1 /* $NetBSD: openpam_check_owner_perms.c,v 1.4 2023/06/30 21:46:20 christos Exp $ */
2
3 /*-
4 * Copyright (c) 2011 Dag-Erling Smørgrav
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. The name of the author may not be used to endorse or promote
16 * products derived from this software without specific prior written
17 * permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 #ifdef HAVE_CONFIG_H
33 # include "config.h"
34 #endif
35
36 #include <sys/cdefs.h>
37 __RCSID("$NetBSD: openpam_check_owner_perms.c,v 1.4 2023/06/30 21:46:20 christos Exp $");
38
39 #include <sys/types.h>
40 #include <sys/stat.h>
41
42 #include <errno.h>
43 #include <limits.h>
44 #include <stdlib.h>
45 #include <string.h>
46 #include <unistd.h>
47
48 #include <security/pam_appl.h>
49
50 #include "openpam_impl.h"
51
52 /*
53 * OpenPAM internal
54 *
55 * Verify that the file or directory referenced by the given descriptor is
56 * owned by either root or the arbitrator and that it is not writable by
57 * group or other.
58 */
59
60 int
openpam_check_desc_owner_perms(const char * name,int fd)61 openpam_check_desc_owner_perms(const char *name, int fd)
62 {
63 uid_t root, arbitrator;
64 struct stat sb;
65 int serrno;
66
67 root = 0;
68 arbitrator = geteuid();
69 if (fstat(fd, &sb) != 0) {
70 serrno = errno;
71 openpam_log(PAM_LOG_ERROR, "%s: %s", name, strerror(errno));
72 errno = serrno;
73 return (-1);
74 }
75 if (!S_ISREG(sb.st_mode)) {
76 openpam_log(PAM_LOG_ERROR,
77 "%s: not a regular file", name);
78 errno = EINVAL;
79 return (-1);
80 }
81 if ((sb.st_uid != root && sb.st_uid != arbitrator) ||
82 (sb.st_mode & (S_IWGRP|S_IWOTH)) != 0) {
83 openpam_log(PAM_LOG_ERROR,
84 "%s: insecure ownership or permissions", name);
85 errno = EPERM;
86 return (-1);
87 }
88 return (0);
89 }
90
91 /*
92 * OpenPAM internal
93 *
94 * Verify that a file or directory and all components of the path leading
95 * up to it are owned by either root or the arbitrator and that they are
96 * not writable by group or other.
97 *
98 * Note that openpam_check_desc_owner_perms() should be used instead if
99 * possible to avoid a race between the ownership / permission check and
100 * the actual open().
101 */
102
103 int
openpam_check_path_owner_perms(const char * path)104 openpam_check_path_owner_perms(const char *path)
105 {
106 uid_t root, arbitrator;
107 char pathbuf[PATH_MAX];
108 struct stat sb;
109 size_t len;
110 int serrno, tip;
111
112 tip = 1;
113 root = 0;
114 arbitrator = geteuid();
115 if (realpath(path, pathbuf) == NULL)
116 return (-1);
117 len = strlen(pathbuf);
118 while (len > 0) {
119 if (stat(pathbuf, &sb) != 0) {
120 if (errno != ENOENT) {
121 serrno = errno;
122 openpam_log(PAM_LOG_ERROR, "%s: %m", pathbuf);
123 errno = serrno;
124 }
125 return (-1);
126 }
127 if (tip && !S_ISREG(sb.st_mode)) {
128 openpam_log(PAM_LOG_ERROR,
129 "%s: not a regular file", pathbuf);
130 errno = EINVAL;
131 return (-1);
132 }
133 if ((sb.st_uid != root && sb.st_uid != arbitrator) ||
134 (sb.st_mode & (S_IWGRP|S_IWOTH)) != 0) {
135 openpam_log(PAM_LOG_ERROR,
136 "%s: insecure ownership or permissions", pathbuf);
137 errno = EPERM;
138 return (-1);
139 }
140 while (--len > 0 && pathbuf[len] != '/')
141 pathbuf[len] = '\0';
142 tip = 0;
143 }
144 return (0);
145 }
146
147 /*
148 * NOPARSE
149 */
150