[mirror_ubuntu-artful-kernel.git] / net / ipv6 / syncookies.c

/*
 *  IPv6 Syncookies implementation for the Linux kernel
 *
 *  Authors:
 *  Glenn Griffin	<ggriffin.kernel@gmail.com>
 *
 *  Based on IPv4 implementation by Andi Kleen
 *  linux/net/ipv4/syncookies.c
 *
 *	This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 *
 */

#include <linux/tcp.h>
#include <linux/random.h>
#include <linux/siphash.h>
#include <linux/kernel.h>
#include <net/secure_seq.h>
#include <net/ipv6.h>
#include <net/tcp.h>

#define COOKIEBITS 24	/* Upper bits store count */
#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)

static siphash_key_t syncookie6_secret[2] __read_mostly;

/* RFC 2460, Section 8.3:
 * [ipv6 tcp] MSS must be computed as the maximum packet size minus 60 [..]
 *
 * Due to IPV6_MIN_MTU=1280 the lowest possible MSS is 1220, which allows
 * using higher values than ipv4 tcp syncookies.
 * The other values are chosen based on ethernet (1500 and 9k MTU), plus
 * one that accounts for common encap (PPPoe) overhead. Table must be sorted.
 */
static __u16 const msstab[] = {
	1280 - 60, /* IPV6_MIN_MTU - 60 */
	1480 - 60,
	1500 - 60,
	9000 - 60,
};

static u32 cookie_hash(const struct in6_addr *saddr,
		       const struct in6_addr *daddr,
		       __be16 sport, __be16 dport, u32 count, int c)
{
	const struct {
		struct in6_addr saddr;
		struct in6_addr daddr;
		u32 count;
		__be16 sport;
		__be16 dport;
	} __aligned(SIPHASH_ALIGNMENT) combined = {
		.saddr = *saddr,
		.daddr = *daddr,
		.count = count,
		.sport = sport,
		.dport = dport
	};

	net_get_random_once(syncookie6_secret, sizeof(syncookie6_secret));
	return siphash(&combined, offsetofend(typeof(combined), dport),
		       &syncookie6_secret[c]);
}

static __u32 secure_tcp_syn_cookie(const struct in6_addr *saddr,
				   const struct in6_addr *daddr,
				   __be16 sport, __be16 dport, __u32 sseq,
				   __u32 data)
{
	u32 count = tcp_cookie_time();
	return (cookie_hash(saddr, daddr, sport, dport, 0, 0) +
		sseq + (count << COOKIEBITS) +
		((cookie_hash(saddr, daddr, sport, dport, count, 1) + data)
		& COOKIEMASK));
}

static __u32 check_tcp_syn_cookie(__u32 cookie, const struct in6_addr *saddr,
				  const struct in6_addr *daddr, __be16 sport,
				  __be16 dport, __u32 sseq)
{
	__u32 diff, count = tcp_cookie_time();

	cookie -= cookie_hash(saddr, daddr, sport, dport, 0, 0) + sseq;

	diff = (count - (cookie >> COOKIEBITS)) & ((__u32) -1 >> COOKIEBITS);
	if (diff >= MAX_SYNCOOKIE_AGE)
		return (__u32)-1;

	return (cookie -
		cookie_hash(saddr, daddr, sport, dport, count - diff, 1))
		& COOKIEMASK;
}

u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
			      const struct tcphdr *th, __u16 *mssp)
{
	int mssind;
	const __u16 mss = *mssp;

	for (mssind = ARRAY_SIZE(msstab) - 1; mssind ; mssind--)
		if (mss >= msstab[mssind])
			break;

	*mssp = msstab[mssind];

	return secure_tcp_syn_cookie(&iph->saddr, &iph->daddr, th->source,
				     th->dest, ntohl(th->seq), mssind);
}
EXPORT_SYMBOL_GPL(__cookie_v6_init_sequence);

