Damien Miller | 35e4819 | 2011-08-06 06:16:23 +1000 | [diff] [blame] | 1 | /* $OpenBSD: sandbox-systrace.c,v 1.4 2011/07/29 14:42:45 djm Exp $ */ |
Damien Miller | 69ff1df | 2011-06-23 08:30:03 +1000 | [diff] [blame] | 2 | /* |
| 3 | * Copyright (c) 2011 Damien Miller <djm@mindrot.org> |
| 4 | * |
| 5 | * Permission to use, copy, modify, and distribute this software for any |
| 6 | * purpose with or without fee is hereby granted, provided that the above |
| 7 | * copyright notice and this permission notice appear in all copies. |
| 8 | * |
| 9 | * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
| 10 | * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
| 11 | * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR |
| 12 | * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
| 13 | * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN |
| 14 | * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF |
| 15 | * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
| 16 | */ |
| 17 | |
| 18 | #include "includes.h" |
| 19 | |
| 20 | #ifdef SANDBOX_SYSTRACE |
| 21 | |
| 22 | #include <sys/types.h> |
| 23 | #include <sys/param.h> |
| 24 | #include <sys/ioctl.h> |
| 25 | #include <sys/syscall.h> |
| 26 | #include <sys/socket.h> |
| 27 | |
| 28 | #include <dev/systrace.h> |
| 29 | |
| 30 | #include <errno.h> |
| 31 | #include <fcntl.h> |
| 32 | #include <limits.h> |
| 33 | #include <stdarg.h> |
| 34 | #include <stdio.h> |
| 35 | #include <stdlib.h> |
| 36 | #include <string.h> |
| 37 | #include <unistd.h> |
| 38 | |
| 39 | #include "atomicio.h" |
| 40 | #include "log.h" |
Damien Miller | dcbd41e | 2011-06-23 19:45:51 +1000 | [diff] [blame] | 41 | #include "ssh-sandbox.h" |
Damien Miller | 69ff1df | 2011-06-23 08:30:03 +1000 | [diff] [blame] | 42 | #include "xmalloc.h" |
| 43 | |
Damien Miller | 35e4819 | 2011-08-06 06:16:23 +1000 | [diff] [blame] | 44 | struct sandbox_policy { |
| 45 | int syscall; |
| 46 | int action; |
| 47 | }; |
| 48 | |
| 49 | /* Permitted syscalls in preauth. Unlisted syscalls get SYSTR_POLICY_KILL */ |
| 50 | static const struct sandbox_policy preauth_policy[] = { |
| 51 | { SYS_open, SYSTR_POLICY_NEVER }, |
| 52 | |
| 53 | { SYS___sysctl, SYSTR_POLICY_PERMIT }, |
| 54 | { SYS_close, SYSTR_POLICY_PERMIT }, |
| 55 | { SYS_exit, SYSTR_POLICY_PERMIT }, |
| 56 | { SYS_getpid, SYSTR_POLICY_PERMIT }, |
| 57 | { SYS_gettimeofday, SYSTR_POLICY_PERMIT }, |
| 58 | { SYS_madvise, SYSTR_POLICY_PERMIT }, |
| 59 | { SYS_mmap, SYSTR_POLICY_PERMIT }, |
| 60 | { SYS_mprotect, SYSTR_POLICY_PERMIT }, |
| 61 | { SYS_poll, SYSTR_POLICY_PERMIT }, |
| 62 | { SYS_munmap, SYSTR_POLICY_PERMIT }, |
| 63 | { SYS_read, SYSTR_POLICY_PERMIT }, |
| 64 | { SYS_select, SYSTR_POLICY_PERMIT }, |
| 65 | { SYS_sigprocmask, SYSTR_POLICY_PERMIT }, |
| 66 | { SYS_write, SYSTR_POLICY_PERMIT }, |
| 67 | { -1, -1 } |
Damien Miller | 69ff1df | 2011-06-23 08:30:03 +1000 | [diff] [blame] | 68 | }; |
| 69 | |
| 70 | struct ssh_sandbox { |
| 71 | int child_sock; |
| 72 | int parent_sock; |
