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
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
|
/*
* Copyright (C) 2014-2020 Firejail Authors
*
* This file is part of firejail project
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "firejail.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <net/if.h>
#include <stdarg.h>
#include <sys/wait.h>
#include "../include/seccomp.h"
#include <fcntl.h>
#ifndef O_PATH
#define O_PATH 010000000
#endif
static int __attribute__((noreturn)) sbox_do_exec_v(unsigned filtermask, char * const arg[]) {
// build a new, clean environment
int env_index = 0;
char *new_environment[256] = { NULL };
// preserve firejail-specific env vars
char *cl = getenv("FIREJAIL_FILE_COPY_LIMIT");
if (cl) {
if (asprintf(&new_environment[env_index++], "FIREJAIL_FILE_COPY_LIMIT=%s", cl) == -1)
errExit("asprintf");
}
if (arg_quiet) // --quiet is passed as an environment variable
new_environment[env_index++] = "FIREJAIL_QUIET=yes";
if (arg_debug) // --debug is passed as an environment variable
new_environment[env_index++] = "FIREJAIL_DEBUG=yes";
if (cfg.seccomp_error_action)
if (asprintf(&new_environment[env_index++], "FIREJAIL_SECCOMP_ERROR_ACTION=%s", cfg.seccomp_error_action) == -1)
errExit("asprintf");
if (filtermask & SBOX_STDIN_FROM_FILE) {
int fd;
if((fd = open(SBOX_STDIN_FILE, O_RDONLY)) == -1) {
fprintf(stderr,"Error: cannot open %s\n", SBOX_STDIN_FILE);
exit(1);
}
if (dup2(fd, STDIN_FILENO) == -1)
errExit("dup2");
close(fd);
}
else if ((filtermask & SBOX_ALLOW_STDIN) == 0) {
int fd = open("/dev/null",O_RDWR, 0);
if (fd != -1) {
if (dup2(fd, STDIN_FILENO) == -1)
errExit("dup2");
close(fd);
}
else // the user could run the sandbox without /dev/null
close(STDIN_FILENO);
}
// close all other file descriptors
if ((filtermask & SBOX_KEEP_FDS) == 0) {
int i;
for (i = 3; i < FIREJAIL_MAX_FD; i++)
close(i); // close open files
}
umask(027);
// apply filters
if (filtermask & SBOX_CAPS_NONE) {
caps_drop_all();
} else {
uint64_t set = 0;
if (filtermask & SBOX_CAPS_NETWORK) {
#ifndef HAVE_GCOV // the following filter will prevent GCOV from saving info in .gcda files
set |= ((uint64_t) 1) << CAP_NET_ADMIN;
set |= ((uint64_t) 1) << CAP_NET_RAW;
#endif
}
if (filtermask & SBOX_CAPS_HIDEPID) {
#ifndef HAVE_GCOV // the following filter will prevent GCOV from saving info in .gcda files
set |= ((uint64_t) 1) << CAP_SYS_PTRACE;
set |= ((uint64_t) 1) << CAP_SYS_PACCT;
#endif
}
if (filtermask & SBOX_CAPS_NET_SERVICE) {
#ifndef HAVE_GCOV // the following filter will prevent GCOV from saving info in .gcda files
set |= ((uint64_t) 1) << CAP_NET_BIND_SERVICE;
set |= ((uint64_t) 1) << CAP_NET_BROADCAST;
#endif
}
if (set != 0) { // some SBOX_CAPS_ flag was specified, drop all other capabilities
#ifndef HAVE_GCOV // the following filter will prevent GCOV from saving info in .gcda files
caps_set(set);
#endif
}
}
if (filtermask & SBOX_SECCOMP) {
struct sock_filter filter[] = {
VALIDATE_ARCHITECTURE,
EXAMINE_SYSCALL,
#if defined(__x86_64__)
#define X32_SYSCALL_BIT 0x40000000
// handle X32 ABI
BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, X32_SYSCALL_BIT, 1, 0),
BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, 0, 1, 0),
RETURN_ERRNO(EPERM),
#endif
// syscall list
#ifdef SYS_mount
BLACKLIST(SYS_mount), // mount/unmount filesystems
#endif
#ifdef SYS_umount
BLACKLIST(SYS_umount),
#endif
#ifdef SYS_umount2
BLACKLIST(SYS_umount2),
#endif
#ifdef SYS_ptrace
BLACKLIST(SYS_ptrace), // trace processes
