1 /* $NetBSD: hesiod.c,v 1.25 2011/01/05 00:09:43 wiz Exp $ */ 2 3 /* Copyright (c) 1996 by Internet Software Consortium. 4 * 5 * Permission to use, copy, modify, and distribute this software for any 6 * purpose with or without fee is hereby granted, provided that the above 7 * copyright notice and this permission notice appear in all copies. 8 * 9 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS 10 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES 11 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE 12 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL 13 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR 14 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS 15 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS 16 * SOFTWARE. 17 */ 18 19 /* Copyright 1996 by the Massachusetts Institute of Technology. 20 * 21 * Permission to use, copy, modify, and distribute this 22 * software and its documentation for any purpose and without 23 * fee is hereby granted, provided that the above copyright 24 * notice appear in all copies and that both that copyright 25 * notice and this permission notice appear in supporting 26 * documentation, and that the name of M.I.T. not be used in 27 * advertising or publicity pertaining to distribution of the 28 * software without specific, written prior permission. 29 * M.I.T. makes no representations about the suitability of 30 * this software for any purpose. It is provided "as is" 31 * without express or implied warranty. 32 */ 33 34 /* This file is part of the hesiod library. It implements the core 35 * portion of the hesiod resolver. 36 * 37 * This file is loosely based on an interim version of hesiod.c from 38 * the BIND IRS library, which was in turn based on an earlier version 39 * of this file. Extensive changes have been made on each step of the 40 * path. 41 * 42 * This implementation is thread-safe because it uses res_nsend(). 43 */ 44 45 #include <sys/cdefs.h> 46 47 #if defined(LIBC_SCCS) && !defined(lint) 48 __IDSTRING(rcsid_hesiod_c, 49 "#Id: hesiod.c,v 1.18.2.1 1997/01/03 20:48:20 ghudson Exp #"); 50 __IDSTRING(rcsid_hesiod_p_h, 51 "#Id: hesiod_p.h,v 1.1 1996/12/08 21:39:37 ghudson Exp #"); 52 __IDSTRING(rcsid_hescompat_c, 53 "#Id: hescompat.c,v 1.1.2.1 1996/12/16 08:37:45 ghudson Exp #"); 54 __RCSID("$NetBSD: hesiod.c,v 1.25 2011/01/05 00:09:43 wiz Exp $"); 55 #endif /* LIBC_SCCS and not lint */ 56 57 #include "namespace.h" 58 59 #include <sys/types.h> 60 #include <sys/param.h> 61 #include <netinet/in.h> 62 #include <arpa/nameser.h> 63 64 #include <assert.h> 65 #include <ctype.h> 66 #include <errno.h> 67 #include <hesiod.h> 68 #include <resolv.h> 69 #include <stdio.h> 70 #include <stdlib.h> 71 #include <string.h> 72 #include <unistd.h> 73 74 #ifdef __weak_alias 75 __weak_alias(hesiod_init,_hesiod_init) 76 __weak_alias(hesiod_end,_hesiod_end) 77 __weak_alias(hesiod_to_bind,_hesiod_to_bind) 78 __weak_alias(hesiod_resolve,_hesiod_resolve) 79 __weak_alias(hesiod_free_list,_hesiod_free_list) 80 __weak_alias(hes_init,_hes_init) 81 __weak_alias(hes_to_bind,_hes_to_bind) 