1/*
2 * Copyright (c) 1983, 1988, 1993
3 *	The Regents of the University of California.  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 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 4. Neither the name of the University nor the names of its contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30#if defined(LIBC_SCCS) && !defined(lint)
31static char sccsid[] = "@(#)syslog.c	8.5 (Berkeley) 4/29/95";
32#endif /* LIBC_SCCS and not lint */
33#include <sys/cdefs.h>
34__FBSDID("$FreeBSD: stable/10/lib/libc/gen/syslog.c 320312 2017-06-24 14:44:59Z kib $");
35
36#include "namespace.h"
37#include <sys/types.h>
38#include <sys/socket.h>
39#include <sys/syslog.h>
40#include <sys/uio.h>
41#include <sys/un.h>
42#include <netdb.h>
43
44#include <errno.h>
45#include <fcntl.h>
46#include <paths.h>
47#include <pthread.h>
48#include <stdio.h>
49#include <stdlib.h>
50#include <string.h>
51#include <time.h>
52#include <unistd.h>
53
54#include <stdarg.h>
55#include "un-namespace.h"
56
57#include "libc_private.h"
58
59static int	LogFile = -1;		/* fd for log */
60static int	status;			/* connection status */
61static int	opened;			/* have done openlog() */
62static int	LogStat = 0;		/* status bits, set by openlog() */
63static const char *LogTag = NULL;	/* string to tag the entry with */
64static int	LogFacility = LOG_USER;	/* default facility code */
65static int	LogMask = 0xff;		/* mask of priorities to be logged */
66static pthread_mutex_t	syslog_mutex = PTHREAD_MUTEX_INITIALIZER;
67
68#define	THREAD_LOCK()							\
69	do { 								\
70		if (__isthreaded) _pthread_mutex_lock(&syslog_mutex);	\
71	} while(0)
72#define	THREAD_UNLOCK()							\
73	do {								\
74		if (__isthreaded) _pthread_mutex_unlock(&syslog_mutex);	\
75	} while(0)
76
77static void	disconnectlog(void); /* disconnect from syslogd */
78static void	connectlog(void);	/* (re)connect to syslogd */
79static void	openlog_unlocked(const char *, int, int);
80
81enum {
82	NOCONN = 0,
83	CONNDEF,
84	CONNPRIV,
85};
86
87/*
88 * Format of the magic cookie passed through the stdio hook
89 */
90struct bufcookie {
91	char	*base;	/* start of buffer */
92	int	left;
93};
94
95/*
96 * stdio write hook for writing to a static string buffer
97 * XXX: Maybe one day, dynamically allocate it so that the line length
98 *      is `unlimited'.
99 */
100static int
101writehook(void *cookie, const char *buf, int len)
102{
103	struct bufcookie *h;	/* private `handle' */
104
105	h = (struct bufcookie *)cookie;
106	if (len > h->left) {
107		/* clip in case of wraparound */
108		len = h->left;
109	}
110	if (len > 0) {
111		(void)memcpy(h->base, buf, len); /* `write' it. */
112		h->base += len;
113		h->left -= len;
114	}
115	return len;
116}
117
118/*
119 * syslog, vsyslog --
120 *	print message on log file; output is intended for syslogd(8).
121 */
122void
123syslog(int pri, const char *fmt, ...)
124{
125	va_list ap;
126
127	va_start(ap, fmt);
128	vsyslog(pri, fmt, ap);
129	va_end(ap);
130}
131
132static void
133vsyslog1(int pri, const char *fmt, va_list ap)
134{
135	int cnt;
136	char ch, *p;
137	time_t now;
138	int fd, saved_errno;
139	char *stdp, tbuf[2048], fmt_cpy[1024], timbuf[26], errstr[64];
140	FILE *fp, *fmt_fp;
141	struct bufcookie tbuf_cookie;
142	struct bufcookie fmt_cookie;
143
144#define	INTERNALLOG	LOG_ERR|LOG_CONS|LOG_PERROR|LOG_PID
145	/* Check for invalid bits. */
146	if (pri & ~(LOG_PRIMASK|LOG_FACMASK)) {
147		syslog(INTERNALLOG,
148		    "syslog: unknown facility/priority: %x", pri);
149		pri &= LOG_PRIMASK|LOG_FACMASK;
150	}
151
152	saved_errno = errno;
153
154	/* Check priority against setlogmask values. */
155	if (!(LOG_MASK(LOG_PRI(pri)) & LogMask))
156		return;
157
158	/* Set default facility if none specified. */
159	if ((pri & LOG_FACMASK) == 0)
160		pri |= LogFacility;
161
162	/* Create the primary stdio hook */
163	tbuf_cookie.base = tbuf;
164	tbuf_cookie.left = sizeof(tbuf);
