2008-02-08 06:49:26 +01:00
|
|
|
/*
|
|
|
|
* 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;
|
2008-03-24 06:21:28 +01:00
|
|
|
extern __u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
|
2008-02-08 06:49:26 +01:00
|
|
|
|
|
|
|
#define COOKIEBITS 24 /* Upper bits store count */
|
|
|
|
#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
|
|
|
|
|
|
|
|
/*
|
|
|
|
* This table has to be sorted and terminated with (__u16)-1.
|
|
|
|
* XXX generate a better table.
|
|
|
|
* Unresolved Issues: HIPPI with a 64k MSS is not well supported.
|
|
|
|
*
|
|
|
|
* Taken directly from ipv4 implementation.
|
|
|
|
* Should this list be modified for ipv6 use or is it close enough?
|
|
|
|
* rfc 2460 8.3 suggests mss values 20 bytes less than ipv4 counterpart
|
|
|
|
*/
|
|
|
|
static __u16 const msstab[] = {
|
|
|
|
64 - 1,
|
|
|
|
256 - 1,
|
|
|
|
512 - 1,
|
|
|
|
536 - 1,
|
|
|
|
1024 - 1,
|
|
|
|
1440 - 1,
|
|
|
|
1460 - 1,
|
|
|
|
4312 - 1,
|
|
|
|
(__u16)-1
|
|
|
|
};
|
|
|
|
/* The number doesn't include the -1 terminator */
|
|
|
|
#define NUM_MSS (ARRAY_SIZE(msstab) - 1)
|
|
|
|
|
|
|
|
/*
|
|
|
|
* 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;
|
|
|
|
}
|
|
|
|
|
2009-06-24 08:13:48 +02:00
|
|
|
static DEFINE_PER_CPU(__u32 [16 + 5 + SHA_WORKSPACE_WORDS],
|
|
|
|
ipv6_cookie_scratch);
|
2008-02-08 06:49:26 +01:00
|
|
|
|
|
|
|
static u32 cookie_hash(struct in6_addr *saddr, struct in6_addr *daddr,
|
|
|
|
__be16 sport, __be16 dport, u32 count, int c)
|
|
|
|
{
|
2009-06-24 08:13:48 +02:00
|
|
|
__u32 *tmp = __get_cpu_var(ipv6_cookie_scratch);
|
2008-02-08 06:49:26 +01:00
|
|
|
|
|
|
|
/*
|
|
|
|
* 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;
|
|
|
|
|
2009-04-19 11:43:48 +02:00
|
|
|
tcp_synq_overflow(sk);
|
2008-02-08 06:49:26 +01:00
|
|
|
|
|
|
|
for (mssind = 0; mss > msstab[mssind + 1]; mssind++)
|
|
|
|
;
|
|
|
|
*mssp = msstab[mssind] + 1;
|
|
|
|
|
2008-07-17 05:31:16 +02:00
|
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
|
2008-02-08 06:49:26 +01:00
|
|
|
|
|
|
|
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 < NUM_MSS ? msstab[mssind] + 1 : 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
|
|
|
|
{
|
|
|
|
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;
|
2008-04-10 12:12:40 +02:00
|
|
|
struct tcp_options_received tcp_opt;
|
2008-02-08 06:49:26 +01:00
|
|
|
|
|
|
|
if (!sysctl_tcp_syncookies || !th->ack)
|
|
|
|
goto out;
|
|
|
|
|
2009-04-19 11:43:48 +02:00
|
|
|
if (tcp_synq_no_recent_overflow(sk) ||
|
2008-02-08 06:49:26 +01:00
|
|
|
(mss = cookie_check(skb, cookie)) == 0) {
|
2008-07-17 05:31:16 +02:00
|
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
|
2008-02-08 06:49:26 +01:00
|
|
|
goto out;
|
|
|
|
}
|
|
|
|
|
2008-07-17 05:31:16 +02:00
|
|
|
