blob: 5abc3692b9011b140816dc4ce6223e79e5defddb [file] [log] [blame]
Glenn Griffinc6aefaf2008-02-07 21:49:26 -08001/*
2 * IPv6 Syncookies implementation for the Linux kernel
3 *
4 * Authors:
5 * Glenn Griffin <ggriffin.kernel@gmail.com>
6 *
7 * Based on IPv4 implementation by Andi Kleen
8 * linux/net/ipv4/syncookies.c
9 *
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public License
12 * as published by the Free Software Foundation; either version
13 * 2 of the License, or (at your option) any later version.
14 *
15 */
16
17#include <linux/tcp.h>
18#include <linux/random.h>
Jason A. Donenfeldfe62d052017-01-08 13:54:03 +010019#include <linux/siphash.h>
Glenn Griffinc6aefaf2008-02-07 21:49:26 -080020#include <linux/kernel.h>
Eric Dumazet84b114b2017-05-05 06:56:54 -070021#include <net/secure_seq.h>
Glenn Griffinc6aefaf2008-02-07 21:49:26 -080022#include <net/ipv6.h>
23#include <net/tcp.h>
24
Glenn Griffinc6aefaf2008-02-07 21:49:26 -080025#define COOKIEBITS 24 /* Upper bits store count */
26#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
27
Jason A. Donenfeldfe62d052017-01-08 13:54:03 +010028static siphash_key_t syncookie6_secret[2] __read_mostly;
Hannes Frederic Sowab23a0022013-10-19 21:48:56 +020029
Florian Westphal08629352013-09-20 22:32:56 +020030/* RFC 2460, Section 8.3:
31 * [ipv6 tcp] MSS must be computed as the maximum packet size minus 60 [..]
32 *
33 * Due to IPV6_MIN_MTU=1280 the lowest possible MSS is 1220, which allows
34 * using higher values than ipv4 tcp syncookies.
35 * The other values are chosen based on ethernet (1500 and 9k MTU), plus
36 * one that accounts for common encap (PPPoe) overhead. Table must be sorted.
37 */
Glenn Griffinc6aefaf2008-02-07 21:49:26 -080038static __u16 const msstab[] = {
Florian Westphal08629352013-09-20 22:32:56 +020039 1280 - 60, /* IPV6_MIN_MTU - 60 */
Florian Westphal5918e2f2010-06-03 00:43:57 +000040 1480 - 60,
41 1500 - 60,
Florian Westphal5918e2f2010-06-03 00:43:57 +000042 9000 - 60,
Glenn Griffinc6aefaf2008-02-07 21:49:26 -080043};
Glenn Griffinc6aefaf2008-02-07 21:49:26 -080044
Jason A. Donenfeldfe62d052017-01-08 13:54:03 +010045static u32 cookie_hash(const struct in6_addr *saddr,
46 const struct in6_addr *daddr,
Glenn Griffinc6aefaf2008-02-07 21:49:26 -080047 __be16 sport, __be16 dport, u32 count, int c)
48{
Jason A. Donenfeldfe62d052017-01-08 13:54:03 +010049 const struct {
50 struct in6_addr saddr;
51 struct in6_addr daddr;
52 u32 count;
53 __be16 sport;
54 __be16 dport;
55 } __aligned(SIPHASH_ALIGNMENT) combined = {
56 .saddr = *saddr,
57 .daddr = *daddr,
58 .count = count,
59 .sport = sport,
60 .dport = dport
61 };
Hannes Frederic Sowab23a0022013-10-19 21:48:56 +020062
63 net_get_random_once(syncookie6_secret, sizeof(syncookie6_secret));
Jason A. Donenfeldfe62d052017-01-08 13:54:03 +010064 return siphash(&combined, offsetofend(typeof(combined), dport),
65 &syncookie6_secret[c]);
Glenn Griffinc6aefaf2008-02-07 21:49:26 -080066}
67
Eric Dumazetb71d1d42011-04-22 04:53:02 +000068static __u32 secure_tcp_syn_cookie(const struct in6_addr *saddr,
69 const struct in6_addr *daddr,
Glenn Griffinc6aefaf2008-02-07 21:49:26 -080070 __be16 sport, __be16 dport, __u32 sseq,
Florian Westphal8c27bd72013-09-20 22:32:55 +020071 __u32 data)
Glenn Griffinc6aefaf2008-02-07 21:49:26 -080072{
Florian Westphal8c27bd72013-09-20 22:32:55 +020073 u32 count = tcp_cookie_time();
Glenn Griffinc6aefaf2008-02-07 21:49:26 -080074 return (cookie_hash(saddr, daddr, sport, dport, 0, 0) +
75 sseq + (count << COOKIEBITS) +
76 ((cookie_hash(saddr, daddr, sport, dport, count, 1) + data)
77 & COOKIEMASK));
78}
79
Eric Dumazetb71d1d42011-04-22 04:53:02 +000080static __u32 check_tcp_syn_cookie(__u32 cookie, const struct in6_addr *saddr,
81 const struct in6_addr *daddr, __be16 sport,
Florian Westphal8c27bd72013-09-20 22:32:55 +020082 __be16 dport, __u32 sseq)
Glenn Griffinc6aefaf2008-02-07 21:49:26 -080083{
