from christos;

- Fix PR/105: Implement dot locking protocol and check return value of flock.
- Fix PR/2247: Don't call unknown users "ubluit". Issue an error message.
- Fix/add prototypes.
- Fix warnings.
- Use POSIX signal mask calls.

1 files changed, 198 insertions, 0 deletions

diff --git a/usr.bin/mail/dotlock.c b/usr.bin/mail/dotlock.c
new file mode 100644
index 00000000000..a16bf531ed1
--- /dev/null
+++ b/usr.bin/mail/dotlock.c
@@ -0,0 +1,198 @@
+/*	$OpenBSD: dotlock.c,v 1.1 1996/06/11 12:53:37 deraadt Exp $	*/
+/*	$NetBSD: dotlock.c,v 1.1 1996/06/08 19:48:19 christos Exp $	*/
+
+/*
+ * Copyright (c) 1996 Christos Zoulas.  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. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by Christos Zoulas.
+ * 4. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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
+static char rcsid[] = "$OpenBSD: dotlock.c,v 1.1 1996/06/11 12:53:37 deraadt Exp $";
+#endif
+
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+
+#include <stdio.h>
+#include <string.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <signal.h>
+
+#include "extern.h"
+
+#ifndef O_SYNC
+#define O_SYNC	0
+#endif
+
+static int create_exclusive __P((const char *));
+/*
+ * Create a unique file. O_EXCL does not really work over NFS so we follow
+ * the following trick: [Inspired by  S.R. van den Berg]
+ *
+ * - make a mostly unique filename and try to create it.
+ * - link the unique filename to our target
+ * - get the link count of the target
+ * - unlink the mostly unique filename
+ * - if the link count was 2, then we are ok; else we've failed.
+ */
+static int
+create_exclusive(fname)
+	const char *fname;
+{
+	char path[MAXPATHLEN], hostname[MAXHOSTNAMELEN];
+	const char *ptr;
+	struct timeval tv;
+	pid_t pid;
+	size_t ntries, cookie;
+	int fd, serrno;
+	struct stat st;
+
+	(void) gettimeofday(&tv, NULL);
+	(void) gethostname(hostname, MAXHOSTNAMELEN);
+	pid = getpid();
+
+	cookie = pid ^ tv.tv_usec;
+
+	/*
+	 * We generate a semi-unique filename, from hostname.(pid ^ usec)
+	 */
+	if ((ptr = strrchr(fname, '/')) == NULL)
+		ptr = fname;
+	else
+		ptr++;
+
+	(void) snprintf(path, sizeof(path), "%.*s.%s.%x", 
+	    ptr - fname, fname, hostname, cookie);
+
+	/*
+	 * We try to create the unique filename.
+	 */
+	for (ntries = 0; ntries < 5; ntries++) {
+		fd = open(path, O_WRONLY|O_CREAT|O_TRUNC|O_EXCL|O_SYNC, 0);
+		if (fd != -1) {
+			(void) close(fd);
+			break;
+		}
+		else if (errno == EEXIST)
+			continue;
+		else
+			return -1;
+	}
+
+	/*
+	 * We link the path to the name
+	 */
+	if (link(path, fname) == -1)
+		goto bad;
+
+	/*
+	 * Note that we stat our own exclusively created name, not the
+	 * destination, since the destination can be affected by others.
+	 */
+	if (stat(path, &st) == -1)
+		goto bad;
+
+	(void) unlink(path);
+
+	/*
+	 * If the number of links was two (one for the unique file and one
+	 * for the lock), we've won the race
+	 */
+	if (st.st_nlink != 2) {
+		errno = EEXIST;
+		return -1;
+	}
+	return 0;
+
+bad:
+	serrno = errno;
+	(void) unlink(path);
+	errno = serrno;
+	return -1;
+}
+
+int
+dot_lock(fname, pollinterval, fp, msg)
+	const char *fname;	/* Pathname to lock */
+	int pollinterval;	/* Interval to check for lock, -1 return */
+	FILE *fp;		/* File to print message */
+	const char *msg;	/* Message to print */
+{
+	char path[MAXPATHLEN];
+	sigset_t nset, oset;
+
+	sigemptyset(&nset);
+	sigaddset(&nset, SIGHUP);
+	sigaddset(&nset, SIGINT);
+	sigaddset(&nset, SIGQUIT);
+	sigaddset(&nset, SIGTERM);
+	sigaddset(&nset, SIGTTIN);
+	sigaddset(&nset, SIGTTOU);
+	sigaddset(&nset, SIGTSTP);
+	sigaddset(&nset, SIGCHLD);
+
+	(void) snprintf(path, sizeof(path), "%s.lock", fname);
+
+	for (;;) {
+		(void) sigprocmask(SIG_BLOCK, &nset, &oset);
+		if (create_exclusive(path) != -1) {
+			(void) sigprocmask(SIG_SETMASK, &oset, NULL);
+			return 0;
+		}
+		else
+			(void) sigprocmask(SIG_SETMASK, &oset, NULL);
+
+		if (errno != EEXIST)
+			return -1;
+
+		if (fp && msg)
+		    (void) fputs(msg, fp);
+
+		if (pollinterval) {
+			if (pollinterval == -1) {
+				errno = EEXIST;
+				return -1;
+			}
+			sleep(pollinterval);
+		}
+	}
+}
+
+void
+dot_unlock(fname)
+	const char *fname;
+{
+	char path[MAXPATHLEN];
+
+	(void) snprintf(path, sizeof(path), "%s.lock", fname);
+	(void) unlink(path);
+}