xref: /freebsd/contrib/libpcap/pcap-netfilter-linux.c (revision ddd5b8e9b4d8957fce018c520657cdfa4ecffad3)
1 /*
2  * Copyright (c) 2011 Jakub Zawadzki
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  *
9  * 1. Redistributions of source code must retain the above copyright
10  * notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  * notice, this list of conditions and the following disclaimer in the
13  * documentation and/or other materials provided with the distribution.
14  * 3. The name of the author may not be used to endorse or promote
15  * products derived from this software without specific prior written
16  * permission.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29  */
30 
31 #ifdef HAVE_CONFIG_H
32 #include "config.h"
33 #endif
34 
35 #include "pcap-int.h"
36 
37 #ifdef NEED_STRERROR_H
38 #include "strerror.h"
39 #endif
40 
41 #include <errno.h>
42 #include <stdlib.h>
43 #include <unistd.h>
44 #include <string.h>
45 #include <sys/socket.h>
46 #include <arpa/inet.h>
47 
48 #include <time.h>
49 #include <sys/time.h>
50 #include <netinet/in.h>
51 #include <linux/types.h>
52 
53 #include <linux/netlink.h>
54 #include <linux/netfilter/nfnetlink.h>
55 #include <linux/netfilter/nfnetlink_log.h>
56 
57 #include "pcap-netfilter-linux.h"
58 
59 #define HDR_LENGTH (NLMSG_LENGTH(NLMSG_ALIGN(sizeof(struct nfgenmsg))))
60 
61 #define NFLOG_IFACE "nflog"
62 
63 static int
64 nflog_read_linux(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user)
65 {
66 	const unsigned char *buf;
67 	int count = 0;
68 	int len;
69 
70 	/* ignore interrupt system call error */
71 	do {
72 		len = recv(handle->fd, handle->buffer, handle->bufsize, 0);
73 		if (handle->break_loop) {
74 			handle->break_loop = 0;
75 			return -2;
76 		}
77 	} while ((len == -1) && (errno == EINTR));
78 
79 	if (len < 0) {
80 		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't receive packet %d:%s", errno, pcap_strerror(errno));
81 		return -1;
82 	}
83 
84 	buf = handle->buffer;
85 	while (len >= NLMSG_SPACE(0)) {
86 		const struct nlmsghdr *nlh = (const struct nlmsghdr *) buf;
87 		u_int32_t msg_len;
88 
89 		if (nlh->nlmsg_len < sizeof(struct nlmsghdr) || len < nlh->nlmsg_len) {
90 			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Message truncated: (got: %d) (nlmsg_len: %u)", len, nlh->nlmsg_len);
91 			return -1;
92 		}
93 
94 		if (NFNL_SUBSYS_ID(nlh->nlmsg_type) == NFNL_SUBSYS_ULOG &&
95 			NFNL_MSG_TYPE(nlh->nlmsg_type) == NFULNL_MSG_PACKET)
96 		{
97 			const unsigned char *payload = NULL;
98 			struct pcap_pkthdr pkth;
99 
100 			if (handle->linktype != DLT_NFLOG) {
101 				const struct nfattr *payload_attr = NULL;
102 
103 				if (nlh->nlmsg_len < HDR_LENGTH) {
104 					snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Malformed message: (nlmsg_len: %u)", nlh->nlmsg_len);
105 					return -1;
106 				}
107 
108 				if (nlh->nlmsg_len > HDR_LENGTH) {
109 					struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
110 					int attr_len = nlh->nlmsg_len - NLMSG_ALIGN(HDR_LENGTH);
111 
112 					while (NFA_OK(attr, attr_len)) {
113 						switch (NFA_TYPE(attr)) {
114 							case NFULA_PAYLOAD:
115 								payload_attr = attr;
116 								break;
117 						}
118 						attr = NFA_NEXT(attr, attr_len);
119 					}
120 				}
121 
122 				if (payload_attr) {
123 					payload = NFA_DATA(payload_attr);
124 					pkth.len = pkth.caplen = NFA_PAYLOAD(payload_attr);