Florian Westphal8c27bd72013-09-20 22:32:55 +020084 __u32 diff, count = tcp_cookie_time();
Glenn Griffinc6aefaf2008-02-07 21:49:26 -080085
86 cookie -= cookie_hash(saddr, daddr, sport, dport, 0, 0) + sseq;
87
88 diff = (count - (cookie >> COOKIEBITS)) & ((__u32) -1 >> COOKIEBITS);
Florian Westphal8c27bd72013-09-20 22:32:55 +020089 if (diff >= MAX_SYNCOOKIE_AGE)
Glenn Griffinc6aefaf2008-02-07 21:49:26 -080090 return (__u32)-1;
91
92 return (cookie -
93 cookie_hash(saddr, daddr, sport, dport, count - diff, 1))
94 & COOKIEMASK;
95}
96
Patrick McHardy81eb6a12013-08-27 08:50:15 +020097u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
98 const struct tcphdr *th, __u16 *mssp)
Glenn Griffinc6aefaf2008-02-07 21:49:26 -080099{
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800100 int mssind;
101 const __u16 mss = *mssp;
102
Florian Westphal5918e2f2010-06-03 00:43:57 +0000103 for (mssind = ARRAY_SIZE(msstab) - 1; mssind ; mssind--)
104 if (mss >= msstab[mssind])
105 break;
106
107 *mssp = msstab[mssind];
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800108
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800109 return secure_tcp_syn_cookie(&iph->saddr, &iph->daddr, th->source,
Florian Westphal8c27bd72013-09-20 22:32:55 +0200110 th->dest, ntohl(th->seq), mssind);
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800111}
Patrick McHardy81eb6a12013-08-27 08:50:15 +0200112EXPORT_SYMBOL_GPL(__cookie_v6_init_sequence);
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800113
Eric Dumazet3f684b42015-09-29 07:42:49 -0700114__u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mssp)
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800115{
Eric Dumazetb71d1d42011-04-22 04:53:02 +0000116 const struct ipv6hdr *iph = ipv6_hdr(skb);
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800117 const struct tcphdr *th = tcp_hdr(skb);
Patrick McHardy81eb6a12013-08-27 08:50:15 +0200118
Patrick McHardy81eb6a12013-08-27 08:50:15 +0200119 return __cookie_v6_init_sequence(iph, th, mssp);
120}
121
122int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
123 __u32 cookie)
124{
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800125 __u32 seq = ntohl(th->seq) - 1;
126 __u32 mssind = check_tcp_syn_cookie(cookie, &iph->saddr, &iph->daddr,
Florian Westphal8c27bd72013-09-20 22:32:55 +0200127 th->source, th->dest, seq);
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800128
Florian Westphal5918e2f2010-06-03 00:43:57 +0000129 return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0;
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800130}
Patrick McHardy81eb6a12013-08-27 08:50:15 +0200131EXPORT_SYMBOL_GPL(__cookie_v6_check);
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800132
133struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
134{
William Allen Simpson4957faade2009-12-02 18:25:27 +0000135 struct tcp_options_received tcp_opt;
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800136 struct inet_request_sock *ireq;
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800137 struct tcp_request_sock *treq;
138 struct ipv6_pinfo *np = inet6_sk(sk);
139 struct tcp_sock *tp = tcp_sk(sk);
140 const struct tcphdr *th = tcp_hdr(skb);
141 __u32 cookie = ntohl(th->ack_seq) - 1;
142 struct sock *ret = sk;
143 struct request_sock *req;
144 int mss;
145 struct dst_entry *dst;
146 __u8 rcv_wscale;
Eric Dumazet84b114b2017-05-05 06:56:54 -0700147 u32 tsoff = 0;
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800148
Nikolay Borisov12ed8242016-02-03 09:46:51 +0200149 if (!sock_net(sk)->ipv4.sysctl_tcp_syncookies || !th->ack || th->rst)
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800150 goto out;
151
Florian Westphal646697b2014-10-30 02:55:38 +0100152 if (tcp_synq_no_recent_overflow(sk))
153 goto out;
154
155 mss = __cookie_v6_check(ipv6_hdr(skb), th, cookie);
