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