From 20710b3b81895c89e92bcc32ce85c0bede1171f8 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Tue, 20 Mar 2018 12:33:51 +0100 Subject: [PATCH] netfilter: ctnetlink: synproxy support This patch exposes synproxy information per-conntrack. Moreover, send sequence adjustment events once server sends us the SYN,ACK packet, so we can synchronize the sequence adjustment too for packets going as reply from the server, as part of the synproxy logic. Signed-off-by: Pablo Neira Ayuso --- include/uapi/linux/netfilter/nf_conntrack_common.h | 1 + include/uapi/linux/netfilter/nfnetlink_conntrack.h | 10 +++ net/ipv4/netfilter/ipt_SYNPROXY.c | 8 +- net/ipv6/netfilter/ip6t_SYNPROXY.c | 8 +- net/netfilter/nf_conntrack_netlink.c | 87 +++++++++++++++++++++- 5 files changed, 109 insertions(+), 5 deletions(-) diff --git a/include/uapi/linux/netfilter/nf_conntrack_common.h b/include/uapi/linux/netfilter/nf_conntrack_common.h index 9574bd4..c712eb6 100644 --- a/include/uapi/linux/netfilter/nf_conntrack_common.h +++ b/include/uapi/linux/netfilter/nf_conntrack_common.h @@ -129,6 +129,7 @@ enum ip_conntrack_events { IPCT_NATSEQADJ = IPCT_SEQADJ, IPCT_SECMARK, /* new security mark has been set */ IPCT_LABEL, /* new connlabel has been set */ + IPCT_SYNPROXY, /* synproxy has been set */ #ifdef __KERNEL__ __IPCT_MAX #endif diff --git a/include/uapi/linux/netfilter/nfnetlink_conntrack.h b/include/uapi/linux/netfilter/nfnetlink_conntrack.h index 7397e02..7798711 100644 --- a/include/uapi/linux/netfilter/nfnetlink_conntrack.h +++ b/include/uapi/linux/netfilter/nfnetlink_conntrack.h @@ -54,6 +54,7 @@ enum ctattr_type { CTA_MARK_MASK, CTA_LABELS, CTA_LABELS_MASK, + CTA_SYNPROXY, __CTA_MAX }; #define CTA_MAX (__CTA_MAX - 1) @@ -190,6 +191,15 @@ enum ctattr_natseq { }; #define CTA_NAT_SEQ_MAX (__CTA_NAT_SEQ_MAX - 1) +enum ctattr_synproxy { + CTA_SYNPROXY_UNSPEC, + CTA_SYNPROXY_ISN, + CTA_SYNPROXY_ITS, + CTA_SYNPROXY_TSOFF, + __CTA_SYNPROXY_MAX, +}; +#define CTA_SYNPROXY_MAX (__CTA_SYNPROXY_MAX - 1) + enum ctattr_expect { CTA_EXPECT_UNSPEC, CTA_EXPECT_MASTER, diff --git a/net/ipv4/netfilter/ipt_SYNPROXY.c b/net/ipv4/netfilter/ipt_SYNPROXY.c index f75fc6b..690b17e 100644 --- a/net/ipv4/netfilter/ipt_SYNPROXY.c +++ b/net/ipv4/netfilter/ipt_SYNPROXY.c @@ -16,6 +16,7 @@ #include #include #include +#include static struct iphdr * synproxy_build_ip(struct net *net, struct sk_buff *skb, __be32 saddr, @@ -384,6 +385,8 @@ static unsigned int ipv4_synproxy_hook(void *priv, 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) @@ -392,8 +395,10 @@ static unsigned int ipv4_synproxy_hook(void *priv, if (!synproxy_parse_options(skb, thoff, th, &opts)) return NF_DROP; - if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP) + 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 | @@ -403,6 +408,7 @@ static unsigned int ipv4_synproxy_hook(void *priv, 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); diff --git a/net/ipv6/netfilter/ip6t_SYNPROXY.c b/net/ipv6/netfilter/ip6t_SYNPROXY.c index 437af8c..cb6d42b0 100644 --- a/net/ipv6/netfilter/ip6t_SYNPROXY.c +++ b/net/ipv6/netfilter/ip6t_SYNPROXY.c @@ -18,6 +18,7 @@ #include #include #include +#include static struct ipv6hdr * synproxy_build_ip(struct net *net, struct sk_buff *skb, @@ -405,6 +406,8 @@ static unsigned int ipv6_synproxy_hook(void *priv, 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) @@ -413,8 +416,10 @@ static unsigned int ipv6_synproxy_hook(void *priv, if (!synproxy_parse_options(skb, thoff, th, &opts)) return NF_DROP; - if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP) + 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 | @@ -424,6 +429,7 @@ static unsigned int ipv6_synproxy_hook(void *priv, 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); diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c index 8884d30..11ef85a 100644 --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -440,6 +440,31 @@ err: return -1; } +static int