__u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mssp)
{
	const struct ipv6hdr *iph = ipv6_hdr(skb);
	const struct tcphdr *th = tcp_hdr(skb);

	return __cookie_v6_init_sequence(iph, th, mssp);
}

int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
		      __u32 cookie)
{
	__u32 seq = ntohl(th->seq) - 1;
	__u32 mssind = check_tcp_syn_cookie(cookie, &iph->saddr, &iph->daddr,
					    th->source, th->dest, seq);

	return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0;
}
EXPORT_SYMBOL_GPL(__cookie_v6_check);

struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_options_received tcp_opt;
	struct inet_request_sock *ireq;
	struct tcp_request_sock *treq;
	struct ipv6_pinfo *np = inet6_sk(sk);
	struct tcp_sock *tp = tcp_sk(sk);
	const struct tcphdr *th = tcp_hdr(skb);
	__u32 cookie = ntohl(th->ack_seq) - 1;
	struct sock *ret = sk;
	struct request_sock *req;
	int mss;
	struct dst_entry *dst;
	__u8 rcv_wscale;
	u32 tsoff = 0;

	if (!sock_net(sk)->ipv4.sysctl_tcp_syncookies || !th->ack || th->rst)
		goto out;

	if (tcp_synq_no_recent_overflow(sk))
		goto out;

	mss = __cookie_v6_check(ipv6_hdr(skb), th, cookie);
	if (mss == 0) {
		__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
		goto out;
	}

	__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV);

	/* check for timestamp cookie support */
	memset(&tcp_opt, 0, sizeof(tcp_opt));
	tcp_parse_options(sock_net(sk), skb, &tcp_opt, 0, NULL);

	if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {
		tsoff = secure_tcpv6_ts_off(sock_net(sk),
					    ipv6_hdr(skb)->daddr.s6_addr32,
					    ipv6_hdr(skb)->saddr.s6_addr32);
		tcp_opt.rcv_tsecr -= tsoff;
	}

	if (!cookie_timestamp_decode(sock_net(sk), &tcp_opt))
		goto out;

	ret = NULL;
	req = inet_reqsk_alloc(&tcp6_request_sock_ops, sk, false);
	if (!req)
		goto out;

	ireq = inet_rsk(req);
	treq = tcp_rsk(req);
	treq->tfo_listener = false;

	if (security_inet_conn_request(sk, skb, req))
		goto out_free;

	req->mss = mss;
	ireq->ir_rmt_port = th->source;
	ireq->ir_num = ntohs(th->dest);
	ireq->ir_v6_rmt_addr = ipv6_hdr(skb)->saddr;
	ireq->ir_v6_loc_addr = ipv6_hdr(skb)->daddr;
	if (ipv6_opt_accepted(sk, skb, &TCP_SKB_CB(skb)->header.h6) ||
	    np->rxopt.bits.rxinfo || np->rxopt.bits.rxoinfo ||
	    np->rxopt.bits.rxhlim || np->rxopt.bits.rxohlim) {
		refcount_inc(&skb->users);
		ireq->pktopts = skb;
	}

	ireq->ir_iif = inet_request_bound_dev_if(sk, skb);
	/* So that link locals have meaning */
	if (!sk->sk_bound_dev_if &&
	    ipv6_addr_type(&ireq->ir_v6_rmt_addr) & IPV6_ADDR_LINKLOCAL)
		ireq->ir_iif = tcp_v6_iif(skb);

	ireq->ir_mark = inet_request_mark(sk, skb);

	req->num_retrans = 0;
	ireq->snd_wscale	= tcp_opt.snd_wscale;
	ireq->sack_ok		= tcp_opt.sack_ok;
	ireq->wscale_ok		= tcp_opt.wscale_ok;
	ireq->tstamp_ok		= tcp_opt.saw_tstamp;
	req->ts_recent		= tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
	treq->snt_synack	= 0;
	treq->rcv_isn = ntohl(th->seq) - 1;
	treq->snt_isn = cookie;
	treq->ts_off = 0;
	treq->txhash = net_tx_rndhash();

