net/core/secure_seq.c

   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
  11 #include <net/secure_seq.h>
  12
  13 #define NET_SECRET_SIZE (MD5_MESSAGE_BYTES / 4)
  14
  15 static u32 net_secret[NET_SECRET_SIZE] ____cacheline_aligned;
  16
  17 static void net_secret_init(void)
  18 {
  19         u32 tmp;
  20         int i;
  21
  22         if (likely(net_secret[0]))
  23                 return;
  24
  25         for (i = NET_SECRET_SIZE; i > 0;) {
  26                 do {
  27                         get_random_bytes(&tmp, sizeof(tmp));
  28                 } while (!tmp);
  29                 cmpxchg(&net_secret[--i], 0, tmp);
  30         }
  31 }
  32
  33 #ifdef CONFIG_INET
  34 static u32 seq_scale(u32 seq)
  35 {
  36         /*
  37          *      As close as possible to RFC 793, which
  38          *      suggests using a 250 kHz clock.
  39          *      Further reading shows this assumes 2 Mb/s networks.
  40          *      For 10 Mb/s Ethernet, a 1 MHz clock is appropriate.
  41          *      For 10 Gb/s Ethernet, a 1 GHz clock should be ok, but
  42          *      we also need to limit the resolution so that the u32 seq
  43          *      overlaps less than one time per MSL (2 minutes).
  44          *      Choosing a clock of 64 ns period is OK. (period of 274 s)
  45          */
  46         return seq + (ktime_to_ns(ktime_get_real()) >> 6);
  47 }
  48 #endif
  49
  50 #if IS_ENABLED(CONFIG_IPV6)
  51 __u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
  52                                    __be16 sport, __be16 dport)
  53 {
  54         u32 secret[MD5_MESSAGE_BYTES / 4];
  55         u32 hash[MD5_DIGEST_WORDS];
  56         u32 i;
  57
  58         net_secret_init();
  59         memcpy(hash, saddr, 16);
  60         for (i = 0; i < 4; i++)
  61                 secret[i] = net_secret[i] + (__force u32)daddr[i];
  62         secret[4] = net_secret[4] +
  63                 (((__force u16)sport << 16) + (__force u16)dport);
  64         for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
  65                 secret[i] = net_secret[i];
  66
  67         md5_transform(hash, secret);
  68
  69         return seq_scale(hash[0]);
  70 }
  71 EXPORT_SYMBOL(secure_tcpv6_sequence_number);
  72
  73 u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
  74                                __be16 dport)
  75 {
  76         u32 secret[MD5_MESSAGE_BYTES / 4];
  77         u32 hash[MD5_DIGEST_WORDS];
  78         u32 i;
  79
  80         net_secret_init();
  81         memcpy(hash, saddr, 16);
  82         for (i = 0; i < 4; i++)
  83                 secret[i] = net_secret[i] + (__force u32) daddr[i];
  84         secret[4] = net_secret[4] + (__force u32)dport;
  85         for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
  86                 secret[i] = net_secret[i];
  87
  88         md5_transform(hash, secret);
  89
  90         return hash[0];
  91 }
  92 EXPORT_SYMBOL(secure_ipv6_port_ephemeral);
  93 #endif
  94
  95 #ifdef CONFIG_INET
  96 __u32 secure_ip_id(__be32 daddr)
  97 {
  98         u32 hash[MD5_DIGEST_WORDS];
  99
 100         net_secret_init();
 101         hash[0] = (__force __u32) daddr;
 102         hash[1] = net_secret[13];
 103         hash[2] = net_secret[14];
 104         hash[3] = net_secret[15];
 105
 106         md5_transform(hash, net_secret);
 107
 108         return hash[0];
 109 }
 110
 111 __u32 secure_ipv6_id(const __be32 daddr[4])
 112 {
 113         __u32 hash[4];
 114
 115         net_secret_init();
 116         memcpy(hash, daddr, 16);
 117         md5_transform(hash, net_secret);
 118
 119         return hash[0];
 120 }
 121
 122 __u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
 123                                  __be16 sport, __be16 dport)
 124 {
 125         u32 hash[MD5_DIGEST_WORDS];
 126
 127         net_secret_init();
 128         hash[0] = (__force u32)saddr;
 129         hash[1] = (__force u32)daddr;
 130         hash[2] = ((__force u16)sport << 16) + (__force u16)dport;
 131         hash[3] = net_secret[15];
 132
 133         md5_transform(hash, net_secret);
 134
 135         return seq_scale(hash[0]);
 136 }
 137
 138 u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
 139 {
 140         u32 hash[MD5_DIGEST_WORDS];
 141
 142         net_secret_init();
 143         hash[0] = (__force u32)saddr;
 144         hash[1] = (__force u32)daddr;
 145         hash[2] = (__force u32)dport ^ net_secret[14];
 146         hash[3] = net_secret[15];
 147
 148         md5_transform(hash, net_secret);
 149
 150         return hash[0];
 151 }
 152 EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);
 153 #endif
 154
 155 #if IS_ENABLED(CONFIG_IP_DCCP)
 156 u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
 157                                 __be16 sport, __be16 dport)
 158 {
 159         u32 hash[MD5_DIGEST_WORDS];
 160         u64 seq;
 161
 162         net_secret_init();
 163         hash[0] = (__force u32)saddr;
 164         hash[1] = (__force u32)daddr;
 165         hash[2] = ((__force u16)sport << 16) + (__force u16)dport;
 166         hash[3] = net_secret[15];
 167
 168         md5_transform(hash, net_secret);
 169
 170         seq = hash[0] | (((u64)hash[1]) << 32);
 171         seq += ktime_to_ns(ktime_get_real());
 172         seq &= (1ull << 48) - 1;
 173
 174         return seq;
 175 }
 176 EXPORT_SYMBOL(secure_dccp_sequence_number);
 177
 178 #if IS_ENABLED(CONFIG_IPV6)
 179 u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
 180                                   __be16 sport, __be16 dport)
 181 {
 182         u32 secret[MD5_MESSAGE_BYTES / 4];
 183         u32 hash[MD5_DIGEST_WORDS];
 184         u64 seq;
 185         u32 i;
 186
 187         net_secret_init();
 188         memcpy(hash, saddr, 16);
 189         for (i = 0; i < 4; i++)
 190                 secret[i] = net_secret[i] + daddr[i];
 191         secret[4] = net_secret[4] +
 192                 (((__force u16)sport << 16) + (__force u16)dport);
 193         for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
 194                 secret[i] = net_secret[i];
 195
 196         md5_transform(hash, secret);
 197
 198         seq = hash[0] | (((u64)hash[1]) << 32);
 199         seq += ktime_to_ns(ktime_get_real());
 200         seq &= (1ull << 48) - 1;
 201
 202         return seq;
 203 }
 204 EXPORT_SYMBOL(secure_dccpv6_sequence_number);
 205 #endif
 206 #endif