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ns_name.c revision 1.4
      1 /*	$NetBSD: ns_name.c,v 1.4 2022/04/03 01:10:58 christos Exp $	*/
      2 
      3 /*
      4  * Copyright (C) 2004-2022 Internet Systems Consortium, Inc. ("ISC")
      5  * Copyright (c) 1996-2003 by Internet Software Consortium
      6  *
      7  * This Source Code Form is subject to the terms of the Mozilla Public
      8  * License, v. 2.0. If a copy of the MPL was not distributed with this
      9  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
     10  *
     11  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
     12  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
     13  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
     14  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
     15  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
     16  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
     17  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
     18  *
     19  *   Internet Systems Consortium, Inc.
     20  *   PO Box 360
     21  *   Newmarket, NH 03857 USA
     22  *   <info (at) isc.org>
     23  *   http://www.isc.org/
     24  */
     25 
     26 #include <sys/cdefs.h>
     27 __RCSID("$NetBSD: ns_name.c,v 1.4 2022/04/03 01:10:58 christos Exp $");
     28 
     29 #include <sys/types.h>
     30 
     31 #include <netinet/in.h>
     32 #include <sys/socket.h>
     33 
     34 #include <errno.h>
     35 #include <string.h>
     36 #include <ctype.h>
     37 
     38 #include "ns_name.h"
     39 #include "arpa/nameser.h"
     40 
     41 /* Data. */
     42 
     43 static const char	digits[] = "0123456789";
     44 
     45 /* Forward. */
     46 
     47 static int		special(int);
     48 static int		printable(int);
     49 static int		dn_find(const u_char *, const u_char *,
     50 				const u_char * const *,
     51 				const u_char * const *);
     52 
     53 /* Public. */
     54 
     55 /*
     56  * MRns_name_len(eom, src)
     57  *	Compute the length of encoded uncompressed domain name.
     58  * return:
     59  *	-1 if it fails, or to be consumed octets if it succeeds.
     60  */
     61 int
     62 MRns_name_len(const u_char *eom, const u_char *src)
     63 {
     64 	const u_char *srcp;
     65 	unsigned n;
     66 	int len;
     67 
     68 	len = -1;
     69 	srcp = src;
     70 	if (srcp >= eom) {
     71 		errno = EMSGSIZE;
     72 		return (-1);
     73 	}
     74 	/* Fetch next label in domain name. */
     75 	while ((n = *srcp++) != 0) {
     76 		/* Limit checks. */
     77 		if (srcp + n >= eom) {
     78 			errno = EMSGSIZE;
     79 			return (-1);
     80 		}
     81 		srcp += n;
     82 	}
     83 	if (len < 0)
     84 		len = srcp - src;
     85 	return (len);
     86 }
     87 
     88 /*
     89  * MRns_name_ntop(src, dst, dstsiz)
     90  *	Convert an encoded domain name to printable ascii as per RFC1035.
     91  * return:
     92  *	Number of bytes written to buffer, or -1 (with errno set)
     93  * notes:
     94  *	The root is returned as "."
