1 /*-
2 * Copyright (c) 2010-2019 The NetBSD Foundation, Inc.
3 * All rights reserved.
4 *
5 * This material is based upon work partially supported by The
6 * NetBSD Foundation under a contract with Mindaugas Rasiukevicius.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
18 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
19 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
20 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
21 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
22 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
23 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
24 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
25 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
26 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
27 * POSSIBILITY OF SUCH DAMAGE.
28 */
29
30 /*
31 * NPF interface for the Application Level Gateways (ALGs).
32 */
33
34 #ifdef _KERNEL
35 #include <sys/cdefs.h>
36 __KERNEL_RCSID(0, "$NetBSD: npf_alg.c,v 1.22 2020/05/30 14:16:56 rmind Exp $");
37
38 #include <sys/param.h>
39 #include <sys/types.h>
40
41 #include <sys/kmem.h>
42 #include <sys/module.h>
43 #endif
44
45 #include "npf_impl.h"
46
47 /*
48 * NAT ALG description structure. For more compact use of cache,
49 * the functions are separated in their own arrays. The number of
50 * ALGs is expected to be very small.
51 */
52
53 struct npf_alg {
54 const char * na_name;
55 unsigned na_slot;
56 };
57
58 struct npf_algset {
59 /* List of ALGs and the count. */
60 npf_alg_t alg_list[NPF_MAX_ALGS];
61 unsigned alg_count;
62
63 /* Matching, inspection and translation functions. */
64 npfa_funcs_t alg_funcs[NPF_MAX_ALGS];
65 };
66
67 #define NPF_ALG_PREF "npf_alg_"
68 #define NPF_ALG_PREFLEN (sizeof(NPF_ALG_PREF) - 1)
69
70 void
npf_alg_init(npf_t * npf)71 npf_alg_init(npf_t *npf)
72 {
73 npf_algset_t *aset;
74
75 aset = kmem_zalloc(sizeof(npf_algset_t), KM_SLEEP);
76 npf->algset = aset;
77 }
78
79 void
npf_alg_fini(npf_t * npf)80 npf_alg_fini(npf_t *npf)
81 {
82 npf_algset_t *aset = npf->algset;
83
84 kmem_free(aset, sizeof(npf_algset_t));
85 }
86
87 static npf_alg_t *
npf_alg_lookup(npf_t * npf,const char * name)88 npf_alg_lookup(npf_t *npf, const char *name)
89 {
90 npf_algset_t *aset = npf->algset;
91
92 KASSERT(npf_config_locked_p(npf));
93
94 for (unsigned i = 0; i < aset->alg_count; i++) {
95 npf_alg_t *alg = &aset->alg_list[i];
96 const char *aname = alg->na_name;
97
98 if (aname && strcmp(aname, name) == 0)
99 return alg;
100 }
101 return NULL;
102 }
103
104 npf_alg_t *
npf_alg_construct(npf_t * npf,const char * name)105 npf_alg_construct(npf_t *npf, const char *name)
106 {
107 npf_alg_t *alg;
108
109 npf_config_enter(npf);
110 if ((alg = npf_alg_lookup(npf, name)) == NULL) {
111 char modname[NPF_ALG_PREFLEN + 64];
112
113 snprintf(modname, sizeof(modname), "%s%s", NPF_ALG_PREF, name);
114 npf_config_exit(npf);
115
116 if (module_autoload(modname, MODULE_CLASS_MISC) != 0) {
117 return NULL;
118 }
119 npf_config_enter(npf);
120 alg = npf_alg_lookup(npf, name);
121 }
122 npf_config_exit(npf);
123 return alg;
124 }
125
126 /*
127 * npf_alg_register: register application-level gateway.
