From patchwork Wed Jun 26 10:44:15 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Fernando F. Mancera" X-Patchwork-Id: 1122676 X-Patchwork-Delegate: pablo@netfilter.org Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netfilter-devel-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=riseup.net Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; secure) header.d=riseup.net header.i=@riseup.net header.b="b1A+pfow"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45Yfpl6WyNz9sCJ for ; Wed, 26 Jun 2019 20:46:39 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727154AbfFZKqg (ORCPT ); Wed, 26 Jun 2019 06:46:36 -0400 Received: from mx1.riseup.net ([198.252.153.129]:41720 "EHLO mx1.riseup.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725930AbfFZKqg (ORCPT ); Wed, 26 Jun 2019 06:46:36 -0400 Received: from bell.riseup.net (bell-pn.riseup.net [10.0.1.178]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (Client CN "*.riseup.net", Issuer "COMODO RSA Domain Validation Secure Server CA" (verified OK)) by mx1.riseup.net (Postfix) with ESMTPS id 231E51A084E for ; Wed, 26 Jun 2019 03:46:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=riseup.net; s=squak; t=1561545995; bh=qEgIo33T4Q3101+ffnkgTUjpXqGTUkwV8EZ1kUiM89c=; h=From:To:Cc:Subject:Date:From; b=b1A+pfowFX3VhcrXrBDMydc4kPAh+MJKqRXHCtjkcztWC94LmWK1STEtltsgDmD4A Qzb4zUI+U/D+6UbjaTtTMIzkSqbJ7Nf7iSBB6C90ch0Qx4qHDGqVTmDAxmr6rL8ewc m9UoIb8RNmuIruMExDZVJ2rY1Cxz9ESUYD6/yEfU= X-Riseup-User-ID: 289F3F0FF7113B556EF66B3A623D636D20C4F1D0ACD8DC3157991644C28FD953 Received: from [127.0.0.1] (localhost [127.0.0.1]) by bell.riseup.net (Postfix) with ESMTPSA id 2DDEE223C33; Wed, 26 Jun 2019 03:46:34 -0700 (PDT) From: Fernando Fernandez Mancera To: netfilter-devel@vger.kernel.org Cc: Fernando Fernandez Mancera Subject: [PATCH nf-next v5] netfilter: nf_tables: Add SYNPROXY support Date: Wed, 26 Jun 2019 12:44:15 +0200 Message-Id: <20190626104413.813-1-ffmancera@riseup.net> MIME-Version: 1.0 Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org Add SYNPROXY module support in nf_tables. It preserves the behaviour of the SYNPROXY target of iptables but structured in a different way to propose improvements in the future. Signed-off-by: Fernando Fernandez Mancera --- v1: initial patch v2: add IPV6 module checks v3: move common eval parts into a function, reorder init function v4: remove NFT_CONTINUE, place error check close to function call in eval v5: avoid #if IS_ENABLED(..) for ipv6 init and fini and remove refcount bumps. --- include/net/netfilter/nf_conntrack_synproxy.h | 1 + include/net/netfilter/nf_synproxy.h | 6 + include/uapi/linux/netfilter/nf_SYNPROXY.h | 4 + include/uapi/linux/netfilter/nf_tables.h | 17 ++ net/netfilter/Kconfig | 11 + net/netfilter/Makefile | 1 + net/netfilter/nft_synproxy.c | 289 ++++++++++++++++++ 7 files changed, 329 insertions(+) create mode 100644 net/netfilter/nft_synproxy.c diff --git a/include/net/netfilter/nf_conntrack_synproxy.h b/include/net/netfilter/nf_conntrack_synproxy.h index c5659dcf5b1a..8f00125b06f4 100644 --- a/include/net/netfilter/nf_conntrack_synproxy.h +++ b/include/net/netfilter/nf_conntrack_synproxy.h @@ -2,6 +2,7 @@ #ifndef _NF_CONNTRACK_SYNPROXY_H #define _NF_CONNTRACK_SYNPROXY_H +#include #include struct nf_conn_synproxy { diff --git a/include/net/netfilter/nf_synproxy.h b/include/net/netfilter/nf_synproxy.h index 3e8b3f03b687..355e46dc6ab5 100644 --- a/include/net/netfilter/nf_synproxy.h +++ b/include/net/netfilter/nf_synproxy.h @@ -37,8 +37,14 @@ bool synproxy_recv_client_ack_ipv6(struct net *net, const struct sk_buff *skb, unsigned int ipv6_synproxy_hook(void *priv, struct sk_buff *skb, const struct nf_hook_state *nhs); + int nf_synproxy_ipv6_init(struct