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 0 49 static char *orig_rcsid = "$NetBSD: hesiod.c,v 1.9 1999/02/11 06:16:38 simonb Exp $"; 50 #endif 51 #include <sys/cdefs.h> 52 __FBSDID("$FreeBSD$"); 53 54 #include <sys/param.h> 55 #include <netinet/in.h> 56 #include <arpa/nameser.h> 57 58 #include <ctype.h> 59 #include <errno.h> 60 #include <hesiod.h> 61 #include <resolv.h> 62 #include <stdio.h> 63 #include <stdlib.h> 64 #include <string.h> 65 #include <unistd.h> 66 67 struct hesiod_p { 68 char *lhs; /* normally ".ns" */ 69 char *rhs; /* AKA the default hesiod domain */ 70 int classes[2]; /* The class search order. */ 71 }; 72 73 #define MAX_HESRESP 1024 74 75 static int read_config_file(struct hesiod_p *, const char *); 76 static char **get_txt_records(int, const char *); 77 static int init_context(void); 78 static void translate_errors(void); 79 80 81 /* 82 * hesiod_init -- 83 * initialize a hesiod_p. 84 */ 85 int 86 hesiod_init(context) 87 void **context; 88 { 89 struct hesiod_p *ctx; 90 const char *p, *configname; 91 92 ctx = malloc(sizeof(struct hesiod_p)); 93 if (ctx) { 94 *context = ctx; 95 if (!issetugid()) 96 configname = getenv("HESIOD_CONFIG"); 97 else 98 configname = NULL; 99 if (!configname) 100 configname = _PATH_HESIOD_CONF; 101 if (read_config_file(ctx, configname) >= 0) { 102 /* 103 * The default rhs can be overridden by an 104 * environment variable. 105 */ 106 if (!issetugid()) 107 p = getenv("HES_DOMAIN"); 108 else 109 p = NULL; 110 if (p) { 111 if (ctx->rhs) 112 free(ctx->rhs); 113 ctx->rhs = malloc(strlen(p) + 2); 114 if (ctx->rhs) { 115 *ctx->rhs = '.'; 116 strcpy(ctx->rhs + 1, 117 (*p == '.') ? p + 1 : p); 118 return 0; 119 } else 120 errno = ENOMEM; 121 } else 122 return 0; 123 } 124 } else 125 errno = ENOMEM; 126 127 if (ctx->lhs) 128 free(ctx->lhs); 129 if (ctx->rhs) 130 free(ctx->rhs); 131 if (ctx) 132 free(ctx); 133 return -1; 134 } 135 136 /* 137 * hesiod_end -- 138 * Deallocates the hesiod_p. 139 */ 140 void 141 hesiod_end(context) 142 void *context; 143 { 144 struct hesiod_p *ctx = (struct hesiod_p *) context; 145 146 free(ctx->rhs); 147 if (ctx->lhs) 148 free(ctx->lhs); 149 free(ctx); 150 } 151 152 /* 153 * hesiod_to_bind -- 154 * takes a hesiod (name, type) and returns a DNS 155 * name which is to be resolved. 156 */ 157 char * 158 hesiod_to_bind(void *context, const char *name, const char *type) 159 { 160 struct hesiod_p *ctx = (struct hesiod_p *) context; 161 char bindname[MAXDNAME], *p, *ret, **rhs_list = NULL; 162 const char *rhs; 163 int len; 164 165 if (strlcpy(bindname, name, sizeof(bindname)) >= sizeof(bindname)) { 166 errno = EMSGSIZE; 167 return NULL; 168 } 169 170 /* 171 * Find the right right hand side to use, possibly 172 * truncating bindname. 173 */ 174 p = strchr(bindname, '@'); 175 if (p) { 176 *p++ = 0; 177 if (strchr(p, '.')) 178 rhs = name + (p - bindname); 179 else { 180 rhs_list = hesiod_resolve(context, p, "rhs-extension"); 181 if (rhs_list) 182 rhs = *rhs_list; 183 else { 184 errno = ENOENT; 185 return NULL; 186 } 187 } 188 } else 189 rhs = ctx->rhs; 190 191 /* See if we have enough room. */ 192 len = strlen(bindname) + 1 + strlen(type); 193 if (ctx->lhs) 194 len += strlen(ctx->lhs) + ((ctx->lhs[0] != '.') ? 1 : 0); 195 len += strlen(rhs) + ((rhs[0] != '.') ? 1 : 0); 196 if (len > sizeof(bindname) - 1) { 197 if (rhs_list) 198 hesiod_free_list(context, rhs_list); 199 errno = EMSGSIZE; 200 return NULL; 201 } 202 /* Put together the rest of the domain. */ 203 strcat(bindname, "."); 204 strcat(bindname, type); 205 /* Only append lhs if it isn't empty. */ 206 if (ctx->lhs && ctx->lhs[0] != '\0' ) { 207 if (ctx->lhs[0] != '.') 208 strcat(bindname, "."); 209 strcat(bindname, ctx->lhs); 210 } 211 if (rhs[0] != '.') 