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Linux/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_to_ns(ktime_get_real()) >> 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_to_ns(ktime_get_real());
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_to_ns(ktime_get_real());
167         seq &= (1ull << 48) - 1;
168 
169         return seq;
170 }
171 EXPORT_SYMBOL(secure_dccpv6_sequence_number);
172 #endif
173 #endif
174 

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