Privilege separated syslog daemon. The child listening to log requests drops

to user _syslogd and chroots itself, while the privileged parent grants it
access to open logfiles and other calls it needs.

The only difference from existing behaviour is that if syslog.conf changes
and syslogd receives a HUP, it will re-exec itself and have two new PIDs.
A HUP with an unchanged config will make syslogd reopen logfiles as before.

Lots of help and code from deraadt@ , and advice from millert@

Various versions tested by todd, cloder, mpech, markus, tdeval and others

1 files changed, 175 insertions, 0 deletions

diff --git a/usr.sbin/syslogd/ttymsg.c b/usr.sbin/syslogd/ttymsg.c
new file mode 100644
index 00000000000..3ef189c07d0
--- /dev/null
+++ b/usr.sbin/syslogd/ttymsg.c
@@ -0,0 +1,175 @@
+/*	$OpenBSD: ttymsg.c,v 1.1 2003/07/31 18:20:07 avsm Exp $	*/
+/*	$NetBSD: ttymsg.c,v 1.3 1994/11/17 07:17:55 jtc Exp $	*/
+
+/*
+ * Copyright (c) 1989, 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.
+ * 3. 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.
+ */
+
+#ifndef lint
+#if 0
+static const char sccsid[] = "@(#)ttymsg.c	8.2 (Berkeley) 11/16/93";
+#endif
+static const char rcsid[] = "$OpenBSD: ttymsg.c,v 1.1 2003/07/31 18:20:07 avsm Exp $";
+#endif /* not lint */
+
+#include <sys/types.h>
+#include <sys/uio.h>
+#include <signal.h>
+#include <fcntl.h>
+#include <dirent.h>
+#include <errno.h>
+#include <paths.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+
+#include "syslogd.h"
+
+/*
+ * Display the contents of a uio structure on a terminal.
+ * Forks and finishes in child if write would block, waiting up to tmout
+ * seconds.  Returns pointer to error string on unexpected error;
+ * string is not newline-terminated.  Various "normal" errors are ignored
+ * (exclusive-use, lack of permission, etc.).
+ */
+char *
+ttymsg(struct iovec *iov, int iovcnt, char *line, int tmout)
+{
+	static char device[MAXNAMLEN] = _PATH_DEV;
+	static char errbuf[1024];
+	int cnt, fd, left, wret;
+	struct iovec localiov[6];
+	int forked = 0;
+	sigset_t mask;
+
+	if (iovcnt > sizeof(localiov) / sizeof(localiov[0]))
+		return ("too many iov's (change code in wall/ttymsg.c)");
+
+	/*
+	 * Ignore lines that start with "ftp" or "uucp".
+	 */
+	if ((strncmp(line, "ftp", 3) == 0) ||
+	    (strncmp(line, "uucp", 4) == 0))
+		return (NULL);
+
+	(void) strlcpy(device + sizeof(_PATH_DEV) - 1, line,
+	    sizeof(device) - (sizeof(_PATH_DEV) - 1));
+	if (strchr(device + sizeof(_PATH_DEV) - 1, '/')) {
+		/* A slash is an attempt to break security... */
+		(void) snprintf(errbuf, sizeof(errbuf), "'/' in \"%s\"",
+		    device);
+		return (errbuf);
+	}
+
+	/*
+	 * open will fail on slip lines or exclusive-use lines
+	 * if not running as root; not an error.
+	 */
+	if ((fd = priv_open_tty(device)) < 0) {
+		if (errno == EBUSY || errno == EACCES)
+			return (NULL);
+		(void) snprintf(errbuf, sizeof(errbuf),
+		    "%s: %s", device, strerror(errno));
+		return (errbuf);
+	}
+
+	for (cnt = left = 0; cnt < iovcnt; ++cnt)
+		left += iov[cnt].iov_len;
+
+	for (;;) {
+		wret = writev(fd, iov, iovcnt);
+		if (wret >= left)
+			break;
+		if (wret >= 0) {
+			left -= wret;
+			if (iov != localiov) {
+				bcopy(iov, localiov,
+				    iovcnt * sizeof(struct iovec));
+				iov = localiov;
+			}
+			for (cnt = 0; wret >= iov->iov_len; ++cnt) {
+				wret -= iov->iov_len;
+				++iov;
+				--iovcnt;
+			}
+			if (wret) {
+				iov->iov_base += wret;
+				iov->iov_len -= wret;
+			}
+			continue;
+		}
+		if (errno == EWOULDBLOCK) {
+			int off = 0;
+			pid_t cpid;
+
+			if (forked) {
+				(void) close(fd);
+				_exit(1);
+			}
+			cpid = fork();
+			if (cpid < 0) {
+				(void) snprintf(errbuf, sizeof(errbuf),
+				    "fork: %s", strerror(errno));
+				(void) close(fd);
+				return (errbuf);
+			}
+			if (cpid) {	/* parent */
+				(void) close(fd);
+				return (NULL);
+			}
+			forked++;
+			/* wait at most tmout seconds */
+			(void) signal(SIGALRM, SIG_DFL);
+			(void) signal(SIGTERM, SIG_DFL); /* XXX */
+			(void) sigemptyset(&mask);
+			(void) sigprocmask(SIG_SETMASK, &mask, NULL);
+			(void) alarm((u_int)tmout);
+			(void) fcntl(fd, O_NONBLOCK, &off);
+			continue;
+		}
+		/*
+		 * We get ENODEV on a slip line if we're running as root,
+		 * and EIO if the line just went away.
+		 */
+		if (errno == ENODEV || errno == EIO)
+			break;
+		(void) close(fd);
+		if (forked)
+			_exit(1);
+		(void) snprintf(errbuf, sizeof(errbuf),
+		    "%s: %s", device, strerror(errno));
+		return (errbuf);
+	}
+
+	(void) close(fd);
+	if (forked)
+		_exit(0);
+	return (NULL);
+}