diff options
Diffstat (limited to 'kernel/net/bridge/netfilter/nft_reject_bridge.c')
-rw-r--r-- | kernel/net/bridge/netfilter/nft_reject_bridge.c | 418 |
1 files changed, 418 insertions, 0 deletions
diff --git a/kernel/net/bridge/netfilter/nft_reject_bridge.c b/kernel/net/bridge/netfilter/nft_reject_bridge.c new file mode 100644 index 000000000..858d84856 --- /dev/null +++ b/kernel/net/bridge/netfilter/nft_reject_bridge.c @@ -0,0 +1,418 @@ +/* + * Copyright (c) 2014 Pablo Neira Ayuso <pablo@netfilter.org> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/module.h> +#include <linux/netlink.h> +#include <linux/netfilter.h> +#include <linux/netfilter/nf_tables.h> +#include <net/netfilter/nf_tables.h> +#include <net/netfilter/nft_reject.h> +#include <net/netfilter/nf_tables_bridge.h> +#include <net/netfilter/ipv4/nf_reject.h> +#include <net/netfilter/ipv6/nf_reject.h> +#include <linux/ip.h> +#include <net/ip.h> +#include <net/ip6_checksum.h> +#include <linux/netfilter_bridge.h> +#include <linux/netfilter_ipv6.h> +#include "../br_private.h" + +static void nft_reject_br_push_etherhdr(struct sk_buff *oldskb, + struct sk_buff *nskb) +{ + struct ethhdr *eth; + + eth = (struct ethhdr *)skb_push(nskb, ETH_HLEN); + skb_reset_mac_header(nskb); + ether_addr_copy(eth->h_source, eth_hdr(oldskb)->h_dest); + ether_addr_copy(eth->h_dest, eth_hdr(oldskb)->h_source); + eth->h_proto = eth_hdr(oldskb)->h_proto; + skb_pull(nskb, ETH_HLEN); +} + +/* We cannot use oldskb->dev, it can be either bridge device (NF_BRIDGE INPUT) + * or the bridge port (NF_BRIDGE PREROUTING). + */ +static void nft_reject_br_send_v4_tcp_reset(struct sk_buff *oldskb, + const struct net_device *dev, + int hook) +{ + struct sk_buff *nskb; + struct iphdr *niph; + const struct tcphdr *oth; + struct tcphdr _oth; + + if (!nft_bridge_iphdr_validate(oldskb)) + return; + + oth = nf_reject_ip_tcphdr_get(oldskb, &_oth, hook); + if (!oth) + return; + + nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) + + LL_MAX_HEADER, GFP_ATOMIC); + if (!nskb) + return; + + skb_reserve(nskb, LL_MAX_HEADER); + niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_TCP, + sysctl_ip_default_ttl); + nf_reject_ip_tcphdr_put(nskb, oldskb, oth); + niph->ttl = sysctl_ip_default_ttl; + niph->tot_len = htons(nskb->len); + ip_send_check(niph); + + nft_reject_br_push_etherhdr(oldskb, nskb); + + br_deliver(br_port_get_rcu(dev), nskb); +} + +static void nft_reject_br_send_v4_unreach(struct sk_buff *oldskb, + const struct net_device *dev, + int hook, u8 code) +{ + struct sk_buff *nskb; + struct iphdr *niph; + struct icmphdr *icmph; + unsigned int len; + void *payload; + __wsum csum; + u8 proto; + + if (oldskb->csum_bad || !nft_bridge_iphdr_validate(oldskb)) + return; + + /* IP header checks: fragment. */ + if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET)) + return; + + /* RFC says return as much as we can without exceeding 576 bytes. */ + len = min_t(unsigned int, 536, oldskb->len); + + if (!pskb_may_pull(oldskb, len)) + return; + + if (pskb_trim_rcsum(oldskb, ntohs(ip_hdr(oldskb)->tot_len))) + return; + + if (ip_hdr(oldskb)->protocol == IPPROTO_TCP || + ip_hdr(oldskb)->protocol == IPPROTO_UDP) + proto = ip_hdr(oldskb)->protocol; + else + proto = 0; + + if (!skb_csum_unnecessary(oldskb) && + nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), proto)) + return; + + nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct icmphdr) + + LL_MAX_HEADER + len, GFP_ATOMIC); + if (!nskb) + return; + + skb_reserve(nskb, LL_MAX_HEADER); + niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_ICMP, + sysctl_ip_default_ttl); + + skb_reset_transport_header(nskb); + icmph = (struct icmphdr *)skb_put(nskb, sizeof(struct