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165573e41f
This reverts28ee1b746f("secure_seq: downgrade to per-host timestamp offsets") tcp_tw_recycle went away in 2017. Zhouyan Deng reported off-path TCP source port leakage via SYN cookie side-channel that can be fixed in multiple ways. One of them is to bring back TCP ports in TS offset randomization. As a bonus, we perform a single siphash() computation to provide both an ISN and a TS offset. Fixes:28ee1b746f("secure_seq: downgrade to per-host timestamp offsets") Reported-by: Zhouyan Deng <dengzhouyan_nwpu@163.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com> Acked-by: Florian Westphal <fw@strlen.de> Link: https://patch.msgid.link/20260302205527.1982836-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
136 lines
3.6 KiB
C
136 lines
3.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
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*/
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/cache.h>
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#include <linux/random.h>
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#include <linux/hrtimer.h>
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#include <linux/ktime.h>
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#include <linux/string.h>
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#include <linux/net.h>
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#include <linux/siphash.h>
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#include <net/secure_seq.h>
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#if IS_ENABLED(CONFIG_IPV6) || IS_ENABLED(CONFIG_INET)
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#include <linux/in6.h>
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#include <net/tcp.h>
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static siphash_aligned_key_t net_secret;
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#define EPHEMERAL_PORT_SHUFFLE_PERIOD (10 * HZ)
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static __always_inline void net_secret_init(void)
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{
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net_get_random_once(&net_secret, sizeof(net_secret));
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}
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#endif
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#ifdef CONFIG_INET
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static u32 seq_scale(u32 seq)
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{
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/*
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* As close as possible to RFC 793, which
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* suggests using a 250 kHz clock.
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* Further reading shows this assumes 2 Mb/s networks.
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* For 10 Mb/s Ethernet, a 1 MHz clock is appropriate.
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* For 10 Gb/s Ethernet, a 1 GHz clock should be ok, but
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* we also need to limit the resolution so that the u32 seq
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* overlaps less than one time per MSL (2 minutes).
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* Choosing a clock of 64 ns period is OK. (period of 274 s)
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*/
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return seq + (ktime_get_real_ns() >> 6);
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}
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#endif
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#if IS_ENABLED(CONFIG_IPV6)
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union tcp_seq_and_ts_off
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secure_tcpv6_seq_and_ts_off(const struct net *net, const __be32 *saddr,
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const __be32 *daddr, __be16 sport, __be16 dport)
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{
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const struct {
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struct in6_addr saddr;
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struct in6_addr daddr;
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__be16 sport;
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__be16 dport;
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} __aligned(SIPHASH_ALIGNMENT) combined = {
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.saddr = *(struct in6_addr *)saddr,
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.daddr = *(struct in6_addr *)daddr,
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.sport = sport,
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.dport = dport
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};
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union tcp_seq_and_ts_off st;
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net_secret_init();
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st.hash64 = siphash(&combined, offsetofend(typeof(combined), dport),
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&net_secret);
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if (READ_ONCE(net->ipv4.sysctl_tcp_timestamps) != 1)
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st.ts_off = 0;
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st.seq = seq_scale(st.seq);
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return st;
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}
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EXPORT_SYMBOL(secure_tcpv6_seq_and_ts_off);
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u64 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
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__be16 dport)
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{
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const struct {
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struct in6_addr saddr;
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struct in6_addr daddr;
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unsigned int timeseed;
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__be16 dport;
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} __aligned(SIPHASH_ALIGNMENT) combined = {
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.saddr = *(struct in6_addr *)saddr,
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.daddr = *(struct in6_addr *)daddr,
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.timeseed = jiffies / EPHEMERAL_PORT_SHUFFLE_PERIOD,
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.dport = dport,
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};
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net_secret_init();
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return siphash(&combined, offsetofend(typeof(combined), dport),
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&net_secret);
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}
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EXPORT_SYMBOL(secure_ipv6_port_ephemeral);
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#endif
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#ifdef CONFIG_INET
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/* secure_tcp_seq_and_tsoff(a, b, 0, d) == secure_ipv4_port_ephemeral(a, b, d),
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* but fortunately, `sport' cannot be 0 in any circumstances. If this changes,
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* it would be easy enough to have the former function use siphash_4u32, passing
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* the arguments as separate u32.
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*/
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union tcp_seq_and_ts_off
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secure_tcp_seq_and_ts_off(const struct net *net, __be32 saddr, __be32 daddr,
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__be16 sport, __be16 dport)
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{
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u32 ports = (__force u32)sport << 16 | (__force u32)dport;
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union tcp_seq_and_ts_off st;
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net_secret_init();
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st.hash64 = siphash_3u32((__force u32)saddr, (__force u32)daddr,
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ports, &net_secret);
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if (READ_ONCE(net->ipv4.sysctl_tcp_timestamps) != 1)
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st.ts_off = 0;
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st.seq = seq_scale(st.seq);
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return st;
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}
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EXPORT_SYMBOL_GPL(secure_tcp_seq_and_ts_off);
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u64 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
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{
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net_secret_init();
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return siphash_4u32((__force u32)saddr, (__force u32)daddr,
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(__force u16)dport,
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jiffies / EPHEMERAL_PORT_SHUFFLE_PERIOD,
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&net_secret);
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}
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EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);
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#endif
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