pflogd.c revision 130617 
1/*	$OpenBSD: pflogd.c,v 1.27 2004/02/13 19:01:57 otto Exp $	*/
2
3/*
4 * Copyright (c) 2001 Theo de Raadt
5 * Copyright (c) 2001 Can Erkin Acar
6 * All rights reserved.
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 *
12 *    - Redistributions of source code must retain the above copyright
13 *      notice, this list of conditions and the following disclaimer.
14 *    - Redistributions in binary form must reproduce the above
15 *      copyright notice, this list of conditions and the following
16 *      disclaimer in the documentation and/or other materials provided
17 *      with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
22 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
23 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
24 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
25 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
26 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
27 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
29 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
30 * POSSIBILITY OF SUCH DAMAGE.
31 */
32
33#include <sys/cdefs.h>
34__FBSDID("$FreeBSD: head/contrib/pf/pflogd/pflogd.c 130617 2004-06-16 23:39:33Z mlaier $");
35
36#include <sys/types.h>
37#include <sys/ioctl.h>
38#include <sys/file.h>
39#include <sys/stat.h>
40#include <stdio.h>
41#include <stdlib.h>
42#include <string.h>
43#include <unistd.h>
44#include <pcap-int.h>
45#include <pcap.h>
46#include <syslog.h>
47#include <signal.h>
48#include <errno.h>
49#include <stdarg.h>
50#include <fcntl.h>
51#ifdef __FreeBSD__
52#include "pidfile.h"
53#else
54#include <util.h>
55#endif
56
57#include "pflogd.h"
58
59pcap_t *hpcap;
60static FILE *dpcap;
61
62int Debug = 0;
63static int snaplen = DEF_SNAPLEN;
64static int cur_snaplen = DEF_SNAPLEN;
65
66volatile sig_atomic_t gotsig_close, gotsig_alrm, gotsig_hup;
67
68char *filename = PFLOGD_LOG_FILE;
69char *interface = PFLOGD_DEFAULT_IF;
70char *filter = NULL;
71
72char errbuf[PCAP_ERRBUF_SIZE];
73
74int log_debug = 0;
75unsigned int delay = FLUSH_DELAY;
76
77char *copy_argv(char * const *);
78void  dump_packet(u_char *, const struct pcap_pkthdr *, const u_char *);
79void  dump_packet_nobuf(u_char *, const struct pcap_pkthdr *, const u_char *);
80int   flush_buffer(FILE *);
81int   init_pcap(void);
82void  logmsg(int, const char *, ...);
83void  purge_buffer(void);
84int   reset_dump(void);
85int   scan_dump(FILE *, off_t);
86int   set_snaplen(int);
87void  set_suspended(int);
88void  sig_alrm(int);
89void  sig_close(int);
90void  sig_hup(int);
91void  usage(void);
92
93/* buffer must always be greater than snaplen */
94static int    bufpkt = 0;	/* number of packets in buffer */
95static int    buflen = 0;	/* allocated size of buffer */
96static char  *buffer = NULL;	/* packet buffer */
97static char  *bufpos = NULL;	/* position in buffer */
98static int    bufleft = 0;	/* bytes left in buffer */
99
100/* if error, stop logging but count dropped packets */
101static int suspended = -1;
102static long packets_dropped = 0;
103
104void
105set_suspended(int s)
106{
107	if (suspended == s)
108		return;
109
110	suspended = s;
111	setproctitle("[%s] -s %d -f %s",
112            suspended ? "suspended" : "running", cur_snaplen, filename);
113}
114
115char *
116copy_argv(char * const *argv)
117{
118	size_t len = 0, n;
119	char *buf;
120
121	if (argv == NULL)
122		return (NULL);
123
124	for (n = 0; argv[n]; n++)
125		len += strlen(argv[n])+1;
126	if (len == 0)
127		return (NULL);
128
129	buf = malloc(len);
130	if (buf == NULL)
131		return (NULL);
132
133	strlcpy(buf, argv[0], len);
134	for (n = 1; argv[n]; n++) {
135		strlcat(buf, " ", len);
136		strlcat(buf, argv[n], len);
137	}
138	return (buf);
139}
140
141void
142logmsg(int pri, const char *message, ...)
