1 /* $NetBSD: hesiod.c,v 1.9 1999/02/11 06:16:38 simonb 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 1.9 1999/02/11 06:16:38 simonb 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 <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 73 #ifdef __weak_alias 74 __weak_alias(hesiod_init,_hesiod_init); 75 __weak_alias(hesiod_end,_hesiod_end); 76 __weak_alias(hesiod_to_bind,_hesiod_to_bind); 77 __weak_alias(hesiod_resolve,_hesiod_resolve); 78 __weak_alias(hesiod_free_list,_hesiod_free_list); 79 __weak_alias(hes_init,_hes_init); 80 __weak_alias(hes_to_bind,_hes_to_bind); 81 __weak_alias(hes_resolve,_hes_resolve); 82 __weak_alias(hes_error,_hes_error); 83 __weak_alias(hes_free,_hes_free); 84 #endif 85 86 struct hesiod_p { 87 char *lhs; /* normally ".ns" */ 88 char *rhs; /* AKA the default hesiod domain */ 89 int classes[2]; /* The class search order. */ 90 }; 91 92 #define MAX_HESRESP 1024 93 94 static int read_config_file __P((struct hesiod_p *, const char *)); 95 static char **get_txt_records __P((int, const char *)); 96 static int init_context __P((void)); 97 static void translate_errors __P((void)); 98 99 100 /* 101 * hesiod_init -- 102 * initialize a hesiod_p. 103 */ 104 int 105 hesiod_init(context) 106 void **context; 107 { 108 struct hesiod_p *ctx; 109 const char *p, *configname; 110 111 ctx = malloc(sizeof(struct hesiod_p)); 112 if (ctx) { 113 *context = ctx; 114 configname = getenv("HESIOD_CONFIG"); 115 if (!configname) 116 configname = _PATH_HESIOD_CONF; 117 if (read_config_file(ctx, configname) >= 0) { 118 /* 119 * The default rhs can be overridden by an 120 * environment variable. 121 */ 122 p = getenv("HES_DOMAIN"); 123 if (p) { 124 if (ctx->rhs) 125 free(ctx->rhs); 126 ctx->rhs = malloc(strlen(p) + 2); 127 if (ctx->rhs) { 128 *ctx->rhs = '.'; 129 strcpy(ctx->rhs + 1, 130 (*p == '.') ? p + 1 : p); 131 return 0; 132 } else 133 errno = ENOMEM; 134 } else 135 return 0; 136 } 137 } else 138 errno = ENOMEM; 139 140 if (ctx->lhs) 141 free(ctx->lhs); 142 if (ctx->rhs) 143 free(ctx->rhs); 144 if (ctx) 145 free(ctx); 146 return -1; 147 } 148 149 /* 150 * hesiod_end -- 151 * Deallocates the hesiod_p. 152 */ 153 void 154 hesiod_end(context) 155 void *context; 156 { 157 struct hesiod_p *ctx = (struct hesiod_p *) context; 158 159 free(ctx->rhs); 160 if (ctx->lhs) 161 free(ctx->lhs); 162 free(ctx); 163 } 164 165 /* 166 * hesiod_to_bind -- 167 * takes a hesiod (name, type) and returns a DNS 168 * name which is to be resolved. 169 */ 170 char * 171 hesiod_to_bind(void *context, const char *name, const char *type) 172 { 173 struct hesiod_p *ctx = (struct hesiod_p *) context; 174 char bindname[MAXDNAME], *p, *ret, **rhs_list = NULL; 175 const char *rhs; 176 int len; 177 178 strcpy(bindname, name); 179 180 /* 181 * Find the right right hand side to use, possibly 182 * truncating bindname. 183 */ 184 p = strchr(bindname, '@'); 185 if (p) { 186 *p++ = 0; 187 if (strchr(p, '.')) 188 rhs = name + (p - bindname); 189 else { 190 rhs_list = hesiod_resolve(context, p, "rhs-extension"); 191 if (rhs_list) 192 rhs = *rhs_list; 193 else { 194 errno = ENOENT; 195 return NULL; 196 } 197 } 198 } else 199 rhs = ctx->rhs; 200 201 /* See if we have enough room. */ 202 len = strlen(bindname) + 1 + strlen(type); 203 if (ctx->lhs) 204 len += strlen(ctx->lhs) + ((ctx->lhs[0] != '.') ? 1 : 0); 205 len += strlen(rhs) + ((rhs[0] != '.') ? 1 : 0); 206 if (len > sizeof(bindname) - 1) { 207 if (rhs_list) 208 hesiod_free_list(context, rhs_list); 209 errno = EMSGSIZE; 210 return NULL; 211 } 212 /* Put together the rest of the domain. */ 213 strcat(bindname, "."); 214 strcat(bindname, type); 215 /* Only append lhs if it isn't empty. */ 216 if (ctx->lhs && ctx->lhs[0] != '\0' ) { 217 if (ctx->lhs[0] != '.') 218 strcat(bindname, "."); 219 strcat(bindname, ctx->lhs); 220 } 221 if (rhs[0] != '.') 222 strcat(bindname, "."); 223 strcat(bindname, rhs); 224 225 /* rhs_list is no longer needed, since we're done with rhs. */ 226 if (rhs_list) 227 hesiod_free_list(context, rhs_list); 228 229 /* Make a copy of the result and return it to the caller. */ 230 ret = strdup(bindname); 231 if (!ret) 232 errno = ENOMEM; 233 return ret; 234 } 235 236 /* 237 * hesiod_resolve -- 238 * Given a hesiod name and type, return an array of strings returned 239 * by the resolver. 240 */ 241 char ** 242 hesiod_resolve(context, name, type) 243 void *context; 244 const char *name; 245 const char *type; 246 { 247 struct hesiod_p *ctx = (struct hesiod_p *) context; 248 char *bindname, **retvec; 249 250 bindname = hesiod_to_bind(context, name, type); 251 if (!bindname) 252 return NULL; 253 254 retvec = get_txt_records(ctx->classes[0], bindname); 255 if (retvec == NULL && errno == ENOENT && ctx->classes[1]) 256 retvec = get_txt_records(ctx->classes[1], bindname); 257 258 free(bindname); 259 return retvec; 260 } 261 262 /*ARGSUSED*/ 263 void 264 hesiod_free_list(context, list) 265 void *context; 266 char **list; 267 { 268 char **p; 269 270 if (list == NULL) 271 return; 272 for (p = list; *p; p++) 273 free(*p); 274 free(list); 275 } 276 277 278 /* read_config_file -- 279 * Parse the /etc/hesiod.conf file. Returns 0 on success, 280 * -1 on failure. On failure, it might leave values in ctx->lhs 281 * or ctx->rhs which need to be freed by the caller. 282 */ 283 static int 284 read_config_file(ctx, filename) 285 struct hesiod_p *ctx; 286 const char *filename; 287 { 288 char *key, *data, *p, **which; 289 char buf[MAXDNAME + 7]; 290 int n; 291 FILE *fp; 292 293 /* Set default query classes. */ 294 ctx->classes[0] = C_IN; 295 ctx->classes[1] = C_HS; 296 297 /* Try to open the configuration file. */ 298 fp = fopen(filename, "r"); 299 if (!fp) { 300 /* Use compiled in default domain names. */ 301 ctx->lhs = strdup(DEF_LHS); 302 ctx->rhs = strdup(DEF_RHS); 303 if (ctx->lhs && ctx->rhs) 304 return 0; 305 else { 306 errno = ENOMEM; 307 return -1; 308 } 309 } 310 ctx->lhs = NULL; 311 ctx->rhs = NULL; 312 while (fgets(buf, sizeof(buf), fp) != NULL) { 313 p = buf; 314 if (*p == '#' || *p == '\n' || *p == '\r') 315 continue; 316 while (*p == ' ' || *p == '\t') 317 p++; 318 key = p; 319 while (*p != ' ' && *p != '\t' && *p != '=') 320 p++; 321 *p++ = 0; 322 323 while (isspace(*p) || *p == '=') 324 p++; 325 data = p; 326 while (!isspace(*p)) 327 p++; 328 *p = 0; 329 330 if (strcasecmp(key, "lhs") == 0 || 331 strcasecmp(key, "rhs") == 0) { 332 which = (strcasecmp(key, "lhs") == 0) 333 ? &ctx->lhs : &ctx->rhs; 334 *which = strdup(data); 335 if (!*which) { 336 errno = ENOMEM; 337 return -1; 338 } 339 } else { 340 if (strcasecmp(key, "classes") == 0) { 341 n = 0; 342 while (*data && n < 2) { 343 p = data; 344 while (*p && *p != ',') 345 p++; 346 if (*p) 347 *p++ = 0; 348 if (strcasecmp(data, "IN") == 0) 349 ctx->classes[n++] = C_IN; 350 else 351 if (strcasecmp(data, "HS") == 0) 352 ctx->classes[n++] = 353 C_HS; 354 data = p; 355 } 356 while (n < 2) 357 ctx->classes[n++] = 0; 358 } 359 } 360 } 361 fclose(fp); 362 363 if (!ctx->rhs || ctx->classes[0] == 0 || 364 ctx->classes[0] == ctx->classes[1]) { 365 errno = ENOEXEC; 366 return -1; 367 } 368 return 0; 369 } 370 371 /* 372 * get_txt_records -- 373 * Given a DNS class and a DNS name, do a lookup for TXT records, and 374 * return a list of them. 375 */ 376 static char ** 377 get_txt_records(qclass, name) 378 int qclass; 379 const char *name; 380 { 381 HEADER *hp; 382 unsigned char qbuf[PACKETSZ], abuf[MAX_HESRESP], *p, *eom, *eor; 383 char *dst, **list; 384 int ancount, qdcount, i, j, n, skip, type, class, len; 385 386 /* Make sure the resolver is initialized. */ 387 if ((_res.options & RES_INIT) == 0 && res_init() == -1) 388 return NULL; 389 390 /* Construct the query. */ 391 n = res_mkquery(QUERY, name, qclass, T_TXT, NULL, 0, 392 NULL, qbuf, PACKETSZ); 393 if (n < 0) 394 return NULL; 395 396 /* Send the query. */ 397 n = res_send(qbuf, n, abuf, MAX_HESRESP); 398 if (n < 0) { 399 errno = ECONNREFUSED; 400 return NULL; 401 } 402 /* Parse the header of the result. */ 403 hp = (HEADER *) (void *) abuf; 404 ancount = ntohs(hp->ancount); 405 qdcount = ntohs(hp->qdcount); 406 p = abuf + sizeof(HEADER); 407 eom = abuf + n; 408 409 /* 410 * Skip questions, trying to get to the answer section 411 * which follows. 412 */ 413 for (i = 0; i < qdcount; i++) { 414 skip = dn_skipname(p, eom); 415 if (skip < 0 || p + skip + QFIXEDSZ > eom) { 416 errno = EMSGSIZE; 417 return NULL; 418 } 419 p += skip + QFIXEDSZ; 420 } 421 422 /* Allocate space for the text record answers. */ 423 list = malloc((ancount + 1) * sizeof(char *)); 424 if (!list) { 425 errno = ENOMEM; 426 return NULL; 427 } 428 /* Parse the answers. */ 429 j = 0; 430 for (i = 0; i < ancount; i++) { 431 /* Parse the header of this answer. */ 432 skip = dn_skipname(p, eom); 433 if (skip < 0 || p + skip + 10 > eom) 434 break; 435 type = p[skip + 0] << 8 | p[skip + 1]; 436 class = p[skip + 2] << 8 | p[skip + 3]; 437 len = p[skip + 8] << 8 | p[skip + 9]; 438 p += skip + 10; 439 if (p + len > eom) { 440 errno = EMSGSIZE; 441 break; 442 } 443 /* Skip entries of the wrong class and type. */ 444 if (class != qclass || type != T_TXT) { 445 p += len; 446 continue; 447 } 448 /* Allocate space for this answer. */ 449 list[j] = malloc((size_t)len); 450 if (!list[j]) { 451 errno = ENOMEM; 452 break; 453 } 454 dst = list[j++]; 455 456 /* Copy answer data into the allocated area. */ 457 eor = p + len; 458 while (p < eor) { 459 n = (unsigned char) *p++; 460 if (p + n > eor) { 461 errno = EMSGSIZE; 462 break; 463 } 464 memcpy(dst, p, (size_t)n); 465 p += n; 466 dst += n; 467 } 468 if (p < eor) { 469 errno = EMSGSIZE; 470 break; 471 } 472 *dst = 0; 473 } 474 475 /* 476 * If we didn't terminate the loop normally, something 477 * went wrong. 478 */ 479 if (i < ancount) { 480 for (i = 0; i < j; i++) 481 free(list[i]); 482 free(list); 483 return NULL; 484 } 485 if (j == 0) { 486 errno = ENOENT; 487 free(list); 488 return NULL; 489 } 490 list[j] = NULL; 491 return list; 492 } 493 494 /* 495 * COMPATIBILITY FUNCTIONS 496 */ 497 498 static int inited = 0; 499 static void *context; 500 static int errval = HES_ER_UNINIT; 501 502 int 503 hes_init() 504 { 505 init_context(); 506 return errval; 507 } 508 509 char * 510 hes_to_bind(name, type) 511 const char *name; 512 const char *type; 513 { 514 static char *bindname; 515 if (init_context() < 0) 516 return NULL; 517 if (bindname) 518 free(bindname); 519 bindname = hesiod_to_bind(context, name, type); 520 if (!bindname) 521 translate_errors(); 522 return bindname; 523 } 524 525 char ** 526 hes_resolve(name, type) 527 const char *name; 528 const char *type; 529 { 530 static char **list; 531 532 if (init_context() < 0) 533 return NULL; 534 535 /* 536 * In the old Hesiod interface, the caller was responsible for 537 * freeing the returned strings but not the vector of strings itself. 538 */ 539 if (list) 540 free(list); 541 542 list = hesiod_resolve(context, name, type); 543 if (!list) 544 translate_errors(); 545 return list; 546 } 547 548 int 549 hes_error() 550 { 551 return errval; 552 } 553 554 void 555 hes_free(hp) 556 char **hp; 557 { 558 hesiod_free_list(context, hp); 559 } 560 561 static int 562 init_context() 563 { 564 if (!inited) { 565 inited = 1; 566 if (hesiod_init(&context) < 0) { 567 errval = HES_ER_CONFIG; 568 return -1; 569 } 570 errval = HES_ER_OK; 571 } 572 return 0; 573 } 574 575 static void 576 translate_errors() 577 { 578 switch (errno) { 579 case ENOENT: 580 errval = HES_ER_NOTFOUND; 581 break; 582 case ECONNREFUSED: 583 case EMSGSIZE: 584 errval = HES_ER_NET; 585 break; 586 case ENOMEM: 587 default: 588 /* Not a good match, but the best we can do. */ 589 errval = HES_ER_CONFIG; 590 break; 591 } 592 } 593