1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
4 */
5
6 #include <linux/kernel.h>
7 #include <linux/init.h>
8 #include <linux/module.h>
9 #include <linux/cache.h>
10 #include <linux/random.h>
11 #include <linux/hrtimer.h>
12 #include <linux/ktime.h>
13 #include <linux/string.h>
14 #include <linux/net.h>
15 #include <linux/siphash.h>
16 #include <net/secure_seq.h>
17
18 #if IS_ENABLED(CONFIG_IPV6) || IS_ENABLED(CONFIG_INET)
19 #include <linux/in6.h>
20 #include <net/tcp.h>
21
22 static siphash_aligned_key_t net_secret;
23 static siphash_aligned_key_t ts_secret;
24
25 #define EPHEMERAL_PORT_SHUFFLE_PERIOD (10 * HZ)
26
net_secret_init(void)27 static __always_inline void net_secret_init(void)
28 {
29 net_get_random_once(&net_secret, sizeof(net_secret));
30 }
31
ts_secret_init(void)32 static __always_inline void ts_secret_init(void)
33 {
34 net_get_random_once(&ts_secret, sizeof(ts_secret));
35 }
36 #endif
37
38 #ifdef CONFIG_INET
seq_scale(u32 seq)39 static u32 seq_scale(u32 seq)
40 {
41 /*
42 * As close as possible to RFC 793, which
43 * suggests using a 250 kHz clock.
44 * Further reading shows this assumes 2 Mb/s networks.
45 * For 10 Mb/s Ethernet, a 1 MHz clock is appropriate.
46 * For 10 Gb/s Ethernet, a 1 GHz clock should be ok, but
47 * we also need to limit the resolution so that the u32 seq
48 * overlaps less than one time per MSL (2 minutes).
49 * Choosing a clock of 64 ns period is OK. (period of 274 s)
50 */
51 return seq + (ktime_get_real_ns() >> 6);
52 }
53 #endif
54
55 #if IS_ENABLED(CONFIG_IPV6)
secure_tcpv6_ts_off(const struct net * net,const __be32 * saddr,const __be32 * daddr)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_SYMBOL(secure_tcpv6_ts_off);
75
secure_tcpv6_seq(const __be32 * saddr,const __be32 * daddr,__be16 sport,__be16 dport)76 u32 secure_tcpv6_seq(const __be32 *saddr, const __be32 *daddr,
77 __be16 sport, __be16 dport)
78 {
79 const struct {
80 struct in6_addr saddr;
81 struct in6_addr daddr;
82 __be16 sport;
83 __be16 dport;
84 } __aligned(SIPHASH_ALIGNMENT) combined = {
85 .saddr = *(struct in6_addr *)saddr,
86 .daddr = *(struct in6_addr *)daddr,
87 .sport = sport,
88 .dport = dport
89 };
90 u32 hash;
91
92 net_secret_init();
93 hash = siphash(&combined, offsetofend(typeof(combined), dport),
94 &net_secret);
95 return seq_scale(hash);
96 }
97 EXPORT_SYMBOL(secure_tcpv6_seq);
98
secure_ipv6_port_ephemeral(const __be32 * saddr,const __be32 * daddr,__be16 dport)99 u64 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
100 __be16 dport)
101 {
102 const struct {
103 struct in6_addr saddr;
104 struct in6_addr daddr;
105 unsigned int timeseed;
106 __be16 dport;
107 } __aligned(SIPHASH_ALIGNMENT) combined = {
108 .saddr = *(struct in6_addr *)saddr,
109 .daddr = *(struct in6_addr *)daddr,
110 .timeseed = jiffies / EPHEMERAL_PORT_SHUFFLE_PERIOD,
111 .dport = dport,
112 };
113 net_secret_init();
114 return siphash(&combined, offsetofend(typeof(combined), dport),
115 &net_secret);
116 }
117 EXPORT_SYMBOL(secure_ipv6_port_ephemeral);
118 #endif
119
120 #ifdef CONFIG_INET
secure_tcp_ts_off(const struct net * net,__be32 saddr,__be32 daddr)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
131 /* secure_tcp_seq_and_tsoff(a, b, 0, d) == secure_ipv4_port_ephemeral(a, b, d),
132 * but fortunately, `sport' cannot be 0 in any circumstances. If this changes,
133 * it would be easy enough to have the former function use siphash_4u32, passing
134 * the arguments as separate u32.
135 */
secure_tcp_seq(__be32 saddr,__be32 daddr,__be16 sport,__be16 dport)136 u32 secure_tcp_seq(__be32 saddr, __be32 daddr,
137 __be16 sport, __be16 dport)
138 {
139 u32 hash;
140
141 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);
146 }
147 EXPORT_SYMBOL_GPL(secure_tcp_seq);
148
secure_ipv4_port_ephemeral(__be32 saddr,__be32 daddr,__be16 dport)149 u64 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
150 {
151 net_secret_init();
152 return siphash_4u32((__force u32)saddr, (__force u32)daddr,
153 (__force u16)dport,
154 jiffies / EPHEMERAL_PORT_SHUFFLE_PERIOD,
155 &net_secret);
156 }
157 EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);
158 #endif
159
160 #if IS_ENABLED(CONFIG_IP_DCCP)
secure_dccp_sequence_number(__be32 saddr,__be32 daddr,__be16 sport,__be16 dport)161 u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
162 __be16 sport, __be16 dport)
163 {
164 u64 seq;
165 net_secret_init();
166 seq = siphash_3u32((__force u32)saddr, (__force u32)daddr,
167 (__force u32)sport << 16 | (__force u32)dport,
168 &net_secret);
169 seq += ktime_get_real_ns();
170 seq &= (1ull << 48) - 1;
171 return seq;
172 }
173 EXPORT_SYMBOL(secure_dccp_sequence_number);
174
175 #if IS_ENABLED(CONFIG_IPV6)
secure_dccpv6_sequence_number(__be32 * saddr,__be32 * daddr,__be16 sport,__be16 dport)176 u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
177 __be16 sport, __be16 dport)
178 {
179 const struct {
180 struct in6_addr saddr;
181 struct in6_addr daddr;
182 __be16 sport;
183 __be16 dport;
184 } __aligned(SIPHASH_ALIGNMENT) combined = {
185 .saddr = *(struct in6_addr *)saddr,
186 .daddr = *(struct in6_addr *)daddr,
187 .sport = sport,
188 .dport = dport
189 };
190 u64 seq;
191 net_secret_init();
192 seq = siphash(&combined, offsetofend(typeof(combined), dport),
193 &net_secret);
194 seq += ktime_get_real_ns();
195 seq &= (1ull << 48) - 1;
196 return seq;
197 }
198 EXPORT_SYMBOL(secure_dccpv6_sequence_number);
199 #endif
200 #endif
201