diff options
Diffstat (limited to 'net/netfilter/nf_conntrack_proto_icmp.c')
-rw-r--r-- | net/netfilter/nf_conntrack_proto_icmp.c | 383 |
1 files changed, 383 insertions, 0 deletions
diff --git a/net/netfilter/nf_conntrack_proto_icmp.c b/net/netfilter/nf_conntrack_proto_icmp.c new file mode 100644 index 000000000..b38b7164a --- /dev/null +++ b/net/netfilter/nf_conntrack_proto_icmp.c @@ -0,0 +1,383 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* (C) 1999-2001 Paul `Rusty' Russell + * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> + * (C) 2006-2010 Patrick McHardy <kaber@trash.net> + */ + +#include <linux/types.h> +#include <linux/timer.h> +#include <linux/netfilter.h> +#include <linux/in.h> +#include <linux/icmp.h> +#include <linux/seq_file.h> +#include <net/ip.h> +#include <net/checksum.h> +#include <linux/netfilter_ipv4.h> +#include <net/netfilter/nf_conntrack_tuple.h> +#include <net/netfilter/nf_conntrack_l4proto.h> +#include <net/netfilter/nf_conntrack_core.h> +#include <net/netfilter/nf_conntrack_timeout.h> +#include <net/netfilter/nf_conntrack_zones.h> +#include <net/netfilter/nf_log.h> + +#include "nf_internals.h" + +static const unsigned int nf_ct_icmp_timeout = 30*HZ; + +bool icmp_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff, + struct net *net, struct nf_conntrack_tuple *tuple) +{ + const struct icmphdr *hp; + struct icmphdr _hdr; + + hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr); + if (hp == NULL) + return false; + + tuple->dst.u.icmp.type = hp->type; + tuple->src.u.icmp.id = hp->un.echo.id; + tuple->dst.u.icmp.code = hp->code; + + return true; +} + +/* Add 1; spaces filled with 0. */ +static const u_int8_t invmap[] = { + [ICMP_ECHO] = ICMP_ECHOREPLY + 1, + [ICMP_ECHOREPLY] = ICMP_ECHO + 1, + [ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1, + [ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1, + [ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1, + [ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1, + [ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1, + [ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1 +}; + +bool nf_conntrack_invert_icmp_tuple(struct nf_conntrack_tuple *tuple, + const struct nf_conntrack_tuple *orig) +{ + if (orig->dst.u.icmp.type >= sizeof(invmap) || + !invmap[orig->dst.u.icmp.type]) + return false; + + tuple->src.u.icmp.id = orig->src.u.icmp.id; + tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1; + tuple->dst.u.icmp.code = orig->dst.u.icmp.code; + return true; +} + +/* Returns verdict for packet, or -1 for invalid. */ +int nf_conntrack_icmp_packet(struct nf_conn *ct, + struct sk_buff *skb, + enum ip_conntrack_info ctinfo, + const struct nf_hook_state *state) +{ + /* Do not immediately delete the connection after the first + successful reply to avoid excessive conntrackd traffic + and also to handle correctly ICMP echo reply duplicates. */ + unsigned int *timeout = nf_ct_timeout_lookup(ct); + static const u_int8_t valid_new[] = { + [ICMP_ECHO] = 1, + [ICMP_TIMESTAMP] = 1, + [ICMP_INFO_REQUEST] = 1, + [ICMP_ADDRESS] = 1 + }; + + if (state->pf != NFPROTO_IPV4) + return -NF_ACCEPT; + + if (ct->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new) || + !valid_new[ct->tuplehash[0].tuple.dst.u.icmp.type]) { + /* Can't create a new ICMP `conn' with this. */ + pr_debug("icmp: can't create new conn with type %u\n", + ct->tuplehash[0].tuple.dst.u.icmp.type); + nf_ct_dump_tuple_ip(&ct->tuplehash[0].tuple); + return -NF_ACCEPT; + } + + if (!timeout) + timeout = &nf_icmp_pernet(nf_ct_net(ct))->timeout; + + nf_ct_refresh_acct(ct, ctinfo, skb, *timeout); + return NF_ACCEPT; +} + +/* Check inner header is related to any of the existing connections */ +int nf_conntrack_inet_error(struct nf_conn *tmpl, struct sk_buff *skb, + unsigned int dataoff, + const struct nf_hook_state *state, + u8 l4proto, union