| 73 | int systrace_fd; |
| 74 | pid_t child_pid; |
Damien Miller | 69ff1df | 2011-06-23 08:30:03 +1000 | [diff] [blame] | 75 | }; |
| 76 | |
| 77 | struct ssh_sandbox * |
| 78 | ssh_sandbox_init(void) |
| 79 | { |
| 80 | struct ssh_sandbox *box; |
| 81 | int s[2]; |
| 82 | |
| 83 | debug3("%s: preparing systrace sandbox", __func__); |
| 84 | box = xcalloc(1, sizeof(*box)); |
| 85 | if (socketpair(AF_UNIX, SOCK_STREAM, 0, s) == -1) |
| 86 | fatal("%s: socketpair: %s", __func__, strerror(errno)); |
| 87 | box->child_sock = s[0]; |
| 88 | box->parent_sock = s[1]; |
| 89 | box->systrace_fd = -1; |
| 90 | box->child_pid = 0; |
| 91 | |
| 92 | return box; |
| 93 | } |
| 94 | |
| 95 | void |
| 96 | ssh_sandbox_child(struct ssh_sandbox *box) |
| 97 | { |
| 98 | char whatever = 0; |
| 99 | |
| 100 | close(box->parent_sock); |
| 101 | /* Signal parent that we are ready */ |
| 102 | debug3("%s: ready", __func__); |
| 103 | if (atomicio(vwrite, box->child_sock, &whatever, 1) != 1) |
| 104 | fatal("%s: write: %s", __func__, strerror(errno)); |
| 105 | /* Wait for parent to signal for us to go */ |
| 106 | if (atomicio(read, box->child_sock, &whatever, 1) != 1) |
| 107 | fatal("%s: read: %s", __func__, strerror(errno)); |
| 108 | debug3("%s: started", __func__); |
| 109 | close(box->child_sock); |
| 110 | } |
| 111 | |
| 112 | static void |
| 113 | ssh_sandbox_parent(struct ssh_sandbox *box, pid_t child_pid, |
Damien Miller | 35e4819 | 2011-08-06 06:16:23 +1000 | [diff] [blame] | 114 | const struct sandbox_policy *allowed_syscalls) |
Damien Miller | 69ff1df | 2011-06-23 08:30:03 +1000 | [diff] [blame] | 115 | { |
| 116 | int dev_systrace, i, j, found; |
| 117 | char whatever = 0; |
Damien Miller | 35e4819 | 2011-08-06 06:16:23 +1000 | [diff] [blame] | 118 | struct systrace_policy policy; |
Damien Miller | 69ff1df | 2011-06-23 08:30:03 +1000 | [diff] [blame] | 119 | |
| 120 | debug3("%s: wait for child %ld", __func__, (long)child_pid); |
| 121 | box->child_pid = child_pid; |
| 122 | close(box->child_sock); |
| 123 | /* Wait for child to signal that it is ready */ |
| 124 | if (atomicio(read, box->parent_sock, &whatever, 1) != 1) |
| 125 | fatal("%s: read: %s", __func__, strerror(errno)); |
| 126 | debug3("%s: child %ld ready", __func__, (long)child_pid); |
| 127 | |
| 128 | /* Set up systracing of child */ |
| 129 | if ((dev_systrace = open("/dev/systrace", O_RDONLY)) == -1) |
| 130 | fatal("%s: open(\"/dev/systrace\"): %s", __func__, |
| 131 | strerror(errno)); |
| 132 | if (ioctl(dev_systrace, STRIOCCLONE, &box->systrace_fd) == -1) |
| 133 | fatal("%s: ioctl(STRIOCCLONE, %d): %s", __func__, |
| 134 | dev_systrace, strerror(errno)); |
| 135 | close(dev_systrace); |
| 136 | debug3("%s: systrace attach, fd=%d", __func__, box->systrace_fd); |
| 137 | if (ioctl(box->systrace_fd, STRIOCATTACH, &child_pid) == -1) |
| 138 | fatal("%s: ioctl(%d, STRIOCATTACH, %d): %s", __func__, |
| 139 | box->systrace_fd, child_pid, strerror(errno)); |
| 140 | |
| 141 | /* Allocate and assign policy */ |
