1 | /* Cache handling for group lookup. |
2 | Copyright (C) 1998-2024 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | |
5 | This program is free software; you can redistribute it and/or modify |
6 | it under the terms of the GNU General Public License as published |
7 | by the Free Software Foundation; version 2 of the License, or |
8 | (at your option) any later version. |
9 | |
10 | This program is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
13 | GNU General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU General Public License |
16 | along with this program; if not, see <https://www.gnu.org/licenses/>. */ |
17 | |
18 | #include <assert.h> |
19 | #include <errno.h> |
20 | #include <error.h> |
21 | #include <grp.h> |
22 | #include <libintl.h> |
23 | #include <stdbool.h> |
24 | #include <stddef.h> |
25 | #include <stdio.h> |
26 | #include <stdint.h> |
27 | #include <stdlib.h> |
28 | #include <string.h> |
29 | #include <unistd.h> |
30 | #include <sys/mman.h> |
31 | #include <sys/socket.h> |
32 | #include <stackinfo.h> |
33 | #include <scratch_buffer.h> |
34 | |
35 | #include "nscd.h" |
36 | #include "dbg_log.h" |
37 | |
38 | /* This is the standard reply in case the service is disabled. */ |
39 | static const gr_response_header disabled = |
40 | { |
41 | .version = NSCD_VERSION, |
42 | .found = -1, |
43 | .gr_name_len = 0, |
44 | .gr_passwd_len = 0, |
45 | .gr_gid = -1, |
46 | .gr_mem_cnt = 0, |
47 | }; |
48 | |
49 | /* This is the struct describing how to write this record. */ |
50 | const struct iovec grp_iov_disabled = |
51 | { |
52 | .iov_base = (void *) &disabled, |
53 | .iov_len = sizeof (disabled) |
54 | }; |
55 | |
56 | |
57 | /* This is the standard reply in case we haven't found the dataset. */ |
58 | static const gr_response_header notfound = |
59 | { |
60 | .version = NSCD_VERSION, |
61 | .found = 0, |
62 | .gr_name_len = 0, |
63 | .gr_passwd_len = 0, |
64 | .gr_gid = -1, |
65 | .gr_mem_cnt = 0, |
66 | }; |
67 | |
68 | |
69 | static time_t |
70 | cache_addgr (struct database_dyn *db, int fd, request_header *req, |
71 | const void *key, struct group *grp, uid_t owner, |
72 | struct hashentry *const he, struct datahead *dh, int errval) |
73 | { |
74 | bool all_written = true; |
75 | ssize_t total; |
76 | time_t t = time (NULL); |
77 | |
78 | /* We allocate all data in one memory block: the iov vector, |
79 | the response header and the dataset itself. */ |
80 | struct dataset |
81 | { |
82 | struct datahead head; |
83 | gr_response_header resp; |
84 | char strdata[0]; |
85 | } *dataset; |
86 | |
87 | assert (offsetof (struct dataset, resp) == offsetof (struct datahead, data)); |
88 | |
89 | time_t timeout = MAX_TIMEOUT_VALUE; |
90 | if (grp == NULL) |
91 | { |
92 | if (he != NULL && errval == EAGAIN) |
93 | { |
94 | /* If we have an old record available but cannot find one |
95 | now because the service is not available we keep the old |
96 | record and make sure it does not get removed. */ |
97 | if (reload_count != UINT_MAX) |
98 | /* Do not reset the value if we never not reload the record. */ |
99 | dh->nreloads = reload_count - 1; |
100 | |
101 | /* Reload with the same time-to-live value. */ |
102 | timeout = dh->timeout = t + db->postimeout; |
103 | |
104 | total = 0; |
105 | } |
106 | else |
107 | { |
108 | /* We have no data. This means we send the standard reply for this |
109 | case. */ |
110 | total = sizeof (notfound); |
111 | |
112 | if (fd != -1 |
113 | && TEMP_FAILURE_RETRY (send (fd, ¬found, total, |
114 | MSG_NOSIGNAL)) != total) |
115 | all_written = false; |