212 strcat(bindname, "."); 213 strcat(bindname, rhs); 214 215 /* rhs_list is no longer needed, since we're done with rhs. */ 216 if (rhs_list) 217 hesiod_free_list(context, rhs_list); 218 219 /* Make a copy of the result and return it to the caller. */ 220 ret = strdup(bindname); 221 if (!ret) 222 errno = ENOMEM; 223 return ret; 224 } 225 226 /* 227 * hesiod_resolve -- 228 * Given a hesiod name and type, return an array of strings returned 229 * by the resolver. 230 */ 231 char ** 232 hesiod_resolve(context, name, type) 233 void *context; 234 const char *name; 235 const char *type; 236 { 237 struct hesiod_p *ctx = (struct hesiod_p *) context; 238 char *bindname, **retvec; 239 240 bindname = hesiod_to_bind(context, name, type); 241 if (!bindname) 242 return NULL; 243 244 retvec = get_txt_records(ctx->classes[0], bindname); 245 if (retvec == NULL && errno == ENOENT && ctx->classes[1]) 246 retvec = get_txt_records(ctx->classes[1], bindname); 247 248 free(bindname); 249 return retvec; 250 } 251 252 /*ARGSUSED*/ 253 void 254 hesiod_free_list(context, list) 255 void *context; 256 char **list; 257 { 258 char **p; 259 260 if (list == NULL) 261 return; 262 for (p = list; *p; p++) 263 free(*p); 264 free(list); 265 } 266 267 268 /* read_config_file -- 269 * Parse the /etc/hesiod.conf file. Returns 0 on success, 270 * -1 on failure. On failure, it might leave values in ctx->lhs 271 * or ctx->rhs which need to be freed by the caller. 272 */ 273 static int 274 read_config_file(ctx, filename) 275 struct hesiod_p *ctx; 276 const char *filename; 277 { 278 char *key, *data, *p, **which; 279 char buf[MAXDNAME + 7]; 280 int n; 281 FILE *fp; 282 283 /* Set default query classes. */ 284 ctx->classes[0] = C_IN; 285 ctx->classes[1] = C_HS; 286 287 /* Try to open the configuration file. */ 288 fp = fopen(filename, "re"); 289 if (!fp) { 290 /* Use compiled in default domain names. */ 291 ctx->lhs = strdup(DEF_LHS); 292 ctx->rhs = strdup(DEF_RHS); 293 if (ctx->lhs && ctx->rhs) 294 return 0; 295 else { 296 errno = ENOMEM; 297 return -1; 298 } 299 } 300 ctx->lhs = NULL; 301 ctx->rhs = NULL; 302 while (fgets(buf, sizeof(buf), fp) != NULL) { 303 p = buf; 304 if (*p == '#' || *p == '\n' || *p == '\r') 305 continue; 306 while (*p == ' ' || *p == '\t') 307 p++; 308 key = p; 309 while (*p != ' ' && *p != '\t' && *p != '=') 310 p++; 311 *p++ = 0; 312 313 while (isspace(*p) || *p == '=') 314 p++; 315 data = p; 316 while (!isspace(*p)) 317 p++; 318 *p = 0; 319 320 if (strcasecmp(key, "lhs") == 0 || 321 strcasecmp(key, "rhs") == 0) { 322 which = (strcasecmp(key, "lhs") == 0) 323 ? &ctx->lhs : &ctx->rhs; 324 *which = strdup(data); 325 if (!*which) { 326 fclose(fp); 327 errno = ENOMEM; 328 return -1; 329 } 330 } else { 331 if (strcasecmp(key, "classes") == 0) { 332 n = 0; 333 while (*data && n < 2) { 334 p = data; 335 while (*p && *p != ',') 336 p++; 337 if (*p) 338 *p++ = 0; 339 if (strcasecmp(data, "IN") == 0) 340 ctx->classes[n++] = C_IN; 341 else 342 if (strcasecmp(data, "HS") == 0) 343 ctx->classes[n++] = 344 C_HS; 345 data = p; 346 } 347 while (n < 2) 348 ctx->classes[n++] = 0; 349 } 350 } 351 } 352 fclose(fp); 353 354 if (!ctx->rhs || ctx->classes[0] == 0 || 355 ctx->classes[0] == ctx->classes[1]) { 356 errno = ENOEXEC; 357 return -1; 358 } 359 return 0; 360 } 361 362 /* 363 * get_txt_records -- 364 * Given a DNS class and a DNS name, do a lookup for TXT records, and 365 * return a list of them. 366 */ 367 static char ** 368 get_txt_records(qclass, name) 369 int qclass; 370 const char *name; 371 { 372 HEADER *hp; 373 unsigned char qbuf[PACKETSZ], abuf[MAX_HESRESP], *p, *eom, *eor; 374 char *dst, **list; 375 int ancount, qdcount, i, j, n, skip, type, class, len; 376 377 /* Make sure the resolver is initialized. */ 378 if ((_res.options & RES_INIT) == 0 && res_init() == -1) 379 return NULL; 380 381 /* Construct the query. */ 382 n = res_mkquery(QUERY, name, qclass, T_TXT, NULL, 0, 383 NULL, qbuf, PACKETSZ); 384 if (n < 0) 385 return NULL; 386 387 /* Send the query. */ 388 n = res_send(qbuf, n, abuf, MAX_HESRESP); 389 if (n < 0 || n > MAX_HESRESP) { 390 errno = ECONNREFUSED; /* XXX */ 391 return NULL; 392 } 393 /* Parse the header of the result. */ 394 hp = (HEADER *) (void *) abuf; 395 ancount = ntohs(hp->ancount); 396 qdcount = ntohs(hp->qdcount); 397 p = abuf + sizeof(HEADER); 398 eom = abuf + n; 399 400 /* 401 * Skip questions, trying to get to the answer section 402 * which follows. 403 */ 404 for (i = 0; i < qdcount; i++) { 405 skip = dn_skipname(p, eom); 406 if (skip < 0 || p + skip + QFIXEDSZ > eom) { 407 errno = EMSGSIZE; 408 return NULL; 409 } 410 p += skip + QFIXEDSZ; 411 } 412 413 /* Allocate space for the text record answers. */ 414 list = malloc((ancount + 1) * sizeof(char *)); 415 if (!list) { 416 errno = ENOMEM; 417 return NULL; 418 } 419 /* Parse the answers. */ 420 j = 0; 421 for (i = 0; i < ancount; i++) { 422 /* Parse the header of this answer. */ 423 skip = dn_skipname(p, eom); 424 if (skip < 0 || p + skip + 10 > eom) 425 break; 426 type = p[skip + 0] << 8 | p[skip + 1]; 427 class = p[skip + 2] << 8 | p[skip + 3]; 428 len = p[skip + 8] << 8 | p[skip + 9]; 429 p += skip + 10; 430 if (p + len > eom) { 431 errno = EMSGSIZE; 432 break; 433 } 434 /* Skip entries of the wrong class and type. */ 435 if (class != qclass || type != T_TXT) { 436 p += len; 437 continue; 438 } 439 /* Allocate space for this answer. */ 440 list[j] = malloc((size_t)len); 441 if (!list[j]) { 442 errno = ENOMEM; 443 break; 444 } 445 dst = list[j++]; 446 447 /* Copy answer data into the allocated area. */ 448 eor = p + len; 449 while (p < eor) { 450 n = (unsigned char) *p++; 451 if (p + n > eor) { 452 errno = EMSGSIZE; 453 break; 454 } 455 memcpy(dst, p, (size_t)n); 456 p += n; 457 dst += n; 458 } 459 if (p < eor) { 460 errno = EMSGSIZE; 461 break; 462 } 463 *dst = 0; 464 } 465 466 /* 467 * If we didn't terminate the loop normally, something 468 * went wrong. 469 */ 470 if (i < ancount) { 471 for (i = 0; i < j; i++) 472 free(list[i]); 473 free(list); 474 return NULL; 475 } 476 if (j == 0) { 477 errno = ENOENT; 478 free(list); 479 return NULL; 480 } 481 list[j] = NULL; 482 return list; 483 } 484 485 /* 486 * COMPATIBILITY FUNCTIONS 487 */ 488 489 static int inited = 0; 490 static void *context; 491 static int errval = HES_ER_UNINIT; 492 493 int 494 hes_init() 495 { 496 init_context(); 497 return errval; 498 } 499 500 char * 501 hes_to_bind(name, type) 502 const char *name; 503 const char *type; 504 { 505 static char *bindname; 506 if (init_context() < 0) 507 return NULL; 508 if (bindname) 509 free(bindname); 510 bindname = hesiod_to_bind(context, name, type); 511 if (!bindname) 512 translate_errors(); 513 return bindname; 514 } 515 516 char ** 517 hes_resolve(name, type) 518 const char *name; 519 const char *type; 520 { 521 static char **list; 522 523 if (init_context() < 0) 524 return NULL; 525 526 /* 527 * In the old Hesiod interface, the caller was responsible for 528 * freeing the returned strings but not the vector of strings itself. 529 */ 530 if (list) 531 free(list); 532 533 list = hesiod_resolve(context, name, type); 534 if (!list) 535 translate_errors(); 536 return list; 537 } 538 539 int 540 hes_error() 541 { 542 return errval; 543 } 544 545 void 546 hes_free(hp) 547 char **hp; 548 { 549 hesiod_free_list(context, hp); 550 } 551 552 static int 553 init_context() 554 { 555 if (!inited) { 556 inited = 1; 557 if (hesiod_init(&context) < 0) { 558 errval = HES_ER_CONFIG; 559 return -1; 560 } 561 errval = HES_ER_OK; 562 } 563 return 0; 564 } 565 566 static void 567 translate_errors() 568 { 569 switch (errno) { 570 case ENOENT: 571 errval = HES_ER_NOTFOUND; 572 break; 573 case ECONNREFUSED: 574 case EMSGSIZE: 575 errval = HES_ER_NET; 576 break; 577 case ENOMEM: 578 default: 579 /* Not a good match, but the best we can do. */ 580 errval = HES_ER_CONFIG; 581 break; 582 } 583 } 584