| 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 |