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