143{
144	va_list ap;
145	va_start(ap, message);
146
147	if (log_debug) {
148		vfprintf(stderr, message, ap);
149		fprintf(stderr, "\n");
150	} else
151		vsyslog(pri, message, ap);
152	va_end(ap);
153}
154
155#ifdef __FreeBSD__
156__dead2 void
157#else
158__dead void
159#endif
160usage(void)
161{
162	fprintf(stderr, "usage: pflogd [-Dx] [-d delay] [-f filename] ");
163	fprintf(stderr, "[-s snaplen] [expression]\n");
164	exit(1);
165}
166
167void
168sig_close(int sig)
169{
170	gotsig_close = 1;
171}
172
173void
174sig_hup(int sig)
175{
176	gotsig_hup = 1;
177}
178
179void
180sig_alrm(int sig)
181{
182	gotsig_alrm = 1;
183}
184
185void
186set_pcap_filter(void)
187{
188	struct bpf_program bprog;
189
190	if (pcap_compile(hpcap, &bprog, filter, PCAP_OPT_FIL, 0) < 0)
191		logmsg(LOG_WARNING, "%s", pcap_geterr(hpcap));
192	else {
193		if (pcap_setfilter(hpcap, &bprog) < 0)
194			logmsg(LOG_WARNING, "%s", pcap_geterr(hpcap));
195		pcap_freecode(&bprog);
196	}
197}
198
199int
200init_pcap(void)
201{
202	hpcap = pcap_open_live(interface, snaplen, 1, PCAP_TO_MS, errbuf);
203	if (hpcap == NULL) {
204		logmsg(LOG_ERR, "Failed to initialize: %s", errbuf);
205		return (-1);
206	}
207
208	if (pcap_datalink(hpcap) != DLT_PFLOG) {
209		logmsg(LOG_ERR, "Invalid datalink type");
210		pcap_close(hpcap);
211		hpcap = NULL;
212		return (-1);
213	}
214
215	set_pcap_filter();
216
217	cur_snaplen = snaplen = pcap_snapshot(hpcap);
218
219#ifdef __FreeBSD__
220	/* We can not lock bpf devices ... yet */
221#else
222	/* lock */
223	if (ioctl(pcap_fileno(hpcap), BIOCLOCK) < 0) {
224		logmsg(LOG_ERR, "BIOCLOCK: %s", strerror(errno));
225		return (-1);
226	}
227#endif
228
229	return (0);
230}
231
232int
233set_snaplen(int snap)
234{
235	if (priv_set_snaplen(snap))
236		return (1);
237
238	if (cur_snaplen > snap)
239		purge_buffer();
240
241	cur_snaplen = snap;
242
243	return (0);
244}
245
246int
247reset_dump(void)
248{
249	struct pcap_file_header hdr;
250	struct stat st;
251	int fd;
252	FILE *fp;
253
254	if (hpcap == NULL)
255		return (-1);
256
257	if (dpcap) {
258		flush_buffer(dpcap);
259		fclose(dpcap);
260		dpcap = NULL;
261	}
262
263	/*
264	 * Basically reimplement pcap_dump_open() because it truncates
265	 * files and duplicates headers and such.
