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1/*
2 * Copyright (C) 2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
3 */
4
5#include <linux/kernel.h>
6#include <linux/init.h>
7#include <linux/cryptohash.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
22static siphash_key_t net_secret __read_mostly;
23static siphash_key_t ts_secret __read_mostly;
24
25static __always_inline void net_secret_init(void)
26{
27 net_get_random_once(&net_secret, sizeof(net_secret));
28}
29
30static __always_inline void ts_secret_init(void)
31{
32 net_get_random_once(&ts_secret, sizeof(ts_secret));
33}
34#endif
35
36#ifdef CONFIG_INET
37static u32 seq_scale(u32 seq)
38{
39 /*
40 * As close as possible to RFC 793, which
41 * suggests using a 250 kHz clock.
42 * Further reading shows this assumes 2 Mb/s networks.
43 * For 10 Mb/s Ethernet, a 1 MHz clock is appropriate.
44 * For 10 Gb/s Ethernet, a 1 GHz clock should be ok, but
45 * we also need to limit the resolution so that the u32 seq
46 * overlaps less than one time per MSL (2 minutes).
47 * Choosing a clock of 64 ns period is OK. (period of 274 s)
48 */
49 return seq + (ktime_get_real_ns() >> 6);
50}
51#endif
52
53#if IS_ENABLED(CONFIG_IPV6)
54u32 secure_tcpv6_ts_off(const struct net *net,
55 const __be32 *saddr, const __be32 *daddr)
56{
57 const struct {
58 struct in6_addr saddr;
59 struct in6_addr daddr;
60 } __aligned(SIPHASH_ALIGNMENT) combined = {
61 .saddr = *(struct in6_addr *)saddr,
62 .daddr = *(struct in6_addr *)daddr,
63 };
64
65 if (net->ipv4.sysctl_tcp_timestamps != 1)
66 return 0;
67
68 ts_secret_init();
69 return siphash(&combined, offsetofend(typeof(combined), daddr),
70 &ts_secret);
71}
72EXPORT_SYMBOL(secure_tcpv6_ts_off);
73
74u32 secure_tcpv6_seq(const __be32 *saddr, const __be32 *daddr,
75 __be16 sport, __be16 dport)
76{
77 const struct {
78 struct in6_addr saddr;
79 struct in6_addr daddr;
80 __be16 sport;
81 __be16 dport;
82 } __aligned(SIPHASH_ALIGNMENT) combined = {
83 .saddr = *(struct in6_addr *)saddr,
84 .daddr = *(struct in6_addr *)daddr,
85 .sport = sport,
86 .dport = dport
87 };
88 u32 hash;
89
90 net_secret_init();
91 hash = siphash(&combined, offsetofend(typeof(combined), dport),
92 &net_secret);
93 return seq_scale(hash);
94}
95EXPORT_SYMBOL(secure_tcpv6_seq);
96
97u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
98 __be16 dport)
99{
100 const struct {
101 struct in6_addr saddr;
102 struct in6_addr daddr;
103 __be16 dport;
104 } __aligned(SIPHASH_ALIGNMENT) combined = {
105 .saddr = *(struct in6_addr *)saddr,
106 .daddr = *(struct in6_addr *)daddr,
107 .dport = dport
108 };
109 net_secret_init();
110 return siphash(&combined, offsetofend(typeof(combined), dport),
111 &net_secret);
112}
113EXPORT_SYMBOL(secure_ipv6_port_ephemeral);
114#endif
115
116#ifdef CONFIG_INET
117u32 secure_tcp_ts_off(const struct net *net, __be32 saddr, __be32 daddr)
118{
119 if (net->ipv4.sysctl_tcp_timestamps != 1)
120 return 0;
121
122 ts_secret_init();
123 return siphash_2u32((__force u32)saddr, (__force u32)daddr,
124 &ts_secret);
125}
126
127/* secure_tcp_seq_and_tsoff(a, b, 0, d) == secure_ipv4_port_ephemeral(a, b, d),
128 * but fortunately, `sport' cannot be 0 in any circumstances. If this changes,
129 * it would be easy enough to have the former function use siphash_4u32, passing
130 * the arguments as separate u32.