156 if (mss == 0) {
Eric Dumazet02a1d6e2016-04-27 16:44:39 -0700157 __NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800158 goto out;
159 }
160
Eric Dumazet02a1d6e2016-04-27 16:44:39 -0700161 __NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV);
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800162
David S. Millerbb5b7c12009-12-15 20:56:42 -0800163 /* check for timestamp cookie support */
164 memset(&tcp_opt, 0, sizeof(tcp_opt));
Christoph Paasch1a2c6182013-03-17 08:23:34 +0000165 tcp_parse_options(skb, &tcp_opt, 0, NULL);
David S. Millerbb5b7c12009-12-15 20:56:42 -0800166
Eric Dumazet84b114b2017-05-05 06:56:54 -0700167 if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {
168 tsoff = secure_tcpv6_ts_off(ipv6_hdr(skb)->daddr.s6_addr32,
169 ipv6_hdr(skb)->saddr.s6_addr32);
170 tcp_opt.rcv_tsecr -= tsoff;
171 }
172
Florian Westphalf1673382014-11-03 17:35:02 +0100173 if (!cookie_timestamp_decode(&tcp_opt))
Florian Westphal8c763682010-06-16 14:42:15 -0700174 goto out;
David S. Millerbb5b7c12009-12-15 20:56:42 -0800175
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800176 ret = NULL;
Eric Dumazeta1a53442015-10-04 21:08:11 -0700177 req = inet_reqsk_alloc(&tcp6_request_sock_ops, sk, false);
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800178 if (!req)
179 goto out;
180
181 ireq = inet_rsk(req);
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800182 treq = tcp_rsk(req);
Eric Dumazet9439ce02015-03-17 18:32:29 -0700183 treq->tfo_listener = false;
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800184
Florian Westphal17305542008-08-03 18:13:44 -0700185 if (security_inet_conn_request(sk, skb, req))
186 goto out_free;
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800187
188 req->mss = mss;
Eric Dumazet634fb9792013-10-09 15:21:29 -0700189 ireq->ir_rmt_port = th->source;
Eric Dumazetb44084c2013-10-10 00:04:37 -0700190 ireq->ir_num = ntohs(th->dest);
Eric Dumazet634fb9792013-10-09 15:21:29 -0700191 ireq->ir_v6_rmt_addr = ipv6_hdr(skb)->saddr;
192 ireq->ir_v6_loc_addr = ipv6_hdr(skb)->daddr;
Eric Dumazeta2247722014-09-27 09:50:56 -0700193 if (ipv6_opt_accepted(sk, skb, &TCP_SKB_CB(skb)->header.h6) ||
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800194 np->rxopt.bits.rxinfo || np->rxopt.bits.rxoinfo ||
195 np->rxopt.bits.rxhlim || np->rxopt.bits.rxohlim) {
196 atomic_inc(&skb->users);
Eric Dumazet634fb9792013-10-09 15:21:29 -0700197 ireq->pktopts = skb;
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800198 }
199
David Ahern6dd9a142015-12-16 13:20:44 -0800200 ireq->ir_iif = inet_request_bound_dev_if(sk, skb);
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800201 /* So that link locals have meaning */
202 if (!sk->sk_bound_dev_if &&
Eric Dumazet634fb9792013-10-09 15:21:29 -0700203 ipv6_addr_type(&ireq->ir_v6_rmt_addr) & IPV6_ADDR_LINKLOCAL)
Eric Dumazet870c3152014-10-17 09:17:20 -0700204 ireq->ir_iif = tcp_v6_iif(skb);
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800205
Lorenzo Colitti84f39b02014-05-13 10:17:35 -0700206 ireq->ir_mark = inet_request_mark(sk, skb);
207
Eric Dumazete6c022a2012-10-27 23:16:46 +0000208 req->num_retrans = 0;
David S. Millerbb5b7c12009-12-15 20:56:42 -0800209 ireq->snd_wscale = tcp_opt.snd_wscale;
David S. Millerbb5b7c12009-12-15 20:56:42 -0800210 ireq->sack_ok = tcp_opt.sack_ok;
211 ireq->wscale_ok = tcp_opt.wscale_ok;
212 ireq->tstamp_ok = tcp_opt.saw_tstamp;
213 req->ts_recent = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
Yuchung Cheng0f1c28a2015-09-18 11:36:14 -0700214 treq->snt_synack.v64 = 0;
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800215 treq->rcv_isn = ntohl(th->seq) - 1;
216 treq->snt_isn = cookie;
Florian Westphal95a22ca2016-12-01 11:32:06 +0100217 treq->ts_off = 0;
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800218
219 /*
220 * We need to lookup the dst_entry to get the correct window size.
