1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1983, 1988, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 #include <sys/cdefs.h>
33 __SCCSID("@(#)syslog.c 8.5 (Berkeley) 4/29/95");
34 #include "namespace.h"
35 #include <sys/param.h>
36 #include <sys/socket.h>
37 #include <sys/syslog.h>
38 #include <sys/time.h>
39 #include <sys/uio.h>
40 #include <sys/un.h>
41 #include <netdb.h>
42
43 #include <errno.h>
44 #include <fcntl.h>
45 #include <paths.h>
46 #include <pthread.h>
47 #include <stdio.h>
48 #include <stdlib.h>
49 #include <string.h>
50 #include <time.h>
51 #include <unistd.h>
52
53 #include <stdarg.h>
54 #include "un-namespace.h"
55
56 #include "libc_private.h"
57
58 /* Maximum number of characters of syslog message */
59 #define MAXLINE 8192
60
61 static int LogFile = -1; /* fd for log */
62 static int status; /* connection status */
63 static int opened; /* have done openlog() */
64 static int LogStat = 0; /* status bits, set by openlog() */
65 static pid_t LogPid = -1; /* process id to tag the entry with */
66 static const char *LogTag = NULL; /* string to tag the entry with */
67 static int LogTagLength = -1; /* usable part of LogTag */
68 static int LogFacility = LOG_USER; /* default facility code */
69 static int LogMask = 0xff; /* mask of priorities to be logged */
70 static pthread_mutex_t syslog_mutex = PTHREAD_MUTEX_INITIALIZER;
71
72 #define THREAD_LOCK() \
73 do { \
74 if (__isthreaded) _pthread_mutex_lock(&syslog_mutex); \
75 } while(0)
76 #define THREAD_UNLOCK() \
77 do { \
78 if (__isthreaded) _pthread_mutex_unlock(&syslog_mutex); \
79 } while(0)
80
81 /* RFC5424 defined value. */
82 #define NILVALUE "-"
83
84 static void disconnectlog(void); /* disconnect from syslogd */
85 static void connectlog(void); /* (re)connect to syslogd */
86 static void openlog_unlocked(const char *, int, int);
87 static void parse_tag(void); /* parse ident[NNN] if needed */
88
89 enum {
90 NOCONN = 0,
91 CONNDEF,
92 CONNPRIV,
93 };
94
95 /*
96 * Format of the magic cookie passed through the stdio hook
97 */
98 struct bufcookie {
99 char *base; /* start of buffer */
100 int left;
101 };
102
103 /*
104 * stdio write hook for writing to a static string buffer
105 * XXX: Maybe one day, dynamically allocate it so that the line length
106 * is `unlimited'.
107 */
108 static int
writehook(void * cookie,const char * buf,int len)109 writehook(void *cookie, const char *buf, int len)
110 {
111 struct bufcookie *h; /* private `handle' */
112
113 h = (struct bufcookie *)cookie;
114 if (len > h->left) {
115 /* clip in case of wraparound */
116 len = h->left;
117 }
118 if (len > 0) {
119 (void)memcpy(h->base, buf, len); /* `write' it. */
120 h->base += len;
121 h->left -= len;
122 }
123 return len;
124 }
125
126 /*
127 * syslog, vsyslog --
128 * print message on log file; output is intended for syslogd(8).
129 */
130 void
syslog(int pri,const char * fmt,...)131 syslog(int pri, const char *fmt, ...)
