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/*
* Copyright (C) 2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/cryptohash.h>
#include <linux/module.h>
#include <linux/cache.h>
#include <linux/random.h>
#include <linux/hrtimer.h>
#include <linux/ktime.h>
#include <linux/string.h>
#include <linux/net.h>
#include <linux/siphash.h>
#include <net/secure_seq.h>
#if IS_ENABLED(CONFIG_IPV6) || IS_ENABLED(CONFIG_INET)
#include <linux/in6.h>
#include <net/tcp.h>
static siphash_key_t net_secret __read_mostly;
static siphash_key_t ts_secret __read_mostly;
#define EPHEMERAL_PORT_SHUFFLE_PERIOD (10 * HZ)
static __always_inline void net_secret_init(void)
{
net_get_random_once(&net_secret, sizeof(net_secret));
}
static __always_inline void ts_secret_init(void)
{
net_get_random_once(&ts_secret, sizeof(ts_secret));
}
#endif
#ifdef CONFIG_INET
static u32 seq_scale(u32 seq)
{
/*
* As close as possible to RFC 793, which
* suggests using a 250 kHz clock.
* Further reading shows this assumes 2 Mb/s networks.
* For 10 Mb/s Ethernet, a 1 MHz clock is appropriate.
* For 10 Gb/s Ethernet, a 1 GHz clock should be ok, but
* we also need to limit the resolution so that the u32 seq
* overlaps less than one time per MSL (2 minutes).
* Choosing a clock of 64 ns period is OK. (period of 274 s)
*/
return seq + (ktime_get_real_ns() >> 6);
}
#endif
#if IS_ENABLED(CONFIG_IPV6)
u32 secure_tcpv6_ts_off(const struct net *net,
const __be32 *saddr, const __be32 *daddr)
{
const struct {
struct in6_addr saddr;
struct in6_addr daddr;
} __aligned(SIPHASH_ALIGNMENT) combined = {
.saddr = *(struct in6_addr *)saddr,
.daddr = *(struct in6_addr *)daddr,
};
if (net->ipv4.sysctl_tcp_timestamps != 1)
return 0;
ts_secret_init();
return siphash(&combined, offsetofend(typeof(combined), daddr),
&ts_secret);
}
EXPORT_SYMBOL(secure_tcpv6_ts_off);
u32 secure_tcpv6_seq(const __be32 *saddr, const __be32 *daddr,
__be16 sport, __be16 dport)
{
const struct {
struct in6_addr saddr;
struct in6_addr daddr;
__be16 sport;
__be16 dport;
} __aligned(SIPHASH_ALIGNMENT) combined = {
.saddr = *(struct in6_addr *)saddr,
.daddr = *(struct in6_addr *)daddr,
.sport = sport,
.dport = dport
};
u32 hash;
net_secret_init();
hash = siphash(&combined, offsetofend(typeof(combined), dport),
&net_secret);
return seq_scale(hash);
}
EXPORT_SYMBOL(secure_tcpv6_seq);
u64 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
__be16 dport)
{
const struct {
struct in6_addr saddr;
struct in6_addr daddr;
unsigned int timeseed;
__be16 dport;
} __aligned(SIPHASH_ALIGNMENT) combined = {
.saddr = *(struct in6_addr *)saddr,
.daddr = *(struct in6_addr *)daddr,
.timeseed = jiffies / EPHEMERAL_PORT_SHUFFLE_PERIOD,
.dport = dport,
};
net_secret_init();
return siphash(&combined, offsetofend(typeof(combined), dport),
&net_secret);
}
EXPORT_SYMBOL(secure_ipv6_port_ephemeral);
#endif
#ifdef CONFIG_INET
u32 secure_tcp_ts_off(const struct net *net, __be32 saddr, __be32 daddr)
{
if (net->ipv4.sysctl_tcp_timestamps != 1)
return 0;
ts_secret_init();
return siphash_2u32((__force u32)saddr, (__force u32)daddr,
&ts_secret);
}
/* secure_tcp_seq_and_tsoff(a, b, 0, d) == secure_ipv4_port_ephemeral(a, b, d),
* but fortunately, `sport' cannot be 0 in any circumstances. If this changes,
* it would be easy enough to have the former function use siphash_4u32, passing
* the arguments as separate u32.
*/
u32 secure_tcp_seq(__be32 saddr, __be32 daddr,
__be16 sport, __be16 dport)
{
u32 hash;
net_secret_init();
hash = siphash_3u32((__force u32)saddr, (__force u32)daddr,
(__force u32)sport << 16 | (__force u32)dport,
&net_secret);
return seq_scale(hash);
}
EXPORT_SYMBOL_GPL(secure_tcp_seq);
u64 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
{
net_secret_init();
return siphash_4u32((__force u32)saddr, (__force u32)daddr,
(__force u16)dport,
jiffies / EPHEMERAL_PORT_SHUFFLE_PERIOD,
&net_secret);
}
EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);
#endif
#if IS_ENABLED(CONFIG_IP_DCCP)
u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
__be16 sport, __be16 dport)
{
u64 seq;
net_secret_init();
seq = siphash_3u32((__force u32)saddr, (__force u32)daddr,
(__force u32)sport << 16 | (__force u32)dport,
&net_secret);
seq += ktime_get_real_ns();
seq &= (1ull << 48) - 1;
return seq;
}
EXPORT_SYMBOL(secure_dccp_sequence_number);
#if IS_ENABLED(CONFIG_IPV6)
u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
__be16 sport, __be16 dport)
{
const struct {
struct in6_addr saddr;
struct in6_addr daddr;
__be16 sport;
__be16 dport;
} __aligned(SIPHASH_ALIGNMENT) combined = {
.saddr = *(struct in6_addr *)saddr,
.daddr = *(struct in6_addr *)daddr,
.sport = sport,
.dport = dport
};
u64 seq;
net_secret_init();
seq = siphash(&combined, offsetofend(typeof(combined), dport),
&net_secret);
seq += ktime_get_real_ns();
seq &= (1ull << 48) - 1;
return seq;
}
EXPORT_SYMBOL(secure_dccpv6_sequence_number);
#endif
#endif
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