ns_name.c

   1 /*
   2  * Copyright (c) 1996,1999 by Internet Software Consortium.
   3  *
   4  * Permission to use, copy, modify, and distribute this software for any
   5  * purpose with or without fee is hereby granted, provided that the above
   6  * copyright notice and this permission notice appear in all copies.
   7  *
   8  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
   9  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  10  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  11  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  12  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  13  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  14  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  15  * SOFTWARE.
  16  */
  17
  18 #ifndef __APPLE__
  19 #ifndef lint
  20 static const char rcsid[] = "$Id: ns_name.c,v 1.1 2006/03/01 19:01:36 majka Exp $";
  21 #endif
  22 #endif
  23
  24 #ifndef __APPLE__
  25 #include "port_before.h"
  26 #endif
  27
  28 #include <sys/types.h>
  29
  30 #include <netinet/in.h>
  31 #include <arpa/nameser.h>
  32
  33 #include <errno.h>
  34 #include <resolv.h>
  35 #include <string.h>
  36 #include <ctype.h>
  37 #include <stdlib.h>
  38 #include <limits.h>
  39
  40 #ifndef __APPLE__
  41 #include "port_after.h"
  42 #endif
  43
  44 #ifdef SPRINTF_CHAR
  45 # define SPRINTF(x) strlen(sprintf/**/x)
  46 #else
  47 # define SPRINTF(x) ((size_t)sprintf x)
  48 #endif
  49
  50 #define NS_TYPE_ELT                     0x40 /* EDNS0 extended label type */
  51 #define DNS_LABELTYPE_BITSTRING         0x41
  52
  53 /* Data. */
  54
  55 static const char       digits[] = "0123456789";
  56
  57 static const char digitvalue[256] = {
  58         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*16*/
  59         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*32*/
  60         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*48*/
  61          0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1, /*64*/
  62         -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*80*/
  63         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*96*/
  64         -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*112*/
  65         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*128*/
  66         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  67         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  68         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  69         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  70         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  71         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  72         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  73         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*256*/
  74 };
  75
  76 /* Forward. */
  77
  78 static int              special(int);
  79 static int              printable(int);
  80 static int              dn_find(const u_char *, const u_char *,
  81                                 const u_char * const *,
  82                                 const u_char * const *);
  83 static int              encode_bitsring(const char **, const char *,
  84                                         char **, char **, const char *);
  85 static int              labellen(const u_char *);
  86 static int              decode_bitstring(const char **, char *, const char *);
  87
  88 /* Public. */
  89
  90 /*
  91  * ns_name_ntop(src, dst, dstsiz)
  92  *      Convert an encoded domain name to printable ascii as per RFC1035.
  93  * return:
  94  *      Number of bytes written to buffer, or -1 (with errno set)
  95  * notes:
  96  *      The root is returned as "."
  97  *      All other domains are returned in non absolute form
  98  */
  99 int
 100 ns_name_ntop(const u_char *src, char *dst, size_t dstsiz)
 101 {
 102         const u_char *cp;
 103         char *dn, *eom;
 104         u_char c;
 105         u_int n;
 106         int l;
 107
 108         cp = src;
 109         dn = dst;
 110         eom = dst + dstsiz;
 111
 112         while ((n = *cp++) != 0) {
 113                 if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
 114                         /* Some kind of compression pointer. */
 115                         errno = EMSGSIZE;
 116                         return (-1);
 117                 }
 118                 if (dn != dst) {
 119                         if (dn >= eom) {
 120                                 errno = EMSGSIZE;
 121                                 return (-1);
 122                         }
 123                         *dn++ = '.';
 124                 }
 125                 if ((l = labellen(cp - 1)) < 0) {
 126                         errno = EMSGSIZE; /* XXX */
 127                         return(-1);
 128                 }
 129                 if (dn + l >= eom) {
 130                         errno = EMSGSIZE;
 131                         return (-1);
 132                 }
 133                 if ((n & NS_CMPRSFLGS) == NS_TYPE_ELT) {
 134                         int m;