132 {
133 va_list ap;
134
135 va_start(ap, fmt);
136 vsyslog(pri, fmt, ap);
137 va_end(ap);
138 }
139
140 static void
vsyslog1(int pri,const char * fmt,va_list ap)141 vsyslog1(int pri, const char *fmt, va_list ap)
142 {
143 struct timeval now;
144 struct tm tm;
145 char ch, *p;
146 long tz_offset;
147 int cnt, fd, saved_errno;
148 char hostname[MAXHOSTNAMELEN], *stdp, tbuf[MAXLINE], fmt_cpy[MAXLINE],
149 errstr[64], tz_sign;
150 FILE *fp, *fmt_fp;
151 struct bufcookie tbuf_cookie;
152 struct bufcookie fmt_cookie;
153
154 #define INTERNALLOG LOG_ERR|LOG_CONS|LOG_PERROR|LOG_PID
155 /* Check for invalid bits. */
156 if (pri & ~(LOG_PRIMASK|LOG_FACMASK)) {
157 syslog(INTERNALLOG,
158 "syslog: unknown facility/priority: %x", pri);
159 pri &= LOG_PRIMASK|LOG_FACMASK;
160 }
161
162 saved_errno = errno;
163
164 /* Check priority against setlogmask values. */
165 if (!(LOG_MASK(LOG_PRI(pri)) & LogMask))
166 return;
167
168 /* Set default facility if none specified. */
169 if ((pri & LOG_FACMASK) == 0)
170 pri |= LogFacility;
171
172 /* Create the primary stdio hook */
173 tbuf_cookie.base = tbuf;
174 tbuf_cookie.left = sizeof(tbuf);
175 fp = fwopen(&tbuf_cookie, writehook);
176 if (fp == NULL)
177 return;
178
179 /* Build the message according to RFC 5424. Tag and version. */
180 (void)fprintf(fp, "<%d>1 ", pri);
181 /* Timestamp similar to RFC 3339. */
182 if (gettimeofday(&now, NULL) == 0 &&
183 localtime_r(&now.tv_sec, &tm) != NULL) {
184 if (tm.tm_gmtoff < 0) {
185 tz_sign = '-';
186 tz_offset = -tm.tm_gmtoff;
187 } else {
188 tz_sign = '+';
189 tz_offset = tm.tm_gmtoff;
190 }
191
192 (void)fprintf(fp,
193 "%04d-%02d-%02d" /* Date. */
194 "T%02d:%02d:%02d.%06ld" /* Time. */
195 "%c%02ld:%02ld ", /* Time zone offset. */
196 tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
197 tm.tm_hour, tm.tm_min, tm.tm_sec, now.tv_usec,
198 tz_sign, tz_offset / 3600, (tz_offset % 3600) / 60);
199 } else
200 (void)fputs(NILVALUE " ", fp);
201 /* Hostname. */
202 (void)gethostname(hostname, sizeof(hostname));
203 (void)fprintf(fp, "%s ",
204 hostname[0] == '\0' ? NILVALUE : hostname);
205 if (LogStat & LOG_PERROR) {
206 /* Transfer to string buffer */
207 (void)fflush(fp);
208 stdp = tbuf + (sizeof(tbuf) - tbuf_cookie.left);
209 }
210 /* Application name. */
211 if (LogTag == NULL)
212 LogTag = _getprogname();
213 else if (LogTagLength == -1)
214 parse_tag();
215 if (LogTagLength > 0)
216 (void)fprintf(fp, "%.*s ", LogTagLength, LogTag);
217 else
218 (void)fprintf(fp, "%s ", LogTag == NULL ? NILVALUE : LogTag);
219 /*
220 * Provide the process ID regardless of whether LOG_PID has been
221 * specified, as it provides valuable information. Many
222 * applications tend not to use this, even though they should.
223 */
224 if (LogTagLength <= 0)
225 LogPid = getpid();
226 (void)fprintf(fp, "%d ", (int)LogPid);
227 /* Message ID. */
228 (void)fputs(NILVALUE " ", fp);
229 /* Structured data. */
230 (void)fputs(NILVALUE " ", fp);
231
232 /* Check to see if we can skip expanding the %m */
233 if (strstr(fmt, "%m")) {
234
235 /* Create the second stdio hook */
236 fmt_cookie.base = fmt_cpy;
237 fmt_cookie.left = sizeof(fmt_cpy) - 1;
238 fmt_fp = fwopen(&fmt_cookie, writehook);
239 if (fmt_fp == NULL) {
240 fclose(fp);
241 return;
242 }
243
244 /*
245 * Substitute error message for %m. Be careful not to
246 * molest an escaped percent "%%m". We want to pass it
247 * on untouched as the format is later parsed by vfprintf.
