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 * 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 #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 116 ssh_sandbox_parent_finish(struct ssh_sandbox *box) 117 { 118 free(box); 119 debug3("%s: finished", __func__); 120 } 121 122 void 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