125 				}
126 
127 			} else {
128 				payload = NLMSG_DATA(nlh);
129 				pkth.caplen = pkth.len = nlh->nlmsg_len-NLMSG_ALIGN(sizeof(struct nlmsghdr));
130 			}
131 
132 			if (payload) {
133 				/* pkth.caplen = min (payload_len, handle->snapshot); */
134 
135 				gettimeofday(&pkth.ts, NULL);
136 				if (handle->fcode.bf_insns == NULL ||
137 						bpf_filter(handle->fcode.bf_insns, payload, pkth.len, pkth.caplen))
138 				{
139 					handle->md.packets_read++;
140 					callback(user, &pkth, payload);
141 					count++;
142 				}
143 			}
144 		}
145 
146 		msg_len = NLMSG_ALIGN(nlh->nlmsg_len);
147 		if (msg_len > len)
148 			msg_len = len;
149 
150 		len -= msg_len;
151 		buf += msg_len;
152 	}
153 	return count;
154 }
155 
156 static int
157 netfilter_set_datalink(pcap_t *handle, int dlt)
158 {
159 	handle->linktype = dlt;
160 	return 0;
161 }
162 
163 static int
164 netfilter_stats_linux(pcap_t *handle, struct pcap_stat *stats)
165 {
166 	stats->ps_recv = handle->md.packets_read;
167 	stats->ps_drop = 0;
168 	stats->ps_ifdrop = 0;
169 	return 0;
170 }
171 
172 static int
173 netfilter_inject_linux(pcap_t *handle, const void *buf, size_t size)
174 {
175 	snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "inject not supported on netfilter devices");
176 	return (-1);
177 }
178 
179 struct my_nfattr {
180 	u_int16_t nfa_len;
181 	u_int16_t nfa_type;
182 	void *data;
183 };
184 
185 static int
186 nflog_send_config_msg(const pcap_t *handle, u_int8_t family, u_int16_t res_id, const struct my_nfattr *mynfa)
187 {
188 	char buf[1024] __attribute__ ((aligned));
189 
190 	struct nlmsghdr *nlh = (struct nlmsghdr *) buf;
191 	struct nfgenmsg *nfg = (struct nfgenmsg *) (buf + sizeof(struct nlmsghdr));
192 
193 	struct sockaddr_nl snl;
194 	static unsigned int seq_id;
195 
196 	if (!seq_id)
197 		seq_id = time(NULL);
198 	++seq_id;
199 
200 	nlh->nlmsg_len = NLMSG_LENGTH(sizeof(struct nfgenmsg));
201 	nlh->nlmsg_type = (NFNL_SUBSYS_ULOG << 8) | NFULNL_MSG_CONFIG;
202 	nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
203 	nlh->nlmsg_pid = 0;	/* to kernel */
204 	nlh->nlmsg_seq = seq_id;
205 
206 	nfg->nfgen_family = family;
207 	nfg->version = NFNETLINK_V0;
208 	nfg->res_id = htons(res_id);
209 
210 	if (mynfa) {
211 		struct nfattr *nfa = (struct nfattr *) (buf + NLMSG_ALIGN(nlh->nlmsg_len));
212 
213 		nfa->nfa_type = mynfa->nfa_type;
214 		nfa->nfa_len = NFA_LENGTH(mynfa->nfa_len);
215 		memcpy(NFA_DATA(nfa), mynfa->data, mynfa->nfa_len);
216 		nlh->nlmsg_len = NLMSG_ALIGN(nlh->nlmsg_len) + NFA_ALIGN(nfa->nfa_len);
217 	}
218 
219 	memset(&snl, 0, sizeof(snl));
220 	snl.nl_family = AF_NETLINK;
221 
222 	if (sendto(handle->fd, nlh, nlh->nlmsg_len, 0, (struct sockaddr *) &snl, sizeof(snl)) == -1)
223 		return -1;
224 
225 	/* waiting for reply loop */
226 	do {
227 		socklen_t addrlen = sizeof(snl);
228 		int len;
229 
230 		/* ignore interrupt system call error */
231 		do {
232 			len = recvfrom(handle->fd, buf, sizeof(buf), 0, (struct sockaddr *) &snl, &addrlen);
233 		} while ((len == -1) && (errno == EINTR));
234 
235 		if (len <= 0)
236 			return len;
237 
238 		if (addrlen != sizeof(snl) || snl.nl_family != AF_NETLINK) {
239 			errno = EINVAL;
240 			return -1;
241 		}
242 
243 		nlh = (struct nlmsghdr *) buf;
244 		if (snl.nl_pid != 0 || seq_id != nlh->nlmsg_seq)	/* if not from kernel or wrong sequence skip */
245 			continue;
246 