128 */
129 npf_alg_t *
npf_alg_register(npf_t * npf,const char * name,const npfa_funcs_t * funcs)130 npf_alg_register(npf_t *npf, const char *name, const npfa_funcs_t *funcs)
131 {
132 npf_algset_t *aset = npf->algset;
133 npfa_funcs_t *afuncs;
134 npf_alg_t *alg;
135 unsigned i;
136
137 npf_config_enter(npf);
138 if (npf_alg_lookup(npf, name) != NULL) {
139 npf_config_exit(npf);
140 return NULL;
141 }
142
143 /* Find a spare slot. */
144 for (i = 0; i < NPF_MAX_ALGS; i++) {
145 alg = &aset->alg_list[i];
146 if (alg->na_name == NULL) {
147 break;
148 }
149 }
150 if (i == NPF_MAX_ALGS) {
151 npf_config_exit(npf);
152 return NULL;
153 }
154
155 /* Register the ALG. */
156 alg->na_name = name;
157 alg->na_slot = i;
158
159 /*
160 * Assign the functions. Make sure the 'destroy' gets visible first.
161 */
162 afuncs = &aset->alg_funcs[i];
163 atomic_store_relaxed(&afuncs->destroy, funcs->destroy);
164 membar_producer();
165 atomic_store_relaxed(&afuncs->translate, funcs->translate);
166 atomic_store_relaxed(&afuncs->inspect, funcs->inspect);
167 atomic_store_relaxed(&afuncs->match, funcs->match);
168 membar_producer();
169
170 atomic_store_relaxed(&aset->alg_count, MAX(aset->alg_count, i + 1));
171 npf_config_exit(npf);
172
173 return alg;
174 }
175
176 /*
177 * npf_alg_unregister: unregister application-level gateway.
178 */
179 int
npf_alg_unregister(npf_t * npf,npf_alg_t * alg)180 npf_alg_unregister(npf_t *npf, npf_alg_t *alg)
181 {
182 npf_algset_t *aset = npf->algset;
183 unsigned i = alg->na_slot;
184 npfa_funcs_t *afuncs;
185
186 /* Deactivate the functions first. */
187 npf_config_enter(npf);
188 afuncs = &aset->alg_funcs[i];
189 atomic_store_relaxed(&afuncs->match, NULL);
190 atomic_store_relaxed(&afuncs->translate, NULL);
191 atomic_store_relaxed(&afuncs->inspect, NULL);
192 npf_config_sync(npf);
193
194 /*
195 * Finally, unregister the ALG. We leave the 'destroy' callback
196 * as the following will invoke it for the relevant connections.
197 */
198 npf_ruleset_freealg(npf_config_natset(npf), alg);
199 atomic_store_relaxed(&afuncs->destroy, NULL);
200 alg->na_name = NULL;
201 npf_config_exit(npf);
202
203 return 0;
204 }
205
206 /*
207 * npf_alg_match: call the ALG matching inspectors.
208 *
209 * The purpose of the "matching" inspector function in the ALG API
210 * is to determine whether this connection matches the ALG criteria
211 * i.e. is concerning the ALG. If yes, ALG can associate itself with
212 * the given NAT state structure and set/save an arbitrary parameter.
213 * This is done using the using the npf_nat_setalg() function.
214 *
215 * => This is called when the packet matches the dynamic NAT policy
216 * and the NAT state entry is being created for it [NAT-ESTABLISH].
217 */
218 bool
npf_alg_match(npf_cache_t * npc,npf_nat_t * nt,int di)219 npf_alg_match(npf_cache_t *npc, npf_nat_t *nt, int di)
220 {
221 npf_t *npf = npc->npc_ctx;
222 npf_algset_t *aset = npf->algset;
223 bool match = false;
224 unsigned count;
225 int s;
226
227 KASSERTMSG(npf_iscached(npc, NPC_IP46), "expecting protocol number");
228
229 s = npf_config_read_enter(npf);
230 count = atomic_load_relaxed(&aset->alg_count);
231 for (unsigned i = 0; i < count; i++) {
232 const npfa_funcs_t *f = &aset->alg_funcs[i];
233 bool (*match_func)(npf_cache_t *, npf_nat_t *, int);
234
235 match_func = atomic_load_relaxed(&f->match);
236 if (match_func && match_func(npc, nt, di)) {
237 match = true;
238 break;
239 }
240 }
241 npf_config_read_exit(npf, s);
242 return match;
243 }
244
245 /*
246 * npf_alg_exec: execute the ALG translation processors.
247 *
248 * The ALG function would perform any additional packet translation
249 * or manipulation here.
250 *
251 * => This is called when the packet is being translated according
252 * to the dynamic NAT logic [NAT-TRANSLATE].
