[net-next-2.6.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/cryptohash.h>
#include <linux/kernel.h>
#include <net/ipv6.h>
#include <net/tcp.h>

extern int sysctl_tcp_syncookies;
extern __u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];

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

/* Table must be sorted. */
static __u16 const msstab[] = {
	64,
	512,
	536,
	1280 - 60,
	1480 - 60,
	1500 - 60,
	4460 - 60,
	9000 - 60,
};

/*
 * This (misnamed) value is the age of syncookie which is permitted.
 * Its ideal value should be dependent on TCP_TIMEOUT_INIT and
 * sysctl_tcp_retries1. It's a rather complicated formula (exponential
 * backoff) to compute at runtime so it's currently hardcoded here.
 */
#define COUNTER_TRIES 4

static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb,
					   struct request_sock *req,
					   struct dst_entry *dst)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct sock *child;

	child = icsk->icsk_af_ops->syn_recv_sock(sk, skb, req, dst);
	if (child)
		inet_csk_reqsk_queue_add(sk, req, child);
	else
		reqsk_free(req);

	return child;
}

static DEFINE_PER_CPU(__u32 [16 + 5 + SHA_WORKSPACE_WORDS],
		      ipv6_cookie_scratch);

static u32 cookie_hash(struct in6_addr *saddr, struct in6_addr *daddr,
		       __be16 sport, __be16 dport, u32 count, int c)
{
	__u32 *tmp = __get_cpu_var(ipv6_cookie_scratch);

	/*
	 * we have 320 bits of information to hash, copy in the remaining
	 * 192 bits required for sha_transform, from the syncookie_secret
	 * and overwrite the digest with the secret
	 */
	memcpy(tmp + 10, syncookie_secret[c], 44);
	memcpy(tmp, saddr, 16);
	memcpy(tmp + 4, daddr, 16);
	tmp[8] = ((__force u32)sport << 16) + (__force u32)dport;
	tmp[9] = count;
	sha_transform(tmp + 16, (__u8 *)tmp, tmp + 16 + 5);

	return tmp[17];
}

static __u32 secure_tcp_syn_cookie(struct in6_addr *saddr, struct in6_addr *daddr,
				   __be16 sport, __be16 dport, __u32 sseq,
				   __u32 count, __u32 data)
{
	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, struct in6_addr *saddr,
				  struct in6_addr *daddr, __be16 sport,
				  __be16 dport, __u32 sseq, __u32 count,
				  __u32 maxdiff)
{
	__u32 diff;

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

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

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

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

	tcp_synq_overflow(sk);

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

	*mssp = msstab[mssind];

	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);

	return secure_tcp_syn_cookie(&iph->saddr, &iph->daddr, th->source,
				     th->dest, ntohl(th->seq),
				     jiffies / (HZ * 60), mssind);
}

static inline int cookie_check(struct sk_buff *skb, __u32 cookie)
{
	struct ipv6hdr *iph = ipv6_hdr(skb);
	const struct tcphdr *th = tcp_hdr(skb);
	__u32 seq = ntohl(th->seq) - 1;
	__u32 mssind = check_tcp_syn_cookie(cookie, &iph->saddr, &iph->daddr,
					    th->source, th->dest, seq,
					    jiffies / (HZ * 60), COUNTER_TRIES);

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

struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_options_received tcp_opt;
	u8 *hash_location;
	struct inet_request_sock *ireq;
	struct inet6_request_sock *ireq6;
	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;
	bool ecn_ok;

	if (!sysctl_tcp_syncookies || !th->ack || th->rst)
		goto out;

	if (tcp_synq_no_recent_overflow(sk) ||
		(mss = cookie_check(skb, cookie)) == 0) {
		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
		goto out;
	}

	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV);

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

	if (!cookie_check_timestamp(&tcp_opt, &ecn_ok))
		goto out;

	ret = NULL;
	req = inet6_reqsk_alloc(&tcp6_request_sock_ops);
	if (!req)
		goto out;

	ireq = inet_rsk(req);
	ireq6 = inet6_rsk(req);
	treq = tcp_rsk(req);