	/*
	 * We need to lookup the dst_entry to get the correct window size.
	 * This is taken from tcp_v6_syn_recv_sock.  Somebody please enlighten
	 * me if there is a preferred way.
	 */
	{
		struct in6_addr *final_p, final;
		struct flowi6 fl6;
		memset(&fl6, 0, sizeof(fl6));
		fl6.flowi6_proto = IPPROTO_TCP;
		fl6.daddr = ireq->ir_v6_rmt_addr;
		final_p = fl6_update_dst(&fl6, rcu_dereference(np->opt), &final);
		fl6.saddr = ireq->ir_v6_loc_addr;
		fl6.flowi6_oif = ireq->ir_iif;
		fl6.flowi6_mark = ireq->ir_mark;
		fl6.fl6_dport = ireq->ir_rmt_port;
		fl6.fl6_sport = inet_sk(sk)->inet_sport;
		fl6.flowi6_uid = sk->sk_uid;
		security_req_classify_flow(req, flowi6_to_flowi(&fl6));

		dst = ip6_dst_lookup_flow(sk, &fl6, final_p);
		if (IS_ERR(dst))
			goto out_free;
	}

	req->rsk_window_clamp = tp->window_clamp ? :dst_metric(dst, RTAX_WINDOW);
	tcp_select_initial_window(tcp_full_space(sk), req->mss,
				  &req->rsk_rcv_wnd, &req->rsk_window_clamp,
				  ireq->wscale_ok, &rcv_wscale,
				  dst_metric(dst, RTAX_INITRWND));

	ireq->rcv_wscale = rcv_wscale;
	ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, sock_net(sk), dst);

