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17#include <linux/tcp.h>
18#include <linux/random.h>
19#include <linux/cryptohash.h>
20#include <linux/kernel.h>
21#include <net/ipv6.h>
22#include <net/tcp.h>
23
24#define COOKIEBITS 24
25#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
26
27
28static __u16 const msstab[] = {
29 64,
30 512,
31 536,
32 1280 - 60,
33 1480 - 60,
34 1500 - 60,
35 4460 - 60,
36 9000 - 60,
37};
38
39
40
41
42
43
44
45#define COUNTER_TRIES 4
46
47static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb,
48 struct request_sock *req,
49 struct dst_entry *dst)
50{
51 struct inet_connection_sock *icsk = inet_csk(sk);
52 struct sock *child;
53
54 child = icsk->icsk_af_ops->syn_recv_sock(sk, skb, req, dst);
55 if (child)
56 inet_csk_reqsk_queue_add(sk, req, child);
57 else
58 reqsk_free(req);
59
60 return child;
61}
62
63static DEFINE_PER_CPU(__u32 [16 + 5 + SHA_WORKSPACE_WORDS],
64 ipv6_cookie_scratch);
65
66static u32 cookie_hash(const struct in6_addr *saddr, const struct in6_addr *daddr,
67 __be16 sport, __be16 dport, u32 count, int c)
68{
69 __u32 *tmp = __get_cpu_var(ipv6_cookie_scratch);
70
71
72
73
74
75
76 memcpy(tmp + 10, syncookie_secret[c], 44);
77 memcpy(tmp, saddr, 16);
78 memcpy(tmp + 4, daddr, 16);
79 tmp[8] = ((__force u32)sport << 16) + (__force u32)dport;
80 tmp[9] = count;
81 sha_transform(tmp + 16, (__u8 *)tmp, tmp + 16 + 5);
82
83 return tmp[17];
84}
85
86static __u32 secure_tcp_syn_cookie(const struct in6_addr *saddr,
87 const struct in6_addr *daddr,
88 __be16 sport, __be16 dport, __u32 sseq,
89 __u32 count, __u32 data)
90{
91 return (cookie_hash(saddr, daddr, sport, dport, 0, 0) +
92 sseq + (count << COOKIEBITS) +
93 ((cookie_hash(saddr, daddr, sport, dport, count, 1) + data)
94 & COOKIEMASK));
95}
96
97static __u32 check_tcp_syn_cookie(__u32 cookie, const struct in6_addr *saddr,
98 const struct in6_addr *daddr, __be16 sport,
99 __be16 dport, __u32 sseq, __u32 count,
100 __u32 maxdiff)
101{
102 __u32 diff;
103
104 cookie -= cookie_hash(saddr, daddr, sport, dport, 0, 0) + sseq;
105
106 diff = (count - (cookie >> COOKIEBITS)) & ((__u32) -1 >> COOKIEBITS);
107 if (diff >= maxdiff)
108 return (__u32)-1;
109
110 return (cookie -
111 cookie_hash(saddr, daddr, sport, dport, count - diff, 1))
112 & COOKIEMASK;
113}
114
115__u32 cookie_v6_init_sequence(struct sock *sk, const struct sk_buff *skb, __u16 *mssp)
116{
117 const struct ipv6hdr *iph = ipv6_hdr(skb);
118 const struct tcphdr *th = tcp_hdr(skb);
119 int mssind;
120 const __u16 mss = *mssp;
121
122 tcp_synq_overflow(sk);
123
124 for (mssind = ARRAY_SIZE(msstab) - 1; mssind ; mssind--)
125 if (mss >= msstab[mssind])
126 break;
127
128 *mssp = msstab[mssind];
129
130 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
131
132 return secure_tcp_syn_cookie(&iph->saddr, &iph->daddr, th->source,
133 th->dest, ntohl(th->seq),
134 jiffies / (HZ * 60), mssind);
135}
136
137static inline int cookie_check(const struct sk_buff *skb, __u32 cookie)
138{
139 const struct ipv6hdr *iph = ipv6_hdr(skb);
140 const struct tcphdr *th = tcp_hdr(skb);
141 __u32 seq = ntohl(th->seq) - 1;
142 __u32 mssind = check_tcp_syn_cookie(cookie, &iph->saddr, &iph->daddr,
143 th->source, th->dest, seq,
144 jiffies / (HZ * 60), COUNTER_TRIES);
145
146 return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0;
147}
148
149struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
150{
151 struct tcp_options_received tcp_opt;
152 struct inet_request_sock *ireq;
153 struct inet6_request_sock *ireq6;
154 struct tcp_request_sock *treq;
155 struct ipv6_pinfo *np = inet6_sk(sk);
156 struct tcp_sock *tp = tcp_sk(sk);
157 const struct tcphdr *th = tcp_hdr(skb);
158 __u32 cookie = ntohl(th->ack_seq) - 1;
159 struct sock *ret = sk;
160 struct request_sock *req;
161 int mss;
162 struct dst_entry *dst;
163 __u8 rcv_wscale;
164 bool ecn_ok = false;
165
166 if (!sysctl_tcp_syncookies || !th->ack || th->rst)
167 goto out;
168
169 if (tcp_synq_no_recent_overflow(sk) ||
170 (mss = cookie_check(skb, cookie)) == 0) {
171 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
172 goto out;
173 }
174
175 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV);
176
177
178 memset(&tcp_opt, 0, sizeof(tcp_opt));
179 tcp_parse_options(skb, &tcp_opt, 0, NULL);
180
181 if (!cookie_check_timestamp(&tcp_opt, sock_net(sk), &ecn_ok))
182 goto out;
183
184 ret = NULL;
185 req = inet6_reqsk_alloc(&tcp6_request_sock_ops);
186 if (!req)
187 goto out;
188
189 ireq = inet_rsk(req);
190 ireq6 = inet6_rsk(req);
191 treq = tcp_rsk(req);
192 treq->listener = NULL;
193
194 if (security_inet_conn_request(sk, skb, req))
195 goto out_free;
196
197 req->mss = mss;
198 ireq->rmt_port = th->source;
199 ireq->loc_port = th->dest;
200 ireq6->rmt_addr = ipv6_hdr(skb)->saddr;
201 ireq6->loc_addr = ipv6_hdr(skb)->daddr;
202 if (ipv6_opt_accepted(sk, skb) ||
203 np->rxopt.bits.rxinfo || np->rxopt.bits.rxoinfo ||
204 np->rxopt.bits.rxhlim || np->rxopt.bits.rxohlim) {
205 atomic_inc(&skb->users);
206 ireq6->pktopts = skb;
207 }
208
209 ireq6->iif = sk->sk_bound_dev_if;
210
211 if (!sk->sk_bound_dev_if &&
212 ipv6_addr_type(&ireq6->rmt_addr) & IPV6_ADDR_LINKLOCAL)
213 ireq6->iif = inet6_iif(skb);
214
215 req->expires = 0UL;
216 req->num_retrans = 0;
217 ireq->ecn_ok = ecn_ok;
218 ireq->snd_wscale = tcp_opt.snd_wscale;
219 ireq->sack_ok = tcp_opt.sack_ok;
220 ireq->wscale_ok = tcp_opt.wscale_ok;
221 ireq->tstamp_ok = tcp_opt.saw_tstamp;
222 req->ts_recent = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
223 treq->snt_synack = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsecr : 0;
224 treq->rcv_isn = ntohl(th->seq) - 1;
225 treq->snt_isn = cookie;
226
227
228
229
230
231
232 {
233 struct in6_addr *final_p, final;
234 struct flowi6 fl6;
235 memset(&fl6, 0, sizeof(fl6));
236 fl6.flowi6_proto = IPPROTO_TCP;
237 fl6.daddr = ireq6->rmt_addr;
238 final_p = fl6_update_dst(&fl6, np->opt, &final);
239 fl6.saddr = ireq6->loc_addr;
240 fl6.flowi6_oif = sk->sk_bound_dev_if;
241 fl6.flowi6_mark = sk->sk_mark;
242 fl6.fl6_dport = inet_rsk(req)->rmt_port;
243 fl6.fl6_sport = inet_sk(sk)->inet_sport;
244 security_req_classify_flow(req, flowi6_to_flowi(&fl6));
245
246 dst = ip6_dst_lookup_flow(sk, &fl6, final_p, false);
247 if (IS_ERR(dst))
248 goto out_free;
249 }
250
251 req->window_clamp = tp->window_clamp ? :dst_metric(dst, RTAX_WINDOW);
252 tcp_select_initial_window(tcp_full_space(sk), req->mss,
253 &req->rcv_wnd, &req->window_clamp,
254 ireq->wscale_ok, &rcv_wscale,
255 dst_metric(dst, RTAX_INITRWND));
256
257 ireq->rcv_wscale = rcv_wscale;
258
259 ret = get_cookie_sock(sk, skb, req, dst);
260out:
261 return ret;
262out_free:
263 reqsk_free(req);
264 return NULL;
265}
266
267