From d7f9b2f18eaef74b4f948c7e24e3a8f796f0c90d Mon Sep 17 00:00:00 2001 From: Fernando Fernandez Mancera Date: Fri, 7 Jun 2019 02:36:07 +0200 Subject: netfilter: synproxy: extract SYNPROXY infrastructure from {ipt, ip6t}_SYNPROXY Add common functions into nf_synproxy_core.c to prepare for nftables support. The prototypes of the functions used by {ipt, ip6t}_SYNPROXY are in the new file nf_synproxy.h Signed-off-by: Fernando Fernandez Mancera Signed-off-by: Pablo Neira Ayuso --- net/ipv4/netfilter/ipt_SYNPROXY.c | 394 +------------------------------------- 1 file changed, 6 insertions(+), 388 deletions(-) (limited to 'net/ipv4/netfilter') diff --git a/net/ipv4/netfilter/ipt_SYNPROXY.c b/net/ipv4/netfilter/ipt_SYNPROXY.c index 690b17ef6a44..7f7979734fb4 100644 --- a/net/ipv4/netfilter/ipt_SYNPROXY.c +++ b/net/ipv4/netfilter/ipt_SYNPROXY.c @@ -6,258 +6,11 @@ * published by the Free Software Foundation. */ -#include -#include -#include - #include #include #include -#include -#include -#include -#include - -static struct iphdr * -synproxy_build_ip(struct net *net, struct sk_buff *skb, __be32 saddr, - __be32 daddr) -{ - struct iphdr *iph; - - skb_reset_network_header(skb); - iph = skb_put(skb, sizeof(*iph)); - iph->version = 4; - iph->ihl = sizeof(*iph) / 4; - iph->tos = 0; - iph->id = 0; - iph->frag_off = htons(IP_DF); - iph->ttl = net->ipv4.sysctl_ip_default_ttl; - iph->protocol = IPPROTO_TCP; - iph->check = 0; - iph->saddr = saddr; - iph->daddr = daddr; - - return iph; -} - -static void -synproxy_send_tcp(struct net *net, - const struct sk_buff *skb, struct sk_buff *nskb, - struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo, - struct iphdr *niph, struct tcphdr *nth, - unsigned int tcp_hdr_size) -{ - nth->check = ~tcp_v4_check(tcp_hdr_size, niph->saddr, niph->daddr, 0); - nskb->ip_summed = CHECKSUM_PARTIAL; - nskb->csum_start = (unsigned char *)nth - nskb->head; - nskb->csum_offset = offsetof(struct tcphdr, check); - - skb_dst_set_noref(nskb, skb_dst(skb)); - nskb->protocol = htons(ETH_P_IP); - if (ip_route_me_harder(net, nskb, RTN_UNSPEC)) - goto free_nskb; - - if (nfct) { - nf_ct_set(nskb, (struct nf_conn *)nfct, ctinfo); - nf_conntrack_get(nfct); - } - - ip_local_out(net, nskb->sk, nskb); - return; - -free_nskb: - kfree_skb(nskb); -} - -static void -synproxy_send_client_synack(struct net *net, - const struct sk_buff *skb, const struct tcphdr *th, - const struct synproxy_options *opts) -{ - struct sk_buff *nskb; - struct iphdr *iph, *niph; - struct tcphdr *nth; - unsigned int tcp_hdr_size; - u16 mss = opts->mss; - - iph = ip_hdr(skb); - - tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts); - nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER, - GFP_ATOMIC); - if (nskb == NULL) - return; - skb_reserve(nskb, MAX_TCP_HEADER); - - niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr); - - skb_reset_transport_header(nskb); - nth = skb_put(nskb, tcp_hdr_size); - nth->source = th->dest; - nth->dest = th->source; - nth->seq = htonl(__cookie_v4_init_sequence(iph, th, &mss)); - nth->ack_seq = htonl(ntohl(th->seq) + 1); - tcp_flag_word(nth) = TCP_FLAG_SYN | TCP_FLAG_ACK; - if (opts->options & XT_SYNPROXY_OPT_ECN) - tcp_flag_word(nth) |= TCP_FLAG_ECE; - nth->doff = tcp_hdr_size / 4; - nth->window = 0; - nth->check = 0; - nth->urg_ptr = 0; - - synproxy_build_options(nth, opts); - - synproxy_send_tcp(net, skb, nskb, skb_nfct(skb), - IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size); -} - -static void -synproxy_send_server_syn(struct net *net, - const struct sk_buff *skb, const struct tcphdr *th, - const struct synproxy_options *opts, u32 recv_seq) -{ - struct synproxy_net *snet = synproxy_pernet(net); - struct sk_buff *nskb; - struct iphdr *iph, *niph; - struct tcphdr *nth; - unsigned int tcp_hdr_size; - - iph = ip_hdr(skb); - - tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts); - nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER, - GFP_ATOMIC); - if (nskb == NULL) - return; - skb_reserve(nskb, MAX_TCP_HEADER); - - niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr); - - skb_reset_transport_header(nskb); - nth = skb_put(nskb, tcp_hdr_size); - nth->source = th->source; - nth->dest = th->dest; - nth->seq = htonl(recv_seq - 1); - /* ack_seq is used to relay our ISN to the synproxy hook to initialize - * sequence number translation once a connection tracking entry exists. - */ - nth->ack_seq = htonl(ntohl(th->ack_seq) - 1); - tcp_flag_word(nth) = TCP_FLAG_SYN; - if (opts->options & XT_SYNPROXY_OPT_ECN) - tcp_flag_word(nth) |= TCP_FLAG_ECE | TCP_FLAG_CWR; - nth->doff = tcp_hdr_size / 4; - nth->window = th->window; - nth->check = 0; - nth->urg_ptr = 0; - - synproxy_build_options(nth, opts); - - synproxy_send_tcp(net, skb, nskb, &snet->tmpl->ct_general, IP_CT_NEW, - niph, nth, tcp_hdr_size); -} - -static void -synproxy_send_server_ack(struct net *net, - const struct ip_ct_tcp *state, - const struct sk_buff *skb, const struct tcphdr *th, - const struct synproxy_options *opts) -{ - struct sk_buff *nskb; - struct iphdr *iph, *niph; - struct tcphdr *nth; - unsigned int tcp_hdr_size; - - iph = ip_hdr(skb); - - tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts); - nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER, - GFP_ATOMIC); - if (nskb == NULL) - return; - skb_reserve(nskb, MAX_TCP_HEADER); - - niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr); - skb_reset_transport_header(nskb); - nth = skb_put(nskb, tcp_hdr_size); - nth->source = th->dest; - nth->dest = th->source; - nth->seq = htonl(ntohl(th->ack_seq)); - nth->ack_seq = htonl(ntohl(th->seq) + 1); - tcp_flag_word(nth) = TCP_FLAG_ACK; - nth->doff = tcp_hdr_size / 4; - nth->window = htons(state->seen[IP_CT_DIR_ORIGINAL].td_maxwin); - nth->check = 0; - nth->urg_ptr = 0; - - synproxy_build_options(nth, opts); - - synproxy_send_tcp(net, skb, nskb, NULL, 0, niph, nth, tcp_hdr_size); -} - -static void -synproxy_send_client_ack(struct net *net, - const struct sk_buff *skb, const struct tcphdr *th, - const struct synproxy_options *opts) -{ - struct sk_buff *nskb; - struct iphdr *iph, *niph; - struct tcphdr *nth; - unsigned int tcp_hdr_size; - - iph = ip_hdr(skb); - - tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts); - nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER, - GFP_ATOMIC); - if (nskb == NULL) - return; - skb_reserve(nskb, MAX_TCP_HEADER); - - niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr); - - skb_reset_transport_header(nskb); - nth = skb_put(nskb, tcp_hdr_size); - nth->source = th->source; - nth->dest = th->dest; - nth->seq = htonl(ntohl(th->seq) + 1); - nth->ack_seq = th->ack_seq; - tcp_flag_word(nth) = TCP_FLAG_ACK; - nth->doff = tcp_hdr_size / 4; - nth->window = htons(ntohs(th->window) >> opts->wscale); - nth->check = 0; - nth->urg_ptr = 0; - - synproxy_build_options(nth, opts); - - synproxy_send_tcp(net, skb, nskb, skb_nfct(skb), - IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size); -} - -static bool -synproxy_recv_client_ack(struct net *net, - const struct sk_buff *skb, const struct tcphdr *th, - struct synproxy_options *opts, u32 recv_seq) -{ - struct synproxy_net *snet = synproxy_pernet(net); - int mss; - - mss = __cookie_v4_check(ip_hdr(skb), th, ntohl(th->ack_seq) - 1); - if (mss == 0) { - this_cpu_inc(snet->stats->cookie_invalid); - return false; - } - - this_cpu_inc(snet->stats->cookie_valid); - opts->mss = mss; - opts->options |= XT_SYNPROXY_OPT_MSS; - - if (opts->options & XT_SYNPROXY_OPT_TIMESTAMP) - synproxy_check_timestamp_cookie(opts); - - synproxy_send_server_syn(net, skb, th, opts, recv_seq); - return true; -} +#include static unsigned int synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par) @@ -309,135 +62,6 @@ synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par) return XT_CONTINUE; } -static unsigned int ipv4_synproxy_hook(void *priv, - struct sk_buff *skb, - const struct nf_hook_state *nhs) -{ - struct net *net = nhs->net; - struct synproxy_net *snet = synproxy_pernet(net); - enum ip_conntrack_info ctinfo; - struct nf_conn *ct; - struct nf_conn_synproxy *synproxy; - struct synproxy_options opts = {}; - const struct ip_ct_tcp *state; - struct tcphdr *th, _th; - unsigned int thoff; - - ct = nf_ct_get(skb, &ctinfo); - if (ct == NULL) - return NF_ACCEPT; - - synproxy = nfct_synproxy(ct); - if (synproxy == NULL) - return NF_ACCEPT; - - if (nf_is_loopback_packet(skb) || - ip_hdr(skb)->protocol != IPPROTO_TCP) - return NF_ACCEPT; - - thoff = ip_hdrlen(skb); - th = skb_header_pointer(skb, thoff, sizeof(_th), &_th); - if (th == NULL) - return NF_DROP; - - state = &ct->proto.tcp; - switch (state->state) { - case TCP_CONNTRACK_CLOSE: - if (th->rst && !test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) { - nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - - ntohl(th->seq) + 1); - break; - } - - if (!th->syn || th->ack || - CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) - break; - - /* Reopened connection - reset the sequence number and timestamp - * adjustments, they will get initialized once the connection is - * reestablished. - */ - nf_ct_seqadj_init(ct, ctinfo, 0); - synproxy->tsoff = 0; - this_cpu_inc(snet->stats->conn_reopened); - - /* fall through */ - case TCP_CONNTRACK_SYN_SENT: - if (!synproxy_parse_options(skb, thoff, th, &opts)) - return NF_DROP; - - if (!th->syn && th->ack && - CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) { - /* Keep-Alives are sent with SEG.SEQ = SND.NXT-1, - * therefore we need to add 1 to make the SYN sequence - * number match the one of first SYN. - */ - if (synproxy_recv_client_ack(net, skb, th, &opts, - ntohl(th->seq) + 1)) { - this_cpu_inc(snet->stats->cookie_retrans); - consume_skb(skb); - return NF_STOLEN; - } else { - return NF_DROP; - } - } - - synproxy->isn = ntohl(th->ack_seq); - if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP) - synproxy->its = opts.tsecr; - - nf_conntrack_event_cache(IPCT_SYNPROXY, ct); - break; - case TCP_CONNTRACK_SYN_RECV: - if (!th->syn || !th->ack) - break; - - if (!synproxy_parse_options(skb, thoff, th, &opts)) - return NF_DROP; - - if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP) { - synproxy->tsoff = opts.tsval - synproxy->its; - nf_conntrack_event_cache(IPCT_SYNPROXY, ct); - } - - opts.options &= ~(XT_SYNPROXY_OPT_MSS | - XT_SYNPROXY_OPT_WSCALE | - XT_SYNPROXY_OPT_SACK_PERM); - - swap(opts.tsval, opts.tsecr); - synproxy_send_server_ack(net, state, skb, th, &opts); - - nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - ntohl(th->seq)); - nf_conntrack_event_cache(IPCT_SEQADJ, ct); - - swap(opts.tsval, opts.tsecr); - synproxy_send_client_ack(net, skb, th, &opts); - - consume_skb(skb); - return NF_STOLEN; - default: - break; - } - - synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy); - return NF_ACCEPT; -} - -static const struct nf_hook_ops ipv4_synproxy_ops[] = { - { - .hook = ipv4_synproxy_hook, - .pf = NFPROTO_IPV4, - .hooknum = NF_INET_LOCAL_IN, - .priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1, - }, - { - .hook = ipv4_synproxy_hook, - .pf = NFPROTO_IPV4, - .hooknum = NF_INET_POST_ROUTING, - .priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1, - }, -}; - static int synproxy_tg4_check(const struct xt_tgchk_param *par) { struct synproxy_net *snet = synproxy_pernet(par->net); @@ -452,13 +76,10 @@ static int synproxy_tg4_check(const struct xt_tgchk_param *par) if (err) return err; - if (snet->hook_ref4 == 0) { - err = nf_register_net_hooks(par->net, ipv4_synproxy_ops, - ARRAY_SIZE(ipv4_synproxy_ops)); - if (err) { - nf_ct_netns_put(par->net, par->family); - return err; - } + err = nf_synproxy_ipv4_init(snet, par->net); + if (err) { + nf_ct_netns_put(par->net, par->family); + return err; } snet->hook_ref4++; @@ -469,10 +90,7 @@ static void synproxy_tg4_destroy(const struct xt_tgdtor_param *par) { struct synproxy_net *snet = synproxy_pernet(par->net); - snet->hook_ref4--; - if (snet->hook_ref4 == 0) - nf_unregister_net_hooks(par->net, ipv4_synproxy_ops, - ARRAY_SIZE(ipv4_synproxy_ops)); + nf_synproxy_ipv4_fini(snet, par->net); nf_ct_netns_put(par->net, par->family); } -- cgit v1.2.3