glibc/misc/syslog.c

/*
 * Copyright (c) 1983, 1988, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)syslog.c	8.4 (Berkeley) 3/18/94";
#endif /* LIBC_SCCS and not lint */

#include <libio/libioP.h>
#include <paths.h>
#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <sys/un.h>
#include <syslog.h>

static int LogType = SOCK_DGRAM;	/* type of socket connection */
static int LogFile = -1;		/* fd for log */
static bool connected;			/* have done connect */
static int LogStat;			/* status bits, set by openlog() */
static const char *LogTag;		/* string to tag the entry with */
static int LogFacility = LOG_USER;	/* default facility code */
static int LogMask = 0xff;		/* mask of priorities to be logged */
extern char *__progname;		/* Program name, from crt0. */

/* Define the lock.  */
__libc_lock_define_initialized (static, syslog_lock)
static void openlog_internal (const char *, int, int);
static void closelog_internal (void);

struct cleanup_arg
{
  void *buf;
  struct sigaction *oldaction;
};

static void
cancel_handler (void *ptr)
{
  /* Restore the old signal handler.  */
  struct cleanup_arg *clarg = (struct cleanup_arg *) ptr;

  if (clarg != NULL)
    /* Free the memstream buffer,  */
    free (clarg->buf);

  /* Free the lock.  */
  __libc_lock_unlock (syslog_lock);
}


/*
 * syslog, vsyslog --
 *	print message on log file; output is intended for syslogd(8).
 */
void
__syslog (int pri, const char *fmt, ...)
{
  va_list ap;

  va_start (ap, fmt);
  __vsyslog_internal (pri, fmt, ap, 0);
  va_end (ap);
}
ldbl_hidden_def (__syslog, syslog)
ldbl_strong_alias (__syslog, syslog)

void
__vsyslog (int pri, const char *fmt, va_list ap)
{
  __vsyslog_internal (pri, fmt, ap, 0);
}
ldbl_weak_alias (__vsyslog, vsyslog)

void
__syslog_chk (int pri, int flag, const char *fmt, ...)
{
  va_list ap;

  va_start (ap, fmt);
  __vsyslog_internal (pri, fmt, ap, (flag > 0) ? PRINTF_FORTIFY : 0);
  va_end (ap);
}

void
__vsyslog_chk (int pri, int flag, const char *fmt, va_list ap)
{
  __vsyslog_internal (pri, fmt, ap, (flag > 0) ? PRINTF_FORTIFY : 0);
}

void
__vsyslog_internal (int pri, const char *fmt, va_list ap,
		    unsigned int mode_flags)
{
  FILE *f;
  char *buf = 0;
  size_t bufsize = 0;
  int msgoff;
  int saved_errno = errno;
  char failbuf[3 * sizeof (pid_t) + sizeof "out of memory []"];

#define	INTERNALLOG LOG_ERR|LOG_CONS|LOG_PERROR|LOG_PID
  /* Check for invalid bits. */
  if (pri & ~(LOG_PRIMASK | LOG_FACMASK))
    {
      syslog (INTERNALLOG, "syslog: unknown facility/priority: %x", pri);
      pri &= LOG_PRIMASK | LOG_FACMASK;
    }

  /* Prepare for multiple users.  We have to take care: most syscalls we are
     using are cancellation points.  */
  struct cleanup_arg clarg = { NULL, NULL };
  __libc_cleanup_push (cancel_handler, &clarg);
  __libc_lock_lock (syslog_lock);

  /* Check priority against setlogmask values. */
  if ((LOG_MASK (LOG_PRI (pri)) & LogMask) == 0)
    goto out;

  /* Set default facility if none specified. */
  if ((pri & LOG_FACMASK) == 0)
    pri |= LogFacility;

  /* Build the message in a memory-buffer stream.  */
  f = __open_memstream (&buf, &bufsize);
  if (f != NULL)
    {
      __fsetlocking (f, FSETLOCKING_BYCALLER);
      /* "%b %e %H:%M:%S"  */
      char timebuf[sizeof "MMM DD hh:mm:ss "];
      time_t now = time_now ();
      struct tm now_tm;
      __localtime_r (&now, &now_tm);
      __strftime_l (timebuf, sizeof (timebuf), "%b %e %T", &now_tm,
		    _nl_C_locobj_ptr);

      pid_t pid = LogStat & LOG_PID ? __getpid () : 0;

      fprintf (f, "<%d>%s %n%s%s%.0d%s: ", pri, timebuf, &msgoff,
               LogTag == NULL ? __progname : LogTag,
               pid != 0 ? "[" : "", pid, pid != 0 ? "]" : "");
      /* Restore errno for %m format.  */
      __set_errno (saved_errno);

      /* We have the header.  Print the user's format into the buffer.  */
      __vfprintf_internal (f, fmt, ap, mode_flags);

