Annotation of src/usr.bin/ssh/sandbox-systrace.c, Revision 1.4
1.4 ! djm 1: /* $OpenBSD: sandbox-systrace.c,v 1.3 2011/06/23 09:34:13 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 },
! 57: { SYS_poll, SYSTR_POLICY_PERMIT },
! 58: { SYS_munmap, SYSTR_POLICY_PERMIT },
! 59: { SYS_read, SYSTR_POLICY_PERMIT },
! 60: { SYS_select, SYSTR_POLICY_PERMIT },
! 61: { SYS_sigprocmask, SYSTR_POLICY_PERMIT },
! 62: { SYS_write, SYSTR_POLICY_PERMIT },
! 63: { -1, -1 }
1.1 djm 64: };
65:
66: struct ssh_sandbox {
67: int child_sock;
68: int parent_sock;
69: int systrace_fd;
70: pid_t child_pid;
71: };
72:
73: struct ssh_sandbox *
74: ssh_sandbox_init(void)
75: {
76: struct ssh_sandbox *box;
77: int s[2];
78:
79: debug3("%s: preparing systrace sandbox", __func__);
80: box = xcalloc(1, sizeof(*box));
81: if (socketpair(AF_UNIX, SOCK_STREAM, 0, s) == -1)
82: fatal("%s: socketpair: %s", __func__, strerror(errno));
83: box->child_sock = s[0];
84: box->parent_sock = s[1];
85: box->systrace_fd = -1;
86: box->child_pid = 0;
87:
88: return box;
89: }
90:
91: void
92: ssh_sandbox_child(struct ssh_sandbox *box)
93: {
94: char whatever = 0;
95:
96: close(box->parent_sock);
97: /* Signal parent that we are ready */
98: debug3("%s: ready", __func__);
99: if (atomicio(vwrite, box->child_sock, &whatever, 1) != 1)
100: fatal("%s: write: %s", __func__, strerror(errno));
101: /* Wait for parent to signal for us to go */
102: if (atomicio(read, box->child_sock, &whatever, 1) != 1)
103: fatal("%s: read: %s", __func__, strerror(errno));
104: debug3("%s: started", __func__);
105: close(box->child_sock);
106: }
107:
108: static void
109: ssh_sandbox_parent(struct ssh_sandbox *box, pid_t child_pid,
1.4 ! djm 110: const struct sandbox_policy *allowed_syscalls)
1.1 djm 111: {
112: int dev_systrace, i, j, found;
113: char whatever = 0;
1.4 ! djm 114: struct systrace_policy policy;
1.1 djm 115:
116: debug3("%s: wait for child %ld", __func__, (long)child_pid);
117: box->child_pid = child_pid;
118: close(box->child_sock);
119: /* Wait for child to signal that it is ready */
120: if (atomicio(read, box->parent_sock, &whatever, 1) != 1)
121: fatal("%s: read: %s", __func__, strerror(errno));
122: debug3("%s: child %ld ready", __func__, (long)child_pid);
123:
124: /* Set up systracing of child */
125: if ((dev_systrace = open("/dev/systrace", O_RDONLY)) == -1)
126: fatal("%s: open(\"/dev/systrace\"): %s", __func__,
127: strerror(errno));
128: if (ioctl(dev_systrace, STRIOCCLONE, &box->systrace_fd) == -1)
129: fatal("%s: ioctl(STRIOCCLONE, %d): %s", __func__,
130: dev_systrace, strerror(errno));
131: close(dev_systrace);
132: debug3("%s: systrace attach, fd=%d", __func__, box->systrace_fd);
133: if (ioctl(box->systrace_fd, STRIOCATTACH, &child_pid) == -1)
134: fatal("%s: ioctl(%d, STRIOCATTACH, %d): %s", __func__,
135: box->systrace_fd, child_pid, strerror(errno));
136:
137: /* Allocate and assign policy */
1.4 ! djm 138: bzero(&policy, sizeof(policy));
! 139: policy.strp_op = SYSTR_POLICY_NEW;
! 140: policy.strp_maxents = SYS_MAXSYSCALL;
! 141: if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
1.1 djm 142: fatal("%s: ioctl(%d, STRIOCPOLICY (new)): %s", __func__,
143: box->systrace_fd, strerror(errno));
144:
1.4 ! djm 145: policy.strp_op = SYSTR_POLICY_ASSIGN;
! 146: policy.strp_pid = box->child_pid;
! 147: if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
1.1 djm 148: fatal("%s: ioctl(%d, STRIOCPOLICY (assign)): %s",
149: __func__, box->systrace_fd, strerror(errno));
150:
151: /* Set per-syscall policy */
152: for (i = 0; i < SYS_MAXSYSCALL; i++) {
1.4 ! djm 153: found = 0;
! 154: for (j = 0; allowed_syscalls[j].syscall != -1; j++) {
! 155: if (allowed_syscalls[j].syscall == i) {
1.1 djm 156: found = 1;
1.4 ! djm 157: break;
! 158: }
1.1 djm 159: }
1.4 ! djm 160: policy.strp_op = SYSTR_POLICY_MODIFY;
! 161: policy.strp_code = i;
! 162: policy.strp_policy = found ?
! 163: allowed_syscalls[j].action : SYSTR_POLICY_KILL;
1.1 djm 164: if (found)
165: debug3("%s: policy: enable syscall %d", __func__, i);
1.4 ! djm 166: if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
1.1 djm 167: fatal("%s: ioctl(%d, STRIOCPOLICY (modify)): %s",
168: __func__, box->systrace_fd, strerror(errno));
169: }
170:
171: /* Signal the child to start running */
172: debug3("%s: start child %ld", __func__, (long)child_pid);
173: if (atomicio(vwrite, box->parent_sock, &whatever, 1) != 1)
174: fatal("%s: write: %s", __func__, strerror(errno));
175: close(box->parent_sock);
176: }
177:
178: void
179: ssh_sandbox_parent_finish(struct ssh_sandbox *box)
180: {
181: /* Closing this before the child exits will terminate it */
182: close(box->systrace_fd);
183:
184: free(box);
185: debug3("%s: finished", __func__);
186: }
187:
188: void
189: ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid)
190: {
191: ssh_sandbox_parent(box, child_pid, preauth_policy);
192: }
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