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hesiod.c revision 1.10 
      1 /*	$NetBSD: hesiod.c,v 1.10 1999/09/16 11:45:13 lukem 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 1.10 1999/09/16 11:45:13 lukem 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 
     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 #ifdef _DIAGNOSTIC
    115 	if (context == NULL) {
    116 		errno = EFAULT;
    117 		return (-1);
    118 	}
    119 #endif
    120 
    121 	ctx = malloc(sizeof(struct hesiod_p));
    122 	if (ctx) {
    123 		*context = ctx;
    124 		configname = getenv("HESIOD_CONFIG");
    125 		if (!configname)
    126 			configname = _PATH_HESIOD_CONF;
    127 		if (read_config_file(ctx, configname) >= 0) {
    128 			/*
    129 			 * The default rhs can be overridden by an
    130 			 * environment variable.
    131 			 */
    132 			p = getenv("HES_DOMAIN");
    133 			if (p) {
    134 				if (ctx->rhs)
    135 					free(ctx->rhs);
    136 				ctx->rhs = malloc(strlen(p) + 2);
    137 				if (ctx->rhs) {
    138 					*ctx->rhs = '.';
    139 					strcpy(ctx->rhs + 1,
    140 					    (*p == '.') ? p + 1 : p);
    141 					return 0;
    142 				} else
    143 					errno = ENOMEM;
    144 			} else
    145 				return 0;
    146 		}
    147 	} else
    148 		errno = ENOMEM;
    149 
    150 	serrno = errno;
    151 	if (ctx->lhs)
    152 		free(ctx->lhs);
    153 	if (ctx->rhs)
    154 		free(ctx->rhs);
    155 	if (ctx)
    156 		free(ctx);
    157 	errno = serrno;
    158 	return -1;
    159 }
    160 
    161 /*
    162  * hesiod_end --
    163  *	Deallocates the hesiod_p.
    164  */
    165 void
    166 hesiod_end(context)
    167 	void	*context;
    168 {
    169 	struct hesiod_p *ctx = (struct hesiod_p *) context;
    170 
    171 	_DIAGASSERT(context != NULL);
    172 #ifdef _DIAGNOSTIC
    173 	if (context == NULL)
    174 		return;
    175 #endif
    176 
    177 	free(ctx->rhs);
    178 	if (ctx->lhs)
    179 		free(ctx->lhs);
    180 	free(ctx);
    181 }
    182 
    183 /*
    184  * hesiod_to_bind --
    185  * 	takes a hesiod (name, type) and returns a DNS
    186  *	name which is to be resolved.
    187  */
    188 char *
    189 hesiod_to_bind(void *context, const char *name, const char *type)
    190 {
    191 	struct hesiod_p *ctx = (struct hesiod_p *) context;
    192 	char		 bindname[MAXDNAME], *p, *ret, **rhs_list = NULL;
    193 	const char	*rhs;
    194 	int		 len;
    195 
    196 	_DIAGASSERT(context != NULL);
    197 	_DIAGASSERT(name != NULL);
    198 	_DIAGASSERT(type != NULL);
    199 #ifdef _DIAGNOSTIC
    200 	if (context == NULL || name == NULL || type == NULL)
    201 		return (NULL);
    202 #endif
    203 
    204 	strcpy(bindname, name);
    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 #ifdef _DIAGNOSTIC
    280 	if (context == NULL || name == NULL || type == NULL)
    281 		return (NULL);
    282 #endif
    283 
    284 	bindname = hesiod_to_bind(context, name, type);
    285 	if (!bindname)
    286 		return NULL;
    287 
    288 	retvec = get_txt_records(ctx->classes[0], bindname);
    289 	if (retvec == NULL && errno == ENOENT && ctx->classes[1])
    290 		retvec = get_txt_records(ctx->classes[1], bindname);
    291 
    292 	free(bindname);
    293 	return retvec;
    294 }
    295 
    296 /*ARGSUSED*/
    297 void
    298 hesiod_free_list(context, list)
    299 	void	 *context;
    300 	char	**list;
    301 {
    302 	char  **p;
    303 
    304 	_DIAGASSERT(context != NULL);
    305 #ifdef _DIAGNOSTIC
    306 	if (context == NULL)
    307 		return;
    308 #endif
    309 
    310 	if (list == NULL)
    311 		return;
    312 	for (p = list; *p; p++)
    313 		free(*p);
    314 	free(list);
    315 }
    316 
    317 
    318 /* read_config_file --
    319  *	Parse the /etc/hesiod.conf file.  Returns 0 on success,
    320  *	-1 on failure.  On failure, it might leave values in ctx->lhs
    321  *	or ctx->rhs which need to be freed by the caller.