     95  *	All other domains are returned in non absolute form
     96  */
     97 int
     98 MRns_name_ntop(const u_char *src, char *dst, size_t dstsiz) {
     99 	const u_char *cp;
    100 	char *dn, *eom;
    101 	u_char c;
    102 	u_int n;
    103 
    104 	cp = src;
    105 	dn = dst;
    106 	eom = dst + dstsiz;
    107 
    108 	while ((n = *cp++) != 0) {
    109 		if ((n & NS_CMPRSFLGS) != 0) {
    110 			/* Some kind of compression pointer. */
    111 			errno = EMSGSIZE;
    112 			return (-1);
    113 		}
    114 		if (dn != dst) {
    115 			if (dn >= eom) {
    116 				errno = EMSGSIZE;
    117 				return (-1);
    118 			}
    119 			*dn++ = '.';
    120 		}
    121 		if (dn + n >= eom) {
    122 			errno = EMSGSIZE;
    123 			return (-1);
    124 		}
    125 		for ((void)NULL; n > 0; n--) {
    126 			c = *cp++;
    127 			if (special(c)) {
    128 				if (dn + 1 >= eom) {
    129 					errno = EMSGSIZE;
    130 					return (-1);
    131 				}
    132 				*dn++ = '\\';
    133 				*dn++ = (char)c;
    134 			} else if (!printable(c)) {
    135 				if (dn + 3 >= eom) {
    136 					errno = EMSGSIZE;
    137 					return (-1);
    138 				}
    139 				*dn++ = '\\';
    140 				*dn++ = digits[c / 100];
    141 				*dn++ = digits[(c % 100) / 10];
    142 				*dn++ = digits[c % 10];
    143 			} else {
    144 				if (dn >= eom) {
    145 					errno = EMSGSIZE;
    146 					return (-1);
    147 				}
    148 				*dn++ = (char)c;
    149 			}
    150 		}
    151 	}
    152 	if (dn == dst) {
    153 		if (dn >= eom) {
    154 			errno = EMSGSIZE;
    155 			return (-1);
    156 		}
    157 		*dn++ = '.';
    158 	}
    159 	if (dn >= eom) {
    160 		errno = EMSGSIZE;
    161 		return (-1);
    162 	}
    163 	*dn++ = '\0';
    164 	return (dn - dst);
    165 }
    166 
    167 /*
    168  * MRns_name_pton(src, dst, dstsiz)
    169  *	Convert a ascii string into an encoded domain name as per RFC1035.
    170  * return:
    171  *	-1 if it fails
    172  *	1 if string was fully qualified
    173  *	0 is string was not fully qualified
    174  * notes:
    175  *	Enforces label and domain length limits.
    176  */
    177 
    178 int
    179 MRns_name_pton(const char *src, u_char *dst, size_t dstsiz) {
    180 	u_char *label, *bp, *eom;
    181 	int c, n, escaped;
    182 	char *cp;
    183 
    184 	escaped = 0;
    185 	bp = dst;
    186 	eom = dst + dstsiz;
    187 	label = bp++;
    188 
    189 	while ((c = *src++) != 0) {
    190 		if (escaped) {
    191 			if ((cp = strchr(digits, c)) != NULL) {
    192 				n = (cp - digits) * 100;
    193 				if ((c = *src++) == 0 ||
    194 				    (cp = strchr(digits, c)) == NULL) {
    195 					errno = EMSGSIZE;
    196 					return (-1);
    197 				}
    198 				n += (cp - digits) * 10;
    199 				if ((c = *src++) == 0 ||
    200 				    (cp = strchr(digits, c)) == NULL) {
    201 					errno = EMSGSIZE;
    202 					return (-1);
    203 				}
    204 				n += (cp - digits);
    205 				if (n > 255) {
    206 					errno = EMSGSIZE;
    207 					return (-1);
    208 				}
    209 				c = n;
    210 			}
    211 			escaped = 0;
    212 		} else if (c == '\\') {
    213 			escaped = 1;
    214 			continue;
    215 		} else if (c == '.') {
    216 			c = (bp - label - 1);
    217 			if ((c & NS_CMPRSFLGS) != 0) {	/* Label too big. */
    218 				errno = EMSGSIZE;
    219 				return (-1);
    220 			}
    221 			if (label >= eom) {
    222 				errno = EMSGSIZE;
    223 				return (-1);
    224 			}
    225 			*label = c;
    226 			/* Fully qualified ? */
    227 			if (*src == '\0') {
    228 				if (c != 0) {
    229 					if (bp >= eom) {
    230 						errno = EMSGSIZE;
    231 						return (-1);
    232 					}
    233 					*bp++ = '\0';
    234 				}
    235 				if ((bp - dst) > MAXCDNAME) {
    236 					errno = EMSGSIZE;
    237 					return (-1);
    238 				}
    239 				return (1);
    240 			}
    241 			if (c == 0 || *src == '.') {
    242 				errno = EMSGSIZE;
    243 				return (-1);
    244 			}
    245 			label = bp++;
    246 			continue;
    247 		}
    248 		if (bp >= eom) {
    249 			errno = EMSGSIZE;
    250 			return (-1);
    251 		}
    252 		*bp++ = (u_char)c;
    253 	}
    254 	c = (bp - label - 1);
    255 	if ((c & NS_CMPRSFLGS) != 0) {		/* Label too big. */
    256 		errno = EMSGSIZE;
    257 		return (-1);
    258 	}
    259 	if (label >= eom) {
    260 		errno = EMSGSIZE;
    261 		return (-1);
    262 	}
    263 	*label = c;
    264 	if (c != 0) {
    265 		if (bp >= eom) {
    266 			errno = EMSGSIZE;
    267 			return (-1);
    268 		}
    269 		*bp++ = 0;
    270 	}
    271 	if ((bp - dst) > MAXCDNAME) {	/* src too big */
    272 		errno = EMSGSIZE;
    273 		return (-1);
    274 	}
    275 	return (0);
    276 }
    277 
    278 #ifdef notdef
    279 /*
    280  * MRns_name_ntol(src, dst, dstsiz)
    281  *	Convert a network strings labels into all lowercase.
