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
|
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <fcntl.h>
#include <sys/types.h>
#include <unistd.h>
#include "alloc-util.h"
#include "constants.h"
#include "errno.h"
#include "fd-util.h"
#include "fileio.h"
#include "mkdir.h"
#include "nspawn-setuid.h"
#include "process-util.h"
#include "signal-util.h"
#include "string-util.h"
#include "strv.h"
#include "user-util.h"
static int spawn_getent(const char *database, const char *key, pid_t *rpid) {
int pipe_fds[2], r;
pid_t pid;
assert(database);
assert(key);
assert(rpid);
if (pipe2(pipe_fds, O_CLOEXEC) < 0)
return log_error_errno(errno, "Failed to allocate pipe: %m");
r = safe_fork_full("(getent)",
(int[]) { -EBADF, pipe_fds[1], -EBADF }, NULL, 0,
FORK_RESET_SIGNALS|FORK_CLOSE_ALL_FDS|FORK_DEATHSIG_SIGTERM|FORK_REARRANGE_STDIO|FORK_LOG|FORK_RLIMIT_NOFILE_SAFE,
&pid);
if (r < 0) {
safe_close_pair(pipe_fds);
return r;
}
if (r == 0) {
execle("/usr/bin/getent", "getent", database, key, NULL, &(char*[1]){});
execle("/bin/getent", "getent", database, key, NULL, &(char*[1]){});
_exit(EXIT_FAILURE);
}
pipe_fds[1] = safe_close(pipe_fds[1]);
*rpid = pid;
return pipe_fds[0];
}
int change_uid_gid_raw(
uid_t uid,
gid_t gid,
const gid_t *supplementary_gids,
size_t n_supplementary_gids,
bool chown_stdio) {
int r;
if (!uid_is_valid(uid))
uid = 0;
if (!gid_is_valid(gid))
gid = 0;
if (chown_stdio) {
(void) fchown(STDIN_FILENO, uid, gid);
(void) fchown(STDOUT_FILENO, uid, gid);
(void) fchown(STDERR_FILENO, uid, gid);
}
r = fully_set_uid_gid(uid, gid, supplementary_gids, n_supplementary_gids);
if (r < 0)
return log_error_errno(r, "Changing privileges failed: %m");
return 0;
}
int change_uid_gid(const char *user, bool chown_stdio, char **ret_home) {
char *x, *u, *g, *h;
_cleanup_free_ gid_t *gids = NULL;
_cleanup_free_ char *home = NULL, *line = NULL;
_cleanup_fclose_ FILE *f = NULL;
_cleanup_close_ int fd = -EBADF;
unsigned n_gids = 0;
uid_t uid;
gid_t gid;
pid_t pid;
int r;
assert(ret_home);
if (!user || STR_IN_SET(user, "root", "0")) {
/* Reset everything fully to 0, just in case */
r = reset_uid_gid();
if (r < 0)
return log_error_errno(r, "Failed to become root: %m");
*ret_home = NULL;
return 0;
}
/* First, get user credentials */
fd = spawn_getent("passwd", user, &pid);
if (fd < 0)
return fd;
f = take_fdopen(&fd, "r");
if (!f)
return log_oom();
r = read_line(f, LONG_LINE_MAX, &line);
if (r == 0)
return log_error_errno(SYNTHETIC_ERRNO(ESRCH),
"Failed to resolve user %s.", user);
if (r < 0)
return log_error_errno(r, "Failed to read from getent: %m");
(void) wait_for_terminate_and_check("getent passwd", pid, WAIT_LOG);
x = strchr(line, ':');
if (!x)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"/etc/passwd entry has invalid user field.");
u = strchr(x+1, ':');
if (!u)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"/etc/passwd entry has invalid password field.");
u++;
g = strchr(u, ':');
if (!g)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"/etc/passwd entry has invalid UID field.");
*g = 0;
g++;
x = strchr(g, ':');
if (!x)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"/etc/passwd entry has invalid GID field.");
*x = 0;
h = strchr(x+1, ':');
if (!h)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"/etc/passwd entry has invalid GECOS field.");
h++;
x = strchr(h, ':');
if (!x)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"/etc/passwd entry has invalid home directory field.");
*x = 0;
r = parse_uid(u, &uid);
if (r < 0)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to parse UID of user.");
r = parse_gid(g, &gid);
if (r < 0)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to parse GID of user.");
home = strdup(h);
if (!home)
return log_oom();
f = safe_fclose(f);
line = mfree(line);
/* Second, get group memberships */
fd = spawn_getent("initgroups", user, &pid);
if (fd < 0)
return fd;
f = take_fdopen(&fd, "r");
if (!f)
return log_oom();
r = read_line(f, LONG_LINE_MAX, &line);
if (r == 0)
return log_error_errno(SYNTHETIC_ERRNO(ESRCH),
"Failed to resolve user %s.", user);
if (r < 0)
return log_error_errno(r, "Failed to read from getent: %m");
(void) wait_for_terminate_and_check("getent initgroups", pid, WAIT_LOG);
/* Skip over the username and subsequent separator whitespace */
x = line;
x += strcspn(x, WHITESPACE);
x += strspn(x, WHITESPACE);
for (const char *p = x;;) {
_cleanup_free_ char *word = NULL;
r = extract_first_word(&p, &word, NULL, 0);
if (r < 0)
return log_error_errno(r, "Failed to parse group data from getent: %m");
if (r == 0)
break;
if (!GREEDY_REALLOC(gids, n_gids+1))
return log_oom();
r = parse_gid(word, &gids[n_gids++]);
if (r < 0)
return log_error_errno(r, "Failed to parse group data from getent: %m");
}
r = mkdir_parents(home, 0775);
if (r < 0)
return log_error_errno(r, "Failed to make home root directory: %m");
r = mkdir_safe(home, 0755, uid, gid, 0);
if (r < 0 && !IN_SET(r, -EEXIST, -ENOTDIR))
return log_error_errno(r, "Failed to make home directory: %m");
r = change_uid_gid_raw(uid, gid, gids, n_gids, chown_stdio);
if (r < 0)
return r;
if (ret_home)
*ret_home = TAKE_PTR(home);
return 0;
}
|
