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
17static u32 net_secret[NET_SECRET_SIZE] ____cacheline_aligned;
18
19static __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
26static 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}
63EXPORT_SYMBOL(secure_tcpv6_sequence_number);
64
65u32 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}
84EXPORT_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
105u32 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}
119EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);
120#endif
121
122#if IS_ENABLED(CONFIG_IP_DCCP)
123u64 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}
143EXPORT_SYMBOL(secure_dccp_sequence_number);
144
145#if IS_ENABLED(CONFIG_IPV6)
146u64 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}
171EXPORT_SYMBOL(secure_dccpv6_sequence_number);
172#endif
173#endif
174