resolv/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 lint
  19 static const char rcsid[] = "$Id$";
  20 #endif
  21
  22 #include <sys/types.h>
  23
  24 #include <netinet/in.h>
  25 #include <arpa/nameser.h>
  26
  27 #include <errno.h>
  28 #include <resolv.h>
  29 #include <string.h>
  30 #include <ctype.h>
  31
  32 /* Data. */
  33
  34 static const char       digits[] = "0123456789";
  35
  36 /* Forward. */
  37
  38 static int              special(int);
  39 static int              printable(int);
  40 static int              dn_find(const u_char *, const u_char *,
  41                                 const u_char * const *,
  42                                 const u_char * const *);
  43
  44 /* Public. */
  45
  46 /*
  47  * ns_name_ntop(src, dst, dstsiz)
  48  *      Convert an encoded domain name to printable ascii as per RFC1035.
  49  * return:
  50  *      Number of bytes written to buffer, or -1 (with errno set)
  51  * notes:
  52  *      The root is returned as "."
  53  *      All other domains are returned in non absolute form
  54  */
  55 int
  56 ns_name_ntop(const u_char *src, char *dst, size_t dstsiz) {
  57         const u_char *cp;
  58         char *dn, *eom;
  59         u_char c;
  60         u_int n;
  61
  62         cp = src;
  63         dn = dst;
  64         eom = dst + dstsiz;
  65
  66         while ((n = *cp++) != 0) {
  67                 if ((n & NS_CMPRSFLGS) != 0) {
  68                         /* Some kind of compression pointer. */
  69                         __set_errno (EMSGSIZE);
  70                         return (-1);
  71                 }
  72                 if (dn != dst) {
  73                         if (dn >= eom) {
  74                                 __set_errno (EMSGSIZE);
  75                                 return (-1);
  76                         }
  77                         *dn++ = '.';
  78                 }
  79                 if (dn + n >= eom) {
  80                         __set_errno (EMSGSIZE);
  81                         return (-1);
  82                 }
  83                 for ((void)NULL; n > 0; n--) {
  84                         c = *cp++;
  85                         if (special(c)) {
  86                                 if (dn + 1 >= eom) {
  87                                         __set_errno (EMSGSIZE);
  88                                         return (-1);
  89                                 }
  90                                 *dn++ = '\\';
  91                                 *dn++ = (char)c;
  92                         } else if (!printable(c)) {
  93                                 if (dn + 3 >= eom) {
  94                                         __set_errno (EMSGSIZE);
  95                                         return (-1);
  96                                 }
  97                                 *dn++ = '\\';
  98                                 *dn++ = digits[c / 100];
  99                                 *dn++ = digits[(c % 100) / 10];
 100                                 *dn++ = digits[c % 10];
 101                         } else {
 102                                 if (dn >= eom) {
 103                                         __set_errno (EMSGSIZE);
 104                                         return (-1);
 105                                 }
 106                                 *dn++ = (char)c;
 107                         }
 108                 }
 109         }
 110         if (dn == dst) {
 111                 if (dn >= eom) {
 112                         __set_errno (EMSGSIZE);
 113                         return (-1);
 114                 }
 115                 *dn++ = '.';
 116         }
 117         if (dn >= eom) {
 118                 __set_errno (EMSGSIZE);
 119                 return (-1);
 120         }
 121         *dn++ = '\0';
 122         return (dn - dst);
 123 }
 124
 125 /*
 126  * ns_name_pton(src, dst, dstsiz)
 127  *      Convert a ascii string into an encoded domain name as per RFC1035.
 128  * return:
 129  *      -1 if it fails
 130  *      1 if string was fully qualified
 131  *      0 is string was not fully qualified
 132  * notes:
 133  *      Enforces label and domain length limits.
