cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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syncookies.c (7610B)


      1// SPDX-License-Identifier: GPL-2.0-or-later
      2/*
      3 *  IPv6 Syncookies implementation for the Linux kernel
      4 *
      5 *  Authors:
      6 *  Glenn Griffin	<ggriffin.kernel@gmail.com>
      7 *
      8 *  Based on IPv4 implementation by Andi Kleen
      9 *  linux/net/ipv4/syncookies.c
     10 */
     11
     12#include <linux/tcp.h>
     13#include <linux/random.h>
     14#include <linux/siphash.h>
     15#include <linux/kernel.h>
     16#include <net/secure_seq.h>
     17#include <net/ipv6.h>
     18#include <net/tcp.h>
     19
     20#define COOKIEBITS 24	/* Upper bits store count */
     21#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
     22
     23static siphash_aligned_key_t syncookie6_secret[2];
     24
     25/* RFC 2460, Section 8.3:
     26 * [ipv6 tcp] MSS must be computed as the maximum packet size minus 60 [..]
     27 *
     28 * Due to IPV6_MIN_MTU=1280 the lowest possible MSS is 1220, which allows
     29 * using higher values than ipv4 tcp syncookies.
     30 * The other values are chosen based on ethernet (1500 and 9k MTU), plus
     31 * one that accounts for common encap (PPPoe) overhead. Table must be sorted.
     32 */
     33static __u16 const msstab[] = {
     34	1280 - 60, /* IPV6_MIN_MTU - 60 */
     35	1480 - 60,
     36	1500 - 60,
     37	9000 - 60,
     38};
     39
     40static u32 cookie_hash(const struct in6_addr *saddr,
     41		       const struct in6_addr *daddr,
     42		       __be16 sport, __be16 dport, u32 count, int c)
     43{
     44	const struct {
     45		struct in6_addr saddr;
     46		struct in6_addr daddr;
     47		u32 count;
     48		__be16 sport;
     49		__be16 dport;
     50	} __aligned(SIPHASH_ALIGNMENT) combined = {
     51		.saddr = *saddr,
     52		.daddr = *daddr,
     53		.count = count,
     54		.sport = sport,
     55		.dport = dport
     56	};
     57
     58	net_get_random_once(syncookie6_secret, sizeof(syncookie6_secret));
     59	return siphash(&combined, offsetofend(typeof(combined), dport),
     60		       &syncookie6_secret[c]);
     61}
     62
     63static __u32 secure_tcp_syn_cookie(const struct in6_addr *saddr,
     64				   const struct in6_addr *daddr,
     65				   __be16 sport, __be16 dport, __u32 sseq,
     66				   __u32 data)
     67{
     68	u32 count = tcp_cookie_time();
     69	return (cookie_hash(saddr, daddr, sport, dport, 0, 0) +
     70		sseq + (count << COOKIEBITS) +
     71		((cookie_hash(saddr, daddr, sport, dport, count, 1) + data)
     72		& COOKIEMASK));
     73}
     74
     75static __u32 check_tcp_syn_cookie(__u32 cookie, const struct in6_addr *saddr,
     76				  const struct in6_addr *daddr, __be16 sport,
     77				  __be16 dport, __u32 sseq)
     78{
     79	__u32 diff, count = tcp_cookie_time();
     80
     81	cookie -= cookie_hash(saddr, daddr, sport, dport, 0, 0) + sseq;
     82
     83	diff = (count - (cookie >> COOKIEBITS)) & ((__u32) -1 >> COOKIEBITS);
     84	if (diff >= MAX_SYNCOOKIE_AGE)
     85		return (__u32)-1;
     86
     87	return (cookie -
     88		cookie_hash(saddr, daddr, sport, dport, count - diff, 1))
     89		& COOKIEMASK;
     90}
     91
     92u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
     93			      const struct tcphdr *th, __u16 *mssp)
     94{
     95	int mssind;
     96	const __u16 mss = *mssp;
     97
     98	for (mssind = ARRAY_SIZE(msstab) - 1; mssind ; mssind--)
     99		if (mss >= msstab[mssind])
    100			break;
    101
    102	*mssp = msstab[mssind];
    103
    104	return secure_tcp_syn_cookie(&iph->saddr, &iph->daddr, th->source,
    105				     th->dest, ntohl(th->seq), mssind);
    106}
    107EXPORT_SYMBOL_GPL(__cookie_v6_init_sequence);
    108
    109__u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mssp)
    110{
    111	const struct ipv6hdr *iph = ipv6_hdr(skb);
    112	const struct tcphdr *th = tcp_hdr(skb);
    113
    114	return __cookie_v6_init_sequence(iph, th, mssp);
    115}
    116
    117int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
    118		      __u32 cookie)
    119{
    120	__u32 seq = ntohl(th->seq) - 1;
    121	__u32 mssind = check_tcp_syn_cookie(cookie, &iph->saddr, &iph->daddr,
    122					    th->source, th->dest, seq);
    123
    124	return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0;
    125}
    126EXPORT_SYMBOL_GPL(__cookie_v6_check);
    127
    128struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
    129{
    130	struct tcp_options_received tcp_opt;
    131	struct inet_request_sock *ireq;
    132	struct tcp_request_sock *treq;
    133	struct ipv6_pinfo *np = inet6_sk(sk);
    134	struct tcp_sock *tp = tcp_sk(sk);
    135	const struct tcphdr *th = tcp_hdr(skb);
