lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame] | 1 | /* Cache handling for passwd lookup. |
| 2 | Copyright (C) 1998-2015 Free Software Foundation, Inc. |
| 3 | This file is part of the GNU C Library. |
| 4 | Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998. |
| 5 | |
| 6 | This program is free software; you can redistribute it and/or modify |
| 7 | it under the terms of the GNU General Public License as published |
| 8 | by the Free Software Foundation; version 2 of the License, or |
| 9 | (at your option) any later version. |
| 10 | |
| 11 | This program is distributed in the hope that it will be useful, |
| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | GNU General Public License for more details. |
| 15 | |
| 16 | You should have received a copy of the GNU General Public License |
| 17 | along with this program; if not, see <http://www.gnu.org/licenses/>. */ |
| 18 | |
| 19 | #include <alloca.h> |
| 20 | #include <assert.h> |
| 21 | #include <errno.h> |
| 22 | #include <error.h> |
| 23 | #include <libintl.h> |
| 24 | #include <pwd.h> |
| 25 | #include <stdbool.h> |
| 26 | #include <stddef.h> |
| 27 | #include <stdio.h> |
| 28 | #include <stdlib.h> |
| 29 | #include <string.h> |
| 30 | #include <time.h> |
| 31 | #include <unistd.h> |
| 32 | #include <sys/mman.h> |
| 33 | #include <sys/socket.h> |
| 34 | #include <stackinfo.h> |
| 35 | |
| 36 | #include "nscd.h" |
| 37 | #include "dbg_log.h" |
| 38 | #ifdef HAVE_SENDFILE |
| 39 | # include <kernel-features.h> |
| 40 | #endif |
| 41 | |
| 42 | /* This is the standard reply in case the service is disabled. */ |
| 43 | static const pw_response_header disabled = |
| 44 | { |
| 45 | .version = NSCD_VERSION, |
| 46 | .found = -1, |
| 47 | .pw_name_len = 0, |
| 48 | .pw_passwd_len = 0, |
| 49 | .pw_uid = -1, |
| 50 | .pw_gid = -1, |
| 51 | .pw_gecos_len = 0, |
| 52 | .pw_dir_len = 0, |
| 53 | .pw_shell_len = 0 |
| 54 | }; |
| 55 | |
| 56 | /* This is the struct describing how to write this record. */ |
| 57 | const struct iovec pwd_iov_disabled = |
| 58 | { |
| 59 | .iov_base = (void *) &disabled, |
| 60 | .iov_len = sizeof (disabled) |
| 61 | }; |
| 62 | |
| 63 | |
| 64 | /* This is the standard reply in case we haven't found the dataset. */ |
| 65 | static const pw_response_header notfound = |
| 66 | { |
| 67 | .version = NSCD_VERSION, |
| 68 | .found = 0, |
| 69 | .pw_name_len = 0, |
| 70 | .pw_passwd_len = 0, |
| 71 | .pw_uid = -1, |
| 72 | .pw_gid = -1, |
| 73 | .pw_gecos_len = 0, |
| 74 | .pw_dir_len = 0, |
| 75 | .pw_shell_len = 0 |
| 76 | }; |
| 77 | |
| 78 | |
| 79 | static time_t |
| 80 | cache_addpw (struct database_dyn *db, int fd, request_header *req, |
| 81 | const void *key, struct passwd *pwd, uid_t owner, |
| 82 | struct hashentry *const he, struct datahead *dh, int errval) |
| 83 | { |
| 84 | bool all_written = true; |
| 85 | ssize_t total; |
| 86 | time_t t = time (NULL); |
| 87 | |
| 88 | /* We allocate all data in one memory block: the iov vector, |
| 89 | the response header and the dataset itself. */ |
| 90 | struct dataset |
| 91 | { |
| 92 | struct datahead head; |
| 93 | pw_response_header resp; |
| 94 | char strdata[0]; |
| 95 | } *dataset; |
| 96 | |
| 97 | assert (offsetof (struct dataset, resp) == offsetof (struct datahead, data)); |
| 98 | |
| 99 | time_t timeout = MAX_TIMEOUT_VALUE; |
| 100 | if (pwd == NULL) |
| 101 | { |
| 102 | if (he != NULL && errval == EAGAIN) |
| 103 | { |
| 104 | /* If we have an old record available but cannot find one |
| 105 | now because the service is not available we keep the old |
| 106 | record and make sure it does not get removed. */ |
| 107 | if (reload_count != UINT_MAX && dh->nreloads == reload_count) |
| 108 | /* Do not reset the value if we never not reload the record. */ |
| 109 | dh->nreloads = reload_count - 1; |
| 110 | |
| 111 | /* Reload with the same time-to-live value. */ |
| 112 | timeout = dh->timeout = t + db->postimeout; |
| 113 | |
| 114 | total = 0; |
| 115 | } |
| 116 | else |
| 117 | { |
| 118 | /* We have no data. This means we send the standard reply for this |
| 119 | case. */ |
| 120 | total = sizeof (notfound); |
| 121 | |
| 122 | if (fd != -1 |
| 123 | && TEMP_FAILURE_RETRY (send (fd, ¬found, total, |
| 124 | MSG_NOSIGNAL)) != total) |
| 125 | all_written = false; |
| 126 | |
| 127 | /* If we have a transient error or cannot permanently store |
| 128 | the result, so be it. */ |
| 129 | if (errno == EAGAIN || __builtin_expect (db->negtimeout == 0, 0)) |
| 130 | { |
| 131 | /* Mark the old entry as obsolete. */ |
| 132 | if (dh != NULL) |
| 133 | dh->usable = false; |
| 134 | } |
| 135 | else if ((dataset = mempool_alloc (db, (sizeof (struct dataset) |
| 136 | + req->key_len), 1)) != NULL) |
| 137 | { |
| 138 | timeout = datahead_init_neg (&dataset->head, |
| 139 | (sizeof (struct dataset) |
| 140 | + req->key_len), total, |
| 141 | db->negtimeout); |
| 142 | |
| 143 | /* This is the reply. */ |
| 144 | memcpy (&dataset->resp, ¬found, total); |
| 145 | |
| 146 | /* Copy the key data. */ |
| 147 | char *key_copy = memcpy (dataset->strdata, key, req->key_len); |
| 148 | |
| 149 | /* If necessary, we also propagate the data to disk. */ |
| 150 | if (db->persistent) |
| 151 | { |
| 152 | // XXX async OK? |
| 153 | uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1; |
| 154 | msync ((void *) pval, |
| 155 | ((uintptr_t) dataset & pagesize_m1) |
| 156 | + sizeof (struct dataset) + req->key_len, MS_ASYNC); |
| 157 | } |
| 158 | |
| 159 | (void) cache_add (req->type, key_copy, req->key_len, |
| 160 | &dataset->head, true, db, owner, he == NULL); |
| 161 | |
| 162 | pthread_rwlock_unlock (&db->lock); |
| 163 | |
| 164 | /* Mark the old entry as obsolete. */ |
| 165 | if (dh != NULL) |
| 166 | dh->usable = false; |
| 167 | } |
| 168 | } |
| 169 | } |
| 170 | else |
| 171 | { |
| 172 | /* Determine the I/O structure. */ |
| 173 | size_t pw_name_len = strlen (pwd->pw_name) + 1; |
| 174 | size_t pw_passwd_len = strlen (pwd->pw_passwd) + 1; |
| 175 | size_t pw_gecos_len = strlen (pwd->pw_gecos) + 1; |
| 176 | size_t pw_dir_len = strlen (pwd->pw_dir) + 1; |
| 177 | size_t pw_shell_len = strlen (pwd->pw_shell) + 1; |
| 178 | char *cp; |
| 179 | const size_t key_len = strlen (key); |
| 180 | const size_t buf_len = 3 * sizeof (pwd->pw_uid) + key_len + 1; |
| 181 | char *buf = alloca (buf_len); |
| 182 | ssize_t n; |
| 183 | |
| 184 | /* We need this to insert the `byuid' entry. */ |
| 185 | int key_offset; |
| 186 | n = snprintf (buf, buf_len, "%d%c%n%s", pwd->pw_uid, '\0', |
| 187 | &key_offset, (char *) key) + 1; |
| 188 | |
| 189 | total = (offsetof (struct dataset, strdata) |
| 190 | + pw_name_len + pw_passwd_len |
| 191 | + pw_gecos_len + pw_dir_len + pw_shell_len); |
| 192 | |
| 193 | /* If we refill the cache, first assume the reconrd did not |
| 194 | change. Allocate memory on the cache since it is likely |
| 195 | discarded anyway. If it turns out to be necessary to have a |
| 196 | new record we can still allocate real memory. */ |
| 197 | bool alloca_used = false; |
| 198 | dataset = NULL; |
| 199 | |
| 200 | if (he == NULL) |
| 201 | dataset = (struct dataset *) mempool_alloc (db, total + n, 1); |
| 202 | |
| 203 | if (dataset == NULL) |
| 204 | { |
| 205 | /* We cannot permanently add the result in the moment. But |
| 206 | we can provide the result as is. Store the data in some |
| 207 | temporary memory. */ |
| 208 | dataset = (struct dataset *) alloca (total + n); |
| 209 | |
| 210 | /* We cannot add this record to the permanent database. */ |
| 211 | alloca_used = true; |
| 212 | } |
| 213 | |
| 214 | timeout = datahead_init_pos (&dataset->head, total + n, |
| 215 | total - offsetof (struct dataset, resp), |
| 216 | he == NULL ? 0 : dh->nreloads + 1, |
| 217 | db->postimeout); |
| 218 | |
| 219 | dataset->resp.version = NSCD_VERSION; |
| 220 | dataset->resp.found = 1; |
| 221 | dataset->resp.pw_name_len = pw_name_len; |
| 222 | dataset->resp.pw_passwd_len = pw_passwd_len; |
| 223 | dataset->resp.pw_uid = pwd->pw_uid; |
| 224 | dataset->resp.pw_gid = pwd->pw_gid; |
| 225 | dataset->resp.pw_gecos_len = pw_gecos_len; |
| 226 | dataset->resp.pw_dir_len = pw_dir_len; |
| 227 | dataset->resp.pw_shell_len = pw_shell_len; |
| 228 | |
| 229 | cp = dataset->strdata; |
| 230 | |
| 231 | /* Copy the strings over into the buffer. */ |
| 232 | cp = mempcpy (cp, pwd->pw_name, pw_name_len); |
| 233 | cp = mempcpy (cp, pwd->pw_passwd, pw_passwd_len); |
| 234 | cp = mempcpy (cp, pwd->pw_gecos, pw_gecos_len); |
| 235 | cp = mempcpy (cp, pwd->pw_dir, pw_dir_len); |
| 236 | cp = mempcpy (cp, pwd->pw_shell, pw_shell_len); |
| 237 | |
| 238 | /* Finally the stringified UID value. */ |
| 239 | memcpy (cp, buf, n); |
| 240 | char *key_copy = cp + key_offset; |
| 241 | assert (key_copy == (char *) rawmemchr (cp, '\0') + 1); |
| 242 | |
| 243 | assert (cp == dataset->strdata + total - offsetof (struct dataset, |
| 244 | strdata)); |
| 245 | |
| 246 | /* Now we can determine whether on refill we have to create a new |
| 247 | record or not. */ |
| 248 | if (he != NULL) |
| 249 | { |
| 250 | assert (fd == -1); |
| 251 | |
| 252 | if (dataset->head.allocsize == dh->allocsize |
| 253 | && dataset->head.recsize == dh->recsize |
| 254 | && memcmp (&dataset->resp, dh->data, |
| 255 | dh->allocsize - offsetof (struct dataset, resp)) == 0) |
| 256 | { |
| 257 | /* The data has not changed. We will just bump the |
| 258 | timeout value. Note that the new record has been |
| 259 | allocated on the stack and need not be freed. */ |
| 260 | dh->timeout = dataset->head.timeout; |
| 261 | ++dh->nreloads; |
| 262 | } |
| 263 | else |
| 264 | { |
| 265 | /* We have to create a new record. Just allocate |
| 266 | appropriate memory and copy it. */ |
| 267 | struct dataset *newp |
| 268 | = (struct dataset *) mempool_alloc (db, total + n, 1); |
| 269 | if (newp != NULL) |
| 270 | { |
| 271 | /* Adjust pointer into the memory block. */ |
| 272 | cp = (char *) newp + (cp - (char *) dataset); |
| 273 | key_copy = (char *) newp + (key_copy - (char *) dataset); |
| 274 | |
| 275 | dataset = memcpy (newp, dataset, total + n); |
| 276 | alloca_used = false; |
| 277 | } |
| 278 | |
| 279 | /* Mark the old record as obsolete. */ |
| 280 | dh->usable = false; |
| 281 | } |
| 282 | } |
| 283 | else |
| 284 | { |
| 285 | /* We write the dataset before inserting it to the database |
| 286 | since while inserting this thread might block and so would |
| 287 | unnecessarily let the receiver wait. */ |
| 288 | assert (fd != -1); |
| 289 | |
| 290 | #ifdef HAVE_SENDFILE |
| 291 | if (__builtin_expect (db->mmap_used, 1) && !alloca_used) |
| 292 | { |
| 293 | assert (db->wr_fd != -1); |
| 294 | assert ((char *) &dataset->resp > (char *) db->data); |
| 295 | assert ((char *) dataset - (char *) db->head |
| 296 | + total |
| 297 | <= (sizeof (struct database_pers_head) |
| 298 | + db->head->module * sizeof (ref_t) |
| 299 | + db->head->data_size)); |
| 300 | ssize_t written = sendfileall (fd, db->wr_fd, |
| 301 | (char *) &dataset->resp |
| 302 | - (char *) db->head, |
| 303 | dataset->head.recsize); |
| 304 | if (written != dataset->head.recsize) |
| 305 | { |
| 306 | # ifndef __ASSUME_SENDFILE |
| 307 | if (written == -1 && errno == ENOSYS) |
| 308 | goto use_write; |
| 309 | # endif |
| 310 | all_written = false; |
| 311 | } |
| 312 | } |
| 313 | else |
| 314 | # ifndef __ASSUME_SENDFILE |
| 315 | use_write: |
| 316 | # endif |
| 317 | #endif |
| 318 | if (writeall (fd, &dataset->resp, dataset->head.recsize) |
| 319 | != dataset->head.recsize) |
| 320 | all_written = false; |
| 321 | } |
| 322 | |
| 323 | |
| 324 | /* Add the record to the database. But only if it has not been |
| 325 | stored on the stack. */ |
| 326 | if (! alloca_used) |
| 327 | { |
| 328 | /* If necessary, we also propagate the data to disk. */ |
| 329 | if (db->persistent) |
| 330 | { |
| 331 | // XXX async OK? |
| 332 | uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1; |
| 333 | msync ((void *) pval, |
| 334 | ((uintptr_t) dataset & pagesize_m1) + total + n, |
| 335 | MS_ASYNC); |
| 336 | } |
| 337 | |
| 338 | /* NB: in the following code we always must add the entry |
| 339 | marked with FIRST first. Otherwise we end up with |
| 340 | dangling "pointers" in case a latter hash entry cannot be |
| 341 | added. */ |
| 342 | bool first = true; |
| 343 | |
| 344 | /* If the request was by UID, add that entry first. */ |
| 345 | if (req->type == GETPWBYUID) |
| 346 | { |
| 347 | if (cache_add (GETPWBYUID, cp, key_offset, &dataset->head, true, |
| 348 | db, owner, he == NULL) < 0) |
| 349 | goto out; |
| 350 | |
| 351 | first = false; |
| 352 | } |
| 353 | /* If the key is different from the name add a separate entry. */ |
| 354 | else if (strcmp (key_copy, dataset->strdata) != 0) |
| 355 | { |
| 356 | if (cache_add (GETPWBYNAME, key_copy, key_len + 1, |
| 357 | &dataset->head, true, db, owner, he == NULL) < 0) |
| 358 | goto out; |
| 359 | |
| 360 | first = false; |
| 361 | } |
| 362 | |
| 363 | /* We have to add the value for both, byname and byuid. */ |
| 364 | if ((req->type == GETPWBYNAME || db->propagate) |
| 365 | && __builtin_expect (cache_add (GETPWBYNAME, dataset->strdata, |
| 366 | pw_name_len, &dataset->head, |
| 367 | first, db, owner, he == NULL) |
| 368 | == 0, 1)) |
| 369 | { |
| 370 | if (req->type == GETPWBYNAME && db->propagate) |
| 371 | (void) cache_add (GETPWBYUID, cp, key_offset, &dataset->head, |
| 372 | false, db, owner, false); |
| 373 | } |
| 374 | |
| 375 | out: |
| 376 | pthread_rwlock_unlock (&db->lock); |
| 377 | } |
| 378 | } |
| 379 | |
| 380 | if (__builtin_expect (!all_written, 0) && debug_level > 0) |
| 381 | { |
| 382 | char buf[256]; |
| 383 | dbg_log (_("short write in %s: %s"), __FUNCTION__, |
| 384 | strerror_r (errno, buf, sizeof (buf))); |
| 385 | } |
| 386 | |
| 387 | return timeout; |
| 388 | } |
| 389 | |
| 390 | |
| 391 | union keytype |
| 392 | { |
| 393 | void *v; |
| 394 | uid_t u; |
| 395 | }; |
| 396 | |
| 397 | |
| 398 | static int |
| 399 | lookup (int type, union keytype key, struct passwd *resultbufp, char *buffer, |
| 400 | size_t buflen, struct passwd **pwd) |
| 401 | { |
| 402 | if (type == GETPWBYNAME) |
| 403 | return __getpwnam_r (key.v, resultbufp, buffer, buflen, pwd); |
| 404 | else |
| 405 | return __getpwuid_r (key.u, resultbufp, buffer, buflen, pwd); |
| 406 | } |
| 407 | |
| 408 | |
| 409 | static time_t |
| 410 | addpwbyX (struct database_dyn *db, int fd, request_header *req, |
| 411 | union keytype key, const char *keystr, uid_t c_uid, |
| 412 | struct hashentry *he, struct datahead *dh) |
| 413 | { |
| 414 | /* Search for the entry matching the key. Please note that we don't |
| 415 | look again in the table whether the dataset is now available. We |
| 416 | simply insert it. It does not matter if it is in there twice. The |
| 417 | pruning function only will look at the timestamp. */ |
| 418 | size_t buflen = 1024; |
| 419 | char *buffer = (char *) alloca (buflen); |
| 420 | struct passwd resultbuf; |
| 421 | struct passwd *pwd; |
| 422 | bool use_malloc = false; |
| 423 | int errval = 0; |
| 424 | |
| 425 | if (__glibc_unlikely (debug_level > 0)) |
| 426 | { |
| 427 | if (he == NULL) |
| 428 | dbg_log (_("Haven't found \"%s\" in password cache!"), keystr); |
| 429 | else |
| 430 | dbg_log (_("Reloading \"%s\" in password cache!"), keystr); |
| 431 | } |
| 432 | |
| 433 | while (lookup (req->type, key, &resultbuf, buffer, buflen, &pwd) != 0 |
| 434 | && (errval = errno) == ERANGE) |
| 435 | { |
| 436 | errno = 0; |
| 437 | |
| 438 | if (__glibc_unlikely (buflen > 32768)) |
| 439 | { |
| 440 | char *old_buffer = buffer; |
| 441 | buflen *= 2; |
| 442 | buffer = (char *) realloc (use_malloc ? buffer : NULL, buflen); |
| 443 | if (buffer == NULL) |
| 444 | { |
| 445 | /* We ran out of memory. We cannot do anything but |
| 446 | sending a negative response. In reality this should |
| 447 | never happen. */ |
| 448 | pwd = NULL; |
| 449 | buffer = old_buffer; |
| 450 | |
| 451 | /* We set the error to indicate this is (possibly) a |
| 452 | temporary error and that it does not mean the entry |
| 453 | is not available at all. */ |
| 454 | errval = EAGAIN; |
| 455 | break; |
| 456 | } |
| 457 | use_malloc = true; |
| 458 | } |
| 459 | else |
| 460 | /* Allocate a new buffer on the stack. If possible combine it |
| 461 | with the previously allocated buffer. */ |
| 462 | buffer = (char *) extend_alloca (buffer, buflen, 2 * buflen); |
| 463 | } |
| 464 | |
| 465 | /* Add the entry to the cache. */ |
| 466 | time_t timeout = cache_addpw (db, fd, req, keystr, pwd, c_uid, he, dh, |
| 467 | errval); |
| 468 | |
| 469 | if (use_malloc) |
| 470 | free (buffer); |
| 471 | |
| 472 | return timeout; |
| 473 | } |
| 474 | |
| 475 | |
| 476 | void |
| 477 | addpwbyname (struct database_dyn *db, int fd, request_header *req, |
| 478 | void *key, uid_t c_uid) |
| 479 | { |
| 480 | union keytype u = { .v = key }; |
| 481 | |
| 482 | addpwbyX (db, fd, req, u, key, c_uid, NULL, NULL); |
| 483 | } |
| 484 | |
| 485 | |
| 486 | time_t |
| 487 | readdpwbyname (struct database_dyn *db, struct hashentry *he, |
| 488 | struct datahead *dh) |
| 489 | { |
| 490 | request_header req = |
| 491 | { |
| 492 | .type = GETPWBYNAME, |
| 493 | .key_len = he->len |
| 494 | }; |
| 495 | union keytype u = { .v = db->data + he->key }; |
| 496 | |
| 497 | return addpwbyX (db, -1, &req, u, db->data + he->key, he->owner, he, dh); |
| 498 | } |
| 499 | |
| 500 | |
| 501 | void |
| 502 | addpwbyuid (struct database_dyn *db, int fd, request_header *req, |
| 503 | void *key, uid_t c_uid) |
| 504 | { |
| 505 | char *ep; |
| 506 | uid_t uid = strtoul ((char *) key, &ep, 10); |
| 507 | |
| 508 | if (*(char *) key == '\0' || *ep != '\0') /* invalid numeric uid */ |
| 509 | { |
| 510 | if (debug_level > 0) |
| 511 | dbg_log (_("Invalid numeric uid \"%s\"!"), (char *) key); |
| 512 | |
| 513 | errno = EINVAL; |
| 514 | return; |
| 515 | } |
| 516 | |
| 517 | union keytype u = { .u = uid }; |
| 518 | |
| 519 | addpwbyX (db, fd, req, u, key, c_uid, NULL, NULL); |
| 520 | } |
| 521 | |
| 522 | |
| 523 | time_t |
| 524 | readdpwbyuid (struct database_dyn *db, struct hashentry *he, |
| 525 | struct datahead *dh) |
| 526 | { |
| 527 | char *ep; |
| 528 | uid_t uid = strtoul (db->data + he->key, &ep, 10); |
| 529 | |
| 530 | /* Since the key has been added before it must be OK. */ |
| 531 | assert (*(db->data + he->key) != '\0' && *ep == '\0'); |
| 532 | |
| 533 | request_header req = |
| 534 | { |
| 535 | .type = GETPWBYUID, |
| 536 | .key_len = he->len |
| 537 | }; |
| 538 | union keytype u = { .u = uid }; |
| 539 | |
| 540 | return addpwbyX (db, -1, &req, u, db->data + he->key, he->owner, he, dh); |
| 541 | } |