1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
|
/* $OpenBSD: locking.c,v 1.8 2006/04/01 22:48:57 deraadt Exp $ */
/*
* Copyright (c) 1996-1998 Theo de Raadt <deraadt@theos.com>
* Copyright (c) 1996-1998 David Mazieres <dm@lcs.mit.edu>
* 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. The name of the authors may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED ``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 AUTHORS 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: locking.c,v 1.8 2006/04/01 22:48:57 deraadt Exp $";
#endif /* not lint */
#include <sys/param.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <pwd.h>
#include <syslog.h>
#include <time.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include "pathnames.h"
#include "mail.local.h"
static char lpath[MAXPATHLEN];
void
rellock(void)
{
if (lpath[0])
unlink(lpath);
}
int
getlock(char *name, struct passwd *pw)
{
struct stat sb, fsb;
int lfd=-1;
char buf[8*1024];
int tries = 0;
(void)snprintf(lpath, sizeof lpath, "%s/%s.lock",
_PATH_MAILDIR, name);
if (stat(_PATH_MAILDIR, &sb) != -1 &&
(sb.st_mode & S_IWOTH) == S_IWOTH) {
/*
* We have a writeable spool, deal with it as
* securely as possible.
*/
time_t ctim = -1;
seteuid(pw->pw_uid);
if (lstat(lpath, &sb) != -1)
ctim = sb.st_ctime;
while (1) {
/*
* Deal with existing user.lock files
* or directories or symbolic links that
* should not be here.
*/
if (readlink(lpath, buf, sizeof buf-1) != -1) {
if (lstat(lpath, &sb) != -1 &&
S_ISLNK(sb.st_mode)) {
seteuid(sb.st_uid);
unlink(lpath);
seteuid(pw->pw_uid);
}
goto again;
}
if ((lfd = open(lpath, O_CREAT|O_WRONLY|O_EXCL|O_EXLOCK,
S_IRUSR|S_IWUSR)) != -1)
break;
again:
if (tries > 10) {
merr(NOTFATAL, "%s: %s", lpath,
strerror(errno));
seteuid(0);
return(-1);
}
if (tries > 9 &&
(lfd = open(lpath, O_WRONLY|O_EXLOCK, 0)) != -1) {
if (fstat(lfd, &fsb) != -1 &&
lstat(lpath, &sb) != -1) {
if (fsb.st_dev == sb.st_dev &&
fsb.st_ino == sb.st_ino &&
ctim == fsb.st_ctime ) {
seteuid(fsb.st_uid);
baditem(lpath);
seteuid(pw->pw_uid);
}
}
}
sleep(1U << tries);
tries++;
continue;
}
seteuid(0);
} else {
/*
* Only root can write the spool directory.
*/
while (1) {
if ((lfd = open(lpath, O_CREAT|O_WRONLY|O_EXCL,
S_IRUSR|S_IWUSR)) != -1)
break;
if (tries > 9) {
merr(NOTFATAL, "%s: %s", lpath, strerror(errno));
return(-1);
}
sleep(1U << tries);
tries++;
}
}
return(lfd);
}
void
baditem(char *path)
{
char npath[MAXPATHLEN];
if (unlink(path) == 0)
return;
snprintf(npath, sizeof npath, "%s/mailXXXXXXXXXX", _PATH_MAILDIR);
if (mktemp(npath) == NULL)
return;
if (rename(path, npath) == -1)
unlink(npath);
else
merr(NOTFATAL, "nasty spool item %s renamed to %s",
path, npath);
/* XXX if we fail to rename, another attempt will happen later */
}
void
merr(int isfatal, const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
vsyslog(LOG_ERR, fmt, ap);
va_end(ap);
if (isfatal)
exit(1);
}
|
