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/* $OpenBSD: locking.c,v 1.12 2015/01/16 06:39:50 deraadt Exp $ */ |
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/* |
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* Copyright (c) 1996-1998 Theo de Raadt <deraadt@theos.com> |
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* Copyright (c) 1996-1998 David Mazieres <dm@lcs.mit.edu> |
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* All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions |
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* are met: |
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* 1. Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in the |
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* documentation and/or other materials provided with the distribution. |
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* 3. The name of the authors may not be used to endorse or promote products |
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* derived from this software without specific prior written permission. |
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* |
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, |
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY |
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* AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL |
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* THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, |
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; |
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* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR |
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* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF |
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* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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*/ |
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#include <sys/types.h> |
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#include <sys/stat.h> |
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#include <fcntl.h> |
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#include <pwd.h> |
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#include <syslog.h> |
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#include <time.h> |
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#include <unistd.h> |
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#include <limits.h> |
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#include <errno.h> |
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#include <stdio.h> |
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#include <stdlib.h> |
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#include <string.h> |
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#include <stdarg.h> |
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#include "pathnames.h" |
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#include "mail.local.h" |
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static char lpath[PATH_MAX]; |
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void |
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rellock(void) |
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{ |
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if (lpath[0]) |
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unlink(lpath); |
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} |
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int |
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getlock(char *name, struct passwd *pw) |
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{ |
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struct stat sb, fsb; |
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int lfd=-1; |
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char buf[8*1024]; |
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int tries = 0; |
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(void)snprintf(lpath, sizeof lpath, "%s/%s.lock", |
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_PATH_MAILDIR, name); |
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if (stat(_PATH_MAILDIR, &sb) != -1 && |
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(sb.st_mode & S_IWOTH) == S_IWOTH) { |
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/* |
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* We have a writeable spool, deal with it as |
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* securely as possible. |
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*/ |
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time_t ctim = -1; |
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seteuid(pw->pw_uid); |
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if (lstat(lpath, &sb) != -1) |
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ctim = sb.st_ctime; |
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while (1) { |
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/* |
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* Deal with existing user.lock files |
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* or directories or symbolic links that |
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* should not be here. |
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*/ |
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if (readlink(lpath, buf, sizeof buf-1) != -1) { |
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if (lstat(lpath, &sb) != -1 && |
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S_ISLNK(sb.st_mode)) { |
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seteuid(sb.st_uid); |
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unlink(lpath); |
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seteuid(pw->pw_uid); |
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} |
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goto again; |
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} |
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if ((lfd = open(lpath, O_CREAT|O_WRONLY|O_EXCL|O_EXLOCK, |
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S_IRUSR|S_IWUSR)) != -1) |
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break; |
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again: |
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if (tries > 10) { |
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merr(NOTFATAL, "%s: %s", lpath, |
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strerror(errno)); |
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seteuid(0); |
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return(-1); |
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} |
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if (tries > 9 && |
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(lfd = open(lpath, O_WRONLY|O_EXLOCK, 0)) != -1) { |
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if (fstat(lfd, &fsb) != -1 && |
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lstat(lpath, &sb) != -1) { |
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if (fsb.st_dev == sb.st_dev && |
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fsb.st_ino == sb.st_ino && |
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ctim == fsb.st_ctime ) { |
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seteuid(fsb.st_uid); |
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baditem(lpath); |
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seteuid(pw->pw_uid); |
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} |
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} |
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close(lfd); |
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} |
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sleep(1U << tries); |
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tries++; |
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continue; |
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} |
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seteuid(0); |
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} else { |
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/* |
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* Only root can write the spool directory. |
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*/ |
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while (1) { |
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if ((lfd = open(lpath, O_CREAT|O_WRONLY|O_EXCL, |
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S_IRUSR|S_IWUSR)) != -1) |
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break; |
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if (tries > 9) { |
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merr(NOTFATAL, "%s: %s", lpath, strerror(errno)); |
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return(-1); |
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} |
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sleep(1U << tries); |
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tries++; |
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} |
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} |
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return(lfd); |
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} |
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void |
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baditem(char *path) |
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{ |
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char npath[PATH_MAX]; |
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int fd; |
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if (unlink(path) == 0) |
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return; |
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snprintf(npath, sizeof npath, "%s/mailXXXXXXXXXX", _PATH_MAILDIR); |
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if ((fd = mkstemp(npath)) == -1) |
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return; |
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close(fd); |
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if (rename(path, npath) == -1) |
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unlink(npath); |
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else |
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merr(NOTFATAL, "nasty spool item %s renamed to %s", |
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path, npath); |
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/* XXX if we fail to rename, another attempt will happen later */ |
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} |
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void |
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merr(int isfatal, const char *fmt, ...) |
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{ |
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va_list ap; |
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va_start(ap, fmt); |
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vsyslog(LOG_ERR, fmt, ap); |
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va_end(ap); |
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if (isfatal) |
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exit(1); |
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} |