    282  * return:
    283  *	Number of bytes written to buffer, or -1 (with errno set)
    284  * notes:
    285  *	Enforces label and domain length limits.
    286  */
    287 
    288 int
    289 MRns_name_ntol(const u_char *src, u_char *dst, size_t dstsiz) {
    290 	const u_char *cp;
    291 	u_char *dn, *eom;
    292 	u_char c;
    293 	u_int n;
    294 
    295 	cp = src;
    296 	dn = dst;
    297 	eom = dst + dstsiz;
    298 
    299 	if (dn >= eom) {
    300 		errno = EMSGSIZE;
    301 		return (-1);
    302 	}
    303 	while ((n = *cp++) != 0) {
    304 		if ((n & NS_CMPRSFLGS) != 0) {
    305 			/* Some kind of compression pointer. */
    306 			errno = EMSGSIZE;
    307 			return (-1);
    308 		}
    309 		*dn++ = n;
    310 		if (dn + n >= eom) {
    311 			errno = EMSGSIZE;
    312 			return (-1);
    313 		}
    314 		for ((void)NULL; n > 0; n--) {
    315 			c = *cp++;
    316 			if (isupper(c))
    317 				*dn++ = tolower(c);
    318 			else
    319 				*dn++ = c;
    320 		}
    321 	}
    322 	*dn++ = '\0';
    323 	return (dn - dst);
    324 }
    325 #endif
    326 
    327 /*
    328  * MRns_name_unpack(msg, eom, src, dst, dstsiz)
    329  *	Unpack a domain name from a message, source may be compressed.
    330  * return:
    331  *	-1 if it fails, or consumed octets if it succeeds.
    332  */
    333 int
    334 MRns_name_unpack(const u_char *msg, const u_char *eom, const u_char *src,
    335 	         u_char *dst, size_t dstsiz)
    336 {
    337 	const u_char *srcp, *dstlim;
    338 	u_char *dstp;
    339 	unsigned n;
    340 	int len;
    341 	int checked;
    342 
    343 	len = -1;
    344 	checked = 0;
    345 	dstp = dst;
    346 	srcp = src;
    347 	dstlim = dst + dstsiz;
    348 	if (srcp < msg || srcp >= eom) {
    349 		errno = EMSGSIZE;
    350 		return (-1);
    351 	}
    352 	/* Fetch next label in domain name. */
    353 	while ((n = *srcp++) != 0) {
    354 		/* Check for indirection. */
    355 		switch (n & NS_CMPRSFLGS) {
    356 		case 0:
    357 			/* Limit checks. */
    358 			if (dstp + n + 1 >= dstlim || srcp + n >= eom) {
    359 				errno = EMSGSIZE;
    360 				return (-1);
    361 			}
    362 			checked += n + 1;
    363 			*dstp++ = n;
    364 			memcpy(dstp, srcp, n);
    365 			dstp += n;
    366 			srcp += n;
    367 			break;
    368 
    369 		case NS_CMPRSFLGS:
    370 			if (srcp >= eom) {
    371 				errno = EMSGSIZE;
    372 				return (-1);
    373 			}
    374 			if (len < 0)
    375 				len = srcp - src + 1;
    376 			n = ((n & 0x3f) << 8) | (*srcp & 0xff);
    377 			if (n >= eom - msg) {  /* Out of range. */
    378 				errno = EMSGSIZE;
    379 				return (-1);
    380 			}
    381 			srcp = msg + n;
    382 			checked += 2;
    383 			/*
    384 			 * Check for loops in the compressed name;
    385 			 * if we've looked at the whole message,
    386 			 * there must be a loop.
