pflogd.c revision 134578 
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 134578 2004-08-31 18:04:34Z 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#ifdef __FreeBSD__
329	struct pcap_sf_pkthdr ph;
330#else
331	struct pcap_pkthdr ph;
332#endif
333	off_t pos;
334
335	/*
336	 * Must read the file, compare the header against our new
337	 * options (in particular, snaplen) and adjust our options so
338	 * that we generate a correct file. Furthermore, check the file
339	 * for consistency so that we can append safely.
340	 *
341	 * XXX this may take a long time for large logs.
342	 */
343	(void) fseek(fp, 0L, SEEK_SET);
344
345	if (fread((char *)&hdr, sizeof(hdr), 1, fp) != 1) {
346		logmsg(LOG_ERR, "Short file header");
347		return (1);
348	}
349
350	if (hdr.magic != TCPDUMP_MAGIC ||
351	    hdr.version_major != PCAP_VERSION_MAJOR ||
352	    hdr.version_minor != PCAP_VERSION_MINOR ||
353	    hdr.linktype != hpcap->linktype ||
354	    hdr.snaplen > PFLOGD_MAXSNAPLEN) {
355		logmsg(LOG_ERR, "Invalid/incompatible log file, move it away");
356		return (1);
357	}
358
359	pos = sizeof(hdr);
360
361	while (!feof(fp)) {
362		off_t len = fread((char *)&ph, 1, sizeof(ph), fp);
363		if (len == 0)
364			break;
365
366		if (len != sizeof(ph))
367			goto error;
368		if (ph.caplen > hdr.snaplen || ph.caplen > PFLOGD_MAXSNAPLEN)
369			goto error;
370		pos += sizeof(ph) + ph.caplen;
371		if (pos > size)
372			goto error;
373		fseek(fp, ph.caplen, SEEK_CUR);
374	}
375
376	if (pos != size)
377		goto error;
378
379	if (hdr.snaplen != cur_snaplen) {
380		logmsg(LOG_WARNING,
381		       "Existing file has different snaplen %u, using it",
382		       hdr.snaplen);
383		if (set_snaplen(hdr.snaplen)) {
384			logmsg(LOG_WARNING,
385			       "Failed, using old settings, offset %llu",
386			       (unsigned long long) size);
387		}
388	}
389
390	return (0);
391
392 error:
393	logmsg(LOG_ERR, "Corrupted log file.");
394	return (1);
395}
396
397/* dump a packet directly to the stream, which is unbuffered */
398void
399dump_packet_nobuf(u_char *user, const struct pcap_pkthdr *h, const u_char *sp)
400{
401	FILE *f = (FILE *)user;
402#ifdef __FreeBSD__
403	struct pcap_sf_pkthdr sh;
404#endif
405
406	if (suspended) {
407		packets_dropped++;
408		return;
409	}
410
411#ifdef __FreeBSD__
412	sh.ts.tv_sec = (bpf_int32)h->ts.tv_sec;
413	sh.ts.tv_usec = (bpf_int32)h->ts.tv_usec;
414	sh.caplen = h->caplen;
415	sh.len = h->len;
416
417	if (fwrite((char *)&sh, sizeof(sh), 1, f) != 1) {
418#else
419	if (fwrite((char *)h, sizeof(*h), 1, f) != 1) {
420#endif
421		/* try to undo header to prevent corruption */
422		off_t pos = ftello(f);
423#ifdef __FreeBSD__
424		if (pos < sizeof(sh) ||
425		    ftruncate(fileno(f), pos - sizeof(sh))) {
426#else
427		if (pos < sizeof(*h) ||
428		    ftruncate(fileno(f), pos - sizeof(*h))) {
429#endif
430			logmsg(LOG_ERR, "Write failed, corrupted logfile!");
431			set_suspended(1);
432			gotsig_close = 1;
433			return;
434		}
435		goto error;
436	}
437
438	if (fwrite((char *)sp, h->caplen, 1, f) != 1)
439		goto error;
440
441	return;
442
443error:
444	set_suspended(1);
445	packets_dropped ++;
446	logmsg(LOG_ERR, "Logging suspended: fwrite: %s", strerror(errno));
447}
448
449int
450flush_buffer(FILE *f)
451{
452	off_t offset;
453	int len = bufpos - buffer;
454
455	if (len <= 0)
456		return (0);
457
458	offset = ftello(f);
459	if (offset == (off_t)-1) {
460		set_suspended(1);
461		logmsg(LOG_ERR, "Logging suspended: ftello: %s",
462		    strerror(errno));
463		return (1);
464	}
465
466	if (fwrite(buffer, len, 1, f) != 1) {
467		set_suspended(1);
468		logmsg(LOG_ERR, "Logging suspended: fwrite: %s",
469		    strerror(errno));
470		ftruncate(fileno(f), offset);
471		return (1);
472	}
473
474	set_suspended(0);
475	bufpos = buffer;
476	bufleft = buflen;
477	bufpkt = 0;
478
479	return (0);
480}
481
482void
483purge_buffer(void)
484{
485	packets_dropped += bufpkt;
486
487	set_suspended(0);
488	bufpos = buffer;
489	bufleft = buflen;
490	bufpkt = 0;
491}
492
493/* append packet to the buffer, flushing if necessary */
494void
495dump_packet(u_char *user, const struct pcap_pkthdr *h, const u_char *sp)
496{
497	FILE *f = (FILE *)user;
498#ifdef __FreeBSD__
499	struct pcap_sf_pkthdr sh;
500	size_t len = sizeof(sh) + h->caplen;
501#else
502	size_t len = sizeof(*h) + h->caplen;
