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7a6eb60b | 1 | /* SPDX-License-Identifier: LGPL-2.1-or-later */ |
31220972 FW |
2 | |
3 | /* Temporary work-around for broken glibc vs. linux kernel header definitions | |
4 | * This is already fixed upstream, remove this when distributions have updated. | |
5 | */ | |
6 | #define _NET_IF_H 1 | |
7 | ||
8 | #include <arpa/inet.h> | |
9 | #include <endian.h> | |
10 | #include <errno.h> | |
11 | #include <stddef.h> | |
12 | #include <string.h> | |
13 | #include <net/if.h> | |
14 | #ifndef IFNAMSIZ | |
15 | #define IFNAMSIZ 16 | |
16 | #endif | |
17 | #include <linux/if.h> | |
18 | #include <linux/netfilter_ipv4/ip_tables.h> | |
19 | #include <linux/netfilter/nf_nat.h> | |
20 | #include <linux/netfilter/xt_addrtype.h> | |
21 | #include <libiptc/libiptc.h> | |
22 | ||
23 | #include "alloc-util.h" | |
24 | #include "firewall-util.h" | |
25 | #include "firewall-util-private.h" | |
26 | #include "in-addr-util.h" | |
27 | #include "macro.h" | |
28 | #include "socket-util.h" | |
29 | ||
fd421c4a | 30 | DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(struct xtc_handle*, iptc_free, NULL); |
31220972 FW |
31 | |
32 | static int entry_fill_basics( | |
33 | struct ipt_entry *entry, | |
34 | int protocol, | |
35 | const char *in_interface, | |
36 | const union in_addr_union *source, | |
37 | unsigned source_prefixlen, | |
38 | const char *out_interface, | |
39 | const union in_addr_union *destination, | |
40 | unsigned destination_prefixlen) { | |
41 | ||
42 | assert(entry); | |
43 | ||
44 | if (out_interface && !ifname_valid(out_interface)) | |
45 | return -EINVAL; | |
46 | if (in_interface && !ifname_valid(in_interface)) | |
47 | return -EINVAL; | |
48 | ||
49 | entry->ip.proto = protocol; | |
50 | ||
51 | if (in_interface) { | |
52 | size_t l; | |
53 | ||
54 | l = strlen(in_interface); | |
55 | assert(l < sizeof entry->ip.iniface); | |
56 | assert(l < sizeof entry->ip.iniface_mask); | |
57 | ||
58 | strcpy(entry->ip.iniface, in_interface); | |
59 | memset(entry->ip.iniface_mask, 0xFF, l + 1); | |
60 | } | |
61 | if (source) { | |
62 | entry->ip.src = source->in; | |
63 | in4_addr_prefixlen_to_netmask(&entry->ip.smsk, source_prefixlen); | |
64 | } | |
65 | ||
66 | if (out_interface) { | |
67 | size_t l = strlen(out_interface); | |
68 | assert(l < sizeof entry->ip.outiface); | |
69 | assert(l < sizeof entry->ip.outiface_mask); | |
70 | ||
71 | strcpy(entry->ip.outiface, out_interface); | |
72 | memset(entry->ip.outiface_mask, 0xFF, l + 1); | |
73 | } | |
74 | if (destination) { | |
75 | entry->ip.dst = destination->in; | |
76 | in4_addr_prefixlen_to_netmask(&entry->ip.dmsk, destination_prefixlen); | |
77 | } | |
78 | ||
79 | return 0; | |
80 | } | |
81 | ||
82 | int fw_iptables_add_masquerade( | |
83 | bool add, | |
84 | int af, | |
85 | const union in_addr_union *source, | |
86 | unsigned source_prefixlen) { | |
87 | ||
88 | static const xt_chainlabel chain = "POSTROUTING"; | |
89 | _cleanup_(iptc_freep) struct xtc_handle *h = NULL; | |
90 | struct ipt_entry *entry, *mask; | |
91 | struct ipt_entry_target *t; | |
92 | size_t sz; | |
93 | struct nf_nat_ipv4_multi_range_compat *mr; | |
94 | int r, protocol = 0; | |
