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53e1b683 | 1 | /* SPDX-License-Identifier: LGPL-2.1+ */ |
ee645080 LP |
2 | /*** |
3 | This file is part of systemd. | |
4 | ||
5 | Copyright 2015 Lennart Poettering | |
6 | ||
7 | systemd is free software; you can redistribute it and/or modify it | |
8 | under the terms of the GNU Lesser General Public License as published by | |
9 | the Free Software Foundation; either version 2.1 of the License, or | |
10 | (at your option) any later version. | |
11 | ||
12 | systemd is distributed in the hope that it will be useful, but | |
13 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
15 | Lesser General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU Lesser General Public License | |
18 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
19 | ***/ | |
20 | ||
07630cea | 21 | #include <grp.h> |
ee645080 LP |
22 | #include <sys/types.h> |
23 | #include <unistd.h> | |
ee645080 | 24 | |
b5efdb8a | 25 | #include "alloc-util.h" |
3ffd4af2 | 26 | #include "fd-util.h" |
ee645080 | 27 | #include "mkdir.h" |
3ffd4af2 | 28 | #include "nspawn-setuid.h" |
ee645080 | 29 | #include "process-util.h" |
07630cea LP |
30 | #include "signal-util.h" |
31 | #include "string-util.h" | |
b1d4f8e1 | 32 | #include "user-util.h" |
07630cea | 33 | #include "util.h" |
ee645080 LP |
34 | |
35 | static int spawn_getent(const char *database, const char *key, pid_t *rpid) { | |
4c253ed1 | 36 | int pipe_fds[2], r; |
ee645080 LP |
37 | pid_t pid; |
38 | ||
39 | assert(database); | |
40 | assert(key); | |
41 | assert(rpid); | |
42 | ||
43 | if (pipe2(pipe_fds, O_CLOEXEC) < 0) | |
44 | return log_error_errno(errno, "Failed to allocate pipe: %m"); | |
45 | ||
4c253ed1 LP |
46 | r = safe_fork("(getent)", FORK_RESET_SIGNALS|FORK_DEATHSIG, &pid); |
47 | if (r < 0) | |
48 | return log_error_errno(r, "Failed to fork getent child: %m"); | |
49 | if (r == 0) { | |
ee645080 LP |
50 | int nullfd; |
51 | char *empty_env = NULL; | |
52 | ||
53 | if (dup3(pipe_fds[1], STDOUT_FILENO, 0) < 0) | |
54 | _exit(EXIT_FAILURE); | |
55 | ||
56 | if (pipe_fds[0] > 2) | |
57 | safe_close(pipe_fds[0]); | |
58 | if (pipe_fds[1] > 2) | |
59 | safe_close(pipe_fds[1]); | |
60 | ||
61 | nullfd = open("/dev/null", O_RDWR); | |
62 | if (nullfd < 0) | |
63 | _exit(EXIT_FAILURE); | |
64 | ||
65 | if (dup3(nullfd, STDIN_FILENO, 0) < 0) | |
66 | _exit(EXIT_FAILURE); | |
67 | ||
68 | if (dup3(nullfd, STDERR_FILENO, 0) < 0) | |
69 | _exit(EXIT_FAILURE); | |
70 | ||
71 | if (nullfd > 2) | |
72 | safe_close(nullfd); | |
73 | ||
ee645080 LP |
74 | close_all_fds(NULL, 0); |
75 | ||
76 | execle("/usr/bin/getent", "getent", database, key, NULL, &empty_env); | |
77 | execle("/bin/getent", "getent", database, key, NULL, &empty_env); | |
78 | _exit(EXIT_FAILURE); | |
79 | } | |
80 | ||
81 | pipe_fds[1] = safe_close(pipe_fds[1]); | |
82 | ||
83 | *rpid = pid; | |
84 | ||
85 | return pipe_fds[0]; | |
86 | } | |
87 | ||
88 | int change_uid_gid(const char *user, char **_home) { | |
89 | char line[LINE_MAX], *x, *u, *g, *h; | |
90 | const char *word, *state; | |
91 | _cleanup_free_ uid_t *uids = NULL; | |
92 | _cleanup_free_ char *home = NULL; | |
93 | _cleanup_fclose_ FILE *f = NULL; | |
94 | _cleanup_close_ int fd = -1; | |
95 | unsigned n_uids = 0; | |
96 | size_t sz = 0, l; | |
97 | uid_t uid; | |
98 | gid_t gid; | |
99 | pid_t pid; | |
100 | int r; | |
101 | ||
102 | assert(_home); | |
103 | ||
104 | if (!user || streq(user, "root") || streq(user, "0")) { | |
105 | /* Reset everything fully to 0, just in case */ | |
106 | ||
107 | r = reset_uid_gid(); | |
108 | if (r < 0) | |
109 | return log_error_errno(r, "Failed to become root: %m"); | |
110 | ||
111 | *_home = NULL; | |
112 | return 0; | |
113 | } | |
114 | ||
115 | /* First, get user credentials */ | |
116 | fd = spawn_getent("passwd", user, &pid); | |
117 | if (fd < 0) | |
118 | return fd; | |
119 | ||
120 | f = fdopen(fd, "r"); | |
121 | if (!f) | |
122 | return log_oom(); | |
123 | fd = -1; | |
124 | ||
125 | if (!fgets(line, sizeof(line), f)) { | |
ee645080 LP |
126 | if (!ferror(f)) { |