165	fp = fwopen(&tbuf_cookie, writehook);
166	if (fp == NULL)
167		return;
168
169	/* Build the message. */
170	(void)time(&now);
171	(void)fprintf(fp, "<%d>", pri);
172	(void)fprintf(fp, "%.15s ", ctime_r(&now, timbuf) + 4);
173	if (LogStat & LOG_PERROR) {
174		/* Transfer to string buffer */
175		(void)fflush(fp);
176		stdp = tbuf + (sizeof(tbuf) - tbuf_cookie.left);
177	}
178	if (LogTag == NULL)
179		LogTag = _getprogname();
180	if (LogTag != NULL)
181		(void)fprintf(fp, "%s", LogTag);
182	if (LogStat & LOG_PID)
183		(void)fprintf(fp, "[%d]", getpid());
184	if (LogTag != NULL) {
185		(void)fprintf(fp, ": ");
186	}
187
188	/* Check to see if we can skip expanding the %m */
189	if (strstr(fmt, "%m")) {
190
191		/* Create the second stdio hook */
192		fmt_cookie.base = fmt_cpy;
193		fmt_cookie.left = sizeof(fmt_cpy) - 1;
194		fmt_fp = fwopen(&fmt_cookie, writehook);
195		if (fmt_fp == NULL) {
196			fclose(fp);
197			return;
198		}
199
200		/*
201		 * Substitute error message for %m.  Be careful not to
202		 * molest an escaped percent "%%m".  We want to pass it
203		 * on untouched as the format is later parsed by vfprintf.
204		 */
205		for ( ; (ch = *fmt); ++fmt) {
206			if (ch == '%' && fmt[1] == 'm') {
207				++fmt;
208				strerror_r(saved_errno, errstr, sizeof(errstr));
209				fputs(errstr, fmt_fp);
210			} else if (ch == '%' && fmt[1] == '%') {
211				++fmt;
212				fputc(ch, fmt_fp);
213				fputc(ch, fmt_fp);
214			} else {
215				fputc(ch, fmt_fp);
216			}
217		}
218
219		/* Null terminate if room */
220		fputc(0, fmt_fp);
221		fclose(fmt_fp);
222
223		/* Guarantee null termination */
224		fmt_cpy[sizeof(fmt_cpy) - 1] = '\0';
225
226		fmt = fmt_cpy;
227	}
228
229	(void)vfprintf(fp, fmt, ap);
230	(void)fclose(fp);
231
232	cnt = sizeof(tbuf) - tbuf_cookie.left;
233
234	/* Remove a trailing newline */
235	if (tbuf[cnt - 1] == '\n')
236		cnt--;
237
238	/* Output to stderr if requested. */
239	if (LogStat & LOG_PERROR) {
240		struct iovec iov[2];
241		struct iovec *v = iov;
242
243		v->iov_base = stdp;
244		v->iov_len = cnt - (stdp - tbuf);
245		++v;
246		v->iov_base = "\n";
247		v->iov_len = 1;
248		(void)_writev(STDERR_FILENO, iov, 2);
249	}
250
251	/* Get connected, output the message to the local logger. */
252	if (!opened)
253		openlog_unlocked(LogTag, LogStat | LOG_NDELAY, 0);
254	connectlog();
255
256	/*
257	 * If the send() fails, there are two likely scenarios:
258	 *  1) syslogd was restarted
259	 *  2) /var/run/log is out of socket buffer space, which
260	 *     in most cases means local DoS.
261	 * If the error does not indicate a full buffer, we address
262	 * case #1 by attempting to reconnect to /var/run/log[priv]
263	 * and resending the message once.
264	 *
265	 * If we are working with a privileged socket, the retry
266	 * attempts end there, because we don't want to freeze a
267	 * critical application like su(1) or sshd(8).
268	 *
269	 * Otherwise, we address case #2 by repeatedly retrying the
270	 * send() to give syslogd a chance to empty its socket buffer.
271	 */
272
273	if (send(LogFile, tbuf, cnt, 0) < 0) {
274		if (errno != ENOBUFS) {
275			/*
276			 * Scenario 1: syslogd was restarted
277			 * reconnect and resend once
278			 */
279			disconnectlog();
280			connectlog();
281			if (send(LogFile, tbuf, cnt, 0) >= 0)
282				return;
283			/*
284			 * if the resend failed, fall through to
285			 * possible scenario 2
286			 */
287		}
288		while (errno == ENOBUFS) {
289			/*
290			 * Scenario 2: out of socket buffer space
291			 * possible DoS, fail fast on a privileged
292			 * socket
293			 */
294			if (status == CONNPRIV)
295				break;
296			_usleep(1);
297			if (send(LogFile, tbuf, cnt, 0) >= 0)
298				return;
299		}
300	} else
301		return;
302
303	/*
304	 * Output the message to the console; try not to block
305	 * as a blocking console should not stop other processes.
