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 * 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 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 110 ssh_sandbox_parent_finish(struct ssh_sandbox *box) 111 { 112 free(box); 113 debug3("%s: finished", __func__); 114 } 115 116 void 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