    136	__u32 cookie = ntohl(th->ack_seq) - 1;
    137	struct sock *ret = sk;
    138	struct request_sock *req;
    139	int full_space, mss;
    140	struct dst_entry *dst;
    141	__u8 rcv_wscale;
    142	u32 tsoff = 0;
    143
    144	if (!sock_net(sk)->ipv4.sysctl_tcp_syncookies || !th->ack || th->rst)
    145		goto out;
    146
    147	if (tcp_synq_no_recent_overflow(sk))
    148		goto out;
    149
    150	mss = __cookie_v6_check(ipv6_hdr(skb), th, cookie);
    151	if (mss == 0) {
    152		__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
    153		goto out;
    154	}
    155
    156	__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV);
    157
    158	/* check for timestamp cookie support */
    159	memset(&tcp_opt, 0, sizeof(tcp_opt));
    160	tcp_parse_options(sock_net(sk), skb, &tcp_opt, 0, NULL);
    161
    162	if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {
    163		tsoff = secure_tcpv6_ts_off(sock_net(sk),
    164					    ipv6_hdr(skb)->daddr.s6_addr32,
    165					    ipv6_hdr(skb)->saddr.s6_addr32);
    166		tcp_opt.rcv_tsecr -= tsoff;
    167	}
    168
    169	if (!cookie_timestamp_decode(sock_net(sk), &tcp_opt))
    170		goto out;
    171
    172	ret = NULL;
    173	req = cookie_tcp_reqsk_alloc(&tcp6_request_sock_ops,
    174				     &tcp_request_sock_ipv6_ops, sk, skb);
    175	if (!req)
    176		goto out;
    177
    178	ireq = inet_rsk(req);
    179	treq = tcp_rsk(req);
    180	treq->tfo_listener = false;
    181
    182	if (security_inet_conn_request(sk, skb, req))
    183		goto out_free;
    184
    185	req->mss = mss;
    186	ireq->ir_rmt_port = th->source;
    187	ireq->ir_num = ntohs(th->dest);
    188	ireq->ir_v6_rmt_addr = ipv6_hdr(skb)->saddr;
    189	ireq->ir_v6_loc_addr = ipv6_hdr(skb)->daddr;
    190	if (ipv6_opt_accepted(sk, skb, &TCP_SKB_CB(skb)->header.h6) ||
    191	    np->rxopt.bits.rxinfo || np->rxopt.bits.rxoinfo ||
    192	    np->rxopt.bits.rxhlim || np->rxopt.bits.rxohlim) {
    193		refcount_inc(&skb->users);
    194		ireq->pktopts = skb;
    195	}
    196
    197	ireq->ir_iif = inet_request_bound_dev_if(sk, skb);
    198	/* So that link locals have meaning */
    199	if (!sk->sk_bound_dev_if &&
    200	    ipv6_addr_type(&ireq->ir_v6_rmt_addr) & IPV6_ADDR_LINKLOCAL)
    201		ireq->ir_iif = tcp_v6_iif(skb);
    202
    203	ireq->ir_mark = inet_request_mark(sk, skb);
    204
    205	req->num_retrans = 0;
    206	ireq->snd_wscale	= tcp_opt.snd_wscale;
    207	ireq->sack_ok		= tcp_opt.sack_ok;
    208	ireq->wscale_ok		= tcp_opt.wscale_ok;
    209	ireq->tstamp_ok		= tcp_opt.saw_tstamp;
    210	req->ts_recent		= tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
    211	treq->snt_synack	= 0;
    212	treq->rcv_isn = ntohl(th->seq) - 1;
    213	treq->snt_isn = cookie;
    214	treq->ts_off = 0;
    215	treq->txhash = net_tx_rndhash();
    216	if (IS_ENABLED(CONFIG_SMC))
    217		ireq->smc_ok = 0;
    218
    219	/*
    220	 * We need to lookup the dst_entry to get the correct window size.
    221	 * This is taken from tcp_v6_syn_recv_sock.  Somebody please enlighten
    222	 * me if there is a preferred way.
    223	 */
    224	{
    225		struct in6_addr *final_p, final;
    226		struct flowi6 fl6;
    227		memset(&fl6, 0, sizeof(fl6));
    228		fl6.flowi6_proto = IPPROTO_TCP;
    229		fl6.daddr = ireq->ir_v6_rmt_addr;
    230		final_p = fl6_update_dst(&fl6, rcu_dereference(np->opt), &final);
    231		fl6.saddr = ireq->ir_v6_loc_addr;
    232		fl6.flowi6_oif = ireq->ir_iif;
    233		fl6.flowi6_mark = ireq->ir_mark;
    234		fl6.fl6_dport = ireq->ir_rmt_port;
    235		fl6.fl6_sport = inet_sk(sk)->inet_sport;
    236		fl6.flowi6_uid = sk->sk_uid;
    237		security_req_classify_flow(req, flowi6_to_flowi_common(&fl6));
    238
    239		dst = ip6_dst_lookup_flow(sock_net(sk), sk, &fl6, final_p);
    240		if (IS_ERR(dst))
    241			goto out_free;
    242	}
    243
    244	req->rsk_window_clamp = tp->window_clamp ? :dst_metric(dst, RTAX_WINDOW);
    245	/* limit the window selection if the user enforce a smaller rx buffer */
    246	full_space = tcp_full_space(sk);
    247	if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
    248	    (req->rsk_window_clamp > full_space || req->rsk_window_clamp == 0))
    249		req->rsk_window_clamp = full_space;
    250
    251	tcp_select_initial_window(sk, full_space, req->mss,
    252				  &req->rsk_rcv_wnd, &req->rsk_window_clamp,
    253				  ireq->wscale_ok, &rcv_wscale,
    254				  dst_metric(dst, RTAX_INITRWND));
    255
    256	ireq->rcv_wscale = rcv_wscale;
    257	ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, sock_net(sk), dst);
    258
    259	ret = tcp_get_cookie_sock(sk, skb, req, dst, tsoff);
    260out:
    261	return ret;
    262out_free:
    263	reqsk_free(req);
    264	return NULL;
    265}