    387 			 */
    388 			if (checked >= eom - msg) {
    389 				errno = EMSGSIZE;
    390 				return (-1);
    391 			}
    392 			break;
    393 
    394 		default:
    395 			errno = EMSGSIZE;
    396 			return (-1);			/* flag error */
    397 		}
    398 	}
    399 	*dstp = '\0';
    400 	if (len < 0)
    401 		len = srcp - src;
    402 	return (len);
    403 }
    404 
    405 /*
    406  * MRns_name_pack(src, dst, dstsiz, dnptrs, lastdnptr)
    407  *	Pack domain name 'domain' into 'comp_dn'.
    408  * return:
    409  *	Size of the compressed name, or -1.
    410  * notes:
    411  *	'dnptrs' is an array of pointers to previous compressed names.
    412  *	dnptrs[0] is a pointer to the beginning of the message. The array
    413  *	ends with NULL.
    414  *	'lastdnptr' is a pointer to the end of the array pointed to
    415  *	by 'dnptrs'.
    416  * Side effects:
    417  *	The list of pointers in dnptrs is updated for labels inserted into
    418  *	the message as we compress the name.  If 'dnptr' is NULL, we don't
    419  *	try to compress names. If 'lastdnptr' is NULL, we don't update the
    420  *	list.
    421  */
    422 int
    423 MRns_name_pack(const u_char *src, u_char *dst, unsigned dstsiz,
    424 	       const u_char **dnptrs, const u_char **lastdnptr)
    425 {
    426 	u_char *dstp;
    427 	const u_char **cpp, **lpp, *eob, *msg;
    428 	const u_char *srcp;
    429 	unsigned n;
    430 	int l;
    431 
    432 	srcp = src;
    433 	dstp = dst;
    434 	eob = dstp + dstsiz;
    435 	lpp = cpp = NULL;
    436 	if (dnptrs != NULL) {
    437 		if ((msg = *dnptrs++) != NULL) {
    438 			for (cpp = dnptrs; *cpp != NULL; cpp++)
    439 				(void)NULL;
    440 			lpp = cpp;	/* end of list to search */
    441 		}
    442 	} else
    443 		msg = NULL;
    444 
    445 	/* make sure the domain we are about to add is legal */
    446 	l = 0;
    447 	do {
    448 		n = *srcp;
    449 		if ((n & NS_CMPRSFLGS) != 0) {
    450 			errno = EMSGSIZE;
    451 			return (-1);
    452 		}
    453 		l += n + 1;
    454 		if (l > MAXCDNAME) {
    455 			errno = EMSGSIZE;
    456 			return (-1);
    457 		}
    458 		srcp += n + 1;
    459 	} while (n != 0);
    460 
    461 	/* from here on we need to reset compression pointer array on error */
    462 	srcp = src;
    463 	do {
    464 		/* Look to see if we can use pointers. */
    465 		n = *srcp;
    466 		if (n != 0 && msg != NULL) {
    467 			l = dn_find(srcp, msg, (const u_char * const *)dnptrs,
    468 				    (const u_char * const *)lpp);
    469 			if (l >= 0) {
    470 				if (dstp + 1 >= eob) {
    471 					goto cleanup;
    472 				}
    473 				*dstp++ = (l >> 8) | NS_CMPRSFLGS;
    474 				*dstp++ = l % 256;
    475 				return (dstp - dst);
    476 			}
    477 			/* Not found, save it. */
    478 			if (lastdnptr != NULL && cpp < lastdnptr - 1 &&
    479 			    (dstp - msg) < 0x4000) {
    480 				*cpp++ = dstp;
    481 				*cpp = NULL;
    482 			}
    483 		}
    484 		/* copy label to buffer */
    485 		if (n & NS_CMPRSFLGS) {		/* Should not happen. */
    486 			goto cleanup;
    487 		}
    488 		if (dstp + 1 + n >= eob) {
    489 			goto cleanup;
    490 		}
    491 		memcpy(dstp, srcp, n + 1);
    492 		srcp += n + 1;
    493 		dstp += n + 1;
    494 	} while (n != 0);
    495 
    496 	if (dstp > eob) {
    497 cleanup:
    498 		if (msg != NULL)
    499 			*lpp = NULL;
    500 		errno = EMSGSIZE;
    501 		return (-1);
    502 	}
    503 	return (dstp - dst);
    504 }
    505 
    506 /*
    507  * MRns_name_uncompress(msg, eom, src, dst, dstsiz)
    508  *	Expand compressed domain name to presentation format.