synproxy_net *snet, struct net *net); void nf_synproxy_ipv6_fini(struct synproxy_net *snet, struct net *net); +#else +static inline int +nf_synproxy_ipv6_init(struct synproxy_net *snet, struct net *net) { return 0; } +static inline void +nf_synproxy_ipv6_fini(struct synproxy_net *snet, struct net *net) {}; #endif /* CONFIG_IPV6 */ #endif /* _NF_SYNPROXY_SHARED_H */ diff --git a/include/uapi/linux/netfilter/nf_SYNPROXY.h b/include/uapi/linux/netfilter/nf_SYNPROXY.h index 068d1b3a6f06..6f3791c8946f 100644 --- a/include/uapi/linux/netfilter/nf_SYNPROXY.h +++ b/include/uapi/linux/netfilter/nf_SYNPROXY.h @@ -9,6 +9,10 @@ #define NF_SYNPROXY_OPT_SACK_PERM 0x04 #define NF_SYNPROXY_OPT_TIMESTAMP 0x08 #define NF_SYNPROXY_OPT_ECN 0x10 +#define NF_SYNPROXY_OPT_MASK (NF_SYNPROXY_OPT_MSS | \ + NF_SYNPROXY_OPT_WSCALE | \ + NF_SYNPROXY_OPT_SACK_PERM | \ + NF_SYNPROXY_OPT_TIMESTAMP) struct nf_synproxy_info { __u8 options; diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h index c6c8ec5c7c00..302c25af17d7 100644 --- a/include/uapi/linux/netfilter/nf_tables.h +++ b/include/uapi/linux/netfilter/nf_tables.h @@ -1551,6 +1551,23 @@ enum nft_osf_flags { NFT_OSF_F_VERSION = (1 << 0), }; +/** + * enum nft_synproxy_attributes - nf_tables synproxy expression + * netlink attributes + * + * @NFTA_SYNPROXY_MSS: mss value sent to the backend (NLA_U16) + * @NFTA_SYNPROXY_WSCALE: wscale value sent to the backend (NLA_U8) + * @NFTA_SYNPROXY_FLAGS: flags (NLA_U32) + */ +enum nft_synproxy_attributes { + NFTA_SYNPROXY_UNSPEC, + NFTA_SYNPROXY_MSS, + NFTA_SYNPROXY_WSCALE, + NFTA_SYNPROXY_FLAGS, + __NFTA_SYNPROXY_MAX, +}; +#define NFTA_SYNPROXY_MAX (__NFTA_SYNPROXY_MAX - 1) + /** * enum nft_device_attributes - nf_tables device netlink attributes * diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig index 21025c2c605b..d59742408d9b 100644 --- a/net/netfilter/Kconfig +++ b/net/netfilter/Kconfig @@ -651,6 +651,17 @@ config NFT_TPROXY help This makes transparent proxy support available in nftables. +config NFT_SYNPROXY + tristate "Netfilter nf_tables SYNPROXY expression support" + depends on NF_CONNTRACK && NETFILTER_ADVANCED + select NETFILTER_SYNPROXY + select SYN_COOKIES + help + The SYNPROXY expression allows you to intercept TCP connections and + establish them using syncookies before they are passed on to the + server. This allows to avoid conntrack and server resource usage + during SYN-flood attacks. + if NF_TABLES_NETDEV config NF_DUP_NETDEV diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile index 72cca6b48960..deada20975ff 100644 --- a/net/netfilter/Makefile +++ b/net/netfilter/Makefile @@ -110,6 +110,7 @@ obj-$(CONFIG_NFT_SOCKET) += nft_socket.o obj-$(CONFIG_NFT_OSF) += nft_osf.o obj-$(CONFIG_NFT_TPROXY) += nft_tproxy.o obj-$(CONFIG_NFT_XFRM) += nft_xfrm.o +obj-$(CONFIG_NFT_SYNPROXY) += nft_synproxy.o obj-$(CONFIG_NFT_NAT) += nft_chain_nat.o diff --git a/net/netfilter/nft_synproxy.c b/net/netfilter/nft_synproxy.c new file mode 100644 index 000000000000..b79a54927123 --- /dev/null +++ b/net/netfilter/nft_synproxy.c @@ -0,0 +1,289 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +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; + return; + } 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; + return; + } 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 != 0 && (flags & NF_SYNPROXY_OPT_MASK) == 0) + return -EINVAL; + 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, ntohs(priv->info.mss)) || + nla_put_u8(skb, NFTA_SYNPROXY_WSCALE, priv->info.wscale) || + nla_put_be32(skb, NFTA_SYNPROXY_FLAGS, ntohl(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_OSF_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 "); +MODULE_ALIAS_NFT_EXPR("synproxy");