diff options
Diffstat (limited to 'net/netfilter/nft_synproxy.c')
| -rw-r--r-- | net/netfilter/nft_synproxy.c | 287 |
1 files changed, 287 insertions, 0 deletions
diff --git a/net/netfilter/nft_synproxy.c b/net/netfilter/nft_synproxy.c new file mode 100644 index 000000000000..80060ade8a5b --- /dev/null +++ b/net/netfilter/nft_synproxy.c @@ -0,0 +1,287 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <linux/types.h> +#include <net/ip.h> +#include <net/tcp.h> +#include <net/netlink.h> +#include <net/netfilter/nf_tables.h> +#include <net/netfilter/nf_conntrack.h> +#include <net/netfilter/nf_conntrack_synproxy.h> +#include <net/netfilter/nf_synproxy.h> +#include <linux/netfilter/nf_tables.h> +#include <linux/netfilter/nf_synproxy.h> + +struct nft_synproxy { + struct nf_synproxy_info info; +}; + +static const struct nla_policy nft_synproxy_policy[NFTA_SYNPROXY_MAX + 1] = { + [NFTA_SYNPROXY_MSS] = { .type = NLA_U16 }, + [NFTA_SYNPROXY_WSCALE] = { .type = NLA_U8 }, + [NFTA_SYNPROXY_FLAGS] = { .type = NLA_U32 }, +}; + +static void nft_synproxy_tcp_options(struct synproxy_options *opts, + const struct tcphdr *tcp, + struct synproxy_net *snet, + struct nf_synproxy_info *info, + struct nft_synproxy *priv) +{ + this_cpu_inc(snet->stats->syn_received); + if (tcp->ece && tcp->cwr) + opts->options |= NF_SYNPROXY_OPT_ECN; + + opts->options &= priv->info.options; + if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP) + synproxy_init_timestamp_cookie(info, opts); + else + opts->options &= ~(NF_SYNPROXY_OPT_WSCALE | + NF_SYNPROXY_OPT_SACK_PERM | + NF_SYNPROXY_OPT_ECN); +} + +static void nft_synproxy_eval_v4(const struct nft_expr *expr, + struct nft_regs *regs, + const struct nft_pktinfo *pkt, + const struct tcphdr *tcp, + struct tcphdr *_tcph, + struct synproxy_options *opts) +{ + struct nft_synproxy *priv = nft_expr_priv(expr); + struct nf_synproxy_info info = priv->info; + struct net *net = nft_net(pkt); + struct synproxy_net *snet = synproxy_pernet(net); + struct sk_buff *skb = pkt->skb; + + if (tcp->syn) { + /* Initial SYN from client */ + nft_synproxy_tcp_options(opts, tcp, snet, &info, priv); + synproxy_send_client_synack(net, skb, tcp, opts); + consume_skb(skb); + regs->verdict.code = NF_STOLEN; + } else if (tcp->ack) { + /* ACK from client */ + if (synproxy_recv_client_ack(net, skb, tcp, opts, + ntohl(tcp->seq))) { + consume_skb(skb); + regs->verdict.code = NF_STOLEN; + } else { + regs->verdict.code = NF_DROP; + } + } +} + +#if IS_ENABLED(CONFIG_NF_TABLES_IPV6) +static void nft_synproxy_eval_v6(const struct nft_expr *expr, + struct nft_regs *regs, + const struct nft_pktinfo *pkt, + const struct tcphdr *tcp, + struct tcphdr *_tcph, + struct synproxy_options *opts) +{ + struct nft_synproxy *priv = nft_expr_priv(expr); + struct nf_synproxy_info info = priv->info; + struct net *net = nft_net(pkt); + struct synproxy_net *snet = synproxy_pernet(net); + struct sk_buff *skb = pkt->skb; + + if (tcp->syn) { + /* Initial SYN from client */ + nft_synproxy_tcp_options(opts, tcp, snet, &info, priv); + synproxy_send_client_synack_ipv6(net, skb, tcp, opts); + consume_skb(skb); + regs->verdict.code = NF_STOLEN; + } else if (tcp->ack) { + /* ACK from client */ + if (synproxy_recv_client_ack_ipv6(net, skb, tcp, opts, + ntohl(tcp->seq))) { + consume_skb(skb); + regs->verdict.code = NF_STOLEN; + } else { + regs->verdict.code = NF_DROP; + } + } +} +#endif /* CONFIG_NF_TABLES_IPV6*/ + +static void nft_synproxy_eval(const struct nft_expr *expr, + struct nft_regs *regs, + const struct nft_pktinfo *pkt) +{ + struct synproxy_options opts = {}; + struct sk_buff *skb = pkt->skb; + int thoff = pkt->xt.thoff; + const struct tcphdr *tcp; + struct tcphdr _tcph; + + if (pkt->tprot != IPPROTO_TCP) { + regs->verdict.code = NFT_BREAK; + return; + } + + if (nf_ip_checksum(skb, nft_hook(pkt), thoff, IPPROTO_TCP)) { + regs->verdict.code = NF_DROP; + return; + } + + tcp = skb_header_pointer(skb, pkt->xt.thoff, + sizeof(struct