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-rw-r--r--src/shared/firewall-util-iptables.c363
1 files changed, 363 insertions, 0 deletions
diff --git a/src/shared/firewall-util-iptables.c b/src/shared/firewall-util-iptables.c
new file mode 100644
index 0000000..55bb427
--- /dev/null
+++ b/src/shared/firewall-util-iptables.c
@@ -0,0 +1,363 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+/* Temporary work-around for broken glibc vs. linux kernel header definitions
+ * This is already fixed upstream, remove this when distributions have updated.
+ */
+#define _NET_IF_H 1
+
+#include <arpa/inet.h>
+#include <endian.h>
+#include <errno.h>
+#include <stddef.h>
+#include <string.h>
+#include <net/if.h>
+#ifndef IFNAMSIZ
+#define IFNAMSIZ 16
+#endif
+#include <linux/if.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter/nf_nat.h>
+#include <linux/netfilter/xt_addrtype.h>
+#include <libiptc/libiptc.h>
+
+#include "alloc-util.h"
+#include "firewall-util.h"
+#include "firewall-util-private.h"
+#include "in-addr-util.h"
+#include "macro.h"
+#include "socket-util.h"
+
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(struct xtc_handle*, iptc_free, NULL);
+
+static int entry_fill_basics(
+ struct ipt_entry *entry,
+ int protocol,
+ const char *in_interface,
+ const union in_addr_union *source,
+ unsigned source_prefixlen,
+ const char *out_interface,
+ const union in_addr_union *destination,
+ unsigned destination_prefixlen) {
+
+ assert(entry);
+
+ if (out_interface && !ifname_valid(out_interface))
+ return -EINVAL;
+ if (in_interface && !ifname_valid(in_interface))
+ return -EINVAL;
+
+ entry->ip.proto = protocol;
+
+ if (in_interface) {
+ size_t l;
+
+ l = strlen(in_interface);
+ assert(l < sizeof entry->ip.iniface);
+ assert(l < sizeof entry->ip.iniface_mask);
+
+ strcpy(entry->ip.iniface, in_interface);
+ memset(entry->ip.iniface_mask, 0xFF, l + 1);
+ }
+ if (source) {
+ entry->ip.src = source->in;
+ in4_addr_prefixlen_to_netmask(&entry->ip.smsk, source_prefixlen);
+ }
+
+ if (out_interface) {
+ size_t l = strlen(out_interface);
+ assert(l < sizeof entry->ip.outiface);
+ assert(l < sizeof entry->ip.outiface_mask);
+
+ strcpy(entry->ip.outiface, out_interface);
+ memset(entry->ip.outiface_mask, 0xFF, l + 1);
+ }
+ if (destination) {
+ entry->ip.dst = destination->in;
+ in4_addr_prefixlen_to_netmask(&entry->ip.dmsk, destination_prefixlen);
+ }
+
+ return 0;
+}
+
+int fw_iptables_add_masquerade(
+ bool add,
+ int af,
+ const union in_addr_union *source,
+ unsigned source_prefixlen) {
+
+ static const xt_chainlabel chain = "POSTROUTING";
+ _cleanup_(iptc_freep) struct xtc_handle *h = NULL;
+ struct ipt_entry *entry, *mask;
+ struct ipt_entry_target *t;
+ size_t sz;
+ struct nf_nat_ipv4_multi_range_compat *mr;
+ int r, protocol = 0;
+ const char *out_interface = NULL;
+ const union in_addr_union *destination = NULL;
+ unsigned destination_prefixlen = 0;
+
+ if (af != AF_INET)
+ return -EOPNOTSUPP;
+
+ if (!source || source_prefixlen == 0)
+ return -EINVAL;
+
+ r = fw_iptables_init_nat(&h);
+ if (r < 0)
+ return r;
+
+ sz = XT_ALIGN(sizeof(struct ipt_entry)) +
+ XT_ALIGN(sizeof(struct ipt_entry_target)) +
+ XT_ALIGN(sizeof(struct nf_nat_ipv4_multi_range_compat));
+
+ /* Put together the entry we want to add or remove */
+ entry = alloca0(sz);
+ entry->next_offset = sz;
+ entry->target_offset = XT_ALIGN(sizeof(struct ipt_entry));