#endif
#ifdef SYS_process_vm_readv
BLACKLIST(SYS_process_vm_readv),
#endif
#ifdef SYS_process_vm_writev
BLACKLIST(SYS_process_vm_writev),
#endif
#ifdef SYS_kexec_file_load
BLACKLIST(SYS_kexec_file_load), // loading a different kernel
#endif
#ifdef SYS_kexec_load
BLACKLIST(SYS_kexec_load),
#endif
#ifdef SYS_name_to_handle_at
BLACKLIST(SYS_name_to_handle_at),
#endif
#ifdef SYS_open_by_handle_at
BLACKLIST(SYS_open_by_handle_at), // open by handle
#endif
#ifdef SYS_init_module
BLACKLIST(SYS_init_module), // kernel module handling
#endif
#ifdef SYS_finit_module // introduced in 2013
BLACKLIST(SYS_finit_module),
#endif
#ifdef SYS_create_module
BLACKLIST(SYS_create_module),
#endif
#ifdef SYS_delete_module
BLACKLIST(SYS_delete_module),
#endif
#ifdef SYS_iopl
BLACKLIST(SYS_iopl), // io permissions
#endif
#ifdef SYS_ioperm
BLACKLIST(SYS_ioperm),
#endif
#ifdef SYS_ioprio_set
BLACKLIST(SYS_ioprio_set),
#endif
#ifdef SYS_ni_syscall // new io permissions call on arm devices
BLACKLIST(SYS_ni_syscall),
#endif
#ifdef SYS_swapon
BLACKLIST(SYS_swapon), // swap on/off
#endif
#ifdef SYS_swapoff
BLACKLIST(SYS_swapoff),
#endif
#ifdef SYS_syslog
BLACKLIST(SYS_syslog), // kernel printk control
#endif
RETURN_ALLOW
};
struct sock_fprog prog = {
.len = (unsigned short)(sizeof(filter) / sizeof(filter[0])),
.filter = filter,
};
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
perror("prctl(NO_NEW_PRIVS)");
}
if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) {
perror("prctl(PR_SET_SECCOMP)");
}
}
if (filtermask & SBOX_ROOT) {
// elevate privileges in order to get grsecurity working
if (setreuid(0, 0))
errExit("setreuid");
if (setregid(0, 0))
errExit("setregid");
}
else if (filtermask & SBOX_USER)
drop_privs(1);
if (arg[0]) { // get rid of scan-build warning
int fd = open(arg[0], O_PATH | O_CLOEXEC);
if (fd == -1) {
if (errno == ENOENT) {
fprintf(stderr, "Error: %s does not exist\n", arg[0]);
exit(1);
} else {
errExit("open");
}
}
struct stat s;
if (fstat(fd, &s) == -1)
errExit("fstat");
if (s.st_uid != 0 && s.st_gid != 0) {
fprintf(stderr, "Error: %s is not owned by root, refusing to execute\n", arg[0]);
exit(1);
}
if (s.st_mode & 00002) {
fprintf(stderr, "Error: %s is world writable, refusing to execute\n", arg[0]);
exit(1);
}
fexecve(fd, arg, new_environment);
} else {
assert(0);
}
perror("fexecve");
_exit(1);
}
int sbox_run(unsigned filtermask, int num, ...) {
va_list valist;
va_start(valist, num);
// build argument list
char **arg = malloc((num + 1) * sizeof(char *));
int i;
for (i = 0; i < num; i++)
arg[i] = va_arg(valist, char *);
arg[i] = NULL;
va_end(valist);
int status = sbox_run_v(filtermask, arg);
free(arg);
return status;
}
int sbox_run_v(unsigned filtermask, char * const arg[]) {
EUID_ROOT();
if (arg_debug) {
printf("sbox run: ");
int i = 0;
while (arg[i]) {
printf("%s ", arg[i]);
i++;
}
printf("\n");
}
// KEEP_FDS only makes sense with sbox_exec_v
assert((filtermask & SBOX_KEEP_FDS) == 0);
pid_t child = fork();
if (child < 0)
errExit("fork");
if (child == 0) {
sbox_do_exec_v(filtermask, arg);
}
int status;
if (waitpid(child, &status, 0) == -1 ) {
errExit("waitpid");
}
if (WIFEXITED(status) && status != 0) {
fprintf(stderr, "Error: failed to run %s\n", arg[0]);
exit(1);
}
return status;
}
void sbox_exec_v(unsigned filtermask, char * const arg[]) {
EUID_ROOT();
if (arg_debug) {
printf("sbox exec: ");
int i = 0;
while (arg[i]) {
printf("%s ", arg[i]);
i++;
}
printf("\n");
}
sbox_do_exec_v(filtermask, arg);
}
|