    322  */
    323 static int
    324 read_config_file(ctx, filename)
    325 	struct hesiod_p	*ctx;
    326 	const char	*filename;
    327 {
    328 	char	*key, *data, *p, **which;
    329 	char	 buf[MAXDNAME + 7];
    330 	int	 n;
    331 	FILE	*fp;
    332 
    333 	_DIAGASSERT(ctx != NULL);
    334 	_DIAGASSERT(filename != NULL);
    335 
    336 		/* Set default query classes. */
    337 	ctx->classes[0] = C_IN;
    338 	ctx->classes[1] = C_HS;
    339 
    340 		/* Try to open the configuration file. */
    341 	fp = fopen(filename, "r");
    342 	if (!fp) {
    343 		/* Use compiled in default domain names. */
    344 		ctx->lhs = strdup(DEF_LHS);
    345 		ctx->rhs = strdup(DEF_RHS);
    346 		if (ctx->lhs && ctx->rhs)
    347 			return 0;
    348 		else {
    349 			errno = ENOMEM;
    350 			return -1;
    351 		}
    352 	}
    353 	ctx->lhs = NULL;
    354 	ctx->rhs = NULL;
    355 	while (fgets(buf, sizeof(buf), fp) != NULL) {
    356 		p = buf;
    357 		if (*p == '#' || *p == '\n' || *p == '\r')
    358 			continue;
    359 		while (*p == ' ' || *p == '\t')
    360 			p++;
    361 		key = p;
    362 		while (*p != ' ' && *p != '\t' && *p != '=')
    363 			p++;
    364 		*p++ = 0;
    365 
    366 		while (isspace(*p) || *p == '=')
    367 			p++;
    368 		data = p;
    369 		while (!isspace(*p))
    370 			p++;
    371 		*p = 0;
    372 
    373 		if (strcasecmp(key, "lhs") == 0 ||
    374 		    strcasecmp(key, "rhs") == 0) {
    375 			which = (strcasecmp(key, "lhs") == 0)
    376 			    ? &ctx->lhs : &ctx->rhs;
    377 			*which = strdup(data);
    378 			if (!*which) {
    379 				errno = ENOMEM;
    380 				return -1;
    381 			}
    382 		} else {
    383 			if (strcasecmp(key, "classes") == 0) {
    384 				n = 0;
    385 				while (*data && n < 2) {
    386 					p = data;
    387 					while (*p && *p != ',')
    388 						p++;
    389 					if (*p)
    390 						*p++ = 0;
    391 					if (strcasecmp(data, "IN") == 0)
    392 						ctx->classes[n++] = C_IN;
    393 					else
    394 						if (strcasecmp(data, "HS") == 0)
    395 							ctx->classes[n++] =
    396 							    C_HS;
    397 					data = p;
    398 				}
    399 				while (n < 2)
    400 					ctx->classes[n++] = 0;
    401 			}
    402 		}
    403 	}
    404 	fclose(fp);
    405 
    406 	if (!ctx->rhs || ctx->classes[0] == 0 ||
    407 	    ctx->classes[0] == ctx->classes[1]) {
    408 		errno = ENOEXEC;
    409 		return -1;
    410 	}
    411 	return 0;
    412 }
    413 
    414 /*
    415  * get_txt_records --
    416  *	Given a DNS class and a DNS name, do a lookup for TXT records, and
    417  *	return a list of them.
    418  */
    419 static char **
    420 get_txt_records(qclass, name)
    421 	int		 qclass;
    422 	const char	*name;
    423 {
    424 	HEADER		*hp;
    425 	unsigned char	 qbuf[PACKETSZ], abuf[MAX_HESRESP], *p, *eom, *eor;
    426 	char		*dst, **list;
    427 	int		 ancount, qdcount, i, j, n, skip, type, class, len;
    428 
    429 	_DIAGASSERT(name != NULL);
    430 
    431 		/* Make sure the resolver is initialized. */
    432 	if ((_res.options & RES_INIT) == 0 && res_init() == -1)
    433 		return NULL;
    434 
    435 		/* Construct the query. */
    436 	n = res_mkquery(QUERY, name, qclass, T_TXT, NULL, 0,
    437 	    NULL, qbuf, PACKETSZ);
    438 	if (n < 0)
    439 		return NULL;
    440 
    441 		/* Send the query. */
    442 	n = res_send(qbuf, n, abuf, MAX_HESRESP);
    443 	if (n < 0) {
    444 		errno = ECONNREFUSED;
    445 		return NULL;
    446 	}
    447 		/* Parse the header of the result. */
    448 	hp = (HEADER *) (void *) abuf;
    449 	ancount = ntohs(hp->ancount);
    450 	qdcount = ntohs(hp->qdcount);
    451 	p = abuf + sizeof(HEADER);
    452 	eom = abuf + n;
    453 
    454 		/*
    455 		 * Skip questions, trying to get to the answer section
    456 		 * which follows.
    457 		 */
    458 	for (i = 0; i < qdcount; i++) {
    459 		skip = dn_skipname(p, eom);
    460 		if (skip < 0 || p + skip + QFIXEDSZ > eom) {
    461 			errno = EMSGSIZE;
    462 			return NULL;
    463 		}
    464 		p += skip + QFIXEDSZ;
    465 	}
    466 
    467 		/* Allocate space for the text record answers. */
    468 	list = malloc((ancount + 1) * sizeof(char *));
    469 	if (!list) {
    470 		errno = ENOMEM;
    471 		return NULL;
    472 	}
    473 		/* Parse the answers. */
    474 	j = 0;
    475 	for (i = 0; i < ancount; i++) {
    476 		/* Parse the header of this answer. */
    477 		skip = dn_skipname(p, eom);
    478 		if (skip < 0 || p + skip + 10 > eom)
    479 			break;
    480 		type = p[skip + 0] << 8 | p[skip + 1];
    481 		class = p[skip + 2] << 8 | p[skip + 3];
    482 		len = p[skip + 8] << 8 | p[skip + 9];
    483 		p += skip + 10;
    484 		if (p + len > eom) {
    485 			errno = EMSGSIZE;
    486 			break;
    487 		}
    488 		/* Skip entries of the wrong class and type. */
    489 		if (class != qclass || type != T_TXT) {
    490 			p += len;
    491 			continue;
    492 		}
    493 		/* Allocate space for this answer. */
    494 		list[j] = malloc((size_t)len);
    495 		if (!list[j]) {
    496 			errno = ENOMEM;
    497 			break;
    498 		}
    499 		dst = list[j++];
    500 
    501 		/* Copy answer data into the allocated area. */
    502 		eor = p + len;
    503 		while (p < eor) {
    504 			n = (unsigned char) *p++;
    505 			if (p + n > eor) {
    506 				errno = EMSGSIZE;
    507 				break;
    508 			}
    509 			memcpy(dst, p, (size_t)n);
    510 			p += n;
    511 			dst += n;
    512 		}
    513 		if (p < eor) {
    514 			errno = EMSGSIZE;
    515 			break;
    516 		}
    517 		*dst = 0;
    518 	}
    519 
    520 		/*
    521 		 * If we didn't terminate the loop normally, something
    522 		 * went wrong.
    523 		 */
    524 	if (i < ancount) {
    525 		for (i = 0; i < j; i++)
    526 			free(list[i]);
    527 		free(list);
    528 		return NULL;
    529 	}
    530 	if (j == 0) {
    531 		errno = ENOENT;
    532 		free(list);
    533 		return NULL;
    534 	}
    535 	list[j] = NULL;
    536 	return list;
    537 }
    538 
    539 		/*
    540 		 *	COMPATIBILITY FUNCTIONS
    541 		 */
    542 
    543 static int	  inited = 0;
    544 static void	 *context;
    545 static int	  errval = HES_ER_UNINIT;
    546 
    547 int
    548 hes_init()
    549 {
    550 	init_context();
    551 	return errval;
    552 }
    553 
    554 char *
    555 hes_to_bind(name, type)
    556 	const char	*name;
    557 	const char	*type;
    558 {
    559 	static	char	*bindname;
    560 
    561 	_DIAGASSERT(name != NULL);
    562 	_DIAGASSERT(type != NULL);
    563 #ifdef _DIAGNOSTIC
    564 	if (name == NULL || type == NULL)
    565 		return (NULL);
    566 #endif
    567 
    568 	if (init_context() < 0)
    569 		return NULL;
    570 	if (bindname)
    571 		free(bindname);
    572 	bindname = hesiod_to_bind(context, name, type);
    573 	if (!bindname)
    574 		translate_errors();
    575 	return bindname;
    576 }
    577 
    578 char **
    579 hes_resolve(name, type)
    580 	const char	*name;
    581 	const char	*type;
    582 {
    583 	static char	**list;
    584 
    585 	_DIAGASSERT(name != NULL);
    586 	_DIAGASSERT(type != NULL);
    587 #ifdef _DIAGNOSTIC
    588 	if (name == NULL || type == NULL)
    589 		return (NULL);
    590 #endif
    591 
    592 	if (init_context() < 0)
    593 		return NULL;
    594 
    595 	/*
    596 	 * In the old Hesiod interface, the caller was responsible for
    597 	 * freeing the returned strings but not the vector of strings itself.
    598 	 */
    599 	if (list)
    600 		free(list);
    601 
    602 	list = hesiod_resolve(context, name, type);
    603 	if (!list)
    604 		translate_errors();
    605 	return list;
    606 }
    607 
    608 int
    609 hes_error()
    610 {
    611 	return errval;
    612 }
    613 
    614 void
    615 hes_free(hp)
    616 	char **hp;
    617 {
    618 	hesiod_free_list(context, hp);
    619 }
    620 
    621 static int
    622 init_context()
    623 {
    624 	if (!inited) {
    625 		inited = 1;
    626 		if (hesiod_init(&context) < 0) {
    627 			errval = HES_ER_CONFIG;
    628 			return -1;
    629 		}
    630 		errval = HES_ER_OK;
    631 	}
    632 	return 0;
    633 }
    634 
    635 static void
    636 translate_errors()
    637 {
    638 	switch (errno) {
    639 	case ENOENT:
    640 		errval = HES_ER_NOTFOUND;
    641 		break;
    642 	case ECONNREFUSED:
    643 	case EMSGSIZE:
    644 		errval = HES_ER_NET;
    645 		break;
    646 	case EFAULT:
    647 	case ENOMEM:
    648 	default:
    649 		/* Not a good match, but the best we can do. */
    650 		errval = HES_ER_CONFIG;
    651 		break;
    652 	}
    653 }
    654