/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include #include #include #include #include #include #include #include #include "sd-netlink.h" #include "alloc-util.h" #include "firewall-util.h" #include "firewall-util-private.h" #include "in-addr-util.h" #include "macro.h" #include "netlink-internal.h" #include "netlink-util.h" #include "socket-util.h" #include "time-util.h" #define NFT_SYSTEMD_DNAT_MAP_NAME "map_port_ipport" #define NFT_SYSTEMD_TABLE_NAME "io.systemd.nat" #define NFT_SYSTEMD_MASQ_SET_NAME "masq_saddr" #define NFNL_DEFAULT_TIMEOUT_USECS (1ULL * USEC_PER_SEC) #define UDP_DPORT_OFFSET 2 static sd_netlink_message **netlink_message_unref_many(sd_netlink_message **m) { if (!m) return NULL; /* This does not free array. The end of the array must be NULL. */ for (sd_netlink_message **p = m; *p; p++) *p = sd_netlink_message_unref(*p); return m; } DEFINE_TRIVIAL_CLEANUP_FUNC(sd_netlink_message**, netlink_message_unref_many); static int nfnl_open_expr_container(sd_netlink_message *m, const char *name) { int r; assert(m); assert(name); r = sd_netlink_message_open_array(m, NFTA_LIST_ELEM); if (r < 0) return r; return sd_netlink_message_open_container_union(m, NFTA_EXPR_DATA, name); } static int nfnl_close_expr_container(sd_netlink_message *m) { int r; assert(m); r = sd_netlink_message_close_container(m); /* NFTA_EXPR_DATA */ if (r < 0) return r; return sd_netlink_message_close_container(m); /* NFTA_LIST_ELEM */ } static int nfnl_add_expr_fib( sd_netlink_message *m, uint32_t nft_fib_flags, enum nft_fib_result result, enum nft_registers dreg) { int r; assert(m); r = nfnl_open_expr_container(m, "fib"); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_FIB_FLAGS, htobe32(nft_fib_flags)); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_FIB_RESULT, htobe32(result)); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_FIB_DREG, htobe32(dreg)); if (r < 0) return r; return nfnl_close_expr_container(m); } static int nfnl_add_expr_meta( sd_netlink_message *m, enum nft_meta_keys key, enum nft_registers dreg) { int r; assert(m); r = nfnl_open_expr_container(m, "meta"); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_META_KEY, htobe32(key)); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_META_DREG, htobe32(dreg)); if (r < 0) return r; return nfnl_close_expr_container(m); } static int nfnl_add_expr_payload( sd_netlink_message *m, enum nft_payload_bases pb, uint32_t offset, uint32_t len, enum nft_registers dreg) { int r; assert(m); r = nfnl_open_expr_container(m, "payload"); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_PAYLOAD_DREG, htobe32(dreg)); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_PAYLOAD_BASE, htobe32(pb)); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_PAYLOAD_OFFSET, htobe32(offset)); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_PAYLOAD_LEN, htobe32(len)); if (r < 0) return r; return nfnl_close_expr_container(m); } static int nfnl_add_expr_lookup( sd_netlink_message *m, const char *set_name, enum nft_registers sreg, enum nft_registers dreg) { int r; assert(m); assert(set_name); r = nfnl_open_expr_container(m, "lookup"); if (r < 0) return r; r = sd_netlink_message_append_string(m, NFTA_LOOKUP_SET, set_name); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_LOOKUP_SREG, htobe32(sreg)); if (r < 0) return r; if (dreg != 0) { r = sd_netlink_message_append_u32(m, NFTA_LOOKUP_DREG, htobe32(dreg)); if (r < 0) return r; } return nfnl_close_expr_container(m); } static int nfnl_add_expr_cmp( sd_netlink_message *m, enum nft_cmp_ops cmp_op, enum nft_registers sreg, const void *data, size_t dlen) { int r; assert(m); assert(data); r = nfnl_open_expr_container(m, "cmp"); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_CMP_OP, htobe32(cmp_op)); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_CMP_SREG, htobe32(sreg)); if (r < 0) return r; r = sd_netlink_message_append_container_data(m, NFTA_CMP_DATA, NFTA_DATA_VALUE, data, dlen); if (r < 0) return r; return nfnl_close_expr_container(m); } static int nfnl_add_expr_bitwise( sd_netlink_message *m, enum nft_registers sreg, enum nft_registers dreg, const void *and, const void *xor, uint32_t len) { int r; assert(m); assert(and); assert(xor); r = nfnl_open_expr_container(m, "bitwise"); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_BITWISE_SREG, htobe32(sreg)); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_BITWISE_DREG, htobe32(dreg)); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_BITWISE_LEN, htobe32(len)); if (r < 0) return r; r = sd_netlink_message_append_container_data(m, NFTA_BITWISE_MASK, NFTA_DATA_VALUE, and, len); if (r < 0) return r; r = sd_netlink_message_append_container_data(m, NFTA_BITWISE_XOR, NFTA_DATA_VALUE, xor, len); if (r < 0) return r; return nfnl_close_expr_container(m); } static int nfnl_add_expr_dnat( sd_netlink_message *m, int family, enum nft_registers areg, enum nft_registers preg) { int r; assert(m); r = nfnl_open_expr_container(m, "nat"); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_NAT_TYPE, htobe32(NFT_NAT_DNAT)); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_NAT_FAMILY, htobe32(family)); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_NAT_REG_ADDR_MIN, htobe32(areg)); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_NAT_REG_PROTO_MIN, htobe32(preg)); if (r < 0) return r; return nfnl_close_expr_container(m); } static int nfnl_add_expr_masq(sd_netlink_message *m) { int r; r = sd_netlink_message_open_array(m, NFTA_LIST_ELEM); if (r < 0) return r; r = sd_netlink_message_append_string(m, NFTA_EXPR_NAME, "masq"); if (r < 0) return r; return sd_netlink_message_close_container(m); /* NFTA_LIST_ELEM */ } static int sd_nfnl_message_new_masq_rule( sd_netlink *nfnl, sd_netlink_message **ret, int family, const char *chain) { _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL; int r; /* -t nat -A POSTROUTING -p protocol -s source/pflen -o out_interface -d destination/pflen -j MASQUERADE */ assert(nfnl); assert(ret); assert(IN_SET(family, AF_INET, AF_INET6)); assert(chain); r = sd_nfnl_nft_message_new_rule(nfnl, &m, family, NFT_SYSTEMD_TABLE_NAME, chain); if (r < 0) return r; r = sd_netlink_message_open_container(m, NFTA_RULE_EXPRESSIONS); if (r < 0) return r; /* 1st statement: ip saddr @masq_saddr. Place iph->saddr in reg1, resp. ipv6 