+ r = entry_fill_basics(entry, protocol, NULL, source, source_prefixlen, out_interface, destination, destination_prefixlen);
+ if (r < 0)
+ return r;
+
+ /* Fill in target part */
+ t = ipt_get_target(entry);
+ t->u.target_size =
+ XT_ALIGN(sizeof(struct ipt_entry_target)) +
+ XT_ALIGN(sizeof(struct nf_nat_ipv4_multi_range_compat));
+ strncpy(t->u.user.name, "MASQUERADE", sizeof(t->u.user.name));
+ mr = (struct nf_nat_ipv4_multi_range_compat*) t->data;
+ mr->rangesize = 1;
+
+ /* Create a search mask entry */
+ mask = alloca_safe(sz);
+ memset(mask, 0xFF, sz);
+
+ if (add) {
+ if (iptc_check_entry(chain, entry, (unsigned char*) mask, h))
+ return 0;
+ if (errno != ENOENT) /* if other error than not existing yet, fail */
+ return -errno;
+
+ if (!iptc_insert_entry(chain, entry, 0, h))
+ return -errno;
+ } else {
+ if (!iptc_delete_entry(chain, entry, (unsigned char*) mask, h)) {
+ if (errno == ENOENT) /* if it's already gone, all is good! */
+ return 0;
+
+ return -errno;
+ }
+ }
+
+ if (!iptc_commit(h))
+ return -errno;
+
+ return 0;
+}
+
+int fw_iptables_add_local_dnat(
+ 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) {
+
+ static const xt_chainlabel chain_pre = "PREROUTING", chain_output = "OUTPUT";
+ _cleanup_(iptc_freep) struct xtc_handle *h = NULL;
+ struct ipt_entry *entry, *mask;
+ struct ipt_entry_target *t;
+ struct ipt_entry_match *m;
+ struct xt_addrtype_info_v1 *at;
+ struct nf_nat_ipv4_multi_range_compat *mr;
+ size_t sz, msz;
+ int r;
+ const char *in_interface = NULL;
+ const union in_addr_union *source = NULL;
+ unsigned source_prefixlen = 0;
+ const union in_addr_union *destination = NULL;
+ unsigned destination_prefixlen = 0;
+
+ assert(add || !previous_remote);
+
+ if (af != AF_INET)
+ return -EOPNOTSUPP;
+
+ if (!IN_SET(protocol, IPPROTO_TCP, IPPROTO_UDP))
+ return -EOPNOTSUPP;
+
+ if (local_port <= 0)
+ return -EINVAL;
+
+ if (remote_port <= 0)
+ return -EINVAL;
+
+ r = fw_iptables_init_nat(&h);
+ if (r < 0)
+ return r;
+
+ sz = XT_ALIGN(sizeof(struct ipt_entry)) +
+ XT_ALIGN(sizeof(struct ipt_entry_match)) +
+ XT_ALIGN(sizeof(struct xt_addrtype_info_v1)) +
+ XT_ALIGN(sizeof(struct ipt_entry_target)) +
+ XT_ALIGN(sizeof(struct nf_nat_ipv4_multi_range_compat));
+
+ if (protocol == IPPROTO_TCP)
+ msz = XT_ALIGN(sizeof(struct ipt_entry_match)) +
+ XT_ALIGN(sizeof(struct xt_tcp));
+ else
+ msz = XT_ALIGN(sizeof(struct ipt_entry_match)) +
+ XT_ALIGN(sizeof(struct xt_udp));
+
+ sz += msz;
+
+ /* Fill in basic part */
+ entry = alloca0(sz);
+ entry->next_offset = sz;
+ entry->target_offset =
+ XT_ALIGN(sizeof(struct ipt_entry)) +
+ XT_ALIGN(sizeof(struct ipt_entry_match)) +
+ XT_ALIGN(sizeof(struct xt_addrtype_info_v1)) +
+ msz;
+ r = entry_fill_basics(entry, protocol, in_interface, source, source_prefixlen, NULL, destination, destination_prefixlen);
+ if (r < 0)
+ return r;
+
+ /* Fill in first match */
+ m = (struct ipt_entry_match*) ((uint8_t*) entry + XT_ALIGN(sizeof(struct ipt_entry)));
+ m->u.match_size = msz;
+ if (protocol == IPPROTO_TCP) {
+ struct xt_tcp *tcp;
+
+ strncpy(m->u.user.name, "tcp", sizeof(m->u.user.name));
+ tcp = (struct xt_tcp*) m->data;
+ tcp->dpts[0] = tcp->dpts[1] = local_port;
+ tcp->spts[0] = 0;
+ tcp->spts[1] = 0xFFFF;
+
+ } else {
+ struct xt_udp *udp;
+
+ strncpy(m->u.user.name, "udp", sizeof(m->u.user.name));
+ udp = (struct xt_udp*) m->data;
+ udp->dpts[0] = udp->dpts[1] = local_port;
+ udp->spts[0] = 0;
+ udp->spts[1] = 0xFFFF;
+ }
