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authorLennart Poettering <lennart@poettering.net>2015-01-13 13:44:30 +0100
committerLennart Poettering <lennart@poettering.net>2015-01-13 13:55:15 +0100
commit76917807eb50ccde58901e8bec7ed3d408d1cc22 (patch)
treef4de29f757a3257dd2190a744ea373e87e81612d /src/shared
parent6cb7fa17b3d89741a5fd3ac807775a3022c7d891 (diff)
shared: add minimal firewall manipulation helpers for establishing NAT rules, using libiptc
Diffstat (limited to 'src/shared')
-rw-r--r--src/shared/fw-util.c344
-rw-r--r--src/shared/fw-util.h82
-rw-r--r--src/shared/in-addr-util.c20
-rw-r--r--src/shared/in-addr-util.h3
4 files changed, 443 insertions, 6 deletions
diff --git a/src/shared/fw-util.c b/src/shared/fw-util.c
new file mode 100644
index 0000000000..ceb1ae508c
--- /dev/null
+++ b/src/shared/fw-util.c
@@ -0,0 +1,344 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+ This file is part of systemd.
+
+ Copyright 2015 Lennart Poettering
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <sys/types.h>
+#include <arpa/inet.h>
+#include <net/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 "util.h"
+#include "fw-util.h"
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(struct xtc_handle*, iptc_free);
+
+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 && strlen(out_interface) >= IFNAMSIZ)
+ return -EINVAL;
+
+ if (in_interface && strlen(in_interface) >= IFNAMSIZ)
+ return -EINVAL;
+
+ entry->ip.proto = protocol;
+
+ if (in_interface) {
+ strcpy(entry->ip.iniface, in_interface);
+ memset(entry->ip.iniface_mask, 0xFF, strlen(in_interface)+1);
+ }
+ if (source) {
+ entry->ip.src = source->in;
+ in_addr_prefixlen_to_netmask(&entry->ip.smsk, source_prefixlen);
+ }
+
+ if (out_interface) {
+ strcpy(entry->ip.outiface, out_interface);
+ memset(entry->ip.outiface_mask, 0xFF, strlen(out_interface)+1);
+ }
+ if (destination) {
+ entry->ip.dst = destination->in;
+ in_addr_prefixlen_to_netmask(&entry->ip.dmsk, destination_prefixlen);
+ }
+
+ return 0;
+}
+
+int fw_add_masquerade(
+ bool add,
+ int af,
+ int protocol,
+ const union in_addr_union *source,
+ unsigned source_prefixlen,
+ const char *out_interface,
+ const union in_addr_union *destination,
+ unsigned destination_prefixlen) {
+
+ _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;
+
+ if (af != AF_INET)
+ return -ENOTSUP;
+
+ if (protocol != 0 && protocol != IPPROTO_TCP && protocol != IPPROTO_UDP)
+ return -ENOTSUP;
+
+ h = iptc_init("nat");
+ if (!h)
+ return -errno;
+
+ 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(sz);
+ memset(mask, 0xFF, sz);
+
+ if (add) {
+ if (iptc_check_entry("POSTROUTING", entry, (unsigned char*) mask, h))
+ return 0;
+ if (errno != ENOENT) /* if other error than not existing yet, fail */
+ return -errno;
+
+ if (!iptc_insert_entry("POSTROUTING", entry, 0, h))
+ return -errno;
+ } else {
+ if (!iptc_delete_entry("POSTROUTING", 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_add_local_dnat(
+ bool add,
+ int af,
+ int protocol,
+ const char *in_interface,
+ const union in_addr_union *source,
+ unsigned source_prefixlen,
+ const union in_addr_union *destination,
+ unsigned destination_prefixlen,
+ uint16_t local_port,
+ const union in_addr_union *remote,
+ uint16_t remote_port,
+ const union in_addr_union *previous_remote) {
+
+
+ _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;
+
+ assert(add || !previous_remote);
+
+ if (af != AF_INET)
+ return -ENOTSUP;
+
+ if (protocol != IPPROTO_TCP && protocol != IPPROTO_UDP)
+ return -ENOTSUP;
+
+ if (local_port <= 0)
+ return -EINVAL;
+
+ if (remote_port <= 0)
+ return -EINVAL;
+
+ h = iptc_init("nat");
+ if (!h)
+ return -errno;
+
+ 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 = htons(remote_port);
+ else
+ mr->range[0].min.udp.port = mr->range[0].max.udp.port = htons(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("PREROUTING", entry, (unsigned char*) mask, h)) {
+ if (errno != ENOENT)
+ return -EINVAL;
+
+ if (!iptc_insert_entry("PREROUTING", 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("PREROUTING", 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("OUTPUT", entry, (unsigned char*) mask, h)) {
+ if (errno != ENOENT)
+ return -errno;
+
+ if (!iptc_insert_entry("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("OUTPUT", entry, (unsigned char*) mask, h)) {
+ if (errno != ENOENT)
+ return -errno;
+ }
+ }
+ }
+ } else {
+ if (!iptc_delete_entry("PREROUTING", 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("OUTPUT", entry, (unsigned char*) mask, h)) {
+ if (errno != ENOENT)
+ return -errno;
+ }
+ }
+ }
+
+ if (!iptc_commit(h))
+ return -errno;
+
+ return 0;
+}
diff --git a/src/shared/fw-util.h b/src/shared/fw-util.h
new file mode 100644
index 0000000000..58b4c2024d
--- /dev/null
+++ b/src/shared/fw-util.h
@@ -0,0 +1,82 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+#pragma once
+
+/***
+ This file is part of systemd.