131 */
132u32 secure_tcp_seq(__be32 saddr, __be32 daddr,
133 __be16 sport, __be16 dport)
134{
135 u32 hash;
136
137 net_secret_init();
138 hash = siphash_3u32((__force u32)saddr, (__force u32)daddr,
139 (__force u32)sport << 16 | (__force u32)dport,
140 &net_secret);
141 return seq_scale(hash);
142}
143
144u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
145{
146 net_secret_init();
147 return siphash_3u32((__force u32)saddr, (__force u32)daddr,
148 (__force u16)dport, &net_secret);
149}
150EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);
151#endif
152
153#if IS_ENABLED(CONFIG_IP_DCCP)
154u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
155 __be16 sport, __be16 dport)
156{
157 u64 seq;
158 net_secret_init();
159 seq = siphash_3u32((__force u32)saddr, (__force u32)daddr,
160 (__force u32)sport << 16 | (__force u32)dport,
161 &net_secret);
162 seq += ktime_get_real_ns();
163 seq &= (1ull << 48) - 1;
164 return seq;
165}
166EXPORT_SYMBOL(secure_dccp_sequence_number);
167
168#if IS_ENABLED(CONFIG_IPV6)
169u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
170 __be16 sport, __be16 dport)
171{
172 const struct {
173 struct in6_addr saddr;
174 struct in6_addr daddr;
175 __be16 sport;
176 __be16 dport;
177 } __aligned(SIPHASH_ALIGNMENT) combined = {
178 .saddr = *(struct in6_addr *)saddr,
179 .daddr = *(struct in6_addr *)daddr,
180 .sport = sport,
181 .dport = dport
182 };
183 u64 seq;
184 net_secret_init();
185 seq = siphash(&combined, offsetofend(typeof(combined), dport),
186 &net_secret);
187 seq += ktime_get_real_ns();
188 seq &= (1ull << 48) - 1;
189 return seq;
190}
191EXPORT_SYMBOL(secure_dccpv6_sequence_number);
192#endif
193#endif
1#include <linux/kernel.h>
2#include <linux/init.h>
3#include <linux/cryptohash.h>
4#include <linux/module.h>
5#include <linux/cache.h>
6#include <linux/random.h>
7#include <linux/hrtimer.h>
8#include <linux/ktime.h>
9#include <linux/string.h>
10#include <linux/net.h>
11
12#include <net/secure_seq.h>
13
14#if IS_ENABLED(CONFIG_IPV6) || IS_ENABLED(CONFIG_INET)
15#define NET_SECRET_SIZE (MD5_MESSAGE_BYTES / 4)
16
17static u32 net_secret[NET_SECRET_SIZE] ____cacheline_aligned;
18
19static __always_inline void net_secret_init(void)
20{
21 net_get_random_once(net_secret, sizeof(net_secret));
22}
23#endif
24
25#ifdef CONFIG_INET
26static u32 seq_scale(u32 seq)
27{
28 /*
29 * As close as possible to RFC 793, which
30 * suggests using a 250 kHz clock.
31 * Further reading shows this assumes 2 Mb/s networks.
32 * For 10 Mb/s Ethernet, a 1 MHz clock is appropriate.
33 * For 10 Gb/s Ethernet, a 1 GHz clock should be ok, but
34 * we also need to limit the resolution so that the u32 seq
35 * overlaps less than one time per MSL (2 minutes).