	ret = tcp_get_cookie_sock(sk, skb, req, dst, tsoff);
out:
	return ret;
out_free:
	reqsk_free(req);
	return NULL;
}
Commit	Line	Data
c6aefafb GG	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>
fe62d05b	19	#include <linux/siphash.h>
c6aefafb	20	#include <linux/kernel.h>
84b114b9	21	#include <net/secure_seq.h>
c6aefafb GG	22	#include <net/ipv6.h>
	23	#include <net/tcp.h>
	24
c6aefafb GG	25	#define COOKIEBITS 24 /* Upper bits store count */
	26	#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
	27
fe62d05b	28	static siphash_key_t syncookie6_secret[2] __read_mostly;
b23a002f	29
08629354 FW	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	*/
c6aefafb	38	static __u16 const msstab[] = {
08629354	39	1280 - 60, /* IPV6_MIN_MTU - 60 */
5918e2fb FW	40	1480 - 60,
5918e2fb FW	41	1500 - 60,
5918e2fb	42	9000 - 60,
c6aefafb	43	};
c6aefafb	44
fe62d05b JD	45	static u32 cookie_hash(const struct in6_addr *saddr,
fe62d05b JD	46	const struct in6_addr *daddr,
c6aefafb GG	47	__be16 sport, __be16 dport, u32 count, int c)
c6aefafb GG	48	{
fe62d05b JD	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	};
b23a002f HFS	62
b23a002f HFS	63	net_get_random_once(syncookie6_secret, sizeof(syncookie6_secret));
fe62d05b JD	64	return siphash(&combined, offsetofend(typeof(combined), dport),
fe62d05b JD	65	&syncookie6_secret[c]);
c6aefafb GG	66	}
c6aefafb GG	67
b71d1d42 ED	68	static __u32 secure_tcp_syn_cookie(const struct in6_addr *saddr,
b71d1d42 ED	69	const struct in6_addr *daddr,
c6aefafb	70	__be16 sport, __be16 dport, __u32 sseq,
8c27bd75	71	__u32 data)
c6aefafb	72	{
8c27bd75	73	u32 count = tcp_cookie_time();
c6aefafb GG	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
b71d1d42 ED	80	static __u32 check_tcp_syn_cookie(__u32 cookie, const struct in6_addr *saddr,
b71d1d42 ED	81	const struct in6_addr *daddr, __be16 sport,
8c27bd75	82	__be16 dport, __u32 sseq)
c6aefafb	83	{
8c27bd75	84	__u32 diff, count = tcp_cookie_time();
c6aefafb GG	85
	86	cookie -= cookie_hash(saddr, daddr, sport, dport, 0, 0) + sseq;
	87
	88	diff = (count - (cookie >> COOKIEBITS)) & ((__u32) -1 >> COOKIEBITS);
8c27bd75	89	if (diff >= MAX_SYNCOOKIE_AGE)
c6aefafb GG	90	return (__u32)-1;
	91
	92	return (cookie -
	93	cookie_hash(saddr, daddr, sport, dport, count - diff, 1))
	94	& COOKIEMASK;
	95	}
	96
81eb6a14 PM	97	u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
81eb6a14 PM	98	const struct tcphdr th, __u16 mssp)
c6aefafb	99	{
c6aefafb GG	100	int mssind;
	101	const __u16 mss = *mssp;
	102
5918e2fb FW	103	for (mssind = ARRAY_SIZE(msstab) - 1; mssind ; mssind--)
	104	if (mss >= msstab[mssind])
	105	break;
	106
	107	*mssp = msstab[mssind];
c6aefafb	108
c6aefafb	109	return secure_tcp_syn_cookie(&iph->saddr, &iph->daddr, th->source,
8c27bd75	110	th->dest, ntohl(th->seq), mssind);
c6aefafb	111	}
81eb6a14	112	EXPORT_SYMBOL_GPL(__cookie_v6_init_sequence);
c6aefafb	113
3f684b4b	114	__u32 cookie_v6_init_sequence(const struct sk_buff skb, __u16 mssp)
c6aefafb	115	{
b71d1d42	116	const struct ipv6hdr *iph = ipv6_hdr(skb);
c6aefafb	117	const struct tcphdr *th = tcp_hdr(skb);
81eb6a14	118
81eb6a14 PM	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	{
c6aefafb GG	125	__u32 seq = ntohl(th->seq) - 1;
c6aefafb GG	126	__u32 mssind = check_tcp_syn_cookie(cookie, &iph->saddr, &iph->daddr,
8c27bd75	127	th->source, th->dest, seq);
c6aefafb	128
5918e2fb	129	return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0;
c6aefafb	130	}
81eb6a14	131	EXPORT_SYMBOL_GPL(__cookie_v6_check);
c6aefafb GG	132
	133	struct sock cookie_v6_check(struct sock sk, struct sk_buff *skb)
	134	{
4957faad	135	struct tcp_options_received tcp_opt;
c6aefafb	136	struct inet_request_sock *ireq;
c6aefafb GG	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;
84b114b9	147	u32 tsoff = 0;
c6aefafb	148
12ed8244	149	if (!sock_net(sk)->ipv4.sysctl_tcp_syncookies \|\| !th->ack \|\| th->rst)
c6aefafb GG	150	goto out;
c6aefafb GG	151
646697b9 FW	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) {
