xref: /openbmc/linux/net/core/secure_seq.c (revision 3666f666)
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