266	 */
267	fd = priv_open_log();
268	if (fd < 0)
269		return (1);
270
271	fp = fdopen(fd, "a+");
272
273	if (fp == NULL) {
274		logmsg(LOG_ERR, "Error: %s: %s", filename, strerror(errno));
275		return (1);
276	}
277	if (fstat(fileno(fp), &st) == -1) {
278		logmsg(LOG_ERR, "Error: %s: %s", filename, strerror(errno));
279		return (1);
280	}
281
282	/* set FILE unbuffered, we do our own buffering */
283	if (setvbuf(fp, NULL, _IONBF, 0)) {
284		logmsg(LOG_ERR, "Failed to set output buffers");
285		return (1);
286	}
287
288#define TCPDUMP_MAGIC 0xa1b2c3d4
289
290	if (st.st_size == 0) {
291		if (snaplen != cur_snaplen) {
292			logmsg(LOG_NOTICE, "Using snaplen %d", snaplen);
293			if (set_snaplen(snaplen)) {
294				logmsg(LOG_WARNING,
295				    "Failed, using old settings");
296			}
297		}
298		hdr.magic = TCPDUMP_MAGIC;
299		hdr.version_major = PCAP_VERSION_MAJOR;
300		hdr.version_minor = PCAP_VERSION_MINOR;
301		hdr.thiszone = hpcap->tzoff;
302		hdr.snaplen = hpcap->snapshot;
303		hdr.sigfigs = 0;
304		hdr.linktype = hpcap->linktype;
305
306		if (fwrite((char *)&hdr, sizeof(hdr), 1, fp) != 1) {
307			fclose(fp);
308			return (1);
309		}
310	} else if (scan_dump(fp, st.st_size)) {
311		/* XXX move file and continue? */
312		fclose(fp);
313		return (1);
314	}
315
316	dpcap = fp;
317
318	set_suspended(0);
319	flush_buffer(fp);
320
321	return (0);
322}
323
324int
325scan_dump(FILE *fp, off_t size)
326{
327	struct pcap_file_header hdr;
328	struct pcap_pkthdr ph;
329	off_t pos;
330
331	/*
332	 * Must read the file, compare the header against our new
333	 * options (in particular, snaplen) and adjust our options so
334	 * that we generate a correct file. Furthermore, check the file
335	 * for consistency so that we can append safely.
336	 *
337	 * XXX this may take a long time for large logs.
338	 */
339	(void) fseek(fp, 0L, SEEK_SET);
340
341	if (fread((char *)&hdr, sizeof(hdr), 1, fp) != 1) {
342		logmsg(LOG_ERR, "Short file header");
343		return (1);
344	}
345
346	if (hdr.magic != TCPDUMP_MAGIC ||
347	    hdr.version_major != PCAP_VERSION_MAJOR ||
348	    hdr.version_minor != PCAP_VERSION_MINOR ||
349	    hdr.linktype != hpcap->linktype ||
350	    hdr.snaplen > PFLOGD_MAXSNAPLEN) {
351		logmsg(LOG_ERR, "Invalid/incompatible log file, move it away");
352		return (1);
353	}
354
355	pos = sizeof(hdr);
356
357	while (!feof(fp)) {
358		off_t len = fread((char *)&ph, 1, sizeof(ph), fp);
359		if (len == 0)
360			break;
361
362		if (len != sizeof(ph))
363			goto error;
364		if (ph.caplen > hdr.snaplen || ph.caplen > PFLOGD_MAXSNAPLEN)
365			goto error;
366		pos += sizeof(ph) + ph.caplen;
367		if (pos > size)
368			goto error;
369		fseek(fp, ph.caplen, SEEK_CUR);
370	}
371
372	if (pos != size)
373		goto error;
374
375	if (hdr.snaplen != cur_snaplen) {
376		logmsg(LOG_WARNING,
377		       "Existing file has different snaplen %u, using it",
378		       hdr.snaplen);
379		if (set_snaplen(hdr.snaplen)) {
380			logmsg(LOG_WARNING,
381			       "Failed, using old settings, offset %llu",