 135
 136                         if (n != DNS_LABELTYPE_BITSTRING) {
 137                                 /* XXX: labellen should reject this case */
 138                                 errno = EINVAL;
 139                                 return(-1);
 140                         }
 141                         if ((m = decode_bitstring((const char **)&cp, dn, eom)) < 0)
 142                         {
 143                                 errno = EMSGSIZE;
 144                                 return(-1);
 145                         }
 146                         dn += m;
 147                         continue;
 148                 }
 149                 for ((void)NULL; l > 0; l--) {
 150                         c = *cp++;
 151                         if (special(c)) {
 152                                 if (dn + 1 >= eom) {
 153                                         errno = EMSGSIZE;
 154                                         return (-1);
 155                                 }
 156                                 *dn++ = '\\';
 157                                 *dn++ = (char)c;
 158                         } else if (!printable(c)) {
 159                                 if (dn + 3 >= eom) {
 160                                         errno = EMSGSIZE;
 161                                         return (-1);
 162                                 }
 163                                 *dn++ = '\\';
 164                                 *dn++ = digits[c / 100];
 165                                 *dn++ = digits[(c % 100) / 10];
 166                                 *dn++ = digits[c % 10];
 167                         } else {
 168                                 if (dn >= eom) {
 169                                         errno = EMSGSIZE;
 170                                         return (-1);
 171                                 }
 172                                 *dn++ = (char)c;
 173                         }
 174                 }
 175         }
 176         if (dn == dst) {
 177                 if (dn >= eom) {
 178                         errno = EMSGSIZE;
 179                         return (-1);
 180                 }
 181                 *dn++ = '.';
 182         }
 183         if (dn >= eom) {
 184                 errno = EMSGSIZE;
 185                 return (-1);
 186         }
 187         *dn++ = '\0';
 188         return (dn - dst);
 189 }
 190
 191 /*
 192  * ns_name_pton(src, dst, dstsiz)
 193  *      Convert a ascii string into an encoded domain name as per RFC1035.
 194  * return:
 195  *      -1 if it fails
 196  *      1 if string was fully qualified
 197  *      0 is string was not fully qualified
 198  * notes:
 199  *      Enforces label and domain length limits.
 200  */
 201
 202 int
 203 ns_name_pton(const char *src, u_char *dst, size_t dstsiz)
 204 {
 205         u_char *label, *bp, *eom;
 206         int c, n, escaped, e = 0;
 207         char *cp;
 208
 209         escaped = 0;
 210         bp = dst;
 211         eom = dst + dstsiz;
 212         label = bp++;
 213
 214         while ((c = *src++) != 0) {
 215                 if (escaped) {
 216                         if (c == '[') { /* start a bit string label */
 217                                 if ((cp = strchr(src, ']')) == NULL) {
 218                                         errno = EINVAL; /* ??? */
 219                                         return(-1);
 220                                 }
 221                                 if ((e = encode_bitsring(&src,
 222                                                          cp + 2,
 223                                                          (char **)&label,
 224                                                          (char **)&bp,
 225                                                          (const char *)eom))
 226                                     != 0) {
 227                                         errno = e;
 228                                         return(-1);
 229                                 }
 230                                 escaped = 0;
 231                                 label = bp++;
 232                                 if ((c = *src++) == 0)
 233                                         goto done;
 234                                 else if (c != '.') {
 235                                         errno = EINVAL;
 236                                         return(-1);
 237                                 }
 238                                 continue;
 239                         }
 240                         else if ((cp = strchr(digits, c)) != NULL) {
 241                                 n = (cp - digits) * 100;
 242                                 if ((c = *src++) == 0 ||
 243                                     (cp = strchr(digits, c)) == NULL) {
 244                                         errno = EMSGSIZE;
 245                                         return (-1);
 246                                 }
 247                                 n += (cp - digits) * 10;
 248                                 if ((c = *src++) == 0 ||