in reg1..reg4. */ if (family == AF_INET) r = nfnl_add_expr_payload(m, NFT_PAYLOAD_NETWORK_HEADER, offsetof(struct iphdr, saddr), sizeof(uint32_t), NFT_REG32_01); else r = nfnl_add_expr_payload(m, NFT_PAYLOAD_NETWORK_HEADER, offsetof(struct ip6_hdr, ip6_src.s6_addr), sizeof(struct in6_addr), NFT_REG32_01); if (r < 0) return r; /* 1st statement: use reg1 content to make lookup in @masq_saddr set. */ r = nfnl_add_expr_lookup(m, NFT_SYSTEMD_MASQ_SET_NAME, NFT_REG32_01, 0); if (r < 0) return r; /* 2nd statement: masq. Only executed by kernel if the previous lookup was successful. */ r = nfnl_add_expr_masq(m); if (r < 0) return r; r = sd_netlink_message_close_container(m); /* NFTA_RULE_EXPRESSIONS */ if (r < 0) return r; *ret = TAKE_PTR(m); return 0; } static int sd_nfnl_message_new_dnat_rule_pre( sd_netlink *nfnl, sd_netlink_message **ret, int family, const char *chain) { _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL; enum nft_registers proto_reg; uint32_t local = RTN_LOCAL; int r; /* -t nat -A PREROUTING -p protocol --dport local_port -i in_interface -s source/pflen * -d destination/pflen -j DNAT --to-destination remote_addr:remote_port */ assert(nfnl); assert(ret); assert(IN_SET(family, AF_INET, AF_INET6)); assert(chain); r = sd_nfnl_nft_message_new_rule(nfnl, &m, family, NFT_SYSTEMD_TABLE_NAME, chain); if (r < 0) return r; r = sd_netlink_message_open_container(m, NFTA_RULE_EXPRESSIONS); if (r < 0) return r; /* 1st statement: fib daddr type local */ r = nfnl_add_expr_fib(m, NFTA_FIB_F_DADDR, NFT_FIB_RESULT_ADDRTYPE, NFT_REG32_01); if (r < 0) return r; /* 1st statement (cont.): compare RTN_LOCAL */ r = nfnl_add_expr_cmp(m, NFT_CMP_EQ, NFT_REG32_01, &local, sizeof(local)); if (r < 0) return r; /* 2nd statement: lookup local port in map, fetch address:dport to map to */ r = nfnl_add_expr_meta(m, NFT_META_L4PROTO, NFT_REG32_01); if (r < 0) return r; r = nfnl_add_expr_payload(m, NFT_PAYLOAD_TRANSPORT_HEADER, UDP_DPORT_OFFSET, sizeof(uint16_t), NFT_REG32_02); if (r < 0) return r; /* 3rd statement: lookup 'l4proto . dport', e.g. 'tcp . 22' as key and * store address and port for the dnat mapping in REG1/REG2. */ r = nfnl_add_expr_lookup(m, NFT_SYSTEMD_DNAT_MAP_NAME, NFT_REG32_01, NFT_REG32_01); if (r < 0) return r; proto_reg = family == AF_INET ? NFT_REG32_02 : NFT_REG32_05; r = nfnl_add_expr_dnat(m, family, NFT_REG32_01, proto_reg); if (r < 0) return r; r = sd_netlink_message_close_container(m); /* NFTA_RULE_EXPRESSIONS */ if (r < 0) return r; *ret = TAKE_PTR(m); return 0; } static int sd_nfnl_message_new_dnat_rule_out( sd_netlink *nfnl, sd_netlink_message **ret, int family, const char *chain) { static const uint32_t zero = 0, one = 1; _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL; enum nft_registers proto_reg; int r; assert(nfnl); assert(ret); assert(IN_SET(family, AF_INET, AF_INET6)); assert(chain); r = sd_nfnl_nft_message_new_rule(nfnl, &m, family, NFT_SYSTEMD_TABLE_NAME, chain); if (r < 0) return r; r = sd_netlink_message_open_container(m, NFTA_RULE_EXPRESSIONS); if (r < 0) return r; /* 1st statement: exclude 127.0.0.1/8: ip daddr != 127.0.0.1/8, resp. avoid ::1 */ if (family == AF_INET) { uint32_t lonet = htobe32(UINT32_C(0x7F000000)), lomask = htobe32(UINT32_C(0xff000000)); r = nfnl_add_expr_payload(m, NFT_PAYLOAD_NETWORK_HEADER, offsetof(struct iphdr, daddr), sizeof(lonet), NFT_REG32_01); if (r < 0) return r; /* 1st statement (cont.): bitops/prefix */ r = nfnl_add_expr_bitwise(m, NFT_REG32_01, NFT_REG32_01, &lomask, &zero, sizeof(lomask)); if (r < 0) return r; /* 1st statement (cont.): compare reg1 with 127/8 */ r = nfnl_add_expr_cmp(m, NFT_CMP_NEQ, NFT_REG32_01, &lonet, sizeof(lonet)); } else { struct in6_addr loaddr = IN6ADDR_LOOPBACK_INIT; r = nfnl_add_expr_payload(m, NFT_PAYLOAD_NETWORK_HEADER, offsetof(struct ip6_hdr, ip6_dst.s6_addr), sizeof(loaddr), NFT_REG32_01); if (r < 0) return r; r = nfnl_add_expr_cmp(m, NFT_CMP_NEQ, NFT_REG32_01, &loaddr, sizeof(loaddr)); } if (r < 0) return r; /* 2nd statement: meta oif lo */ r = nfnl_add_expr_meta(m, NFT_META_OIF, NFT_REG32_01); if (r < 0) return r; /* 2nd statement (cont.): compare to lo ifindex (1) */ r = nfnl_add_expr_cmp(m, NFT_CMP_EQ, NFT_REG32_01, &one, sizeof(one)); if (r < 0) return r; /* 3rd statement: meta l4proto . th dport dnat ip . port to map @map_port_ipport */ r = nfnl_add_expr_meta(m, NFT_META_L4PROTO, NFT_REG32_01); if (r < 0) return r; /* 3rd statement (cont): store the port number in reg2 */ r = nfnl_add_expr_payload(m, NFT_PAYLOAD_TRANSPORT_HEADER, UDP_DPORT_OFFSET, sizeof(uint16_t), NFT_REG32_02); if (r < 0) return r; /* 3rd statement (cont): use reg1 and reg2 and retrieve * the new destination ip and port number. * * reg1 and reg2 are clobbered and will then contain the new * address/port number. */ r = nfnl_add_expr_lookup(m, NFT_SYSTEMD_DNAT_MAP_NAME, NFT_REG32_01, NFT_REG32_01); if (r < 0) return r; /* 4th statement: dnat connection to address/port retrieved by the * preceding expression. */ proto_reg = family == AF_INET ? NFT_REG32_02 : NFT_REG32_05; r = nfnl_add_expr_dnat(m, family, NFT_REG32_01, proto_reg); if (r < 0) return r; r = sd_netlink_message_close_container(m); /* NFTA_RULE_EXPRESSIONS */ if (r < 0) return r; *ret = TAKE_PTR(m); return 0; } static int nft_new_set( struct sd_netlink *nfnl, sd_netlink_message **ret, int family, const char *set_name, uint32_t set_id, uint32_t flags, uint32_t type, uint32_t klen) { _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL; int r; assert(nfnl); assert(ret); assert(IN_SET(family, AF_INET, AF_INET6)); assert(set_name); r = sd_nfnl_nft_message_new_set(nfnl, &m, family, NFT_SYSTEMD_TABLE_NAME, set_name, set_id, klen); if (r < 0) return r; if (flags != 0) { r = sd_netlink_message_append_u32(m, NFTA_SET_FLAGS, htobe32(flags)); if (r < 0) return r; } r = sd_netlink_message_append_u32(m, NFTA_SET_KEY_TYPE, htobe32(type)); if (r < 0) return r; *ret = TAKE_PTR(m); return r; } static int nft_new_map( struct sd_netlink *nfnl, sd_netlink_message **ret, int family, const char *set_name, uint32_t set_id, uint32_t flags, uint32_t type, uint32_t klen, uint32_t dtype, uint32_t dlen) { _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL; int r; assert(nfnl); assert(ret); assert(IN_SET(family, AF_INET, AF_INET6)); assert(set_name); r = nft_new_set(nfnl, &m, family, set_name, set_id, flags | NFT_SET_MAP, type, klen); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_SET_DATA_TYPE, htobe32(dtype)); if (r < 0) return r; r = sd_netlink_message_append_u32(m, NFTA_SET_DATA_LEN, htobe32(dlen)); if (r < 0) return r; *ret = TAKE_PTR(m); return 0; } static int nft_add_element( sd_netlink *nfnl, sd_netlink_message **ret, int family, const char *set_name, const void *key, uint32_t klen, const void *data, uint32_t dlen) { _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL; int r; assert(nfnl); assert(ret); assert(IN_SET(family, AF_INET, AF_INET6)); assert(set_name); assert(key); assert(data); /* * Ideally there would be an API that provides: * * 1) an init function to add the main ruleset skeleton * 2) a function that populates the sets with all known address/port pairs to s/dnat for * 3) a function that can remove address/port pairs again. * * At this time, the existing API is used which is built on a * 'add/delete a rule' paradigm. * * This replicated here and each element gets added to the set * one-by-one. */ r = sd_nfnl_nft_message_new_setelems(nfnl, &m, /* add = */ true, family, NFT_SYSTEMD_TABLE_NAME, set_name); if (r < 0) return r; r = sd_netlink_message_open_container(m, NFTA_SET_ELEM_LIST_ELEMENTS); if (r < 0) return r; r = sd_nfnl_nft_message_append_setelem(m, 0, key, klen, data, dlen, 0); if (r < 0) return r; /* could theoretically append more set elements to add here */ r = sd_netlink_message_close_container(m); /* NFTA_SET_ELEM_LIST_ELEMENTS */ if (r < 0) return r; *ret = TAKE_PTR(m); return 0; } static int nft_del_element( sd_netlink *nfnl, sd_netlink_message **ret, int family, const char *set_name, const void *key, uint32_t klen, const void *data, uint32_t dlen) { _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL; int r; assert(nfnl); assert(ret); assert(IN_SET(family, AF_INET, AF_INET6)); assert(set_name); assert(key); assert(data); r = sd_nfnl_nft_message_new_setelems(nfnl, &m, /* add = */ false, family, NFT_SYSTEMD_TABLE_NAME, set_name); if (r < 0) return r; r = sd_netlink_message_open_container(m, NFTA_SET_ELEM_LIST_ELEMENTS); if (r < 0) return r; r = sd_nfnl_nft_message_append_setelem(m, 0, key, klen, data, dlen, 0); if (r < 0) return r; r = sd_netlink_message_close_container(m); /* NFTA_SET_ELEM_LIST_ELEMENTS */ if (r < 0) return r; *ret = TAKE_PTR(m); return 0; } /* This is needed so 'nft' userspace tool can properly format the contents * of the set/map when someone uses 'nft' to inspect their content. * * The values cannot be changed, they are part of the nft tool type identifier ABI. */ #define TYPE_BITS 6 enum nft_key_types { TYPE_IPADDR = 7, TYPE_IP6ADDR = 8, TYPE_INET_PROTOCOL = 12, TYPE_INET_SERVICE = 13, }; static uint32_t concat_types2(enum nft_key_types a, enum nft_key_types b) { uint32_t type = (uint32_t)a; type <<= TYPE_BITS; type |= (uint32_t)b; return type; } static int fw_nftables_init_family(sd_netlink *nfnl, int family) { sd_netlink_message *messages[10] = {}; _unused_ _cleanup_(netlink_message_unref_manyp) sd_netlink_message **unref = messages; size_t msgcnt = 0, ip_type_size; uint32_t set_id = 0; int