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

	req->mss = mss;
	ireq->rmt_port = th->source;
	ireq->loc_port = th->dest;
	ipv6_addr_copy(&ireq6->rmt_addr, &ipv6_hdr(skb)->saddr);
	ipv6_addr_copy(&ireq6->loc_addr, &ipv6_hdr(skb)->daddr);
	if (ipv6_opt_accepted(sk, skb) ||
	    np->rxopt.bits.rxinfo || np->rxopt.bits.rxoinfo ||
	    np->rxopt.bits.rxhlim || np->rxopt.bits.rxohlim) {
		atomic_inc(&skb->users);
		ireq6->pktopts = skb;
	}

	ireq6->iif = sk->sk_bound_dev_if;
	/* So that link locals have meaning */
	if (!sk->sk_bound_dev_if &&
	    ipv6_addr_type(&ireq6->rmt_addr) & IPV6_ADDR_LINKLOCAL)
		ireq6->iif = inet6_iif(skb);

	req->expires = 0UL;
	req->retrans = 0;
	ireq->ecn_ok		= ecn_ok;
	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->rcv_isn = ntohl(th->seq) - 1;
	treq->snt_isn = cookie;

	/*
	 * 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 flowi fl;
		memset(&fl, 0, sizeof(fl));
		fl.proto = IPPROTO_TCP;
		ipv6_addr_copy(&fl.fl6_dst, &ireq6->rmt_addr);
		final_p = fl6_update_dst(&fl, np->opt, &final);
		ipv6_addr_copy(&fl.fl6_src, &ireq6->loc_addr);
		fl.oif = sk->sk_bound_dev_if;
		fl.mark = sk->sk_mark;
		fl.fl_ip_dport = inet_rsk(req)->rmt_port;
		fl.fl_ip_sport = inet_sk(sk)->inet_sport;
		security_req_classify_flow(req, &fl);
		if (ip6_dst_lookup(sk, &dst, &fl))
			goto out_free;

		if (final_p)
			ipv6_addr_copy(&fl.fl6_dst, final_p);
		if ((xfrm_lookup(sock_net(sk), &dst, &fl, sk, 0)) < 0)
			goto out_free;
	}

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

	ireq->rcv_wscale = rcv_wscale;