 249                                     (cp = strchr(digits, c)) == NULL) {
 250                                         errno = EMSGSIZE;
 251                                         return (-1);
 252                                 }
 253                                 n += (cp - digits);
 254                                 if (n > 255) {
 255                                         errno = EMSGSIZE;
 256                                         return (-1);
 257                                 }
 258                                 c = n;
 259                         }
 260                         escaped = 0;
 261                 } else if (c == '\\') {
 262                         escaped = 1;
 263                         continue;
 264                 } else if (c == '.') {
 265                         c = (bp - label - 1);
 266                         if ((c & NS_CMPRSFLGS) != 0) {  /* Label too big. */
 267                                 errno = EMSGSIZE;
 268                                 return (-1);
 269                         }
 270                         if (label >= eom) {
 271                                 errno = EMSGSIZE;
 272                                 return (-1);
 273                         }
 274                         *label = c;
 275                         /* Fully qualified ? */
 276                         if (*src == '\0') {
 277                                 if (c != 0) {
 278                                         if (bp >= eom) {
 279                                                 errno = EMSGSIZE;
 280                                                 return (-1);
 281                                         }
 282                                         *bp++ = '\0';
 283                                 }
 284                                 if ((bp - dst) > NS_MAXCDNAME) {
 285                                         errno = EMSGSIZE;
 286                                         return (-1);
 287                                 }
 288                                 return (1);
 289                         }
 290                         if (c == 0 || *src == '.') {
 291                                 errno = EMSGSIZE;
 292                                 return (-1);
 293                         }
 294                         label = bp++;
 295                         continue;
 296                 }
 297                 if (bp >= eom) {
 298                         errno = EMSGSIZE;
 299                         return (-1);
 300                 }
 301                 *bp++ = (u_char)c;
 302         }
 303         c = (bp - label - 1);
 304         if ((c & NS_CMPRSFLGS) != 0) {          /* Label too big. */
 305                 errno = EMSGSIZE;
 306                 return (-1);
 307         }
 308   done:
 309         if (label >= eom) {
 310                 errno = EMSGSIZE;
 311                 return (-1);
 312         }
 313         *label = c;
 314         if (c != 0) {
 315                 if (bp >= eom) {
 316                         errno = EMSGSIZE;
 317                         return (-1);
 318                 }
 319                 *bp++ = 0;
 320         }
 321         if ((bp - dst) > NS_MAXCDNAME) {        /* src too big */
 322                 errno = EMSGSIZE;
 323                 return (-1);
 324         }
 325         return (0);
 326 }
 327
 328 /*
 329  * ns_name_ntol(src, dst, dstsiz)
 330  *      Convert a network strings labels into all lowercase.
 331  * return:
 332  *      Number of bytes written to buffer, or -1 (with errno set)
 333  * notes:
 334  *      Enforces label and domain length limits.
 335  */
 336
 337 int
 338 ns_name_ntol(const u_char *src, u_char *dst, size_t dstsiz)
 339 {
 340         const u_char *cp;
 341         u_char *dn, *eom;
 342         u_char c;
 343         u_int n;
 344         int l;
 345
 346         cp = src;
 347         dn = dst;
 348         eom = dst + dstsiz;
 349
 350         while ((n = *cp++) != 0) {
 351                 if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
 352                         /* Some kind of compression pointer. */
 353                         errno = EMSGSIZE;
 354                         return (-1);
 355                 }
 356                 *dn++ = n;
 357                 if ((l = labellen(cp - 1)) < 0) {
 358                         errno = EMSGSIZE;
 359                         return (-1);
 360                 }
 361                 if (dn + l >= eom) {
 362                         errno = EMSGSIZE;
 363                         return (-1);
 364                 }
 365                 for ((void)NULL; l > 0; l--) {
 366                         c = *cp++;
 367                         if (isupper(c))
 368                                 *dn++ = tolower(c);
 369                         else
 370                                 *dn++ = c;
 371                 }
 372         }
 373         *dn++ = '\0';
 374         return (dn - dst);
 375 }
 376
 377 /*
 378  * ns_name_unpack(msg, eom, src, dst, dstsiz)
 379  *      Unpack a domain name from a message, source may be compressed.
