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