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secure_seq: downgrade to per-host timestamp offsets

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Unfortunately too many devices (not under our control) use tcp_tw_recycle=1,
which depends on timestamps being identical of the same saddr.

Although tcp_tw_recycle got removed in net-next we can't make
such end hosts disappear so downgrade to per-host timestamp offsets.

Cc: Soheil Hassas Yeganeh <soheil@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Reported-by: Yvan Vanrossomme <yvan@vanrossomme.net>
Fixes: 95a22caee3 ("tcp: randomize tcp timestamp offsets for each connection")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Westphal 2017-03-24 19:42:37 +01:00 committed by David S. Miller
parent 95f2552113
commit 28ee1b746f
1 changed files with 29 additions and 2 deletions
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31
net/core/secure_seq.c
View file

@ -20,9 +20,11 @@
#include <net/tcp.h>
static siphash_key_t net_secret __read_mostly;
static siphash_key_t ts_secret __read_mostly;
static __always_inline void net_secret_init(void)
{
net_get_random_once(&ts_secret, sizeof(ts_secret));
net_get_random_once(&net_secret, sizeof(net_secret));
}
#endif
@ -45,6 +47,23 @@ static u32 seq_scale(u32 seq)
#endif
#if IS_ENABLED(CONFIG_IPV6)
static u32 secure_tcpv6_ts_off(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 (sysctl_tcp_timestamps != 1)
return 0;
return siphash(&combined, offsetofend(typeof(combined), daddr),
&ts_secret);
}
u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
__be16 sport, __be16 dport, u32 *tsoff)
{
@ -63,7 +82,7 @@ u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
net_secret_init();
hash = siphash(&combined, offsetofend(typeof(combined), dport),
&net_secret);
*tsoff = sysctl_tcp_timestamps == 1 ? (hash >> 32) : 0;
*tsoff = secure_tcpv6_ts_off(saddr, daddr);
return seq_scale(hash);
}
EXPORT_SYMBOL(secure_tcpv6_sequence_number);
@ -88,6 +107,14 @@ EXPORT_SYMBOL(secure_ipv6_port_ephemeral);
#endif
#ifdef CONFIG_INET
static u32 secure_tcp_ts_off(__be32 saddr, __be32 daddr)
{
if (sysctl_tcp_timestamps != 1)
return 0;
return siphash_2u32((__force u32)saddr, (__force u32)daddr,
&ts_secret);
}
/* secure_tcp_sequence_number(a, b, 0, d) == secure_ipv4_port_ephemeral(a, b, d),
* but fortunately, `sport' cannot be 0 in any circumstances. If this changes,
@ -103,7 +130,7 @@ u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
hash = siphash_3u32((__force u32)saddr, (__force u32)daddr,
(__force u32)sport << 16 | (__force u32)dport,
&net_secret);
*tsoff = sysctl_tcp_timestamps == 1 ? (hash >> 32) : 0;
*tsoff = secure_tcp_ts_off(saddr, daddr);
return seq_scale(hash);
}