~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/net/ipv6/syncookies.c

Version: ~ [ linux-5.13-rc7 ] ~ [ linux-5.12.12 ] ~ [ linux-5.11.22 ] ~ [ linux-5.10.45 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.127 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.195 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.237 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.273 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.273 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.18.140 ] ~ [ linux-3.16.85 ] ~ [ linux-3.14.79 ] ~ [ linux-3.12.74 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /*
  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>
 19 #include <linux/siphash.h>
 20 #include <linux/kernel.h>
 21 #include <net/secure_seq.h>
 22 #include <net/ipv6.h>
 23 #include <net/tcp.h>
 24 
 25 #define COOKIEBITS 24   /* Upper bits store count */
 26 #define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
 27 
 28 static siphash_key_t syncookie6_secret[2] __read_mostly;
 29 
 30 /* 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  */
 38 static __u16 const msstab[] = {
 39         1280 - 60, /* IPV6_MIN_MTU - 60 */
 40         1480 - 60,
 41         1500 - 60,
 42         9000 - 60,
 43 };
 44 
 45 static u32 cookie_hash(const struct in6_addr *saddr,
 46                        const struct in6_addr *daddr,
 47                        __be16 sport, __be16 dport, u32 count, int c)
 48 {
 49         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         };
 62 
 63         net_get_random_once(syncookie6_secret, sizeof(syncookie6_secret));
 64         return siphash(&combined, offsetofend(typeof(combined), dport),
 65                        &syncookie6_secret[c]);
 66 }
 67 
 68 static __u32 secure_tcp_syn_cookie(const struct in6_addr *saddr,
 69                                    const struct in6_addr *daddr,
 70                                    __be16 sport, __be16 dport, __u32 sseq,
 71                                    __u32 data)
 72 {
 73         u32 count = tcp_cookie_time();
 74         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 
 80 static __u32 check_tcp_syn_cookie(__u32 cookie, const struct in6_addr *saddr,
 81                                   const struct in6_addr *daddr, __be16 sport,
 82                                   __be16 dport, __u32 sseq)
 83 {
 84         __u32 diff, count = tcp_cookie_time();
 85 
 86         cookie -= cookie_hash(saddr, daddr, sport, dport, 0, 0) + sseq;
 87 
 88         diff = (count - (cookie >> COOKIEBITS)) & ((__u32) -1 >> COOKIEBITS);
 89         if (diff >= MAX_SYNCOOKIE_AGE)
 90                 return (__u32)-1;
 91 
 92         return (cookie -
 93                 cookie_hash(saddr, daddr, sport, dport, count - diff, 1))
 94                 & COOKIEMASK;
 95 }
 96 
 97 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
 98                               const struct tcphdr *th, __u16 *mssp)
 99 {
100         int mssind;
101         const __u16 mss = *mssp;
102 
103         for (mssind = ARRAY_SIZE(msstab) - 1; mssind ; mssind--)
104                 if (mss >= msstab[mssind])
105                         break;
106 
107         *mssp = msstab[mssind];
108 
109         return secure_tcp_syn_cookie(&iph->saddr, &iph->daddr, th->source,
110                                      th->dest, ntohl(th->seq), mssind);
111 }
112 EXPORT_SYMBOL_GPL(__cookie_v6_init_sequence);
113 
114 __u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mssp)
115 {
116         const struct ipv6hdr *iph = ipv6_hdr(skb);
117         const struct tcphdr *th = tcp_hdr(skb);
118 
119         return __cookie_v6_init_sequence(iph, th, mssp);
120 }
121 
122 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
123                       __u32 cookie)
124 {
125         __u32 seq = ntohl(th->seq) - 1;
126         __u32 mssind = check_tcp_syn_cookie(cookie, &iph->saddr, &iph->daddr,
127                                             th->source, th->dest, seq);
128 
129         return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0;
130 }
131 EXPORT_SYMBOL_GPL(__cookie_v6_check);
132 
133 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
134 {
135         struct tcp_options_received tcp_opt;
136         struct inet_request_sock *ireq;
137         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;
147         u32 tsoff = 0;
148 
149         if (!sock_net(sk)->ipv4.sysctl_tcp_syncookies || !th->ack || th->rst)
150                 goto out;
151 
152         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) {