tcphdr), + &_tcph); + if (!tcp) { + regs->verdict.code = NF_DROP; + return; + } + + if (!synproxy_parse_options(skb, thoff, tcp, &opts)) { + regs->verdict.code = NF_DROP; + return; + } + + switch (skb->protocol) { + case htons(ETH_P_IP): + nft_synproxy_eval_v4(expr, regs, pkt, tcp, &_tcph, &opts); + return; +#if IS_ENABLED(CONFIG_NF_TABLES_IPV6) + case htons(ETH_P_IPV6): + nft_synproxy_eval_v6(expr, regs, pkt, tcp, &_tcph, &opts); + return; +#endif + } + regs->verdict.code = NFT_BREAK; +} + +static int nft_synproxy_init(const struct nft_ctx *ctx, + const struct nft_expr *expr, + const struct nlattr * const tb[]) +{ + struct synproxy_net *snet = synproxy_pernet(ctx->net); + struct nft_synproxy *priv = nft_expr_priv(expr); + u32 flags; + int err; + + if (tb[NFTA_SYNPROXY_MSS]) + priv->info.mss = ntohs(nla_get_be16(tb[NFTA_SYNPROXY_MSS])); + if (tb[NFTA_SYNPROXY_WSCALE]) + priv->info.wscale = nla_get_u8(tb[NFTA_SYNPROXY_WSCALE]); + if (tb[NFTA_SYNPROXY_FLAGS]) { + flags = ntohl(nla_get_be32(tb[NFTA_SYNPROXY_FLAGS])); + if (flags & ~NF_SYNPROXY_OPT_MASK) + return -EOPNOTSUPP; + priv->info.options = flags; + } + + err = nf_ct_netns_get(ctx->net, ctx->family); + if (err) + return err; + + switch (ctx->family) { + case NFPROTO_IPV4: + err = nf_synproxy_ipv4_init(snet, ctx->net); + if (err) + goto nf_ct_failure; + break; +#if IS_ENABLED(CONFIG_NF_TABLES_IPV6) + case NFPROTO_IPV6: + err = nf_synproxy_ipv6_init(snet, ctx->net); + if (err) + goto nf_ct_failure; + break; +#endif + case NFPROTO_INET: + case NFPROTO_BRIDGE: + err = nf_synproxy_ipv4_init(snet, ctx->net); + if (err) + goto nf_ct_failure; + err = nf_synproxy_ipv6_init(snet, ctx->net); + if (err) + goto nf_ct_failure; + break; + } + + return 0; + +nf_ct_failure: + nf_ct_netns_put(ctx->net, ctx->family); + return err; +} + +static void nft_synproxy_destroy(const struct nft_ctx *ctx, + const struct nft_expr *expr) +{ + struct synproxy_net *snet = synproxy_pernet(ctx->net); + + switch (ctx->family) { + case NFPROTO_IPV4: + nf_synproxy_ipv4_fini(snet, ctx->net); + break; +#if IS_ENABLED(CONFIG_NF_TABLES_IPV6) + case NFPROTO_IPV6: + nf_synproxy_ipv6_fini(snet, ctx->net); + break; +#endif + case NFPROTO_INET: + case NFPROTO_BRIDGE: + nf_synproxy_ipv4_fini(snet, ctx->net); + nf_synproxy_ipv6_fini(snet, ctx->net); + break; + } + nf_ct_netns_put(ctx->net, ctx->family); +} + +static int nft_synproxy_dump(struct sk_buff *skb, const struct nft_expr *expr) +{ + const struct nft_synproxy *priv = nft_expr_priv(expr); + + if (nla_put_be16(skb, NFTA_SYNPROXY_MSS, htons(priv->info.mss)) || + nla_put_u8(skb, NFTA_SYNPROXY_WSCALE, priv->info.wscale) || + nla_put_be32(skb, NFTA_SYNPROXY_FLAGS, htonl(priv->info.options))) + goto nla_put_failure; + + return 0; + +nla_put_failure: + return -1; +} + +static int nft_synproxy_validate(const struct nft_ctx *ctx, + const struct nft_expr *expr, + const struct nft_data **data) +{ + return nft_chain_validate_hooks(ctx->chain, (1 << NF_INET_LOCAL_IN) | + (1 << NF_INET_FORWARD)); +} + +static struct nft_expr_type nft_synproxy_type; +static const struct nft_expr_ops nft_synproxy_ops = { + .eval = nft_synproxy_eval, + .size = NFT_EXPR_SIZE(sizeof(struct nft_synproxy)), + .init = nft_synproxy_init, + .destroy = nft_synproxy_destroy, + .dump = nft_synproxy_dump, + .type = &nft_synproxy_type, + .validate = nft_synproxy_validate, +}; + +static struct nft_expr_type nft_synproxy_type __read_mostly = { + .ops = &nft_synproxy_ops, + .name = "synproxy", + .owner = THIS_MODULE, + .policy = nft_synproxy_policy, + .maxattr = NFTA_SYNPROXY_MAX, +}; + +static int __init nft_synproxy_module_init(void) +{ + return nft_register_expr(&nft_synproxy_type); +} + +static void __exit nft_synproxy_module_exit(void) +{ + return nft_unregister_expr(&nft_synproxy_type); +} + +module_init(nft_synproxy_module_init); +module_exit(nft_synproxy_module_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>"); +MODULE_ALIAS_NFT_EXPR("synproxy"); |