icmphdr)); + memset(icmph, 0, sizeof(*icmph)); + icmph->type = ICMP_DEST_UNREACH; + icmph->code = code; + + payload = skb_put(nskb, len); + memcpy(payload, skb_network_header(oldskb), len); + + csum = csum_partial((void *)icmph, len + sizeof(struct icmphdr), 0); + icmph->checksum = csum_fold(csum); + + niph->tot_len = htons(nskb->len); + ip_send_check(niph); + + nft_reject_br_push_etherhdr(oldskb, nskb); + + br_deliver(br_port_get_rcu(dev), nskb); +} + +static void nft_reject_br_send_v6_tcp_reset(struct net *net, + struct sk_buff *oldskb, + const struct net_device *dev, + int hook) +{ + struct sk_buff *nskb; + const struct tcphdr *oth; + struct tcphdr _oth; + unsigned int otcplen; + struct ipv6hdr *nip6h; + + if (!nft_bridge_ip6hdr_validate(oldskb)) + return; + + oth = nf_reject_ip6_tcphdr_get(oldskb, &_oth, &otcplen, hook); + if (!oth) + return; + + nskb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(struct tcphdr) + + LL_MAX_HEADER, GFP_ATOMIC); + if (!nskb) + return; + + skb_reserve(nskb, LL_MAX_HEADER); + nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP, + net->ipv6.devconf_all->hop_limit); + nf_reject_ip6_tcphdr_put(nskb, oldskb, oth, otcplen); + nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr)); + + nft_reject_br_push_etherhdr(oldskb, nskb); + + br_deliver(br_port_get_rcu(dev), nskb); +} + +static bool reject6_br_csum_ok(struct sk_buff *skb, int hook) +{ + const struct ipv6hdr *ip6h = ipv6_hdr(skb); + int thoff; + __be16 fo; + u8 proto = ip6h->nexthdr; + + if (skb->csum_bad) + return false; + + if (skb_csum_unnecessary(skb)) + return true; + + if (ip6h->payload_len && + pskb_trim_rcsum(skb, ntohs(ip6h->payload_len) + sizeof(*ip6h))) + return false; + + thoff = ipv6_skip_exthdr(skb, ((u8*)(ip6h+1) - skb->data), &proto, &fo); + if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0) + return false; + + return nf_ip6_checksum(skb, hook, thoff, proto) == 0; +} + +static void nft_reject_br_send_v6_unreach(struct net *net, + struct sk_buff *oldskb, + const struct net_device *dev, + int hook, u8 code) +{ + struct sk_buff *nskb; + struct ipv6hdr *nip6h; + struct icmp6hdr *icmp6h; + unsigned int len; + void *payload; + + if (!nft_bridge_ip6hdr_validate(oldskb)) + return; + + /* Include "As much of invoking packet as possible without the ICMPv6 + * packet exceeding the minimum IPv6 MTU" in the ICMP payload. + */ + len = min_t(unsigned int, 1220, oldskb->len); + + if (!pskb_may_pull(oldskb, len)) + return; + + if (!reject6_br_csum_ok(oldskb, hook)) + return; + + nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct icmp6hdr) + + LL_MAX_HEADER + len, GFP_ATOMIC); + if (!nskb) + return; + + skb_reserve(nskb, LL_MAX_HEADER); + nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_ICMPV6, + net->ipv6.devconf_all->hop_limit); + + skb_reset_transport_header(nskb); + icmp6h = (struct icmp6hdr *)skb_put(nskb, sizeof(struct icmp6hdr)); + memset(icmp6h, 0, sizeof(*icmp6h)); + icmp6h->icmp6_type = ICMPV6_DEST_UNREACH; + icmp6h->icmp6_code = code; + + payload = skb_put(nskb, len); + memcpy(payload, skb_network_header(oldskb), len); + nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr)); + + icmp6h->icmp6_cksum = + csum_ipv6_magic(&nip6h->saddr, &nip6h->daddr, + nskb->len - sizeof(struct ipv6hdr), + IPPROTO_ICMPV6, + csum_partial(icmp6h, + nskb->len - sizeof(struct ipv6hdr), + 0)); + + nft_reject_br_push_etherhdr(oldskb, nskb); + + br_deliver(br_port_get_rcu(dev), nskb); +} + +static void nft_reject_bridge_eval(const struct nft_expr *expr, + struct nft_regs *regs, + const struct nft_pktinfo *pkt) +{ + struct nft_reject *priv = nft_expr_priv(expr); + struct net *net = dev_net((pkt->in != NULL) ? pkt->in : pkt->out); + const unsigned