1 /*-
2  * Copyright (c) 2009-2011 Robert N. M. Watson
3  * Copyright (c) 2011 Jonathan Anderson
4  * All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25  * SUCH DAMAGE.
26  */
27 
28 #include <sys/cdefs.h>
29 #include <sys/param.h>
30 #include <sys/capsicum.h>
31 #include <sys/errno.h>
32 
33 #include <err.h>
34 #include <fcntl.h>
35 #include <stdlib.h>
36 #include <string.h>
37 #include <unistd.h>
38 
39 #include "cap_test.h"
40 
41 /*
42  * Test openat(2) in a variety of sitations to ensure that it obeys Capsicum
43  * "strict relative" rules:
44  *
45  * 1. Use strict relative lookups in capability mode or when operating
46  *    relative to a capability.
47  * 2. When performing strict relative lookups, absolute paths (including
48  *    symlinks to absolute paths) are not allowed, nor are paths containing
49  *    '..' components.
50  */
51 int
52 test_relative(void)
53 {
54 	int success = PASSED;
55 	int fd, etc, etc_cap, etc_cap_ro, etc_cap_base, etc_cap_all;
56 	cap_rights_t baserights = CAP_READ | CAP_WRITE | CAP_SEEK | CAP_LOOKUP;
57 	cap_rights_t rights;
58 
59 	REQUIRE(etc = open("/etc/", O_RDONLY));
60 	CHECK_SYSCALL_SUCCEEDS(cap_getrights, etc, &rights);
61 	CHECK_RIGHTS(rights, CAP_ALL);
62 
63 	MAKE_CAPABILITY(etc_cap, etc, CAP_READ);
64 	MAKE_CAPABILITY(etc_cap_ro, etc, CAP_READ | CAP_LOOKUP);
65 	MAKE_CAPABILITY(etc_cap_base, etc, baserights);
66 	MAKE_CAPABILITY(etc_cap_all, etc, CAP_MASK_VALID);
67 
68 	/*
69 	 * openat(2) with regular file descriptors in non-capability mode
70 	 * should Just Work (tm).
71 	 */
72 	CHECK_SYSCALL_SUCCEEDS(openat, etc, "/etc/passwd", O_RDONLY);
73 	CHECK_SYSCALL_SUCCEEDS(openat, AT_FDCWD, "/etc/passwd", O_RDONLY);
74 	CHECK_SYSCALL_SUCCEEDS(openat, etc, "passwd", O_RDONLY);
75 	CHECK_SYSCALL_SUCCEEDS(openat, etc, "../etc/passwd", O_RDONLY);
76 
77 	/*
78 	 * Lookups relative to capabilities should be strictly relative.
79 	 *
80 	 * When not in capability mode, we don't actually require CAP_LOOKUP.
81 	 */
82 	CHECK_SYSCALL_SUCCEEDS(openat, etc_cap_ro, "passwd", O_RDONLY);
83 	CHECK_SYSCALL_SUCCEEDS(openat, etc_cap_base, "passwd", O_RDONLY);
84 	CHECK_SYSCALL_SUCCEEDS(openat, etc_cap_all, "passwd", O_RDONLY);
85 
86 	CHECK_NOTCAPABLE(openat, etc_cap_ro, "../etc/passwd", O_RDONLY);
87 	CHECK_NOTCAPABLE(openat, etc_cap_base, "../etc/passwd", O_RDONLY);
88 
89 	/*
90 	 * This requires discussion: do we treat a capability with
91 	 * CAP_MASK_VALID *exactly* like a non-capability file descriptor
92 	 * (currently, the implementation says yes)?
93 	 */
94 	CHECK_SYSCALL_SUCCEEDS(openat, etc_cap_all, "../etc/passwd", O_RDONLY);
95 
96 	/*
97 	 * A file opened relative to a capability should itself be a capability.
98 	 */
99 	CHECK_SYSCALL_SUCCEEDS(cap_getrights, etc_cap_base, &rights);
100 
101 	REQUIRE(fd = openat(etc_cap_base, "passwd", O_RDONLY));
102 	CHECK_SYSCALL_SUCCEEDS(cap_getrights, fd, &rights);
103 	CHECK_RIGHTS(rights, baserights);
104 
105 	/*
106 	 * Enter capability mode; now ALL lookups are strictly relative.
107 	 */
108 	REQUIRE(cap_enter());
109 
110 	/*
111 	 * Relative lookups on regular files or capabilities with CAP_LOOKUP
112 	 * ought to succeed.
113 	 */
114 	CHECK_SYSCALL_SUCCEEDS(openat, etc, "passwd", O_RDONLY);
115 	CHECK_SYSCALL_SUCCEEDS(openat, etc_cap_ro, "passwd", O_RDONLY);
116 	CHECK_SYSCALL_SUCCEEDS(openat, etc_cap_base, "passwd", O_RDONLY);
117 	CHECK_SYSCALL_SUCCEEDS(openat, etc_cap_all, "passwd", O_RDONLY);
118 
119 	/*
120 	 * Lookup relative to capabilities without CAP_LOOKUP should fail.
121 	 */
122 	CHECK_NOTCAPABLE(openat, etc_cap, "passwd", O_RDONLY);
123 
124 	/*
125 	 * Absolute lookups should fail.
126 	 */
127 	CHECK_CAPMODE(openat, AT_FDCWD, "/etc/passwd", O_RDONLY);
128 	CHECK_NOTCAPABLE(openat, etc, "/etc/passwd", O_RDONLY);
129 
130 	/*
131 	 * Lookups containing '..' should fail in capability mode.
132 	 */
133 	CHECK_NOTCAPABLE(openat, etc, "../etc/passwd", O_RDONLY);
134 	CHECK_NOTCAPABLE(openat, etc_cap_ro, "../etc/passwd", O_RDONLY);
135 	CHECK_NOTCAPABLE(openat, etc_cap_base, "../etc/passwd", O_RDONLY);
136 
137 	REQUIRE(fd = openat(etc, "passwd", O_RDONLY));
138 	CHECK_SYSCALL_SUCCEEDS(cap_getrights, fd, &rights);
139 
140 	/*
141 	 * A file opened relative to a capability should itself be a capability.
142 	 */
143 	REQUIRE(fd = openat(etc_cap_base, "passwd", O_RDONLY));
144 	CHECK_SYSCALL_SUCCEEDS(cap_getrights, fd, &rights);
145 	CHECK_RIGHTS(rights, baserights);
146 
147 	return success;
148 }
149