382			       (unsigned long long) size);
383		}
384	}
385
386	return (0);
387
388 error:
389	logmsg(LOG_ERR, "Corrupted log file.");
390	return (1);
391}
392
393/* dump a packet directly to the stream, which is unbuffered */
394void
395dump_packet_nobuf(u_char *user, const struct pcap_pkthdr *h, const u_char *sp)
396{
397	FILE *f = (FILE *)user;
398
399	if (suspended) {
400		packets_dropped++;
401		return;
402	}
403
404	if (fwrite((char *)h, sizeof(*h), 1, f) != 1) {
405		/* try to undo header to prevent corruption */
406		off_t pos = ftello(f);
407		if (pos < sizeof(*h) ||
408		    ftruncate(fileno(f), pos - sizeof(*h))) {
409			logmsg(LOG_ERR, "Write failed, corrupted logfile!");
410			set_suspended(1);
411			gotsig_close = 1;
412			return;
413		}
414		goto error;
415	}
416
417	if (fwrite((char *)sp, h->caplen, 1, f) != 1)
418		goto error;
419
420	return;
421
422error:
423	set_suspended(1);
424	packets_dropped ++;
425	logmsg(LOG_ERR, "Logging suspended: fwrite: %s", strerror(errno));
426}
427
428int
429flush_buffer(FILE *f)
430{
431	off_t offset;
432	int len = bufpos - buffer;
433
434	if (len <= 0)
435		return (0);
436
437	offset = ftello(f);
438	if (offset == (off_t)-1) {
439		set_suspended(1);
440		logmsg(LOG_ERR, "Logging suspended: ftello: %s",
441		    strerror(errno));
442		return (1);
443	}
444
445	if (fwrite(buffer, len, 1, f) != 1) {
446		set_suspended(1);
447		logmsg(LOG_ERR, "Logging suspended: fwrite: %s",
448		    strerror(errno));
449		ftruncate(fileno(f), offset);
450		return (1);
451	}
452
453	set_suspended(0);
454	bufpos = buffer;
455	bufleft = buflen;
456	bufpkt = 0;
457
458	return (0);
459}
460
461void
462purge_buffer(void)
463{
464	packets_dropped += bufpkt;
465
466	set_suspended(0);
467	bufpos = buffer;
468	bufleft = buflen;
469	bufpkt = 0;
470}
471
472/* append packet to the buffer, flushing if necessary */
473void
474dump_packet(u_char *user, const struct pcap_pkthdr *h, const u_char *sp)
475{
476	FILE *f = (FILE *)user;
477	size_t len = sizeof(*h) + h->caplen;
478
479	if (len < sizeof(*h) || h->caplen > (size_t)cur_snaplen) {
480		logmsg(LOG_NOTICE, "invalid size %u (%u/%u), packet dropped",
481		       len, cur_snaplen, snaplen);
482		packets_dropped++;
483		return;
484	}
485
486	if (len <= bufleft)
487		goto append;
488
489	if (suspended) {
490		packets_dropped++;
491		return;
492	}
493
494	if (flush_buffer(f)) {
495		packets_dropped++;
496		return;
497	}
498
499	if (len > bufleft) {
500		dump_packet_nobuf(user, h, sp);
501		return;
502	}
503
504 append:
505	memcpy(bufpos, h, sizeof(*h));
506	memcpy(bufpos + sizeof(*h), sp, h->caplen);
507
508	bufpos += len;
509	bufleft -= len;
510	bufpkt++;
511
512	return;
513}
514
515int
516main(int argc, char **argv)
517{
518	struct pcap_stat pstat;
519	int ch, np, Xflag = 0;
520	pcap_handler phandler = dump_packet;
521
522#ifdef __FreeBSD__
523	/* another ?paranoid? safety measure we do not have */
524#else
525	closefrom(STDERR_FILENO + 1);
526#endif
527
528	while ((ch = getopt(argc, argv, "Dxd:s:f:")) != -1) {
