![Lorenzo Colitti](/assets/img/avatar_default.png)
- Use the UID in routing lookups made by protocol connect() and sendmsg() functions. - Make sure that routing lookups triggered by incoming packets (e.g., Path MTU discovery) take the UID of the socket into account. - For packets not associated with a userspace socket, (e.g., ping replies) use UID 0 inside the user namespace corresponding to the network namespace the socket belongs to. This allows all namespaces to apply routing and iptables rules to kernel-originated traffic in that namespaces by matching UID 0. This is better than using the UID of the kernel socket that is sending the traffic, because the UID of kernel sockets created at namespace creation time (e.g., the per-processor ICMP and TCP sockets) is the UID of the user that created the socket, which might not be mapped in the namespace. Tested: compiles allnoconfig, allyesconfig, allmodconfig Tested: https://android-review.googlesource.com/253302 Signed-off-by: Lorenzo Colitti <lorenzo@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
254 lines
7.2 KiB
C
254 lines
7.2 KiB
C
/*
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* IPv6 Syncookies implementation for the Linux kernel
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*
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* Authors:
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* Glenn Griffin <ggriffin.kernel@gmail.com>
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*
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* Based on IPv4 implementation by Andi Kleen
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* linux/net/ipv4/syncookies.c
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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*/
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#include <linux/tcp.h>
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#include <linux/random.h>
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#include <linux/cryptohash.h>
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#include <linux/kernel.h>
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#include <net/ipv6.h>
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#include <net/tcp.h>
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#define COOKIEBITS 24 /* Upper bits store count */
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#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
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static u32 syncookie6_secret[2][16-4+SHA_DIGEST_WORDS] __read_mostly;
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/* RFC 2460, Section 8.3:
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* [ipv6 tcp] MSS must be computed as the maximum packet size minus 60 [..]
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*
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* Due to IPV6_MIN_MTU=1280 the lowest possible MSS is 1220, which allows
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* using higher values than ipv4 tcp syncookies.
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* The other values are chosen based on ethernet (1500 and 9k MTU), plus
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* one that accounts for common encap (PPPoe) overhead. Table must be sorted.
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*/
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static __u16 const msstab[] = {
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1280 - 60, /* IPV6_MIN_MTU - 60 */
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1480 - 60,
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1500 - 60,
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9000 - 60,
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};
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static DEFINE_PER_CPU(__u32 [16 + 5 + SHA_WORKSPACE_WORDS], ipv6_cookie_scratch);
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static u32 cookie_hash(const struct in6_addr *saddr, const struct in6_addr *daddr,
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__be16 sport, __be16 dport, u32 count, int c)
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{
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__u32 *tmp;
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net_get_random_once(syncookie6_secret, sizeof(syncookie6_secret));
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tmp = this_cpu_ptr(ipv6_cookie_scratch);
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/*
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* we have 320 bits of information to hash, copy in the remaining
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* 192 bits required for sha_transform, from the syncookie6_secret
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* and overwrite the digest with the secret
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*/
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memcpy(tmp + 10, syncookie6_secret[c], 44);
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memcpy(tmp, saddr, 16);
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memcpy(tmp + 4, daddr, 16);
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tmp[8] = ((__force u32)sport << 16) + (__force u32)dport;
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tmp[9] = count;
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sha_transform(tmp + 16, (__u8 *)tmp, tmp + 16 + 5);
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return tmp[17];
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}
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static __u32 secure_tcp_syn_cookie(const struct in6_addr *saddr,
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const struct in6_addr *daddr,
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__be16 sport, __be16 dport, __u32 sseq,
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__u32 data)
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{
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u32 count = tcp_cookie_time();
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return (cookie_hash(saddr, daddr, sport, dport, 0, 0) +
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sseq + (count << COOKIEBITS) +
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((cookie_hash(saddr, daddr, sport, dport, count, 1) + data)
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& COOKIEMASK));
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}
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static __u32 check_tcp_syn_cookie(__u32 cookie, const struct in6_addr *saddr,
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const struct in6_addr *daddr, __be16 sport,
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__be16 dport, __u32 sseq)
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{
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__u32 diff, count = tcp_cookie_time();
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cookie -= cookie_hash(saddr, daddr, sport, dport, 0, 0) + sseq;
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diff = (count - (cookie >> COOKIEBITS)) & ((__u32) -1 >> COOKIEBITS);
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if (diff >= MAX_SYNCOOKIE_AGE)
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return (__u32)-1;
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return (cookie -
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cookie_hash(saddr, daddr, sport, dport, count - diff, 1))
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& COOKIEMASK;
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}
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u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
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const struct tcphdr *th, __u16 *mssp)
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{
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int mssind;
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const __u16 mss = *mssp;
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for (mssind = ARRAY_SIZE(msstab) - 1; mssind ; mssind--)
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if (mss >= msstab[mssind])
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break;
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*mssp = msstab[mssind];
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return secure_tcp_syn_cookie(&iph->saddr, &iph->daddr, th->source,
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th->dest, ntohl(th->seq), mssind);
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}
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EXPORT_SYMBOL_GPL(__cookie_v6_init_sequence);
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__u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mssp)
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{
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const struct ipv6hdr *iph = ipv6_hdr(skb);
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const struct tcphdr *th = tcp_hdr(skb);
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return __cookie_v6_init_sequence(iph, th, mssp);
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}
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int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
