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 int m_recvfd;
49 int m_log_sendfd;
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 debug3("%s: preparing capsicum sandbox", __func__);
58 box = xcalloc(1, sizeof(*box));
59 box->m_recvfd = monitor->m_recvfd;
60 box->m_log_sendfd = monitor->m_log_sendfd;
61 return box;
62 }
63
64 void
ssh_sandbox_child(struct ssh_sandbox * box)65 ssh_sandbox_child(struct ssh_sandbox *box)
66 {
67 struct rlimit rl_zero;
68 cap_rights_t rights;
69
70 #ifdef HAVE_CAPH_CACHE_TZDATA
71 caph_cache_tzdata();
72 #endif
73
74 rl_zero.rlim_cur = rl_zero.rlim_max = 0;
75
76 if (setrlimit(RLIMIT_FSIZE, &rl_zero) == -1)
77 fatal("%s: setrlimit(RLIMIT_FSIZE, { 0, 0 }): %s",
78 __func__, strerror(errno));
79 #ifndef SANDBOX_SKIP_RLIMIT_NOFILE
80 if (setrlimit(RLIMIT_NOFILE, &rl_zero) == -1)
81 fatal("%s: setrlimit(RLIMIT_NOFILE, { 0, 0 }): %s",
82 __func__, strerror(errno));
83 #endif
84 if (setrlimit(RLIMIT_NPROC, &rl_zero) == -1)
85 fatal("%s: setrlimit(RLIMIT_NPROC, { 0, 0 }): %s",
86 __func__, strerror(errno));
87
88 cap_rights_init(&rights);
89
90 if (cap_rights_limit(STDIN_FILENO, &rights) < 0 && errno != ENOSYS)
91 fatal("can't limit stdin: %m");
92 if (cap_rights_limit(STDOUT_FILENO, &rights) < 0 && errno != ENOSYS)
93 fatal("can't limit stdout: %m");
94 if (cap_rights_limit(STDERR_FILENO, &rights) < 0 && errno != ENOSYS)
95 fatal("can't limit stderr: %m");
96
97 cap_rights_init(&rights, CAP_READ, CAP_WRITE);
98 if (cap_rights_limit(box->m_recvfd, &rights) < 0 &&
99 errno != ENOSYS)
100 fatal("%s: failed to limit the network socket", __func__);
101 cap_rights_init(&rights, CAP_WRITE);
102 if (cap_rights_limit(box->m_log_sendfd, &rights) < 0 &&
103 errno != ENOSYS)
104 fatal("%s: failed to limit the logging socket", __func__);
105 if (cap_enter() < 0 && errno != ENOSYS)
106 fatal("%s: failed to enter capability mode", __func__);
107
108 }
109
110 #endif /* SANDBOX_CAPSICUM */
111