82 __weak_alias(hes_resolve,_hes_resolve) 83 __weak_alias(hes_error,_hes_error) 84 __weak_alias(hes_free,_hes_free) 85 #endif 86 87 struct hesiod_p { 88 char *lhs; /* normally ".ns" */ 89 char *rhs; /* AKA the default hesiod domain */ 90 int classes[2]; /* The class search order. */ 91 }; 92 93 #define MAX_HESRESP 1024 94 95 static int read_config_file __P((struct hesiod_p *, const char *)); 96 static char **get_txt_records __P((int, const char *)); 97 static int init_context __P((void)); 98 static void translate_errors __P((void)); 99 100 101 /* 102 * hesiod_init -- 103 * initialize a hesiod_p. 104 */ 105 int 106 hesiod_init(context) 107 void **context; 108 { 109 struct hesiod_p *ctx; 110 const char *p, *configname; 111 int serrno; 112 113 _DIAGASSERT(context != NULL); 114 115 ctx = calloc(1, sizeof(struct hesiod_p)); 116 if (ctx) { 117 *context = ctx; 118 /* 119 * don't permit overrides from environment 120 * for set.id programs 121 */ 122 if (issetugid()) 123 configname = NULL; 124 else 125 configname = getenv("HESIOD_CONFIG"); 126 if (!configname) 127 configname = _PATH_HESIOD_CONF; 128 if (read_config_file(ctx, configname) >= 0) { 129 /* 130 * The default rhs can be overridden by an 131 * environment variable, unless set.id. 132 */ 133 if (issetugid()) 134 p = NULL; 135 else 136 p = getenv("HES_DOMAIN"); 137 if (p) { 138 if (ctx->rhs) 139 free(ctx->rhs); 140 ctx->rhs = malloc(strlen(p) + 2); 141 if (ctx->rhs) { 142 *ctx->rhs = '.'; 143 strcpy(ctx->rhs + 1, 144 (*p == '.') ? p + 1 : p); 145 return 0; 146 } else 147 errno = ENOMEM; 148 } else 149 return 0; 150 } 151 } else 152 errno = ENOMEM; 153 154 serrno = errno; 155 if (ctx) { 156 if (ctx->lhs) 157 free(ctx->lhs); 158 if (ctx->rhs) 159 free(ctx->rhs); 160 free(ctx); 161 } 162 errno = serrno; 163 return -1; 164 } 165 166 /* 167 * hesiod_end -- 168 * Deallocates the hesiod_p. 169 */ 170 void 171 hesiod_end(context) 172 void *context; 173 { 174 struct hesiod_p *ctx = (struct hesiod_p *) context; 175 176 _DIAGASSERT(context != NULL); 177 178 free(ctx->rhs); 179 if (ctx->lhs) 180 free(ctx->lhs); 181 free(ctx); 182 } 183 184 /* 185 * hesiod_to_bind -- 186 * takes a hesiod (name, type) and returns a DNS 187 * name which is to be resolved. 188 */ 189 char * 190 hesiod_to_bind(void *context, const char *name, const char *type) 191 { 192 struct hesiod_p *ctx = (struct hesiod_p *) context; 193 char bindname[MAXDNAME], *p, *ret, **rhs_list = NULL; 194 const char *rhs; 195 size_t len; 196 197 _DIAGASSERT(context != NULL); 198 _DIAGASSERT(name != NULL); 199 _DIAGASSERT(type != NULL); 200 201 if (strlcpy(bindname, name, sizeof(bindname)) >= sizeof(bindname)) { 202 errno = EMSGSIZE; 203 return NULL; 204 } 205 206 /* 207 * Find the right right hand side to use, possibly 208 * truncating bindname. 209 */ 210 p = strchr(bindname, '@'); 211 if (p) { 212 *p++ = 0; 213 if (strchr(p, '.')) 