247 		while (len >= NLMSG_SPACE(0) && NLMSG_OK(nlh, len)) {
248 			if (nlh->nlmsg_type == NLMSG_ERROR || (nlh->nlmsg_type == NLMSG_DONE && nlh->nlmsg_flags & NLM_F_MULTI)) {
249 				if (nlh->nlmsg_len < NLMSG_ALIGN(sizeof(struct nlmsgerr))) {
250 					errno = EBADMSG;
251 					return -1;
252 				}
253 				errno = -(*((int *)NLMSG_DATA(nlh)));
254 				return (errno == 0) ? 0 : -1;
255 			}
256 			nlh = NLMSG_NEXT(nlh, len);
257 		}
258 	} while (1);
259 
260 	return -1; /* never here */
261 }
262 
263 static int
264 nflog_send_config_cmd(const pcap_t *handle, u_int16_t group_id, u_int8_t cmd, u_int8_t family)
265 {
266 	struct nfulnl_msg_config_cmd msg;
267 	struct my_nfattr nfa;
268 
269 	msg.command = cmd;
270 
271 	nfa.data = &msg;
272 	nfa.nfa_type = NFULA_CFG_CMD;
273 	nfa.nfa_len = sizeof(msg);
274 
275 	return nflog_send_config_msg(handle, family, group_id, &nfa);
276 }
277 
278 static int
279 nflog_send_config_mode(const pcap_t *handle, u_int16_t group_id, u_int8_t copy_mode, u_int32_t copy_range)
280 {
281 	struct nfulnl_msg_config_mode msg;
282 	struct my_nfattr nfa;
283 
284 	msg.copy_range = htonl(copy_range);
285 	msg.copy_mode = copy_mode;
286 
287 	nfa.data = &msg;
288 	nfa.nfa_type = NFULA_CFG_MODE;
289 	nfa.nfa_len = sizeof(msg);
290 
291 	return nflog_send_config_msg(handle, AF_UNSPEC, group_id, &nfa);
292 }
293 
294 static int
295 nflog_activate(pcap_t* handle)
296 {
297 	const char *dev = handle->opt.source;
298 	unsigned short groups[32];
299 	int group_count = 0;
300 	int i;
301 
302 	if (strncmp(dev, NFLOG_IFACE, strlen(NFLOG_IFACE)) == 0) {
303 		dev += strlen(NFLOG_IFACE);
304 
305 		/* nflog:30,33,42 looks nice, allow it */
306 		if (*dev == ':')
307 			dev++;
308 
309 		while (*dev) {
310 			long int group_id;
311 			char *end_dev;
312 
313 			if (group_count == 32) {
314 				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
315 						"Maximum 32 netfilter groups! dev: %s",
316 						handle->opt.source);
317 				return PCAP_ERROR;
318 			}
319 
320 			group_id = strtol(dev, &end_dev, 0);
321 			if (end_dev != dev) {
322 				if (group_id < 0 || group_id > 65535) {
323 					snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
324 							"Netfilter group range from 0 to 65535 (got %ld)",
325 							group_id);
326 					return PCAP_ERROR;
327 				}
328 
329 				groups[group_count++] = (unsigned short) group_id;
330 				dev = end_dev;
331 			}
332 			if (*dev != ',')
333 				break;
334 			dev++;
335 		}
336 	}
337 
338 	if (*dev) {
339 		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
340 				"Can't get netfilter group(s) index from %s",
341 				handle->opt.source);
342 		return PCAP_ERROR;
343 	}
344 
345 	/* if no groups, add default: 0 */
346 	if (!group_count) {
347 		groups[0] = 0;
348 		group_count = 1;
349 	}
350 
351 	/* Initialize some components of the pcap structure. */
352 	handle->bufsize = 128 + handle->snapshot;
353 	handle->offset = 0;
354 	handle->linktype = DLT_NFLOG;
355 	handle->read_op = nflog_read_linux;
356 	handle->inject_op = netfilter_inject_linux;
357 	handle->setfilter_op = install_bpf_program; /* no kernel filtering */
358 	handle->setdirection_op = NULL;
359 	handle->set_datalink_op = NULL;
360 	handle->set_datalink_op = netfilter_set_datalink;
361 	handle->getnonblock_op = pcap_getnonblock_fd;
362 	handle->setnonblock_op = pcap_setnonblock_fd;
363 	handle->stats_op = netfilter_stats_linux;
364 