ctnetlink_dump_ct_synproxy(struct sk_buff *skb, struct nf_conn *ct) +{ + struct nf_conn_synproxy *synproxy = nfct_synproxy(ct); + struct nlattr *nest_parms; + + if (!synproxy) + return 0; + + nest_parms = nla_nest_start(skb, CTA_SYNPROXY | NLA_F_NESTED); + if (!nest_parms) + goto nla_put_failure; + + if (nla_put_be32(skb, CTA_SYNPROXY_ISN, htonl(synproxy->isn)) || + nla_put_be32(skb, CTA_SYNPROXY_ITS, htonl(synproxy->its)) || + nla_put_be32(skb, CTA_SYNPROXY_TSOFF, htonl(synproxy->tsoff))) + goto nla_put_failure; + + nla_nest_end(skb, nest_parms); + + return 0; + +nla_put_failure: + return -1; +} + static int ctnetlink_dump_id(struct sk_buff *skb, const struct nf_conn *ct) { if (nla_put_be32(skb, CTA_ID, htonl((unsigned long)ct))) @@ -518,7 +543,8 @@ ctnetlink_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type, ctnetlink_dump_id(skb, ct) < 0 || ctnetlink_dump_use(skb, ct) < 0 || ctnetlink_dump_master(skb, ct) < 0 || - ctnetlink_dump_ct_seq_adj(skb, ct) < 0) + ctnetlink_dump_ct_seq_adj(skb, ct) < 0 || + ctnetlink_dump_ct_synproxy(skb, ct) < 0) goto nla_put_failure; nlmsg_end(skb, nlh); @@ -730,6 +756,10 @@ ctnetlink_conntrack_event(unsigned int events, struct nf_ct_event *item) if (events & (1 << IPCT_SEQADJ) && ctnetlink_dump_ct_seq_adj(skb, ct) < 0) goto nla_put_failure; + + if (events & (1 << IPCT_SYNPROXY) && + ctnetlink_dump_ct_synproxy(skb, ct) < 0) + goto nla_put_failure; } #ifdef CONFIG_NF_CONNTRACK_MARK @@ -1689,6 +1719,39 @@ err: return ret; } +static const struct nla_policy synproxy_policy[CTA_SYNPROXY_MAX + 1] = { + [CTA_SYNPROXY_ISN] = { .type = NLA_U32 }, + [CTA_SYNPROXY_ITS] = { .type = NLA_U32 }, + [CTA_SYNPROXY_TSOFF] = { .type = NLA_U32 }, +}; + +static int ctnetlink_change_synproxy(struct nf_conn *ct, + const struct nlattr * const cda[]) +{ + struct nf_conn_synproxy *synproxy = nfct_synproxy(ct); + struct nlattr *tb[CTA_SYNPROXY_MAX + 1]; + int err; + + if (!synproxy) + return 0; + + err = nla_parse_nested(tb, CTA_SYNPROXY_MAX, cda[CTA_SYNPROXY], + synproxy_policy, NULL); + if (err < 0) + return err; + + if (!tb[CTA_SYNPROXY_ISN] || + !tb[CTA_SYNPROXY_ITS] || + !tb[CTA_SYNPROXY_TSOFF]) + return -EINVAL; + + synproxy->isn = ntohl(nla_get_be32(tb[CTA_SYNPROXY_ISN])); + synproxy->its = ntohl(nla_get_be32(tb[CTA_SYNPROXY_ITS])); + synproxy->tsoff = ntohl(nla_get_be32(tb[CTA_SYNPROXY_TSOFF])); + + return 0; +} + static int ctnetlink_attach_labels(struct nf_conn *ct, const struct nlattr * const cda[]) { @@ -1759,6 +1822,12 @@ ctnetlink_change_conntrack(struct nf_conn *ct, return err; } + if (cda[CTA_SYNPROXY]) { + err = ctnetlink_change_synproxy(ct, cda); + if (err < 0) + return err; + } + if (cda[CTA_LABELS]) { err = ctnetlink_attach_labels(ct, cda); if (err < 0) @@ -1880,6 +1949,12 @@ ctnetlink_create_conntrack(struct net *net, goto err2; } + if (cda[CTA_SYNPROXY]) { + err = ctnetlink_change_synproxy(ct, cda); + if (err < 0) + goto err2; + } + #if defined(CONFIG_NF_CONNTRACK_MARK) if (cda[CTA_MARK]) ct->mark = ntohl(nla_get_be32(cda[CTA_MARK])); @@ -1991,7 +2066,9 @@ static int ctnetlink_new_conntrack(struct net *net, struct sock *ctnl, (1 << IPCT_HELPER) | (1 << IPCT_PROTOINFO) | (1 << IPCT_SEQADJ) | - (1 << IPCT_MARK) | events, + (1 << IPCT_MARK) | + (1 << IPCT_SYNPROXY) | + events, ct, NETLINK_CB(skb).portid, nlmsg_report(nlh)); nf_ct_put(ct); @@ -2012,7 +2089,8 @@ static int ctnetlink_new_conntrack(struct net *net, struct sock *ctnl, (1 << IPCT_LABEL) | (1 << IPCT_PROTOINFO) | (1 << IPCT_SEQADJ) | - (1 << IPCT_MARK), + (1 << IPCT_MARK) | + (1 << IPCT_SYNPROXY), ct, NETLINK_CB(skb).portid, nlmsg_report(nlh)); } @@ -2282,6 +2360,9 @@ static int __ctnetlink_glue_build(struct sk_buff *skb, struct nf_conn *ct) ctnetlink_dump_ct_seq_adj(skb, ct) < 0) goto nla_put_failure; + if (ctnetlink_dump_ct_synproxy(skb, ct) < 0) + goto nla_put_failure; + #ifdef CONFIG_NF_CONNTRACK_MARK if (ct->mark && ctnetlink_dump_mark(skb, ct) < 0) goto nla_put_failure; -- 2.7.4