	ret = get_cookie_sock(sk, skb, req, dst);
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>
	19	#include <linux/cryptohash.h>
	20	#include <linux/kernel.h>
	21	#include <net/ipv6.h>
	22	#include <net/tcp.h>
	23
	24	extern int sysctl_tcp_syncookies;
2051f11f	25	extern __u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
c6aefafb GG	26
	27	#define COOKIEBITS 24 /* Upper bits store count */
	28	#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
	29
5918e2fb	30	/* Table must be sorted. */
c6aefafb	31	static __u16 const msstab[] = {
5918e2fb FW	32	64,
	33	512,
	34	536,
	35	1280 - 60,
	36	1480 - 60,
	37	1500 - 60,
	38	4460 - 60,
	39	9000 - 60,
c6aefafb	40	};
c6aefafb GG	41
	42	/*
	43	* This (misnamed) value is the age of syncookie which is permitted.
	44	* Its ideal value should be dependent on TCP_TIMEOUT_INIT and
	45	* sysctl_tcp_retries1. It's a rather complicated formula (exponential
	46	* backoff) to compute at runtime so it's currently hardcoded here.
	47	*/
	48	#define COUNTER_TRIES 4
	49
	50	static inline struct sock get_cookie_sock(struct sock sk, struct sk_buff *skb,
	51	struct request_sock *req,
	52	struct dst_entry *dst)
	53	{
	54	struct inet_connection_sock *icsk = inet_csk(sk);
	55	struct sock *child;
	56
	57	child = icsk->icsk_af_ops->syn_recv_sock(sk, skb, req, dst);
	58	if (child)
	59	inet_csk_reqsk_queue_add(sk, req, child);
	60	else
	61	reqsk_free(req);
	62
	63	return child;
	64	}
	65
245b2e70 TH	66	static DEFINE_PER_CPU(__u32 [16 + 5 + SHA_WORKSPACE_WORDS],
245b2e70 TH	67	ipv6_cookie_scratch);
c6aefafb GG	68
	69	static u32 cookie_hash(struct in6_addr saddr, struct in6_addr daddr,
	70	__be16 sport, __be16 dport, u32 count, int c)
	71	{
245b2e70	72	__u32 *tmp = __get_cpu_var(ipv6_cookie_scratch);
c6aefafb GG	73
	74	/*
	75	* we have 320 bits of information to hash, copy in the remaining
	76	* 192 bits required for sha_transform, from the syncookie_secret
	77	* and overwrite the digest with the secret
	78	*/
	79	memcpy(tmp + 10, syncookie_secret[c], 44);
	80	memcpy(tmp, saddr, 16);
	81	memcpy(tmp + 4, daddr, 16);
	82	tmp[8] = ((__force u32)sport << 16) + (__force u32)dport;
	83	tmp[9] = count;
	84	sha_transform(tmp + 16, (__u8 *)tmp, tmp + 16 + 5);
	85
	86	return tmp[17];
	87	}
	88
	89	static __u32 secure_tcp_syn_cookie(struct in6_addr saddr, struct in6_addr daddr,
	90	__be16 sport, __be16 dport, __u32 sseq,
	91	__u32 count, __u32 data)
	92	{
	93	return (cookie_hash(saddr, daddr, sport, dport, 0, 0) +
	94	sseq + (count << COOKIEBITS) +
	95	((cookie_hash(saddr, daddr, sport, dport, count, 1) + data)
	96	& COOKIEMASK));
	97	}
	98
	99	static __u32 check_tcp_syn_cookie(__u32 cookie, struct in6_addr *saddr,
	100	struct in6_addr *daddr, __be16 sport,
	101	__be16 dport, __u32 sseq, __u32 count,
	102	__u32 maxdiff)
	103	{
	104	__u32 diff;
	105
	106	cookie -= cookie_hash(saddr, daddr, sport, dport, 0, 0) + sseq;
	107
	108	diff = (count - (cookie >> COOKIEBITS)) & ((__u32) -1 >> COOKIEBITS);
	109	if (diff >= maxdiff)
	110	return (__u32)-1;
	111
	112	return (cookie -
	113	cookie_hash(saddr, daddr, sport, dport, count - diff, 1))
	114	& COOKIEMASK;
	115	}
	116
	117	__u32 cookie_v6_init_sequence(struct sock sk, struct sk_buff skb, __u16 *mssp)
	118	{
	119	struct ipv6hdr *iph = ipv6_hdr(skb);
	120	const struct tcphdr *th = tcp_hdr(skb);
	121	int mssind;
	122	const __u16 mss = *mssp;
	123
a0f82f64	124	tcp_synq_overflow(sk);
c6aefafb	125
5918e2fb FW	126	for (mssind = ARRAY_SIZE(msstab) - 1; mssind ; mssind--)
	127	if (mss >= msstab[mssind])
	128	break;
	129
	130	*mssp = msstab[mssind];
c6aefafb	131
de0744af	132	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
c6aefafb GG	133
	134	return secure_tcp_syn_cookie(&iph->saddr, &iph->daddr, th->source,
	135	th->dest, ntohl(th->seq),
	136	jiffies / (HZ * 60), mssind);
	137	}
	138
	139	static inline int cookie_check(struct sk_buff *skb, __u32 cookie)
	140	{
	141	struct ipv6hdr *iph = ipv6_hdr(skb);
	142	const struct tcphdr *th = tcp_hdr(skb);
	143	__u32 seq = ntohl(th->seq) - 1;
	144	__u32 mssind = check_tcp_syn_cookie(cookie, &iph->saddr, &iph->daddr,
	145	th->source, th->dest, seq,
	146	jiffies / (HZ * 60), COUNTER_TRIES);
	147
5918e2fb	148	return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0;
c6aefafb GG	149	}
	150