529		switch (ch) {
530		case 'D':
531			Debug = 1;
532			break;
533		case 'd':
534			delay = atoi(optarg);
535			if (delay < 5 || delay > 60*60)
536				usage();
537			break;
538		case 'f':
539			filename = optarg;
540			break;
541		case 's':
542			snaplen = atoi(optarg);
543			if (snaplen <= 0)
544				snaplen = DEF_SNAPLEN;
545			if (snaplen > PFLOGD_MAXSNAPLEN)
546				snaplen = PFLOGD_MAXSNAPLEN;
547			break;
548		case 'x':
549			Xflag++;
550			break;
551		default:
552			usage();
553		}
554
555	}
556
557	log_debug = Debug;
558	argc -= optind;
559	argv += optind;
560
561	if (!Debug) {
562		openlog("pflogd", LOG_PID | LOG_CONS, LOG_DAEMON);
563		if (daemon(0, 0)) {
564			logmsg(LOG_WARNING, "Failed to become daemon: %s",
565			    strerror(errno));
566		}
567		pidfile(NULL);
568	}
569
570	(void)umask(S_IRWXG | S_IRWXO);
571
572	/* filter will be used by the privileged process */
573	if (argc) {
574		filter = copy_argv(argv);
575		if (filter == NULL)
576			logmsg(LOG_NOTICE, "Failed to form filter expression");
577	}
578
579	/* initialize pcap before dropping privileges */
580	if (init_pcap()) {
581		logmsg(LOG_ERR, "Exiting, init failure");
582		exit(1);
583	}
584
585	/* Privilege separation begins here */
586	if (priv_init()) {
587		logmsg(LOG_ERR, "unable to privsep");
588		exit(1);
589	}
590
591	setproctitle("[initializing]");
592	/* Process is now unprivileged and inside a chroot */
593	signal(SIGTERM, sig_close);
594	signal(SIGINT, sig_close);
595	signal(SIGQUIT, sig_close);
596	signal(SIGALRM, sig_alrm);
597	signal(SIGHUP, sig_hup);
598	alarm(delay);
599
600	buffer = malloc(PFLOGD_BUFSIZE);
601
602	if (buffer == NULL) {
603		logmsg(LOG_WARNING, "Failed to allocate output buffer");
604		phandler = dump_packet_nobuf;
605	} else {
606		bufleft = buflen = PFLOGD_BUFSIZE;
607		bufpos = buffer;
608		bufpkt = 0;
609	}
610
611	if (reset_dump()) {
612		if (Xflag)
613			return (1);
614
615		logmsg(LOG_ERR, "Logging suspended: open error");
616		set_suspended(1);
617	} else if (Xflag)
618		return (0);
619
620	while (1) {
621		np = pcap_dispatch(hpcap, PCAP_NUM_PKTS,
622		    dump_packet, (u_char *)dpcap);
623		if (np < 0)
624			logmsg(LOG_NOTICE, "%s", pcap_geterr(hpcap));
625
626		if (gotsig_close)
627			break;
628		if (gotsig_hup) {
629			if (reset_dump()) {
630				logmsg(LOG_ERR,
631				    "Logging suspended: open error");
632				set_suspended(1);
633			}
634			gotsig_hup = 0;
635		}
636
637		if (gotsig_alrm) {
638			if (dpcap)
639				flush_buffer(dpcap);
640			gotsig_alrm = 0;
641			alarm(delay);
642		}
643	}
644
645	logmsg(LOG_NOTICE, "Exiting");
646	if (dpcap) {
647		flush_buffer(dpcap);
648		fclose(dpcap);
649	}
650	purge_buffer();
651
652	if (pcap_stats(hpcap, &pstat) < 0)
653		logmsg(LOG_WARNING, "Reading stats: %s", pcap_geterr(hpcap));
654	else
655		logmsg(LOG_NOTICE,
656		    "%u packets received, %u/%u dropped (kernel/pflogd)",
657		    pstat.ps_recv, pstat.ps_drop, packets_dropped);
658
659	pcap_close(hpcap);
660	if (!Debug)
661		closelog();
662	return (0);
663}
664