+
+ /* Fill in second match */
+ m = (struct ipt_entry_match*) ((uint8_t*) entry + XT_ALIGN(sizeof(struct ipt_entry)) + msz);
+ m->u.match_size =
+ XT_ALIGN(sizeof(struct ipt_entry_match)) +
+ XT_ALIGN(sizeof(struct xt_addrtype_info_v1));
+ strncpy(m->u.user.name, "addrtype", sizeof(m->u.user.name));
+ m->u.user.revision = 1;
+ at = (struct xt_addrtype_info_v1*) m->data;
+ at->dest = XT_ADDRTYPE_LOCAL;
+
+ /* Fill in target part */
+ t = ipt_get_target(entry);
+ t->u.target_size =
+ XT_ALIGN(sizeof(struct ipt_entry_target)) +
+ XT_ALIGN(sizeof(struct nf_nat_ipv4_multi_range_compat));
+ strncpy(t->u.user.name, "DNAT", sizeof(t->u.user.name));
+ mr = (struct nf_nat_ipv4_multi_range_compat*) t->data;
+ mr->rangesize = 1;
+ mr->range[0].flags = NF_NAT_RANGE_PROTO_SPECIFIED|NF_NAT_RANGE_MAP_IPS;
+ mr->range[0].min_ip = mr->range[0].max_ip = remote->in.s_addr;
+ if (protocol == IPPROTO_TCP)
+ mr->range[0].min.tcp.port = mr->range[0].max.tcp.port = htobe16(remote_port);
+ else
+ mr->range[0].min.udp.port = mr->range[0].max.udp.port = htobe16(remote_port);
+
+ mask = alloca0(sz);
+ memset(mask, 0xFF, sz);
+
+ if (add) {
+ /* Add the PREROUTING rule, if it is missing so far */
+ if (!iptc_check_entry(chain_pre, entry, (unsigned char*) mask, h)) {
+ if (errno != ENOENT)
+ return -EINVAL;
+
+ if (!iptc_insert_entry(chain_pre, entry, 0, h))
+ return -errno;
+ }
+
+ /* If a previous remote is set, remove its entry */
+ if (previous_remote && previous_remote->in.s_addr != remote->in.s_addr) {
+ mr->range[0].min_ip = mr->range[0].max_ip = previous_remote->in.s_addr;
+
+ if (!iptc_delete_entry(chain_pre, entry, (unsigned char*) mask, h)) {
+ if (errno != ENOENT)
+ return -errno;
+ }
+
+ mr->range[0].min_ip = mr->range[0].max_ip = remote->in.s_addr;
+ }
+
+ /* Add the OUTPUT rule, if it is missing so far */
+ if (!in_interface) {
+
+ /* Don't apply onto loopback addresses */
+ if (!destination) {
+ entry->ip.dst.s_addr = htobe32(0x7F000000);
+ entry->ip.dmsk.s_addr = htobe32(0xFF000000);
+ entry->ip.invflags = IPT_INV_DSTIP;
+ }
+
+ if (!iptc_check_entry(chain_output, entry, (unsigned char*) mask, h)) {
+ if (errno != ENOENT)
+ return -errno;
+
+ if (!iptc_insert_entry(chain_output, entry, 0, h))
+ return -errno;
+ }
+
+ /* If a previous remote is set, remove its entry */
+ if (previous_remote && previous_remote->in.s_addr != remote->in.s_addr) {
+ mr->range[0].min_ip = mr->range[0].max_ip = previous_remote->in.s_addr;
+
+ if (!iptc_delete_entry(chain_output, entry, (unsigned char*) mask, h)) {
+ if (errno != ENOENT)
+ return -errno;
+ }
+ }
+ }
+ } else {
+ if (!iptc_delete_entry(chain_pre, entry, (unsigned char*) mask, h)) {
+ if (errno != ENOENT)
+ return -errno;
+ }
+
+ if (!in_interface) {
+ if (!destination) {
+ entry->ip.dst.s_addr = htobe32(0x7F000000);
+ entry->ip.dmsk.s_addr = htobe32(0xFF000000);
+ entry->ip.invflags = IPT_INV_DSTIP;
+ }
+
+ if (!iptc_delete_entry(chain_output, entry, (unsigned char*) mask, h)) {
+ if (errno != ENOENT)
+ return -errno;
+ }
+ }
+ }
+
+ if (!iptc_commit(h))
+ return -errno;
+
+ return 0;
+}
+
+int fw_iptables_init_nat(struct xtc_handle **ret) {
+ _cleanup_(iptc_freep) struct xtc_handle *h = NULL;
+
+ h = iptc_init("nat");
+ if (!h)
+ return log_debug_errno(errno, "Failed to init \"nat\" table: %s", iptc_strerror(errno));
+
+ if (ret)
+ *ret = TAKE_PTR(h);
+
+ return 0;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-19 16:00:43 +0000