Date: 8 Sep 1995 04:21:28 +0800 From: peter@haywire.dialix.com (Peter Wemm) To: freebsd-security@freebsd.org Subject: Are we doing this syslog() thing the wrong way? Message-ID: <42nk88$ad0$1@haywire.DIALix.COM>
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Are we not all looking at it from the wrong way?
It seems that an incredible effort is being spent to make the message
fit in a small, fixed size buffer. I have a half-baked idea for an
alternative, that might just be better and more efficient..
It might be even easier still.. How's this for a skeleton for starters:
vsyslog(...)
{
...
FILE fake;
fake._flags = _SWR | _SSTR; /* from libc/stdio/vsnprintf.c */
fake._bf._base = fake._p = (unsigned char *)tbuf;
fake._bf._size = fake._w = sizeof(tbuf);
... then do *all* the printfs via fprintf()..
fprintf(&fake, "<%d>", pri);
fprintf(&fake, "%.15s ", ctime(now) + 4);
..
if (LogTag)
fprintf(&fake, "%s", LogTag);
if (LogStat & LOG_PID)
fprintf(&fake, "[%d]", getpid());
if (LogTag)
fprintf(&fake, ": ");
for (....) {
....
fprintf(&fake, "%s", strerror(saved_errno);
....
}
vfprintf(&fake, fmt_cpy, ap);
/* at this point, we're done. fake._w has (I think) the space left */
#if hmm... I dont think this is needed,
tbuf[sizeof(tbuf) - 1] = '\0';
cnt = strlen(tbuf);
#else
cnt = sizeof(tbuf) - fake._w; /* have not checked yet... */
#endif
.. writev()...
send(LogFile, tbuf, cnt, 0)
...
... write() to console...
}
stdio is meant to be our friend. It can help us here...
Comments? Is this a better way?
It'd be nice if stdio exported a non-advertised routine to set things
like this up. I'm sure they could be used elsewhere in the system if
it wasn't for the "detailed knowledge" of the stdio internals.
Anyway, here's a *minimally* touched version of our current syslog,
which appears to work with a couple of simple tests with logger. I
have not analysed to see if there are any off-by-one errors - it may
be possible that it writes one character too many into tbuf. I'm sure
there are minor things that need cleaning, but the basics are there.
I think this ties it up pretty well... I guess the collective gaze of
a group of security-suspicious people will find it's holes pretty
quick.. :-) Please, be gentle.. :-)
-Peter
/*
* Copyright (c) 1983, 1988, 1993
* The Regents of the University of California. All rights reserved.
* Copyright (c) 1995 Peter Wemm (so there.. :-)
*
* 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 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 <sys/types.h>
#include <sys/socket.h>
#include <sys/syslog.h>
#include <sys/uio.h>
#include <netdb.h>
#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#if __STDC__
#include <stdarg.h>
#else
#include <varargs.h>
#endif
static int LogFile = -1; /* fd for log */
static int connected; /* have done connect */
static int LogStat = 0; /* status bits, set by openlog() */
static const char *LogTag = NULL; /* 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. */
/*
* syslog, vsyslog --
* print message on log file; output is intended for syslogd(8).
*/
void
#if __STDC__
syslog(int pri, const char *fmt, ...)
#else
syslog(pri, fmt, va_alist)
int pri;
char *fmt;
va_dcl
#endif
{
va_list ap;
#if __STDC__
va_start(ap, fmt);
#else
va_start(ap);
#endif
vsyslog(pri, fmt, ap);
va_end(ap);
}
void
vsyslog(pri, fmt, ap)
int pri;
register const char *fmt;
va_list ap;
{
register int cnt;
register char ch, *p, *t;
time_t now;
int fd, saved_errno;
char *stdp, tbuf[2048], fmt_cpy[1024];
FILE f;
/*
* Initialise the stdio buffer to do multiple writes to a
* string buffer
*/
f._flags = __SWR | __SSTR; /* __SSTR means string buffer mode */
f._bf._base = f._p = (unsigned char *) tbuf;
f._bf._size = f._w = sizeof(tbuf);
#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;
}
/* Check priority against setlogmask values. */
if (!(LOG_MASK(LOG_PRI(pri)) & LogMask))
return;
saved_errno = errno;
/* Set default facility if none specified. */
if ((pri & LOG_FACMASK) == 0)
pri |= LogFacility;
/* Build the message. */
(void)time(&now);
(void)fprintf(&f, "<%d>", pri);
(void)fprintf(&f, "%.15s ", ctime(&now) + 4);
if (LogStat & LOG_PERROR)
stdp = tbuf + (sizeof(tbuf) - f._w);
if (LogTag == NULL)
LogTag = __progname;
if (LogTag != NULL)
(void)fprintf(&f, "%s", LogTag);
if (LogStat & LOG_PID)
(void)fprintf(&f, "[%d]", getpid());
if (LogTag != NULL) {
(void)fprintf(&f, ": ");
}
/* Substitute error message for %m. */
for (t = fmt_cpy; ch = *fmt; ++fmt)
if (ch == '%' && fmt[1] == 'm') {
++fmt;
t += sprintf(t, "%s", strerror(saved_errno));
} else
*t++ = ch;
*t = '\0';
vfprintf(&f, fmt_cpy, ap);
cnt = sizeof(tbuf) - f._w;
/* Output to stderr if requested. */
if (LogStat & LOG_PERROR) {
struct iovec iov[2];
register struct iovec *v = iov;
v->iov_base = stdp;
v->iov_len = cnt - (stdp - tbuf);
++v;
v->iov_base = "\n";
v->iov_len = 1;
(void)writev(STDERR_FILENO, iov, 2);
}
/* Get connected, output the message to the local logger. */
if (!connected)
openlog(LogTag, LogStat | LOG_NDELAY, 0);
if (send(LogFile, tbuf, cnt, 0) >= 0)
return;
/*
* 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.
*/
if (LogStat & LOG_CONS &&
(fd = open(_PATH_CONSOLE, O_WRONLY, 0)) >= 0) {
(void)strcat(tbuf, "\r\n");
cnt += 2;
p = index(tbuf, '>') + 1;
(void)write(fd, p, cnt - (p - tbuf));
(void)close(fd);
}
}
static struct sockaddr SyslogAddr; /* AF_UNIX address of local logger */
void
openlog(ident, logstat, logfac)
const char *ident;
int logstat, logfac;
{
if (ident != NULL)
LogTag = ident;
LogStat = logstat;
if (logfac != 0 && (logfac &~ LOG_FACMASK) == 0)
LogFacility = logfac;
if (LogFile == -1) {
SyslogAddr.sa_family = AF_UNIX;
(void)strncpy(SyslogAddr.sa_data, _PATH_LOG,
sizeof(SyslogAddr.sa_data));
if (LogStat & LOG_NDELAY) {
if ((LogFile = socket(AF_UNIX, SOCK_DGRAM, 0)) == -1)
return;
(void)fcntl(LogFile, F_SETFD, 1);
}
}
if (LogFile != -1 && !connected)
if (connect(LogFile, &SyslogAddr, sizeof(SyslogAddr)) == -1) {
(void)close(LogFile);
LogFile = -1;
} else
connected = 1;
}
void
closelog()
{
(void)close(LogFile);
LogFile = -1;
connected = 0;
}
/* setlogmask -- set the log mask level */
int
setlogmask(pmask)
int pmask;
{
int omask;
omask = LogMask;
if (pmask != 0)
LogMask = pmask;
return (omask);
}
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