source: MondoRescue/branches/3.3/mindi-busybox/libbb/update_passwd.c@ 3621

Last change on this file since 3621 was 3621, checked in by Bruno Cornec, 7 years ago

New 3?3 banch for incorporation of latest busybox 1.25. Changing minor version to handle potential incompatibilities.
  • Property svn:eol-style set to native
File size: 8.4 KB
Line 
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
19static 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*/
72int 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}
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