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hesiod.c revision 1.26 
      1 /*	$NetBSD: hesiod.c,v 1.26 2011/10/15 22:57:57 christos 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 1.26 2011/10/15 22:57:57 christos 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	*buf, *key, *data, *p, **which;
    321 	int	 n;
    322 	FILE	*fp;
    323 
    324 	_DIAGASSERT(ctx != NULL);
    325 	_DIAGASSERT(filename != NULL);
    326 
    327 	/* Set default query classes. */
    328 	ctx->classes[0] = C_IN;
    329 	ctx->classes[1] = C_HS;
    330 
    331 	/* Try to open the configuration file. */
    332 	fp = fopen(filename, "r");
    333 	if (!fp) {
    334 		/* Use compiled in default domain names. */
    335 		ctx->lhs = strdup(DEF_LHS);
    336 		ctx->rhs = strdup(DEF_RHS);
    337 		if (ctx->lhs && ctx->rhs)
    338 			return 0;
    339 		else {
    340 			errno = ENOMEM;
    341 			return -1;
    342 		}
    343 	}
    344 	ctx->lhs = NULL;
    345 	ctx->rhs = NULL;
    346 	for (; (buf = fparseln(fp, NULL, NULL, NULL, FPARSELN_UNESCALL))
    347 	    != NULL; free(buf)) {
    348 		p = buf;
    349 		while (*p == ' ' || *p == '\t')
    350 			p++;
    351 		key = p;
    352 		while (*p != ' ' && *p != '\t' && *p != '=' && *p)
    353 			p++;
    354 
    355 		if (*p == '\0')
    356 			continue;
    357 
    358 		*p++ = 0;
    359 
    360 		while (isspace((u_char) *p) || *p == '=')
    361 			p++;
    362 
    363 		if (*p == '\0')
    364 			continue;
    365 
    366 		data = p;
    367 		while (!isspace((u_char) *p) && *p)
    368 			p++;
    369 
    370 		*p = 0;
    371 
    372 		if (strcasecmp(key, "lhs") == 0 ||
    373 		    strcasecmp(key, "rhs") == 0) {
    374 			which = (strcasecmp(key, "lhs") == 0)
    375 			    ? &ctx->lhs : &ctx->rhs;
    376 			*which = strdup(data);
    377 			if (!*which) {
    378 				errno = ENOMEM;
    379 				free(buf);
    380 				(void)fclose(fp);
    381 				return -1;
    382 			}
    383 		} else {
    384 			if (strcasecmp(key, "classes") == 0) {
    385 				n = 0;
    386 				while (*data && n < 2) {
    387 					p = data;
    388 					while (*p && *p != ',')
    389 						p++;
    390 					if (*p)
    391 						*p++ = 0;
    392 					if (strcasecmp(data, "IN") == 0)
    393 						ctx->classes[n++] = C_IN;
    394 					else
    395 						if (strcasecmp(data, "HS") == 0)
    396 							ctx->classes[n++] =
    397 							    C_HS;
    398 					data = p;
    399 				}
    400 				while (n < 2)
    401 					ctx->classes[n++] = 0;
    402 			}
    403 		}
    404 	}
    405 	fclose(fp);
    406 
    407 	if (!ctx->rhs || ctx->classes[0] == 0 ||
    408 	    ctx->classes[0] == ctx->classes[1]) {
    409 		errno = ENOEXEC;
    410 		return -1;
    411 	}
    412 	return 0;
    413 }
    414 
    415 /*
    416  * get_txt_records --
    417  *	Given a DNS class and a DNS name, do a lookup for TXT records, and
    418  *	return a list of them.
    419  */
    420 static char **
    421 get_txt_records(qclass, name)
    422 	int		 qclass;
    423 	const char	*name;
    424 {
    425 	HEADER		*hp;
    426 	unsigned char	 qbuf[PACKETSZ], abuf[MAX_HESRESP], *p, *eom, *eor;
    427 	char		*dst, **list;
    428 	int		 ancount, qdcount, i, j, n, skip, type, class, len;
    429 	res_state	 res = __res_get_state();
    430 
    431 	if (res == NULL)
    432 		return NULL;
    433 
    434 	_DIAGASSERT(name != NULL);
    435 
    436 	/* Construct the query. */
    437 	n = res_nmkquery(res, QUERY, name, qclass, T_TXT, NULL, 0,
    438 	    NULL, qbuf, PACKETSZ);
    439 	if (n < 0) {
    440 		errno = EMSGSIZE;
    441 		__res_put_state(res);
    442 		return NULL;
    443 	}
    444 
    445 	/* Send the query. */
    446 	n = res_nsend(res, qbuf, n, abuf, MAX_HESRESP);
    447 	__res_put_state(res);
    448 	if (n < 0) {
    449 		errno = ECONNREFUSED;
    450 		return NULL;
    451 	}
    452 	/* Parse the header of the result. */
    453 	hp = (HEADER *) (void *) abuf;
    454 	ancount = ntohs(hp->ancount);
    455 	qdcount = ntohs(hp->qdcount);
    456 	p = abuf + sizeof(HEADER);
    457 	eom = abuf + n;
    458 
    459 	/*
    460 	 * Skip questions, trying to get to the answer section
    461 	 * which follows.