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__u32 cookie)
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{
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__u32 seq = ntohl(th->seq) - 1;
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__u32 mssind = check_tcp_syn_cookie(cookie, &iph->saddr, &iph->daddr,
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th->source, th->dest, seq);
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return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0;
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}
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EXPORT_SYMBOL_GPL(__cookie_v6_check);
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struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
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{
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struct tcp_options_received tcp_opt;
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struct inet_request_sock *ireq;
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struct tcp_request_sock *treq;
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struct ipv6_pinfo *np = inet6_sk(sk);
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struct tcp_sock *tp = tcp_sk(sk);
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const struct tcphdr *th = tcp_hdr(skb);
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__u32 cookie = ntohl(th->ack_seq) - 1;
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struct sock *ret = sk;
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struct request_sock *req;
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int mss;
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struct dst_entry *dst;
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__u8 rcv_wscale;
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if (!sock_net(sk)->ipv4.sysctl_tcp_syncookies || !th->ack || th->rst)
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goto out;
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if (tcp_synq_no_recent_overflow(sk))
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goto out;
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mss = __cookie_v6_check(ipv6_hdr(skb), th, cookie);
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if (mss == 0) {
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__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
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goto out;
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}
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__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV);
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/* check for timestamp cookie support */
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memset(&tcp_opt, 0, sizeof(tcp_opt));
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tcp_parse_options(skb, &tcp_opt, 0, NULL);
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if (!cookie_timestamp_decode(&tcp_opt))
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goto out;
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ret = NULL;
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req = inet_reqsk_alloc(&tcp6_request_sock_ops, sk, false);
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if (!req)
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goto out;
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ireq = inet_rsk(req);
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treq = tcp_rsk(req);
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treq->tfo_listener = false;
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if (security_inet_conn_request(sk, skb, req))
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goto out_free;
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req->mss = mss;
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ireq->ir_rmt_port = th->source;
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ireq->ir_num = ntohs(th->dest);
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ireq->ir_v6_rmt_addr = ipv6_hdr(skb)->saddr;
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ireq->ir_v6_loc_addr = ipv6_hdr(skb)->daddr;
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if (ipv6_opt_accepted(sk, skb, &TCP_SKB_CB(skb)->header.h6) ||
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np->rxopt.bits.rxinfo || np->rxopt.bits.rxoinfo ||
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np->rxopt.bits.rxhlim || np->rxopt.bits.rxohlim) {
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atomic_inc(&skb->users);
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ireq->pktopts = skb;
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}
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ireq->ir_iif = inet_request_bound_dev_if(sk, skb);
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/* So that link locals have meaning */
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if (!sk->sk_bound_dev_if &&
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ipv6_addr_type(&ireq->ir_v6_rmt_addr) & IPV6_ADDR_LINKLOCAL)
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ireq->ir_iif = tcp_v6_iif(skb);
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ireq->ir_mark = inet_request_mark(sk, skb);
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req->num_retrans = 0;
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ireq->snd_wscale = tcp_opt.snd_wscale;
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ireq->sack_ok = tcp_opt.sack_ok;
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ireq->wscale_ok = tcp_opt.wscale_ok;
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ireq->tstamp_ok = tcp_opt.saw_tstamp;
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req->ts_recent = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
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treq->snt_synack.v64 = 0;
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treq->rcv_isn = ntohl(th->seq) - 1;
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treq->snt_isn = cookie;
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/*
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* We need to lookup the dst_entry to get the correct window size.
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* This is taken from tcp_v6_syn_recv_sock. Somebody please enlighten
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* me if there is a preferred way.
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*/
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{
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struct in6_addr *final_p, final;
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struct flowi6 fl6;
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memset(&fl6, 0, sizeof(fl6));
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fl6.flowi6_proto = IPPROTO_TCP;
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fl6.daddr = ireq->ir_v6_rmt_addr;
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final_p = fl6_update_dst(&fl6, rcu_dereference(np->opt), &final);
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fl6.saddr = ireq->ir_v6_loc_addr;
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fl6.flowi6_oif = ireq->ir_iif;
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fl6.flowi6_mark = ireq->ir_mark;
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fl6.fl6_dport = ireq->ir_rmt_port;
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fl6.fl6_sport = inet_sk(sk)->inet_sport;
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fl6.flowi6_uid = sk->sk_uid;
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security_req_classify_flow(req, flowi6_to_flowi(&fl6));
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dst = ip6_dst_lookup_flow(sk, &fl6, final_p);
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if (IS_ERR(dst))
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goto out_free;
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}
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req->rsk_window_clamp = tp->window_clamp ? :dst_metric(dst, RTAX_WINDOW);
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tcp_select_initial_window(tcp_full_space(sk), req->mss,
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&req->rsk_rcv_wnd, &req->rsk_window_clamp,
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ireq->wscale_ok, &rcv_wscale,
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dst_metric(dst, RTAX_INITRWND));
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ireq->rcv_wscale = rcv_wscale;
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ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, sock_net(sk), dst);
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ret = tcp_get_cookie_sock(sk, skb, req, dst);
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out:
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return ret;
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out_free:
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reqsk_free(req);
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return NULL;
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}
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