116 | |
117 | /* If we have a transient error or cannot permanently store |
118 | the result, so be it. */ |
119 | if (errval == EAGAIN || __glibc_unlikely (db->negtimeout == 0)) |
120 | { |
121 | /* Mark the old entry as obsolete. */ |
122 | if (dh != NULL) |
123 | dh->usable = false; |
124 | } |
125 | else if ((dataset = mempool_alloc (db, len: sizeof (struct dataset) + req->key_len, data_alloc: 1)) != NULL) |
126 | { |
127 | timeout = datahead_init_neg (head: &dataset->head, |
128 | allocsize: (sizeof (struct dataset) |
129 | + req->key_len), recsize: total, |
130 | ttl: db->negtimeout); |
131 | |
132 | /* This is the reply. */ |
133 | memcpy (dest: &dataset->resp, src: ¬found, n: total); |
134 | |
135 | /* Copy the key data. */ |
136 | memcpy (dest: dataset->strdata, src: key, n: req->key_len); |
137 | |
138 | /* If necessary, we also propagate the data to disk. */ |
139 | if (db->persistent) |
140 | { |
141 | // XXX async OK? |
142 | uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1; |
143 | msync (addr: (void *) pval, |
144 | len: ((uintptr_t) dataset & pagesize_m1) |
145 | + sizeof (struct dataset) + req->key_len, MS_ASYNC); |
146 | } |
147 | |
148 | (void) cache_add (type: req->type, key: &dataset->strdata, len: req->key_len, |
149 | packet: &dataset->head, true, table: db, owner, prune_wakeup: he == NULL); |
150 | |
151 | pthread_rwlock_unlock (rwlock: &db->lock); |
152 | |
153 | /* Mark the old entry as obsolete. */ |
154 | if (dh != NULL) |
155 | dh->usable = false; |
156 | } |
157 | } |
158 | } |
159 | else |
160 | { |
161 | /* Determine the I/O structure. */ |
162 | size_t gr_name_len = strlen (s: grp->gr_name) + 1; |
163 | size_t gr_passwd_len = strlen (s: grp->gr_passwd) + 1; |
164 | size_t gr_mem_cnt = 0; |
165 | uint32_t *gr_mem_len; |
166 | size_t gr_mem_len_total = 0; |
167 | char *gr_name; |
168 | char *cp; |
169 | const size_t key_len = strlen (s: key); |
170 | const size_t buf_len = 3 * sizeof (grp->gr_gid) + key_len + 1; |
171 | size_t alloca_used = 0; |
172 | char *buf = alloca_account (buf_len, alloca_used); |
173 | ssize_t n; |
174 | size_t cnt; |
175 | |
176 | /* We need this to insert the `bygid' entry. */ |
177 | int key_offset; |
178 | n = snprintf (s: buf, maxlen: buf_len, format: "%d%c%n%s" , grp->gr_gid, '\0', |
179 | &key_offset, (char *) key) + 1; |
180 | |
181 | /* Determine the length of all members. */ |
182 | while (grp->gr_mem[gr_mem_cnt]) |
183 | ++gr_mem_cnt; |
184 | gr_mem_len = alloca_account (gr_mem_cnt * sizeof (uint32_t), alloca_used); |
185 | for (gr_mem_cnt = 0; grp->gr_mem[gr_mem_cnt]; ++gr_mem_cnt) |
186 | { |
187 | gr_mem_len[gr_mem_cnt] = strlen (s: grp->gr_mem[gr_mem_cnt]) + 1; |
188 | gr_mem_len_total += gr_mem_len[gr_mem_cnt]; |
189 | } |
190 | |
191 | total = (offsetof (struct dataset, strdata) |
192 | + gr_mem_cnt * sizeof (uint32_t) |
193 | + gr_name_len + gr_passwd_len + gr_mem_len_total); |
194 | |
195 | /* If we refill the cache, first assume the reconrd did not |
196 | change. Allocate memory on the cache since it is likely |
197 | discarded anyway. If it turns out to be necessary to have a |
198 | new record we can still allocate real memory. */ |
199 | bool dataset_temporary = false; |
200 | bool dataset_malloced = false; |
201 | dataset = NULL; |
202 | |
203 | if (he == NULL) |
204 | { |
205 | /* Prevent an INVALIDATE request from pruning the data between |
206 | the two calls to cache_add. */ |
207 | if (db->propagate) |
208 | pthread_mutex_lock (mutex: &db->prune_run_lock); |
209 | dataset = (struct dataset *) mempool_alloc (db, len: total + n, data_alloc: 1); |