    509  * return:
    510  *	Number of bytes read out of `src', or -1 (with errno set).
    511  * note:
    512  *	Root domain returns as "." not "".
    513  */
    514 static int
    515 MRns_name_uncompress(const u_char *msg, const u_char *eom, const u_char *src,
    516 		     char *dst, size_t dstsiz)
    517 {
    518 	u_char tmp[NS_MAXCDNAME];
    519 	int n;
    520 
    521 	if ((n = MRns_name_unpack(msg, eom, src, tmp, sizeof tmp)) == -1)
    522 		return (-1);
    523 	if (MRns_name_ntop(tmp, dst, dstsiz) == -1)
    524 		return (-1);
    525 	return (n);
    526 }
    527 
    528 /*
    529  * MRns_name_compress(src, dst, dstsiz, dnptrs, lastdnptr)
    530  *	Compress a domain name into wire format, using compression pointers.
    531  * return:
    532  *	Number of bytes consumed in `dst' or -1 (with errno set).
    533  * notes:
    534  *	'dnptrs' is an array of pointers to previous compressed names.
    535  *	dnptrs[0] is a pointer to the beginning of the message.
    536  *	The list ends with NULL.  'lastdnptr' is a pointer to the end of the
    537  *	array pointed to by 'dnptrs'. Side effect is to update the list of
    538  *	pointers for labels inserted into the message as we compress the name.
    539  *	If 'dnptr' is NULL, we don't try to compress names. If 'lastdnptr'
    540  *	is NULL, we don't update the list.
    541  */
    542 int
    543 MRns_name_compress(const char *src, u_char *dst, size_t dstsiz,
    544 		 const u_char **dnptrs, const u_char **lastdnptr)
    545 {
    546 	u_char tmp[NS_MAXCDNAME];
    547 
    548 	if (MRns_name_pton(src, tmp, sizeof tmp) == -1)
    549 		return (-1);
    550 	return (MRns_name_pack(tmp, dst, dstsiz, dnptrs, lastdnptr));
    551 }
    552 
    553 #ifdef notdef
    554 /*
    555  * MRns_name_skip(ptrptr, eom)
    556  *	Advance *ptrptr to skip over the compressed name it points at.
    557  * return:
    558  *	0 on success, -1 (with errno set) on failure.
    559  */
    560 int
    561 MRns_name_skip(const u_char **ptrptr, const u_char *eom) {
    562 	const u_char *cp;
    563 	u_int n;
    564 
    565 	cp = *ptrptr;
    566 	while (cp < eom && (n = *cp++) != 0) {
    567 		/* Check for indirection. */
    568 		switch (n & NS_CMPRSFLGS) {
    569 		case 0:			/* normal case, n == len */
    570 			cp += n;
    571 			continue;
    572 		case NS_CMPRSFLGS:	/* indirection */
    573 			cp++;
    574 			break;
    575 		default:		/* illegal type */
    576 			errno = EMSGSIZE;
    577 			return (-1);
    578 		}
    579 		break;
    580 	}
    581 	if (cp > eom) {
    582 		errno = EMSGSIZE;
    583 		return (-1);
    584 	}
    585 	*ptrptr = cp;
    586 	return (0);
    587 }
    588 #endif
    589 
    590 /* Private. */
    591 
    592 /*
    593  * special(ch)
    594  *	Thinking in noninternationalized USASCII (per the DNS spec),
    595  *	is this characted special ("in need of quoting") ?