157                 __NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
158                 goto out;
159         }
160 
161         __NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV);
162 
163         /* check for timestamp cookie support */
164         memset(&tcp_opt, 0, sizeof(tcp_opt));
165         tcp_parse_options(sock_net(sk), skb, &tcp_opt, 0, NULL);
166 
167         if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {
168                 tsoff = secure_tcpv6_ts_off(sock_net(sk),
169                                             ipv6_hdr(skb)->daddr.s6_addr32,
170                                             ipv6_hdr(skb)->saddr.s6_addr32);
171                 tcp_opt.rcv_tsecr -= tsoff;
172         }
173 
174         if (!cookie_timestamp_decode(sock_net(sk), &tcp_opt))
175                 goto out;
176 
177         ret = NULL;
178         req = inet_reqsk_alloc(&tcp6_request_sock_ops, sk, false);
179         if (!req)
180                 goto out;
181 
182         ireq = inet_rsk(req);
183         treq = tcp_rsk(req);
184         treq->tfo_listener = false;
185 
186         if (security_inet_conn_request(sk, skb, req))
187                 goto out_free;
188 
189         req->mss = mss;
190         ireq->ir_rmt_port = th->source;
191         ireq->ir_num = ntohs(th->dest);
192         ireq->ir_v6_rmt_addr = ipv6_hdr(skb)->saddr;
193         ireq->ir_v6_loc_addr = ipv6_hdr(skb)->daddr;
194         if (ipv6_opt_accepted(sk, skb, &TCP_SKB_CB(skb)->header.h6) ||
195             np->rxopt.bits.rxinfo || np->rxopt.bits.rxoinfo ||
196             np->rxopt.bits.rxhlim || np->rxopt.bits.rxohlim) {
197                 refcount_inc(&skb->users);
198                 ireq->pktopts = skb;
199         }
200 
201         ireq->ir_iif = inet_request_bound_dev_if(sk, skb);
202         /* So that link locals have meaning */
203         if (!sk->sk_bound_dev_if &&
204             ipv6_addr_type(&ireq->ir_v6_rmt_addr) & IPV6_ADDR_LINKLOCAL)
205                 ireq->ir_iif = tcp_v6_iif(skb);
206 
207         ireq->ir_mark = inet_request_mark(sk, skb);
208 
209         req->num_retrans = 0;
210         ireq->snd_wscale        = tcp_opt.snd_wscale;
211         ireq->sack_ok           = tcp_opt.sack_ok;
212         ireq->wscale_ok         = tcp_opt.wscale_ok;
213         ireq->tstamp_ok         = tcp_opt.saw_tstamp;
214         req->ts_recent          = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
215         treq->snt_synack        = 0;
216         treq->rcv_isn = ntohl(th->seq) - 1;
217         treq->snt_isn = cookie;
218         treq->ts_off = 0;
219         treq->txhash = net_tx_rndhash();
220 
221         /*
222          * We need to lookup the dst_entry to get the correct window size.
223          * This is taken from tcp_v6_syn_recv_sock.  Somebody please enlighten
224          * me if there is a preferred way.
225          */
226         {
227                 struct in6_addr *final_p, final;
228                 struct flowi6 fl6;
229                 memset(&fl6, 0, sizeof(fl6));
230                 fl6.flowi6_proto = IPPROTO_TCP;
231                 fl6.daddr = ireq->ir_v6_rmt_addr;
232                 final_p = fl6_update_dst(&fl6, rcu_dereference(np->opt), &final);
233                 fl6.saddr = ireq->ir_v6_loc_addr;
234                 fl6.flowi6_oif = ireq->ir_iif;
235                 fl6.flowi6_mark = ireq->ir_mark;
236                 fl6.fl6_dport = ireq->ir_rmt_port;
237                 fl6.fl6_sport = inet_sk(sk)->inet_sport;
238                 fl6.flowi6_uid = sk->sk_uid;
239                 security_req_classify_flow(req, flowi6_to_flowi(&fl6));
240 
241                 dst = ip6_dst_lookup_flow(sk, &fl6, final_p);
242                 if (IS_ERR(dst))
243                         goto out_free;
244         }
245 
246         req->rsk_window_clamp = tp->window_clamp ? :dst_metric(dst, RTAX_WINDOW);
247         tcp_select_initial_window(tcp_full_space(sk), req->mss,
248                                   &req->rsk_rcv_wnd, &req->rsk_window_clamp,
249                                   ireq->wscale_ok, &rcv_wscale,
250                                   dst_metric(dst, RTAX_INITRWND));
251 
252         ireq->rcv_wscale = rcv_wscale;
253         ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, sock_net(sk), dst);
254 
255         ret = tcp_get_cookie_sock(sk, skb, req, dst, tsoff);
256 out:
257         return ret;
258 out_free:
259         reqsk_free(req);
260         return NULL;
261 }
262 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp