blob: a2004f480ca757a2faf3d3f1918ec3a05e9c3ddb
1 | /* vi: set sw=4 ts=4: */ |
2 | /* |
3 | * update_passwd |
4 | * |
5 | * update_passwd is a common function for passwd and chpasswd applets; |
6 | * it is responsible for updating password file (i.e. /etc/passwd or |
7 | * /etc/shadow) for a given user and password. |
8 | * |
9 | * Moved from loginutils/passwd.c by Alexander Shishkin <virtuoso@slind.org> |
10 | * |
11 | * Modified to be able to add or delete users, groups and users to/from groups |
12 | * by Tito Ragusa <farmatito@tiscali.it> |
13 | * |
14 | * Licensed under GPLv2, see file LICENSE in this source tree. |
15 | */ |
16 | #include "libbb.h" |
17 | |
18 | #if ENABLE_SELINUX |
19 | static void check_selinux_update_passwd(const char *username) |
20 | { |
21 | security_context_t context; |
22 | char *seuser; |
23 | |
24 | if (getuid() != (uid_t)0 || is_selinux_enabled() == 0) |
25 | return; /* No need to check */ |
26 | |
27 | if (getprevcon_raw(&context) < 0) |
28 | bb_perror_msg_and_die("getprevcon failed"); |
29 | seuser = strtok(context, ":"); |
30 | if (!seuser) |
31 | bb_error_msg_and_die("invalid context '%s'", context); |
32 | if (strcmp(seuser, username) != 0) { |
33 | if (checkPasswdAccess(PASSWD__PASSWD) != 0) |
34 | bb_error_msg_and_die("SELinux: access denied"); |
35 | } |
36 | if (ENABLE_FEATURE_CLEAN_UP) |
37 | freecon(context); |
38 | } |
39 | #else |
40 | # define check_selinux_update_passwd(username) ((void)0) |
41 | #endif |
42 | |
43 | /* |
44 | 1) add a user: update_passwd(FILE, USER, REMAINING_PWLINE, NULL) |
45 | only if CONFIG_ADDUSER=y and applet_name[0] == 'a' like in adduser |
46 | |
47 | 2) add a group: update_passwd(FILE, GROUP, REMAINING_GRLINE, NULL) |
48 | only if CONFIG_ADDGROUP=y and applet_name[0] == 'a' like in addgroup |
49 | |
50 | 3) add a user to a group: update_passwd(FILE, GROUP, NULL, MEMBER) |
51 | only if CONFIG_FEATURE_ADDUSER_TO_GROUP=y, applet_name[0] == 'a' |
52 | like in addgroup and member != NULL |
53 | |
54 | 4) delete a user: update_passwd(FILE, USER, NULL, NULL) |
55 | |
56 | 5) delete a group: update_passwd(FILE, GROUP, NULL, NULL) |
57 | |
58 | 6) delete a user from a group: update_passwd(FILE, GROUP, NULL, MEMBER) |
59 | only if CONFIG_FEATURE_DEL_USER_FROM_GROUP=y and member != NULL |
60 | |
61 | 7) change user's password: update_passwd(FILE, USER, NEW_PASSWD, NULL) |
62 | only if CONFIG_PASSWD=y and applet_name[0] == 'p' like in passwd |
63 | or if CONFIG_CHPASSWD=y and applet_name[0] == 'c' like in chpasswd |
64 | |
65 | 8) delete a user from all groups: update_passwd(FILE, NULL, NULL, MEMBER) |
66 | |
67 | This function does not validate the arguments fed to it |
68 | so the calling program should take care of that. |
69 | |
70 | Returns number of lines changed, or -1 on error. |
71 | */ |
72 | int FAST_FUNC update_passwd(const char *filename, |
73 | const char *name, |
74 | const char *new_passwd, |
75 | const char *member) |
76 | { |
77 | #if !(ENABLE_FEATURE_ADDUSER_TO_GROUP || ENABLE_FEATURE_DEL_USER_FROM_GROUP) |
78 | #define member NULL |
79 | #endif |
80 | struct stat sb; |
81 | struct flock lock; |
82 | FILE *old_fp; |
83 | FILE *new_fp; |
84 | char *fnamesfx; |
85 | char *sfx_char; |
86 | char *name_colon; |
87 | int old_fd; |
88 | int new_fd; |
89 | int i; |
90 | int changed_lines; |
91 | int ret = -1; /* failure */ |
92 | /* used as a bool: "are we modifying /etc/shadow?" */ |
93 | #if ENABLE_FEATURE_SHADOWPASSWDS |
