From 28ee1b746f493b7c62347d714f58fbf4f70df4f0 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Fri, 24 Mar 2017 19:42:37 +0100 Subject: 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 Cc: Eric Dumazet Cc: Neal Cardwell Cc: Yuchung Cheng Reported-by: Yvan Vanrossomme Fixes: 95a22caee396c ("tcp: randomize tcp timestamp offsets for each connection") Signed-off-by: Florian Westphal Signed-off-by: David S. Miller --- net/core/secure_seq.c | 31 +++++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-) (limited to 'net/core/secure_seq.c') 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 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); } -- cgit v1.2.3-59-g8ed1b