked, ipv4_tcp_sk) = {
105105

106106
static DEFINE_MUTEX(tcp_exit_batch_mutex);
107107

108-
static u32 tcp_v4_init_seq(const struct sk_buff *skb)
108+
static union tcp_seq_and_ts_off
109+
tcp_v4_init_seq_and_ts_off(const struct net *net, const struct sk_buff *skb)
109110
{
110-
return secure_tcp_seq(ip_hdr(skb)->daddr,
111-
ip_hdr(skb)->saddr,
112-
tcp_hdr(skb)->dest,
113-
tcp_hdr(skb)->source);
114-
}
115-
116-
static u32 tcp_v4_init_ts_off(const struct net *net, const struct sk_buff *skb)
117-
{
118-
return secure_tcp_ts_off(net, ip_hdr(skb)->daddr, ip_hdr(skb)->saddr);
111+
return secure_tcp_seq_and_ts_off(net,
112+
ip_hdr(skb)->daddr,
113+
ip_hdr(skb)->saddr,
114+
tcp_hdr(skb)->dest,
115+
tcp_hdr(skb)->source);
119116
}
120117

121118
int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp)
@@ -327,15 +324,16 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr_unsized *uaddr, int addr_len
327324
rt = NULL;
328325

329326
if (likely(!tp->repair)) {
327+
union tcp_seq_and_ts_off st;
328+
329+
st = secure_tcp_seq_and_ts_off(net,
330+
inet->inet_saddr,
331+
inet->inet_daddr,
332+
inet->inet_sport,
333+
usin->sin_port);
330334
if (!tp->write_seq)
331-
WRITE_ONCE(tp->write_seq,
332-
secure_tcp_seq(inet->inet_saddr,
333-
inet->inet_daddr,
334-
inet->inet_sport,
335-
usin->sin_port));
336-
WRITE_ONCE(tp->tsoffset,
337-
secure_tcp_ts_off(net, inet->inet_saddr,
338-
inet->inet_daddr));
335+
WRITE_ONCE(tp->write_seq, st.seq);
336+
WRITE_ONCE(tp->tsoffset, st.ts_off);
339337
}
340338

341339
atomic_set(&inet->inet_id, get_random_u16());
@@ -1677,8 +1675,7 @@ const struct tcp_request_sock_ops tcp_request_sock_ipv4_ops = {
16771675
.cookie_init_seq = cookie_v4_init_sequence,
16781676
#endif
16791677
.route_req = tcp_v4_route_req,
1680-
.init_seq = tcp_v4_init_seq,
1681-
.init_ts_off = tcp_v4_init_ts_off,
1678+
.init_seq_and_ts_off = tcp_v4_init_seq_and_ts_off,
16821679
.send_synack = tcp_v4_send_synack,
16831680
};
16841681

‎net/ipv6/syncookies.c‎

Lines changed: 8 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -151,9 +151,14 @@ static struct request_sock *cookie_tcp_check(struct net *net, struct sock *sk,
151151
tcp_parse_options(net, skb, &tcp_opt, 0, NULL);
152152

153153
if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {
154-
tsoff = secure_tcpv6_ts_off(net,
155-
ipv6_hdr(skb)->daddr.s6_addr32,
156-
ipv6_hdr(skb)->saddr.s6_addr32);
154+
union tcp_seq_and_ts_off st;
155+
156+
st = secure_tcpv6_seq_and_ts_off(net,
157+
ipv6_hdr(skb)->daddr.s6_addr32,
158+
ipv6_hdr(skb)->saddr.s6_addr32,
159+
tcp_hdr(skb)->dest,
160+
tcp_hdr(skb)->source);
161+
tsoff = st.ts_off;
157162
tcp_opt.rcv_tsecr -= tsoff;
158163
}
159164

‎net/ipv6/tcp_ipv6.c‎

Lines changed: 17 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -105,18 +105,14 @@ static void inet6_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
105105
}
106106
}
107107

108-
static u32 tcp_v6_init_seq(const struct sk_buff *skb)
108+
static union tcp_seq_and_ts_off
109+
tcp_v6_init_seq_and_ts_off(const struct net *net, const struct sk_buff *skb)
109110
{
110-
return secure_tcpv6_seq(ipv6_hdr(skb)->daddr.s6_addr32,
111-
ipv6_hdr(skb)->saddr.s6_addr32,
112-
tcp_hdr(skb)->dest,
113-
tcp_hdr(skb)->source);
114-
}
115-
116-
static u32 tcp_v6_init_ts_off(const struct net *net, const struct sk_buff *skb)
117-
{
118-
return secure_tcpv6_ts_off(net, ipv6_hdr(skb)->daddr.s6_addr32,
119-
ipv6_hdr(skb)->saddr.s6_addr32);
111+
return secure_tcpv6_seq_and_ts_off(net,
112+
ipv6_hdr(skb)->daddr.s6_addr32,
113+
ipv6_hdr(skb)->saddr.s6_addr32,
114+
tcp_hdr(skb)->dest,
115+
tcp_hdr(skb)->source);
120116
}
121117

122118
static int tcp_v6_pre_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
@@ -320,14 +316,16 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
320316
sk_set_txhash(sk);
321317

322318
if (likely(!tp->repair)) {
319+
union tcp_seq_and_ts_off st;
320+
321+
st = secure_tcpv6_seq_and_ts_off(net,
322+
np->saddr.s6_addr32,
323+
sk->sk_v6_daddr.s6_addr32,
324+
inet->inet_sport,
325+
inet->inet_dport);
323326
if (!tp->write_seq)
324-
WRITE_ONCE(tp->write_seq,
325-
secure_tcpv6_seq(np->saddr.s6_addr32,
326-
sk->sk_v6_daddr.s6_addr32,
327-
inet->inet_sport,
328-
inet->inet_dport));
329-
tp->tsoffset = secure_tcpv6_ts_off(net, np->saddr.s6_addr32,
330-
sk->sk_v6_daddr.s6_addr32);
327+
WRITE_ONCE(tp->write_seq, st.seq);
328+
tp->tsoffset = st.ts_off;
331329
}
332330

333331
if (tcp_fastopen_defer_connect(sk, &err))
@@ -817,8 +815,7 @@ const struct tcp_request_sock_ops tcp_request_sock_ipv6_ops = {
817815
.cookie_init_seq = cookie_v6_init_sequence,
818816
#endif
819817
.route_req = tcp_v6_route_req,
820-
.init_seq = tcp_v6_init_seq,
821-
.init_ts_off = tcp_v6_init_ts_off,
818+
.init_seq_and_ts_off = tcp_v6_init_seq_and_ts_off,
822819
.send_synack = tcp_v6_send_synack,
823820
};
824821

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