    596  * return:
    597  *	boolean.
    598  */
    599 static int
    600 special(int ch) {
    601 	switch (ch) {
    602 	case 0x22: /* '"' */
    603 	case 0x2E: /* '.' */
    604 	case 0x3B: /* ';' */
    605 	case 0x5C: /* '\\' */
    606 	/* Special modifiers in zone files. */
    607 	case 0x40: /* '@' */
    608 	case 0x24: /* '$' */
    609 		return (1);
    610 	default:
    611 		return (0);
    612 	}
    613 }
    614 
    615 /*
    616  * printable(ch)
    617  *	Thinking in noninternationalized USASCII (per the DNS spec),
    618  *	is this character visible and not a space when printed ?
    619  * return:
    620  *	boolean.
    621  */
    622 static int
    623 printable(int ch) {
    624 	return (ch > 0x20 && ch < 0x7f);
    625 }
    626 
    627 /*
    628  *	Thinking in noninternationalized USASCII (per the DNS spec),
    629  *	convert this character to lower case if it's upper case.
    630  */
    631 static int
    632 mklower(int ch) {
    633 	if (ch >= 0x41 && ch <= 0x5A)
    634 		return (ch + 0x20);
    635 	return (ch);
    636 }
    637 
    638 /*
    639  * dn_find(domain, msg, dnptrs, lastdnptr)
    640  *	Search for the counted-label name in an array of compressed names.
    641  * return:
    642  *	offset from msg if found, or -1.
    643  * notes:
    644  *	dnptrs is the pointer to the first name on the list,
    645  *	not the pointer to the start of the message.
    646  */
    647 static int
    648 dn_find(const u_char *domain, const u_char *msg,
    649 	const u_char * const *dnptrs,
    650 	const u_char * const *lastdnptr)
    651 {
    652 	const u_char *dn, *cp, *sp;
    653 	const u_char * const *cpp;
    654 	u_int n;
    655 
    656 	for (cpp = dnptrs; cpp < lastdnptr; cpp++) {
    657 		dn = domain;
    658 		sp = cp = *cpp;
    659 		while ((n = *cp++) != 0) {
    660 			/*
    661 			 * check for indirection
    662 			 */
    663 			switch (n & NS_CMPRSFLGS) {
    664 			case 0:			/* normal case, n == len */
    665 				if (n != *dn++)
    666 					goto next;
    667 				for ((void)NULL; n > 0; n--)
    668 					if (mklower(*dn++) != mklower(*cp++))
    669 						goto next;
    670 				/* Is next root for both ? */
    671 				if (*dn == '\0' && *cp == '\0')
    672 					return (sp - msg);
    673 				if (*dn)
    674 					continue;
    675 				goto next;
    676 
    677 			case NS_CMPRSFLGS:	/* indirection */
    678 				cp = msg + (((n & 0x3f) << 8) | *cp);
    679 				break;
    680 
    681 			default:	/* illegal type */
    682 				errno = EMSGSIZE;
    683 				return (-1);
    684 			}
    685 		}
    686  next: ;
    687 	}
    688 	errno = ENOENT;
    689 	return (-1);
    690 }
    691 
    692 /*!
    693  * \brief Creates a string of comma-separated domain-names from a
    694  * compressed list
    695  *
    696  * Produces a null-terminated string of comma-separated domain-names from
    697  * a buffer containing a compressed list of domain-names. The names will
    698  * be dotted and without enclosing quotes. For example:
    699  * If a compressed list contains the follwoing two domain names:
    700  *
    701  *  a. one.two.com
    702  *  b. three.four.com
    703  *
    704  * The compressed data will look like this:
    705  *
    706  *  03 6f 6e 65 03 74 77 6f 03 63 6f 6d 00 05 74 68
    707  *  72 65 65 04 66 6f 75 72 c0 08
    708  *
    709  * and will decompress into:
    710  *
    711  *  one.two.com,three.four.com
    712  *
    713  * \param  buf - buffer containing the compressed list of domain-names
    714  * \param  buflen - length of compressed list of domain-names
    715  * \param  dst_buf - buffer to receive the decompressed list
    716  * \param  dst_size - size of the destination buffer
    717  *
    718  * \return the length of the decompressed string when successful, -1 on
    719  * error.
