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/param.h>
23 #include <sys/time.h>
24 #include <sys/resource.h>
25 #include <sys/capability.h>
26
27 #include <errno.h>
28 #include <stdarg.h>
29 #include <stdio.h>
30 #include <stdlib.h>
31 #include <string.h>
32 #include <unistd.h>
33
34 #include "log.h"
35 #include "monitor.h"
36 #include "ssh-sandbox.h"
37 #include "xmalloc.h"
38
39 /*
40 * Capsicum sandbox that sets zero nfiles, nprocs and filesize rlimits,
41 * limits rights on stdout, stdin, stderr, monitor and switches to
42 * capability mode.
43 */
44
45 struct ssh_sandbox {
46 struct monitor *monitor;
47 pid_t child_pid;
48 };
49
50 struct ssh_sandbox *
ssh_sandbox_init(struct monitor * monitor)51 ssh_sandbox_init(struct monitor *monitor)
52 {
53 struct ssh_sandbox *box;
54
55 /*
56 * Strictly, we don't need to maintain any state here but we need
57 * to return non-NULL to satisfy the API.
58 */
59 debug3("%s: preparing capsicum sandbox", __func__);
60 box = xcalloc(1, sizeof(*box));
61 box->monitor = monitor;
62 box->child_pid = 0;
63
64 return box;
65 }
66
67 void
ssh_sandbox_child(struct ssh_sandbox * box)68 ssh_sandbox_child(struct ssh_sandbox *box)
69 {
70 struct rlimit rl_zero;
71 cap_rights_t rights;
72
73 rl_zero.rlim_cur = rl_zero.rlim_max = 0;
74
75 if (setrlimit(RLIMIT_FSIZE, &rl_zero) == -1)
76 fatal("%s: setrlimit(RLIMIT_FSIZE, { 0, 0 }): %s",
77 __func__, strerror(errno));
78 #ifndef SANDBOX_SKIP_RLIMIT_NOFILE
79 if (setrlimit(RLIMIT_NOFILE, &rl_zero) == -1)
80 fatal("%s: setrlimit(RLIMIT_NOFILE, { 0, 0 }): %s",
81 __func__, strerror(errno));
82 #endif
83 if (setrlimit(RLIMIT_NPROC, &rl_zero) == -1)
84 fatal("%s: setrlimit(RLIMIT_NPROC, { 0, 0 }): %s",
85 __func__, strerror(errno));
86
87 cap_rights_init(&rights);
88
89 if (cap_rights_limit(STDIN_FILENO, &rights) < 0 && errno != ENOSYS)
90 fatal("can't limit stdin: %m");
91 if (cap_rights_limit(STDOUT_FILENO, &rights) < 0 && errno != ENOSYS)
92 fatal("can't limit stdout: %m");
93 if (cap_rights_limit(STDERR_FILENO, &rights) < 0 && errno != ENOSYS)
94 fatal("can't limit stderr: %m");
95
96 cap_rights_init(&rights, CAP_READ, CAP_WRITE);
97 if (cap_rights_limit(box->monitor->m_recvfd, &rights) < 0 &&
98 errno != ENOSYS)
99 fatal("%s: failed to limit the network socket", __func__);
100 cap_rights_init(&rights, CAP_WRITE);
101 if (cap_rights_limit(box->monitor->m_log_sendfd, &rights) < 0 &&
102 errno != ENOSYS)
103 fatal("%s: failed to limit the logging socket", __func__);
104 if (cap_enter() < 0 && errno != ENOSYS)
105 fatal("%s: failed to enter capability mode", __func__);
106
107 }
108
109 void
ssh_sandbox_parent_finish(struct ssh_sandbox * box)110 ssh_sandbox_parent_finish(struct ssh_sandbox *box)
111 {
112 free(box);
113 debug3("%s: finished", __func__);
114 }
115
116 void
ssh_sandbox_parent_preauth(struct ssh_sandbox * box,pid_t child_pid)117 ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid)
118 {
119 box->child_pid = child_pid;
120 }
121
122 #endif /* SANDBOX_CAPSICUM */
123