npf_alg.c revision 1.20 
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 1.20 2019/07/23 00:52:01 rmind Exp $");
37
38#include <sys/param.h>
39#include <sys/types.h>
40
41#include <sys/kmem.h>
42#include <sys/pserialize.h>
43#include <sys/module.h>
44#endif
45
46#include "npf_impl.h"
47
48/*
49 * NAT ALG description structure.  For more compact use of cache,
50 * the functions are separated in their own arrays.  The number of
51 * ALGs is expected to be very small.
52 */
53
54struct npf_alg {
55	const char *	na_name;
56	unsigned	na_slot;
57};
58
59struct npf_algset {
60	/* List of ALGs and the count. */
61	npf_alg_t	alg_list[NPF_MAX_ALGS];
62	unsigned	alg_count;
63
64	/* Matching, inspection and translation functions. */
65	npfa_funcs_t	alg_funcs[NPF_MAX_ALGS];
66};
67
68#define	NPF_ALG_PREF	"npf_alg_"
69#define	NPF_ALG_PREFLEN	(sizeof(NPF_ALG_PREF) - 1)
70
71void
72npf_alg_init(npf_t *npf)
73{
74	npf_algset_t *aset;
75
76	aset = kmem_zalloc(sizeof(npf_algset_t), KM_SLEEP);
77	npf->algset = aset;
78}
79
80void
81npf_alg_fini(npf_t *npf)
82{
83	npf_algset_t *aset = npf->algset;
84
85	kmem_free(aset, sizeof(npf_algset_t));
86}
87
88static npf_alg_t *
89npf_alg_lookup(npf_t *npf, const char *name)
90{
91	npf_algset_t *aset = npf->algset;
92
93	KASSERT(npf_config_locked_p(npf));
94
95	for (unsigned i = 0; i < aset->alg_count; i++) {
96		npf_alg_t *alg = &aset->alg_list[i];
97		const char *aname = alg->na_name;
98
99		if (aname && strcmp(aname, name) == 0)
100			return alg;
101	}
102	return NULL;
103}
104
105npf_alg_t *
106npf_alg_construct(npf_t *npf, const char *name)
107{
108	npf_alg_t *alg;
109
110	npf_config_enter(npf);
111	if ((alg = npf_alg_lookup(npf, name)) == NULL) {
112		char modname[NPF_ALG_PREFLEN + 64];
113
114		snprintf(modname, sizeof(modname), "%s%s", NPF_ALG_PREF, name);
115		npf_config_exit(npf);
116
117		if (module_autoload(modname, MODULE_CLASS_MISC) != 0) {
118			return NULL;
119		}
120		npf_config_enter(npf);
121		alg = npf_alg_lookup(npf, name);
122	}
123	npf_config_exit(npf);
124	return alg;
125}
126
127/*
128 * npf_alg_register: register application-level gateway.
129 */
130npf_alg_t *
131npf_alg_register(npf_t *npf, const char *name, const npfa_funcs_t *funcs)
132{
133	npf_algset_t *aset = npf->algset;
134	npfa_funcs_t *afuncs;
135	npf_alg_t *alg;
136	unsigned i;
137
138	npf_config_enter(npf);
139	if (npf_alg_lookup(npf, name) != NULL) {
140		npf_config_exit(npf);
141		return NULL;
142	}
143
144	/* Find a spare slot. */
145	for (i = 0; i < NPF_MAX_ALGS; i++) {
146		alg = &aset->alg_list[i];
147		if (alg->na_name == NULL) {
148			break;
149		}
150	}
151	if (i == NPF_MAX_ALGS) {
152		npf_config_exit(npf);
153		return NULL;
154	}
155
156	/* Register the ALG. */
157	alg->na_name = name;
158	alg->na_slot = i;
159
160	/* Assign the functions. */
161	afuncs = &aset->alg_funcs[i];
162	afuncs->match = funcs->match;
163	afuncs->translate = funcs->translate;
164	afuncs->inspect = funcs->inspect;
165
166	aset->alg_count = MAX(aset->alg_count, i + 1);
167	npf_config_exit(npf);
168
169	return alg;
170}
171
172/*
173 * npf_alg_unregister: unregister application-level gateway.