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV);
|
2008-02-08 06:49:26 +01:00
|
|
|
|
2008-04-10 12:12:40 +02:00
|
|
|
/* check for timestamp cookie support */
|
|
|
|
memset(&tcp_opt, 0, sizeof(tcp_opt));
|
|
|
|
tcp_parse_options(skb, &tcp_opt, 0);
|
|
|
|
|
|
|
|
if (tcp_opt.saw_tstamp)
|
|
|
|
cookie_check_timestamp(&tcp_opt);
|
|
|
|
|
2008-02-08 06:49:26 +01:00
|
|
|
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);
|
|
|
|
|
2008-08-04 03:13:44 +02:00
|
|
|
if (security_inet_conn_request(sk, skb, req))
|
|
|
|
goto out_free;
|
2008-02-08 06:49:26 +01:00
|
|
|
|
|
|
|
req->mss = mss;
|
|
|
|
ireq->rmt_port = th->source;
|
2008-10-20 08:35:58 +02:00
|
|
|
ireq->loc_port = th->dest;
|
2008-02-08 06:49:26 +01:00
|
|
|
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;
|
2008-07-26 11:21:54 +02:00
|
|
|
ireq->ecn_ok = 0;
|
2008-04-10 12:12:40 +02:00
|
|
|
ireq->snd_wscale = tcp_opt.snd_wscale;
|
|
|
|
ireq->rcv_wscale = tcp_opt.rcv_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;
|
2008-02-08 06:49:26 +01:00
|
|
|
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 = NULL, final;
|
|
|
|
struct flowi fl;
|
|
|
|
memset(&fl, 0, sizeof(fl));
|
|
|
|
fl.proto = IPPROTO_TCP;
|
|
|
|
ipv6_addr_copy(&fl.fl6_dst, &ireq6->rmt_addr);
|
|
|
|
if (np->opt && np->opt->srcrt) {
|
|
|
|
struct rt0_hdr *rt0 = (struct rt0_hdr *) np->opt->srcrt;
|
|
|
|
ipv6_addr_copy(&final, &fl.fl6_dst);
|
|
|
|
ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
|
|
|
|
final_p = &final;
|
|
|
|
}
|
|
|
|
ipv6_addr_copy(&fl.fl6_src, &ireq6->loc_addr);
|
|
|
|
fl.oif = sk->sk_bound_dev_if;
|
2009-10-05 10:24:16 +02:00
|
|
|
fl.mark = sk->sk_mark;
|
2008-02-08 06:49:26 +01:00
|
|
|
fl.fl_ip_dport = inet_rsk(req)->rmt_port;
|
|
|
|
fl.fl_ip_sport = inet_sk(sk)->sport;
|
|
|
|
security_req_classify_flow(req, &fl);
|
2008-08-04 03:13:44 +02:00
|
|
|
if (ip6_dst_lookup(sk, &dst, &fl))
|
|
|
|
goto out_free;
|
|
|
|
|
2008-02-08 06:49:26 +01:00
|
|
|
if (final_p)
|
|
|
|
ipv6_addr_copy(&fl.fl6_dst, final_p);
|
2008-11-26 02:35:18 +01:00
|
|
|
if ((xfrm_lookup(sock_net(sk), &dst, &fl, sk, 0)) < 0)
|
2008-08-04 03:13:44 +02:00
|
|
|
goto out_free;
|
2008-02-08 06:49:26 +01:00
|
|
|
}
|
|
|
|
|
2008-04-10 12:12:40 +02:00
|
|
|
req->window_clamp = tp->window_clamp ? :dst_metric(dst, RTAX_WINDOW);
|
2008-02-08 06:49:26 +01:00
|
|
|
tcp_select_initial_window(tcp_full_space(sk), req->mss,
|
|
|
|
&req->rcv_wnd, &req->window_clamp,
|
2008-04-10 12:12:40 +02:00
|
|
|
ireq->wscale_ok, &rcv_wscale);
|
2008-02-08 06:49:26 +01:00
|
|
|
|
|
|
|
ireq->rcv_wscale = rcv_wscale;
|
|
|
|
|
|
|
|
ret = get_cookie_sock(sk, skb, req, dst);
|
2008-08-04 03:13:44 +02:00
|
|
|
out:
|
|
|
|
return ret;
|
|
|
|
out_free:
|
|
|
|
reqsk_free(req);
|
|
|
|
return NULL;
|
2008-02-08 06:49:26 +01:00
|
|
|
}
|
|
|
|
|