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
|
#define _GNU_SOURCE
#include <sched.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/stat.h>
#include <limits.h>
#include <sys/types.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <string.h>
static const char *_max_user_namespaces = "/proc/sys/user/max_user_namespaces";
static const char *_unprivileged_user_namespaces = "/proc/sys/kernel/unprivileged_userns_clone";
static int
syscall_setresuid (uid_t ruid, uid_t euid, uid_t suid)
{
return (int) syscall (__NR_setresuid, ruid, euid, suid);
}
static int
syscall_setresgid (gid_t rgid, gid_t egid, gid_t sgid)
{
return (int) syscall (__NR_setresgid, rgid, egid, sgid);
}
static int
syscall_clone (unsigned long flags, void *child_stack)
{
return (int) syscall (__NR_clone, flags, child_stack);
}
static char **
get_cmd_line_args (pid_t pid)
{
int fd;
char path[PATH_MAX];
char *buffer;
size_t allocated;
size_t used = 0;
int ret;
int i, argc = 0;
char **argv;
sprintf (path, "/proc/%d/cmdline", pid);
fd = open (path, O_RDONLY);
if (fd < 0)
return NULL;
allocated = 512;
buffer = malloc (allocated);
if (buffer == NULL)
return NULL;
for (;;)
{
do
ret = read (fd, buffer + used, allocated - used);
while (ret < 0 && errno == EINTR);
if (ret < 0)
return NULL;
if (ret == 0)
break;
used += ret;
if (allocated == used)
{
allocated += 512;
char *tmp = realloc (buffer, allocated);
if (buffer == NULL) {
free(buffer);
return NULL;
}
buffer=tmp;
}
}
close (fd);
for (i = 0; i < used; i++)
if (buffer[i] == '\0')
argc++;
if (argc == 0)
return NULL;
argv = malloc (sizeof (char *) * (argc + 1));
if (argv == NULL)
return NULL;
argc = 0;
argv[argc++] = buffer;
for (i = 0; i < used - 1; i++)
if (buffer[i] == '\0')
argv[argc++] = buffer + i + 1;
argv[argc] = NULL;
return argv;
}
int
reexec_userns_join (int userns, int mountns)
{
pid_t ppid = getpid ();
char uid[16];
char **argv;
int pid;
sprintf (uid, "%d", geteuid ());
argv = get_cmd_line_args (ppid);
if (argv == NULL)
{
fprintf (stderr, "cannot read argv: %s\n", strerror (errno));
_exit (EXIT_FAILURE);
}
pid = fork ();
if (pid < 0)
fprintf (stderr, "cannot fork: %s\n", strerror (errno));
if (pid)
return pid;
setenv ("_LIBPOD_USERNS_CONFIGURED", "init", 1);
setenv ("_LIBPOD_ROOTLESS_UID", uid, 1);
if (setns (userns, 0) < 0)
{
fprintf (stderr, "cannot setns: %s\n", strerror (errno));
_exit (EXIT_FAILURE);
}
close (userns);
if (mountns >= 0 && setns (mountns, 0) < 0)
{
fprintf (stderr, "cannot setns: %s\n", strerror (errno));
_exit (EXIT_FAILURE);
}
close (userns);
if (syscall_setresgid (0, 0, 0) < 0)
{
fprintf (stderr, "cannot setresgid: %s\n", strerror (errno));
_exit (EXIT_FAILURE);
}
if (syscall_setresuid (0, 0, 0) < 0)
{
fprintf (stderr, "cannot setresuid: %s\n", strerror (errno));
_exit (EXIT_FAILURE);
}
execvp (argv[0], argv);
_exit (EXIT_FAILURE);
}
static void
check_proc_sys_userns_file (const char *path)
{
FILE *fp;
fp = fopen (path, "r");
if (fp)
{
char buf[32];
size_t n_read = fread (buf, 1, sizeof(buf) - 1, fp);
if (n_read > 0)
{
buf[n_read] = '\0';
if (strtol (buf, NULL, 10) == 0)
fprintf (stderr, "user namespaces are not enabled in %s\n", path);
}
fclose (fp);
}
}
int
reexec_in_user_namespace (int ready)
{
int ret;
pid_t pid;
char b;
pid_t ppid = getpid ();
char **argv;
char uid[16];
sprintf (uid, "%d", geteuid ());
pid = syscall_clone (CLONE_NEWUSER|CLONE_NEWNS|SIGCHLD, NULL);
if (pid < 0)
{
FILE *fp;
fprintf (stderr, "cannot clone: %s\n", strerror (errno));
check_proc_sys_userns_file (_max_user_namespaces);
check_proc_sys_userns_file (_unprivileged_user_namespaces);
}
if (pid)
return pid;
argv = get_cmd_line_args (ppid);
if (argv == NULL)
{
fprintf (stderr, "cannot read argv: %s\n", strerror (errno));
_exit (EXIT_FAILURE);
}
setenv ("_LIBPOD_USERNS_CONFIGURED", "init", 1);
setenv ("_LIBPOD_ROOTLESS_UID", uid, 1);
do
ret = read (ready, &b, 1) < 0;
while (ret < 0 && errno == EINTR);
if (ret < 0)
{
fprintf (stderr, "cannot read from sync pipe: %s\n", strerror (errno));
_exit (EXIT_FAILURE);
}
close (ready);
if (syscall_setresgid (0, 0, 0) < 0)
{
fprintf (stderr, "cannot setresgid: %s\n", strerror (errno));
_exit (EXIT_FAILURE);
}
if (syscall_setresuid (0, 0, 0) < 0)
{
fprintf (stderr, "cannot setresuid: %s\n", strerror (errno));
_exit (EXIT_FAILURE);
}
execvp (argv[0], argv);
_exit (EXIT_FAILURE);
}
int
reexec_in_user_namespace_wait (int pid)
{
pid_t p;
int status;
do
p = waitpid (pid, &status, 0);
while (p < 0 && errno == EINTR);
if (p < 0)
return -1;
if (WIFEXITED (status))
return WEXITSTATUS (status);
if (WIFSIGNALED (status))
return 128 + WTERMSIG (status);
return -1;
}
|