214 rhs = name + (p - bindname); 215 else { 216 rhs_list = hesiod_resolve(context, p, "rhs-extension"); 217 if (rhs_list) 218 rhs = *rhs_list; 219 else { 220 errno = ENOENT; 221 return NULL; 222 } 223 } 224 } else 225 rhs = ctx->rhs; 226 227 /* See if we have enough room. */ 228 len = strlen(bindname) + 1 + strlen(type); 229 if (ctx->lhs) 230 len += strlen(ctx->lhs) + ((ctx->lhs[0] != '.') ? 1 : 0); 231 len += strlen(rhs) + ((rhs[0] != '.') ? 1 : 0); 232 if (len > sizeof(bindname) - 1) { 233 if (rhs_list) 234 hesiod_free_list(context, rhs_list); 235 errno = EMSGSIZE; 236 return NULL; 237 } 238 /* Put together the rest of the domain. */ 239 strlcat(bindname, ".", sizeof(bindname)); 240 strlcat(bindname, type, sizeof(bindname)); 241 /* Only append lhs if it isn't empty. */ 242 if (ctx->lhs && ctx->lhs[0] != '\0' ) { 243 if (ctx->lhs[0] != '.') 244 strlcat(bindname, ".", sizeof(bindname)); 245 strlcat(bindname, ctx->lhs, sizeof(bindname)); 246 } 247 if (rhs[0] != '.') 248 strlcat(bindname, ".", sizeof(bindname)); 249 strlcat(bindname, rhs, sizeof(bindname)); 250 251 /* rhs_list is no longer needed, since we're done with rhs. */ 252 if (rhs_list) 253 hesiod_free_list(context, rhs_list); 254 255 /* Make a copy of the result and return it to the caller. */ 256 ret = strdup(bindname); 257 if (ret == NULL) 258 errno = ENOMEM; 259 return ret; 260 } 261 262 /* 263 * hesiod_resolve -- 264 * Given a hesiod name and type, return an array of strings returned 265 * by the resolver. 266 */ 267 char ** 268 hesiod_resolve(context, name, type) 269 void *context; 270 const char *name; 271 const char *type; 272 { 273 struct hesiod_p *ctx = (struct hesiod_p *) context; 274 char *bindname, **retvec; 275 276 _DIAGASSERT(context != NULL); 277 _DIAGASSERT(name != NULL); 278 _DIAGASSERT(type != NULL); 279 280 bindname = hesiod_to_bind(context, name, type); 281 if (!bindname) 282 return NULL; 283 284 retvec = get_txt_records(ctx->classes[0], bindname); 285 if (retvec == NULL && errno == ENOENT && ctx->classes[1]) 286 retvec = get_txt_records(ctx->classes[1], bindname); 287 288 free(bindname); 289 return retvec; 290 } 291 292 /*ARGSUSED*/ 293 void 294 hesiod_free_list(context, list) 295 void *context; 296 char **list; 297 { 298 char **p; 299 300 _DIAGASSERT(context != NULL); 301 302 if (list == NULL) 303 return; 304 for (p = list; *p; p++) 305 free(*p); 306 free(list); 307 } 308 309 310 /* read_config_file -- 311 * Parse the /etc/hesiod.conf file. Returns 0 on success, 312 * -1 on failure. On failure, it might leave values in ctx->lhs 313 * or ctx->rhs which need to be freed by the caller. 314 */ 315 static int 316 read_config_file(ctx, filename) 317 struct hesiod_p *ctx; 318 const char *filename; 319 { 320 char *key, *data, *p, **which; 321 char buf[MAXDNAME + 7]; 322 int n; 323 FILE *fp; 324 325 _DIAGASSERT(ctx != NULL); 326 _DIAGASSERT(filename != NULL); 327 328 /* Set default query classes. */ 329 ctx->classes[0] = C_IN; 330 ctx->classes[1] = C_HS; 331 332 /* Try to open the configuration file. */ 333 fp = fopen(filename, "r"); 334 if (!fp) { 335 /* Use compiled in default domain names. */ 336 ctx->lhs = strdup(DEF_LHS); 337 ctx->rhs = strdup(DEF_RHS); 338 if (ctx->lhs && ctx->rhs) 339 return 0; 340 else { 341 errno = ENOMEM; 342 return -1; 343 } 344 } 345 ctx->lhs = NULL; 346 ctx->rhs = NULL; 347 while (fgets(buf, sizeof(buf), fp) != NULL) { 348 p = buf; 349 if (*p == '#' || *p == '\n' || *p == '\r') 350 continue; 351 while (*p == ' ' || *p == '\t') 352 p++; 353 key = p; 354 while (*p != ' ' && *p != '\t' && *p != '=' && *p) 355 p++; 356 357 if (*p == '\0') 358 continue; 359 360 *p++ = 0; 361 362 while (isspace((u_char) *p) || *p == '=') 363 p++; 364 365 if (*p == '\0') 366 continue; 367 368 data = p; 369 while (!isspace((u_char) *p) && *p) 370 p++; 371 372 *p = 0; 373 374 if (strcasecmp(key, "lhs") == 0 || 375 strcasecmp(key, "rhs") == 0) { 376 which = (strcasecmp(key, "lhs") == 0) 377 ? &ctx->lhs : &ctx->rhs; 378 *which = strdup(data); 379 if (!*which) { 380 errno = ENOMEM; 381 (void)fclose(fp); 382 return -1; 383 } 384 } else { 385 if (strcasecmp(key, "classes") == 0) { 386 n = 0; 387 while (*data && n < 2) { 388 p = data; 389 while (*p && *p != ',') 390 p++; 391 if (*p) 392 *p++ = 0; 393 if (strcasecmp(data, "IN") == 0) 394 ctx->classes[n++] = C_IN; 395 else 396 if (strcasecmp(data, "HS") == 0) 397 ctx->classes[n++] = 398 C_HS; 399 data = p; 400 } 401 while (n < 2) 402 ctx->classes[n++] = 0; 403 } 404 } 405 } 406 fclose(fp); 407 408 if (!ctx->rhs || ctx->classes[0] == 0 || 409 ctx->classes[0] == ctx->classes[1]) { 410 errno = ENOEXEC; 411 return -1; 412 } 413 return 0; 414 } 415 416 /* 417 * get_txt_records -- 418 * Given a DNS class and a DNS name, do a lookup for TXT records, and 419 * return a list of them. 420 */ 421 static char ** 422 get_txt_records(qclass, name) 423 int qclass; 424 const char *name; 425 { 426 HEADER *hp; 427 unsigned char qbuf[PACKETSZ], abuf[MAX_HESRESP], *p, *eom, *eor; 428 char *dst, **list; 429 int ancount, qdcount, i, j, n, skip, type, class, len; 430 res_state res = __res_get_state(); 431 432 if (res == NULL) 433 return NULL; 434 435 _DIAGASSERT(name != NULL); 436 437 /* Construct the query. */ 438 n = res_nmkquery(res, QUERY, name, qclass, T_TXT, NULL, 0, 439 NULL, qbuf, PACKETSZ); 440 if (n < 0) { 441 errno = EMSGSIZE; 442 __res_put_state(res); 443 return NULL; 444 } 445 446 /* Send the query. */ 447 n = res_nsend(res, qbuf, n, abuf, MAX_HESRESP); 448 __res_put_state(res); 449 if (n < 0) { 450 errno = ECONNREFUSED; 451 return NULL; 452 } 453 /* Parse the header of the result. */ 454 hp = (HEADER *) (void *) abuf; 455 ancount = ntohs(hp->ancount); 456 qdcount = ntohs(hp->qdcount); 457 p = abuf + sizeof(HEADER); 458 eom = abuf + n; 459 460 /* 461 * Skip questions, trying to get to the answer section 462 * which follows. 463 */ 464 for (i = 0; i < qdcount; i++) { 465 skip = dn_skipname(p, eom); 466 if (skip < 0 || p + skip + QFIXEDSZ > eom) { 467 errno = EMSGSIZE; 468 return NULL; 469 } 470 p += skip + QFIXEDSZ; 471 } 472 473 /* Allocate space for the text record answers. */ 474 list = malloc((ancount + 1) * sizeof(char *)); 475 if (!list) { 476 errno = ENOMEM; 477 return NULL; 478 } 479 /* Parse the answers. */ 480 j = 0; 481 for (i = 0; i < ancount; i++) { 482 /* Parse the header of this answer. */ 483 