127 | log_error("Failed to resolve user %s.", user); | |
128 | return -ESRCH; | |
129 | } | |
130 | ||
d710aaf7 | 131 | return log_error_errno(errno, "Failed to read from getent: %m"); |
ee645080 LP |
132 | } |
133 | ||
134 | truncate_nl(line); | |
135 | ||
136 | wait_for_terminate_and_warn("getent passwd", pid, true); | |
137 | ||
138 | x = strchr(line, ':'); | |
139 | if (!x) { | |
140 | log_error("/etc/passwd entry has invalid user field."); | |
141 | return -EIO; | |
142 | } | |
143 | ||
144 | u = strchr(x+1, ':'); | |
145 | if (!u) { | |
146 | log_error("/etc/passwd entry has invalid password field."); | |
147 | return -EIO; | |
148 | } | |
149 | ||
150 | u++; | |
151 | g = strchr(u, ':'); | |
152 | if (!g) { | |
153 | log_error("/etc/passwd entry has invalid UID field."); | |
154 | return -EIO; | |
155 | } | |
156 | ||
157 | *g = 0; | |
158 | g++; | |
159 | x = strchr(g, ':'); | |
160 | if (!x) { | |
161 | log_error("/etc/passwd entry has invalid GID field."); | |
162 | return -EIO; | |
163 | } | |
164 | ||
165 | *x = 0; | |
166 | h = strchr(x+1, ':'); | |
167 | if (!h) { | |
168 | log_error("/etc/passwd entry has invalid GECOS field."); | |
169 | return -EIO; | |
170 | } | |
171 | ||
172 | h++; | |
173 | x = strchr(h, ':'); | |
174 | if (!x) { | |
175 | log_error("/etc/passwd entry has invalid home directory field."); | |
176 | return -EIO; | |
177 | } | |
178 | ||
179 | *x = 0; | |
180 | ||
181 | r = parse_uid(u, &uid); | |
182 | if (r < 0) { | |
183 | log_error("Failed to parse UID of user."); | |
184 | return -EIO; | |
185 | } | |
186 | ||
187 | r = parse_gid(g, &gid); | |
188 | if (r < 0) { | |
189 | log_error("Failed to parse GID of user."); | |
190 | return -EIO; | |
191 | } | |
192 | ||
193 | home = strdup(h); | |
194 | if (!home) | |
195 | return log_oom(); | |
196 | ||
197 | /* Second, get group memberships */ | |
198 | fd = spawn_getent("initgroups", user, &pid); | |
199 | if (fd < 0) | |
200 | return fd; | |
201 | ||
202 | fclose(f); | |
203 | f = fdopen(fd, "r"); | |
204 | if (!f) | |
205 | return log_oom(); | |
206 | fd = -1; | |
207 | ||
208 | if (!fgets(line, sizeof(line), f)) { | |
209 | if (!ferror(f)) { | |
210 | log_error("Failed to resolve user %s.", user); | |
211 | return -ESRCH; | |
212 | } | |
213 | ||
d710aaf7 | 214 | return log_error_errno(errno, "Failed to read from getent: %m"); |
ee645080 LP |
215 | } |
216 | ||
217 | truncate_nl(line); | |
218 | ||
219 | wait_for_terminate_and_warn("getent initgroups", pid, true); | |
220 | ||
221 | /* Skip over the username and subsequent separator whitespace */ | |
222 | x = line; | |
223 | x += strcspn(x, WHITESPACE); | |
224 | x += strspn(x, WHITESPACE); | |
225 | ||
226 | FOREACH_WORD(word, l, x, state) { | |
227 | char c[l+1]; | |
228 | ||
229 | memcpy(c, word, l); | |
230 | c[l] = 0; | |
231 | ||
232 | if (!GREEDY_REALLOC(uids, sz, n_uids+1)) | |
233 | return log_oom(); | |
234 | ||
235 | r = parse_uid(c, &uids[n_uids++]); | |
236 | if (r < 0) { | |
237 | log_error("Failed to parse group data from getent."); | |
238 | return -EIO; | |
239 | } | |
240 | } | |
241 | ||
242 | r = mkdir_parents(home, 0775); | |
243 | if (r < 0) | |
244 | return log_error_errno(r, "Failed to make home root directory: %m"); | |
245 | ||
c31ad024 | 246 | r = mkdir_safe(home, 0755, uid, gid, false); |
ee645080 LP |
247 | if (r < 0 && r != -EEXIST) |
248 | return log_error_errno(r, "Failed to make home directory: %m"); | |
249 | ||
250 | (void) fchown(STDIN_FILENO, uid, gid); | |
251 | (void) fchown(STDOUT_FILENO, uid, gid); | |
252 | (void) fchown(STDERR_FILENO, uid, gid); | |
253 | ||
254 | if (setgroups(n_uids, uids) < 0) | |
255 | return log_error_errno(errno, "Failed to set auxiliary groups: %m"); | |
256 | ||
257 | if (setresgid(gid, gid, gid) < 0) | |
d2b8497d | 258 | return log_error_errno(errno, "setresgid() failed: %m"); |
ee645080 LP |
259 | |
260 | if (setresuid(uid, uid, uid) < 0) | |
d2b8497d | 261 | return log_error_errno(errno, "setresuid() failed: %m"); |
ee645080 LP |
262 | |
263 | if (_home) { | |
264 | *_home = home; | |
265 | home = NULL; | |
266 | } | |
267 | ||
268 | return 0; | |
269 | } |