Damien Miller | 35e4819 | 2011-08-06 06:16:23 +1000 | [diff] [blame] | 142 | bzero(&policy, sizeof(policy)); |
| 143 | policy.strp_op = SYSTR_POLICY_NEW; |
| 144 | policy.strp_maxents = SYS_MAXSYSCALL; |
| 145 | if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1) |
Damien Miller | 69ff1df | 2011-06-23 08:30:03 +1000 | [diff] [blame] | 146 | fatal("%s: ioctl(%d, STRIOCPOLICY (new)): %s", __func__, |
| 147 | box->systrace_fd, strerror(errno)); |
| 148 | |
Damien Miller | 35e4819 | 2011-08-06 06:16:23 +1000 | [diff] [blame] | 149 | policy.strp_op = SYSTR_POLICY_ASSIGN; |
| 150 | policy.strp_pid = box->child_pid; |
| 151 | if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1) |
Damien Miller | 69ff1df | 2011-06-23 08:30:03 +1000 | [diff] [blame] | 152 | fatal("%s: ioctl(%d, STRIOCPOLICY (assign)): %s", |
| 153 | __func__, box->systrace_fd, strerror(errno)); |
| 154 | |
| 155 | /* Set per-syscall policy */ |
| 156 | for (i = 0; i < SYS_MAXSYSCALL; i++) { |
Damien Miller | 35e4819 | 2011-08-06 06:16:23 +1000 | [diff] [blame] | 157 | found = 0; |
| 158 | for (j = 0; allowed_syscalls[j].syscall != -1; j++) { |
| 159 | if (allowed_syscalls[j].syscall == i) { |
Damien Miller | 69ff1df | 2011-06-23 08:30:03 +1000 | [diff] [blame] | 160 | found = 1; |
Damien Miller | 35e4819 | 2011-08-06 06:16:23 +1000 | [diff] [blame] | 161 | break; |
| 162 | } |
Damien Miller | 69ff1df | 2011-06-23 08:30:03 +1000 | [diff] [blame] | 163 | } |
Damien Miller | 35e4819 | 2011-08-06 06:16:23 +1000 | [diff] [blame] | 164 | policy.strp_op = SYSTR_POLICY_MODIFY; |
| 165 | policy.strp_code = i; |
| 166 | policy.strp_policy = found ? |
| 167 | allowed_syscalls[j].action : SYSTR_POLICY_KILL; |
Damien Miller | 69ff1df | 2011-06-23 08:30:03 +1000 | [diff] [blame] | 168 | if (found) |
| 169 | debug3("%s: policy: enable syscall %d", __func__, i); |
Damien Miller | 35e4819 | 2011-08-06 06:16:23 +1000 | [diff] [blame] | 170 | if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1) |
Damien Miller | 69ff1df | 2011-06-23 08:30:03 +1000 | [diff] [blame] | 171 | fatal("%s: ioctl(%d, STRIOCPOLICY (modify)): %s", |
| 172 | __func__, box->systrace_fd, strerror(errno)); |
| 173 | } |
| 174 | |
| 175 | /* Signal the child to start running */ |
| 176 | debug3("%s: start child %ld", __func__, (long)child_pid); |
| 177 | if (atomicio(vwrite, box->parent_sock, &whatever, 1) != 1) |
| 178 | fatal("%s: write: %s", __func__, strerror(errno)); |
| 179 | close(box->parent_sock); |
| 180 | } |
| 181 | |
| 182 | void |
| 183 | ssh_sandbox_parent_finish(struct ssh_sandbox *box) |
| 184 | { |
| 185 | /* Closing this before the child exits will terminate it */ |
| 186 | close(box->systrace_fd); |
| 187 | |
| 188 | free(box); |
| 189 | debug3("%s: finished", __func__); |
| 190 | } |
| 191 | |
| 192 | void |
| 193 | ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid) |
| 194 | { |
| 195 | ssh_sandbox_parent(box, child_pid, preauth_policy); |
| 196 | } |
| 197 | |
| 198 | #endif /* SANDBOX_SYSTRACE */ |