Annotation of src/usr.bin/ssh/sandbox-systrace.c, Revision 1.5
1.5 ! dtucker 1: /* $OpenBSD: sandbox-systrace.c,v 1.4 2011/07/29 14:42:45 djm 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>
23:
24: #include <dev/systrace.h>
25:
26: #include <errno.h>
27: #include <fcntl.h>
28: #include <limits.h>
29: #include <stdarg.h>
30: #include <stdio.h>
31: #include <stdlib.h>
32: #include <string.h>
33: #include <unistd.h>
34:
35: #include "atomicio.h"
36: #include "log.h"
1.3 djm 37: #include "ssh-sandbox.h"
1.1 djm 38: #include "xmalloc.h"
39:
1.4 djm 40: struct sandbox_policy {
41: int syscall;
42: int action;
43: };
44:
45: /* Permitted syscalls in preauth. Unlisted syscalls get SYSTR_POLICY_KILL */
46: static const struct sandbox_policy preauth_policy[] = {
47: { SYS_open, SYSTR_POLICY_NEVER },
48:
49: { SYS___sysctl, SYSTR_POLICY_PERMIT },
50: { SYS_close, SYSTR_POLICY_PERMIT },
51: { SYS_exit, SYSTR_POLICY_PERMIT },
52: { SYS_getpid, SYSTR_POLICY_PERMIT },
53: { SYS_gettimeofday, SYSTR_POLICY_PERMIT },
54: { SYS_madvise, SYSTR_POLICY_PERMIT },
55: { SYS_mmap, SYSTR_POLICY_PERMIT },
56: { SYS_mprotect, SYSTR_POLICY_PERMIT },
1.5 ! dtucker 57: { SYS_mquery, SYSTR_POLICY_PERMIT },
1.4 djm 58: { SYS_poll, SYSTR_POLICY_PERMIT },
59: { SYS_munmap, SYSTR_POLICY_PERMIT },
60: { SYS_read, SYSTR_POLICY_PERMIT },
61: { SYS_select, SYSTR_POLICY_PERMIT },
62: { SYS_sigprocmask, SYSTR_POLICY_PERMIT },
63: { SYS_write, SYSTR_POLICY_PERMIT },
64: { -1, -1 }
1.1 djm 65: };
66:
67: struct ssh_sandbox {
68: int child_sock;
69: int parent_sock;
70: int systrace_fd;
71: pid_t child_pid;
72: };
73:
74: struct ssh_sandbox *
75: ssh_sandbox_init(void)
76: {
77: struct ssh_sandbox *box;
78: int s[2];
79:
80: debug3("%s: preparing systrace sandbox", __func__);
81: box = xcalloc(1, sizeof(*box));
82: if (socketpair(AF_UNIX, SOCK_STREAM, 0, s) == -1)
83: fatal("%s: socketpair: %s", __func__, strerror(errno));
84: box->child_sock = s[0];
85: box->parent_sock = s[1];
86: box->systrace_fd = -1;
87: box->child_pid = 0;
88:
89: return box;
90: }
91:
92: void
93: ssh_sandbox_child(struct ssh_sandbox *box)
94: {
95: char whatever = 0;
96:
97: close(box->parent_sock);
98: /* Signal parent that we are ready */
99: debug3("%s: ready", __func__);
100: if (atomicio(vwrite, box->child_sock, &whatever, 1) != 1)
101: fatal("%s: write: %s", __func__, strerror(errno));
102: /* Wait for parent to signal for us to go */
103: if (atomicio(read, box->child_sock, &whatever, 1) != 1)
104: fatal("%s: read: %s", __func__, strerror(errno));
105: debug3("%s: started", __func__);
106: close(box->child_sock);
107: }
108:
109: static void
110: ssh_sandbox_parent(struct ssh_sandbox *box, pid_t child_pid,
1.4 djm 111: const struct sandbox_policy *allowed_syscalls)
1.1 djm 112: {
113: int dev_systrace, i, j, found;
114: char whatever = 0;
1.4 djm 115: struct systrace_policy policy;
1.1 djm 116:
117: debug3("%s: wait for child %ld", __func__, (long)child_pid);
118: box->child_pid = child_pid;
119: close(box->child_sock);
120: /* Wait for child to signal that it is ready */
121: if (atomicio(read, box->parent_sock, &whatever, 1) != 1)
122: fatal("%s: read: %s", __func__, strerror(errno));
123: debug3("%s: child %ld ready", __func__, (long)child_pid);
124:
125: /* Set up systracing of child */
126: if ((dev_systrace = open("/dev/systrace", O_RDONLY)) == -1)
127: fatal("%s: open(\"/dev/systrace\"): %s", __func__,
128: strerror(errno));
129: if (ioctl(dev_systrace, STRIOCCLONE, &box->systrace_fd) == -1)
130: fatal("%s: ioctl(STRIOCCLONE, %d): %s", __func__,
131: dev_systrace, strerror(errno));
132: close(dev_systrace);
133: debug3("%s: systrace attach, fd=%d", __func__, box->systrace_fd);
134: if (ioctl(box->systrace_fd, STRIOCATTACH, &child_pid) == -1)
135: fatal("%s: ioctl(%d, STRIOCATTACH, %d): %s", __func__,
136: box->systrace_fd, child_pid, strerror(errno));
137:
138: /* Allocate and assign policy */
1.4 djm 139: bzero(&policy, sizeof(policy));
140: policy.strp_op = SYSTR_POLICY_NEW;
141: policy.strp_maxents = SYS_MAXSYSCALL;
142: if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
1.1 djm 143: fatal("%s: ioctl(%d, STRIOCPOLICY (new)): %s", __func__,
144: box->systrace_fd, strerror(errno));
145:
1.4 djm 146: policy.strp_op = SYSTR_POLICY_ASSIGN;
147: policy.strp_pid = box->child_pid;
148: if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
1.1 djm 149: fatal("%s: ioctl(%d, STRIOCPOLICY (assign)): %s",
150: __func__, box->systrace_fd, strerror(errno));
151:
152: /* Set per-syscall policy */
153: for (i = 0; i < SYS_MAXSYSCALL; i++) {
1.4 djm 154: found = 0;
155: for (j = 0; allowed_syscalls[j].syscall != -1; j++) {
156: if (allowed_syscalls[j].syscall == i) {
1.1 djm 157: found = 1;
1.4 djm 158: break;
159: }
1.1 djm 160: }
1.4 djm 161: policy.strp_op = SYSTR_POLICY_MODIFY;
162: policy.strp_code = i;
163: policy.strp_policy = found ?
164: allowed_syscalls[j].action : SYSTR_POLICY_KILL;
1.1 djm 165: if (found)
166: debug3("%s: policy: enable syscall %d", __func__, i);
1.4 djm 167: if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
1.1 djm 168: fatal("%s: ioctl(%d, STRIOCPOLICY (modify)): %s",
169: __func__, box->systrace_fd, strerror(errno));
170: }
171:
172: /* Signal the child to start running */
173: debug3("%s: start child %ld", __func__, (long)child_pid);
174: if (atomicio(vwrite, box->parent_sock, &whatever, 1) != 1)
175: fatal("%s: write: %s", __func__, strerror(errno));
176: close(box->parent_sock);
177: }
178:
179: void
180: ssh_sandbox_parent_finish(struct ssh_sandbox *box)
181: {
182: /* Closing this before the child exits will terminate it */
183: close(box->systrace_fd);
184:
185: free(box);
186: debug3("%s: finished", __func__);
187: }
188:
189: void
190: ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid)
191: {
192: ssh_sandbox_parent(box, child_pid, preauth_policy);
193: }
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