1 /* $NetBSD: hesiod.c,v 1.16 2001/02/13 15:41:18 sommerfeld 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 not truly thread-safe at the moment because 43 * it uses res_send() and accesses _res. 44 */ 45 46 #include <sys/cdefs.h> 47 48 #if defined(LIBC_SCCS) && !defined(lint) 49 __IDSTRING(rcsid_hesiod_c, 50 "#Id: hesiod.c,v 1.18.2.1 1997/01/03 20:48:20 ghudson Exp #"); 51 __IDSTRING(rcsid_hesiod_p_h, 52 "#Id: hesiod_p.h,v 1.1 1996/12/08 21:39:37 ghudson Exp #"); 53 __IDSTRING(rcsid_hescompat_c, 54 "#Id: hescompat.c,v 1.1.2.1 1996/12/16 08:37:45 ghudson Exp #"); 55 __RCSID("$NetBSD: hesiod.c,v 1.16 2001/02/13 15:41:18 sommerfeld Exp $"); 56 #endif /* LIBC_SCCS and not lint */ 57 58 #include "namespace.h" 59 60 #include <sys/types.h> 61 #include <sys/param.h> 62 #include <netinet/in.h> 63 #include <arpa/nameser.h> 64 65 #include <assert.h> 66 #include <ctype.h> 67 #include <errno.h> 68 #include <hesiod.h> 69 #include <resolv.h> 70 #include <stdio.h> 71 #include <stdlib.h> 72 #include <string.h> 73 #include <unistd.h> 74 75 #ifdef __weak_alias 76 __weak_alias(hesiod_init,_hesiod_init) 77 __weak_alias(hesiod_end,_hesiod_end) 78 __weak_alias(hesiod_to_bind,_hesiod_to_bind) 79 __weak_alias(hesiod_resolve,_hesiod_resolve) 80 __weak_alias(hesiod_free_list,_hesiod_free_list) 81 __weak_alias(hes_init,_hes_init) 82 __weak_alias(hes_to_bind,_hes_to_bind) 83 __weak_alias(hes_resolve,_hes_resolve) 84 __weak_alias(hes_error,_hes_error) 85 __weak_alias(hes_free,_hes_free) 86 #endif 87 88 struct hesiod_p { 89 char *lhs; /* normally ".ns" */ 90 char *rhs; /* AKA the default hesiod domain */ 91 int classes[2]; /* The class search order. */ 92 }; 93 94 #define MAX_HESRESP 1024 95 96 static int read_config_file __P((struct hesiod_p *, const char *)); 97 static char **get_txt_records __P((int, const char *)); 98 static int init_context __P((void)); 99 static void translate_errors __P((void)); 100 101 102 /* 103 * hesiod_init -- 104 * initialize a hesiod_p. 105 */ 106 int 107 hesiod_init(context) 108 void **context; 109 { 110 struct hesiod_p *ctx; 111 const char *p, *configname; 112 int serrno; 113 114 _DIAGASSERT(context != NULL); 115 116 ctx = malloc(sizeof(struct hesiod_p)); 117 if (ctx) { 118 *context = ctx; 119 /* 120 * don't permit overrides from environment 121 * for set.id programs 122 */ 123 if (issetugid()) 124 configname = NULL; 125 else 126 configname = getenv("HESIOD_CONFIG"); 127 if (!configname) 128 configname = _PATH_HESIOD_CONF; 129 if (read_config_file(ctx, configname) >= 0) { 130 /* 131 * The default rhs can be overridden by an 132 * environment variable, unless set.id. 133 */ 134 if (issetugid()) 135 p = NULL; 136 else 137 p = getenv("HES_DOMAIN"); 138 if (p) { 139 if (ctx->rhs) 140 free(ctx->rhs); 141 ctx->rhs = malloc(strlen(p) + 2); 142 if (ctx->rhs) { 143 *ctx->rhs = '.'; 144 strcpy(ctx->rhs + 1, 145 (*p == '.') ? p + 1 : p); 146 return 0; 147 } else 148 errno = ENOMEM; 149 } else 150 return 0; 151 } 152 } else 153 errno = ENOMEM; 154 155 serrno = errno; 156 if (ctx->lhs) 157 free(ctx->lhs); 158 if (ctx->rhs) 159 free(ctx->rhs); 160 if (ctx) 161 free(ctx); 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 int 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 strcat(bindname, "."); 240 strcat(bindname, type); 241 /* Only append lhs if it isn't empty. */ 242 if (ctx->lhs && ctx->lhs[0] != '\0' ) { 243 if (ctx->lhs[0] != '.') 244 strcat(bindname, "."); 245 strcat(bindname, ctx->lhs); 246 } 247 if (rhs[0] != '.') 248 strcat(bindname, "."); 249 strcat(bindname, rhs); 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) 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 != '=') 355 p++; 356 *p++ = 0; 357 358 while (isspace((u_char) *p) || *p == '=') 359 p++; 360 data = p; 361 while (!isspace((u_char) *p)) 362 p++; 363 *p = 0; 364 365 if (strcasecmp(key, "lhs") == 0 || 366 strcasecmp(key, "rhs") == 0) { 367 which = (strcasecmp(key, "lhs") == 0) 368 ? &ctx->lhs : &ctx->rhs; 369 *which = strdup(data); 370 if (!*which) { 371 errno = ENOMEM; 372 return -1; 373 } 374 } else { 375 if (strcasecmp(key, "classes") == 0) { 376 n = 0; 377 while (*data && n < 2) { 378 p = data; 379 while (*p && *p != ',') 380 p++; 381 if (*p) 382 *p++ = 0; 383 if (strcasecmp(data, "IN") == 0) 384 ctx->classes[n++] = C_IN; 385 else 386 if (strcasecmp(data, "HS") == 0) 387 ctx->classes[n++] = 388 C_HS; 389 data = p; 390 } 391 while (n < 2) 392 ctx->classes[n++] = 0; 393 } 394 } 395 } 396 fclose(fp); 397 398 if (!ctx->rhs || ctx->classes[0] == 0 || 399 ctx->classes[0] == ctx->classes[1]) { 400 errno = ENOEXEC; 401 return -1; 402 } 403 return 0; 404 } 405 406 /* 407 * get_txt_records -- 408 * Given a DNS class and a DNS name, do a lookup for TXT records, and 409 * return a list of them. 410 */ 411 static char ** 412 get_txt_records(qclass, name) 413 int qclass; 414 const char *name; 415 { 416 HEADER *hp; 417 unsigned char qbuf[PACKETSZ], abuf[MAX_HESRESP], *p, *eom, *eor; 418 char *dst, **list; 419 int ancount, qdcount, i, j, n, skip, type, class, len; 420 421 _DIAGASSERT(name != NULL); 422 423 /* Make sure the resolver is initialized. */ 424 if ((_res.options & RES_INIT) == 0 && res_init() == -1) 425 return NULL; 426 427 /* Construct the query. */ 428 n = res_mkquery(QUERY, name, qclass, T_TXT, NULL, 0, 429 NULL, qbuf, PACKETSZ); 430 if (n < 0) { 431 errno = EMSGSIZE; 432 return NULL; 433 } 434 435 /* Send the query. */ 436 n = res_send(qbuf, n, abuf, MAX_HESRESP); 437 if (n < 0) { 438 errno = ECONNREFUSED; 439 return NULL; 440 } 441 /* Parse the header of the result. */ 442 hp = (HEADER *) (void *) abuf; 443 ancount = ntohs(hp->ancount); 444 qdcount = ntohs(hp->qdcount); 445 p = abuf + sizeof(HEADER); 446 eom = abuf + n; 447 448 /* 449 * Skip questions, trying to get to the answer section 450 * which follows. 451 */ 452 for (i = 0; i < qdcount; i++) { 453 skip = dn_skipname(p, eom); 454 if (skip < 0 || p + skip + QFIXEDSZ > eom) { 455 errno = EMSGSIZE; 456 return NULL; 457 } 458 p += skip + QFIXEDSZ; 459 } 460 461 /* Allocate space for the text record answers. */ 462 list = malloc((ancount + 1) * sizeof(char *)); 463 if (!list) { 464 errno = ENOMEM; 465 return NULL; 466 } 467 /* Parse the answers. */ 468 j = 0; 469 for (i = 0; i < ancount; i++) { 470 /* Parse the header of this answer. */ 471 skip = dn_skipname(p, eom); 472 if (skip < 0 || p + skip + 10 > eom) 473 break; 474 type = p[skip + 0] << 8 | p[skip + 1]; 475 class = p[skip + 2] << 8 | p[skip + 3]; 476 len = p[skip + 8] << 8 | p[skip + 9]; 477 p += skip + 10; 478 if (p + len > eom) { 479 errno = EMSGSIZE; 480 break; 481 } 482 /* Skip entries of the wrong class and type. */ 483 if (class != qclass || type != T_TXT) { 484 p += len; 485 continue; 486 } 487 /* Allocate space for this answer. */ 488 list[j] = malloc((size_t)len); 489 if (!list[j]) { 490 errno = ENOMEM; 491 break; 492 } 493 dst = list[j++]; 494 495 /* Copy answer data into the allocated area. */ 496 eor = p + len; 497 while (p < eor) { 498 n = (unsigned char) *p++; 499 if (p + n > eor) { 500 errno = EMSGSIZE; 501 break; 502 } 503 memcpy(dst, p, (size_t)n); 504 p += n; 505 dst += n; 506 } 507 if (p < eor) { 508 errno = EMSGSIZE; 509 break; 510 } 511 *dst = 0; 512 } 513 514 /* 515 * If we didn't terminate the loop normally, something 516 * went wrong. 517 */ 518 if (i < ancount) { 519 for (i = 0; i < j; i++) 520 free(list[i]); 521 free(list); 522 return NULL; 523 } 524 if (j == 0) { 525 errno = ENOENT; 526 free(list); 527 return NULL; 528 } 529 list[j] = NULL; 530 return list; 531 } 532 533 /* 534 * COMPATIBILITY FUNCTIONS 535 */ 536 537 static int inited = 0; 538 static void *context; 539 static int errval = HES_ER_UNINIT; 540 541 int 542 hes_init() 543 { 544 init_context(); 545 return errval; 546 } 547 548 char * 549 hes_to_bind(name, type) 550 const char *name; 551 const char *type; 552 { 553 static char *bindname; 554 555 _DIAGASSERT(name != NULL); 556 _DIAGASSERT(type != NULL); 557 558 if (init_context() < 0) 559 return NULL; 560 if (bindname) 561 free(bindname); 562 bindname = hesiod_to_bind(context, name, type); 563 if (!bindname) 564 translate_errors(); 565 return bindname; 566 } 567 568 char ** 569 hes_resolve(name, type) 570 const char *name; 571 const char *type; 572 { 573 static char **list; 574 575 _DIAGASSERT(name != NULL); 576 _DIAGASSERT(type != NULL); 577 578 if (init_context() < 0) 579 return NULL; 580 581 /* 582 * In the old Hesiod interface, the caller was responsible for 583 * freeing the returned strings but not the vector of strings itself. 584 */ 585 if (list) 586 free(list); 587 588 list = hesiod_resolve(context, name, type); 589 if (!list) 590 translate_errors(); 591 return list; 592 } 593 594 int 595 hes_error() 596 { 597 return errval; 598 } 599 600 void 601 hes_free(hp) 602 char **hp; 603 { 604 hesiod_free_list(context, hp); 605 } 606 607 static int 608 init_context() 609 { 610 if (!inited) { 611 inited = 1; 612 if (hesiod_init(&context) < 0) { 613 errval = HES_ER_CONFIG; 614 return -1; 615 } 616 errval = HES_ER_OK; 617 } 618 return 0; 619 } 620 621 static void 622 translate_errors() 623 { 624 switch (errno) { 625 case ENOENT: 626 errval = HES_ER_NOTFOUND; 627 break; 628 case ECONNREFUSED: 629 case EMSGSIZE: 630 errval = HES_ER_NET; 631 break; 632 case EFAULT: 633 case ENOMEM: 634 default: 635 /* Not a good match, but the best we can do. */ 636 errval = HES_ER_CONFIG; 637 break; 638 } 639 } 640