      /* Close the memory stream; this will finalize the data into a malloc'd
         buffer in BUF.  */
      fclose (f);

      /* Tell the cancellation handler to free this buffer.  */
      clarg.buf = buf;
    }
  else
    {
      /* Nothing much to do but emit an error message.  */
      bufsize = __snprintf (failbuf, sizeof failbuf, "out of memory[%d]",
                            __getpid ());
      buf = failbuf;
    }

  /* Output to stderr if requested. */
  if (LogStat & LOG_PERROR)
    __dprintf (STDERR_FILENO, "%s%s", buf + msgoff,
	       "\n" + (buf[bufsize - 1] == '\n'));

  /* Get connected, output the message to the local logger.  */
  if (!connected)
    openlog_internal (NULL, LogStat | LOG_NDELAY, LogFacility);

  /* If we have a SOCK_STREAM connection, also send ASCII NUL as a record
     terminator.  */
  if (LogType == SOCK_STREAM)
    ++bufsize;

  if (!connected || __send (LogFile, buf, bufsize, MSG_NOSIGNAL) < 0)
    {
      if (connected)
	{
	  /* Try to reopen the syslog connection.  Maybe it went down.  */
	  closelog_internal ();
	  openlog_internal (NULL, LogStat | LOG_NDELAY, LogFacility);
	}

      if (!connected || __send (LogFile, buf, bufsize, MSG_NOSIGNAL) < 0)
	{
	  closelog_internal ();	/* attempt re-open next time */
	  /*
	   * Output the message to the console; don't worry
	   * about blocking, if console blocks everything will.
	   * Make sure the error reported is the one from the
	   * syslogd failure.
	   */
	  int fd;
	  if (LogStat & LOG_CONS &&
	      (fd = __open (_PATH_CONSOLE, O_WRONLY | O_NOCTTY
			    | O_CLOEXEC, 0)) >= 0)
	    {
	      __dprintf (fd, "%s\r\n", buf + msgoff);
	      __close (fd);
	    }
	}
    }

out:
  /* End of critical section.  */
  __libc_cleanup_pop (0);
  __libc_lock_unlock (syslog_lock);

  if (buf != failbuf)
    free (buf);
}

/* AF_UNIX address of local logger  */
static const struct sockaddr_un SyslogAddr =
  {
    .sun_family = AF_UNIX,
    .sun_path = _PATH_LOG
  };

static void
openlog_internal (const char *ident, int logstat, int logfac)
{
  if (ident != NULL)
    LogTag = ident;
  LogStat = logstat;
  if ((logfac & ~LOG_FACMASK) == 0)
    LogFacility = logfac;

  int retry = 0;
  while (retry < 2)
    {
      if (LogFile == -1)
	{
	  if (LogStat & LOG_NDELAY)
	    {
	      LogFile = __socket (AF_UNIX, LogType | SOCK_CLOEXEC, 0);
	      if (LogFile == -1)
		return;
	    }
	}
      if (LogFile != -1 && !connected)
	{
	  int old_errno = errno;
	  if (__connect (LogFile, &SyslogAddr, sizeof (SyslogAddr)) == -1)
	    {
	      int saved_errno = errno;
	      int fd = LogFile;
	      LogFile = -1;
	      __close (fd);
	      __set_errno (old_errno);
	      if (saved_errno == EPROTOTYPE)
		{
		  /* retry with the other type: */
		  LogType = LogType == SOCK_DGRAM ? SOCK_STREAM : SOCK_DGRAM;
		  ++retry;
		  continue;
		}
	    }
	  else
	    connected = true;
	}
      break;
    }
}

void
openlog (const char *ident, int logstat, int logfac)
{
  /* Protect against multiple users and cancellation.  */
  __libc_cleanup_push (cancel_handler, NULL);
  __libc_lock_lock (syslog_lock);

  openlog_internal (ident, logstat, logfac);

  __libc_cleanup_pop (1);
}

static void
closelog_internal (void)
{
  if (!connected)
    return;

  __close (LogFile);
  LogFile = -1;
  connected = false;
}

void
closelog (void)
{
  /* Protect against multiple users and cancellation.  */
  __libc_cleanup_push (cancel_handler, NULL);
  __libc_lock_lock (syslog_lock);

  closelog_internal ();
  LogTag = NULL;
  LogType = SOCK_DGRAM; /* this is the default */

  /* Free the lock.  */
  __libc_cleanup_pop (1);
}

/* setlogmask -- set the log mask level */
int
setlogmask (int pmask)
{
  int omask;

  /* Protect against multiple users.  */
  __libc_lock_lock (syslog_lock);

  omask = LogMask;
  if (pmask != 0)
    LogMask = pmask;

  __libc_lock_unlock (syslog_lock);

  return (omask);
}