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 __RCSID("$FreeBSD$"); 19 20 #ifdef SANDBOX_CAPSICUM 21 22 #include <sys/types.h> 23 #include <sys/param.h> 24 #include <sys/time.h> 25 #include <sys/resource.h> 26 #include <sys/capsicum.h> 27 28 #include <errno.h> 29 #include <stdarg.h> 30 #include <stdio.h> 31 #include <stdlib.h> 32 #include <string.h> 33 #include <unistd.h> 34 #include <capsicum_helpers.h> 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 * 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 70 ssh_sandbox_child(struct ssh_sandbox *box) 71 { 72 struct rlimit rl_zero; 73 cap_rights_t rights; 74 75 caph_cache_tzdata(); 76 77 rl_zero.rlim_cur = rl_zero.rlim_max = 0; 78 79 if (setrlimit(RLIMIT_FSIZE, &rl_zero) == -1) 80 fatal("%s: setrlimit(RLIMIT_FSIZE, { 0, 0 }): %s", 81 __func__, strerror(errno)); 82 #ifndef SANDBOX_SKIP_RLIMIT_NOFILE 83 if (setrlimit(RLIMIT_NOFILE, &rl_zero) == -1) 84 fatal("%s: setrlimit(RLIMIT_NOFILE, { 0, 0 }): %s", 85 __func__, strerror(errno)); 86 #endif 87 if (setrlimit(RLIMIT_NPROC, &rl_zero) == -1) 88 fatal("%s: setrlimit(RLIMIT_NPROC, { 0, 0 }): %s", 89 __func__, strerror(errno)); 90 91 cap_rights_init(&rights); 92 93 if (cap_rights_limit(STDIN_FILENO, &rights) < 0 && errno != ENOSYS) 94 fatal("can't limit stdin: %m"); 95 if (cap_rights_limit(STDOUT_FILENO, &rights) < 0 && errno != ENOSYS) 96 fatal("can't limit stdout: %m"); 97 if (cap_rights_limit(STDERR_FILENO, &rights) < 0 && errno != ENOSYS) 98 fatal("can't limit stderr: %m"); 99 100 cap_rights_init(&rights, CAP_READ, CAP_WRITE); 101 if (cap_rights_limit(box->monitor->m_recvfd, &rights) < 0 && 102 errno != ENOSYS) 103 fatal("%s: failed to limit the network socket", __func__); 104 cap_rights_init(&rights, CAP_WRITE); 105 if (cap_rights_limit(box->monitor->m_log_sendfd, &rights) < 0 && 106 errno != ENOSYS) 107 fatal("%s: failed to limit the logging socket", __func__); 108 if (cap_enter() < 0 && errno != ENOSYS) 109 fatal("%s: failed to enter capability mode", __func__); 110 111 } 112 113 void 114 ssh_sandbox_parent_finish(struct ssh_sandbox *box) 115 { 116 free(box); 117 debug3("%s: finished", __func__); 118 } 119 120 void 121 ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid) 122 { 123 box->child_pid = child_pid; 124 } 125 126 #endif /* SANDBOX_CAPSICUM */ 127