Annotation of src/usr.bin/ssh/sandbox-systrace.c, Revision 1.18
1.18 ! deraadt 1: /* $OpenBSD: sandbox-systrace.c,v 1.17 2015/07/27 16:29:23 guenther Exp $ */
1.1 djm 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 <sys/types.h>
19: #include <sys/ioctl.h>
20: #include <sys/syscall.h>
21: #include <sys/socket.h>
1.6 markus 22: #include <sys/wait.h>
1.1 djm 23:
24: #include <dev/systrace.h>
25:
26: #include <errno.h>
27: #include <fcntl.h>
28: #include <limits.h>
1.6 markus 29: #include <signal.h>
1.1 djm 30: #include <stdarg.h>
31: #include <stdio.h>
32: #include <stdlib.h>
33: #include <string.h>
34: #include <unistd.h>
1.14 deraadt 35: #include <limits.h>
1.1 djm 36:
37: #include "atomicio.h"
38: #include "log.h"
1.3 djm 39: #include "ssh-sandbox.h"
1.1 djm 40: #include "xmalloc.h"
41:
1.4 djm 42: struct sandbox_policy {
43: int syscall;
44: int action;
45: };
46:
47: /* Permitted syscalls in preauth. Unlisted syscalls get SYSTR_POLICY_KILL */
48: static const struct sandbox_policy preauth_policy[] = {
49: { SYS_exit, SYSTR_POLICY_PERMIT },
1.18 ! deraadt 50: #ifdef SYS_kbind
! 51: { SYS_kbind, SYSTR_POLICY_PERMIT },
! 52: #endif
! 53:
1.4 djm 54: { SYS_getpid, SYSTR_POLICY_PERMIT },
1.16 djm 55: { SYS_getpgid, SYSTR_POLICY_PERMIT },
1.18 ! deraadt 56: { SYS_clock_gettime, SYSTR_POLICY_PERMIT },
1.4 djm 57: { SYS_gettimeofday, SYSTR_POLICY_PERMIT },
1.18 ! deraadt 58: { SYS_sigprocmask, SYSTR_POLICY_PERMIT },
! 59:
! 60: { SYS_getentropy, SYSTR_POLICY_PERMIT },
! 61:
! 62: { SYS_sendsyslog, SYSTR_POLICY_PERMIT },
! 63:
1.4 djm 64: { SYS_madvise, SYSTR_POLICY_PERMIT },
65: { SYS_mmap, SYSTR_POLICY_PERMIT },
66: { SYS_mprotect, SYSTR_POLICY_PERMIT },
1.5 dtucker 67: { SYS_mquery, SYSTR_POLICY_PERMIT },
1.15 deraadt 68: { SYS_munmap, SYSTR_POLICY_PERMIT },
1.18 ! deraadt 69:
1.4 djm 70: { SYS_poll, SYSTR_POLICY_PERMIT },
1.18 ! deraadt 71: { SYS_select, SYSTR_POLICY_PERMIT },
1.4 djm 72: { SYS_read, SYSTR_POLICY_PERMIT },
1.18 ! deraadt 73: { SYS_write, SYSTR_POLICY_PERMIT },
1.8 djm 74: { SYS_shutdown, SYSTR_POLICY_PERMIT },
1.18 ! deraadt 75: { SYS_close, SYSTR_POLICY_PERMIT },
! 76:
! 77: { SYS_open, SYSTR_POLICY_NEVER },
! 78:
1.4 djm 79: { -1, -1 }
1.1 djm 80: };
81:
82: struct ssh_sandbox {
83: int systrace_fd;
84: pid_t child_pid;
1.6 markus 85: void (*osigchld)(int);
1.1 djm 86: };
87:
88: struct ssh_sandbox *
89: ssh_sandbox_init(void)
90: {
91: struct ssh_sandbox *box;
92:
93: debug3("%s: preparing systrace sandbox", __func__);
94: box = xcalloc(1, sizeof(*box));
95: box->systrace_fd = -1;
96: box->child_pid = 0;
1.6 markus 97: box->osigchld = signal(SIGCHLD, SIG_IGN);
1.1 djm 98:
99: return box;
100: }
101:
102: void
103: ssh_sandbox_child(struct ssh_sandbox *box)
104: {
105: debug3("%s: ready", __func__);
1.6 markus 106: signal(SIGCHLD, box->osigchld);
107: if (kill(getpid(), SIGSTOP) != 0)
108: fatal("%s: kill(%d, SIGSTOP)", __func__, getpid());
1.1 djm 109: debug3("%s: started", __func__);
110: }
111:
112: static void
113: ssh_sandbox_parent(struct ssh_sandbox *box, pid_t child_pid,
1.4 djm 114: const struct sandbox_policy *allowed_syscalls)
1.1 djm 115: {
1.6 markus 116: int dev_systrace, i, j, found, status;
117: pid_t pid;
1.4 djm 118: struct systrace_policy policy;
1.1 djm 119:
1.6 markus 120: /* Wait for the child to send itself a SIGSTOP */