36 * Choosing a clock of 64 ns period is OK. (period of 274 s)
37 */
38 return seq + (ktime_get_real_ns() >> 6);
39}
40#endif
41
42#if IS_ENABLED(CONFIG_IPV6)
43__u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
44 __be16 sport, __be16 dport)
45{
46 u32 secret[MD5_MESSAGE_BYTES / 4];
47 u32 hash[MD5_DIGEST_WORDS];
48 u32 i;
49
50 net_secret_init();
51 memcpy(hash, saddr, 16);
52 for (i = 0; i < 4; i++)
53 secret[i] = net_secret[i] + (__force u32)daddr[i];
54 secret[4] = net_secret[4] +
55 (((__force u16)sport << 16) + (__force u16)dport);
56 for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
57 secret[i] = net_secret[i];
58
59 md5_transform(hash, secret);
60
61 return seq_scale(hash[0]);
62}
63EXPORT_SYMBOL(secure_tcpv6_sequence_number);
64
65u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
66 __be16 dport)
67{
68 u32 secret[MD5_MESSAGE_BYTES / 4];
69 u32 hash[MD5_DIGEST_WORDS];
70 u32 i;
71
72 net_secret_init();
73 memcpy(hash, saddr, 16);
74 for (i = 0; i < 4; i++)
75 secret[i] = net_secret[i] + (__force u32) daddr[i];
76 secret[4] = net_secret[4] + (__force u32)dport;
77 for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
78 secret[i] = net_secret[i];
79
80 md5_transform(hash, secret);
81
82 return hash[0];
83}
84EXPORT_SYMBOL(secure_ipv6_port_ephemeral);
85#endif
86
87#ifdef CONFIG_INET
88
89__u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
90 __be16 sport, __be16 dport)
91{
92 u32 hash[MD5_DIGEST_WORDS];
93
94 net_secret_init();
95 hash[0] = (__force u32)saddr;
96 hash[1] = (__force u32)daddr;
97 hash[2] = ((__force u16)sport << 16) + (__force u16)dport;
98 hash[3] = net_secret[15];
99
100 md5_transform(hash, net_secret);
101
102 return seq_scale(hash[0]);
103}
104
105u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
106{
107 u32 hash[MD5_DIGEST_WORDS];
108
109 net_secret_init();
110 hash[0] = (__force u32)saddr;
111 hash[1] = (__force u32)daddr;
112 hash[2] = (__force u32)dport ^ net_secret[14];
113 hash[3] = net_secret[15];
114
115 md5_transform(hash, net_secret);
116
117 return hash[0];
118}
119EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);
120#endif
121
122#if IS_ENABLED(CONFIG_IP_DCCP)
123u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
124 __be16 sport, __be16 dport)
125{
126 u32 hash[MD5_DIGEST_WORDS];
127 u64 seq;
128
129 net_secret_init();
130 hash[0] = (__force u32)saddr;
131 hash[1] = (__force u32)daddr;
132 hash[2] = ((__force u16)sport << 16) + (__force u16)dport;
133 hash[3] = net_secret[15];
134
135 md5_transform(hash, net_secret);
136
137 seq = hash[0] | (((u64)hash[1]) << 32);
138 seq += ktime_get_real_ns();
139 seq &= (1ull << 48) - 1;
140
141 return seq;
142}
143EXPORT_SYMBOL(secure_dccp_sequence_number);
144
145#if IS_ENABLED(CONFIG_IPV6)
146u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
147 __be16 sport, __be16 dport)
148{
149 u32 secret[MD5_MESSAGE_BYTES / 4];
150 u32 hash[MD5_DIGEST_WORDS];
151 u64 seq;
152 u32 i;
153
154 net_secret_init();
155 memcpy(hash, saddr, 16);
156 for (i = 0; i < 4; i++)
157 secret[i] = net_secret[i] + (__force u32)daddr[i];
158 secret[4] = net_secret[4] +
159 (((__force u16)sport << 16) + (__force u16)dport);
160 for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
161 secret[i] = net_secret[i];
162
163 md5_transform(hash, secret);
164
165 seq = hash[0] | (((u64)hash[1]) << 32);
166 seq += ktime_get_real_ns();
167 seq &= (1ull << 48) - 1;
168
169 return seq;
170}
171EXPORT_SYMBOL(secure_dccpv6_sequence_number);
172#endif
173#endif