 134  */
 135
 136 int
 137 ns_name_pton(const char *src, u_char *dst, size_t dstsiz) {
 138         u_char *label, *bp, *eom;
 139         int c, n, escaped;
 140         char *cp;
 141
 142         escaped = 0;
 143         bp = dst;
 144         eom = dst + dstsiz;
 145         label = bp++;
 146
 147         while ((c = *src++) != 0) {
 148                 if (escaped) {
 149                         if ((cp = strchr(digits, c)) != NULL) {
 150                                 n = (cp - digits) * 100;
 151                                 if ((c = *src++) == 0 ||
 152                                     (cp = strchr(digits, c)) == NULL) {
 153                                         __set_errno (EMSGSIZE);
 154                                         return (-1);
 155                                 }
 156                                 n += (cp - digits) * 10;
 157                                 if ((c = *src++) == 0 ||
 158                                     (cp = strchr(digits, c)) == NULL) {
 159                                         __set_errno (EMSGSIZE);
 160                                         return (-1);
 161                                 }
 162                                 n += (cp - digits);
 163                                 if (n > 255) {
 164                                         __set_errno (EMSGSIZE);
 165                                         return (-1);
 166                                 }
 167                                 c = n;
 168                         }
 169                         escaped = 0;
 170                 } else if (c == '\\') {
 171                         escaped = 1;
 172                         continue;
 173                 } else if (c == '.') {
 174                         c = (bp - label - 1);
 175                         if ((c & NS_CMPRSFLGS) != 0) {  /* Label too big. */
 176                                 __set_errno (EMSGSIZE);
 177                                 return (-1);
 178                         }
 179                         if (label >= eom) {
 180                                 __set_errno (EMSGSIZE);
 181                                 return (-1);
 182                         }
 183                         *label = c;
 184                         /* Fully qualified ? */
 185                         if (*src == '\0') {
 186                                 if (c != 0) {
 187                                         if (bp >= eom) {
 188                                                 __set_errno (EMSGSIZE);
 189                                                 return (-1);
 190                                         }
 191                                         *bp++ = '\0';
 192                                 }
 193                                 if ((bp - dst) > MAXCDNAME) {
 194                                         __set_errno (EMSGSIZE);
 195                                         return (-1);
 196                                 }
 197                                 return (1);
 198                         }
 199                         if (c == 0 || *src == '.') {
 200                                 __set_errno (EMSGSIZE);
 201                                 return (-1);
 202                         }
 203                         label = bp++;
 204                         continue;
 205                 }
 206                 if (bp >= eom) {
 207                         __set_errno (EMSGSIZE);
 208                         return (-1);
 209                 }
 210                 *bp++ = (u_char)c;
 211         }
 212         c = (bp - label - 1);
 213         if ((c & NS_CMPRSFLGS) != 0) {          /* Label too big. */
 214                 __set_errno (EMSGSIZE);
 215                 return (-1);
 216         }
 217         if (label >= eom) {
 218                 __set_errno (EMSGSIZE);
 219                 return (-1);
 220         }
 221         *label = c;
 222         if (c != 0) {
 223                 if (bp >= eom) {
 224                         __set_errno (EMSGSIZE);
 225                         return (-1);
 226                 }
 227                 *bp++ = 0;
 228         }
 229         if ((bp - dst) > MAXCDNAME) {   /* src too big */
 230                 __set_errno (EMSGSIZE);
 231                 return (-1);
 232         }
 233         return (0);
 234 }
 235
 236 /*
 237  * ns_name_ntol(src, dst, dstsiz)
 238  *      Convert a network strings labels into all lowercase.
 239  * return:
 240  *      Number of bytes written to buffer, or -1 (with errno set)
 241  * notes:
 242  *      Enforces label and domain length limits.
 243  */
 244
 245 int
 246 ns_name_ntol(const u_char *src, u_char *dst, size_t dstsiz) {
 247         const u_char *cp;
 248         u_char *dn, *eom;
 249         u_char c;
 250         u_int n;
 251
 252         cp = src;
 253         dn = dst;
 254         eom = dst + dstsiz;
 255
 256         while ((n = *cp++) != 0) {
 257                 if ((n & NS_CMPRSFLGS) != 0) {
 258                         /* Some kind of compression pointer. */
 259                         __set_errno (EMSGSIZE);
 260                         return (-1);
 261                 }
 262                 *dn++ = n;
 263                 if (dn + n >= eom) {
 264                         __set_errno (EMSGSIZE);
 265                         return (-1);
 266                 }
 267                 for ((void)NULL; n > 0; n--) {
 268                         c = *cp++;
 269                         if (isupper(c))
 270                                 *dn++ = tolower(c);
 271                         else
 272                                 *dn++ = c;
 273                 }
 274         }
 275         *dn++ = '\0';
 276         return (dn - dst);
 277 }
 278
 279 /*
 280  * ns_name_unpack(msg, eom, src, dst, dstsiz)
 281  *      Unpack a domain name from a message, source may be compressed.