95 | const char *out_interface = NULL; | |
96 | const union in_addr_union *destination = NULL; | |
97 | unsigned destination_prefixlen = 0; | |
98 | ||
99 | if (af != AF_INET) | |
100 | return -EOPNOTSUPP; | |
101 | ||
102 | if (!source || source_prefixlen == 0) | |
103 | return -EINVAL; | |
104 | ||
afbcd905 AZ |
105 | r = fw_iptables_init_nat(&h); |
106 | if (r < 0) | |
107 | return r; | |
31220972 FW |
108 | |
109 | sz = XT_ALIGN(sizeof(struct ipt_entry)) + | |
110 | XT_ALIGN(sizeof(struct ipt_entry_target)) + | |
111 | XT_ALIGN(sizeof(struct nf_nat_ipv4_multi_range_compat)); | |
112 | ||
113 | /* Put together the entry we want to add or remove */ | |
114 | entry = alloca0(sz); | |
115 | entry->next_offset = sz; | |
116 | entry->target_offset = XT_ALIGN(sizeof(struct ipt_entry)); | |
117 | r = entry_fill_basics(entry, protocol, NULL, source, source_prefixlen, out_interface, destination, destination_prefixlen); | |
118 | if (r < 0) | |
119 | return r; | |
120 | ||
121 | /* Fill in target part */ | |
122 | t = ipt_get_target(entry); | |
123 | t->u.target_size = | |
124 | XT_ALIGN(sizeof(struct ipt_entry_target)) + | |
125 | XT_ALIGN(sizeof(struct nf_nat_ipv4_multi_range_compat)); | |
126 | strncpy(t->u.user.name, "MASQUERADE", sizeof(t->u.user.name)); | |
127 | mr = (struct nf_nat_ipv4_multi_range_compat*) t->data; | |
128 | mr->rangesize = 1; | |
129 | ||
130 | /* Create a search mask entry */ | |
131 | mask = alloca(sz); | |
132 | memset(mask, 0xFF, sz); | |
133 | ||
134 | if (add) { | |
135 | if (iptc_check_entry(chain, entry, (unsigned char*) mask, h)) | |
136 | return 0; | |
137 | if (errno != ENOENT) /* if other error than not existing yet, fail */ | |
138 | return -errno; | |
139 | ||
140 | if (!iptc_insert_entry(chain, entry, 0, h)) | |
141 | return -errno; | |
142 | } else { | |
143 | if (!iptc_delete_entry(chain, entry, (unsigned char*) mask, h)) { | |
144 | if (errno == ENOENT) /* if it's already gone, all is good! */ | |
145 | return 0; | |
146 | ||
147 | return -errno; | |
148 | } | |
149 | } | |
150 | ||
151 | if (!iptc_commit(h)) | |
152 | return -errno; | |
153 | ||
154 | return 0; | |
155 | } | |
156 | ||
157 | int fw_iptables_add_local_dnat( | |
158 | bool add, | |
159 | int af, | |
160 | int protocol, | |
161 | uint16_t local_port, | |
162 | const union in_addr_union *remote, | |
163 | uint16_t remote_port, | |
164 | const union in_addr_union *previous_remote) { | |
165 | ||
166 | static const xt_chainlabel chain_pre = "PREROUTING", chain_output = "OUTPUT"; | |
167 | _cleanup_(iptc_freep) struct xtc_handle *h = NULL; | |
168 | struct ipt_entry *entry, *mask; | |
169 | struct ipt_entry_target *t; | |
170 | struct ipt_entry_match *m; | |
171 | struct xt_addrtype_info_v1 *at; | |
172 | struct nf_nat_ipv4_multi_range_compat *mr; | |
173 | size_t sz, msz; | |
174 | int r; | |
175 | const char *in_interface = NULL; | |
176 | const union in_addr_union *source = NULL; | |
177 | unsigned source_prefixlen = 0; | |
178 | const union in_addr_union *destination = NULL; | |
179 | unsigned destination_prefixlen = 0; | |
180 | ||
181 | assert(add || !previous_remote); | |
182 | ||
183 | if (af != AF_INET) | |
184 | return -EOPNOTSUPP; | |
185 | ||