ip_type, r; assert(nfnl); assert(IN_SET(family, AF_INET, AF_INET6)); /* Set F_EXCL so table add fails if the table already exists. */ r = sd_nfnl_nft_message_new_table(nfnl, &messages[msgcnt++], family, NFT_SYSTEMD_TABLE_NAME); if (r < 0) return r; r = sd_nfnl_nft_message_new_basechain(nfnl, &messages[msgcnt++], family, NFT_SYSTEMD_TABLE_NAME, "prerouting", "nat", NF_INET_PRE_ROUTING, NF_IP_PRI_NAT_DST + 1); if (r < 0) return r; r = sd_nfnl_nft_message_new_basechain(nfnl, &messages[msgcnt++], family, NFT_SYSTEMD_TABLE_NAME, "output", "nat", NF_INET_LOCAL_OUT, NF_IP_PRI_NAT_DST + 1); if (r < 0) return r; r = sd_nfnl_nft_message_new_basechain(nfnl, &messages[msgcnt++], family, NFT_SYSTEMD_TABLE_NAME, "postrouting", "nat", NF_INET_POST_ROUTING, NF_IP_PRI_NAT_SRC + 1); if (r < 0) return r; if (family == AF_INET) { ip_type_size = sizeof(uint32_t); ip_type = TYPE_IPADDR; } else { assert(family == AF_INET6); ip_type_size = sizeof(struct in6_addr); ip_type = TYPE_IP6ADDR; } /* set to store ip address ranges we should masquerade for */ r = nft_new_set(nfnl, &messages[msgcnt++], family, NFT_SYSTEMD_MASQ_SET_NAME, ++set_id, NFT_SET_INTERVAL, ip_type, ip_type_size); if (r < 0) return r; /* * map to store ip address:port pair to dnat to. elements in concatenation * are rounded up to 4 bytes. * * Example: ip protocol . tcp daddr is sizeof(uint32_t) + sizeof(uint32_t), not * sizeof(uint8_t) + sizeof(uint16_t). */ r = nft_new_map(nfnl, &messages[msgcnt++], family, NFT_SYSTEMD_DNAT_MAP_NAME, ++set_id, 0, concat_types2(TYPE_INET_PROTOCOL, TYPE_INET_SERVICE), sizeof(uint32_t) * 2, concat_types2(ip_type, TYPE_INET_SERVICE), ip_type_size + sizeof(uint32_t)); if (r < 0) return r; r = sd_nfnl_message_new_dnat_rule_pre(nfnl, &messages[msgcnt++], family, "prerouting"); if (r < 0) return r; r = sd_nfnl_message_new_dnat_rule_out(nfnl, &messages[msgcnt++], family, "output"); if (r < 0) return r; r = sd_nfnl_message_new_masq_rule(nfnl, &messages[msgcnt++], family, "postrouting"); if (r < 0) return r; assert(msgcnt < ELEMENTSOF(messages)); r = sd_nfnl_call_batch(nfnl, messages, msgcnt, NFNL_DEFAULT_TIMEOUT_USECS, NULL); if (r < 0 && r != -EEXIST) return r; return 0; } int fw_nftables_init(FirewallContext *ctx) { _cleanup_(sd_netlink_unrefp) sd_netlink *nfnl = NULL; int r; assert(ctx); assert(!ctx->nfnl); r = sd_nfnl_socket_open(&nfnl); if (r < 0) return r; r = fw_nftables_init_family(nfnl, AF_INET); if (r < 0) return r; if (socket_ipv6_is_supported()) { r = fw_nftables_init_family(nfnl, AF_INET6); if (r < 0) log_debug_errno(r, "Failed to init ipv6 NAT: %m"); } ctx->nfnl = TAKE_PTR(nfnl); return 0; } void fw_nftables_exit(FirewallContext *ctx) { assert(ctx); ctx->nfnl = sd_netlink_unref(ctx->nfnl); } static int nft_message_append_setelem_iprange( sd_netlink_message *m, const union in_addr_union *source, unsigned int prefixlen) { uint32_t mask, start, end; unsigned int nplen; int r; assert(m); assert(source); assert(prefixlen <= 32); nplen = 32 - prefixlen; mask = (1U << nplen) - 1U; mask = htobe32(~mask); start = source->in.s_addr & mask; r = sd_netlink_message_open_container(m, NFTA_SET_ELEM_LIST_ELEMENTS); if (r < 0) return r; r = sd_nfnl_nft_message_append_setelem(m, 0, &start, sizeof(start), NULL, 0, 0); if (r < 0) return r; end = be32toh(start) + (1U << nplen); if (end < be32toh(start)) end = 0U; end = htobe32(end); r = sd_nfnl_nft_message_append_setelem(m, 1, &end, sizeof(end), NULL, 0, NFT_SET_ELEM_INTERVAL_END); if (r < 0) return r; return sd_netlink_message_close_container(m); /* NFTA_SET_ELEM_LIST_ELEMENTS */ } static int nft_message_append_setelem_ip6range( sd_netlink_message *m, const union in_addr_union *source, unsigned int prefixlen) { union in_addr_union start, end; int r; assert(m); assert(source); r = in_addr_prefix_range(AF_INET6, source, prefixlen, &start, &end); if (r < 0) return r; r = sd_netlink_message_open_container(m, NFTA_SET_ELEM_LIST_ELEMENTS); if (r < 0) return r; r = sd_nfnl_nft_message_append_setelem(m, 0, &start.in6, sizeof(start.in6), NULL, 0, 0); if (r < 0) return r; r = sd_nfnl_nft_message_append_setelem(m, 1, &end.in6, sizeof(end.in6), NULL, 0, NFT_SET_ELEM_INTERVAL_END); if (r < 0) return r; return sd_netlink_message_close_container(m); /* NFTA_SET_ELEM_LIST_ELEMENTS */ } static int fw_nftables_add_masquerade_internal( sd_netlink *nfnl, bool add, int af, const union in_addr_union *source, unsigned int source_prefixlen) { _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL; int r; assert(nfnl); assert(IN_SET(af, AF_INET, AF_INET6)); if (!source || source_prefixlen == 0) return -EINVAL; if (af == AF_INET6 && source_prefixlen < 8) return -EINVAL; r = sd_nfnl_nft_message_new_setelems(nfnl, &m, add, af, NFT_SYSTEMD_TABLE_NAME, NFT_SYSTEMD_MASQ_SET_NAME); if (r < 0) return r; if (af == AF_INET) r = nft_message_append_setelem_iprange(m, source, source_prefixlen); else r = nft_message_append_setelem_ip6range(m, source, source_prefixlen); if (r < 0) return r; return sd_nfnl_call_batch(nfnl, &m, 1, NFNL_DEFAULT_TIMEOUT_USECS, NULL); } int fw_nftables_add_masquerade( FirewallContext *ctx, bool add, int af, const union in_addr_union *source, unsigned int source_prefixlen) { int r; assert(ctx); assert(ctx->nfnl); assert(IN_SET(af, AF_INET, AF_INET6)); if (!socket_ipv6_is_supported() && af == AF_INET6) return -EOPNOTSUPP; r = fw_nftables_add_masquerade_internal(ctx->nfnl, add, af, source, source_prefixlen); if (r != -ENOENT) return r; /* When someone runs 'nft flush ruleset' in the same net namespace this will also tear down the * systemd nat table. * * Unlike iptables -t nat -F (which will remove all rules added by the systemd iptables * backend, iptables has builtin chains that cannot be deleted -- the next add operation will * 'just work'. * * In the nftables case, everything gets removed. The next add operation will yield -ENOENT. * * If we see -ENOENT on add, replay the initial table setup. If that works, re-do the add * operation. * * Note that this doesn't protect against external sabotage such as a * 'while true; nft flush ruleset; done'. There is nothing that could be done about that short * of extending the kernel to allow tables to be owned by stystemd-networkd and making them * non-deleteable except by the 'owning process'. */ r = fw_nftables_init_family(ctx->nfnl, af); if (r < 0) return r; return