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authorFlorian Westphal <fw@strlen.de>2017-03-24 19:42:37 +0100
committerDavid S. Miller <davem@davemloft.net>2017-03-24 19:27:44 -0700
commit28ee1b746f493b7c62347d714f58fbf4f70df4f0 (patch)
tree852380c08234ff831bcf3177a21bcbeba0329b1f /net/core/secure_seq.c
parent95f255211396958c718aef8c45e3923b5211ea7b (diff)
secure_seq: downgrade to per-host timestamp offsets
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: 95a22caee396c ("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>
Diffstat (limited to 'net/core/secure_seq.c')
-rw-r--r--net/core/secure_seq.c31
1 files changed, 29 insertions, 2 deletions
diff --git a/net/core/secure_seq.c b/net/core/secure_seq.c
index 758f140b6bed..d28da7d363f1 100644
--- a/net/core/secure_seq.c
+++ b/net/core/secure_seq.c
@@ -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);
}