221 * This is taken from tcp_v6_syn_recv_sock. Somebody please enlighten
222 * me if there is a preferred way.
223 */
224 {
Arnaud Ebalard20c59de2010-06-01 21:35:01 +0000225 struct in6_addr *final_p, final;
David S. Miller4c9483b2011-03-12 16:22:43 -0500226 struct flowi6 fl6;
227 memset(&fl6, 0, sizeof(fl6));
228 fl6.flowi6_proto = IPPROTO_TCP;
Eric Dumazet634fb9792013-10-09 15:21:29 -0700229 fl6.daddr = ireq->ir_v6_rmt_addr;
Eric Dumazet45f6fad2015-11-29 19:37:57 -0800230 final_p = fl6_update_dst(&fl6, rcu_dereference(np->opt), &final);
Eric Dumazet634fb9792013-10-09 15:21:29 -0700231 fl6.saddr = ireq->ir_v6_loc_addr;
David Ahern6dd9a142015-12-16 13:20:44 -0800232 fl6.flowi6_oif = ireq->ir_iif;
Lorenzo Colitti84f39b02014-05-13 10:17:35 -0700233 fl6.flowi6_mark = ireq->ir_mark;
Eric Dumazet634fb9792013-10-09 15:21:29 -0700234 fl6.fl6_dport = ireq->ir_rmt_port;
David S. Miller1958b852011-03-12 16:36:19 -0500235 fl6.fl6_sport = inet_sk(sk)->inet_sport;
Lorenzo Colittie2d118a2016-11-04 02:23:43 +0900236 fl6.flowi6_uid = sk->sk_uid;
David S. Miller4c9483b2011-03-12 16:22:43 -0500237 security_req_classify_flow(req, flowi6_to_flowi(&fl6));
Florian Westphal17305542008-08-03 18:13:44 -0700238
Steffen Klassert0e0d44a2013-08-28 08:04:14 +0200239 dst = ip6_dst_lookup_flow(sk, &fl6, final_p);
David S. Miller68d0c6d2011-03-01 13:19:07 -0800240 if (IS_ERR(dst))
Florian Westphal17305542008-08-03 18:13:44 -0700241 goto out_free;
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800242 }
243
Eric Dumazeted53d0a2015-10-08 19:33:23 -0700244 req->rsk_window_clamp = tp->window_clamp ? :dst_metric(dst, RTAX_WINDOW);
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800245 tcp_select_initial_window(tcp_full_space(sk), req->mss,
Eric Dumazeted53d0a2015-10-08 19:33:23 -0700246 &req->rsk_rcv_wnd, &req->rsk_window_clamp,
laurent chavey31d12922009-12-15 11:15:28 +0000247 ireq->wscale_ok, &rcv_wscale,
248 dst_metric(dst, RTAX_INITRWND));
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800249
250 ireq->rcv_wscale = rcv_wscale;
Florian Westphalf7b3bec2014-11-03 17:35:03 +0100251 ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, sock_net(sk), dst);
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800252
Eric Dumazet84b114b2017-05-05 06:56:54 -0700253 ret = tcp_get_cookie_sock(sk, skb, req, dst, tsoff);
Florian Westphal17305542008-08-03 18:13:44 -0700254out:
255 return ret;
256out_free:
257 reqsk_free(req);
258 return NULL;
Glenn Griffinc6aefaf2008-02-07 21:49:26 -0800259}