210 | } |
211 | |
212 | if (dataset == NULL) |
213 | { |
214 | if (he == NULL && db->propagate) |
215 | pthread_mutex_unlock (mutex: &db->prune_run_lock); |
216 | |
217 | /* We cannot permanently add the result in the moment. But |
218 | we can provide the result as is. Store the data in some |
219 | temporary memory. */ |
220 | if (! __libc_use_alloca (size: alloca_used + total + n)) |
221 | { |
222 | dataset = malloc (size: total + n); |
223 | /* Perhaps we should log a message that we were unable |
224 | to allocate memory for a large request. */ |
225 | if (dataset == NULL) |
226 | goto out; |
227 | dataset_malloced = true; |
228 | } |
229 | else |
230 | dataset = alloca_account (total + n, alloca_used); |
231 | |
232 | /* We cannot add this record to the permanent database. */ |
233 | dataset_temporary = true; |
234 | } |
235 | |
236 | timeout = datahead_init_pos (head: &dataset->head, allocsize: total + n, |
237 | recsize: total - offsetof (struct dataset, resp), |
238 | nreloads: he == NULL ? 0 : dh->nreloads + 1, |
239 | ttl: db->postimeout); |
240 | |
241 | dataset->resp.version = NSCD_VERSION; |
242 | dataset->resp.found = 1; |
243 | dataset->resp.gr_name_len = gr_name_len; |
244 | dataset->resp.gr_passwd_len = gr_passwd_len; |
245 | dataset->resp.gr_gid = grp->gr_gid; |
246 | dataset->resp.gr_mem_cnt = gr_mem_cnt; |
247 | |
248 | cp = dataset->strdata; |
249 | |
250 | /* This is the member string length array. */ |
251 | cp = mempcpy (cp, gr_mem_len, gr_mem_cnt * sizeof (uint32_t)); |
252 | gr_name = cp; |
253 | cp = mempcpy (cp, grp->gr_name, gr_name_len); |
254 | cp = mempcpy (cp, grp->gr_passwd, gr_passwd_len); |
255 | |
256 | for (cnt = 0; cnt < gr_mem_cnt; ++cnt) |
257 | cp = mempcpy (cp, grp->gr_mem[cnt], gr_mem_len[cnt]); |
258 | |
259 | /* Finally the stringified GID value. */ |
260 | memcpy (dest: cp, src: buf, n: n); |
261 | char *key_copy = cp + key_offset; |
262 | assert (key_copy == strchr (cp, '\0') + 1); |
263 | |
264 | assert (cp == dataset->strdata + total - offsetof (struct dataset, |
265 | strdata)); |
266 | |
267 | /* Now we can determine whether on refill we have to create a new |
268 | record or not. */ |
269 | if (he != NULL) |
270 | { |
271 | assert (fd == -1); |
272 | |
273 | if (total + n == dh->allocsize |
274 | && total - offsetof (struct dataset, resp) == dh->recsize |
275 | && memcmp (s1: &dataset->resp, s2: dh->data, |
276 | n: dh->allocsize - offsetof (struct dataset, resp)) == 0) |
277 | { |
278 | /* The data has not changed. We will just bump the |
279 | timeout value. Note that the new record has been |
280 | allocated on the stack and need not be freed. */ |
281 | dh->timeout = dataset->head.timeout; |
282 | ++dh->nreloads; |
283 | |
284 | /* If the new record was allocated via malloc, then we must free |
285 | it here. */ |
286 | if (dataset_malloced) |
287 | free (ptr: dataset); |
288 | } |
289 | else |
290 | { |
291 | /* We have to create a new record. Just allocate |
292 | appropriate memory and copy it. */ |
293 | struct dataset *newp |
294 | = (struct dataset *) mempool_alloc (db, len: total + n, data_alloc: 1); |
295 | if (newp != NULL) |
296 | { |
297 | /* Adjust pointers into the memory block. */ |
298 | gr_name = (char *) newp + (gr_name - (char *) dataset); |
299 | cp = (char *) newp + (cp - (char *) dataset); |
300 | key_copy = (char *) newp + (key_copy - (char *) dataset); |
301 | |
302 | dataset = memcpy (dest: newp, src: dataset, n: total + n); |
303 | dataset_temporary = false; |
304 | } |
305 | |