02a1d6e7	157	__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
c6aefafb GG	158	goto out;
	159	}
	160
02a1d6e7	161	__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV);
c6aefafb	162
bb5b7c11 DM	163	/* check for timestamp cookie support */
bb5b7c11 DM	164	memset(&tcp_opt, 0, sizeof(tcp_opt));
eed29f17	165	tcp_parse_options(sock_net(sk), skb, &tcp_opt, 0, NULL);
bb5b7c11	166
84b114b9	167	if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {
5d2ed052 ED	168	tsoff = secure_tcpv6_ts_off(sock_net(sk),
5d2ed052 ED	169	ipv6_hdr(skb)->daddr.s6_addr32,
84b114b9 ED	170	ipv6_hdr(skb)->saddr.s6_addr32);
	171	tcp_opt.rcv_tsecr -= tsoff;
	172	}
	173
f9301034	174	if (!cookie_timestamp_decode(sock_net(sk), &tcp_opt))
8c763681	175	goto out;
bb5b7c11	176
c6aefafb	177	ret = NULL;
a1a5344d	178	req = inet_reqsk_alloc(&tcp6_request_sock_ops, sk, false);
c6aefafb GG	179	if (!req)
	180	goto out;
	181
	182	ireq = inet_rsk(req);
c6aefafb	183	treq = tcp_rsk(req);
9439ce00	184	treq->tfo_listener = false;
c6aefafb	185
1730554f FW	186	if (security_inet_conn_request(sk, skb, req))
1730554f FW	187	goto out_free;
c6aefafb GG	188
c6aefafb GG	189	req->mss = mss;
634fb979	190	ireq->ir_rmt_port = th->source;
b44084c2	191	ireq->ir_num = ntohs(th->dest);
634fb979 ED	192	ireq->ir_v6_rmt_addr = ipv6_hdr(skb)->saddr;
634fb979 ED	193	ireq->ir_v6_loc_addr = ipv6_hdr(skb)->daddr;
a224772d	194	if (ipv6_opt_accepted(sk, skb, &TCP_SKB_CB(skb)->header.h6) \|\|
c6aefafb GG	195	np->rxopt.bits.rxinfo \|\| np->rxopt.bits.rxoinfo \|\|
c6aefafb GG	196	np->rxopt.bits.rxhlim \|\| np->rxopt.bits.rxohlim) {
63354797	197	refcount_inc(&skb->users);
634fb979	198	ireq->pktopts = skb;
c6aefafb GG	199	}
c6aefafb GG	200
6dd9a14e	201	ireq->ir_iif = inet_request_bound_dev_if(sk, skb);
c6aefafb GG	202	/* So that link locals have meaning */
c6aefafb GG	203	if (!sk->sk_bound_dev_if &&
634fb979	204	ipv6_addr_type(&ireq->ir_v6_rmt_addr) & IPV6_ADDR_LINKLOCAL)
870c3151	205	ireq->ir_iif = tcp_v6_iif(skb);
c6aefafb	206
84f39b08 LC	207	ireq->ir_mark = inet_request_mark(sk, skb);
84f39b08 LC	208
e6c022a4	209	req->num_retrans = 0;
bb5b7c11	210	ireq->snd_wscale = tcp_opt.snd_wscale;
bb5b7c11 DM	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;
9a568de4	215	treq->snt_synack = 0;
c6aefafb GG	216	treq->rcv_isn = ntohl(th->seq) - 1;
c6aefafb GG	217	treq->snt_isn = cookie;
95a22cae	218	treq->ts_off = 0;
18bcf290	219	treq->txhash = net_tx_rndhash();
c6aefafb GG	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	{
20c59de2	227	struct in6_addr *final_p, final;
4c9483b2 DM	228	struct flowi6 fl6;
	229	memset(&fl6, 0, sizeof(fl6));
	230	fl6.flowi6_proto = IPPROTO_TCP;
634fb979	231	fl6.daddr = ireq->ir_v6_rmt_addr;
45f6fad8	232	final_p = fl6_update_dst(&fl6, rcu_dereference(np->opt), &final);
634fb979	233	fl6.saddr = ireq->ir_v6_loc_addr;
6dd9a14e	234	fl6.flowi6_oif = ireq->ir_iif;
84f39b08	235	fl6.flowi6_mark = ireq->ir_mark;
634fb979	236	fl6.fl6_dport = ireq->ir_rmt_port;
1958b856	237	fl6.fl6_sport = inet_sk(sk)->inet_sport;
e2d118a1	238	fl6.flowi6_uid = sk->sk_uid;
4c9483b2 DM	239	security_req_classify_flow(req, flowi6_to_flowi(&fl6));
4c9483b2 DM	240
0e0d44ab	241	dst = ip6_dst_lookup_flow(sk, &fl6, final_p);
68d0c6d3	242	if (IS_ERR(dst))
1730554f	243	goto out_free;
c6aefafb GG	244	}
c6aefafb GG	245
ed53d0ab	246	req->rsk_window_clamp = tp->window_clamp ? :dst_metric(dst, RTAX_WINDOW);
c6aefafb	247	tcp_select_initial_window(tcp_full_space(sk), req->mss,
ed53d0ab	248	&req->rsk_rcv_wnd, &req->rsk_window_clamp,
31d12926	249	ireq->wscale_ok, &rcv_wscale,
31d12926	250	dst_metric(dst, RTAX_INITRWND));
c6aefafb GG	251
c6aefafb GG	252	ireq->rcv_wscale = rcv_wscale;
f7b3bec6	253	ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, sock_net(sk), dst);
c6aefafb	254
84b114b9	255	ret = tcp_get_cookie_sock(sk, skb, req, dst, tsoff);
1730554f FW	256	out:
	257	return ret;
	258	out_free:
	259	reqsk_free(req);
	260	return NULL;
c6aefafb	261	}