	151	struct sock cookie_v6_check(struct sock sk, struct sk_buff *skb)
	152	{
4957faad WAS	153	struct tcp_options_received tcp_opt;
4957faad WAS	154	u8 *hash_location;
c6aefafb GG	155	struct inet_request_sock *ireq;
	156	struct inet6_request_sock *ireq6;
	157	struct tcp_request_sock *treq;
	158	struct ipv6_pinfo *np = inet6_sk(sk);
	159	struct tcp_sock *tp = tcp_sk(sk);
	160	const struct tcphdr *th = tcp_hdr(skb);
	161	__u32 cookie = ntohl(th->ack_seq) - 1;
	162	struct sock *ret = sk;
	163	struct request_sock *req;
	164	int mss;
	165	struct dst_entry *dst;
	166	__u8 rcv_wscale;
172d69e6	167	bool ecn_ok;
c6aefafb	168
af9b4738	169	if (!sysctl_tcp_syncookies \|\| !th->ack \|\| th->rst)
c6aefafb GG	170	goto out;
c6aefafb GG	171
a0f82f64	172	if (tcp_synq_no_recent_overflow(sk) \|\|
c6aefafb	173	(mss = cookie_check(skb, cookie)) == 0) {
de0744af	174	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
c6aefafb GG	175	goto out;
	176	}
	177
de0744af	178	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV);
c6aefafb	179
bb5b7c11 DM	180	/* check for timestamp cookie support */
	181	memset(&tcp_opt, 0, sizeof(tcp_opt));
	182	tcp_parse_options(skb, &tcp_opt, &hash_location, 0);
	183
172d69e6	184	if (!cookie_check_timestamp(&tcp_opt, &ecn_ok))
8c763681	185	goto out;
bb5b7c11	186
c6aefafb GG	187	ret = NULL;
	188	req = inet6_reqsk_alloc(&tcp6_request_sock_ops);
	189	if (!req)
	190	goto out;
	191
	192	ireq = inet_rsk(req);
	193	ireq6 = inet6_rsk(req);
	194	treq = tcp_rsk(req);
c6aefafb	195
1730554f FW	196	if (security_inet_conn_request(sk, skb, req))
1730554f FW	197	goto out_free;
c6aefafb GG	198
	199	req->mss = mss;
	200	ireq->rmt_port = th->source;
fd507037	201	ireq->loc_port = th->dest;
c6aefafb GG	202	ipv6_addr_copy(&ireq6->rmt_addr, &ipv6_hdr(skb)->saddr);
	203	ipv6_addr_copy(&ireq6->loc_addr, &ipv6_hdr(skb)->daddr);
	204	if (ipv6_opt_accepted(sk, skb) \|\|
	205	np->rxopt.bits.rxinfo \|\| np->rxopt.bits.rxoinfo \|\|
	206	np->rxopt.bits.rxhlim \|\| np->rxopt.bits.rxohlim) {
	207	atomic_inc(&skb->users);
	208	ireq6->pktopts = skb;
	209	}
	210
	211	ireq6->iif = sk->sk_bound_dev_if;
	212	/* So that link locals have meaning */
	213	if (!sk->sk_bound_dev_if &&
	214	ipv6_addr_type(&ireq6->rmt_addr) & IPV6_ADDR_LINKLOCAL)
	215	ireq6->iif = inet6_iif(skb);
	216
	217	req->expires = 0UL;
	218	req->retrans = 0;
172d69e6	219	ireq->ecn_ok = ecn_ok;
bb5b7c11	220	ireq->snd_wscale = tcp_opt.snd_wscale;
bb5b7c11 DM	221	ireq->sack_ok = tcp_opt.sack_ok;
	222	ireq->wscale_ok = tcp_opt.wscale_ok;
	223	ireq->tstamp_ok = tcp_opt.saw_tstamp;
	224	req->ts_recent = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
c6aefafb GG	225	treq->rcv_isn = ntohl(th->seq) - 1;
	226	treq->snt_isn = cookie;
	227
	228	/*
	229	* We need to lookup the dst_entry to get the correct window size.
	230	* This is taken from tcp_v6_syn_recv_sock. Somebody please enlighten
	231	* me if there is a preferred way.
	232	*/
	233	{
20c59de2	234	struct in6_addr *final_p, final;
c6aefafb GG	235	struct flowi fl;
	236	memset(&fl, 0, sizeof(fl));
	237	fl.proto = IPPROTO_TCP;
	238	ipv6_addr_copy(&fl.fl6_dst, &ireq6->rmt_addr);
20c59de2	239	final_p = fl6_update_dst(&fl, np->opt, &final);
c6aefafb GG	240	ipv6_addr_copy(&fl.fl6_src, &ireq6->loc_addr);
c6aefafb GG	241	fl.oif = sk->sk_bound_dev_if;
51953d5b	242	fl.mark = sk->sk_mark;
c6aefafb	243	fl.fl_ip_dport = inet_rsk(req)->rmt_port;
c720c7e8	244	fl.fl_ip_sport = inet_sk(sk)->inet_sport;
c6aefafb	245	security_req_classify_flow(req, &fl);
1730554f FW	246	if (ip6_dst_lookup(sk, &dst, &fl))
	247	goto out_free;
	248
c6aefafb GG	249	if (final_p)
c6aefafb GG	250	ipv6_addr_copy(&fl.fl6_dst, final_p);
52479b62	251	if ((xfrm_lookup(sock_net(sk), &dst, &fl, sk, 0)) < 0)
1730554f	252	goto out_free;
c6aefafb GG	253	}
c6aefafb GG	254
4dfc2817	255	req->window_clamp = tp->window_clamp ? :dst_metric(dst, RTAX_WINDOW);
c6aefafb GG	256	tcp_select_initial_window(tcp_full_space(sk), req->mss,
c6aefafb GG	257	&req->rcv_wnd, &req->window_clamp,
31d12926	258	ireq->wscale_ok, &rcv_wscale,
31d12926	259	dst_metric(dst, RTAX_INITRWND));
c6aefafb GG	260
	261	ireq->rcv_wscale = rcv_wscale;
	262
	263	ret = get_cookie_sock(sk, skb, req, dst);
1730554f FW	264	out:
	265	return ret;
	266	out_free:
	267	reqsk_free(req);
	268	return NULL;
c6aefafb GG	269	}
c6aefafb GG	270