nf_inet_addr *outer_daddr) +{ + struct nf_conntrack_tuple innertuple, origtuple; + const struct nf_conntrack_tuple_hash *h; + const struct nf_conntrack_zone *zone; + enum ip_conntrack_info ctinfo; + struct nf_conntrack_zone tmp; + union nf_inet_addr *ct_daddr; + enum ip_conntrack_dir dir; + struct nf_conn *ct; + + WARN_ON(skb_nfct(skb)); + zone = nf_ct_zone_tmpl(tmpl, skb, &tmp); + + /* Are they talking about one of our connections? */ + if (!nf_ct_get_tuplepr(skb, dataoff, + state->pf, state->net, &origtuple)) + return -NF_ACCEPT; + + /* Ordinarily, we'd expect the inverted tupleproto, but it's + been preserved inside the ICMP. */ + if (!nf_ct_invert_tuple(&innertuple, &origtuple)) + return -NF_ACCEPT; + + h = nf_conntrack_find_get(state->net, zone, &innertuple); + if (!h) + return -NF_ACCEPT; + + /* Consider: A -> T (=This machine) -> B + * Conntrack entry will look like this: + * Original: A->B + * Reply: B->T (SNAT case) OR A + * + * When this function runs, we got packet that looks like this: + * iphdr|icmphdr|inner_iphdr|l4header (tcp, udp, ..). + * + * Above nf_conntrack_find_get() makes lookup based on inner_hdr, + * so we should expect that destination of the found connection + * matches outer header destination address. + * + * In above example, we can consider these two cases: + * 1. Error coming in reply direction from B or M (middle box) to + * T (SNAT case) or A. + * Inner saddr will be B, dst will be T or A. + * The found conntrack will be reply tuple (B->T/A). + * 2. Error coming in original direction from A or M to B. + * Inner saddr will be A, inner daddr will be B. + * The found conntrack will be original tuple (A->B). + * + * In both cases, conntrack[dir].dst == inner.dst. + * + * A bogus packet could look like this: + * Inner: B->T + * Outer: B->X (other machine reachable by T). + * + * In this case, lookup yields connection A->B and will + * set packet from B->X as *RELATED*, even though no connection + * from X was ever seen. + */ + ct = nf_ct_tuplehash_to_ctrack(h); + dir = NF_CT_DIRECTION(h); + ct_daddr = &ct->tuplehash[dir].tuple.dst.u3; + if (!nf_inet_addr_cmp(outer_daddr, ct_daddr)) { + if (state->pf == AF_INET) { + nf_l4proto_log_invalid(skb, state, + l4proto, + "outer daddr %pI4 != inner %pI4", + &outer_daddr->ip, &ct_daddr->ip); + } else if (state->pf == AF_INET6) { + nf_l4proto_log_invalid(skb, state, + l4proto, + "outer daddr %pI6 != inner %pI6", + &outer_daddr->ip6, &ct_daddr->ip6); + } + nf_ct_put(ct); + return -NF_ACCEPT; + } + + ctinfo = IP_CT_RELATED; + if (dir == IP_CT_DIR_REPLY) + ctinfo += IP_CT_IS_REPLY; + + /* Update skb to refer to this connection */ + nf_ct_set(skb, ct, ctinfo); + return NF_ACCEPT; +} + +static void icmp_error_log(const struct sk_buff *skb, + const struct nf_hook_state *state, + const char *msg) +{ + nf_l4proto_log_invalid(skb, state, IPPROTO_ICMP, "%s", msg); +} + +/* Small and modified version of icmp_rcv */ +int nf_conntrack_icmpv4_error(struct nf_conn *tmpl, + struct sk_buff *skb, unsigned int dataoff, + const struct nf_hook_state *state) +{ + union nf_inet_addr outer_daddr; + const struct icmphdr *icmph; + struct icmphdr _ih; + + /* Not enough header? */ + icmph = skb_header_pointer(skb, dataoff, sizeof(_ih), &_ih); + if (icmph == NULL) { + icmp_error_log(skb, state, "short packet"); + return -NF_ACCEPT; + } + + /* See nf_conntrack_proto_tcp.c */ + if (state->net->ct.sysctl_checksum && + state->hook == NF_INET_PRE_ROUTING && + nf_ip_checksum(skb, state->hook, dataoff, IPPROTO_ICMP)) { + icmp_error_log(skb, state, "bad hw icmp checksum"); + return -NF_ACCEPT; + } + + /* + * 18 is the highest 'known' ICMP type. Anything else is a mystery + * + * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently + * discarded. + */ + if (icmph->type > NR_ICMP_TYPES) { + icmp_error_log(skb, state, "invalid icmp type"); + return -NF_ACCEPT; + } + + /* Need to track icmp error message? */ + if (!icmp_is_err(icmph->type)) + return NF_ACCEPT; + + memset(&outer_daddr, 0, sizeof(outer_daddr)); + outer_daddr.ip = ip_hdr(skb)->daddr; + + dataoff += sizeof(*icmph); + return nf_conntrack_inet_error(tmpl, skb, dataoff, state, + IPPROTO_ICMP, &outer_daddr); +} + +#if IS_ENABLED(CONFIG_NF_CT_NETLINK) + +#include <linux/netfilter/nfnetlink.h> +#include <linux/netfilter/nfnetlink_conntrack.h> + +static int icmp_tuple_to_nlattr(struct sk_buff *skb, + const struct nf_conntrack_tuple *t) +{ + if (nla_put_be16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id) || + nla_put_u8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type) || + nla_put_u8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code)) + goto nla_put_failure; + return 0; + +nla_put_failure: + return -1; +} + +static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = { + [CTA_PROTO_ICMP_TYPE] = { .type = NLA_U8 }, + [CTA_PROTO_ICMP_CODE] = { .type = NLA_U8 }, + [CTA_PROTO_ICMP_ID] = { .type = NLA_U16 }, +}; + +static int icmp_nlattr_to_tuple(struct nlattr *tb[], + struct nf_conntrack_tuple *tuple, + u_int32_t flags) +{ + if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_TYPE)) { + if (!tb[CTA_PROTO_ICMP_TYPE]) + return -EINVAL; + + tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]); + if (tuple->dst.u.icmp.type >= sizeof(invmap) || + !invmap[tuple->dst.u.icmp.type]) + return -EINVAL; + } + + if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_CODE)) { + if (!tb[CTA_PROTO_ICMP_CODE]) + return -EINVAL; + + tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]); + } + + if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_ID)) { + if (!tb[CTA_PROTO_ICMP_ID]) + return -EINVAL; + + tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]); + } + + return 0; +} + +static unsigned int icmp_nlattr_tuple_size(void) +{ + static unsigned int size __read_mostly; + + if (!size) + size = nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1); + + return size; +} +#endif + +#ifdef CONFIG_NF_CONNTRACK_TIMEOUT + +#include <linux/netfilter/nfnetlink.h> +#include <linux/netfilter/nfnetlink_cttimeout.h> + +static int icmp_timeout_nlattr_to_obj(struct nlattr *tb[], + struct net *net, void *data) +{ + unsigned int *timeout = data; + struct nf_icmp_net *in = nf_icmp_pernet(net); + + if (tb[CTA_TIMEOUT_ICMP_TIMEOUT]) { + if (!timeout) + timeout = &in->timeout; + *timeout = + ntohl(nla_get_be32(tb[CTA_TIMEOUT_ICMP_TIMEOUT])) * HZ; + } else if (timeout) { + /* Set default ICMP timeout. */ + *timeout = in->timeout; + } + return 0; +} + +static int +icmp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data) +{ + const unsigned int *timeout = data; + + if (nla_put_be32(skb, CTA_TIMEOUT_ICMP_TIMEOUT, htonl(*timeout / HZ))) + goto nla_put_failure; + return 0; + +nla_put_failure: + return -ENOSPC; +} + +static const struct nla_policy +icmp_timeout_nla_policy[CTA_TIMEOUT_ICMP_MAX+1] = { + [CTA_TIMEOUT_ICMP_TIMEOUT] = { .type = NLA_U32 }, +}; +#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ + +void nf_conntrack_icmp_init_net(struct net *net) +{ + struct nf_icmp_net *in = nf_icmp_pernet(net); + + in->timeout = nf_ct_icmp_timeout; +} + +const struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp = +{ + .l4proto = IPPROTO_ICMP, +#if IS_ENABLED(CONFIG_NF_CT_NETLINK) + .tuple_to_nlattr = icmp_tuple_to_nlattr, + .nlattr_tuple_size = icmp_nlattr_tuple_size, + .nlattr_to_tuple = icmp_nlattr_to_tuple, + .nla_policy = icmp_nla_policy, +#endif +#ifdef CONFIG_NF_CONNTRACK_TIMEOUT + .ctnl_timeout = { + .nlattr_to_obj = icmp_timeout_nlattr_to_obj, + .obj_to_nlattr = icmp_timeout_obj_to_nlattr, + .nlattr_max = CTA_TIMEOUT_ICMP_MAX, + .obj_size = sizeof(unsigned int), + .nla_policy = icmp_timeout_nla_policy, + }, +#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ +}; |