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