    720  */
    721 int MRns_name_uncompress_list(const unsigned char* buf, int buflen,
    722 			      char* dst_buf, size_t dst_size)
    723 {
    724 	const unsigned char* src = buf;
    725 	char* dst = dst_buf;
    726 	int consumed = 1;
    727 	int dst_remaining = dst_size;
    728 	int added_len = 0;
    729 	int first_pass = 1;
    730 
    731 	if (!buf || buflen == 0 || *buf == 0x00) {
    732 		/* nothing to do */
    733 		*dst = 0;
    734 		return (0);
    735 	}
    736 
    737 	while ((consumed > 0) && (src < (buf + buflen)))
    738 	{
    739 		if (dst_remaining <= 0) {
    740 			errno = EMSGSIZE;
    741 			return (-1);
    742 		}
    743 
    744 		if (!first_pass) {
    745 			*dst++ = ',';
    746 			*dst = '\0';
    747 			dst_remaining--;
    748 		}
    749 
    750 		consumed = MRns_name_uncompress(buf, buf + buflen, src,
    751 						dst, dst_remaining);
    752 		if (consumed < 0) {
    753 			return (-1);
    754 		}
    755 
    756 		src += consumed;
    757 		added_len = strlen(dst);
    758 		dst_remaining -= added_len;
    759 		dst += added_len;
    760 		first_pass = 0;
    761 	}
    762 	*dst='\0';
    763 
    764 	/* return the length of the uncompressed list string */
    765 	return (strlen(dst_buf));
    766 }
    767 
    768 /*!
    769  * \brief Creates a compressed list from a string of comma-separated
    770  * domain-names
    771  *
    772  * Produces a buffer containing a compressed data version of a list of
    773  * domain-names extracted from a comma-separated string. Given a string
    774  * containing:
    775  *
    776  *  one.two.com,three.four.com
    777  *
    778  * It will compress this into:
    779  *
    780  *  03 6f 6e 65 03 74 77 6f 03 63 6f 6d 00 05 74 68
    781  *  72 65 65 04 66 6f 75 72 c0 08
    782  *
    783  * \param  buf - buffer containing the uncompressed string of domain-names
    784  * \param  buflen - length of uncompressed string of domain-names
    785  * \param  compbuf - buffer to receive the compressed list
    786  * \param  compbuf_size - size of the compression buffer
    787  *
    788  * \return the length of the compressed data when successful, -1 on error.
    789  */
    790 int MRns_name_compress_list(const char* buf, int buflen,
    791 	unsigned char* compbuf, size_t compbuf_size)
    792 {
    793 	char cur_name[NS_MAXCDNAME];
    794 	const unsigned char *dnptrs[256], **lastdnptr;
    795 	const char* src;
    796 	const char* src_end;
    797 	unsigned clen = 0;
    798 	int result = 0;
    799 
    800 	memset(compbuf, 0, compbuf_size);
    801 	memset(dnptrs, 0, sizeof(dnptrs));
    802 	dnptrs[0] = compbuf;
    803 	lastdnptr = &dnptrs[255];
    804 
    805 	src = buf;
    806 	src_end = buf + buflen;
    807 	while (src < src_end) {
    808 		char *comma = strchr(src, ',');
    809 		int copylen = ((comma != NULL) ? comma - src : strlen(src));
    810 		if (copylen > (sizeof(cur_name) - 1)) {
    811 			errno = EMSGSIZE;
    812 			return (-1);
    813 		}
    814 
    815 		memcpy(cur_name, src, copylen);
    816 		cur_name[copylen] = '\0';
    817 		src += copylen + 1;
    818 
    819 		result = MRns_name_compress(cur_name, compbuf + clen,
    820 					    compbuf_size - clen,
    821 					    dnptrs, lastdnptr);
    822 
    823 		if (result < 0) {
    824 			return (-1);
    825 		}
    826 
    827 		clen += result;
    828 	}
    829 
    830 	/* return size of compressed list */
    831 	return(clen);
    832 }
    833