174 */
175int
176npf_alg_unregister(npf_t *npf, npf_alg_t *alg)
177{
178	npf_algset_t *aset = npf->algset;
179	unsigned i = alg->na_slot;
180	npfa_funcs_t *afuncs;
181
182	/* Deactivate the functions first. */
183	npf_config_enter(npf);
184	afuncs = &aset->alg_funcs[i];
185	afuncs->match = NULL;
186	afuncs->translate = NULL;
187	afuncs->inspect = NULL;
188	pserialize_perform(npf->qsbr);
189
190	/* Finally, unregister the ALG. */
191	npf_ruleset_freealg(npf_config_natset(npf), alg);
192	alg->na_name = NULL;
193	npf_config_exit(npf);
194
195	return 0;
196}
197
198/*
199 * npf_alg_match: call the ALG matching inspectors.
200 *
201 *	The purpose of the "matching" inspector function in the ALG API
202 *	is to determine whether this connection matches the ALG criteria
203 *	i.e. is concerning the ALG.  If yes, ALG can associate itself with
204 *	the given NAT state structure and set/save an arbitrary parameter.
205 *	This is done using the using the npf_nat_setalg() function.
206 *
207 *	=> This is called when the packet matches the dynamic NAT policy
208 *	   and the NAT state entry is being created for it [NAT-ESTABLISH].
209 */
210bool
211npf_alg_match(npf_cache_t *npc, npf_nat_t *nt, int di)
212{
213	npf_algset_t *aset = npc->npc_ctx->algset;
214	bool match = false;
215	int s;
216
217	KASSERTMSG(npf_iscached(npc, NPC_IP46), "expecting protocol number");
218
219	s = pserialize_read_enter();
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	pserialize_read_exit(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_algset_t *aset = npc->npc_ctx->algset;
247	int s;
248
249	KASSERTMSG(npf_iscached(npc, NPC_IP46), "expecting protocol number");
250
251	s = pserialize_read_enter();
252	for (unsigned i = 0; i < aset->alg_count; i++) {
253		const npfa_funcs_t *f = &aset->alg_funcs[i];
254
255		if (f->translate) {
256			f->translate(npc, nt, forw);
257		}
258	}
259	pserialize_read_exit(s);
260}
261
262/*
263 * npf_alg_conn: query ALGs giving which may perform a custom state lookup.
264 *
265 *	The purpose of ALG connection inspection function is to provide
266 *	ALGs with a mechanism to override the regular connection state
267 *	lookup, if they need to.  For example, some ALGs may want to
268 *	extract and use a different 5-tuple to perform a lookup.
269 *
270 *	=> This is called at the beginning of the connection state lookup
271 *	   function [CONN-LOOKUP].
272 *
273 *	=> Must use the npf_conn_lookup() function to perform the custom
274 *	   connection state lookup and return the result.
275 *
276 *	=> Returning NULL will result in NPF performing a regular state
277 *	   lookup for the packet.
278 */
279npf_conn_t *
280npf_alg_conn(npf_cache_t *npc, int di)
281{
282	npf_algset_t *aset = npc->npc_ctx->algset;
283	npf_conn_t *con = NULL;
284	int s;
285
286	s = pserialize_read_enter();
287	for (unsigned i = 0; i < aset->alg_count; i++) {
288		const npfa_funcs_t *f = &aset->alg_funcs[i];
289
290		if (!f->inspect)
291			continue;
292		if ((con = f->inspect(npc, di)) != NULL)
293			break;
294	}
295	pserialize_read_exit(s);
296	return con;
297}
298
299/*
300 * npf_alg_export: serialise the configuration of ALGs.
301 */
302int
303npf_alg_export(npf_t *npf, nvlist_t *npf_dict)
304{
305	npf_algset_t *aset = npf->algset;
306
307	KASSERT(npf_config_locked_p(npf));
308
309	for (unsigned i = 0; i < aset->alg_count; i++) {
310		const npf_alg_t *alg = &aset->alg_list[i];
311		nvlist_t *algdict;
312
313		if (alg->na_name == NULL) {
314			continue;
315		}
316		algdict = nvlist_create(0);
317		nvlist_add_string(algdict, "name", alg->na_name);
318		nvlist_append_nvlist_array(npf_dict, "algs", algdict);
319		nvlist_destroy(algdict);
320	}
321	return 0;
322}
323