 380  * return:
 381  *      -1 if it fails, or consumed octets if it succeeds.
 382  */
 383 int
 384 ns_name_unpack(const u_char *msg, const u_char *eom, const u_char *src,
 385                u_char *dst, size_t dstsiz)
 386 {
 387         const u_char *srcp, *dstlim;
 388         u_char *dstp;
 389         int n, len, checked, l;
 390
 391         len = -1;
 392         checked = 0;
 393         dstp = dst;
 394         srcp = src;
 395         dstlim = dst + dstsiz;
 396         if (srcp < msg || srcp >= eom) {
 397                 errno = EMSGSIZE;
 398                 return (-1);
 399         }
 400         /* Fetch next label in domain name. */
 401         while ((n = *srcp++) != 0) {
 402                 /* Check for indirection. */
 403                 switch (n & NS_CMPRSFLGS) {
 404                 case 0:
 405                 case NS_TYPE_ELT:
 406                         /* Limit checks. */
 407                         if ((l = labellen(srcp - 1)) < 0) {
 408                                 errno = EMSGSIZE;
 409                                 return(-1);
 410                         }
 411                         if (dstp + l + 1 >= dstlim || srcp + l >= eom) {
 412                                 errno = EMSGSIZE;
 413                                 return (-1);
 414                         }
 415                         checked += l + 1;
 416                         *dstp++ = n;
 417                         memcpy(dstp, srcp, l);
 418                         dstp += l;
 419                         srcp += l;
 420                         break;
 421
 422                 case NS_CMPRSFLGS:
 423                         if (srcp >= eom) {
 424                                 errno = EMSGSIZE;
 425                                 return (-1);
 426                         }
 427                         if (len < 0)
 428                                 len = srcp - src + 1;
 429                         srcp = msg + (((n & 0x3f) << 8) | (*srcp & 0xff));
 430                         if (srcp < msg || srcp >= eom) {  /* Out of range. */
 431                                 errno = EMSGSIZE;
 432                                 return (-1);
 433                         }
 434                         checked += 2;
 435                         /*
 436                          * Check for loops in the compressed name;
 437                          * if we've looked at the whole message,
 438                          * there must be a loop.
 439                          */
 440                         if (checked >= eom - msg) {
 441                                 errno = EMSGSIZE;
 442                                 return (-1);
 443                         }
 444                         break;
 445
 446                 default:
 447                         errno = EMSGSIZE;
 448                         return (-1);                    /* flag error */
 449                 }
 450         }
 451         *dstp = '\0';
 452         if (len < 0)
 453                 len = srcp - src;
 454         return (len);
 455 }
 456
 457 /*
 458  * ns_name_pack(src, dst, dstsiz, dnptrs, lastdnptr)
 459  *      Pack domain name 'domain' into 'comp_dn'.
 460  * return:
 461  *      Size of the compressed name, or -1.
 462  * notes:
 463  *      'dnptrs' is an array of pointers to previous compressed names.
 464  *      dnptrs[0] is a pointer to the beginning of the message. The array
 465  *      ends with NULL.
 466  *      'lastdnptr' is a pointer to the end of the array pointed to
 467  *      by 'dnptrs'.
 468  * Side effects:
 469  *      The list of pointers in dnptrs is updated for labels inserted into
 470  *      the message as we compress the name.  If 'dnptr' is NULL, we don't
 471  *      try to compress names. If 'lastdnptr' is NULL, we don't update the
 472  *      list.
