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TOMOYO Linux Cross Reference
Linux/net/core/secure_seq.c

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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 
 22 static siphash_key_t net_secret __read_mostly;
 23 static siphash_key_t ts_secret __read_mostly;
 24 
 25 static __always_inline void net_secret_init(void)
 26 {
 27         net_get_random_once(&net_secret, sizeof(net_secret));
 28 }
 29 
 30 static __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
 37 static 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)
 54 u32 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 }
 72 EXPORT_SYMBOL(secure_tcpv6_ts_off);
 73 
 74 u32 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 }
 95 EXPORT_SYMBOL(secure_tcpv6_seq);
 96 
 97 u32 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 }
113 EXPORT_SYMBOL(secure_ipv6_port_ephemeral);
114 #endif
115 
116 #ifdef CONFIG_INET
117 u32 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  */
132 u32 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 
144 u32 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 }
150 EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);
151 #endif
152 
153 #if IS_ENABLED(CONFIG_IP_DCCP)
154 u64 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 }
166 EXPORT_SYMBOL(secure_dccp_sequence_number);
167 
168 #if IS_ENABLED(CONFIG_IPV6)
169 u64 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 }
191 EXPORT_SYMBOL(secure_dccpv6_sequence_number);
192 #endif
193 #endif
194 

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