fw_nftables_add_masquerade_internal(ctx->nfnl, add, af, source, source_prefixlen); } static int fw_nftables_add_local_dnat_internal( sd_netlink *nfnl, bool add, int af, int protocol, uint16_t local_port, const union in_addr_union *remote, uint16_t remote_port, const union in_addr_union *previous_remote) { sd_netlink_message *messages[3] = {}; _unused_ _cleanup_(netlink_message_unref_manyp) sd_netlink_message **unref = messages; static bool ipv6_supported = true; uint32_t data[5], key[2], dlen; size_t msgcnt = 0; int r; assert(nfnl); assert(add || !previous_remote); assert(IN_SET(af, AF_INET, AF_INET6)); if (!ipv6_supported && af == AF_INET6) return -EOPNOTSUPP; if (!IN_SET(protocol, IPPROTO_TCP, IPPROTO_UDP)) return -EPROTONOSUPPORT; if (local_port <= 0) return -EINVAL; key[0] = protocol; key[1] = htobe16(local_port); if (!remote) return -EOPNOTSUPP; if (remote_port <= 0) return -EINVAL; if (af == AF_INET) { dlen = 8; data[1] = htobe16(remote_port); } else { assert(af == AF_INET6); dlen = sizeof(data); data[4] = htobe16(remote_port); } /* If a previous remote is set, remove its entry */ if (add && previous_remote && !in_addr_equal(af, previous_remote, remote)) { if (af == AF_INET) data[0] = previous_remote->in.s_addr; else memcpy(data, &previous_remote->in6, sizeof(previous_remote->in6)); r = nft_del_element(nfnl, &messages[msgcnt++], af, NFT_SYSTEMD_DNAT_MAP_NAME, key, sizeof(key), data, dlen); if (r < 0) return r; } if (af == AF_INET) data[0] = remote->in.s_addr; else memcpy(data, &remote->in6, sizeof(remote->in6)); if (add) r = nft_add_element(nfnl, &messages[msgcnt++], af, NFT_SYSTEMD_DNAT_MAP_NAME, key, sizeof(key), data, dlen); else r = nft_del_element(nfnl, &messages[msgcnt++], af, NFT_SYSTEMD_DNAT_MAP_NAME, key, sizeof(key), data, dlen); if (r < 0) return r; assert(msgcnt < ELEMENTSOF(messages)); r = sd_nfnl_call_batch(nfnl, messages, msgcnt, NFNL_DEFAULT_TIMEOUT_USECS, NULL); if (r == -EOVERFLOW && af == AF_INET6) { /* The current implementation of DNAT in systemd requires kernel's * fdb9c405e35bdc6e305b9b4e20ebc141ed14fc81 (v5.8), and the older kernel returns * -EOVERFLOW. Let's treat the error as -EOPNOTSUPP. */ log_debug_errno(r, "The current implementation of IPv6 DNAT in systemd requires kernel 5.8 or newer, ignoring: %m"); ipv6_supported = false; return -EOPNOTSUPP; } if (r < 0) return r; return 0; } int fw_nftables_add_local_dnat( FirewallContext *ctx, bool add, int af, int protocol, uint16_t local_port, const union in_addr_union *remote, uint16_t remote_port, const union in_addr_union *previous_remote) { int r; assert(ctx); assert(ctx->nfnl); assert(IN_SET(af, AF_INET, AF_INET6)); if (!socket_ipv6_is_supported() && af == AF_INET6) return -EOPNOTSUPP; r = fw_nftables_add_local_dnat_internal(ctx->nfnl, add, af, protocol, local_port, remote, remote_port, previous_remote); if (r != -ENOENT) return r; /* See comment in fw_nftables_add_masquerade(). */ r = fw_nftables_init_family(ctx->nfnl, af); if (r < 0) return r; /* table created anew; previous address already gone */ return fw_nftables_add_local_dnat_internal(ctx->nfnl, add, af, protocol, local_port, remote, remote_port, NULL); }