 282  * return:
 283  *      -1 if it fails, or consumed octets if it succeeds.
 284  */
 285 int
 286 ns_name_unpack(const u_char *msg, const u_char *eom, const u_char *src,
 287                u_char *dst, size_t dstsiz)
 288 {
 289         const u_char *srcp, *dstlim;
 290         u_char *dstp;
 291         int n, len, checked;
 292
 293         len = -1;
 294         checked = 0;
 295         dstp = dst;
 296         srcp = src;
 297         dstlim = dst + dstsiz;
 298         if (srcp < msg || srcp >= eom) {
 299                 __set_errno (EMSGSIZE);
 300                 return (-1);
 301         }
 302         /* Fetch next label in domain name. */
 303         while ((n = *srcp++) != 0) {
 304                 /* Check for indirection. */
 305                 switch (n & NS_CMPRSFLGS) {
 306                 case 0:
 307                         /* Limit checks. */
 308                         if (dstp + n + 1 >= dstlim || srcp + n >= eom) {
 309                                 __set_errno (EMSGSIZE);
 310                                 return (-1);
 311                         }
 312                         checked += n + 1;
 313                         *dstp++ = n;
 314                         memcpy(dstp, srcp, n);
 315                         dstp += n;
 316                         srcp += n;
 317                         break;
 318
 319                 case NS_CMPRSFLGS:
 320                         if (srcp >= eom) {
 321                                 __set_errno (EMSGSIZE);
 322                                 return (-1);
 323                         }
 324                         if (len < 0)
 325                                 len = srcp - src + 1;
 326                         srcp = msg + (((n & 0x3f) << 8) | (*srcp & 0xff));
 327                         if (srcp < msg || srcp >= eom) {  /* Out of range. */
 328                                 __set_errno (EMSGSIZE);
 329                                 return (-1);
 330                         }
 331                         checked += 2;
 332                         /*
 333                          * Check for loops in the compressed name;
 334                          * if we've looked at the whole message,
 335                          * there must be a loop.
 336                          */
 337                         if (checked >= eom - msg) {
 338                                 __set_errno (EMSGSIZE);
 339                                 return (-1);
 340                         }
 341                         break;
 342
 343                 default:
 344                         __set_errno (EMSGSIZE);
 345                         return (-1);                    /* flag error */
 346                 }
 347         }
 348         *dstp = '\0';
 349         if (len < 0)
 350                 len = srcp - src;
 351         return (len);
 352 }
 353
 354 /*
 355  * ns_name_pack(src, dst, dstsiz, dnptrs, lastdnptr)
 356  *      Pack domain name 'domain' into 'comp_dn'.
 357  * return:
 358  *      Size of the compressed name, or -1.
 359  * notes:
 360  *      'dnptrs' is an array of pointers to previous compressed names.
 361  *      dnptrs[0] is a pointer to the beginning of the message. The array
 362  *      ends with NULL.
 363  *      'lastdnptr' is a pointer to the end of the array pointed to
 364  *      by 'dnptrs'.
 365  * Side effects:
 366  *      The list of pointers in dnptrs is updated for labels inserted into
 367  *      the message as we compress the name.  If 'dnptr' is NULL, we don't
 368  *      try to compress names. If 'lastdnptr' is NULL, we don't update the
 369  *      list.