94 | const char *shadow = strstr(filename, "shadow"); |
95 | #else |
96 | # define shadow NULL |
97 | #endif |
98 | |
99 | filename = xmalloc_follow_symlinks(filename); |
100 | if (filename == NULL) |
101 | return ret; |
102 | |
103 | if (name) |
104 | check_selinux_update_passwd(name); |
105 | |
106 | /* New passwd file, "/etc/passwd+" for now */ |
107 | fnamesfx = xasprintf("%s+", filename); |
108 | sfx_char = &fnamesfx[strlen(fnamesfx)-1]; |
109 | name_colon = xasprintf("%s:", name ? name : ""); |
110 | |
111 | if (shadow) |
112 | old_fp = fopen(filename, "r+"); |
113 | else |
114 | old_fp = fopen_or_warn(filename, "r+"); |
115 | if (!old_fp) { |
116 | if (shadow) |
117 | ret = 0; /* missing shadow is not an error */ |
118 | goto free_mem; |
119 | } |
120 | old_fd = fileno(old_fp); |
121 | |
122 | selinux_preserve_fcontext(old_fd); |
123 | |
124 | /* Try to create "/etc/passwd+". Wait if it exists. */ |
125 | i = 30; |
126 | do { |
127 | // FIXME: on last iteration try w/o O_EXCL but with O_TRUNC? |
128 | new_fd = open(fnamesfx, O_WRONLY|O_CREAT|O_EXCL, 0600); |
129 | if (new_fd >= 0) goto created; |
130 | if (errno != EEXIST) break; |
131 | usleep(100000); /* 0.1 sec */ |
132 | } while (--i); |
133 | bb_perror_msg("can't create '%s'", fnamesfx); |
134 | goto close_old_fp; |
135 | |
136 | created: |
137 | if (fstat(old_fd, &sb) == 0) { |
138 | fchmod(new_fd, sb.st_mode & 0777); /* ignore errors */ |
139 | fchown(new_fd, sb.st_uid, sb.st_gid); |
140 | } |
141 | errno = 0; |
142 | new_fp = xfdopen_for_write(new_fd); |
143 | |
144 | /* Backup file is "/etc/passwd-" */ |
145 | *sfx_char = '-'; |
146 | /* Delete old backup */ |
147 | i = (unlink(fnamesfx) && errno != ENOENT); |
148 | /* Create backup as a hardlink to current */ |
149 | if (i || link(filename, fnamesfx)) |
150 | bb_perror_msg("warning: can't create backup copy '%s'", |
151 | fnamesfx); |
152 | *sfx_char = '+'; |
153 | |
154 | /* Lock the password file before updating */ |
155 | lock.l_type = F_WRLCK; |
156 | lock.l_whence = SEEK_SET; |
157 | lock.l_start = 0; |
158 | lock.l_len = 0; |
159 | if (fcntl(old_fd, F_SETLK, &lock) < 0) |
160 | bb_perror_msg("warning: can't lock '%s'", filename); |
161 | lock.l_type = F_UNLCK; |
162 | |
163 | /* Read current password file, write updated /etc/passwd+ */ |
164 | changed_lines = 0; |
165 | while (1) { |
166 | char *cp, *line; |
167 | |
168 | line = xmalloc_fgetline(old_fp); |
169 | if (!line) /* EOF/error */ |
170 | break; |
171 | |
172 | if (!name && member) { |
173 | /* Delete member from all groups */ |
174 | /* line is "GROUP:PASSWD:[member1[,member2]...]" */ |
175 | unsigned member_len = strlen(member); |
176 | char *list = strrchr(line, ':'); |
177 | while (list) { |
178 | list++; |
179 | next_list_element: |
180 | if (is_prefixed_with(list, member)) { |
181 | char c; |
182 | changed_lines++; |
183 | c = list[member_len]; |
184 | if (c == '\0') { |
185 | if (list[-1] == ',') |
186 | list--; |
187 | *list = '\0'; |
188 | break; |
189 | } |
190 | if (c == ',') { |
191 | overlapping_strcpy(list, list + member_len + 1); |
192 | goto next_list_element; |
193 | } |
194 | changed_lines--; |
195 | } |
196 | list = strchr(list, ','); |
197 | } |
198 | fprintf(new_fp, "%s\n", line); |
199 | goto next; |
200 | } |
201 | |
202 | cp = is_prefixed_with(line, name_colon); |
203 | if (!cp) { |
204 | fprintf(new_fp, "%s\n", line); |
205 | goto next; |
206 | } |
207 | |
208 | /* We have a match with "name:"... */ |
209 | /* cp points past "name:" */ |
