1 /*
2 * Copyright (c) 2011 Dag-Erling Smorgrav
3 *
4 * Permission to use, copy, modify, and distribute this software for any
5 * purpose with or without fee is hereby granted, provided that the above
6 * copyright notice and this permission notice appear in all copies.
7 *
8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15 */
16
17 #include "includes.h"
18
19 #ifdef SANDBOX_CAPSICUM
20
21 #include <sys/types.h>
22 #include <sys/time.h>
23 #include <sys/resource.h>
24 #include <sys/capsicum.h>
25
26 #include <errno.h>
27 #include <stdarg.h>
28 #include <stdio.h>
29 #include <stdlib.h>
30 #include <string.h>
31 #include <unistd.h>
32 #ifdef HAVE_CAPSICUM_HELPERS_H
33 #include <capsicum_helpers.h>
34 #endif
35
36 #include "log.h"
37 #include "monitor.h"
38 #include "ssh-sandbox.h"
39 #include "xmalloc.h"
40
41 /*
42 * Capsicum sandbox that sets zero nfiles, nprocs and filesize rlimits,
43 * limits rights on stdout, stdin, stderr, monitor and switches to
44 * capability mode.
45 */
46
47 struct ssh_sandbox {
48 struct monitor *monitor;
49 pid_t child_pid;
50 };
51
52 struct ssh_sandbox *
ssh_sandbox_init(struct monitor * monitor)53 ssh_sandbox_init(struct monitor *monitor)
54 {
55 struct ssh_sandbox *box;
56
57 /*
58 * Strictly, we don't need to maintain any state here but we need
59 * to return non-NULL to satisfy the API.
60 */
61 debug3("%s: preparing capsicum sandbox", __func__);
62 box = xcalloc(1, sizeof(*box));
63 box->monitor = monitor;
64 box->child_pid = 0;
65
66 return box;
67 }
68
69 void
ssh_sandbox_child(struct ssh_sandbox * box)70 ssh_sandbox_child(struct ssh_sandbox *box)
71 {
72 struct rlimit rl_zero;
73 cap_rights_t rights;
74
75 #ifdef HAVE_CAPH_CACHE_TZDATA
76 caph_cache_tzdata();
77 #endif
78
79 rl_zero.rlim_cur = rl_zero.rlim_max = 0;
80
81 if (setrlimit(RLIMIT_FSIZE, &rl_zero) == -1)
82 fatal("%s: setrlimit(RLIMIT_FSIZE, { 0, 0 }): %s",
83 __func__, strerror(errno));
84 #ifndef SANDBOX_SKIP_RLIMIT_NOFILE
85 if (setrlimit(RLIMIT_NOFILE, &rl_zero) == -1)
86 fatal("%s: setrlimit(RLIMIT_NOFILE, { 0, 0 }): %s",
87 __func__, strerror(errno));
88 #endif
89 if (setrlimit(RLIMIT_NPROC, &rl_zero) == -1)
90 fatal("%s: setrlimit(RLIMIT_NPROC, { 0, 0 }): %s",
91 __func__, strerror(errno));
92
93 cap_rights_init(&rights);
94
95 if (cap_rights_limit(STDIN_FILENO, &rights) < 0 && errno != ENOSYS)
96 fatal("can't limit stdin: %m");
97 if (cap_rights_limit(STDOUT_FILENO, &rights) < 0 && errno != ENOSYS)
98 fatal("can't limit stdout: %m");
99 if (cap_rights_limit(STDERR_FILENO, &rights) < 0 && errno != ENOSYS)
100 fatal("can't limit stderr: %m");
101
102 cap_rights_init(&rights, CAP_READ, CAP_WRITE);
103 if (cap_rights_limit(box->monitor->m_recvfd, &rights) < 0 &&
104 errno != ENOSYS)
105 fatal("%s: failed to limit the network socket", __func__);
106 cap_rights_init(&rights, CAP_WRITE);
107 if (cap_rights_limit(box->monitor->m_log_sendfd, &rights) < 0 &&
108 errno != ENOSYS)
109 fatal("%s: failed to limit the logging socket", __func__);
110 if (cap_enter() < 0 && errno != ENOSYS)
111 fatal("%s: failed to enter capability mode", __func__);
112
113 }
114
115 void
ssh_sandbox_parent_finish(struct ssh_sandbox * box)116 ssh_sandbox_parent_finish(struct ssh_sandbox *box)
117 {
118 free(box);
119 debug3("%s: finished", __func__);
120 }
121
122 void
ssh_sandbox_parent_preauth(struct ssh_sandbox * box,pid_t child_pid)123 ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid)
124 {
125 box->child_pid = child_pid;
126 }
127
128 #endif /* SANDBOX_CAPSICUM */
129