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 | |
27 | static __always_inline void net_secret_init(void) |
28 | { |
29 | net_get_random_once(&net_secret, sizeof(net_secret)); |
30 | } |
31 | |
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 |
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) |
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(data: &combined, offsetofend(typeof(combined), daddr), |
72 | key: &ts_secret); |
73 | } |
74 | EXPORT_SYMBOL(secure_tcpv6_ts_off); |
75 | |
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(data: &combined, offsetofend(typeof(combined), dport), |
94 | key: &net_secret); |
95 | return seq_scale(seq: hash); |
96 | } |
97 | EXPORT_SYMBOL(secure_tcpv6_seq); |
98 | |
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(data: &combined, offsetofend(typeof(combined), dport), |
115 | key: &net_secret); |
116 | } |
117 | EXPORT_SYMBOL(secure_ipv6_port_ephemeral); |
118 | #endif |
119 | |
120 | #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(a: (__force u32)saddr, b: (__force u32)daddr, |
128 | key: &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 | */ |
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(a: (__force u32)saddr, b: (__force u32)daddr, |
143 | c: (__force u32)sport << 16 | (__force u32)dport, |
144 | key: &net_secret); |
145 | return seq_scale(seq: hash); |
146 | } |
147 | EXPORT_SYMBOL_GPL(secure_tcp_seq); |
148 | |
149 | u64 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport) |
150 | { |
151 | net_secret_init(); |
152 | return siphash_4u32(a: (__force u32)saddr, b: (__force u32)daddr, |
153 | c: (__force u16)dport, |
154 | d: jiffies / EPHEMERAL_PORT_SHUFFLE_PERIOD, |
155 | key: &net_secret); |
156 | } |
157 | EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral); |
158 | #endif |
159 | |
160 | #if IS_ENABLED(CONFIG_IP_DCCP) |
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(a: (__force u32)saddr, b: (__force u32)daddr, |
167 | c: (__force u32)sport << 16 | (__force u32)dport, |
168 | key: &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) |
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(data: &combined, offsetofend(typeof(combined), dport), |
193 | key: &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 | |