 473  */
 474 int
 475 ns_name_pack(const u_char *src, u_char *dst, int dstsiz,
 476              const u_char **dnptrs, const u_char **lastdnptr)
 477 {
 478         u_char *dstp;
 479         const u_char **cpp, **lpp, *eob, *msg;
 480         const u_char *srcp;
 481         int n, l, first = 1;
 482
 483         srcp = src;
 484         dstp = dst;
 485         eob = dstp + dstsiz;
 486         lpp = cpp = NULL;
 487         if (dnptrs != NULL) {
 488                 if ((msg = *dnptrs++) != NULL) {
 489                         for (cpp = dnptrs; *cpp != NULL; cpp++)
 490                                 (void)NULL;
 491                         lpp = cpp;      /* end of list to search */
 492                 }
 493         } else
 494                 msg = NULL;
 495
 496         /* make sure the domain we are about to add is legal */
 497         l = 0;
 498         do {
 499                 int l0;
 500
 501                 n = *srcp;
 502                 if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
 503                         errno = EMSGSIZE;
 504                         return (-1);
 505                 }
 506                 if ((l0 = labellen(srcp)) < 0) {
 507                         errno = EINVAL;
 508                         return(-1);
 509                 }
 510                 l += l0 + 1;
 511                 if (l > NS_MAXCDNAME) {
 512                         errno = EMSGSIZE;
 513                         return (-1);
 514                 }
 515                 srcp += l0 + 1;
 516         } while (n != 0);
 517
 518         /* from here on we need to reset compression pointer array on error */
 519         srcp = src;
 520         do {
 521                 /* Look to see if we can use pointers. */
 522                 n = *srcp;
 523                 if (n != 0 && msg != NULL) {
 524                         l = dn_find(srcp, msg, (const u_char * const *)dnptrs,
 525                                     (const u_char * const *)lpp);
 526                         if (l >= 0) {
 527                                 if (dstp + 1 >= eob) {
 528                                         goto cleanup;
 529                                 }
 530                                 *dstp++ = (l >> 8) | NS_CMPRSFLGS;
 531                                 *dstp++ = l % 256;
 532                                 return (dstp - dst);
 533                         }
 534                         /* Not found, save it. */
 535                         if (lastdnptr != NULL && cpp < lastdnptr - 1 &&
 536                             (dstp - msg) < 0x4000 && first) {
 537                                 *cpp++ = dstp;
 538                                 *cpp = NULL;
 539                                 first = 0;
 540                         }
 541                 }
 542                 /* copy label to buffer */
 543                 if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
 544                         /* Should not happen. */
 545                         goto cleanup;
 546                 }
 547                 n = labellen(srcp);
 548                 if (dstp + 1 + n >= eob) {
 549                         goto cleanup;
 550                 }
 551                 memcpy(dstp, srcp, n + 1);
 552                 srcp += n + 1;
 553                 dstp += n + 1;
 554         } while (n != 0);
 555
 556         if (dstp > eob) {
 557 cleanup:
 558                 if (msg != NULL)
 559                         *lpp = NULL;
 560                 errno = EMSGSIZE;
 561                 return (-1);
 562         }
 563         return (dstp - dst);
 564 }
 565
 566 /*
 567  * ns_name_uncompress(msg, eom, src, dst, dstsiz)
 568  *      Expand compressed domain name to presentation format.
 569  * return:
 570  *      Number of bytes read out of `src', or -1 (with errno set).
 571  * note:
 572  *      Root domain returns as "." not "".
 573  */
 574 int
 575 ns_name_uncompress(const u_char *msg, const u_char *eom, const u_char *src,
 576                    char *dst, size_t dstsiz)
 577 {
 578         u_char tmp[NS_MAXCDNAME];
 579         int n;
 580
 581         if ((n = ns_name_unpack(msg, eom, src, tmp, sizeof tmp)) == -1)
 582                 return (-1);
 583         if (ns_name_ntop(tmp, dst, dstsiz) == -1)
 584                 return (-1);
 585         return (n);
 586 }
 587
 588 /*
 589  * ns_name_compress(src, dst, dstsiz, dnptrs, lastdnptr)
 590  *      Compress a domain name into wire format, using compression pointers.
 591  * return:
 592  *      Number of bytes consumed in `dst' or -1 (with errno set).
 593  * notes:
 594  *      'dnptrs' is an array of pointers to previous compressed names.
 595  *      dnptrs[0] is a pointer to the beginning of the message.
 596  *      The list ends with NULL.  'lastdnptr' is a pointer to the end of the
 597  *      array pointed to by 'dnptrs'. Side effect is to update the list of
 598  *      pointers for labels inserted into the message as we compress the name.