skip = dn_skipname(p, eom); 484 if (skip < 0 || p + skip + 10 > eom) 485 break; 486 type = p[skip + 0] << 8 | p[skip + 1]; 487 class = p[skip + 2] << 8 | p[skip + 3]; 488 len = p[skip + 8] << 8 | p[skip + 9]; 489 p += skip + 10; 490 if (p + len > eom) { 491 errno = EMSGSIZE; 492 break; 493 } 494 /* Skip entries of the wrong class and type. */ 495 if (class != qclass || type != T_TXT) { 496 p += len; 497 continue; 498 } 499 /* Allocate space for this answer. */ 500 list[j] = malloc((size_t)len); 501 if (!list[j]) { 502 errno = ENOMEM; 503 break; 504 } 505 dst = list[j++]; 506 507 /* Copy answer data into the allocated area. */ 508 eor = p + len; 509 while (p < eor) { 510 n = (unsigned char) *p++; 511 if (p + n > eor) { 512 errno = EMSGSIZE; 513 break; 514 } 515 memcpy(dst, p, (size_t)n); 516 p += n; 517 dst += n; 518 } 519 if (p < eor) { 520 errno = EMSGSIZE; 521 break; 522 } 523 *dst = 0; 524 } 525 526 /* 527 * If we didn't terminate the loop normally, something 528 * went wrong. 529 */ 530 if (i < ancount) { 531 for (i = 0; i < j; i++) 532 free(list[i]); 533 free(list); 534 return NULL; 535 } 536 if (j == 0) { 537 errno = ENOENT; 538 free(list); 539 return NULL; 540 } 541 list[j] = NULL; 542 return list; 543 } 544 545 /* 546 * COMPATIBILITY FUNCTIONS 547 */ 548 549 static int inited = 0; 550 static void *context; 551 static int errval = HES_ER_UNINIT; 552 553 int 554 hes_init() 555 { 556 init_context(); 557 return errval; 558 } 559 560 char * 561 hes_to_bind(name, type) 562 const char *name; 563 const char *type; 564 { 565 static char *bindname; 566 567 _DIAGASSERT(name != NULL); 568 _DIAGASSERT(type != NULL); 569 570 if (init_context() < 0) 571 return NULL; 572 if (bindname) 573 free(bindname); 574 bindname = hesiod_to_bind(context, name, type); 575 if (!bindname) 576 translate_errors(); 577 return bindname; 578 } 579 580 char ** 581 hes_resolve(name, type) 582 const char *name; 583 const char *type; 584 { 585 static char **list; 586 587 _DIAGASSERT(name != NULL); 588 _DIAGASSERT(type != NULL); 589 590 if (init_context() < 0) 591 return NULL; 592 593 /* 594 * In the old Hesiod interface, the caller was responsible for 595 * freeing the returned strings but not the vector of strings itself. 596 */ 597 if (list) 598 free(list); 599 600 list = hesiod_resolve(context, name, type); 601 if (!list) 602 translate_errors(); 603 return list; 604 } 605 606 int 607 hes_error() 608 { 609 return errval; 610 } 611 612 void 613 hes_free(hp) 614 char **hp; 615 { 616 hesiod_free_list(context, hp); 617 } 618 619 static int 620 init_context() 621 { 622 if (!inited) { 623 inited = 1; 624 if (hesiod_init(&context) < 0) { 625 errval = HES_ER_CONFIG; 626 return -1; 627 } 628 errval = HES_ER_OK; 629 } 630 return 0; 631 } 632 633 static void 634 translate_errors() 635 { 636 switch (errno) { 637 case ENOENT: 638 errval = HES_ER_NOTFOUND; 639 break; 640 case ECONNREFUSED: 641 case EMSGSIZE: 642 errval = HES_ER_NET; 643 break; 644 default: 645 /* Not a good match, but the best we can do. */ 646 errval = HES_ER_CONFIG; 647 break; 648 } 649 } 650