Annotation of src/usr.bin/ssh/sandbox-systrace.c, Revision 1.10
1.10 ! deraadt 1: /* $OpenBSD: sandbox-systrace.c,v 1.9 2014/01/31 16:39:19 tedu 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/param.h>
20: #include <sys/ioctl.h>
21: #include <sys/syscall.h>
22: #include <sys/socket.h>
1.6 markus 23: #include <sys/wait.h>
1.1 djm 24:
25: #include <dev/systrace.h>
26:
27: #include <errno.h>
28: #include <fcntl.h>
29: #include <limits.h>
1.6 markus 30: #include <signal.h>
1.1 djm 31: #include <stdarg.h>
32: #include <stdio.h>
33: #include <stdlib.h>
34: #include <string.h>
35: #include <unistd.h>
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_open, SYSTR_POLICY_NEVER },
50:
51: { SYS___sysctl, SYSTR_POLICY_PERMIT },
52: { SYS_close, SYSTR_POLICY_PERMIT },
53: { SYS_exit, SYSTR_POLICY_PERMIT },
54: { SYS_getpid, SYSTR_POLICY_PERMIT },
1.10 ! deraadt 55: { SYS_getentropy, SYSTR_POLICY_PERMIT },
1.4 djm 56: { SYS_gettimeofday, SYSTR_POLICY_PERMIT },
1.7 dtucker 57: { SYS_clock_gettime, SYSTR_POLICY_PERMIT },
1.4 djm 58: { SYS_madvise, SYSTR_POLICY_PERMIT },
59: { SYS_mmap, SYSTR_POLICY_PERMIT },
60: { SYS_mprotect, SYSTR_POLICY_PERMIT },
1.5 dtucker 61: { SYS_mquery, SYSTR_POLICY_PERMIT },
1.4 djm 62: { SYS_poll, SYSTR_POLICY_PERMIT },
63: { SYS_munmap, SYSTR_POLICY_PERMIT },
64: { SYS_read, SYSTR_POLICY_PERMIT },
65: { SYS_select, SYSTR_POLICY_PERMIT },
1.8 djm 66: { SYS_shutdown, SYSTR_POLICY_PERMIT },
1.4 djm 67: { SYS_sigprocmask, SYSTR_POLICY_PERMIT },
68: { SYS_write, SYSTR_POLICY_PERMIT },
69: { -1, -1 }
1.1 djm 70: };
71:
72: struct ssh_sandbox {
73: int systrace_fd;
74: pid_t child_pid;
1.6 markus 75: void (*osigchld)(int);
1.1 djm 76: };
77:
78: struct ssh_sandbox *
79: ssh_sandbox_init(void)
80: {
81: struct ssh_sandbox *box;
82:
83: debug3("%s: preparing systrace sandbox", __func__);
84: box = xcalloc(1, sizeof(*box));
85: box->systrace_fd = -1;
86: box->child_pid = 0;
1.6 markus 87: box->osigchld = signal(SIGCHLD, SIG_IGN);
1.1 djm 88:
89: return box;
90: }
91:
92: void
93: ssh_sandbox_child(struct ssh_sandbox *box)
94: {
95: debug3("%s: ready", __func__);
1.6 markus 96: signal(SIGCHLD, box->osigchld);
97: if (kill(getpid(), SIGSTOP) != 0)
98: fatal("%s: kill(%d, SIGSTOP)", __func__, getpid());
1.1 djm 99: debug3("%s: started", __func__);
100: }
101:
102: static void
103: ssh_sandbox_parent(struct ssh_sandbox *box, pid_t child_pid,
1.4 djm 104: const struct sandbox_policy *allowed_syscalls)
1.1 djm 105: {
1.6 markus 106: int dev_systrace, i, j, found, status;
107: pid_t pid;
1.4 djm 108: struct systrace_policy policy;
1.1 djm 109:
1.6 markus 110: /* Wait for the child to send itself a SIGSTOP */
1.1 djm 111: debug3("%s: wait for child %ld", __func__, (long)child_pid);
1.6 markus 112: do {
113: pid = waitpid(child_pid, &status, WUNTRACED);
114: } while (pid == -1 && errno == EINTR);
115: signal(SIGCHLD, box->osigchld);
116: if (!WIFSTOPPED(status)) {
117: if (WIFSIGNALED(status))
118: fatal("%s: child terminated with signal %d",
119: __func__, WTERMSIG(status));
120: if (WIFEXITED(status))
121: fatal("%s: child exited with status %d",
122: __func__, WEXITSTATUS(status));
123: fatal("%s: child not stopped", __func__);
124: }
125: debug3("%s: child %ld stopped", __func__, (long)child_pid);
1.1 djm 126: box->child_pid = 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 */
1.9 tedu 142: memset(&policy, 0, sizeof(policy));
1.4 djm 143: policy.strp_op = SYSTR_POLICY_NEW;
144: policy.strp_maxents = SYS_MAXSYSCALL;
145: if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
1.1 djm 146: fatal("%s: ioctl(%d, STRIOCPOLICY (new)): %s", __func__,
147: box->systrace_fd, strerror(errno));
148:
1.4 djm 149: policy.strp_op = SYSTR_POLICY_ASSIGN;
150: policy.strp_pid = box->child_pid;
151: if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
1.1 djm 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++) {
1.4 djm 157: found = 0;
158: for (j = 0; allowed_syscalls[j].syscall != -1; j++) {
159: if (allowed_syscalls[j].syscall == i) {
1.1 djm 160: found = 1;
1.4 djm 161: break;
162: }
1.1 djm 163: }
1.4 djm 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;
1.1 djm 168: if (found)
169: debug3("%s: policy: enable syscall %d", __func__, i);
1.4 djm 170: if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
1.1 djm 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);
1.6 markus 177: if (kill(box->child_pid, SIGCONT) != 0)
178: fatal("%s: kill(%d, SIGCONT)", __func__, box->child_pid);
1.1 djm 179: }
180:
181: void
182: ssh_sandbox_parent_finish(struct ssh_sandbox *box)
183: {
184: /* Closing this before the child exits will terminate it */
185: close(box->systrace_fd);
186:
187: free(box);
188: debug3("%s: finished", __func__);
189: }
190:
191: void
192: ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid)
193: {
194: ssh_sandbox_parent(box, child_pid, preauth_policy);
195: }
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