 599  *      If 'dnptr' is NULL, we don't try to compress names. If 'lastdnptr'
 600  *      is NULL, we don't update the list.
 601  */
 602 int
 603 ns_name_compress(const char *src, u_char *dst, size_t dstsiz,
 604                  const u_char **dnptrs, const u_char **lastdnptr)
 605 {
 606         u_char tmp[NS_MAXCDNAME];
 607
 608         if (ns_name_pton(src, tmp, sizeof tmp) == -1)
 609                 return (-1);
 610         return (ns_name_pack(tmp, dst, dstsiz, dnptrs, lastdnptr));
 611 }
 612
 613 /*
 614  * Reset dnptrs so that there are no active references to pointers at or
 615  * after src.
 616  */
 617 void
 618 ns_name_rollback(const u_char *src, const u_char **dnptrs,
 619                  const u_char **lastdnptr)
 620 {
 621         while (dnptrs < lastdnptr && *dnptrs != NULL) {
 622                 if (*dnptrs >= src) {
 623                         *dnptrs = NULL;
 624                         break;
 625                 }
 626                 dnptrs++;
 627         }
 628 }
 629
 630 /*
 631  * ns_name_skip(ptrptr, eom)
 632  *      Advance *ptrptr to skip over the compressed name it points at.
 633  * return:
 634  *      0 on success, -1 (with errno set) on failure.
 635  */
 636 int
 637 ns_name_skip(const u_char **ptrptr, const u_char *eom)
 638 {
 639         const u_char *cp;
 640         u_int n;
 641         int l;
 642
 643         cp = *ptrptr;
 644         while (cp < eom && (n = *cp++) != 0) {
 645                 /* Check for indirection. */
 646                 switch (n & NS_CMPRSFLGS) {
 647                 case 0:                 /* normal case, n == len */
 648                         cp += n;
 649                         continue;
 650                 case NS_TYPE_ELT: /* EDNS0 extended label */
 651                         if ((l = labellen(cp - 1)) < 0) {
 652                                 errno = EMSGSIZE; /* XXX */
 653                                 return(-1);
 654                         }
 655                         cp += l;
 656                         continue;
 657                 case NS_CMPRSFLGS:      /* indirection */
 658                         cp++;
 659                         break;
 660                 default:                /* illegal type */
 661                         errno = EMSGSIZE;
 662                         return (-1);
 663                 }
 664                 break;
 665         }
 666         if (cp > eom) {
 667                 errno = EMSGSIZE;
 668                 return (-1);
 669         }
 670         *ptrptr = cp;
 671         return (0);
 672 }
 673
 674 /* Private. */
 675
 676 /*
 677  * special(ch)
 678  *      Thinking in noninternationalized USASCII (per the DNS spec),
 679  *      is this characted special ("in need of quoting") ?
 680  * return:
 681  *      boolean.
 682  */
 683 static int
 684 special(int ch) {
 685         switch (ch) {
 686         case 0x22: /* '"' */
 687         case 0x2E: /* '.' */
 688         case 0x3B: /* ';' */
 689         case 0x5C: /* '\\' */
 690         case 0x28: /* '(' */
 691         case 0x29: /* ')' */
 692         /* Special modifiers in zone files. */
 693         case 0x40: /* '@' */
 694         case 0x24: /* '$' */
 695                 return (1);
 696         default:
 697                 return (0);
 698         }
 699 }
 700
 701 /*
 702  * printable(ch)
 703  *      Thinking in noninternationalized USASCII (per the DNS spec),
 704  *      is this character visible and not a space when printed ?
 705  * return:
 706  *      boolean.
 707  */
 708 static int
 709 printable(int ch) {
 710         return (ch > 0x20 && ch < 0x7f);
 711 }
 712
 713 /*
 714  *      Thinking in noninternationalized USASCII (per the DNS spec),
 715  *      convert this character to lower case if it's upper case.
