npf_alg.c revision 1.21 
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 1.21 2019/08/25 13:21:03 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
53struct npf_alg {
54	const char *	na_name;
55	unsigned	na_slot;
56};
57
58struct 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
70void
71npf_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
79void
80npf_alg_fini(npf_t *npf)
81{
82	npf_algset_t *aset = npf->algset;
83
84	kmem_free(aset, sizeof(npf_algset_t));
85}
86
87static npf_alg_t *
88npf_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
104npf_alg_t *
105npf_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 */
129npf_alg_t *
130npf_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	/* Assign the functions. */
160	afuncs = &aset->alg_funcs[i];
161	afuncs->match = funcs->match;
162	afuncs->translate = funcs->translate;
163	afuncs->inspect = funcs->inspect;
164
165	aset->alg_count = MAX(aset->alg_count, i + 1);
166	npf_config_exit(npf);
167
168	return alg;
169}
170
171/*
172 * npf_alg_unregister: unregister application-level gateway.
173 */
174int
175npf_alg_unregister(npf_t *npf, npf_alg_t *alg)
176{
177	npf_algset_t *aset = npf->algset;
178	unsigned i = alg->na_slot;
179	npfa_funcs_t *afuncs;
180
181	/* Deactivate the functions first. */
182	npf_config_enter(npf);
183	afuncs = &aset->alg_funcs[i];
184	afuncs->match = NULL;
185	afuncs->translate = NULL;
186	afuncs->inspect = NULL;
187	npf_ebr_full_sync(npf->ebr);
188
189	/* Finally, unregister the ALG. */
190	npf_ruleset_freealg(npf_config_natset(npf), alg);
191	alg->na_name = NULL;
192	npf_config_exit(npf);
193
194	return 0;
195}
196
197/*
198 * npf_alg_match: call the ALG matching inspectors.
199 *
200 *	The purpose of the "matching" inspector function in the ALG API
201 *	is to determine whether this connection matches the ALG criteria
202 *	i.e. is concerning the ALG.  If yes, ALG can associate itself with
203 *	the given NAT state structure and set/save an arbitrary parameter.
204 *	This is done using the using the npf_nat_setalg() function.
205 *
206 *	=> This is called when the packet matches the dynamic NAT policy
207 *	   and the NAT state entry is being created for it [NAT-ESTABLISH].
208 */
209bool
210npf_alg_match(npf_cache_t *npc, npf_nat_t *nt, int di)
211{
212	npf_t *npf = npc->npc_ctx;
213	npf_algset_t *aset = npf->algset;
214	bool match = false;
215	int s;
216
217	KASSERTMSG(npf_iscached(npc, NPC_IP46), "expecting protocol number");
218
219	s = npf_ebr_enter(npf->ebr);
220	for (unsigned i = 0; i < aset->alg_count; i++) {
221		const npfa_funcs_t *f = &aset->alg_funcs[i];
222
223		if (f->match && f->match(npc, nt, di)) {
224			match = true;
225			break;
226		}
227	}
228	npf_ebr_exit(npf->ebr, s);
229	return match;
230}
231
232/*
233 * npf_alg_exec: execute the ALG translation processors.
234 *
235 *	The ALG function would perform any additional packet translation
236 *	or manipulation here.  The translate function will be called by
237 *	once the ALG has been associated with the NAT state through the
238 *	npf_alg_match() inspector.
239 *
240 *	=> This is called when the packet is being translated according
241 *	   to the dynamic NAT logic [NAT-TRANSLATE].
242 */
243void
244npf_alg_exec(npf_cache_t *npc, npf_nat_t *nt, bool forw)
245{
246	npf_t *npf = npc->npc_ctx;
247	npf_algset_t *aset = npf->algset;
248	int s;
249
250	KASSERTMSG(npf_iscached(npc, NPC_IP46), "expecting protocol number");
251
252	s = npf_ebr_enter(npf->ebr);
253	for (unsigned i = 0; i < aset->alg_count; i++) {
254		const npfa_funcs_t *f = &aset->alg_funcs[i];
255
256		if (f->translate) {
257			f->translate(npc, nt, forw);
258		}
259	}
260	npf_ebr_exit(npf->ebr, s);
261}
262
263/*
264 * npf_alg_conn: query ALGs which may perform a custom state lookup.
265 *
266 *	The purpose of ALG connection inspection function is to provide
267 *	ALGs with a mechanism to override the regular connection state
268 *	lookup, if they need to.  For example, some ALGs may want to
269 *	extract and use a different 5-tuple to perform a lookup.
270 *
271 *	=> This is called at the beginning of the connection state lookup
272 *	   function [CONN-LOOKUP].
273 *
274 *	=> Must use the npf_conn_lookup() function to perform the custom
275 *	   connection state lookup and return the result.
276 *
277 *	=> Returning NULL will result in NPF performing a regular state
278 *	   lookup for the packet.
279 */
280npf_conn_t *
281npf_alg_conn(npf_cache_t *npc, int di)
282{
283	npf_t *npf = npc->npc_ctx;
284	npf_algset_t *aset = npf->algset;
285	npf_conn_t *con = NULL;
286	int s;
287
288	s = npf_ebr_enter(npf->ebr);
289	for (unsigned i = 0; i < aset->alg_count; i++) {
290		const npfa_funcs_t *f = &aset->alg_funcs[i];
291
292		if (!f->inspect)
293			continue;
294		if ((con = f->inspect(npc, di)) != NULL)
295			break;
296	}
297	npf_ebr_exit(npf->ebr, s);
298	return con;
299}
300
301/*
302 * npf_alg_export: serialise the configuration of ALGs.
303 */
304int
305npf_alg_export(npf_t *npf, nvlist_t *npf_dict)
306{
307	npf_algset_t *aset = npf->algset;
308
309	KASSERT(npf_config_locked_p(npf));
310
311	for (unsigned i = 0; i < aset->alg_count; i++) {
312		const npf_alg_t *alg = &aset->alg_list[i];
313		nvlist_t *algdict;
314
315		if (alg->na_name == NULL) {
316			continue;
317		}
318		algdict = nvlist_create(0);
319		nvlist_add_string(algdict, "name", alg->na_name);
320		nvlist_append_nvlist_array(npf_dict, "algs", algdict);
321		nvlist_destroy(algdict);
322	}
323	return 0;
324}
325