306 | /* Mark the old record as obsolete. */ |
307 | dh->usable = false; |
308 | } |
309 | } |
310 | else |
311 | { |
312 | /* We write the dataset before inserting it to the database |
313 | since while inserting this thread might block and so would |
314 | unnecessarily let the receiver wait. */ |
315 | assert (fd != -1); |
316 | |
317 | if (writeall (fd, buf: &dataset->resp, len: dataset->head.recsize) |
318 | != dataset->head.recsize) |
319 | all_written = false; |
320 | } |
321 | |
322 | /* Add the record to the database. But only if it has not been |
323 | stored on the stack. */ |
324 | if (! dataset_temporary) |
325 | { |
326 | /* If necessary, we also propagate the data to disk. */ |
327 | if (db->persistent) |
328 | { |
329 | // XXX async OK? |
330 | uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1; |
331 | msync (addr: (void *) pval, |
332 | len: ((uintptr_t) dataset & pagesize_m1) + total + n, |
333 | MS_ASYNC); |
334 | } |
335 | |
336 | /* NB: in the following code we always must add the entry |
337 | marked with FIRST first. Otherwise we end up with |
338 | dangling "pointers" in case a latter hash entry cannot be |
339 | added. */ |
340 | bool first = true; |
341 | |
342 | /* If the request was by GID, add that entry first. */ |
343 | if (req->type == GETGRBYGID) |
344 | { |
345 | if (cache_add (type: GETGRBYGID, key: cp, len: key_offset, packet: &dataset->head, true, |
346 | table: db, owner, prune_wakeup: he == NULL) < 0) |
347 | goto out; |
348 | |
349 | first = false; |
350 | } |
351 | /* If the key is different from the name add a separate entry. */ |
352 | else if (strcmp (s1: key_copy, s2: gr_name) != 0) |
353 | { |
354 | if (cache_add (type: GETGRBYNAME, key: key_copy, len: key_len + 1, |
355 | packet: &dataset->head, true, table: db, owner, prune_wakeup: he == NULL) < 0) |
356 | goto out; |
357 | |
358 | first = false; |
359 | } |
360 | |
361 | /* We have to add the value for both, byname and byuid. */ |
362 | if ((req->type == GETGRBYNAME || db->propagate) |
363 | && __builtin_expect (cache_add (type: GETGRBYNAME, key: gr_name, |
364 | len: gr_name_len, |
365 | packet: &dataset->head, first, table: db, owner, |
366 | prune_wakeup: he == NULL) |
367 | == 0, 1)) |
368 | { |
369 | if (req->type == GETGRBYNAME && db->propagate) |
370 | (void) cache_add (type: GETGRBYGID, key: cp, len: key_offset, packet: &dataset->head, |
371 | false, table: db, owner, false); |
372 | } |
373 | |
374 | out: |
375 | pthread_rwlock_unlock (rwlock: &db->lock); |
376 | if (he == NULL && db->propagate) |
377 | pthread_mutex_unlock (mutex: &db->prune_run_lock); |
378 | } |
379 | } |
380 | |
381 | if (__builtin_expect (!all_written, 0) && debug_level > 0) |
382 | { |
383 | char buf[256]; |
384 | dbg_log (_("short write in %s: %s" ), __FUNCTION__, |
385 | strerror_r (errno, buf: buf, buflen: sizeof (buf))); |
386 | } |
387 | |
388 | return timeout; |
389 | } |
390 | |
391 | |
392 | union keytype |
393 | { |
394 | void *v; |
395 | gid_t g; |
396 | }; |
397 | |
398 | |
399 | static int |
400 | lookup (int type, union keytype key, struct group *resultbufp, char *buffer, |
401 | size_t buflen, struct group **grp) |
402 | { |
403 | if (type == GETGRBYNAME) |
404 | return __getgrnam_r (name: key.v, resultbuf: resultbufp, buffer: buffer, buflen: buflen, result: grp); |
405 | else |
406 | return __getgrgid_r (gid: key.g, resultbuf: resultbufp, buffer: buffer, buflen: buflen, result: grp); |
407 | } |
408 | |
409 | |
410 | static time_t |
411 | addgrbyX (struct database_dyn *db, int fd, request_header *req, |