1.1 djm 121: debug3("%s: wait for child %ld", __func__, (long)child_pid);
1.6 markus 122: do {
123: pid = waitpid(child_pid, &status, WUNTRACED);
124: } while (pid == -1 && errno == EINTR);
125: signal(SIGCHLD, box->osigchld);
126: if (!WIFSTOPPED(status)) {
127: if (WIFSIGNALED(status))
128: fatal("%s: child terminated with signal %d",
129: __func__, WTERMSIG(status));
130: if (WIFEXITED(status))
131: fatal("%s: child exited with status %d",
132: __func__, WEXITSTATUS(status));
133: fatal("%s: child not stopped", __func__);
134: }
135: debug3("%s: child %ld stopped", __func__, (long)child_pid);
1.1 djm 136: box->child_pid = child_pid;
137:
138: /* Set up systracing of child */
139: if ((dev_systrace = open("/dev/systrace", O_RDONLY)) == -1)
140: fatal("%s: open(\"/dev/systrace\"): %s", __func__,
141: strerror(errno));
142: if (ioctl(dev_systrace, STRIOCCLONE, &box->systrace_fd) == -1)
143: fatal("%s: ioctl(STRIOCCLONE, %d): %s", __func__,
144: dev_systrace, strerror(errno));
145: close(dev_systrace);
146: debug3("%s: systrace attach, fd=%d", __func__, box->systrace_fd);
147: if (ioctl(box->systrace_fd, STRIOCATTACH, &child_pid) == -1)
148: fatal("%s: ioctl(%d, STRIOCATTACH, %d): %s", __func__,
149: box->systrace_fd, child_pid, strerror(errno));
150:
151: /* Allocate and assign policy */
1.9 tedu 152: memset(&policy, 0, sizeof(policy));
1.4 djm 153: policy.strp_op = SYSTR_POLICY_NEW;
154: policy.strp_maxents = SYS_MAXSYSCALL;
155: if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
1.1 djm 156: fatal("%s: ioctl(%d, STRIOCPOLICY (new)): %s", __func__,
157: box->systrace_fd, strerror(errno));
158:
1.4 djm 159: policy.strp_op = SYSTR_POLICY_ASSIGN;
160: policy.strp_pid = box->child_pid;
161: if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
1.1 djm 162: fatal("%s: ioctl(%d, STRIOCPOLICY (assign)): %s",
163: __func__, box->systrace_fd, strerror(errno));
164:
165: /* Set per-syscall policy */
166: for (i = 0; i < SYS_MAXSYSCALL; i++) {
1.4 djm 167: found = 0;
168: for (j = 0; allowed_syscalls[j].syscall != -1; j++) {
169: if (allowed_syscalls[j].syscall == i) {
1.1 djm 170: found = 1;
1.4 djm 171: break;
172: }
1.1 djm 173: }
1.4 djm 174: policy.strp_op = SYSTR_POLICY_MODIFY;
175: policy.strp_code = i;
176: policy.strp_policy = found ?
177: allowed_syscalls[j].action : SYSTR_POLICY_KILL;
1.1 djm 178: if (found)
179: debug3("%s: policy: enable syscall %d", __func__, i);
1.4 djm 180: if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
1.1 djm 181: fatal("%s: ioctl(%d, STRIOCPOLICY (modify)): %s",
182: __func__, box->systrace_fd, strerror(errno));
183: }
184:
185: /* Signal the child to start running */
186: debug3("%s: start child %ld", __func__, (long)child_pid);
1.6 markus 187: if (kill(box->child_pid, SIGCONT) != 0)
188: fatal("%s: kill(%d, SIGCONT)", __func__, box->child_pid);
1.1 djm 189: }
190:
191: void
192: ssh_sandbox_parent_finish(struct ssh_sandbox *box)
193: {
194: /* Closing this before the child exits will terminate it */
195: close(box->systrace_fd);
196:
197: free(box);
198: debug3("%s: finished", __func__);
199: }
200:
201: void
202: ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid)
203: {
204: ssh_sandbox_parent(box, child_pid, preauth_policy);
205: }
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