 716  */
 717 static int
 718 mklower(int ch) {
 719         if (ch >= 0x41 && ch <= 0x5A)
 720                 return (ch + 0x20);
 721         return (ch);
 722 }
 723
 724 /*
 725  * dn_find(domain, msg, dnptrs, lastdnptr)
 726  *      Search for the counted-label name in an array of compressed names.
 727  * return:
 728  *      offset from msg if found, or -1.
 729  * notes:
 730  *      dnptrs is the pointer to the first name on the list,
 731  *      not the pointer to the start of the message.
 732  */
 733 static int
 734 dn_find(const u_char *domain, const u_char *msg,
 735         const u_char * const *dnptrs,
 736         const u_char * const *lastdnptr)
 737 {
 738         const u_char *dn, *cp, *sp;
 739         const u_char * const *cpp;
 740         u_int n;
 741
 742         for (cpp = dnptrs; cpp < lastdnptr; cpp++) {
 743                 sp = *cpp;
 744                 /*
 745                  * terminate search on:
 746                  * root label
 747                  * compression pointer
 748                  * unusable offset
 749                  */
 750                 while (*sp != 0 && (*sp & NS_CMPRSFLGS) == 0 &&
 751                        (sp - msg) < 0x4000) {
 752                         dn = domain;
 753                         cp = sp;
 754                         while ((n = *cp++) != 0) {
 755                                 /*
 756                                  * check for indirection
 757                                  */
 758                                 switch (n & NS_CMPRSFLGS) {
 759                                 case 0:         /* normal case, n == len */
 760                                         n = labellen(cp - 1); /* XXX */
 761
 762                                         if (n != *dn++)
 763                                                 goto next;
 764
 765                                         for ((void)NULL; n > 0; n--)
 766                                                 if (mklower(*dn++) !=
 767                                                     mklower(*cp++))
 768                                                         goto next;
 769                                         /* Is next root for both ? */
 770                                         if (*dn == '\0' && *cp == '\0')
 771                                                 return (sp - msg);
 772                                         if (*dn)
 773                                                 continue;
 774                                         goto next;
 775                                 case NS_CMPRSFLGS:      /* indirection */
 776                                         cp = msg + (((n & 0x3f) << 8) | *cp);
 777                                         break;
 778
 779                                 default:        /* illegal type */
 780                                         errno = EMSGSIZE;
 781                                         return (-1);
 782                                 }
 783                         }
 784  next: ;
 785                         sp += *sp + 1;
 786                 }
 787         }
 788         errno = ENOENT;
 789         return (-1);
 790 }
 791
 792 static int
 793 decode_bitstring(const char **cpp, char *dn, const char *eom)
 794 {
 795         const char *cp = *cpp;
 796         char *beg = dn, tc;
 797         int b, blen, plen;
 798
 799         if ((blen = (*cp & 0xff)) == 0)
 800                 blen = 256;
 801         plen = (blen + 3) / 4;
 802         plen += sizeof("\\[x/]") + (blen > 99 ? 3 : (blen > 9) ? 2 : 1);
 803         if (dn + plen >= eom)
 804                 return(-1);
 805
 806         cp++;
 807         dn += SPRINTF((dn, "\\[x"));
 808         for (b = blen; b > 7; b -= 8, cp++)
 809                 dn += SPRINTF((dn, "%02x", *cp & 0xff));
 810         if (b > 4) {
 811                 tc = *cp++;
 812                 dn += SPRINTF((dn, "%02x", tc & (0xff << (8 - b))));
 813         } else if (b > 0) {
 814                 tc = *cp++;
 815                 dn += SPRINTF((dn, "%1x",
 816                                ((tc >> 4) & 0x0f) & (0x0f << (4 - b))));
 817         }
 818         dn += SPRINTF((dn, "/%d]", blen));
 819
 820         *cpp = cp;
 821         return(dn - beg);
 822 }
 823
 824 static int
 825 encode_bitsring(const char **bp, const char *end, char **labelp,
 826                 char ** dst, const char *eom)
 827 {
 828         int afterslash = 0;
 829         const char *cp = *bp;
 830         char *tp, c;
 831         const char *beg_blen;
 832         char *end_blen = NULL;
 833         int value = 0, count = 0, tbcount = 0, blen = 0;
 834