+
+ Copyright 2015 Lennart Poettering
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include "in-addr-util.h"
+
+#ifdef HAVE_LIBIPTC
+
+int fw_add_masquerade(
+ bool add,
+ int af,
+ int protocol,
+ const union in_addr_union *source,
+ unsigned source_prefixlen,
+ const char *out_interface,
+ const union in_addr_union *destination,
+ unsigned destination_prefixlen);
+
+int fw_add_local_dnat(
+ bool add,
+ int af,
+ int protocol,
+ const char *in_interface,
+ const union in_addr_union *source,
+ unsigned source_prefixlen,
+ const union in_addr_union *destination,
+ unsigned destination_prefixlen,
+ uint16_t local_port,
+ const union in_addr_union *remote,
+ uint16_t remote_port,
+ const union in_addr_union *previous_remote);
+
+#else
+
+static inline int fw_add_masquerade(
+ bool add,
+ int af,
+ int protocol,
+ const union in_addr_union *source,
+ unsigned source_prefixlen,
+ const char *out_interface,
+ const union in_addr_union *destination,
+ unsigned destination_prefixlen) {
+ return -ENOTSUP;
+}
+
+static inline int fw_add_local_dnat(
+ bool add,
+ int af,
+ int protocol,
+ const char *in_interface,
+ const union in_addr_union *source,
+ unsigned source_prefixlen,
+ const union in_addr_union *destination,
+ unsigned destination_prefixlen,
+ uint16_t local_port,
+ const union in_addr_union *remote,
+ uint16_t remote_port,
+ const union in_addr_union *previous_remote) {
+ return -ENOSTUP;
+}
+
+#endif
diff --git a/src/shared/in-addr-util.c b/src/shared/in-addr-util.c
index 9dc9ec82b4..b02e7516ca 100644
--- a/src/shared/in-addr-util.c
+++ b/src/shared/in-addr-util.c
@@ -243,12 +243,25 @@ int in_addr_from_string_auto(const char *s, int *family, union in_addr_union *re
return -EINVAL;
}
-unsigned in_addr_netmask_to_prefixlen(const struct in_addr *addr) {
+unsigned char in_addr_netmask_to_prefixlen(const struct in_addr *addr) {
assert(addr);
return 32 - u32ctz(be32toh(addr->s_addr));
}
+struct in_addr* in_addr_prefixlen_to_netmask(struct in_addr *addr, unsigned char prefixlen) {
+ assert(addr);
+ assert(prefixlen <= 32);
+
+ /* Shifting beyond 32 is not defined, handle this specially. */
+ if (prefixlen == 0)
+ addr->s_addr = 0;
+ else
+ addr->s_addr = htobe32((0xffffffff << (32 - prefixlen)) & 0xffffffff);
+
+ return addr;
+}
+
int in_addr_default_prefixlen(const struct in_addr *addr, unsigned char *prefixlen) {
uint8_t msb_octet = *(uint8_t*) addr;
@@ -284,9 +297,6 @@ int in_addr_default_subnet_mask(const struct in_addr *addr, struct in_addr *mask
if (r < 0)
return r;
- assert(prefixlen > 0 && prefixlen < 32);
-
- mask->s_addr = htobe32((0xffffffff << (32 - prefixlen)) & 0xffffffff);
-
+ in_addr_prefixlen_to_netmask(mask, prefixlen);
return 0;
}
diff --git a/src/shared/in-addr-util.h b/src/shared/in-addr-util.h
index 8da030ceb6..4cf4418b4b 100644
--- a/src/shared/in-addr-util.h
+++ b/src/shared/in-addr-util.h
@@ -39,7 +39,8 @@ int in_addr_prefix_next(int family, union in_addr_union *u, unsigned prefixlen);
int in_addr_to_string(int family, const union in_addr_union *u, char **ret);
int in_addr_from_string(int family, const char *s, union in_addr_union *ret);
int in_addr_from_string_auto(const char *s, int *family, union in_addr_union *ret);
-unsigned in_addr_netmask_to_prefixlen(const struct in_addr *addr);
+unsigned char in_addr_netmask_to_prefixlen(const struct in_addr *addr);
+struct in_addr* in_addr_prefixlen_to_netmask(struct in_addr *addr, unsigned char prefixlen);
int in_addr_default_prefixlen(const struct in_addr *addr, unsigned char *prefixlen);
int in_addr_default_subnet_mask(const struct in_addr *addr, struct in_addr *mask);