 370  */
 371 int
 372 ns_name_pack(const u_char *src, u_char *dst, int dstsiz,
 373              const u_char **dnptrs, const u_char **lastdnptr)
 374 {
 375         u_char *dstp;
 376         const u_char **cpp, **lpp, *eob, *msg;
 377         const u_char *srcp;
 378         int n, l;
 379
 380         srcp = src;
 381         dstp = dst;
 382         eob = dstp + dstsiz;
 383         lpp = cpp = NULL;
 384         if (dnptrs != NULL) {
 385                 if ((msg = *dnptrs++) != NULL) {
 386                         for (cpp = dnptrs; *cpp != NULL; cpp++)
 387                                 (void)NULL;
 388                         lpp = cpp;      /* end of list to search */
 389                 }
 390         } else
 391                 msg = NULL;
 392
 393         /* make sure the domain we are about to add is legal */
 394         l = 0;
 395         do {
 396                 n = *srcp;
 397                 if ((n & NS_CMPRSFLGS) != 0) {
 398                         __set_errno (EMSGSIZE);
 399                         return (-1);
 400                 }
 401                 l += n + 1;
 402                 if (l > MAXCDNAME) {
 403                         __set_errno (EMSGSIZE);
 404                         return (-1);
 405                 }
 406                 srcp += n + 1;
 407         } while (n != 0);
 408
 409         /* from here on we need to reset compression pointer array on error */
 410         srcp = src;
 411         do {
 412                 /* Look to see if we can use pointers. */
 413                 n = *srcp;
 414                 if (n != 0 && msg != NULL) {
 415                         l = dn_find(srcp, msg, (const u_char * const *)dnptrs,
 416                                     (const u_char * const *)lpp);
 417                         if (l >= 0) {
 418                                 if (dstp + 1 >= eob) {
 419                                         goto cleanup;
 420                                 }
 421                                 *dstp++ = (l >> 8) | NS_CMPRSFLGS;
 422                                 *dstp++ = l % 256;
 423                                 return (dstp - dst);
 424                         }
 425                         /* Not found, save it. */
 426                         if (lastdnptr != NULL && cpp < lastdnptr - 1 &&
 427                             (dstp - msg) < 0x4000) {
 428                                 *cpp++ = dstp;
 429                                 *cpp = NULL;
 430                         }
 431                 }
 432                 /* copy label to buffer */
 433                 if (n & NS_CMPRSFLGS) {         /* Should not happen. */
 434                         goto cleanup;
 435                 }
 436                 if (dstp + 1 + n >= eob) {
 437                         goto cleanup;
 438                 }
 439                 memcpy(dstp, srcp, n + 1);
 440                 srcp += n + 1;
 441                 dstp += n + 1;
 442         } while (n != 0);
 443
 444         if (dstp > eob) {
 445 cleanup:
 446                 if (msg != NULL)
 447                         *lpp = NULL;
 448                 __set_errno (EMSGSIZE);
 449                 return (-1);
 450         }
 451         return (dstp - dst);
 452 }
 453
 454 /*
 455  * ns_name_uncompress(msg, eom, src, dst, dstsiz)
 456  *      Expand compressed domain name to presentation format.
 457  * return:
 458  *      Number of bytes read out of `src', or -1 (with errno set).
 459  * note:
 460  *      Root domain returns as "." not "".
 461  */
 462 int
 463 ns_name_uncompress(const u_char *msg, const u_char *eom, const u_char *src,
 464                    char *dst, size_t dstsiz)
 465 {
 466         u_char tmp[NS_MAXCDNAME];
 467         int n;
 468
 469         if ((n = ns_name_unpack(msg, eom, src, tmp, sizeof tmp)) == -1)
 470                 return (-1);
 471         if (ns_name_ntop(tmp, dst, dstsiz) == -1)
 472                 return (-1);
 473         return (n);
 474 }
 475
 476 /*
 477  * ns_name_compress(src, dst, dstsiz, dnptrs, lastdnptr)
 478  *      Compress a domain name into wire format, using compression pointers.
 479  * return:
 480  *      Number of bytes consumed in `dst' or -1 (with errno set).
 481  * notes:
 482  *      'dnptrs' is an array of pointers to previous compressed names.
 483  *      dnptrs[0] is a pointer to the beginning of the message.
 484  *      The list ends with NULL.  'lastdnptr' is a pointer to the end of the
 485  *      array pointed to by 'dnptrs'. Side effect is to update the list of
 486  *      pointers for labels inserted into the message as we compress the name.
 487  *      If 'dnptr' is NULL, we don't try to compress names. If 'lastdnptr'
 488  *      is NULL, we don't update the list.
 489  */
 490 int
 491 ns_name_compress(const char *src, u_char *dst, size_t dstsiz,
 492                  const u_char **dnptrs, const u_char **lastdnptr)
 493 {
 494         u_char tmp[NS_MAXCDNAME];
 495
 496         if (ns_name_pton(src, tmp, sizeof tmp) == -1)
 497                 return (-1);
 498         return (ns_name_pack(tmp, dst, dstsiz, dnptrs, lastdnptr));
 499 }
 500
 501 /*
 502  * ns_name_skip(ptrptr, eom)
 503  *      Advance *ptrptr to skip over the compressed name it points at.