248 */
249 for ( ; (ch = *fmt); ++fmt) {
250 if (ch == '%' && fmt[1] == 'm') {
251 ++fmt;
252 strerror_r(saved_errno, errstr, sizeof(errstr));
253 fputs(errstr, fmt_fp);
254 } else if (ch == '%' && fmt[1] == '%') {
255 ++fmt;
256 fputc(ch, fmt_fp);
257 fputc(ch, fmt_fp);
258 } else {
259 fputc(ch, fmt_fp);
260 }
261 }
262
263 /* Null terminate if room */
264 fputc(0, fmt_fp);
265 fclose(fmt_fp);
266
267 /* Guarantee null termination */
268 fmt_cpy[sizeof(fmt_cpy) - 1] = '\0';
269
270 fmt = fmt_cpy;
271 }
272
273 /* Message. */
274 (void)vfprintf(fp, fmt, ap);
275 (void)fclose(fp);
276
277 cnt = sizeof(tbuf) - tbuf_cookie.left;
278
279 /* Remove a trailing newline */
280 if (tbuf[cnt - 1] == '\n')
281 cnt--;
282
283 /* Output to stderr if requested. */
284 if (LogStat & LOG_PERROR) {
285 struct iovec iov[2];
286 struct iovec *v = iov;
287
288 v->iov_base = stdp;
289 v->iov_len = cnt - (stdp - tbuf);
290 ++v;
291 v->iov_base = "\n";
292 v->iov_len = 1;
293 (void)_writev(STDERR_FILENO, iov, 2);
294 }
295
296 /* Get connected, output the message to the local logger. */
297 if (!opened)
298 openlog_unlocked(LogTag, LogStat | LOG_NDELAY, 0);
299 connectlog();
300
301 /*
302 * If the send() fails, there are two likely scenarios:
303 * 1) syslogd was restarted
304 * 2) /var/run/log is out of socket buffer space, which
305 * in most cases means local DoS.
306 * If the error does not indicate a full buffer, we address
307 * case #1 by attempting to reconnect to /var/run/log[priv]
308 * and resending the message once.
309 *
310 * If we are working with a privileged socket, the retry
311 * attempts end there, because we don't want to freeze a
312 * critical application like su(1) or sshd(8).
313 *
314 * Otherwise, we address case #2 by repeatedly retrying the
315 * send() to give syslogd a chance to empty its socket buffer.
316 */
317
318 if (send(LogFile, tbuf, cnt, 0) < 0) {
319 if (errno != ENOBUFS) {
320 /*
321 * Scenario 1: syslogd was restarted
322 * reconnect and resend once
323 */
324 disconnectlog();
325 connectlog();
326 if (send(LogFile, tbuf, cnt, 0) >= 0)
327 return;
328 /*
329 * if the resend failed, fall through to
330 * possible scenario 2
331 */
332 }
333 while (errno == ENOBUFS) {
334 /*
335 * Scenario 2: out of socket buffer space
336 * possible DoS, fail fast on a privileged
337 * socket
338 */
339 if (status == CONNPRIV)
340 break;
341 _usleep(1);
342 if (send(LogFile, tbuf, cnt, 0) >= 0)
343 return;
344 }
345 } else
346 return;
347
348 /*
349 * Output the message to the console; try not to block
350 * as a blocking console should not stop other processes.
351 * Make sure the error reported is the one from the syslogd failure.
352 */
353 if (LogStat & LOG_CONS &&
354 (fd = _open(_PATH_CONSOLE, O_WRONLY|O_NONBLOCK|O_CLOEXEC, 0)) >=
355 0) {
356 struct iovec iov[2];
357 struct iovec *v = iov;
358
359 p = strchr(tbuf, '>') + 3;
360 v->iov_base = p;
361 v->iov_len = cnt - (p - tbuf);
362 ++v;
363 v->iov_base = "\r\n";
364 v->iov_len = 2;
365 (void)_writev(fd, iov, 2);
366 (void)_close(fd);
367 }
368 }
369
370 static void
syslog_cancel_cleanup(void * arg __unused)371 syslog_cancel_cleanup(void *arg __unused)
372 {
373
374 THREAD_UNLOCK();
375 }
376
377 void
vsyslog(int pri,const char * fmt,va_list ap)378 vsyslog(int pri, const char *fmt, va_list ap)
379 {
380
381 THREAD_LOCK();
382 pthread_cleanup_push(syslog_cancel_cleanup, NULL);
383 vsyslog1(pri, fmt, ap);
384 pthread_cleanup_pop(1);
385 }
386
387 /* Should be called with mutex acquired */
388 static void
disconnectlog(void)389 disconnectlog(void)
390 {
391 /*
392 * If the user closed the FD and opened another in the same slot,
393 * that's their problem. They should close it before calling on
394 * system services.
395 */
396 if (LogFile != -1) {
397 _close(LogFile);
398 LogFile = -1;
399 }
400 status = NOCONN; /* retry connect */
401 }
402
403 /* Should be called with mutex acquired */
404 static void
connectlog(void)405 connectlog(void)
406 {
407 struct sockaddr_un SyslogAddr; /* AF_UNIX address of local logger */
408
409 if (LogFile == -1) {
410 socklen_t len;
411
412 if ((LogFile = _socket(AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC,
413 0)) == -1)
414 return;
415 if (_getsockopt(LogFile, SOL_SOCKET, SO_SNDBUF, &len,
416 &(socklen_t){sizeof(len)}) == 0) {
417 if (len < MAXLINE) {
418 len = MAXLINE;
419 (void)_setsockopt(LogFile, SOL_SOCKET, SO_SNDBUF,
420 &len, sizeof(len));
421 }
422 }
423 }
424 if (LogFile != -1 && status == NOCONN) {
425 SyslogAddr.sun_len = sizeof(SyslogAddr);
426 SyslogAddr.sun_family = AF_UNIX;
427
428 /*
429 * First try privileged socket. If no success,
430 * then try default socket.