186 | if (!IN_SET(protocol, IPPROTO_TCP, IPPROTO_UDP)) | |
187 | return -EOPNOTSUPP; | |
188 | ||
189 | if (local_port <= 0) | |
190 | return -EINVAL; | |
191 | ||
192 | if (remote_port <= 0) | |
193 | return -EINVAL; | |
194 | ||
afbcd905 AZ |
195 | r = fw_iptables_init_nat(&h); |
196 | if (r < 0) | |
197 | return r; | |
31220972 FW |
198 | |
199 | sz = XT_ALIGN(sizeof(struct ipt_entry)) + | |
200 | XT_ALIGN(sizeof(struct ipt_entry_match)) + | |
201 | XT_ALIGN(sizeof(struct xt_addrtype_info_v1)) + | |
202 | XT_ALIGN(sizeof(struct ipt_entry_target)) + | |
203 | XT_ALIGN(sizeof(struct nf_nat_ipv4_multi_range_compat)); | |
204 | ||
205 | if (protocol == IPPROTO_TCP) | |
206 | msz = XT_ALIGN(sizeof(struct ipt_entry_match)) + | |
207 | XT_ALIGN(sizeof(struct xt_tcp)); | |
208 | else | |
209 | msz = XT_ALIGN(sizeof(struct ipt_entry_match)) + | |
210 | XT_ALIGN(sizeof(struct xt_udp)); | |
211 | ||
212 | sz += msz; | |
213 | ||
214 | /* Fill in basic part */ | |
215 | entry = alloca0(sz); | |
216 | entry->next_offset = sz; | |
217 | entry->target_offset = | |
218 | XT_ALIGN(sizeof(struct ipt_entry)) + | |
219 | XT_ALIGN(sizeof(struct ipt_entry_match)) + | |
220 | XT_ALIGN(sizeof(struct xt_addrtype_info_v1)) + | |
221 | msz; | |
222 | r = entry_fill_basics(entry, protocol, in_interface, source, source_prefixlen, NULL, destination, destination_prefixlen); | |
223 | if (r < 0) | |
224 | return r; | |
225 | ||
226 | /* Fill in first match */ | |
227 | m = (struct ipt_entry_match*) ((uint8_t*) entry + XT_ALIGN(sizeof(struct ipt_entry))); | |
228 | m->u.match_size = msz; | |
229 | if (protocol == IPPROTO_TCP) { | |
230 | struct xt_tcp *tcp; | |
231 | ||
232 | strncpy(m->u.user.name, "tcp", sizeof(m->u.user.name)); | |
233 | tcp = (struct xt_tcp*) m->data; | |
234 | tcp->dpts[0] = tcp->dpts[1] = local_port; | |
235 | tcp->spts[0] = 0; | |
236 | tcp->spts[1] = 0xFFFF; | |
237 | ||
238 | } else { | |
239 | struct xt_udp *udp; | |
240 | ||
241 | strncpy(m->u.user.name, "udp", sizeof(m->u.user.name)); | |
242 | udp = (struct xt_udp*) m->data; | |
243 | udp->dpts[0] = udp->dpts[1] = local_port; | |
244 | udp->spts[0] = 0; | |
245 | udp->spts[1] = 0xFFFF; | |
246 | } | |
247 | ||
248 | /* Fill in second match */ | |
249 | m = (struct ipt_entry_match*) ((uint8_t*) entry + XT_ALIGN(sizeof(struct ipt_entry)) + msz); | |
250 | m->u.match_size = | |
251 | XT_ALIGN(sizeof(struct ipt_entry_match)) + | |
252 | XT_ALIGN(sizeof(struct xt_addrtype_info_v1)); | |
253 | strncpy(m->u.user.name, "addrtype", sizeof(m->u.user.name)); | |
254 | m->u.user.revision = 1; | |
255 | at = (struct xt_addrtype_info_v1*) m->data; | |
256 | at->dest = XT_ADDRTYPE_LOCAL; | |
257 | ||
258 | /* Fill in target part */ | |
259 | t = ipt_get_target(entry); | |
260 | t->u.target_size = | |
261 | XT_ALIGN(sizeof(struct ipt_entry_target)) + | |
262 | XT_ALIGN(sizeof(struct nf_nat_ipv4_multi_range_compat)); | |
263 | strncpy(t->u.user.name, "DNAT", sizeof(t->u.user.name)); | |
264 | mr = (struct nf_nat_ipv4_multi_range_compat*) t->data; | |
265 | mr->rangesize = 1; | |
266 | mr->range[0].flags = NF_NAT_RANGE_PROTO_SPECIFIED|NF_NAT_RANGE_MAP_IPS; | |
267 | mr->range[0].min_ip = mr->range[0].max_ip = remote->in.s_addr; | |
268 | if (protocol == IPPROTO_TCP) | |