365 	/* Create netlink socket */
366 	handle->fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_NETFILTER);
367 	if (handle->fd < 0) {
368 		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't create raw socket %d:%s", errno, pcap_strerror(errno));
369 		return PCAP_ERROR;
370 	}
371 
372 	handle->dlt_list = (u_int *) malloc(sizeof(u_int) * 2);
373 	if (handle->dlt_list != NULL) {
374 		handle->dlt_list[0] = DLT_NFLOG;
375 		handle->dlt_list[1] = DLT_IPV4;
376 		handle->dlt_count = 2;
377 	}
378 
379 	handle->buffer = malloc(handle->bufsize);
380 	if (!handle->buffer) {
381 		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't allocate dump buffer: %s", pcap_strerror(errno));
382 		goto close_fail;
383 	}
384 
385 	if (nflog_send_config_cmd(handle, 0, NFULNL_CFG_CMD_PF_UNBIND, AF_INET) < 0) {
386 		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFULNL_CFG_CMD_PF_UNBIND: %s", pcap_strerror(errno));
387 		goto close_fail;
388 	}
389 
390 	if (nflog_send_config_cmd(handle, 0, NFULNL_CFG_CMD_PF_BIND, AF_INET) < 0) {
391 		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFULNL_CFG_CMD_PF_BIND: %s", pcap_strerror(errno));
392 		goto close_fail;
393 	}
394 
395 	/* Bind socket to the nflog groups */
396 	for (i = 0; i < group_count; i++) {
397 		if (nflog_send_config_cmd(handle, groups[i], NFULNL_CFG_CMD_BIND, AF_UNSPEC) < 0) {
398 			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't listen on group group index: %s", pcap_strerror(errno));
399 			goto close_fail;
400 		}
401 
402 		if (nflog_send_config_mode(handle, groups[i], NFULNL_COPY_PACKET, handle->snapshot) < 0) {
403 			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFULNL_COPY_PACKET: %s", pcap_strerror(errno));
404 			goto close_fail;
405 		}
406 	}
407 
408 	if (handle->opt.rfmon) {
409 		/*
410 		 * Monitor mode doesn't apply to netfilter devices.
411 		 */
412 		pcap_cleanup_live_common(handle);
413 		return PCAP_ERROR_RFMON_NOTSUP;
414 	}
415 
416 	if (handle->opt.buffer_size != 0) {
417 		/*
418 		 * Set the socket buffer size to the specified value.
419 		 */
420 		if (setsockopt(handle->fd, SOL_SOCKET, SO_RCVBUF, &handle->opt.buffer_size, sizeof(handle->opt.buffer_size)) == -1) {
421 			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "SO_RCVBUF: %s", pcap_strerror(errno));
422 			goto close_fail;
423 		}
424 	}
425 
426 	handle->selectable_fd = handle->fd;
427 	return 0;
428 
429 close_fail:
430 	pcap_cleanup_live_common(handle);
431 	return PCAP_ERROR;
432 }
433 
434 pcap_t *
435 nflog_create(const char *device, char *ebuf)
436 {
437 	pcap_t *p;
438 
439 	p = pcap_create_common(device, ebuf);
440 	if (p == NULL)
441 		return (NULL);
442 
443 	p->activate_op = nflog_activate;
444 	return (p);
445 }
446 
447 int
448 netfilter_platform_finddevs(pcap_if_t **alldevsp, char *err_str)
449 {
450 	pcap_if_t *found_dev = *alldevsp;
451 	int sock;
452 
453 	sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_NETFILTER);
454 	if (sock < 0) {
455 		/* if netlink is not supported this is not fatal */
456 		if (errno == EAFNOSUPPORT || errno == EPROTONOSUPPORT)
457 			return 0;
458 		snprintf(err_str, PCAP_ERRBUF_SIZE, "Can't open netlink socket %d:%s",
459 			errno, pcap_strerror(errno));
460 		return -1;
461 	}
462 	close(sock);
463 
464 	if (pcap_add_if(&found_dev, NFLOG_IFACE, 0, "Linux netfilter log (NFLOG) interface", err_str) < 0)
465 		return -1;
466 	return 0;
467 }
468 
469