char *dest = eth_hdr(pkt->skb)->h_dest; + + if (is_broadcast_ether_addr(dest) || + is_multicast_ether_addr(dest)) + goto out; + + switch (eth_hdr(pkt->skb)->h_proto) { + case htons(ETH_P_IP): + switch (priv->type) { + case NFT_REJECT_ICMP_UNREACH: + nft_reject_br_send_v4_unreach(pkt->skb, pkt->in, + pkt->ops->hooknum, + priv->icmp_code); + break; + case NFT_REJECT_TCP_RST: + nft_reject_br_send_v4_tcp_reset(pkt->skb, pkt->in, + pkt->ops->hooknum); + break; + case NFT_REJECT_ICMPX_UNREACH: + nft_reject_br_send_v4_unreach(pkt->skb, pkt->in, + pkt->ops->hooknum, + nft_reject_icmp_code(priv->icmp_code)); + break; + } + break; + case htons(ETH_P_IPV6): + switch (priv->type) { + case NFT_REJECT_ICMP_UNREACH: + nft_reject_br_send_v6_unreach(net, pkt->skb, pkt->in, + pkt->ops->hooknum, + priv->icmp_code); + break; + case NFT_REJECT_TCP_RST: + nft_reject_br_send_v6_tcp_reset(net, pkt->skb, pkt->in, + pkt->ops->hooknum); + break; + case NFT_REJECT_ICMPX_UNREACH: + nft_reject_br_send_v6_unreach(net, pkt->skb, pkt->in, + pkt->ops->hooknum, + nft_reject_icmpv6_code(priv->icmp_code)); + break; + } + break; + default: + /* No explicit way to reject this protocol, drop it. */ + break; + } +out: + regs->verdict.code = NF_DROP; +} + +static int nft_reject_bridge_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_BR_PRE_ROUTING) | + (1 << NF_BR_LOCAL_IN)); +} + +static int nft_reject_bridge_init(const struct nft_ctx *ctx, + const struct nft_expr *expr, + const struct nlattr * const tb[]) +{ + struct nft_reject *priv = nft_expr_priv(expr); + int icmp_code, err; + + err = nft_reject_bridge_validate(ctx, expr, NULL); + if (err < 0) + return err; + + if (tb[NFTA_REJECT_TYPE] == NULL) + return -EINVAL; + + priv->type = ntohl(nla_get_be32(tb[NFTA_REJECT_TYPE])); + switch (priv->type) { + case NFT_REJECT_ICMP_UNREACH: + case NFT_REJECT_ICMPX_UNREACH: + if (tb[NFTA_REJECT_ICMP_CODE] == NULL) + return -EINVAL; + + icmp_code = nla_get_u8(tb[NFTA_REJECT_ICMP_CODE]); + if (priv->type == NFT_REJECT_ICMPX_UNREACH && + icmp_code > NFT_REJECT_ICMPX_MAX) + return -EINVAL; + + priv->icmp_code = icmp_code; + break; + case NFT_REJECT_TCP_RST: + break; + default: + return -EINVAL; + } + return 0; +} + +static int nft_reject_bridge_dump(struct sk_buff *skb, + const struct nft_expr *expr) +{ + const struct nft_reject *priv = nft_expr_priv(expr); + + if (nla_put_be32(skb, NFTA_REJECT_TYPE, htonl(priv->type))) + goto nla_put_failure; + + switch (priv->type) { + case NFT_REJECT_ICMP_UNREACH: + case NFT_REJECT_ICMPX_UNREACH: + if (nla_put_u8(skb, NFTA_REJECT_ICMP_CODE, priv->icmp_code)) + goto nla_put_failure; + break; + default: + break; + } + + return 0; + +nla_put_failure: + return -1; +} + +static struct nft_expr_type nft_reject_bridge_type; +static const struct nft_expr_ops nft_reject_bridge_ops = { + .type = &nft_reject_bridge_type, + .size = NFT_EXPR_SIZE(sizeof(struct nft_reject)), + .eval = nft_reject_bridge_eval, + .init = nft_reject_bridge_init, + .dump = nft_reject_bridge_dump, + .validate = nft_reject_bridge_validate, +}; + +static struct nft_expr_type nft_reject_bridge_type __read_mostly = { + .family = NFPROTO_BRIDGE, + .name = "reject", + .ops = &nft_reject_bridge_ops, + .policy = nft_reject_policy, + .maxattr = NFTA_REJECT_MAX, + .owner = THIS_MODULE, +}; + +static int __init nft_reject_bridge_module_init(void) +{ + return nft_register_expr(&nft_reject_bridge_type); +} + +static void __exit nft_reject_bridge_module_exit(void) +{ + nft_unregister_expr(&nft_reject_bridge_type); +} + +module_init(nft_reject_bridge_module_init); +module_exit(nft_reject_bridge_module_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>"); +MODULE_ALIAS_NFT_AF_EXPR(AF_BRIDGE, "reject"); |