 835         beg_blen = end_blen = NULL;
 836
 837         /* a bitstring must contain at least 2 characters */
 838         if (end - cp < 2)
 839                 return(EINVAL);
 840
 841         /* XXX: currently, only hex strings are supported */
 842         if (*cp++ != 'x')
 843                 return(EINVAL);
 844         if (!isxdigit((*cp) & 0xff)) /* reject '\[x/BLEN]' */
 845                 return(EINVAL);
 846
 847         for (tp = *dst + 1; cp < end && tp < eom; cp++) {
 848                 switch((c = *cp)) {
 849                 case ']':       /* end of the bitstring */
 850                         if (afterslash) {
 851                                 if (beg_blen == NULL)
 852                                         return(EINVAL);
 853                                 blen = (int)strtol(beg_blen, &end_blen, 10);
 854                                 if (*end_blen != ']')
 855                                         return(EINVAL);
 856                         }
 857                         if (count)
 858                                 *tp++ = ((value << 4) & 0xff);
 859                         cp++;   /* skip ']' */
 860                         goto done;
 861                 case '/':
 862                         afterslash = 1;
 863                         break;
 864                 default:
 865                         if (afterslash) {
 866                                 if (!isdigit(c&0xff))
 867                                         return(EINVAL);
 868                                 if (beg_blen == NULL) {
 869
 870                                         if (c == '0') {
 871                                                 /* blen never begings with 0 */
 872                                                 return(EINVAL);
 873                                         }
 874                                         beg_blen = cp;
 875                                 }
 876                         } else {
 877                                 if (!isxdigit(c&0xff))
 878                                         return(EINVAL);
 879                                 value <<= 4;
 880                                 value += digitvalue[(int)c];
 881                                 count += 4;
 882                                 tbcount += 4;
 883                                 if (tbcount > 256)
 884                                         return(EINVAL);
 885                                 if (count == 8) {
 886                                         *tp++ = value;
 887                                         count = 0;
 888                                 }
 889                         }
 890                         break;
 891                 }
 892         }
 893   done:
 894         if (cp >= end || tp >= eom)
 895                 return(EMSGSIZE);
 896
 897         /*
 898          * bit length validation:
 899          * If a <length> is present, the number of digits in the <bit-data>
 900          * MUST be just sufficient to contain the number of bits specified
 901          * by the <length>. If there are insignificant bits in a final
 902          * hexadecimal or octal digit, they MUST be zero.
 903          * RFC 2673, Section 3.2.
 904          */
 905         if (blen > 0) {
 906                 int traillen;
 907
 908                 if (((blen + 3) & ~3) != tbcount)
 909                         return(EINVAL);
 910                 traillen = tbcount - blen; /* between 0 and 3 */
 911                 if (((value << (8 - traillen)) & 0xff) != 0)
 912                         return(EINVAL);
 913         }
 914         else
 915                 blen = tbcount;
 916         if (blen == 256)
 917                 blen = 0;
 918
 919         /* encode the type and the significant bit fields */
 920         **labelp = DNS_LABELTYPE_BITSTRING;
 921         **dst = blen;
 922
 923         *bp = cp;
 924         *dst = tp;
 925
 926         return(0);
 927 }
 928
 929 static int
 930 labellen(const u_char *lp)
 931 {
 932         int bitlen;
 933         u_char l = *lp;
 934
 935         if ((l & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
 936                 /* should be avoided by the caller */
 937                 return(-1);
 938         }
 939
 940         if ((l & NS_CMPRSFLGS) == NS_TYPE_ELT) {
 941                 if (l == DNS_LABELTYPE_BITSTRING) {
 942                         if ((bitlen = *(lp + 1)) == 0)
 943                                 bitlen = 256;
 944                         return((bitlen + 7 ) / 8 + 1);
 945                 }
 946                 return(-1);     /* unknwon ELT */
 947         }
 948         return(l);
 949 }