503#endif
504
505	if (len < sizeof(*h) || h->caplen > (size_t)cur_snaplen) {
506		logmsg(LOG_NOTICE, "invalid size %u (%u/%u), packet dropped",
507		       len, cur_snaplen, snaplen);
508		packets_dropped++;
509		return;
510	}
511
512	if (len <= bufleft)
513		goto append;
514
515	if (suspended) {
516		packets_dropped++;
517		return;
518	}
519
520	if (flush_buffer(f)) {
521		packets_dropped++;
522		return;
523	}
524
525	if (len > bufleft) {
526		dump_packet_nobuf(user, h, sp);
527		return;
528	}
529
530 append:
531#ifdef __FreeBSD__
532 	sh.ts.tv_sec = (bpf_int32)h->ts.tv_sec;
533 	sh.ts.tv_usec = (bpf_int32)h->ts.tv_usec;
534	sh.caplen = h->caplen;
535	sh.len = h->len;
536
537	memcpy(bufpos, &sh, sizeof(sh));
538	memcpy(bufpos + sizeof(sh), sp, h->caplen);
539#else
540	memcpy(bufpos, h, sizeof(*h));
541	memcpy(bufpos + sizeof(*h), sp, h->caplen);
542#endif
543
544	bufpos += len;
545	bufleft -= len;
546	bufpkt++;
547
548	return;
549}
550
551int
552main(int argc, char **argv)
553{
554	struct pcap_stat pstat;
555	int ch, np, Xflag = 0;
556	pcap_handler phandler = dump_packet;
557
558#ifdef __FreeBSD__
559	/* another ?paranoid? safety measure we do not have */
560#else
561	closefrom(STDERR_FILENO + 1);
562#endif
563
564	while ((ch = getopt(argc, argv, "Dxd:s:f:")) != -1) {
565		switch (ch) {
566		case 'D':
567			Debug = 1;
568			break;
569		case 'd':
570			delay = atoi(optarg);
571			if (delay < 5 || delay > 60*60)
572				usage();
573			break;
574		case 'f':
575			filename = optarg;
576			break;
577		case 's':
578			snaplen = atoi(optarg);
579			if (snaplen <= 0)
580				snaplen = DEF_SNAPLEN;
581			if (snaplen > PFLOGD_MAXSNAPLEN)
582				snaplen = PFLOGD_MAXSNAPLEN;
583			break;
584		case 'x':
585			Xflag++;
586			break;
587		default:
588			usage();
589		}
590
591	}
592
593	log_debug = Debug;
594	argc -= optind;
595	argv += optind;
596
597	if (!Debug) {
598		openlog("pflogd", LOG_PID | LOG_CONS, LOG_DAEMON);
599		if (daemon(0, 0)) {
600			logmsg(LOG_WARNING, "Failed to become daemon: %s",
601			    strerror(errno));
602		}
603		pidfile(NULL);
604	}
605
606	(void)umask(S_IRWXG | S_IRWXO);
607
608	/* filter will be used by the privileged process */
609	if (argc) {
610		filter = copy_argv(argv);
611		if (filter == NULL)
612			logmsg(LOG_NOTICE, "Failed to form filter expression");
613	}
614
615	/* initialize pcap before dropping privileges */
616	if (init_pcap()) {
617		logmsg(LOG_ERR, "Exiting, init failure");
618		exit(1);
619	}
620
621	/* Privilege separation begins here */
622	if (priv_init()) {
623		logmsg(LOG_ERR, "unable to privsep");
624		exit(1);
625	}
626
627	setproctitle("[initializing]");
628	/* Process is now unprivileged and inside a chroot */
629	signal(SIGTERM, sig_close);
630	signal(SIGINT, sig_close);
631	signal(SIGQUIT, sig_close);
632	signal(SIGALRM, sig_alrm);
633	signal(SIGHUP, sig_hup);
634	alarm(delay);
635
636	buffer = malloc(PFLOGD_BUFSIZE);
637
638	if (buffer == NULL) {
639		logmsg(LOG_WARNING, "Failed to allocate output buffer");
640		phandler = dump_packet_nobuf;
641	} else {
642		bufleft = buflen = PFLOGD_BUFSIZE;
643		bufpos = buffer;
644		bufpkt = 0;
645	}
646
647	if (reset_dump()) {
648		if (Xflag)
649			return (1);
650
651		logmsg(LOG_ERR, "Logging suspended: open error");
652		set_suspended(1);
653	} else if (Xflag)
654		return (0);
655
656	while (1) {
657		np = pcap_dispatch(hpcap, PCAP_NUM_PKTS,
658		    dump_packet, (u_char *)dpcap);
659		if (np < 0)
660			logmsg(LOG_NOTICE, "%s", pcap_geterr(hpcap));
661
662		if (gotsig_close)
663			break;
664		if (gotsig_hup) {
665			if (reset_dump()) {
666				logmsg(LOG_ERR,
667				    "Logging suspended: open error");
668				set_suspended(1);
669			}
670			gotsig_hup = 0;
671		}
672
673		if (gotsig_alrm) {
674			if (dpcap)
675				flush_buffer(dpcap);
676			gotsig_alrm = 0;
677			alarm(delay);
678		}
679	}
680
681	logmsg(LOG_NOTICE, "Exiting");
682	if (dpcap) {
683		flush_buffer(dpcap);
684		fclose(dpcap);
685	}
686	purge_buffer();
687
688	if (pcap_stats(hpcap, &pstat) < 0)
689		logmsg(LOG_WARNING, "Reading stats: %s", pcap_geterr(hpcap));
690	else
691		logmsg(LOG_NOTICE,
692		    "%u packets received, %u/%u dropped (kernel/pflogd)",
693		    pstat.ps_recv, pstat.ps_drop, packets_dropped);
694
695	pcap_close(hpcap);
696	if (!Debug)
697		closelog();
698	return (0);
699}
700