412 | union keytype key, const char *keystr, uid_t uid, |
413 | struct hashentry *he, struct datahead *dh) |
414 | { |
415 | /* Search for the entry matching the key. Please note that we don't |
416 | look again in the table whether the dataset is now available. We |
417 | simply insert it. It does not matter if it is in there twice. The |
418 | pruning function only will look at the timestamp. */ |
419 | |
420 | struct group resultbuf; |
421 | struct group *grp; |
422 | int errval = 0; |
423 | struct scratch_buffer tmpbuf; |
424 | scratch_buffer_init (buffer: &tmpbuf); |
425 | |
426 | if (__glibc_unlikely (debug_level > 0)) |
427 | { |
428 | if (he == NULL) |
429 | dbg_log (_("Haven't found \"%s\" in group cache!" ), keystr); |
430 | else |
431 | dbg_log (_("Reloading \"%s\" in group cache!" ), keystr); |
432 | } |
433 | |
434 | while (lookup (type: req->type, key, resultbufp: &resultbuf, |
435 | buffer: tmpbuf.data, buflen: tmpbuf.length, grp: &grp) != 0 |
436 | && (errval = errno) == ERANGE) |
437 | if (!scratch_buffer_grow (buffer: &tmpbuf)) |
438 | { |
439 | /* We ran out of memory. We cannot do anything but sending a |
440 | negative response. In reality this should never |
441 | happen. */ |
442 | grp = NULL; |
443 | /* We set the error to indicate this is (possibly) a temporary |
444 | error and that it does not mean the entry is not available |
445 | at all. */ |
446 | errval = EAGAIN; |
447 | break; |
448 | } |
449 | |
450 | time_t timeout = cache_addgr (db, fd, req, key: keystr, grp, owner: uid, he, dh, errval); |
451 | scratch_buffer_free (buffer: &tmpbuf); |
452 | return timeout; |
453 | } |
454 | |
455 | |
456 | void |
457 | addgrbyname (struct database_dyn *db, int fd, request_header *req, |
458 | void *key, uid_t uid) |
459 | { |
460 | union keytype u = { .v = key }; |
461 | |
462 | addgrbyX (db, fd, req, key: u, keystr: key, uid, NULL, NULL); |
463 | } |
464 | |
465 | |
466 | time_t |
467 | readdgrbyname (struct database_dyn *db, struct hashentry *he, |
468 | struct datahead *dh) |
469 | { |
470 | request_header req = |
471 | { |
472 | .type = GETGRBYNAME, |
473 | .key_len = he->len |
474 | }; |
475 | union keytype u = { .v = db->data + he->key }; |
476 | |
477 | return addgrbyX (db, fd: -1, req: &req, key: u, keystr: db->data + he->key, uid: he->owner, he, dh); |
478 | } |
479 | |
480 | |
481 | void |
482 | addgrbygid (struct database_dyn *db, int fd, request_header *req, |
483 | void *key, uid_t uid) |
484 | { |
485 | char *ep; |
486 | gid_t gid = strtoul ((char *) key, &ep, 10); |
487 | |
488 | if (*(char *) key == '\0' || *ep != '\0') /* invalid numeric uid */ |
489 | { |
490 | if (debug_level > 0) |
491 | dbg_log (_("Invalid numeric gid \"%s\"!" ), (char *) key); |
492 | |
493 | errno = EINVAL; |
494 | return; |
495 | } |
496 | |
497 | union keytype u = { .g = gid }; |
498 | |
499 | addgrbyX (db, fd, req, key: u, keystr: key, uid, NULL, NULL); |
500 | } |
501 | |
502 | |
503 | time_t |
504 | readdgrbygid (struct database_dyn *db, struct hashentry *he, |
505 | struct datahead *dh) |
506 | { |
507 | char *ep; |
508 | gid_t gid = strtoul (db->data + he->key, &ep, 10); |
509 | |
510 | /* Since the key has been added before it must be OK. */ |
511 | assert (*(db->data + he->key) != '\0' && *ep == '\0'); |
512 | |
513 | request_header req = |
514 | { |
515 | .type = GETGRBYGID, |
516 | .key_len = he->len |
517 | }; |
518 | union keytype u = { .g = gid }; |
519 | |
520 | return addgrbyX (db, fd: -1, req: &req, key: u, keystr: db->data + he->key, uid: he->owner, he, dh); |
521 | } |
522 | |