210 | |
211 | #if ENABLE_FEATURE_ADDUSER_TO_GROUP || ENABLE_FEATURE_DEL_USER_FROM_GROUP |
212 | if (member) { |
213 | /* It's actually /etc/group+, not /etc/passwd+ */ |
214 | if (ENABLE_FEATURE_ADDUSER_TO_GROUP |
215 | && applet_name[0] == 'a' |
216 | ) { |
217 | /* Add user to group */ |
218 | fprintf(new_fp, "%s%s%s\n", line, |
219 | last_char_is(line, ':') ? "" : ",", |
220 | member); |
221 | changed_lines++; |
222 | } else if (ENABLE_FEATURE_DEL_USER_FROM_GROUP |
223 | /* && applet_name[0] == 'd' */ |
224 | ) { |
225 | /* Delete user from group */ |
226 | char *tmp; |
227 | const char *fmt = "%s"; |
228 | |
229 | /* find the start of the member list: last ':' */ |
230 | cp = strrchr(line, ':'); |
231 | /* cut it */ |
232 | *cp++ = '\0'; |
233 | /* write the cut line name:passwd:gid: |
234 | * or name:!:: */ |
235 | fprintf(new_fp, "%s:", line); |
236 | /* parse the tokens of the member list */ |
237 | tmp = cp; |
238 | while ((cp = strsep(&tmp, ",")) != NULL) { |
239 | if (strcmp(member, cp) != 0) { |
240 | fprintf(new_fp, fmt, cp); |
241 | fmt = ",%s"; |
242 | } else { |
243 | /* found member, skip it */ |
244 | changed_lines++; |
245 | } |
246 | } |
247 | fprintf(new_fp, "\n"); |
248 | } |
249 | } else |
250 | #endif |
251 | if ((ENABLE_PASSWD && applet_name[0] == 'p') |
252 | || (ENABLE_CHPASSWD && applet_name[0] == 'c') |
253 | ) { |
254 | /* Change passwd */ |
255 | cp = strchrnul(cp, ':'); /* move past old passwd */ |
256 | |
257 | if (shadow && *cp == ':') { |
258 | /* /etc/shadow's field 3 (passwd change date) needs updating */ |
259 | /* move past old change date */ |
260 | cp = strchrnul(cp + 1, ':'); |
261 | /* "name:" + "new_passwd" + ":" + "change date" + ":rest of line" */ |
262 | fprintf(new_fp, "%s%s:%u%s\n", name_colon, new_passwd, |
263 | (unsigned)(time(NULL)) / (24*60*60), cp); |
264 | } else { |
265 | /* "name:" + "new_passwd" + ":rest of line" */ |
266 | fprintf(new_fp, "%s%s%s\n", name_colon, new_passwd, cp); |
267 | } |
268 | changed_lines++; |
269 | } /* else delete user or group: skip the line */ |
270 | next: |
271 | free(line); |
272 | } |
273 | |
274 | if (changed_lines == 0) { |
275 | #if ENABLE_FEATURE_ADDUSER_TO_GROUP || ENABLE_FEATURE_DEL_USER_FROM_GROUP |
276 | if (member) { |
277 | if (ENABLE_ADDGROUP && applet_name[0] == 'a') |
278 | bb_error_msg("can't find %s in %s", name, filename); |
279 | if (ENABLE_DELGROUP && applet_name[0] == 'd') |
280 | bb_error_msg("can't find %s in %s", member, filename); |
281 | } |
282 | #endif |
283 | if ((ENABLE_ADDUSER || ENABLE_ADDGROUP) |
284 | && applet_name[0] == 'a' && !member |
285 | ) { |
286 | /* add user or group */ |
287 | fprintf(new_fp, "%s%s\n", name_colon, new_passwd); |
288 | changed_lines++; |
289 | } |
290 | } |
291 | |
292 | fcntl(old_fd, F_SETLK, &lock); |
293 | |
294 | /* We do want all of them to execute, thus | instead of || */ |
295 | errno = 0; |
296 | if ((ferror(old_fp) | fflush(new_fp) | fsync(new_fd) | fclose(new_fp)) |
297 | || rename(fnamesfx, filename) |
298 | ) { |
299 | /* At least one of those failed */ |
300 | bb_perror_nomsg(); |
301 | goto unlink_new; |
302 | } |
303 | /* Success: ret >= 0 */ |
304 | ret = changed_lines; |
305 | |
306 | unlink_new: |
307 | if (ret < 0) |
308 | unlink(fnamesfx); |
309 | |
310 | close_old_fp: |
311 | fclose(old_fp); |
312 | |
313 | free_mem: |
314 | free(fnamesfx); |
315 | free((char *)filename); |
316 | free(name_colon); |
317 | return ret; |
318 | } |
319 |