269 | mr->range[0].min.tcp.port = mr->range[0].max.tcp.port = htobe16(remote_port); | |
270 | else | |
271 | mr->range[0].min.udp.port = mr->range[0].max.udp.port = htobe16(remote_port); | |
272 | ||
273 | mask = alloca0(sz); | |
274 | memset(mask, 0xFF, sz); | |
275 | ||
276 | if (add) { | |
277 | /* Add the PREROUTING rule, if it is missing so far */ | |
278 | if (!iptc_check_entry(chain_pre, entry, (unsigned char*) mask, h)) { | |
279 | if (errno != ENOENT) | |
280 | return -EINVAL; | |
281 | ||
282 | if (!iptc_insert_entry(chain_pre, entry, 0, h)) | |
283 | return -errno; | |
284 | } | |
285 | ||
286 | /* If a previous remote is set, remove its entry */ | |
287 | if (previous_remote && previous_remote->in.s_addr != remote->in.s_addr) { | |
288 | mr->range[0].min_ip = mr->range[0].max_ip = previous_remote->in.s_addr; | |
289 | ||
290 | if (!iptc_delete_entry(chain_pre, entry, (unsigned char*) mask, h)) { | |
291 | if (errno != ENOENT) | |
292 | return -errno; | |
293 | } | |
294 | ||
295 | mr->range[0].min_ip = mr->range[0].max_ip = remote->in.s_addr; | |
296 | } | |
297 | ||
298 | /* Add the OUTPUT rule, if it is missing so far */ | |
299 | if (!in_interface) { | |
300 | ||
301 | /* Don't apply onto loopback addresses */ | |
302 | if (!destination) { | |
303 | entry->ip.dst.s_addr = htobe32(0x7F000000); | |
304 | entry->ip.dmsk.s_addr = htobe32(0xFF000000); | |
305 | entry->ip.invflags = IPT_INV_DSTIP; | |
306 | } | |
307 | ||
308 | if (!iptc_check_entry(chain_output, entry, (unsigned char*) mask, h)) { | |
309 | if (errno != ENOENT) | |
310 | return -errno; | |
311 | ||
312 | if (!iptc_insert_entry(chain_output, entry, 0, h)) | |
313 | return -errno; | |
314 | } | |
315 | ||
316 | /* If a previous remote is set, remove its entry */ | |
317 | if (previous_remote && previous_remote->in.s_addr != remote->in.s_addr) { | |
318 | mr->range[0].min_ip = mr->range[0].max_ip = previous_remote->in.s_addr; | |
319 | ||
320 | if (!iptc_delete_entry(chain_output, entry, (unsigned char*) mask, h)) { | |
321 | if (errno != ENOENT) | |
322 | return -errno; | |
323 | } | |
324 | } | |
325 | } | |
326 | } else { | |
327 | if (!iptc_delete_entry(chain_pre, entry, (unsigned char*) mask, h)) { | |
328 | if (errno != ENOENT) | |
329 | return -errno; | |
330 | } | |
331 | ||
332 | if (!in_interface) { | |
333 | if (!destination) { | |
334 | entry->ip.dst.s_addr = htobe32(0x7F000000); | |
335 | entry->ip.dmsk.s_addr = htobe32(0xFF000000); | |
336 | entry->ip.invflags = IPT_INV_DSTIP; | |
337 | } | |
338 | ||
339 | if (!iptc_delete_entry(chain_output, entry, (unsigned char*) mask, h)) { | |
340 | if (errno != ENOENT) | |
341 | return -errno; | |
342 | } | |
343 | } | |
344 | } | |
345 | ||
346 | if (!iptc_commit(h)) | |
347 | return -errno; | |
348 | ||
349 | return 0; | |
350 | } | |
afbcd905 AZ |
351 | |
352 | int fw_iptables_init_nat(struct xtc_handle **ret) { | |
353 | _cleanup_(iptc_freep) struct xtc_handle *h = NULL; | |
354 | ||
355 | h = iptc_init("nat"); | |
356 | if (!h) | |
357 | return log_debug_errno(errno, "Failed to init \"nat\" table: %s", iptc_strerror(errno)); | |
358 | ||
359 | if (ret) | |
360 | *ret = TAKE_PTR(h); | |
361 | ||
362 | return 0; | |
363 | } |