431 */
432 (void)strncpy(SyslogAddr.sun_path, _PATH_LOG_PRIV,
433 sizeof SyslogAddr.sun_path);
434 if (_connect(LogFile, (struct sockaddr *)&SyslogAddr,
435 sizeof(SyslogAddr)) != -1)
436 status = CONNPRIV;
437
438 if (status == NOCONN) {
439 (void)strncpy(SyslogAddr.sun_path, _PATH_LOG,
440 sizeof SyslogAddr.sun_path);
441 if (_connect(LogFile, (struct sockaddr *)&SyslogAddr,
442 sizeof(SyslogAddr)) != -1)
443 status = CONNDEF;
444 }
445
446 if (status == NOCONN) {
447 /*
448 * Try the old "/dev/log" path, for backward
449 * compatibility.
450 */
451 (void)strncpy(SyslogAddr.sun_path, _PATH_OLDLOG,
452 sizeof SyslogAddr.sun_path);
453 if (_connect(LogFile, (struct sockaddr *)&SyslogAddr,
454 sizeof(SyslogAddr)) != -1)
455 status = CONNDEF;
456 }
457
458 if (status == NOCONN) {
459 (void)_close(LogFile);
460 LogFile = -1;
461 }
462 }
463 }
464
465 static void
openlog_unlocked(const char * ident,int logstat,int logfac)466 openlog_unlocked(const char *ident, int logstat, int logfac)
467 {
468 if (ident != NULL) {
469 LogTag = ident;
470 LogTagLength = -1;
471 }
472 LogStat = logstat;
473 parse_tag();
474 if (logfac != 0 && (logfac &~ LOG_FACMASK) == 0)
475 LogFacility = logfac;
476
477 if (LogStat & LOG_NDELAY) /* open immediately */
478 connectlog();
479
480 opened = 1; /* ident and facility has been set */
481 }
482
483 void
openlog(const char * ident,int logstat,int logfac)484 openlog(const char *ident, int logstat, int logfac)
485 {
486
487 THREAD_LOCK();
488 pthread_cleanup_push(syslog_cancel_cleanup, NULL);
489 openlog_unlocked(ident, logstat, logfac);
490 pthread_cleanup_pop(1);
491 }
492
493
494 void
closelog(void)495 closelog(void)
496 {
497 THREAD_LOCK();
498 if (LogFile != -1) {
499 (void)_close(LogFile);
500 LogFile = -1;
501 }
502 LogTag = NULL;
503 LogTagLength = -1;
504 status = NOCONN;
505 THREAD_UNLOCK();
506 }
507
508 /* setlogmask -- set the log mask level */
509 int
setlogmask(int pmask)510 setlogmask(int pmask)
511 {
512 int omask;
513
514 THREAD_LOCK();
515 omask = LogMask;
516 if (pmask != 0)
517 LogMask = pmask;
518 THREAD_UNLOCK();
519 return (omask);
520 }
521
522 /*
523 * Obtain LogPid from LogTag formatted as following: ident[NNN]
524 */
525 static void
parse_tag(void)526 parse_tag(void)
527 {
528 char *begin, *end, *p;
529 pid_t pid;
530
531 if (LogTag == NULL || (LogStat & LOG_PID) != 0)
532 return;
533 /*
534 * LogTagLength is -1 if LogTag was not parsed yet.
535 * Avoid multiple passes over same LogTag.
536 */
537 LogTagLength = 0;
538
539 /* Check for presence of opening [ and non-empty ident. */
540 if ((begin = strchr(LogTag, '[')) == NULL || begin == LogTag)
541 return;
542 /* Check for presence of closing ] at the very end and non-empty pid. */
543 if ((end = strchr(begin + 1, ']')) == NULL || end[1] != 0 ||
544 (end - begin) < 2)
545 return;
546
547 /* Check for pid to contain digits only. */
548 pid = (pid_t)strtol(begin + 1, &p, 10);
549 if (p != end)
550 return;
551
552 LogPid = pid;
553 LogTagLength = begin - LogTag;
554 }
555