306	 * Make sure the error reported is the one from the syslogd failure.
307	 */
308	if (LogStat & LOG_CONS &&
309	    (fd = _open(_PATH_CONSOLE, O_WRONLY|O_NONBLOCK|O_CLOEXEC, 0)) >=
310	    0) {
311		struct iovec iov[2];
312		struct iovec *v = iov;
313
314		p = strchr(tbuf, '>') + 1;
315		v->iov_base = p;
316		v->iov_len = cnt - (p - tbuf);
317		++v;
318		v->iov_base = "\r\n";
319		v->iov_len = 2;
320		(void)_writev(fd, iov, 2);
321		(void)_close(fd);
322	}
323}
324
325static void
326syslog_cancel_cleanup(void *arg __unused)
327{
328
329	THREAD_UNLOCK();
330}
331
332void
333vsyslog(int pri, const char *fmt, va_list ap)
334{
335
336	THREAD_LOCK();
337	pthread_cleanup_push(syslog_cancel_cleanup, NULL);
338	vsyslog1(pri, fmt, ap);
339	pthread_cleanup_pop(1);
340}
341
342/* Should be called with mutex acquired */
343static void
344disconnectlog(void)
345{
346	/*
347	 * If the user closed the FD and opened another in the same slot,
348	 * that's their problem.  They should close it before calling on
349	 * system services.
350	 */
351	if (LogFile != -1) {
352		_close(LogFile);
353		LogFile = -1;
354	}
355	status = NOCONN;			/* retry connect */
356}
357
358/* Should be called with mutex acquired */
359static void
360connectlog(void)
361{
362	struct sockaddr_un SyslogAddr;	/* AF_UNIX address of local logger */
363
364	if (LogFile == -1) {
365		if ((LogFile = _socket(AF_UNIX, SOCK_DGRAM, 0)) == -1)
366			return;
367		(void)_fcntl(LogFile, F_SETFD, FD_CLOEXEC);
368	}
369	if (LogFile != -1 && status == NOCONN) {
370		SyslogAddr.sun_len = sizeof(SyslogAddr);
371		SyslogAddr.sun_family = AF_UNIX;
372
373		/*
374		 * First try privileged socket. If no success,
375		 * then try default socket.
376		 */
377		(void)strncpy(SyslogAddr.sun_path, _PATH_LOG_PRIV,
378		    sizeof SyslogAddr.sun_path);
379		if (_connect(LogFile, (struct sockaddr *)&SyslogAddr,
380		    sizeof(SyslogAddr)) != -1)
381			status = CONNPRIV;
382
383		if (status == NOCONN) {
384			(void)strncpy(SyslogAddr.sun_path, _PATH_LOG,
385			    sizeof SyslogAddr.sun_path);
386			if (_connect(LogFile, (struct sockaddr *)&SyslogAddr,
387			    sizeof(SyslogAddr)) != -1)
388				status = CONNDEF;
389		}
390
391		if (status == NOCONN) {
392			/*
393			 * Try the old "/dev/log" path, for backward
394			 * compatibility.
395			 */
396			(void)strncpy(SyslogAddr.sun_path, _PATH_OLDLOG,
397			    sizeof SyslogAddr.sun_path);
398			if (_connect(LogFile, (struct sockaddr *)&SyslogAddr,
399			    sizeof(SyslogAddr)) != -1)
400				status = CONNDEF;
401		}
402
403		if (status == NOCONN) {
404			(void)_close(LogFile);
405			LogFile = -1;
406		}
407	}
408}
409
410static void
411openlog_unlocked(const char *ident, int logstat, int logfac)
412{
413	if (ident != NULL)
414		LogTag = ident;
415	LogStat = logstat;
416	if (logfac != 0 && (logfac &~ LOG_FACMASK) == 0)
417		LogFacility = logfac;
418
419	if (LogStat & LOG_NDELAY)	/* open immediately */
420		connectlog();
421
422	opened = 1;	/* ident and facility has been set */
423}
424
425void
426openlog(const char *ident, int logstat, int logfac)
427{
428
429	THREAD_LOCK();
430	pthread_cleanup_push(syslog_cancel_cleanup, NULL);
431	openlog_unlocked(ident, logstat, logfac);
432	pthread_cleanup_pop(1);
433}
434
435
436void
437closelog(void)
438{
439	THREAD_LOCK();
440	if (LogFile != -1) {
441		(void)_close(LogFile);
442		LogFile = -1;
443	}
444	LogTag = NULL;
445	status = NOCONN;
446	THREAD_UNLOCK();
447}
448
449/* setlogmask -- set the log mask level */
450int
451setlogmask(int pmask)
452{
453	int omask;
454
455	THREAD_LOCK();
456	omask = LogMask;
457	if (pmask != 0)
458		LogMask = pmask;
459	THREAD_UNLOCK();
460	return (omask);
461}
462