    462 	 */
    463 	for (i = 0; i < qdcount; i++) {
    464 		skip = dn_skipname(p, eom);
    465 		if (skip < 0 || p + skip + QFIXEDSZ > eom) {
    466 			errno = EMSGSIZE;
    467 			return NULL;
    468 		}
    469 		p += skip + QFIXEDSZ;
    470 	}
    471 
    472 	/* Allocate space for the text record answers. */
    473 	list = malloc((ancount + 1) * sizeof(char *));
    474 	if (!list) {
    475 		errno = ENOMEM;
    476 		return NULL;
    477 	}
    478 	/* Parse the answers. */
    479 	j = 0;
    480 	for (i = 0; i < ancount; i++) {
    481 		/* Parse the header of this answer. */
    482 		skip = dn_skipname(p, eom);
    483 		if (skip < 0 || p + skip + 10 > eom)
    484 			break;
    485 		type = p[skip + 0] << 8 | p[skip + 1];
    486 		class = p[skip + 2] << 8 | p[skip + 3];
    487 		len = p[skip + 8] << 8 | p[skip + 9];
    488 		p += skip + 10;
    489 		if (p + len > eom) {
    490 			errno = EMSGSIZE;
    491 			break;
    492 		}
    493 		/* Skip entries of the wrong class and type. */
    494 		if (class != qclass || type != T_TXT) {
    495 			p += len;
    496 			continue;
    497 		}
    498 		/* Allocate space for this answer. */
    499 		list[j] = malloc((size_t)len);
    500 		if (!list[j]) {
    501 			errno = ENOMEM;
    502 			break;
    503 		}
    504 		dst = list[j++];
    505 
    506 		/* Copy answer data into the allocated area. */
    507 		eor = p + len;
    508 		while (p < eor) {
    509 			n = (unsigned char) *p++;
    510 			if (p + n > eor) {
    511 				errno = EMSGSIZE;
    512 				break;
    513 			}
    514 			memcpy(dst, p, (size_t)n);
    515 			p += n;
    516 			dst += n;
    517 		}
    518 		if (p < eor) {
    519 			errno = EMSGSIZE;
    520 			break;
    521 		}
    522 		*dst = 0;
    523 	}
    524 
    525 	/*
    526 	 * If we didn't terminate the loop normally, something
    527 	 * went wrong.
    528 	 */
    529 	if (i < ancount) {
    530 		for (i = 0; i < j; i++)
    531 			free(list[i]);
    532 		free(list);
    533 		return NULL;
    534 	}
    535 	if (j == 0) {
    536 		errno = ENOENT;
    537 		free(list);
    538 		return NULL;
    539 	}
    540 	list[j] = NULL;
    541 	return list;
    542 }
    543 
    544 /*
    545  * COMPATIBILITY FUNCTIONS
    546  */
    547 
    548 static int	  inited = 0;
    549 static void	 *context;
    550 static int	  errval = HES_ER_UNINIT;
    551 
    552 int
    553 hes_init()
    554 {
    555 	init_context();
    556 	return errval;
    557 }
    558 
    559 char *
    560 hes_to_bind(name, type)
    561 	const char	*name;
    562 	const char	*type;
    563 {
    564 	static	char	*bindname;
    565 
    566 	_DIAGASSERT(name != NULL);
    567 	_DIAGASSERT(type != NULL);
    568 
    569 	if (init_context() < 0)
    570 		return NULL;
    571 	if (bindname)
    572 		free(bindname);
    573 	bindname = hesiod_to_bind(context, name, type);
    574 	if (!bindname)
    575 		translate_errors();
    576 	return bindname;
    577 }
    578 
    579 char **
    580 hes_resolve(name, type)
    581 	const char	*name;
    582 	const char	*type;
    583 {
    584 	static char	**list;
    585 
    586 	_DIAGASSERT(name != NULL);
    587 	_DIAGASSERT(type != NULL);
    588 
    589 	if (init_context() < 0)
    590 		return NULL;
    591 
    592 	/*
    593 	 * In the old Hesiod interface, the caller was responsible for
    594 	 * freeing the returned strings but not the vector of strings itself.
    595 	 */
    596 	if (list)
    597 		free(list);
    598 
    599 	list = hesiod_resolve(context, name, type);
    600 	if (!list)
    601 		translate_errors();
    602 	return list;
    603 }
    604 
    605 int
    606 hes_error()
    607 {
    608 	return errval;
    609 }
    610 
    611 void
    612 hes_free(hp)
    613 	char **hp;
    614 {
    615 	hesiod_free_list(context, hp);
    616 }
    617 
    618 static int
    619 init_context()
    620 {
    621 	if (!inited) {
    622 		inited = 1;
    623 		if (hesiod_init(&context) < 0) {
    624 			errval = HES_ER_CONFIG;
    625 			return -1;
    626 		}
    627 		errval = HES_ER_OK;
    628 	}
    629 	return 0;
    630 }
    631 
    632 static void
    633 translate_errors()
    634 {
    635 	switch (errno) {
    636 	case ENOENT:
    637 		errval = HES_ER_NOTFOUND;
    638 		break;
    639 	case ECONNREFUSED:
    640 	case EMSGSIZE:
    641 		errval = HES_ER_NET;
    642 		break;
    643 	default:
    644 		/* Not a good match, but the best we can do. */
    645 		errval = HES_ER_CONFIG;
    646 		break;
    647 	}
    648 }
    649