1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
| | // SPDX-License-Identifier: AGPL-3.0-or-later
/* PASST - Plug A Simple Socket Transport
* for qemu/UNIX domain socket mode
*
* PASTA - Pack A Subtle Tap Abstraction
* for network namespace/tap device mode
*
* isolation.c - Self isolation helpers
*
* Copyright Red Hat
* Author: Stefano Brivio <sbrivio(a)redhat.com>
* Author: David Gibson <david(a)gibson.dropbear.id.au>
*/
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <inttypes.h>
#include <limits.h>
#include <pwd.h>
#include <sched.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <sys/mount.h>
#include <sys/prctl.h>
#include <sys/socket.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netinet/if_ether.h>
#include <linux/audit.h>
#include <linux/capability.h>
#include <linux/filter.h>
#include <linux/seccomp.h>
#include "util.h"
#include "seccomp.h"
#include "passt.h"
#include "isolation.h"
/**
* drop_caps() - Drop capabilities we might have except for CAP_NET_BIND_SERVICE
*/
void drop_caps(void)
{
int i;
for (i = 0; i < 64; i++) {
if (i == CAP_NET_BIND_SERVICE)
continue;
prctl(PR_CAPBSET_DROP, i, 0, 0, 0);
}
}
/**
* drop_root() - Switch to given UID and GID
*/
void drop_root(uid_t uid, gid_t gid)
{
if (setgroups(0, NULL)) {
/* If we don't start with CAP_SETGID, this will EPERM */
if (errno != EPERM) {
err("Can't drop supplementary groups: %s",
strerror(errno));
exit(EXIT_FAILURE);
}
}
if (!setgid(gid) && !setuid(uid))
return;
err("Can't change user/group, exiting");
exit(EXIT_FAILURE);
}
/**
* sandbox() - Unshare IPC, mount, PID, UTS, and user namespaces, "unmount" root
*
* Return: negative error code on failure, zero on success
*/
int sandbox(struct ctx *c)
{
int flags = CLONE_NEWIPC | CLONE_NEWNS | CLONE_NEWUTS;
if (!c->netns_only) {
if (c->pasta_userns_fd == -1)
flags |= CLONE_NEWUSER;
else
setns(c->pasta_userns_fd, CLONE_NEWUSER);
}
c->pasta_userns_fd = -1;
/* If we run in foreground, we have no chance to actually move to a new
* PID namespace. For passt, use CLONE_NEWPID anyway, in case somebody
* ever gets around seccomp profiles -- there's no harm in passing it.
*/
if (!c->foreground || c->mode == MODE_PASST)
flags |= CLONE_NEWPID;
if (unshare(flags)) {
perror("unshare");
return -errno;
}
if (mount("", "/", "", MS_UNBINDABLE | MS_REC, NULL)) {
perror("mount /");
return -errno;
}
if (mount("", TMPDIR, "tmpfs",
MS_NODEV | MS_NOEXEC | MS_NOSUID | MS_RDONLY,
"nr_inodes=2,nr_blocks=0")) {
perror("mount tmpfs");
return -errno;
}
if (chdir(TMPDIR)) {
perror("chdir");
return -errno;
}
if (syscall(SYS_pivot_root, ".", ".")) {
perror("pivot_root");
return -errno;
}
if (umount2(".", MNT_DETACH | UMOUNT_NOFOLLOW)) {
perror("umount2");
return -errno;
}
drop_caps(); /* Relative to the new user namespace this time. */
return 0;
}
/**
* seccomp() - Set up seccomp filters depending on mode, won't return on failure
* @c: Execution context
*/
void seccomp(const struct ctx *c)
{
struct sock_fprog prog;
if (c->mode == MODE_PASST) {
prog.len = (unsigned short)ARRAY_SIZE(filter_passt);
prog.filter = filter_passt;
} else {
prog.len = (unsigned short)ARRAY_SIZE(filter_pasta);
prog.filter = filter_pasta;
}
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) ||
prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) {
perror("prctl");
exit(EXIT_FAILURE);
}
}
|