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