 504  * return:
 505  *      0 on success, -1 (with errno set) on failure.
 506  */
 507 int
 508 ns_name_skip(const u_char **ptrptr, const u_char *eom) {
 509         const u_char *cp;
 510         u_int n;
 511
 512         cp = *ptrptr;
 513         while (cp < eom && (n = *cp++) != 0) {
 514                 /* Check for indirection. */
 515                 switch (n & NS_CMPRSFLGS) {
 516                 case 0:                 /* normal case, n == len */
 517                         cp += n;
 518                         continue;
 519                 case NS_CMPRSFLGS:      /* indirection */
 520                         cp++;
 521                         break;
 522                 default:                /* illegal type */
 523                         __set_errno (EMSGSIZE);
 524                         return (-1);
 525                 }
 526                 break;
 527         }
 528         if (cp > eom) {
 529                 __set_errno (EMSGSIZE);
 530                 return (-1);
 531         }
 532         *ptrptr = cp;
 533         return (0);
 534 }
 535
 536 /* Private. */
 537
 538 /*
 539  * special(ch)
 540  *      Thinking in noninternationalized USASCII (per the DNS spec),
 541  *      is this characted special ("in need of quoting") ?
 542  * return:
 543  *      boolean.
 544  */
 545 static int
 546 special(int ch) {
 547         switch (ch) {
 548         case 0x22: /* '"' */
 549         case 0x2E: /* '.' */
 550         case 0x3B: /* ';' */
 551         case 0x5C: /* '\\' */
 552         /* Special modifiers in zone files. */
 553         case 0x40: /* '@' */
 554         case 0x24: /* '$' */
 555                 return (1);
 556         default:
 557                 return (0);
 558         }
 559 }
 560
 561 /*
 562  * printable(ch)
 563  *      Thinking in noninternationalized USASCII (per the DNS spec),
 564  *      is this character visible and not a space when printed ?
 565  * return:
 566  *      boolean.
 567  */
 568 static int
 569 printable(int ch) {
 570         return (ch > 0x20 && ch < 0x7f);
 571 }
 572
 573 /*
 574  *      Thinking in noninternationalized USASCII (per the DNS spec),
 575  *      convert this character to lower case if it's upper case.
 576  */
 577 static int
 578 mklower(int ch) {
 579         if (ch >= 0x41 && ch <= 0x5A)
 580                 return (ch + 0x20);
 581         return (ch);
 582 }
 583
 584 /*
 585  * dn_find(domain, msg, dnptrs, lastdnptr)
 586  *      Search for the counted-label name in an array of compressed names.
 587  * return:
 588  *      offset from msg if found, or -1.
 589  * notes:
 590  *      dnptrs is the pointer to the first name on the list,
 591  *      not the pointer to the start of the message.
 592  */
 593 static int
 594 dn_find(const u_char *domain, const u_char *msg,
 595         const u_char * const *dnptrs,
 596         const u_char * const *lastdnptr)
 597 {
 598         const u_char *dn, *cp, *sp;
 599         const u_char * const *cpp;
 600         u_int n;
 601
 602         for (cpp = dnptrs; cpp < lastdnptr; cpp++) {
 603                 dn = domain;
 604                 sp = cp = *cpp;
 605                 while ((n = *cp++) != 0) {
 606                         /*
 607                          * check for indirection
 608                          */
 609                         switch (n & NS_CMPRSFLGS) {
 610                         case 0:                 /* normal case, n == len */
 611                                 if (n != *dn++)
 612                                         goto next;
 613                                 for ((void)NULL; n > 0; n--)
 614                                         if (mklower(*dn++) != mklower(*cp++))
 615                                                 goto next;
 616                                 /* Is next root for both ? */
 617                                 if (*dn == '\0' && *cp == '\0')
 618                                         return (sp - msg);
 619                                 if (*dn)
 620                                         continue;
 621                                 goto next;
 622
 623                         case NS_CMPRSFLGS:      /* indirection */
 624                                 cp = msg + (((n & 0x3f) << 8) | *cp);
 625                                 break;
 626
 627                         default:        /* illegal type */
 628                                 __set_errno (EMSGSIZE);
 629                                 return (-1);
 630                         }
 631                 }
 632  next: ;
 633         }
 634         __set_errno (ENOENT);
 635         return (-1);
 636 }