253 */
254 void
npf_alg_exec(npf_cache_t * npc,npf_nat_t * nt,const npf_flow_t flow)255 npf_alg_exec(npf_cache_t *npc, npf_nat_t *nt, const npf_flow_t flow)
256 {
257 npf_t *npf = npc->npc_ctx;
258 npf_algset_t *aset = npf->algset;
259 unsigned count;
260 int s;
261
262 s = npf_config_read_enter(npf);
263 count = atomic_load_relaxed(&aset->alg_count);
264 for (unsigned i = 0; i < count; i++) {
265 const npfa_funcs_t *f = &aset->alg_funcs[i];
266 bool (*translate_func)(npf_cache_t *, npf_nat_t *, npf_flow_t);
267
268 translate_func = atomic_load_relaxed(&f->translate);
269 if (translate_func) {
270 translate_func(npc, nt, flow);
271 }
272 }
273 npf_config_read_exit(npf, s);
274 }
275
276 /*
277 * npf_alg_conn: query ALGs which may perform a custom state lookup.
278 *
279 * The purpose of ALG connection inspection function is to provide
280 * ALGs with a mechanism to override the regular connection state
281 * lookup, if they need to. For example, some ALGs may want to
282 * extract and use a different n-tuple to perform a lookup.
283 *
284 * => This is called at the beginning of the connection state lookup
285 * function [CONN-LOOKUP].
286 *
287 * => Must use the npf_conn_lookup() function to perform the custom
288 * connection state lookup and return the result.
289 *
290 * => Returning NULL will result in NPF performing a regular state
291 * lookup for the packet.
292 */
293 npf_conn_t *
npf_alg_conn(npf_cache_t * npc,int di)294 npf_alg_conn(npf_cache_t *npc, int di)
295 {
296 npf_t *npf = npc->npc_ctx;
297 npf_algset_t *aset = npf->algset;
298 npf_conn_t *con = NULL;
299 unsigned count;
300 int s;
301
302 s = npf_config_read_enter(npf);
303 count = atomic_load_relaxed(&aset->alg_count);
304 for (unsigned i = 0; i < count; i++) {
305 const npfa_funcs_t *f = &aset->alg_funcs[i];
306 npf_conn_t *(*inspect_func)(npf_cache_t *, int);
307
308 inspect_func = atomic_load_relaxed(&f->inspect);
309 if (inspect_func && (con = inspect_func(npc, di)) != NULL) {
310 break;
311 }
312 }
313 npf_config_read_exit(npf, s);
314 return con;
315 }
316
317 /*
318 * npf_alg_destroy: free the ALG structure associated with the NAT entry.
319 */
320 void
npf_alg_destroy(npf_t * npf,npf_alg_t * alg,npf_nat_t * nat,npf_conn_t * con)321 npf_alg_destroy(npf_t *npf, npf_alg_t *alg, npf_nat_t *nat, npf_conn_t *con)
322 {
323 npf_algset_t *aset = npf->algset;
324 const npfa_funcs_t *f = &aset->alg_funcs[alg->na_slot];
325 void (*destroy_func)(npf_t *, npf_nat_t *, npf_conn_t *);
326
327 if ((destroy_func = atomic_load_relaxed(&f->destroy)) != NULL) {
328 destroy_func(npf, nat, con);
329 }
330 }
331
332 /*
333 * npf_alg_export: serialise the configuration of ALGs.
334 */
335 int
npf_alg_export(npf_t * npf,nvlist_t * nvl)336 npf_alg_export(npf_t *npf, nvlist_t *nvl)
337 {
338 npf_algset_t *aset = npf->algset;
339
340 KASSERT(npf_config_locked_p(npf));
341
342 for (unsigned i = 0; i < aset->alg_count; i++) {
343 const npf_alg_t *alg = &aset->alg_list[i];
344 nvlist_t *algdict;
345
346 if (alg->na_name == NULL) {
347 continue;
348 }
349 algdict = nvlist_create(0);
350 nvlist_add_string(algdict, "name", alg->na_name);
351 nvlist_append_nvlist_array(nvl, "algs", algdict);
352 nvlist_destroy(algdict);
353 }
354 return 0;
355 }
356